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The internal flow instability and high pulsation characteristics in the Roots-type hydrogen circulation pump (RHCP) are the main causes of its aerodynamic noise. This study proposes two mathematical models of new deflectors combined in the static domain to improve flow stability and reduce gas pulsations. Meanwhile, this study also compares the simulation results of different cases with a combination of different deflectors and then chooses the best performance case to research with the original model. Results found that placing the V-shaped deflector at the inlet of the rotor domain effectively reduces pressure pulsations in the RHCP at low rotary speeds. The pressure pulsation index at the inlet of the rotor domain decreased by about 26% compared to the original modal, and the outlet pressure pulsation index decreased by about 10%. Additionally, at low rotary speed, the V-shaped deflector significantly reduces the impact of radial clearance leakage flow on the flow characteristics inside the suction chamber, which improves the gas flow characteristics in the suction chamber. These research findings provide new ideas and methods for designing and manufacturing RHCPs. • Analysis of Roots pumps combining both internal flow characteristics and pulsation characteristics. • Two novel deflector structures are proposed for the rectification objective. • The application of deflectors does not affect the volumetric efficiency of pumps. • The deflector reduces inlet pulsation characteristics at low rotation speed. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative two-stage ejector with a needle blocking the main nozzle area within 0%-60% to control the mass flow rate of the inlet. Based on this, under certain liquid volume fraction in two-phase inlet fluids, the nozzle exit positions (NXP 1 and NXP 2) and constant-area mixing chamber lengths (L 1 and L 2) of the first and second stages were optimized with blocking area ratio (BAR) of primary nozzle throat by using CFD simulation, the working fluid is R134a. The main results are as follows: (1) The maximum increase rate of the entrainment ratio (ER) of the first and the second-stage with optimization of four geometries without needle blockage are relatively slight, in comparison, both of them with optimization of L 1 can reach 23.47% and 20.38%, which obtain the best improvement; (2) Under the condition of a needle blockage at the primary flow inlet of the first-stage ejector, the increase rate of ER 1 with optimization of NXP 1 and L 1 are close to that without needle blockage; (3) Under the condition of a needle blockage at the primary flow inlet of the second-stage ejector, the first-stage ejector can achieve relatively large improvement of ER, especially, the optimization of NXP 2 can increase the maximum ER 1 by 258.73% of initial value, and the optimization of L 2 can increase the maximum ER 1 by 239.38% of initial value. The study in this work is helpful to understand the two-stage ejector performance improvement by adjusting the blocking area ratio of primary nozzle throat under certain liquid volume fraction in two-phase inlet fluids. [ABSTRACT FROM AUTHOR]

This study investigates the impact of upstream energy deposition as an active flow control method on the performance of a two-dimensional scramjet inlet through numerical simulations. An in-house inviscid finite volume solver was employed for the simulations, with boundary reconstruction of the scramjet achieved using a ghost-cell based immersed boundary method. The effects of different energy spot locations, various energy strengths, and different freestream Mach numbers on the scramjet performance were thoroughly analyzed. Four inlet parameters, namely, mass capture ratio (μ), total pressure ratio (TPR), kinetic energy efficiency (η K E), and flow distortion index (DI), were used to assess the scramjet performance. The analysis revealed that energy deposition significantly reduced flow distortion, resulting in noticeable improvements in mass flux and total pressure ratio. However, kinetic energy efficiency exhibited minimal change. The study provides comprehensive insights into the impact of energy deposition on scramjet performance, highlighting its potential for enhancing inlet characteristics. • Effects of upstream energy deposition on scramjet inlet performance are numerically investigated. • Scramjet performance is assessed using four aerothermodynamic parameters. • Upstream energy deposition significantly reduces flow distortion and improves mass flux. • The location and strength of the deposited energy strongly influence the performance parameters. [ABSTRACT FROM AUTHOR]

We study the capability of Large Eddy Simulation (LES) to predict fluid residence time in a ventilated room. Validation is performed against an experiment where the inlet vent slot width matches that of the room. On a coarse grid, the Smagorinsky subgrid-scale model has a detrimental effect on flow statistics, whilst the WALE and Germano–Lilly models perform well. A refined grid produces close agreement with the reference data. A simulation with a narrow inlet slot demonstrates that the flow becomes three-dimensional, with pairs of spiral vortices forming in the room and altering the recirculation pattern when compared to the wide inlet slot configuration. The obtained LES statistics show improvements in the prediction of velocity field over conventional RANS modelling techniques. Fluid age probability density functions show that a wide range of residence time values around the mean value can be observed within the room. LES is capable of providing accurate predictions in a simplified ventilated room, and residence time probability density function distributions can be useful for the improvement of ventilation strategies. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigated the thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen supply system. A performance analysis model was developed by the modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen. In the analysis model, a plate-fin heat exchanger (PFHE) was chosen as the type of a cryogenic vaporizer. The inlet temperature and pressure conditions of liquified hydrogen were 20 K and 10 bar, respectively and the outlet temperature condition of hydrogen was a room temperature. Based on the theoretical results, we presented effects of geometric parameters on the performance of the vaporizer under the fixed pumping power condition. Especially, it is shown that the effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. In addition, we presented the effect of the aspect ratio of microchannels on the effectiveness considering both cases where the microchannel heights of the EGW mixture and hydrogen were either the same or different. Also, we showed the effect of the vaporizer length on the performance of the vaporizer. Finally, geometric parameters that can satisfy the two target performances are suggested. • Thermal performance of a low-pressure cryogenic vaporizer for liquified hydrogen was investigated. • Modified effectiveness-NTU method considering the axial conduction and phase change of liquified hydrogen were used. • Effectiveness of the hot fluid and cold fluid exhibit opposite trends depending on the axial conduction. • Effects of the aspect ratio of microchannels and the length on the effectiveness were presented. [ABSTRACT FROM AUTHOR]

Chip breakers are used in turning to improve chip breakage. In standard cutting inserts, they are pressed into the rake face before sintering. However, for specialized tools like profile grooving tools, this pressing is not possible. Instead, a laser preparation process can be applied after grinding the tool profile to create a diverse range of chip breaker geometries. The aim of this investigation is to gain insights into the relationship between the geometric parameters of laser-prepared chip breaker geometries and chip formation. For this reason, experimental turning investigations were conducted with varied chip breaker geometries. Based on these experiments, chip formation was observed for different profile geometries and chip breakers. The findings indicate that the inlet angle, outlet angle, width, depth, and lateral ridges significantly influence chip-breaking behaviour. These results can inform the development of application-specific design for chip breaker geometries. [ABSTRACT FROM AUTHOR]

Dry powder inhalers (DPIs) are widely employed to treat respiratory diseases, offering numerous advantages such as high dose capacity and stable formulations. However, they usually face challenges in achieving sufficient pulmonary drug delivery and minimizing excessive oropharyngeal deposition. This review provides a new viewpoint to address these challenges by focusing on the role of swirling flow, a crucial yet under-researched aspect that induces strong turbulence. In the review, we comprehensively discuss both key classic designs (tangential inlet, swirling chamber, grid mesh, and mouthpiece) and innovative designs in inhalers, exploring how the induced swirling flow initiates powder dispersion and promotes delivery efficiency. Valuable design considerations to effectively coordinate inhalers with formulations and patients are also provided. It is highlighted that the delicate manipulation of swirling flow is essential to maximize benefits. By emphasizing the role of swirling flow and its potential application, this review offers promising insights for advancing DPI technology and optimizing therapeutic outcomes in inhaled therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] As lyophilization continues to be a critical step in the manufacturing of sensitive biopharmaceuticals, challenges often arise during the scale up to commercial scale or the transfer from one manufacturing site to another. While data from the small-scale development of the lyophilization cycle is abundant it is typically much more difficult to extract important information from commercial scale cycles, due to the lack of process analytical technologies available on the commercial line. There is often a reluctance to include wireless temperature or pressure probes during GMP operations due to the additional contamination risk, and retrofitting equipment such as the TDLAS can be prohibitively expensive. Further, as products become more advanced, the cost of consuming the product or even the availability of material may limit the opportunities to run commercial scale trials. This paper presents two novel methods to garner critical cycle information to allow for the evaluation of cycle performance without the need for expensive analytical equipment, costly revalidation and line downtime. Critically, this can be achieved using commonly available temperature and capacitance probes on existing commercial scale equipment. The first method is a calorimetric method, based on quantifying the differences in heat transfer liquid temperature between the shelf inlet and shelf outlet. This change in temperature results from the on-going sublimation, an endo-thermic reaction occurring during lyophilization. The second method uses the differential pressure between the chamber and condenser resulting from the vapor flow from vial to condenser during primary drying. As stated by the authors both methods align well and provide valuable cycle characterization data. [ABSTRACT FROM AUTHOR]

Mixing characteristics play an important role on the operational process of rotating detonation combustor (RDC). In this paper, a series of numerical calculations were conducted to analyze the influence of injection diameter, injection position, reactant mass flow rate, and equivalence ratio on mixing characteristics. Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed in detail. The findings indicated that all four injection conditions had significant influence on mixing characteristics, among which injection position was the most significant factor. When injection position was in convergent section, the mixing characteristics were better than those in ignition section. Reducing the fuel diameter gradually improved mixing characteristics, but also increased total pressure loss. The change of reactant mass flow rate had a minimal effect on mixing characteristics. As equivalence ratio decreased, mixing characteristics decreased and total pressure loss decreased. In addition, the comparative analysis also showed that penetration depth of hydrogen had an impact on flow field disturbance and distribution of return region, which led to the difference in mixing characteristics. When hydrogen was injected into the convergent structure section where air flow velocity did not reach sonic speed and was in acceleration phase, total pressure loss would be effectively reduced in combustor dome. • A new rotating detonation combustor model with convergent inlet structure was built. • Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed using RANS and LES. • Mixing characteristics of RDC were significantly enhanced when the injection position was in convergent structure section. [ABSTRACT FROM AUTHOR]

The advection-diffusion equation is fundamental to modeling various transport phenomena, including the distribution of chemical species in surface or groundwater flow. In cases where the concentration at the source is unknown, inverse problem formulations are required to estimate the desired states by assimilating concentration monitoring data from specific points along the watercourse using a Bayesian approach. This paper proposes a combination of the Eulerian-Lagrangian method and the meshless method of fundamental solutions to solve the advection-diffusion equation. Moreover, the method was used as an evolution model for the sequential importance resampling particle filter algorithm to reconstruct the time-dependent inlet pollutant concentration in inverse problems. Numerical smooth and discontinuous inlet function results show that the particle filter - Eulerian-Lagrangian method of fundamental solutions combination can reconstruct inlet concentration time series. • Verification and validation of ELMFS solution with analytical, FDM and experimental data. • The ELMFS was coupled with sampling importance resampling particle filter for the solution of inverse problem. • The proposed framework is reliable and robust in reconstructing the inlet boundary conditions. [ABSTRACT FROM AUTHOR]

For the roots hydrogen circulating pump (HCP), different rotor profiles result in variations in flow pulsation, pressure pulsation, and pressure-velocity distribution within the pump. In this study, unsteady numerical simulations were conducted on the HCP with variable trochoid ratio profiles to analyze its flow characteristics. The findings indicate that employing a variable trochoid ratio to design the rotor profile enhances the amplitude of the HCP's inlet and outlet flow rates, with a greater impact on the pulsation of the inlet flow rate. In comparison to an ordinary trochoid profile, the variable trochoid ratio profile exhibits reduced vortex in the suction chamber and is less affected by leakage flow between the rotor and casing. Furthermore, due to the lager area utilization rate of the variable trochoid ratio profile, the volume of the HCP's suction chamber increases, facilitating the full development of inlet flow and generating a high kinetic energy vortex, thereby further augmenting the inlet flow. [Display omitted] • Implementation of variable trochoid ratio profile enhances average flow rate. • Inlet flow pulsation varies in variable and ordinary trochoid profiles. • Inward-tapered profile expands suction chamber, generates high-energy vortex. [ABSTRACT FROM AUTHOR]

To improve the performance of hydrocyclones for in-situ natural gas hydrate recovery and desanding, this study analyzed the hydrocyclone's sensitivity factors, optimized the structural parameters, and investigated the adaptability to the reservoir and operating parameters through numerical simulations and experiments. Results showed that the optimal structural parameters were spiral pitch of 24 mm, vortex finder diameter of 36 mm, spigot diameter of 26 mm, number of spirals equals 5, and cone angle of 6°. Under the optimal parameter configuration, the efficiency of the hydrocyclone is exceeded 90%, and the pressure drop was within 0.5 MPa. When the inlet natural gas hydrate volume concentration, or the inlet sand volume concentration are increased, the separation efficiency and pressure drop changed only slightly. The natural gas hydrate hydrocyclone showed good adaptability to the reservoir and operating parameters. These findings provide theoretical guidance for the design and construction of natural gas hydrate in-situ separators. [ABSTRACT FROM AUTHOR]

To effectively reduce the dust pollution in the fully mechanized face, this study proposes a large-scale dust-droplet coupling model based on LES-VOF and the dust-droplet probabilistic collision algorithm. Subsequently, the dispersion of droplets and dust under various spray pressures was analyzed. The accuracy of the model was verified through experiments and measurements, with a relative error of less than 15.0%. The analysis results indicated that the airflow on the air inlet side generated a vortex field, resulting in the accumulation of dust and droplets within 0–9.8 m from the heading face. The airflow on the air outlet side moved backward along the tunnel floor, causing the droplets and dust to disperse in a larger area. As the spray pressure increased, the droplet coverage distance showed a bimodal pattern, while the dust diffusion distance initially increased and then decreased. If the spray pressure exceeded 5 MPa, the covering distance of droplets and dust reached 23.0 m and 4.2 m, respectively, and the dust concentration in the area going beyond 15.0 m was below 20.0 mg/m3. The dust concentration at the driver's location was measured at 5.35 mg/m3, achieving a significant dust reduction rate of 90.60%. More importantly, the on-site application analysis has presented well-aligned data with the simulation results. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the high probability of hydrogen leaking from narrow cracks of the vessels, an experimental study is conducted to investigate the spontaneous ignition of high-pressure hydrogen released into a tube through inlets with different narrowness, including circular, square (length-width ratio χ = 1), and two slit shapes of χ = 2 and 3, with the same area. Pressure transducers and photoelectric sensors are used to detect shock wave dynamic variation and ignition occurrence. The results indicate that narrow inlets weaken the shock wave intensity and speed, and the weakening effect increases with narrowness. Moreover, spontaneous ignition is affected. The minimum burst pressure required for spontaneous ignition is higher in the cases with square and slit inlets. Most significantly, when χ is 3 , it is 2.5 times that of circular inlet. Meanwhile, for narrow inlets, the ignition flame intensity and speed are enhanced, and the inlet of χ = 2 has the greatest impact. • The influence of narrow releasing ports on self-ignition hydrogen is investigated. • Narrow ports weaken the shock wave intensity and speed. • It requires higher burst pressure for self-ignition under narrow ports. • The flame intensity is enhanced under narrow ports. • Different narrowness of the ports brings different effects. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the inlet is prone to unstart during the flight of air-breathing hypersonic vehicles (AHV), an adaptive backstepping control method with state constraints is proposed to prevent the occurrence of inlet unstart. Firstly, a parametric model of AHV with velocity, flight path angle, angle of attack and angle of attack rate as state variables is derived. Then, adaptive dynamic inverse control is adopted for the velocity subsystem, and adaptive backstepping control with state C is adopted for the flight path angle subsystem. The tracking errors of angle of attack and angle of attack rate are constrained by asymmetric barrier Lyapunov function (ABLF) and symmetric barrier Lyapunov function (SBLF) respectively, and smooth saturation function is constructed to restrict the virtual control commands. Adaptive laws are used to handle parameter uncertainty. Finally, it is proved by Lyapunov theory that the states of the closed-loop system can be uniformly and ultimately bounded, and the constraints on angle of attack and angle of attack rate can be satisfied. The simulation results show that compared with the adaptive backstepping control method, the proposed method can guarantee that the angle of attack and angle of attack rate are always within the operating limits of scramjet engine, and effectively avoid the occurrence of inlet unstart. • A parameterized model is derived for air-breathing hypersonic vehicles. • An adaptive backstepping control method with state constraints on angle of attack and angle of attack rate is proposed. • An smooth saturation function is used to limit the virtual commands so that the differentials of the virtual commands are continuous. • Comparative simulations are provided. [ABSTRACT FROM AUTHOR]

The flow characteristics of injectors with oscillations play a significant role in the mechanism of combustion instability. And combustion instability reduces engine reliability. Therefore, an efficient VOF-to-DPM model-based method is proposed to evaluate the effect of inlet mass flow rate oscillation on the injectors in liquid rocket engines. In this method, the VOF-to-DPM model, which can portray the complete spray process with less computational cost than the VOF method, is adopted to simulate the whole spray process of the injector under oscillations. The proposed method is first verified by the reported simulation work. Then, it is applied to study the flow characteristics (response and spray characteristics) of the simplex swirl injector under different inlet mass flow rate oscillations. The result of the proposed method indicates that the simplex swirl injector is sensitive to the oscillation of 200–300 Hz, which is consistent with the reported experimental work. Additionally, inlet oscillation frequency dominantly increases the phase difference while frequency and amplitude jointly determine the amplification or attenuation of the outlet mass flow. The injector with 250 Hz has a higher velocity of downstream recirculation and smaller droplets than other oscillation frequencies, which may provoke combustion instability. The numerical results are beneficial to injector design and reduce the possibility of combustion instability by active regulation. The proposed method contributes to revealing the mechanism of combustion instability and improving the reliability of liquid rocket engines. • A VOF-to-DPM model-based methodology for swirl injectors is proposed. • This proposed methodology is verified by the reported work. • The method has achieved the whole spray process of the injectors with oscillations. • Provide an efficient tool for injector dynamics. [ABSTRACT FROM AUTHOR]

• A BOG buffer tank and a control strategy is proposed to optimize the liquefaction process and can maintain the stability of the system. • The inlet gas volume increases by 12.2% and system specific energy consumption is reduced by 5.7% compared with the reference process. • The results of the simulation data provide an identifiable scale demarcation for the control strategy. • The optimal intake ratio exists which can be more responsively adjusted and adapted to process fluctuations in actual operation. The re-liquefaction of BOG is a necessary part of the safety and security of LNG cargo ships. And the volatility of BOG will fluctuate with the sea conditions of ship transportation, so how to deal with the fluctuation of the re-liquefaction system and improve the liquefaction capacity is a problem that cannot be ignored in the operation of the liquefaction system; In this paper, a BOG buffer tank is added to the Reverse Brayton Process. Moreover, a control strategy is proposed to optimize the liquefaction process. The proposed four possible operating conditions' efficiency,the specific energy consumption (SEC), liquefaction rate and main heat exchanger parameters were simulated and analyzed by using Aspen HYSYS software. According to the results, the specific energy consumption of the basic re-liquefaction process is 1.329 kWh/kg LNG , which is 5.7% less than that of the reference process; In the study of flow fluctuation, after adopting the control strategy, the specific energy consumption of the whole process is 1.29 kWh/kg LNG , with 15.6% efficiency and 99.5% liquefaction rate. The whole system can be maintained at a low specific energy consumption level when the feed gas volume is fluctuating. The analyses of various BOG composition and the parameters of the main heat exchanger show that the regulation of the inlet gas volume can make the primary re-liquefaction process flexible and maintain the heat exchanger in a good working condition; Even if the system is in a worse working condition, the inlet gas volume can be improved by 12.2% compared with the reference process. [ABSTRACT FROM AUTHOR]

This paper presents a study on the influence of inlet radial angle in a multi-inlet cyclone separator using Eulerian-Lagrangian (EL) fluid dynamics approach. The investigation focuses on the behavior of air and solid particles within the cyclone. Air circulation was simulated at velocities ranging from 2 to 6 m/s, with inlet radial angles of 15°, 32°, 45°, 61°, and 72°. To model the turbulent flow, the Reynolds stress model (RSM) and renormalization group k-model (RNG) were employed, while the particle trajectories were simulated using the discrete phase model (DPM) in ANSYS Fluent. The purpose of this study was to determine how the inlet radial angle impacts various parameters: collection efficiency, pressure drop, cut-off diameter, axial velocity, and tangential velocity. The numerical data obtained from the simulations were validated and found to be consistent with the existing literature. The results revealed interesting findings. In the case of an inlet velocity of 6 m/s, the highest pressure drop of 84.5 Pa was observed for the 15° inlet radial angle, while the lowest pressure drop of 77.42 Pa was observed for the 32° inlet radial angle. It was found that the collection efficiency varied according to the radial angle of the inlet, with values of 89.00%, 91.70%, 92.50%, 94.77%, and 94.83% for 32°, 45°, 15°, 72°, and 61°, respectively. Additionally, at an inlet velocity of 2 m/s and a radial angle of 72°, 61°, 15°, 45°, and 32°, the corresponding cut-off sizes were determined to be 1.17 μm, 1.19 μm, 1.25 μm, 1.33 μm, and 1.38 μm, respectively. At an inlet velocity of 6 m/s, the peak tangential velocities were found to be approximately 1.48, 1.44, 1.44, 1.39, and 1.34 times the inlet velocity for the 15°, 72°, 61°, 45°, and 32° radial angles, respectively, within the axial location range of z = 1.5 D to z = 3.4 D. The peak axial velocity values for the 32°, 72°, 45°, 15°, and 61° radial angles, were reported as 0.85, 0.89, 0.92, 0.94, and 0.96 times the inlet velocity respectively. [ABSTRACT FROM AUTHOR]

Heterogeneous reaction characteristics of premixed H 2 /Air mixture are numerically investigated in micro combustor with coating platinum (Pt) catalyst on the inner wall. The well-designed combustor with the inserted baffle is committed to improving the transport of bulk species on the catalytic surface, therefore enhancing the fuel conversion ratio. A two-dimensional numerical model with detailed heterogeneous reaction mechanism is developed and verified. In this work, the numerical results reveal that the heterogeneous reaction rate and fuel conversion ratio are significantly improved in the combustor with inserted baffle. The velocity of gaseous mixture swiftly increases between the baffle and catalytic surface, resulting in the increasing adsorption-desorption of bulk species on the catalytic surface. The main influencing factors of inserted baffle body comprise of slit width between two ribs in the same row (W), rib length (L), distance between adjacent baffles row (D), number of baffle row (n) which are studied to obtain a set of optimized parameters of baffle in the well-designed combustor. The optimized parameters of the baffle are W = 0 mm, L = 0.4 mm, D = 4 mm and n = 4, which are employed in the combustor to obtain a high hydrogen conversion ratio. Moreover, the effect of different inlet velocities and equivalent ratios of the mixture on the heterogeneous reaction characteristics are carried out in the designed combustor. As the designed combustor performs well, and the improvement effect of the optimized baffle gradually increases together with the inlet velocity, particularly for high inlet velocity (7 m/s). The promotion effects of baffle in the designed combustor are presented when the rich and lean fuel are adopted at inlet velocity of 7 m/s. Finally, the relative parameters of this work can serve as a reference and guidance for the design of micro scale combustor. • A digital model for a catalytic micro combustor with baffles is established. • Optimization of baffle parameters is found to improve the combustor performance. • Effect of varying inlet conditions on the well-designed combustor performance is investigated. • The principle of enhanced heterogeneous reaction in a micro combustor is explored. [ABSTRACT FROM AUTHOR]

A three-dimensional single-flow channel computational model is used to investigate the performance characteristics of polymer electrolyte fuel cells (PEFC). The combined influence of non-uniform interfacial contact resistance (ICR) and inlet relative humidity (RH), along with the heterogeneous flow properties of the gas diffusion layer (GDL) on the PEFC performance is evaluated. The study considers combinations of full and partial humidification of anode and cathode reactants. Results reveal heterogeneous GDL with non-uniform ICR distribution results in a slight ∼4.4% reduction in current density at 0.3V compared to the homogeneous case. However, under same electrical/flow heterogeneities, the current density is observed to increase by ∼19% to ∼1.3A/cm2 under fully humidified anode and partially humidified cathode (i.e., RH a |RH c = 100%|60%) as compared to ∼1.1A/cm2 under symmetric RH a |RH c = 100%|100%. Interesting observations are made on the temperature distribution and cathodic water fractions. The variation in anodic inlet humidity is observed to have no impact on temperature distribution in the membrane, whereas variation in cathodic inlet humidity is effective in reducing the temperature in the channel regime with a 4K (kelvin) difference among all the cases. It is noted here that the overpotential map is not an indicator for performance loss, at least at full inlet humidity. This parameter is observed to depend on water concentration in the cathode. The study provides a detailed analysis of the distribution of reactant mass fraction, water concentration, current density, temperature, cathodic overpotential, and cell performance for all the simulated cases. • Effect of electrical/flow heterogeneity of GDL under different inlet humidification is simulated. • Heterogeneity lead to ∼4.4% reduction in current density (from ∼1.2A/cm2 to ∼1.15A/cm2) under full humidification. • ∼19% increase in current density (from ∼1.1A/cm2 to ∼1.3A/cm2) is observed with RH a.|RH c = 100%|60% • Temperature distribution in membrane is dependent function of cathode inlet humidity. • Overpotential is independent indicator of PEFC performance variation. [ABSTRACT FROM AUTHOR]

The effect of the gas inlet distance on the quality and yield of carbon nanotubes (CNTs) is studied through the on-line intermittent method via a previous self-made tapered fluidized bed reactor (TFBR). The CNTs are catalytically grown on the Fe-Co-Mo/Al 2 O 3 and Fe/Mo/Vermiculite catalyst at different inlet distances (DIDs), which clarify the effect of inlet distance and explore the optimum location. The whole process of CNTs growth in the TFBR without a distributor is explored. The effects of DIDs on catalyst flow and CNTs growth are discussed as well. Additionally, the morphology, quantity and quality of multi-walled carbon nanotubes (MWCNTs) are systematically characterized by using scanning electron microscopes (SEM), Brunauer Emment Teller (BET) and Raman Spectra. The results show that the CNTs prepared at 50 mm from the bottom of the cone have lower ash content and defect, and higher quality compared to other locations. That is, the airflow from 1/2–3/4 of the cone bottom could improve the catalytic performance of the catalyst, which results in the CNTs prepared have an excellent structure and high-efficiency carbon conversion rate. ● The optimum inlet distance of CNTs is investigated in a TFBR. ● The V-CNTs is less affected by the inlet distance than A-CNTs. ● The effect of inlet distance on V-CNTs and A-CNTs has similarity. [ABSTRACT FROM AUTHOR]

In this study, the adaptive mode switching process of rotating detonation waves (RDWs) in response to the change of inlet conditions is numerically explored and analytically explained. Once a quasi-steady rotating detonation flow field is obtained, the inlet total pressure of the reservoir is decreased and maintained at different levels for a certain period of time in order to observe the feedback on the RDWs. It shows that instead of being quenched immediately, the RDWs can adapt to the change of inlet conditions by a mode switching adjustment; it decreases the number of detonation waves and begins to run in a new operating mode, a process that is found to occur swiftly and is corroborated by experimental observations; moreover, an analytical analysis indicates that for a stable RDW flow field, the characteristic parameters such as the number and height of detonation waves are related to the combustor geometry and inlet conditions, which determine whether the RDWs are required to switch into a new operating mode as a means to ensure stability. Additionally, the results indicate that the rotating detonation engine (RDE) can work in different operating modes at the same mass flow rate, or conversely, the RDE can remain in the same operating mode even if the mass flow rate varies. • Numerical simulations are conducted to investigate the operating modes of rotating detonation engines (RDEs). • The RDE can adapt to the changes of inlet conditions and switch its operating mode when necessary. • A quasi-steady analysis of the rotating detention waves is provided to explain the adaptive mode switching process. [ABSTRACT FROM AUTHOR]

• A spray pre-cooled NDDCT model under crosswind conditions was developed. • The behavior of droplets under crosswind and no crosswind were compared. • Feasible nozzle arrangements were explored under different crosswinds. • Good nozzle arrangement should consider height, radius, spray angle and crosswind. Crosswind affects the airflow fields of the natural draft dry cooling towers (NDDCTs), thus the spray zones for pre-cooling the inlet air of the NDDCT might be different from no crosswind. Therefore, a 3-D model of pre-cooled NDDCT under crosswind was established by Fluent 16.2 to investigate the feasible zone of nozzle spray of a 120 m high NDDCT based on the behavior of the droplets. Six nozzle heights, nine nozzle radiuses and four spray angles were simulated for the NDDCT application within the crosswind speeds of 0∼10 m/s. The evaporation percentage of droplets higher than 99% and the maximum effective evaporation ratio are selected as the criterion for the feasible zone of nozzle arrangement. Simulation finds that: (1) the nozzle arrangement height should be set at 7 m when the crosswind speed is 0 m/s, and it should be set at 9 m when the crosswind speeds are 2 m/s, 4 m/s,6 m/s, 8 m/s and 10 m/s, respectively. (2) The feasible spray angles of nozzles are 0°and 90° at the crosswind speeds of 0∼4 m/s and 6∼10 m/s, respectively. (3) The nozzle radiuses are 0∼41.5 m at crosswind speed of 0 m/s, they are 0∼21.5 m at the crosswind speed of 2 m/s, and they are 0∼16.5 m when the crosswind speeds are 4 m/s, 6 m/s, 8 m/s and 10 m/s, respectively based on the above feasible heights and spray angles. The results will provide a guidance for nozzle design of spray pre-cooled NDDCT under crosswinds. [ABSTRACT FROM AUTHOR]

The study was dedicated to the mathematical modeling of the catalytic reverse-flow process in reactors of different design, e.g. in reactors with axial, side or tangential arrangement of reaction gas inlet/outlet streams. The oxidation of volatile organic compounds in the fixed adiabatic catalyst beds was considered, using toluene as an example contaminant. Three-dimensional fluid dynamics modelling performed by means of Comsol Multiphysics software showed the existence of the significant gradients of temperature, concentrations of reactants and fluid velocities along the bed radius; such gradients are neglected in the conventional one-dimensional models, usually used for simulation of reverse-flow processes. The spatial distribution of these parameters may be asymmetric in the reactors with asymmetric design. It was shown that efficiency of both toluene conversion and heat regeneration significantly decrease in reactor with side feeding of inlet mixture, finally resulting in lower thermal stability of the process with the significant (∼20%) decline of the maximum possible duration of the cycles between flow reversals compared to reactor with axial gas feeding. Vice versa, the tangential arrangement of gas inlet provides the visible (∼10%) increase of maximum cycle duration. Application of 3D modelling approach to development and optimization of catalytic processes becomes especially important in case of reverse-flow reactors where negative influence of various spatial non-uniformities may impose more significant influence on process parameters. • 3D mathematical modeling of reverse-flow reactors performed. • Significant radial temperature and composition gradients in catalyst bed exist. • Asymmetry in reactor design may cause asymmetry of heat waves. • Side feed inlet may significantly decrease process thermal stability. • Tangential feed inlet increases process stability. [ABSTRACT FROM AUTHOR]

This paper explores the potential of water jet eductor to replace large condensers and vacuum pump in the thermal desalination systems, with heat source temperatures below 95 °C. The operational limit of eductor has been investigated for active vapor transport and condensation to produce permeate. Combined system and its operational principle have been proposed with critical examination based on suction performance of Eductor. Experimental and computational study are the primary methodology of this work. The computational analysis of single-phase flow in Eductor, is in proper agreement with the experimental data. The result showed primary pressure & area ratio has positive impact and swirl ratio has negative impact on suction. The extended thermal analysis summarizes strength of Eductor while working with lower temperature sources and optimum cooling capacity of proposed system. Considering the simplicity and reduction in footprint, proposed application has been highlighted. The research disseminates knowledge on maximum vacuum generation capacity of Eductor and operational limit of thermal desalination system. [ABSTRACT FROM AUTHOR]

Water and solid particles, such as wear particles and sand, will enter lubricating oil during the operation of machinery, seriously affecting the performance and lifetime of the oil, and adversely affecting the machinery. Therefore, a device for simultaneously extracting water and solid particles mixed with lubricating oil is proposed. For such a device, a numerical model is established by combining mixture, Reynolds-stress, population-balance, and discrete-phase models to investigate the influence of inlet velocity and solid separation gap on separation characteristics, and the three-phase separation experiment is carried out. Results show that the oil-water-solid phase separating device delivers an excellent performance, and that the dewatering, deoiling, and solid particle recovery rates reach 76.9 %, 88.55 %, and 88.97 %, respectively; and separation time of solid particles and droplets and the tangential velocity increases with the increase of the solid separation gap. Furthermore, at an inlet velocity of 9 m/s, a large tangential velocity is generated to provide a strong centrifugal force while maintaining the stability of the internal flow field. This work provides a valuable guide for the design of high-performance devices for lubricating oil purification using physical methods. [Display omitted] • A device for separating three phases: oil, water and solid was proposed. • Numerical model of the three-phase separating device was established. • Separation characteristics of the device were investigated. • Optimum inlet velocity and solid separation gap were obtained. [ABSTRACT FROM AUTHOR]

The flow response hysteresis in a mixed-compression supersonic inlet's throttling/unthrottling process is unconducive to its practical engineering applications. To suppress such hysteresis, herein, a flow control method based on a distributed bleed system in the inlet's internal contraction part was proposed and applied to a rectangular supersonic inlet with a designed Mach number of 4.0 and an internal contraction ratio of 1.5. All tests were conducted in a supersonic wind tunnel at a freestream Mach number of 2.9, and the relevant test data were obtained using the high-speed schlieren and dynamic pressure measurement systems. The results indicate that the distributed bleed system improved the uncontrolled inlet's unstart throttling ratio from 43.8% to 47.3% and the restart throttling ratio from 29.4% to 47.1%, and it essentially eliminated the flow response hysteresis during the throttling/unthrottling process. Moreover, the hysteresis mechanism of the uncontrolled inlet, dominated by the separation-induced flow structures in the internal contraction part, was investigated to help elucidate the targeted control mechanism of the bleed system that suppresses the hysteresis. Finally, the specific flow phenomena in the oscillation of the controlled inlet were examined to study the bleed system's impact on the unsteady flowfield, including the coupled flow of the mainstream with the bleed system and complex wave motion structures. • Flow response hysteresis in a mixed-compression supersonic inlet's downstream throttling/unthrottling process is experimentally investigated. • An effective hysteresis suppression method based on a distributed bleed system is proposed. • New flow phenomena in the oscillation of the inlet under bleed control were examined. [ABSTRACT FROM AUTHOR]

Unexpected spontaneous combustion and shock waves can occur when high-pressure hydrogen leaks into pipelines, whilst irregular leakage ports affect their features. In this paper, shock waves and self-ignition are experimentally and numerically studied after the pressurized hydrogen is released through the partially open inlet. And the effects of tube length and release pressure are investigated. Pressure signals, light signals, and flame images are used to characterize the shockwave, self-ignition, and flame propagation. Results show that the shock-affected region can be formed near the partially open inlet. It is accompanied by complex wave structures, shock wave interactions, and shock wave focusing. The contact surface is distorted and deformed. The flow field parameters near the inlet change dramatically and are unevenly distributed, which affect the overpressure characteristics recorded by the pressure sensors. The initial intensity of the shock wave is lower than that in tubes with the fully open inlet at the early stage of the leakage. In addition, the partially open inlet influences the critical pressure at which spontaneous ignition occurs and the flame evolution inside or outside the tube. It has an inhibition effect on spontaneous ignition, but this inhibition effect weakens with increasing tube length. [ABSTRACT FROM AUTHOR]

Coal-derived liquid fuels (CDLs) are petroleum diesel's (PD) alternatives produced by coal liquefaction. The injection and non-evaporating spray characteristics of CDLs, including diesel from direct coal liquefaction (DDCL), diesel from indirect coal liquefaction (DICL), and their blends (DBCL), were discussed. The high-pressure common rail test bench was used to evaluate the injection delay, injection rate, injection quantity, single injection heat value, and injector inlet pressure. A constant volume chamber along with high-speed camera was used to visualize the spray, then measuring the spray tip penetration distance, spray cone angle, and spray area. Besides, injection tests were conducted using injectors removed from engines that had finished durability tests fueled with DBCL and PD. The results revealed that DDCL had shorter injection delays and more mass injection quantity than PD, with an injection heat value 7 % higher at a rail pressure of 140 MPa. Regarding the spray, PD had a longer spray tip penetration distance and smaller cone angle than CDLs. On test conditions, the spray Sauter mean diameters of DDCL and DICL were over 30 % less than that of PD. Inferring from the reduction in injection rate and quantity, PD generated more clog in the injector hole than DBCL. • Injection and spray characteristics of CDLs and PD were investigated. • Single injection heat values of CDLs were higher than that of PD. • Injector hole clogging of engines fueled with DBCL and PD were reported. [ABSTRACT FROM AUTHOR]

The problem of ash deposition on the surface of photovoltaic (PV) arrays during actual operation seriously affects their power generation efficiency. Because traditional research does not consider the PV module spacing, it cannot reflect the actual PV array ash deposition problem. This study explored the influence of PV module spacing, combined with different tilt angles and inlet wind speeds, on the characteristics of ash deposition and power output of the PV array through indoor experiments. The study designed a set of experimental equipment for simulating the formation process of ash deposition on the surface of PV arrays and set up an experimental platform to measure the influence of ash deposition on the maximum output power (P max), open-circuit voltage (U oc), and short-circuit current (I sc) of the PV modules. The findings indicate that as the tilt angle increases, the PV array experiences reduced ash deposition and increased output power. Conversely, higher inlet wind speeds lead to greater ash deposition and decreased output power. Moreover, widening the spacing between PV modules results in increased ash deposition and reduced output power. Notably, within the PV array, the front PV module accumulates more ash than the rear module, with larger particle sizes. These research findings have significant implications for optimizing PV array design and enhancing power generation efficiency. • Investigated the impact of PV module spacing, tilt angles, and wind speeds on ash deposition and power output through indoor experiments. • Designed experimental equipment to simulate ash deposition on PV array surfaces. • Designed a platform to measure how ash deposition affects PV array output. [ABSTRACT FROM AUTHOR]

To obtain the ignition performance of an integrated inclined combustor, we perform an experimental study on the ignition performance of an inclined combustor under various ignition positions, inlet flow rates, and fuel air ratios (FARs). The experimental results reveal the following. 1) During ignition at I1, the inclined combustor presents the best ignition performance. 2) The forward propagation process of flame along the swirler's inclined direction easily realizes flame propagation, whereas the backward flame propagation process in the swirler's inclined direction is difficult to achieve; forward and backward flame propagations exhibit evident differences. 3) The diffusion propagation of swirl flames at the ignition head is the main means swirl flames are generated at the nonignition head. 4) During the ignition process, the combustion intensity increases with the increase in FAR and decreases with the increase in inlet flow rate. 5) The successful ignition time decreases with the increase in inlet flow rate and FAR. • Proposed an integrated inclined combustor technology. • Explored the difference between forward and reverse flame propagation in an integrated inclined combustor. • Revealed the effects of different ignition positions on ignition circumferential propagation performance. • Quantitative analysis of the effects of inlet flow rate and fuel gas ratio on flame dynamics. [ABSTRACT FROM AUTHOR]

• A CG CFD-DEM is established to study particle motion behavior in cyclone combustor. • Effects of four different structural parameters are explored. • Increasing the primary inlet number decreases the average parcel residence time. • The addition of secondary inlet generally elevates the overall parcel height. • Including diversion structure raises likelihood of small parcels in near-wall zone. A coarse-grained computational fluid dynamics-discrete element method (CFD-DEM) was established to investigate the influence of cyclone combustor structure on the motion behaviors of solid fuel particles. Four structural parameters, i.e., primary inlet number (P n), secondary inlet number (S n), secondary inlet location (S L), and guide blade angle (α), were examined. Compared to the base structure with a single primary inlet, the addition of extra primary inlet, secondary inlet, or diversion structure elevates the global parcel location. Increasing P n and S n decreases the average parcel residence time, while augmenting S L and α generally lengthens it. Meanwhile, increasing P n , S n , and S L or decreasing α broadly reduces the wall parcel-hold ratio. Furthermore, the inclusion of secondary inlet and diversion structure increases the probability of small parcels occurring in the near-wall zone. These observations are helpful for optimizing the design and operation of cyclone combustors. [ABSTRACT FROM AUTHOR]

• Enhanced stability for ultra-high-load transonic rotors via tailored casing treatment strategy. • Insights into stall mechanism shifts post-casing treatment. • Revealed unsteady mechanisms to suppress unstable flow structures. • Stall margin is extended by approximately 12 %. Low-reaction compressors are promising for achieving high loads but face severe flow instability challenges. This study investigates a low-reaction transonic compressor rotor using casing treatment technologies to control unstable flow dynamics precisely. First, a design integrating self-recirculating and circumferential groove casing treatments near the leading edge is implemented. This design enhances flow capacity at the tip passage inlet. However, it causes a "stall transposition" phenomenon. The unstable flow structures shift from shock-tip leakage vortex interactions at the front to corner separation at the rear. Consequently, the stall mechanism transitions from an end-wall stall to a blade stall. To address this issue, a new casing treatment layout is proposed. Grooves are added after the mid-chord of the initial front casing configuration. This adaptation suppresses emerging unstable flow structures and extends the stall margin by approximately 12.07 %. Detailed flow field analysis shows that the rear grooves effectively reduced the trailing edge separation vortex. They also limit downstream corner separation and mitigate disturbances from tip leakage flows in the rear of the passage. [ABSTRACT FROM AUTHOR]

• An inlet-engine hybrid integrated modelling method with pressure dynamic self-tuning. • The proposed method combines the advantages of volume effect model and component level model. • A flight envelope verification on an actual controller proves its excellent stability and real-time performance. • The accuracy of the proposed method is verified by ground experimental data. With aircraft flying faster and higher, the interaction between the inlet and engine cannot be ignored. The inlet engine integration characteristics must be considered in engine design and performance evaluation. The total pressure between the inlet and compressor is a critical parameter that directly affects the accuracy of engine performance evaluation. The traditional solution to inlet-engine integrated modelling is to add an external balance equation to the component-level model (CLM), which may reduce real-time performance. In this study, an inlet-engine hybrid integrated modelling (IEHIM) method is proposed to solve this problem, which combines the advantages of the volume effect model and the CLM method. The proposed IEHIM method consists of an engine model, characteristics of the inlet component, and a pressure dynamic self-tuning (PDST) algorithm. The PDST algorithm coefficients were optimised to enhance the performance of the IEHIM method. Finally, the effectiveness of the IEHIM was verified through simulations and ground experiments. The method was also verified on an actual controller (operating frequency: 132 MHz), which exhibited a mass-flow matching error below 0.2 % and an average time consumption of 5.191 ms in each control cycle. The results were also compared with the actual experimental data, where the errors in the compressor entry total pressure and rotor speed were below 1.1520 % and 1.2195 %, respectively. [ABSTRACT FROM AUTHOR]

Density wave oscillation (DWO) in parallel channels is an important problem that has been widely studied. The marginal stability boundary (MSB) is often found to be " L " shaped on the N pch - N sub plane, but some very different shapes were also reported. In this paper, the instability marsh region which could occur in the traditional instable region but having both instability and stability sections was presented and discussed, which is found to be an explanation of the distortion of MSB. The analysis of the instability marsh region showed that the evolution of instability marsh should be due to the stability change when operation condition changes, which can be estimated with the analysis of the two-phase and single phase pressure drop variation, as well as Ma's stability criterion for different heat flux profiles. Variation of instability marsh with different heat flux profile, inlet and outlet resistance coefficient, mass flow and pressure were obtained and analyzed, and the effects of these parameters on instability marsh variation were found to be well interpreted with stability change. The calculation and analysis of instability marsh showed a clear evolution figure of the distortion of MSB under different conditions, and related research could be helpful in better understanding the flow instability in parallel channels. [ABSTRACT FROM AUTHOR]

The most important characteristic of main Steam Line Break (SLB) accident is the asymmetry cooldown between loops due to secondary break spurting, which results non-uniform reactivity feedback in different reactor core sections. The fuel rod DNBR limit would be more challenged in the core section with peak power. The SLB safety analysis methodologies in Administration License Application for typical PWR in China are investigated in this paper. Based on the conservative universal methodology, the best-estimated code RELAP5/MOD3 is used to perform the SLB thermal-hydraulic calculation for a three-loop PWR. In this analysis, the critical conservative models submitted for Licensing process are implemented in RELAP5/MOD3 specified modeling, which includes the Three-Channel Core Model, core inlet mixture array, core outlet mixture, vessel upper head flow and the more realistic SG model. The "second pressurizer" phenomenon in vessel upper head flashing is studied, which affects the system pressure response and mitigation. The effect of SG spouting during the transient is also studied in this paper, which is different with lumped parameter SG model. The combined approach for Deterministic safety analysis is validated in this paper, which is composed with best-estimated code, Conservative assumptions and Conservative initial & boundary conditions. Because of the flexibility and adequate conservatism, it can be spread for design optimization and independent safety assessment from the third party. [ABSTRACT FROM AUTHOR]

• Experimental and numerical methods are used to analyze the effect of non-uniform flow on the pressure distribution of RCPs' inlet and outlet. • Different pressure averaging methods are used to investigate the flow structure and the errors under different inflow conditions. • This research establishes a head correction formula under non-uniform inflow conditions, which can be used for the subsequent optimization design of the RCPs. The reactor coolant pump (RCP) in Advanced Passive (AP) series reactors is directly connected to the bottom of the steam generator (SG), which could cause an irregular flow pattern at the pump inlet. This type of inflow is called non-uniform inflow and would lead to changes in the pressure field distribution at pump inlet. Generally, a surface averaging method is used in numerical simulations for the inlet and outlet to calculate the pressure and thus the head. Nevertheless, this approach would introduce an additional error between the experimental and numerical heads under non-uniform inflow condition. In this study, experimental and numerical methods are used to analyze the effect of non-uniform flow on the pressure distribution of RCPs' inlet and outlet. Different pressure averaging methods are used to investigate the flow structure and the errors under different inflow conditions. The results show that there is no difference between different pressure averaging methods under uniform inflow condition, while the error between different pressure averaging methods reaches up to 2.46% under non-uniform inflow conditions. By comparing with the experimental results, this research establishes a head correction formula under non-uniform inflow conditions, which can be used for the subsequent optimization design of the RCPs. [ABSTRACT FROM AUTHOR]

The organic Rankine cycle coupled vapor compression refrigeration system is an attractive refrigeration technology that converts low-grade thermal energy into cooling capacity to improve waste heat utilization efficiency. Due to the inevitable change in ambient temperature and cooling demand, the dynamic characteristics of the combined system are worth studying. In this paper, a small experimental apparatus with a common condenser is designed and developed. The dynamic characteristic experiments under different disturbances are carried out to understand the response characteristics of operating parameters and the variation of system performance. The results show that the maximum response time of the system under different disturbances ranges from 493 s to 694 s. The impact of throttle opening on the response characteristics of refrigeration subsystem parameters is significantly higher than that of the organic Rankine cycle. The mass flow rate of organic Rankine cycle has the fastest response to pump frequency, while the compressor inlet temperature changes rapidly with the cooling water temperature. Under a step cooling water temperature, it is important to control the compressor inlet temperature to avoid liquid droplets in its inlet. In addition, the mass flow rate of organic Rankine cycle should be controlled reasonably to achieve the maximum coefficient of system performance. The cooling capacity of the system is mainly affected by the cooling water temperature and the throttle valve opening. During the experiment, the maximum cooling capacity and performance coefficient of the system are 3.75 kW and 0.275, respectively. This work can provide guidance for the design of the control strategy of the combined system. • An organic Rankine cycle coupled vapor compression refrigeration system was built. • Dynamic characteristics of the combined system under various disturbances were tested. • Response time and change rate of main parameters were provided. • System has a large thermal inertia with a maximum response time of 694 s. [ABSTRACT FROM AUTHOR]

Emissions requirements, performance expectations, and expanding range of fuels for off-road engines are broadening engine air system requirements. As part of reducing engine development cost and risk, virtual engine simulation is used to select architecture and components capable of covering a broad range of requirements through low risk changes to the turbocharger turbine. A method is presented for predicting turbine performance changes due to turbine housing area change, the most effective of these low risk changes, from available turbine map data. The method, developed from a mean line model, learns four simplified geometry parameters, three loss coefficients, and two maximum efficiency rotor inlet incidence coefficients from a training turbine map data set, then predicts a scaled turbine map for changes to a simplified geometry parameter associated with housing area. Reduced mass flow RMS errors less than 4.3% and efficiency RMS errors less than 5.2% are expected when generating scaled turbine maps with this method, which is additional 2% error for flow and 3% error for efficiency over that expected when modeling actual turbine map data. • Turbocharger turbine mapping data is modeled using a mean-line model. • Simplified geometry parameters are determined from turbine mapping data. • When changing housing A/R, efficiency is shifted in pressure ratio and scaled. • Estimated turbine map is generated for changes to simplified geometry parameters. • Virtual engine can predict engine performance changes from estimated turbine map. [ABSTRACT FROM AUTHOR]

• A model for a three-phase separator is developed using population balance modeling. • The model considers the inlet and separation sections for steady and transient cases. • The model is tested against experimental data for a pipe separator. In this study, we have developed a mathematical model for a three-phase separator. The model consists of two sections: the inlet section and the separation section, separated by a perforated calming baffle. In the inlet section, two dispersion layers undergo droplet size evolution due to turbulent breakage and coalescence, described by a spatially homogeneous PBE. In the separation section, the two dispersion layers flow alongside each other and interact at an interface. The volumetric flow and velocity profiles are influenced by interfacial coalescence, with considerations for plug and laminar flow assumptions. The model incorporates droplet gravity-driven transport using the Kumar and Hartland model, binary and interfacial coalescence employing a film drainage model, and an effective diffusion term to account for the formation of the dense packed layer which ensures a physical volume fraction range of 0–1. Steady-state and transient numerical solvers are developed to solve the resulting advection–diffusion equations. Additionally, a series of experiments were conducted using a lab-scale multi-parallel pipes separator to investigate the impact of varying volume fractions and flow rates on the separation efficiency of the equipment. The model results are compared with the experimental data which shows relatively good agreement. [ABSTRACT FROM AUTHOR]

[Display omitted] • NETmix performance was assessed for dissimilar inlet flow conditions. • Similar outlet flowrates were obtained for all inlet flowrate ratios studied. • A uniform flow distribution is achieved after at least 10 NETmix rows. • Spectral analysis allowed to determine the frequency of oscillation of the flow. • Increasing Re led to an increase in the size of vortices in the NETmix chambers. The mixing dynamics that occur inside the NETmix reactor have been previously thoroughly studied for equal feed streams distributed through the inlets. To broaden the applicability of this static mixer, this work intends to expand the knowledge of the mixing dynamics mechanisms for cases where dissimilar inlet flowrates are imposed. Computational Fluid Dynamics (CFD) tools were used to simulate flow dynamics experiments in a reduced NETmix geometry for different inlet flowrate ratios. The simulation results show that this reactor can attain the desirable condition of similar outlet flowrates for several dissimilar inlet flow conditions. A flow dynamics analysis enabled the determination of the natural frequency of oscillation of the flow and related it to the volume of the chambers occupied by vortices. Finally, the velocity fluctuations at the centre of NETmix chambers were characterised in terms of the intensity of turbulence. [ABSTRACT FROM AUTHOR]

The North Frisian Wadden Sea (NFWS), an open tidal basin within the UNESCO World Heritage Wadden Sea, is characterized by its barrier systems, tidal inlets, intertidal flats, and estuaries. Unlike its East Frisian and Dutch counterparts, the NFWS is underexplored in terms of residual sediment and flow transport pathways—knowledge crucial for coastal conservation and nature-based protection. These pathways are a product of complex interplay between tides, winds and waves that together shape the morphology of the NFWS. This study investigates these interactions using a high-resolution process-based model to perform a representative period simulation derived through a novel unfiltered-reduction technique. Our results reveal an anticlockwise residual flow circulation in the back-barrier region, which was not discernible in the residual sediment pathways. Waves primarily dictated sediment transport over intertidal flats, showing high variability in transport direction under energetic conditions. The coastline orientation and fetch size favored southward wavedriven sediment transport, opposing the northward residual flow transport driven by tidal propagation. A dynamic residual divergence pattern in the nearshore region of the barrier islands is also revealed for both sediment and flow, which moves alongshore during energetic events. The discussion compares these patterns and their implications with earlier local measurements, conceptual pathways, and different systems globally to provide a comprehensive overview of the transport dynamics in the NFWS. • A new unfiltered reduction technique is presented based on hindcast wind dataset for identifying representative periods. • Representative residual transport pathways are calculated using a high-resolution process-based model, resulting in a comprehensive overview of flow and sediment transport patterns in a mixed-energy tidal system. • The study demonstrates that there is not always agreement between residual flow and sediment transport pathways • Impact of tides, winds and waves on residual transport have been decomposed and quantified. • A dynamic residual divergence transport zone exists near the shore controlled mainly by the wave-driven forces. [ABSTRACT FROM AUTHOR]

• Experiment is conducted on an additive manufactured plate-fin precooler. • The temperature of hot fluid reaches up to 1300 K while pressure drop to 15 kPa. • A pressure recovery coefficient of 97% and a temperature drop of 40% are achieved. • Precooler's performance depends more on the hot fluid than on the cooling fluid. This paper introduces an original plate-fin precooler designed for potential applications in extreme low-pressure environments. Utilizing additive manufacturing technology, the heat transfer plate thickness is constrained to 2.0 mm, with channel widths inside the plate achieving 0.8 mm. Through experimental methods, this study aims to assess the precooler's performance and identify critical influencing factors. Experimental results indicate that the hot fluid inlet temperature to the precooler exceeds 1100 K, with static pressures dropping below 30 kPa. Despite these conditions, the precooler demonstrates an impressive pressure recovery coefficient exceeding 97 % and achieves a maximum temperature drop of 731.4 K for the hot fluid. Furthermore, it is observed that the overall performance of the precooler diminishes with increasing mass flow rates of the hot fluid, showing fluctuations of up to 25 % when assessed by the j/f 1/3 factor. Additionally, while the hot fluid inlet velocity exceeds 90 m/s, laminar flow predominates during the heat transfer process. Moreover, regardless of whether the cooling fluid experiences a phase change within the precooler, its heat transfer performance show priority than that of the hot fluid. Thus, changes in the mass flow rate of the cooling fluid have minimal impact on the overall precooler performance. Finally, the first-stage heat exchanger plays a critical role in the heat transfer process, accounting for over 2/3 of the total temperature and pressure drop for the hot fluid. This research is expected to contribute to the design of high-efficiency, low-resistance precoolers, particularly those applied for operation under negative pressure conditions. [ABSTRACT FROM AUTHOR]

In order to further explore the physical mechanism of rotating stall induced by different rim leakage flow intensification, the velocity distribution of the stall flow field of the mixed flow pump under different rim clearance scales was obtained by Particle Image Velocimetry technology. By comparing the flow structure under different shooting sections, different phases and different working conditions, the influence of rim clearance scale on the flow field near the wall of the mixed flow pump was revealed. The results show that under the design flow conditions, there is an obvious reflux phenomenon near the hub of the guide vane inlet of the mixed flow pump under the four kinds of rim clearance, but the intensity is weak, and it does not affect the main flow field in the impeller channel. With the increase of rim clearance scale, the leakage flow intensity also increases, and the main flow area affected by the TLV structure also increases. In the deep stall condition, the reflux vortex at the inlet of the guide vane of the mixed flow pump still exists at each clearance, but the unsteady flow structure begins to appear inside, especially the large secondary vortex structure formed at the guide vane inlet, which seriously blocks the main flow. With the increase of the rim clearance, the flow field at the inlet of the guide vane is also obviously affected, and the secondary vortex core gradually moves towards the end wall area, resulting in an increase in the blocked area in the flow field. At the same time, the unsteady flow intensity of the flow field shows a nonlinear increasing trend. The unsteady strength of flow field increases rapidly with small gap impellers, while the unsteady strength changes slowly with large gap impellers. This study provides a reference for optimizing the rim clearance of mixed-flow pump and improving the efficiency of mixed-flow pump. • The PIV shooting method of mixed-flow pump flow field under different rim clearances is introduced. • The formation mechanism and influence of leakage vortex in mixed-flow pump are revealed. • The relationship between the backflow vortex, the secondary vortex and the rim clearance in the mixed flow pump is investigated. • The formation mechanism and influence of leakage vortex in mixed-flow pump tip are studied.The influence of tip clearance on unsteady strength of flow field in mixed flow pump is studied. [ABSTRACT FROM AUTHOR]

This study introduces and evaluates five models of Mach 7 scramjet inlets designed to reduce side spillage. The baseline model is characterized as a 2D-wedge type inlet without sidewalls. To mitigate interference from expansion waves, an alternative model featuring a converging angle identical to the freestream Mach angle is proposed. Another inlet model presents each ramp's converging angle matched to the local Mach angle of its respective ramp. Subsequently, an inlet model with sidewalls attached to the baseline model is introduced, and an additional inlet model is presented with reduced-height sidewalls. Three-dimensional Reynolds-Averaged Navier-Stokes simulations are conducted for each inlet model, and the performance of the inlets is compared. The mass flow averaged properties at the isolator exit for each inlet model are computed. To evaluate the performance of engines equipped with each inlet model, thrust and specific impulse are determined using thermodynamic cycle analysis. Ultimately, net thrust is calculated by subtracting drag from thrust, and the results are compared. The inlet with converging ramps, which has the largest captured area, indicates the lowest net thrust, amounting to 38% of that of the baseline model. In contrast, the inlet with reduced height sidewalls represents the highest net thrust, which is 3.5 times that of the inlet with converging ramps. These results demonstrate that for scramjet inlet design, using sidewalls to reduce drag is a more effective method for reducing side spillage compared to employing converging ramps with a large captured area. • Five 2D-wedge-type scramjet inlet models to reduce side spillage are proposed. • A ramp with converging angles equal to the Mach angles increases the mass flow rate. • Lowering the height of the sidewalls improves flow uniformity. • The inlet model with reduced height of sidewalls shows the highest net thrust. • The sidewall is more efficient for reducing side spillage than the converging ramp. [ABSTRACT FROM AUTHOR]

The compressed air energy storage (CAES) system experiences decreasing air storage pressure during energy release process. To ensure system stability, maintaining a specific pressure difference between air storage and turbine inlet is necessary. Hence, adopting a judicious air distribution scheme for the turbine is crucial. Partial admission, based on reasoned nozzle governing methods, enhances system performance. This investigation explores the impact of varying partial admission ratio (PAR) and inlet pressure on flow dynamics and loss characteristics under rated output power. Full circumferential numerical simulations of a two-stage axial turbine within CAES system elucidates insights. First-stage efficiency declines linearly with decreasing PAR, while second-stage displays escalating reductions. Principally, turbine energy losses primarily stem from the entropy production rate (EPR) by turbulent dissipation and EPR arising from heat transfer with fluctuating temperature gradients. Partial admission significantly affects losses within the rotor, especially within the second stage. Leaving velocity loss for 50 % PAR is about 3 times that of 100 % PAR. The percentage of losses within R2 for 50 % PAR increases by 6.7 % compared with that for 100 % PAR. This research provides theoretical insights for designing, regulating, and optimizing nozzle governing and partial admission turbines in CAES systems. • 50 % PAR results in a 5.7 % decrease in overall efficiency compared with 100 % PAR. • The leaving velocity loss for 50 % PAR is about 3 times that of 100 % PAR. • Energy losses primarily stem from EPTD and EPFT, as well as a small portion of EPDD. • The percentage of losses within R2 at 50 % PAR increases by 6.7 % compared with 100 % PAR. [ABSTRACT FROM AUTHOR]

Particle velocimetry setup was used to accurately measure the velocity of SiO 2 particles. Subsequently, a titanium alloy erosion wear setup enabled the acquisition of data on erosion rate and erosion angle. Leveraging this data, the Tabakoff erosion wear model for compressors was established. Particle motion characteristics, blade erosion wear areas, and erosion rates were meticulously analyzed under no, tip, and hub distortions. The findings reveal that tip distortion has the most severe impact on compressor erosion wear, followed by no distortion, while hub distortion leads to the least erosion wear. In the rotor and stator blades, the maximum erosion rate increased by 51.6 % and 37.3 % under tip distortion and by 46.2 % and 28.6 % under hub distortion compared to no distortion. [Display omitted] • Influence of different radial inlet distortion on compressor erosion wear is studied innovatively. • A Tabakoff erosive wear model parameters for compressor obtained experimentally. • Different compressor erosion distributions and rates under different distortion conditions. • Tip radial inlet distortion causes the most erosion wear in compressors. [ABSTRACT FROM AUTHOR]

• The distribution of shaft injected H 2 can be studied through the use of RTD theory. • Changes in inlet flow rate and temperature affect the H 2 flow in distinct ways. • Correlations between the RTD of H 2 and the use of reducing gas is case-specific. Hydrogen, as a carbon-free reducing agent, can be adopted in the blast furnace (BF) ironmaking process to replace carbon-bearing materials towards green steelmaking partially. Theoretically, hydrogen can be introduced into the BF via shaft injection, and its residence time distribution (RTD) has not been studied or reported in detail in open literature. In this study, a multi-fluid BF model is developed further to investigate the RTD of hydrogen when injected into the BF through shaft inlets. It is observed that the RTD of shaft-injected hydrogen exhibits some features of piston-type flow but varies at different monitoring points. For the case studied, increasing the hydrogen injection rate decreases the average residence time of hydrogen from 12.2 s to 10.1 s. Similarly, increasing the hydrogen injection temperature slightly reduces the average residence time from 10.4 s to 9.5 s. These results indicate that the hydrogen flow rate has a relatively more significant effect on the RTD than the injection temperature. Moreover, it is found the utilisation efficiency of shaft-injected hydrogen is influenced by both the limited residence time and conditions on the trajectories followed by the fluid particles. The model presented in this study provides an alternative and cost-effective method to enhance our understanding of the hydrogen RTD inside an ironmaking BF. [ABSTRACT FROM AUTHOR]

The zinc smelting solution purification process regulates the oxidation-reduction reactions (characterized by the oxidation-reduction potential (ORP)) by controlling the amount of zinc powder added to remove the impurity ions. In order to ensure the optimal operation of the process, the target key technical indicators should be converted into the optimal setpoint of controlled variables (that is, ORP). Based on the mechanism knowledge, fuzzy rules, and preference-guided predictive optimization, a comprehensive setting method for the optimal setpoint of controlled variables under multi-variation inlet status is proposed. It includes a hybrid trend detection method for inlet status, a mechanism model under multiple operating modes, and a fuzzy correction method and a preference-guided predictive optimization method to deal with slight and violent fluctuations in the inlet status, respectively. The experimental results show that the proposed method can obtain the optimal setpoint of controlled variables and reduce zinc powder consumption by approximately 3.6%. • A comprehensive setting method for the optimal setpoint of controlled variables under multi-variation status is proposed. • A hybrid trend detection method is proposed to identify different inlet statuses of the solution purification process. • Based on the reaction kinetics and the reaction efficiency, a mechanism model under multiple operating modes is constructed. • An optimal setpoint correction method based on fuzzy rules is proposed to cope with slight changes in inlet status. • A preference-guided predictive optimization method is proposed to cope with violent changes or anomalies in inlet status. [ABSTRACT FROM AUTHOR]