Search

Machine learning is a promising method to model production processes and predict product quality. It is challenging to accurately model complex systems due to data scarcity, as mass customisation leads to various high-variety low-volume products. This study conceptualised knowledge accumulation, extraction, and transfer (KAET) to exploit the knowledge embedded in similar entities to address data scarcity. A sequential cross-product KAET (SeqTrans) is proposed to conduct KAET, integrating data preparation and preprocessing, feature selection (FS), feature learning (FL), and transfer learning (TL). The FS and FL modules conduct knowledge extraction and help address various practical challenges such as changing operating conditions and unbalanced datasets. In this paper, sequential TL is introduced to production modelling to conduct knowledge transfer among multiple entities. The first case study of auxetic material performance prediction demonstrates the effectiveness of sequential TL. Compared with conventional TL, sequential TL can achieve the same test mean square errors with 300 fewer training examples when facing data scarcity. In the second case study, balancing anomaly detection models were constructed for two gas turbines in the same series using real-world production data. With SeqTrans, the F1-score of the anomaly detection model of the data-poor engine was improved from 0.769 to 0.909. [ABSTRACT FROM AUTHOR]

Hybrid fuel cell/gas turbine systems provide an efficient means of producing electricity from fossil fuels with ultra low emissions. However, there are many significant challenges involved in integrating the fuel cell with the gas turbine and other components of this type of system. The fuel cell and the gas turbine must maintain efficient operation and electricity production while protecting equipment during perturbations that may occur when the system is connected to the utility grid or in stand-alone mode. This paper presents recent dynamic simulation results from two laboratories focused on developing tools to aid in the design and dynamic analyses of hybrid fuel cell systems. The simulation results present the response of a carbonate fuel cell/gas turbine, or molten carbonate fuel cell/gas turbine, (MCFC/GT) hybrid system to a load demand perturbation. Initial results suggest that creative control strategies will be needed to ensure a flexible system with wide turndown and robust dynamic operation. Paper No. GT2004-53653,

Thermal history sensors are valuable tools for thermal analysis of high-temperature components within aero-engines and gas turbines. However, most thermal history sensors have an upper temperature limit of ∼1200 °C, which is insufficient to meet the requirement of gas turbines. This study introduces a novel material for thermal history sensing capable of measuring temperatures up to 1400 °C. We show thermal history measurements based on the emission intensity ratio of a Eu3+-doped yttrium–aluminum mixture, whose luminescence characteristics undergo irreversible changes when exposed to high temperature. The primary mechanism is the decrease of the symmetry ratio owing to the phase transformation from YAG (Y 3 Al 5 O 12), YAM (Y 4 Al 2 O 9) to YAP (YAlO 3) utilizing the combination reaction of YAP induced by heat-treatment. The intensity ratio between 5D 0 →7F 1 and 5D 0 →7F 2 exhibits a monotonic decrease from 1.3 to 0.4 as the heat-treatment temperature increases from 1000 °C to 1400 °C. Moreover, we demonstrate that the irreversible change in intensity ratio after heat treatment remains insensitive to exposure time and oxygen partial pressure. Thus, the Eu3+-doped yttrium-aluminum mixture is a promising material for manufacturing high-temperature thermal history sensors. [ABSTRACT FROM AUTHOR]

This paper presents an event-triggered sliding mode fault-tolerant control method for networked control systems with actuator faults and external disturbance. First, an event-triggered scheme in the networked control systems is proposed to reduce the number of data transmission. In addition, considering the event-triggering, a sliding mode surface based on the system structure is constructed. Besides, to obtain the controller parameters that meet the H ∞ performance, the bounded real lemma in the form of linear matrix inequality is obtained using the Lyapunov functional. In addition, a sliding mode fault-tolerant control is designed to guarantee that the system can still run stably under the condition of faults and disturbances. Finally, the simulation results of gas turbine system are given to verify the feasibility of the theoretical method. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) are essential for protecting the high-temperature components in gas turbines. However, the durability of TBCs is limited, and new technologies to improve their lifetime are necessary. This study focuses on the pre-oxidation treatment of the NiCoCrAlY bond coat in TBCs to reduce the growth rate of the thermally grown oxide (TGO) and improve the TBC lifetime. The mechanism of the TGO growth rate reduction by the pre-oxidation treatment of NiCoCrAlY was investigated. Oxidation behaviors of the surface of NiCoCrAlY coating samples with or without pre-oxidation treatment were evaluated in air at 800 °C and 900 °C. In-situ X-ray diffraction (XRD) measurements and isothermal oxidation tests were performed. The obtained results revealed that the growth rate of TGO is significantly suppressed by α-Al2O3 layer formed by the pre-oxidation treatment. The generation of γ-Al2O3 and θ-Al2O3, which are typically formed below 900 °C, was significantly reduced by pre-oxidation. It is suggested that this reduction suppresses of the TGO growth. [ABSTRACT FROM AUTHOR]

Addressing burning characteristics of syngas under oxy-combustion conditions in substantially CO 2 -diluted combustion environment for gas turbine combustion applications has rarely been reported. A detailed modeling study was performed over a broad range of syngas compositions at fixed inlet flow velocity of 6 m/s, fixed equivalence ratio of 0.42, and fixed oxygen fraction (OF) of 60% (by vol.). For validating the numerical model, the calculated results were compared against experimental results recorded from the same physical combustion setup. The effects of syngas composition on flow field, laminar flame speed (LFS), flame thickness, adiabatic flame temperature (AFT), combustor power density (PD), thermal power (TP), and species distributions were investigated. Adiabatic flame temperature increased from 2312 to 2388 K, LFS increased from 0.53 to 1.32 m/s, PD reduced from 2854 to 2672 kW/m3, and TP decreased from 4.0 to 3.7 kW when the hydrogen fraction (HF) was changed from 0 to 80%.When the HF was reduced from 90% to 10%, with excluding CH 4 , the AFT increased from 2447 to 2560 K, the LFS decreased from 2.01 to 0.46 m/s, the TP increased from 3.64 to 4.1 kW, and the PD increased from 2620 to 2923 kw/m3. [Display omitted] • Study combustion characteristics of CH 4 /H 2 /CO syngas premixed flames. • Flame speed and temperature and power decreased increased with CO fraction rise. • Increase in H 2 fraction leads to rise in flame speed and temperature but power decreases. • Increase in CH 4 leads to decreases in flame speed and temperature but power increases. • Excluding CH 4 leads to decreases in flame speed and temperature but power increases. [ABSTRACT FROM AUTHOR]

To attain a net zero-carbon emissions energy system, the grid needs dispatchable and flexible power production capable of responding to wind and solar energy variability. Hydrogen-fired gas turbines could play a role in meeting this requirement in the electricity grid; however, research and development are needed to assess the impact of the fuel change on these systems. This study aims to determine the effect of fuel switching on the cycle performance of a typical aero-derivative gas turbine, ranging from 25-35MW when combined with various steam-based bottoming cycles using Aspen Plus thermodynamic simulations. The gas turbine cycle's efficiency and net output power increased by about 2.26% and 5.24%, respectively, when fueled with hydrogen for the constant TIT control strategy compared with the base case. The other two control strategies—constant TOT and heat input—are also positive. The performance of the combined heat and power configurations, expressed by the fuel charged to power, is better for almost all the hydrogen-fired cases compared with the methane case. This implies that using hydrogen as fuel in the gas turbine and duct-firing requires less fuel to produce heat and electricity. Although hydrogen integration into the overall system may pose challenges with auxiliary equipment, storage, supply, and combustion, hydrogen as fuel shows promise in improving the performance of gas turbine combined heat and power units. • Hydrogen for GTs will be an enabler of low-carbon and flexible power production. • Switching to hydrogen enhances power and heat production in all operating strategies. • The GT performance improves with the hydrogen fraction for all operating strategies. • Hydrogen firing increases the operational flexibility of GT-based CHP configurations. [ABSTRACT FROM AUTHOR]

This study explores the transition in combustion technologies from dry micro-mix hydrogen-air to wet micro-mix hydrogen-oxygen configurations. The investigation involves a comprehensive analysis of the combustion processes currently being considered for converting methane gas turbines to methane-hydrogen mixtures and hydrogen, including wet premixed, dry low emission, sequential combustion, and micro-mix, examining key parameters such as efficiency, emissions, and overall performance. Then, the work considers the shift from utilizing air as an oxidizer to oxygen. Wet micro-mix hydrogen-oxygen combustion is then discussed for its impact on combustion dynamics and the potential for achieving zero emissions, cancelling NOx emissions in addition to CO 2 emissions. The findings contribute valuable insights into the feasibility and advantages of transitioning from conventional hydrogen-air combustion to innovative wet hydrogen-oxygen combustion, paving the way for more sustainable and environmentally friendly combustion technologies. Scheme of a hydrogen energy storage system comprising one electrolyser, two tanks for the hydrogen and the oxygen, and an O 2 /H 2 /H 2 O gas turbine power system. The system could be able to receive non-dispatchable electricity and release dispatchable electricity working as a battery but without any limitation on the amount of energy storable, or the time of the storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Rotating machinery like gas turbine engines consist of rotating components like gas turbine disks that are exposed to high thermal loads and stresses due to centrifugal force acting on them, and thus effective cooling is essential. The disks are additionally exposed to hot turbine gas ingress as an adverse pressure gradient is created in the stator-rotor cavity due to outward pumping of near-disk flow. Impingement of a coolant jet on such a surface can effectively provide cooling and also counter this adverse gradient. There also exists a circular relative velocity between the disk and wall-jet formed by impinging air as well as the air in the disk vicinity. Thus, the study of heat transfer under rotating conditions becomes important. With the advent of advanced manufacturing techniques, it is possible to produce disks with novel heat transfer enhancement features such as pin-fins which have not been previously explored. They create unique flow features in addition to increasing the surface area. The present study numerically investigates the heat transfer over rotating surfaces under jet impingement with square, triangular, cylindrical and dome-shaped pin-fins. This will inform the optimization of pin geometry for better heat transfer effectiveness and uniformity. Three different jet Reynolds numbers between 5000 and 18000 based on the jet diameter have been studied for three different Rotational Reynolds numbers based on the disk diameter. Transient non-conjugate heat transfer analysis was conducted, and the technique was compared with experimental results on square pin-fins and a smooth circular disk. The heat transfer enhancement greatly depends on the flow separation and pin area normal to the flow. A heat transfer enhancement of close to 2.2 was observed for triangular fins for the lowest rotation speed, for the highest rotation speed, the highest enhancement of close to 1.7 was observed in the cylindrical pins. [ABSTRACT FROM AUTHOR]

To limit global warming and meet international environmental targets, more environmentally benign technologies must be used in the residential market. Combined Heat and Power (CHP) at the micro-scale (<50 kWe) is seen as one of the best solutions that offers simultaneous generation of both electricity and heat with high overall efficiencies using environmentally friendly fuels (e.g., biofuel, hydrogen, syngas). In this study, four major micro-CHP prime movers (i.e. Micro-gas turbine, Gas engine, Stirling engine, and Fuel cell) have been evaluated in terms of their performance and the currently available technologies and products. The most suitable options for household applications were identified using Political, Economic, Social, Technological, Legal, and Environmental (PESTLE) risk analysis and a Multi-Criteria Decision Analysis (MCDA). Fuel cells display the best environmentally friendly properties despite their price and high start-up time. Gas engines (Reciprocating engines) have the most developed technology with the fastest start-up time and high efficiencies but have vibration and noise issues. Micro-gas turbine micro-CHPs are emerging into the market with relatively cheaper prices, lower maintenance, and good start-up time. Stirling engines are fuel flexible with reasonable prices and available products. Micro-CHP systems, particularly when running on biofuels and hydrogen, provide excellent energy solutions for the future net zero buildings. [ABSTRACT FROM AUTHOR]

In this article, an industrial gas turbine engine with a single spool (single spool 9EA-GT) is discussed, and a thermodynamic model for computing steady-state performance is presented. In addition, a novel component map production method for investigating a gas turbine engine (GTE) is developed for a different compressor and turbine by downloading from the GasTurb 12 tool and scaling to the compressor and turbine's design points. A system of controlling engine flow capacitance by changing inlet guide vanes (IGVs) is presented. Adjusting the controllable IGV blades can optimize all the engine units by continuously correcting the compressor features map. The airflow via the compressor, which in turn controls the airflow throughout the entire system, is managed by IGVs. The computations for steady-state performance involve two models: steady-state behavior at engine startup (from 65% to 100% speed, without load) and steady-state behavior while loading (continuous speed of 100%). In this model, the challenges brought by the lack of understanding of stage-by-stage performance are resolved by building artificial machine maps using suitable scaling methods to generalized maps derived from the previous research and validating them with experimental observations from real power plants. The engine performance simulation utilizing the maps is carried out using MATLAB. Assessment results are found to be in good agreement with the actual performance data. During a steady start, the control system used in this study decreased the fuel consumption, exhaust gas mass flow rate, and compressordriven power for the GTE by 9.5%, 19.3%, and 37.5%, respectively, and those variables decreased by 1%, 12.2%, and 19.7%, respectively, when loading the engine. [ABSTRACT FROM AUTHOR]

Performance adaptation is an effective way to improve the accuracy of gas turbine performance models. Although current performance adaptation methods, such as those using genetic algorithms or evolutionary computation to modify component characteristic maps, are useful for finding good solutions, they are essentially searching methods and suffer from long computation time. This paper presents a novel approach that can achieve good performance adaptation with low time complexity and without using any searching method. In this method, the actual component performance parameters are first estimated using engine measurements at different operating conditions. For each operating condition, some scaling factors are introduced and calculated to indicate the difference between the actual and predicted component performance parameters. Afterward, an interpolating algorithm is adopted to synthesize the scaling factors for modifying all major component maps. The adapted component maps are then able to make the engine model match all the gas path measurements and achieve the required accuracy of the engine performance model. The proposed approach has been tested with a model high-bypass turbofan engine using simulated data. The results show that the proposed performance adaptation approach can effectively improve the model's accuracy. Specifically, the prediction errors can be reduced from about 9% to about 0.6%. In addition, this approach has much less computational complexity compared to other optimization-based counterparts. [ABSTRACT FROM AUTHOR]

In the context of the dual carbon goal strategy, the proportion of new energy generation has increased annually, large‐scale renewable energy integration has been achieved, and the intermittent and uncertain operating characteristics pose an enormous challenge to the complete and stable operation of an integrated energy system (IES), promoting the complexity of IES optimization models. To increase the stability and accuracy of the system and improve the operation efficiency of the system, a Gaussian mixture model is used to fit the probability distribution of wind power and the prediction errors of the photovoltaic output. In addition, the expected maximization method is used to solve a model with hidden variables, the results show that the expectation maximization algorithm can improve the fitting accuracy, reduce the error caused by the subjective setting of the initial value, and make the fitting accuracy of the wind‐solar power prediction error greater. Then, to solve the problem in which the low resolution of the day‐ahead scheduling time leads to large errors, day‐ahead, day‐to‐day multitime scale operation optimization model takes into account the comprehensive demand response according to the differences in wind and solar output and load forecasting accuracy. Finally, simulation validation is conducted in multiple scenarios, and a comparative analysis is performed for single and multitime scale comprehensive demand response scenarios. The simulation results show that compared with the optimization results of no demand response day, the optimization results of this model reduce the total cost by 23.21%, carbon emissions by 13.98%, purchased electricity by 13.87%, and purchased gas by 19.31%, effectively improving the use of gas turbines in the system. The multitime scale scheduling strategy increases the overall operating cost of the IES, modifies the scheduling results, and agrees with real operating scenarios. [ABSTRACT FROM AUTHOR]

This study investigates experimentally and numerically the stability, combustion, and emissions characteristics of premixed swirl-stabilized methane/air flames with enhanced lean blowout (ELBO) injection of hydrogen in the non-premixed mode for higher turndown ratio gas turbines. The study analyzed the effects of hydrogen fraction (HF : volumetric percentage of H 2 in the total fuel) ranging from 0 to 25% and equivalence ratio (φ) ranging from 0.5 to 0.893 on flow/flame interactions and flame stability, structure, and emissions. The introduction of non-premixed H 2 yields two conflicting outcomes, with enhancements in reaction kinetics and flame speed yet counteracted by increased hydrogen jet momentum dispersing the flame. The combustor lean blowout (LBO) limit remains relatively unaffected (φ overall ≈ 0.5) by H 2 injection. Flame temperature is primarily influenced by φ and minorly by HF. Increasing HF resulted in localized temperature rises around H 2 jets without an overall increase in flame temperature, offering a promising strategy for reduction of NOx emissions. Nevertheless, using H 2 as a pilot fuel leads to an increase in intermediate species like OH, H, and O, contributing to flame stabilization. However, this practice also results in higher CO and unburned hydrocarbons emissions due to the inherent characteristics and heightened reactivity of H 2. • Flow/flame/emissions of premixed CH 4 -air flames with enhanced lean blowout H 2 injection. • H 2 injection resulted in counteracting effects of enhanced kinetics and increased momentum. • Lean blowout (LBO) limit remains relatively unaffected (φ overall ≈ 0.5) by H 2 injection. • Non-premixed H 2 injection proves to be an effective strategy for reducing NOx emissions. • Non-premixed H 2 injection resulted in higher CO and unburned hydrocarbons emissions. [ABSTRACT FROM AUTHOR]

The present study proposes a novel method to improve the performance of film cooling. In this type of cooling, due to the presence of counter-rotating vortex pairs downstream of the injection hole, the formed film on the surface tends to detach from the surface. A new geometry is proposed to overcome this vortex pair. In this geometry, the injection passage is equipped with one or more helical ribs. These ribs induce rotation in the injected cooling fluid flow which prevents the separation of the coolant film from the surface. Analysis and optimization of the effective parameters are done including the injection angle, the height, thickness, number, and pitch of the ribs. The results show that by exceeding the injection angle from an optimum value, the mixing tendency of the injected fluid and main flow increases, and the cold fluid film liftoff occurs faster. On the other hand, as this angle decreases, the pressure drop rises. Considering both the heat transfer and pressure drop effects, the best performance is observed at the injection angle of 20°. Moreover, the best performance is achieved for the ribbed passage (of D diameter) with two ribs of 0.025D ​​thickness, 0.1D height, and 0.33D rib pitch. [ABSTRACT FROM AUTHOR]

Thermometry of thermal barrier coatings (TBCs) is essential for designing effective thermal management systems and prolonging the service life of components in aeroengines and gas turbines. However, conducting on-line thermometry in these systems is challenging because it requires physical or optical access to components during operation. A promising alternative is off-line thermometry, in which phosphorescent thermal-history sensors are used to record exposure temperatures after operation. In this study, we synthesized europium (III)-ion-doped barium aluminate (BaAl 2 O 4 :Eu3+) via a solid-state reaction and confirmed its ability to function as a thermal history sensor. Subsequently, we developed a new thermal-sensing strategy based on the self-reduction of Eu3+ to Eu2+ in a BaAl 2 O 4 :Eu3+ phosphor exposed to high temperatures (900–1300 °C) in ambient air. The Eu3+ concentration decreased as the heat exposure temperature increased due to self-reduction of Eu3+ to Eu2+, which irreversibly changed the phosphorescence of BaAl 2 O 4 :Eu3+, i.e., its spectra, the ratio of the phosphorescence intensities of Eu3+ and Eu2+, and the lifetime of Eu3+. As the heat exposure temperature increased, the ratio of the phosphorescence intensities of Eu3+ and Eu2+ monotonically decreased due to self-reduction, whereas the phosphorescence lifetime of Eu3+ initially gradually increased until the heat exposure temperature reached 1000 °C because of the degeneration of concentration quenching, and then decreased as the temperature exceeded 1000 °C because of the degeneration of lattice distortions. This demonstrates that heat exposure temperatures exceeding 1000 °C can be quantitatively evaluated through off-line analysis of Eu3+ and Eu2+ phosphorescence intensity ratios and Eu3+ lifetime at room temperature. Thus, BaAl 2 O 4 :Eu3+, a self-reducing phosphor, is a potential sensor for off-line thermometry of TBCs. [ABSTRACT FROM AUTHOR]

This paper presents a summary of and introduction to research on high-altitude and subatmospheric combustion concerning turbine and scramjet engines. The investigation includes theoretical analysis, experimental studies, and numerical simulations. The analysis encompasses the flow field structure, fuel atomization, and combustion performance. Subsequently, recent research on the combustion performance of liquid fuels, solid fuels, and gaseous fuels under high-altitude and low-pressure plateau environments is reviewed. This includes an evaluation of flame height, flame temperature, combustion rate, fire spread rate, and heat radiation flux. Additionally, combustion performance prediction models for high-altitude environments based on experimental and theoretical analysis have been introduced. Lastly, issues in subatmospheric combustion in the aerospace and plateau fire fields are presented based on the current research. [ABSTRACT FROM AUTHOR]

To meet the requirements of achieving higher efficiency and lower NOx pollution, the flame temperature in gas turbine combustors increases continually; thus, the effusion-cooling technology has been used to ensure the combustor liner remains within the allowed temperature, by which the combustion characteristics and emission behavior are possibly influenced. In order to investigate the effects of dome cooling air flow on combustion characteristics and NOx emissions, three-dimensional combustion simulations for a swirl-stabilized can-type gas turbine combustor are carried out in this work by using the computational fluid dynamics (CFD) method. Through adjusting the ratio of the dome cooling air flow and the dilution cooling air flow, the characteristics of flow field, temperature distribution and NOx emissions under each work condition are analyzed. At different ratios of the dome-cooling air flow to the total air flow, the flow velocity field in the region near the center of the combustion chamber is not changed much, while the velocity field near the chamber wall shows a more significant difference. The temperature in the outer recirculation zone within the combustion chamber is effectively reduced as the dome cooling air flow increases. By analyzing the distribution characteristics of the concentration of OH*, it is demonstrated that the dome cooling air flow does not have a direct effect on the reaction of combustion. It is also found that as the ratio of the dome cooling air flow to the total air flow increases from 0 to 0.15, the value of the NOx emissions drops from 28.4 to 26.3 ppmv, about a 7.4% decrease. The distribution of the NOx generation rate in the combustion chamber does not vary significantly with the increasing dome cooling air flow. Furthermore, by calculating the residence time in different stages, when the the ratio of the dome cooling air flow to the total air flow varies from 0 to 0.15, the residence time in the pilot stage decreases obviously, from 42 ms to 18 ms. This means that reduction in residence time is the main factor in the decrease of NOx emissions when the dome cooling air flow increases. [ABSTRACT FROM AUTHOR]

A high-temperature-resistance single-crystal magnesium oxide (MgO) extrinsic Fabry–Perot (FP) interferometer (EFPI) fiber-optic vibration sensor is proposed and experimentally demonstrated at 1000 °C. Due to the excellent thermal properties (melting point > 2800 °C) and optical properties (transmittance ≥ 90%), MgO is chosen as the ideal material to be placed in the high-temperature testing area. The combination of wet chemical etching and direct bonding is used to construct an all-MgO sensor head, which is favorable to reduce the temperature gradient inside the sensor structure and avoid sensor failure. A temperature decoupling method is proposed to eliminate the cross-sensitivity between temperature and vibration, improving the accuracy of vibration detection. The experimental results show that the sensor is stable at 20–1000 °C and 2–20 g, with a sensitivity of 0.0073 rad (20 °C). The maximum nonlinearity error of the vibration sensor measurement after temperature decoupling is 1.17%. The sensor with a high temperature resistance and outstanding dynamic performance has the potential for applications in testing aero-engines and gas turbine engines. [ABSTRACT FROM AUTHOR]

To modify the structure of thermal barrier coatings and improve their high-temperature resistance, induction plasma spheroidization (IPS) technology was applied to regulate the structure of YSZ powders in this study. The surface morphology, particle size distribution, phase composition, and internal microstructure of the conventional agglomerated and spheroidized powders were characterized using scanning electron microscopy and focused ion beam analysis methods. The results showed that the microstructure of the powders presented uneven evolution in the induction plasma stream. Due to the existence of the temperature gradient along the radial direction of the powders, the IPS powders consisted of outer dense shells and internal porous cores. The mechanical property of such shell–core structure was analyzed by using the finite elemental simulation method. In addition, coatings were prepared using the IPS powders and the agglomerated powders. The IPS coating showed improved water-cooling thermal cycling resistance compared to the conventional coating. [ABSTRACT FROM AUTHOR]

In the paper, the maiden application of Tilted Integral Fractional Derivative with Filter plus Fractional Derivative controller (TIDμ1NDμ2$TI{D^{{\mu _1}}}N{D^{{\mu _2}}}$), called TIFDNFD controller, is proposed to achieve load frequency control (LFC) of two area‐multi source power system. In the study, both areas include thermal power, hydropower, and gas turbine power systems. In this study, generation rate constraint and governor dead‐band are integrated into the power system to evaluate the performance of the controller in a non‐linear environment. The wild horse optimizer (WHO) is used for controller parameter tuning in the LFC problem for the first time. The performance of the proposed controller is demonstrated by comparing it with the recently published studies including different controllers. In this study, to obtain more realistic results, solar photovoltaic (PV) power, wind power, and load demand with stochastic form have been added to the power system. In addition, the dynamic effect of the hydrogen storage system, consisting of an electrolyser and a fuel cell, is considered a grid supporter. The superiority of the WHO algorithm in optimization has been verified by comparing it with three optimization algorithms recently proposed. Finally, the resilience and robustness of the power system are evaluated in perturbed system parameters. [ABSTRACT FROM AUTHOR]

Gas turbines play core roles in clean energy supply and the construction of comprehensive energy systems. The control performance of primary frequency modulation of gas turbines has a great impact on the frequency control of the power grid. However, there are some control difficulties in the primary frequency modulation control of gas turbines, such as the coupling effect of the fuel control loop and speed control loop, slow tracking speed, and so on. To relieve the abovementioned difficulties, a control strategy based on the desired dynamic equation proportional integral (DDE-PI) is proposed in this paper. Based on the parameter stability region, a parameter tuning procedure is summarized. Simulation is carried out to address the ease of use and simplicity of the proposed tuning method. Finally, DDE-PI is applied to the primary frequency modulation system of an MS6001B heavy-duty gas turbine. The simulation results indicate that the gas turbine with the proposed strategy can obtain the best control performance with a strong ability to deal with system uncertainties. The proposed method shows good engineering application potential. [ABSTRACT FROM AUTHOR]

Due to the inherent geometric restrictions of a micro gas turbine (MGT) mixed flow compressor design, diffuser design has a major impact on compressor performance and operating range. Vaned diffusers are often preferred to vaneless diffusers in MGT compressor designs due to better efficiency and pressure recovery, albeit at the expense of operating range. A numeric investigation of the effect of a tandem vane crossover diffuser configuration on the performance and operating range of a MGT mixed flow compressor stage is presented. Three baseline test compressors, covering a wide range of design speeds, mass flow rates and meridional exit angles, are designed with a single vane crossover diffuser. For each of the three baseline compressors, the crossover diffuser design is modified to feature various tandem vane configurations. The tangential shift of the second vane row relative to the first row is evaluated. Additionally, relative first and second vane row lengths are evaluated. The performance (efficiency and pressure ratio) and operating range of the modified diffuser configurations are compared to the baseline configurations. It is shown that a 75% second vane row tangential shift configuration displays the best overall performance, regardless of the relative vane length. It is further shown that an appropriate vane length depends on the design requirement. [ABSTRACT FROM AUTHOR]

Inward flow radial (IFR) supercritical CO2 (sCO2) turbines are smaller in size and operate at considerably higher speeds in comparison to similar capacity conventional gas or steam turbines. The compact size and high speed of IFR turbines result in significant parasitic (leakage and disk friction) losses at the rotor backface. This paper presents CFD investigations to understand the mechanism of parasitic losses of IFR turbines in the kW to MW power scales. The first part of the paper presents a parametric study to quantify the effect of backface flowpath dimensions, rotor inlet radius, and rotational speed on the magnitude of parasitic losses. Subsequently, the paper proposes the implementation of a radial labyrinth seal on the rotor backface to curtail the parasitic losses. The second part of the paper examines how the power scale of the turbine and its design parameters, specific speed and velocity ratio, influence the magnitude of parasitic losses. The investigation reveals that parasitic losses cause an efficiency drop of 8%–15% for 100 kW and 4%–9% for 1 MW IFR sCO2 turbines. In addition, IFR turbines designed for low specific speeds and high velocity ratios result in notably higher parasitic losses, leading to a decline in turbine efficiency. Finally, the paper presents optimal turbine design parameters accounting for the parasitic losses to maximize turbine efficiency. [ABSTRACT FROM AUTHOR]

With ever-increasing demand for high efficiency and high stability gas turbine under the goal of carbon neutrality, the design of L-inlet duct has set stricter demands for low pressure loss and low flow distortion. No general optimization guidelines on both pressure loss and distortion for L-inlet duct were found in open literature. Four geometry parameters including inlet width, inlet length, contraction geometry angle and truncated cone geometry angle are explored for their effects on the trends of pressure loss and flow distortion. Optimization geometry parameters of the L-inlet duct are analysed, and the flow characteristics are thoroughly examined. The flow field characteristic of ΔPt, DC60, SC60 from surrogate model are validated by CFD, the relative errors are 0.37%, −3.92% and 1.75%, respectively. At the design point EF = 35 comparing with original scheme of the L-inlet duct, ΔPt decreases 21.14%, DC60 decreases 45.37%, and SC60 decreases 38.7%. For all off design conditions, the optimization results are better than original scheme. It is estimated that gas turbines can achieve a 0.144% reduction in power loss and a 0.333% improvement in surge margin. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) in gas turbine engines are used in expressly harsh environments; thus, assessing TBC integrity status is critical for safety and reliability. However, traditional periodic maintenance involves visual inspections of the TBCs, requiring the gas turbine to be decommissioned and partially dismantled. Most importantly, tiny defects or internal damages that easily cause coating failure cannot be identified. In this work, a new nondestructive evaluation (NDE) technique of TBCs based on quantum dot (QD) anion exchange is first explored internationally. By exchanging anions between the Cl ions and the CsPbBr3 QDs, the degrees of salt corrosion of the TBCs are evaluated. The resultant NDE technique shows that the colour of the TBCs obviously changes from green to blue, accompanied by a large blueshift (∼ 100 nm) of the photoluminescence (PL) peak position. In addition, the relationship between the PL peak position and coating thermophysical properties indicates that the precision of this NDE technique may easily identify the µm-level of the thermal growth oxide (TGO) changes inside the TBCs. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative approach, Deep Multiscale Soft-Threshold Support Vector Data Description (DMS-SVDD), designed for the detection of anomalies and prediction of faults in heavy-duty gas turbine generator sets (GENSETs). The model combines a support vector data description (SVDD) with a deep autoencoder backbone network framework, integrating a multiscale convolutional neural network (M) and soft-threshold activation network (S) into the Deep-SVDD framework. In comparison with conventional methods, such as One-Class Support Vector Machine (OCSVM) and autoencoder (AE), DMS-SVDD demonstrates improvements in accuracy (by 22.94%), recall (by 32%), F1 score (by 12.02%), and smoothness (by 39.15%). The model excels particularly in feature extraction, denoising, and early fault detection, offering a proactive strategy for maintenance. Furthermore, the DMS-SVDD demonstrated enhanced training efficiency with a reduction in the convergence rounds by 66% and overall training times by 34.13%. The study concludes that DMS-SVDD presents a robust and efficient solution for gas turbine anomaly detection, with practical advantages for decision support in turbine maintenance. Future research could explore additional refinements and applications of the DMS-SVDD model across diverse industrial contexts. [ABSTRACT FROM AUTHOR]

Recently, hydrogen application has been a new and promising technology in gas turbines, paving the way towards a cleaner and more sustainable energy future. However, challenges and considerations accompany this technology due to hydrogen's combustion characteristics compared to traditional fossil fuels. This review presents a comprehensive analysis of recent advancements in hydrogen-fueled gas turbines, focusing on their impacts on gas turbines, economic evaluation, and the development of commercial hydrogen gas turbines. Our analysis demonstrated that the unique combustion characteristics of hydrogen will influence combustion stability, flame dynamics, and the overall combustion process in gas turbines. The challenges associated with commercial hydrogen gas turbines encompass the high cost of hydrogen production, effective and efficient hydrogen combustion, material compatibility, and the imperative need for supportive regulatory measures. • Hydrogen influences combustion stability and the overall performance in gas turbines. • Economic viability of a hydrogen gas turbine depends on various factors. • Test results demonstrate the feasibility of commercial hydrogen gas turbines. • Cost of hydrogen gas turbines is expected to decrease for economies of scale. [ABSTRACT FROM AUTHOR]

Ceramic coatings are widely used in the thermal protection of hot section components of aero-engines, such as turbine blades, turbine casings and combustion chambers. The damage and failure of ceramic coatings have a direct impact on the stability and reliability of hot section components while in operation, and thus have attracted extensive attention. Especially, the size effect of damage of ceramic coatings under thermal loading has to be investigated. This study employs numerical simulation methods to explore the size effect of damage evolution in ceramic coatings with a series of thicknesses under thermal loading. The simulation results show that the transverse cracks, perpendicular to the interface between the coating and the substrate, first initiate inside the ceramic coating, and then propagate toward the outer surface of the ceramic coating and the interface. As the thickness of ceramic coatings increases, the number of transverse cracks decreases, and the interfacial delamination becomes more pronounced. By combining the simulation results of the crack evolution with the mathematical damage model, the relationship between the thickness of the ceramic coating and the damage rate under thermal load is studied. The results indicate that the damage follows a power-law characteristic with an exponent of 0.5, and the damage rate increases with the enhancement of coating thickness. Moreover, the influences of variations in coatings' elastic modulus and the difference in thermal expansion coefficients between the coating and substrate on the initial damage temperature of the coatings are also studied. The results show that doubling the elastic modulus of coatings leads to an average reduction of 43.7 % in the initial damage temperature of the coatings. When the difference in thermal expansion coefficient between the coating and the substrate increases 1.5 times, the average initial damage temperature of the coating reduces 22.3 %. [ABSTRACT FROM AUTHOR]

This study conducts conventional and advanced exergy, exergo-economic, and exergo-environmental analyses and comparisons of two tri-generation systems driven by solid oxide fuel cells (SOFCs) and gas turbines (GTs). The proposed systems mainly consist of SOFC, GT, heat recovery steam generator (HRSG), (organic) Rankine cycle, and heat exchanger. The analysis results indicate that the biggest cost rates of exergy destruction and component in both systems appear in SOFCs being 4.4333 $/h and 4.2760 $/h, while the highest environmental impact rates combined with exergy destruction and component in systems 1 and 2 are found in afterburner and HRSG, which are 645.9569 mPts/h and 849.2659 mPts/h. Compared to the conventional analyses, the advanced analyses demonstrate that air compressors own the largest avoidable-endogenous parts of cost rates, while HRSG of system 1 and steam turbine (ST) of system 2 own the highest avoidable-endogenous parts of environmental impact rates being 165.8482 mPts/h and 115.2299 mPts/h. • Two novel tri-generation systems driven by solid oxide fuel cells are proposed. • Conventional and advanced exergy-based analyses are performed and compared. • The biggest cost rates of exergy destruction and component appear in SOFCs. • The advanced exergo-economic and exergo-environmental factors are improved. [ABSTRACT FROM AUTHOR]

The low flame speed and NO x emissions of ammonia are the key to affecting combustion temperature, stability, flame structure, and pollutant control, limiting its application in power generation devices. This study proposes oxy-ammonia combustion (oxygen content in oxidant = 100%, NH 3 /O 2 combustion) as a novel method for significantly enhancing ammonia combustion. A method for measuring the laminar flame speed using the NH* distribution of the Bunsen burner flame is proposed, and the measured data is close to the constant volume combustion bomb. 21 kinetic models were collected and optimized after comparison with the experimental data of constant volume combustion bombs, and results show that Han et al.'s model has higher prediction accuracy for NH 3 /O 2 flames. The preheating temperature was relevant to gas turbine combustors (298.15–500 K), and the equivalence ratio ranged from 0.7 to 1.6. At this extreme condition (oxygen content in oxidant = 100%), the results show that the maximum laminar flame speed reaches 1.25 m/s at ambient pressure and temperature, which is approximately 18 times that of NH 3 /air combustion, mainly due to the increased reaction rates of OH, H, O and NH 2 radicals in the reaction zone (primary ammonia decomposition and H/O radical pool). The NO emission of NH 3 /O 2 combustion at stoichiometric conditions is about 7216 ppmv@15%O 2 , 1.5 and 13 times that of NH 3 /air and CH 4 /air combustion, respectively. NO production and consumption may follow the N 2 O and NNH mechanism, and HNO is an important precursor for NO formation. Increasing the preheating temperature has less effect on the reaction pathway directions in the reaction network of nitrogen conversion but affects the path flux significantly. [Display omitted] • Oxy-fuel combustion enhances the ammonia combustion to "m/s" level. • Active radical pools and ammonia primary decomposition determine flame speeds. • N 2 O–NNH mechanism dominates nitric oxide production and consumption. • Preheating and fuel-lean conditions promote ammonia primary decomposition. • HNO is the dominant precursor of nitric oxide and competes with NH radicals. [ABSTRACT FROM AUTHOR]

In the high-temperature mainstream of gas turbines, there is a rim clearance between the rotor and the stator. A rim seal is to prevent the intrusion of high-temperature gas by spraying cool fluid from the inside of the rim clearance to the outside. In the past research on rim seals, the focus was on the overall performance of the sealing structure, and the flow in the disc cavity was studied more, but the high-radius flow was simplified. In recent years, additional research in the field has focused on more complex sealing structures and high-radius flows, such as the interface between the disk cavity and the mainstream. There is more work to be conducted in this area of research. In this paper, the unsteady numerical simulation of the flow in four different rim sealing geometries is carried out by the URANS method. The flow phenomena and the influence of geometry on the flow are studied. The numerical simulation results are validated with the experimental results. It is found that the fluid in the rim sealing obviously presents two distinct forms and confrontations according to the tangential velocity. The flow in the sealing structure presents obvious circumferential non-uniformity. Compared with the single-axial structure, in the single-radial structure, the mixing area is induced by the radial geometry, and more vortex structures are generated, the mixing process is more intense, and the sealing effect is better. In the double-sealing structure, the inner structure plays the role of a barrier, and the cavity geometry between the two layers has a major influence on the sealing performance. [ABSTRACT FROM AUTHOR]

In this research, an annular combustion chamber with swirlers is introduced in a micro-gas turbine engine for power production. The impact of the dilution holes position and swirler vane angles on the performance of the combustion chamber is investigated. Furthermore, optimization of the combustion chamber is carried out to accommodate a multi-fuel blend, incorporating pure methane, natural gas, and ethanol. The combustor is designed in SolidWorks, and simulations are performed in Ansys Fluent for two positions of dilution holes in the liner and swirler blade angles. The model used is non-premixed with a compressible k–ε turbulent flow model and an equilibrium probability density function for the chemical reaction. To measure the performance of the combustion chamber, pollutant emissions, combustion efficiency, and outlet temperature are examined. Pollutant emissions such as carbon monoxide and unburned fuels exist in a small amount; however, nitric oxides are negligible. The combustion efficiency found is above 98% for methane and natural gas, and almost 100% for ethanol. Moreover, simulation results reveal that the swirler vane angle of 45° widely improves combustor performance. [ABSTRACT FROM AUTHOR]

Combustion instabilities in annular systems raise fundamental issues that are also of practical importance to aircraft engines and ground-based gas turbine combustors. Recent studies indicate that the injector plays a significant role in the stability of combustors by defining the flame dynamical response and setting the inlet impedance of the system. The present investigation examines the effects of combinations of injectors of two different types ($U$ and $S$) on thermoacoustic instabilities in a laboratory-scale annular combustor and compares different circumferential staging strategies. The combustor operates in a stable fashion when all injection units belong to the $S$ -family, but exhibits large amplitude pressure oscillations when all these units are of the $U$ -type. When the system comprises a mix of $U$ - and $S$ -injectors, it is possible to determine the number of $S$ -injectors leading to stable operation. For a fixed proportion of $U$ - and $S$ -injectors, some arrangements give rise to stable operation while others do not. Results also show that introducing symmetry-breaking elements affects the system's modal dynamics. These experimental observations are interpreted in an acoustic energy balance framework used to derive an expression for the growth rate as a function of the describing functions of the flames formed by the different injectors and their respective azimuthal locations. Growth rates are determined for the different configurations and used to explain the various observations, estimate the system damping rate and predict the location of the nodal line when the standing mode prevails. [ABSTRACT FROM AUTHOR]

In this study, the implementation of a solid oxide fuel cell–gas turbine hybrid engine for primary propulsion and electric power generation in aircraft is investigated. The following three parameters, which are crucial in attaining optimal performance at any point in the flight profile, were identified: the oxygen-to-carbon ratio of the catalytic partial oxidation reformer, the fuel utilization factor of the fuel cell, and the airflow split ratio at the outlet of the high-pressure compressor. The study assesses the impact of varying these parameters within specified ranges on the performance of the hybrid system. At the design point, the system yielded a total power output of 1.96 MW, with 102.5 kW of electric power coming from the fuel cell and 7.9 kN (1.86 MW) of thrust power coming from the gas turbine. The results indicate that varying the oxygen-to-carbon ratio affected the fuel cell's fuel utilization and resulted in a slight decrease in gas turbine thrust. The fuel utilization factor primarily affected the power output of the fuel cell stack, with a minor impact on thrust. Notably, varying the airflow split ratio showed the most significant influence on the overall system performance. This analysis provides insights into the system's sensitivities and contributes to the development of more sustainable aircraft energy systems. [ABSTRACT FROM AUTHOR]

A kinetic theory, known as the Langmuir–Hinshelwood–Hougen–Watson adsorption model, is applied to describe the steam methane reforming (SMR) in a 500 kW scale micro chemically recuperated gas turbine (CRGT) cycle. The response surface models of important performance parameters, including the methane conversion, carbon monoxide selectivity, and chemically recuperated heat as a function of the temperature, pressure, steam-to-carbon ratio, and contact time are numerically obtained based on the cases selected by the central composite design. The factors affecting the SMR performance are analyzed, and the reformer performance is optimized using both the desirability function combined with the response surface methodology and the second generation non-dominated sorting genetic algorithm. Finally, performance of the optimized reformer and electrical efficiency of the micro CRGT cycle with the reformer are evaluated. Results reveal that the efficiency of the micro CRGT is 40.70%, which is much higher than the typical high-efficiency micro gas trubine without reformer. [Display omitted] • Steam methane reforming kinetics in micro chemically recuperated gas turbine. • Analyses of factors affecting reforming performance using response surface method. • Reformer optimizing by desirability function combined with response surface method. • Reformer optimizing by a second generation non-dominated sorting genetic algorithm. • Micro gas turbine cycle with the optimized reformer has an efficiency of 40.70%. [ABSTRACT FROM AUTHOR]

The aerodynamic noise of pipelines is an important part of the noise of a ship's system. This paper conducted numerical investigations on the flow and acoustic characteristics of the marine gas turbine exhaust system. The near-field and far-field acoustic characteristics of the internal flow noise of the exhaust system are calculated by employing the Möhring's sound analogy method. In addition, the far-field acoustic characteristics of the external jet flow noise of the exhaust system are calculated by employing the stochastic noise generation and radiation (SNGR) method. Two kinds of protrusions are added to the main nozzle outlet to achieve noise reduction. The internal sound field of the marine exhaust system is dominated by low frequency sound sources, which are more obvious as the exhaust mass flow rate decreases. As for the external sound field of the marine exhaust system, the peak frequency of the far-field noise spectrum decreases with the decrease in the exhaust mass flow rate. The eight periodic protrusions perform better in reducing the internal aerodynamic noise of the exhaust system, while the five aperiodic protrusions perform better in reducing the external jet noise of the exhaust system. [ABSTRACT FROM AUTHOR]

An advanced material known as structurally graded material has composition and structure that gradually alters or changes the quality of material in tandem. Various materials could be used with this idea for structural and practical purpose. By offering practical and affordable solutions for design validation, product prototype, and production of high‐performance functional components, fused deposition modelling, a highly regarded three‐dimensional printing technique, has sparked the industrial advancements. Fiber reinforced polymer (polylactic acid‐based composites) are replacing traditional thermosetting polymers and steel as alternative materials. The aircraft industry and energy industry (gas turbines, structural re‐entry thermal production) both frequently utilize ceramic reinforced polymer. In these applications, ceramic reinforced polymer components must be permanently or temporarily adhered to the surrounding materials. Here, in this research work structurally graded wall is fabricated using carbon fiber reinforced polymer and ceramic reinforced polymer through fused deposition modelling process. This research work for creation of structurally graded material architecture was inspired by idea of merging seemingly incompatible functionalities such as the toughness of carbon fiber reinforced polymer and refractoriness of ceramic reinforced polymer with the relaxing of defects. [ABSTRACT FROM AUTHOR]

Second-stage gas turbine nozzles are an important part of the gas turbine due to their performance in hot temperature conditions. In this investigation, service-induced failure analysis and microstructural variations of different sides of a second-stage nozzle in a 100 MW gas turbine made of FSX-414 cobalt-based alloy were comprehensively studied to determine the conditions and mechanisms of the failure process. The primary carbides M3C2 and M7C3 types were converted to secondary carbides M23C6 type by phase transformation process and formed a continuous layer in the grain boundaries owing to high-temperature operation conditions. A network of cracks was created in the grain boundaries, leading to a fracture in the vane of the nozzle. The continuity and density of the produced carbides decreased ductility and toughness of the nozzle. The results demonstrated that hot oxidation and sulfidation occurred in the leading-edge zone. The aggregation and asymmetry of the combustion line and, consequently, the increasing temperature were the reasons for the damage. Some macrocracks were observed by visual inspection on the surface of the nozzle owing to exposure to high temperatures and placement in the path of the hot gas with high pressure. Based on the results, the continuous and coarse brittle M23C6 carbides on the grain boundaries were the major cause of the failure due to the crack growth caused by stress corrosion. These carbides provided appropriate paths for the growth of the crack through grain boundaries, leading to failure after the operational out-of-service condition of a second-stage gas turbine nozzle. Operational in over-hot conditions and an inappropriate filtration system were the main reasons for the operational-induced thermal fatigue failure process of the second-stage gas turbine nozzles. Based on the results, oxidation and microstructural variations were the main causes of the failure process of the second-stage gas turbine nozzles. [ABSTRACT FROM AUTHOR]

The effects of fuel blends comprising ammonia and hydrogen on the technical, economic, and environmental indicators of an existing gas turbine unit with 7.6 MW output power were investigated and analyzed. Four models, each with different fuel-blending options, were designed by Aspen HYSYS and Ansys®Chemkin Pro to analyze the technical and chemical processes. Based on the technical and CO 2 emission values of each model developed in Aspen HYSYS, the focus was on Scenario 4 with ammonia and hydrogen co-firing. This scenario exhibited the highest electric efficiency and the lowest CO 2 emissions but had higher costs for generated electricity compared to other scenarios. Economic evaluations of all scenarios provided a clear understanding of each fuel cost and Levelized Cost of Electricity (LCOE). Initially, scenario 2, with ammonia co-firing, appeared to be an attractive option for further implementation. However, detailed analyses of the combustion process in each model dramatically changed the final decision and provided a good reason to focus on hydrogen fuel, which significantly reduced NOx emissions. In conclusion, Scenario 3 with hydrogen co-firing demonstrated attractive performance and favorable combustion kinetics. [Display omitted] • Performance of operating gas turbine with natural gas, NH 3 , and H 2 blends is investigated. • NOx emissions under H 2 and natural gas blend are within the requirements. • Natural gas, NH 3 , and H 2 blends enhance the performance of the cycle but costly and emit more NOx. • Hydrogen combustion remained the strongest alternative to natural gas. [ABSTRACT FROM AUTHOR]

This study experimentally investigates stability, near flashback dynamics, and NOx emissions arising from H 2 /N 2 flames in a micromixer-based burner for gas turbine combustion applications. Generalized stability maps were generated and NOx emissions and temperature profiles were recorded. Two distinct flashback modes are revealed at each hydrogen fraction (HF) , with intense audible loud noise (dynamic instabilities) during flashback mode 1, followed by the actual flashback (flashback mode 2) occurrence. Shorter combustors are needed for more stable H 2 flames. The onset of acoustic perturbations (flashback mode 1) is observed to occur consistently at a constant adiabatic flame temperature (AFT) of ∼1800 K. A uniform temperature profile, a smaller profile factor (PF), is reported at the different HFs. The lean cold combustion conditions minimized NOx emissions to the single-digit ppm level despite rising the AFT. [Display omitted] • Stability, dynamics, and NOx emissions of H 2 /N 2 /Air flames in a micromixer combustor. • Shorter combustors are needed to host stable H 2 flames compared to natural gas flames. • The onset of flashback mode 1 was observed to occur at a constant AFT of ∼1800 K. • A uniform temperature profile, smaller profile factor (PF), is reported at the different HFs. • The lean cold combustion minimized NOx to the single-digit ppm level despite the AFT. [ABSTRACT FROM AUTHOR]

The effect of centerbody heating by the flame on flashback propensity is experimentally investigated. The burner is technically premixed with 100% hydrogen as fuel under atmospheric pressure. The centerbody temperature was monitored by thermocouples revealing a thermal runaway of the centerbody temperature at the onset of flashback. Post-processed OH*-chemiluminescence imaging data of the flame show an increase in OH*-chemiluminescence intensity during thermal runaway indicating either less quenching or auto-ignition events of hydrogen/air mixtures being in contact with the heated centerbody surface. The authors recorded the formation of an auto-ignited flame kernel upstream of the flame front. An analytical model involving an auto-ignition Damköhler number D a A I , the Reynolds number R e and the normalized burner pressure drop Δ p b u r / Δ p b u r r e f is introduced predicting whether thermal runaway takes place under certain operating conditions. Experimental data from two different burners are applied to the model's safety map and good agreement is found. • A flame attached to the centerbody can lead to thermal runaway. • Auto-ignition is the dominant flashback mechanism if thermal runaway occurs. • A Damköhler model has been developed predicting whether thermal runaway takes place. [ABSTRACT FROM AUTHOR]

Environmental barrier coatings (EBCs) are necessary for use of SiC/SiC ceramic matrix composites (CMCs) in gas turbine engines. Due to the complex operational environments, it is increasingly important to understand the interplay of damage modes to project the durability of the EBC/CMC system. Two life-limiting failure mechanisms of EBCs are steam oxidation and molten calcium-magnesium-aluminosilicate (CMAS) attack. Steam oxidation results in the formation of a thermally grown oxide (TGO) that acts as a weak interface and CMAS/EBC interactions cause thermomechanical and thermochemical changes that compromise coating integrity. EBCs consisting of a Yb 2 Si 2 O 7 topcoat and a silicon bond coat were subjected to low (2 mg/cm2) loadings of two CMAS compositions prior to steam oxidation at 1316 °C for up to 300 h. Exposure to CMAS reduced the TGO thickness and the low CaO content glass resulted in the thinnest oxide scales. However, glass exposure had mechanical consequences that caused premature coating delamination. [ABSTRACT FROM AUTHOR]

The Helmholtz method is developed to predict the self-excited thermoacoustic instabilities in a gas turbine combustor, combining flame describing functions, the measured damping rates under the firing condition, and the non-uniform spatial distributions of the physical parameters. The impact of the hydrodynamic and geometrical parameters on the thermoacoustic instabilities is investigated. The measured damping rates show lower values under a hot condition compared with those in a cold state. The experimental results indicate that the relative errors of the predicted eigenfrequencies and the velocity fluctuation levels are below 10%. The pressure amplitude decreases and the phase increases in the axial direction, indicating a typical 1/4-wavelengh mode. At a higher equivalence ratio, the mode shape in the axial direction becomes steeper due to the elevated fluctuation amplitude at the pressure antinode after enhancing the thermal power. When the air flow rate increases, the discrepancies between the pressure shape on the flame tube side and that on the plenum side are reduced. The velocity fluctuation level increases as the combustor length increases at a constant damping rate. In fact, the velocity fluctuation level first increases and then declines, caused by more significant damping rates when employing longer flame tubes. Self-excited thermoacoustic instabilities can be well predicted using the proposed method. [ABSTRACT FROM AUTHOR]

In this study, large eddy simulation (LES) was used to investigate the dynamic characteristics of diffusion flames in a swirl combustion chamber at an oxygen content of 11–23 wt% and temperature of 770 K. The proper orthogonal decomposition (POD) method was employed to obtain flame dynamic modes. The results indicate that oxygen content has a significant impact on the downstream flow and flame combustion characteristics of the swirl combustion chamber. With oxygen content increasing, the size of the recirculation zone is reduced, and the flame field fluctuations are intensified. The pressure and heat release fluctuations under different oxygen contents were analyzed using frequency spectrum analysis. Finally, the flame modes were analyzed using the POD method, and it was found that the coherent structures are asymmetric relative to the local coordinate system. At an oxygen content of 11 wt%, they exhibit larger coherent structures, while at an oxygen content of 23 wt%, they exhibit numerous turbulent structures. [ABSTRACT FROM AUTHOR]

Given the increasing role of computational fluid dynamics (CFD) simulations in the aerothermal design of gas turbine vanes and blades, their rigorous validation is becoming more and more important. This article exploits an experimental database obtained by the von Karman Institute (VKI) for Fluid Dynamics for the LS-94 test case. This represents a film-cooled transonic turbine vane, investigated in a five-vane linear cascade configuration under engine-like conditions in terms of the Reynolds number and Mach number. The experimental characterization included inlet freestream turbulence measured with hot-wire anemometry, aerodynamic performance assessed with a three-hole pressure probe in the downstream section, and vane convective heat transfer coefficient distribution determined with thin-film thermometers. The test matrix included cases without any film-cooling injection, pressure-side injection, and suction-side injection. The CFD simulations were carried out in Ansys Fluent, considering the impact of mesh sizing and steady-state Reynolds-Averaged Navier-Stokes (RANS) transition modelling, as well as more accurate transient scale-resolving simulations. This work provides insight into the advantages and drawbacks of such approaches for gas turbine hot-gas path designers. [ABSTRACT FROM AUTHOR]

Data from the steady-state operation of gas turbine engines are used in gas path diagnostic procedures. A method to identify steady-state operation is thus required. This paper initially explains and demonstrates the factors that cause a deviation in engine health when transient data are used for diagnosis and shows that there is a threshold in the slope of time traces, below which the variation in engine health parameters is acceptable. A methodology for deriving a criterion for steady-state operation based on actual flight data is then presented. The slope of the exhaust gas temperature variation with time and the size of its time-series window, from which this slope is determined, are the required parameters that must be specified when applying this criterion. It is found that the values of these parameters must be selected so that a sufficient number of steady-state points are available without compromising the accuracy of the diagnostic procedure. [ABSTRACT FROM AUTHOR]