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The hydrogen fuel free-piston engine (FPE) is an ideal onboard power device for new energy vehicles due to its multiple advantages, including better fuel adaptability. However, the periodic cyclic variations of FPE pose a significant challenge in controlling its stable operation. To address this issue, a secondary fuel injection (SFI) control strategy based on the inner dead center (IDC) has been designed. It categorizes and manages IDC by exploring the relationship between different positions of IDC and IMEP. The controller calculates the SFI quantity to control the IMEP and reduce cycle fluctuations effectively based on the classification results and the difference between the current IMEP and the target value. In practice, a rapid simulation combustion control model based on the prototype was established to validate the effectiveness of the control strategy. After implementing active control, IMEP achieved the step response to the target value in just one cycle instantaneously, and the variation range stabilized from 0.3 bar to 0.1 bar. The degree of fluctuation in the PV curve of FPE significantly decreases before and after control, indicating more stable FPE operation. The results demonstrate that this control strategy can effectively achieve precise IMEP control and reduce cycle variations. This means a more reliable and efficient operation of hydrogen fuel FPEs in new energy vehicles, enhancing their performance and viability. • An in-cycle controlled secondary fuel injection control strategy to reduce cycle variations was designed. • The mathematical model of single cylinder free-piston engine based on the prototype was established. • The required secondary injection volume can be calculated based on the initial injection and the inner dead center. • The secondary fuel injection control strategy can instantly achieve step response and stabilize near the set point. • The stability of free-piston engine operation under two control methods, PID and secondary fuel injection, was compared. [ABSTRACT FROM AUTHOR]

The dynamics of rotating hydrodynamic systems containing phase inclusions are interesting due to the related widespread occurrence in nature and technology. The influence of external force fields on rotating systems can be used to control the dynamics of inclusions of various types. Controlling inclusions is of current interest for space technologies. In low gravity, even a slight vibration effect can lead to the appearance of a force acting on phase inclusions near a solid boundary. When vibrations are applied to multiphase hydrodynamic systems, the oscillating body intensively interacts with the fluid and introduces changes in the related flow structure. Asymmetries in the fluid flow lead to the appearance of an averaged force. As a result, the body is repelled from the cavity boundary and takes a position at a certain distance from it. The vibrationally-induced movement of phase inclusions in liquids can be used to improve various technological processes (for example, when degassing and cleaning liquids from solid inclusions, mixing various components, etc.). This study presents a relevant methodology to study the averaged vibrational force acting on a pair of free cylindrical bodies near the oscillating wall of a cavity. Attention is paid to the region of moderate and low dimensionless frequencies when the size of the inclusion is consistent with the thickness of the Stokes boundary layer. The dynamics of these bodies is considered in a horizontal cylindrical cavity with a fluid undergoing modulated rotation. The average lift force of a vibrational nature is measured by the method of quasi-stationary suspension of bodies whose density differs from the density of the liquid in a static centrifugal force field. The developed technique makes it possible to determine the dependence of the lift force on vibration parameters and the distance from the oscillating boundary at which solid inclusions are located. It is shown that in the region of moderate dimensionless frequencies, the average lift force acting on an inclusion near the boundary undergoing modulated rotation almost linearly depends on the dimensionless frequency. [ABSTRACT FROM AUTHOR]

The engine in-cylinder pressure is a very important parameter for the optimization of internal combustion engines. This paper proposes an alternative recursive Kalman filter-based engine cylinder pressure reconstruction approach using sensor-fused engine speed. In the proposed approach, the fused engine speed is first obtained using the centralized sensor fusion technique, which synthesizes the information from the engine vibration sensor and engine flywheel angular speed sensor. Afterwards, with the fused speed, the engine cylinder pressure signal can be reconstructed by inverse filtering of the engine structural vibration signal. The cylinder pressure reconstruction results of the proposed approach are validated by two combustion indicators, which are pressure peak P max and peak location P loc . Meanwhile, the reconstruction results are compared with the results obtained by the cylinder pressure reconstruction approach using the calculated engine speed. The results of sensor fusion can indicate that the fused speed is smoother when the vibration signal is trusted more. Furthermore, the cylinder pressure reconstruction results can display the relationship between the sensor-fused speed and the cylinder pressure reconstruction accuracy, and with more belief in the vibration signal, the reconstructed results will become better. [ABSTRACT FROM AUTHOR]

Methanol is favored for its excellent physicochemical properties, becoming an ideal alternative fuel for engines. Adopting a dual-fuel injection mode of methanol port injection and gasoline direct injection (MPI + GDI) allows for more flexible injection strategies, enhancing the engine's power, efficiency, and emission performance. However, observing the processes of fuel injection, atomization, mixing, flow, and combustion in real engine cylinders is challenging, and controlling the fuel–air distribution and turbulence before engine ignition is difficult. Therefore, after validating the simulation model through optical engine bench experiments, this study investigated the performance and emission characteristics of MPI + GDI engines under various injection strategies. The results indicate that delaying the GDI injection timing decreases the uniformity of the fuel–air mixture and reduces cylinder pressure, corresponding to a retarded crank angle. Increasing GDI injection pressure enhances the fuel–air mixing, especially when the injection timing is later. Employing secondary injection and increasing the proportion of the second injection lead to poorer fuel–air uniformity in the cylinder, a decrease in peak pressure value, reduced nitrogen oxides (NOx) emissions, and a gradual increase in carbon monoxide (CO) and total hydrocarbons (THC). [ABSTRACT FROM AUTHOR]

Thanks to the distinctive morphology of graphite particles in its microstructure, compacted graphite iron (CGI) exhibits excellent thermal conductivity together with high strength and durability. CGI is extensively used in many applications, e.g., engine cylinder heads and brakes. The structural integrity of such metal-matrix materials is controlled by the generation and growth of microcracks. Although the effects of the volume fraction and morphology of graphite inclusions on the tensile response of CGI were investigated in recent years, their influence on crack initiation is still unknown. Experimental studies of crack initiation require a considerable amount of time and resources due to the highly complicated geometries of graphite inclusions scattered throughout the metallic matrix. Therefore, developing a 2D computational framework for CGI with a random microstructure capable of predicting the crack initiation and path is desirable. In this work, an integrated numerical model is developed for the analysis of the effects of volume fraction and nodularity on the mechanical properties of CGI as well as its damage and failure behaviours. Finite-element models of random microstructure are generated using an in-house Python script. The determination of spacings between a graphite inclusion and its four adjacent particles is performed with a plugin, written in Java and implemented in ImageJ. To analyse the orientation effect of inclusions, a statistical analysis is implemented for representative elements in this research. Further, Johnson–Cook damage criteria are used to predict crack initiation in the developed models. The numerical simulations are validated with conventional tensile-test data. The created models can support the understanding of the fracture behaviour of CGI under mechanical load, and the proposed approach can be utilised to design metal-matrix composites with optimised mechanical properties and performance. [ABSTRACT FROM AUTHOR]

Ammonia is emerging as a promising alternative fuel for longer range decarbonised heavy transport, particularly in the marine sector due to highly favourable characteristics as an effective hydrogen carrier. This is despite generally unfavourable combustion and toxicity attributes, restricting end use to applications where robust health and safety protocols can be upheld. In the currently reported work, a spark ignited thermodynamic single cylinder research engine equipped with gasoline direct injection was upgraded to include gaseous ammonia port injection fuelling, with the aim of understanding maximum viable ammonia substitution ratios across the speed load operating map. The work was conducted under overall stoichiometric conditions with the spark timing re-optimised for maximum brake torque at all stable logged sites. The experiments included industry standard measurements of combustion, performance and engine-out emissions (including ammonia 'slip'). With a geometric compression ratio of 12.4:1, it was possible to run the engine on pure ammonia at low engine speeds (1000-1800 rpm) at low to moderate engine loads in a fully warmed up state. When progressively dropping down below a threshold load limit, an increasing amount of gasoline co-firing was required to avoid engine misfire. Due to the favourable antiknock characteristics, pure ammonia operation was up to 5% more efficient than pure gasoline operation under stable operating regions. A maximum net indicated thermal efficiency (ITE) of 40% was achieved, with efficiency tending to increase with speed and load. For the co-fuelling of gasoline and ammonia in a pure ammonia attainable operating region, it was found that addition of gasoline improved the combustion, but these improvements were not sufficient to translate into improved thermal efficiency. Emissions of ammonia slip reduced with increased gasoline co-fuelling, albeit with increased NOx. However, the reduction in ammonia slip was nearly ten times the increase in NOx emissions. Comparing pure ammonia and pure gasoline operation, NOx reduced by ~60% when switching from pure gasoline to pure ammonia (as the latter is associated with longer and cooler combustion). Results were finally compared to those obtained a modern multicylinder Volvo 'D8' turbo-diesel engine modified for dual-fuel operation with ammonia port fuel injection (PFI), with the focus of the comparison being ammonia slip and NOx emissions. [ABSTRACT FROM AUTHOR]

he thermodynamics of in-cylinder processes of the internal combustion engine in cranking mode when measuring compression were examined. Analysis of various theoretical models and comparison of known data showed that the problems of constructing mathematical models of the engine operating cycle remain unresolved. The vast majority of practical data and recommendations for measuring cylinder compression are based on empirical knowledge, numerous experiments, and tests. In accordance with this, there is a need for computational models of the compression measurement process and their theoretical justification. To solve the identified problems, a mathematical model of the thermodynamic processes in the cylinder was developed. Unlike existing ones, the model describes the processes in the cylinder step by step, taking into account the real nature of the intake-exhaust processes, air leakage through the interfaces of parts, and heat exchange with the walls. Using modeling, the main patterns of changes in compression depending on the modes, the nature of damage to the associated parts of the valve mechanism and cylinder-piston group, the amount of leakage, and engine temperature were found. Based on the results of the study, the properties of the model which make its use effective in diagnosing and monitoring the technical condition of engines in operation were concluded. [ABSTRACT FROM AUTHOR]

Aiming at the problem of torque fluctuations and intake pressure fluctuations caused by cycle cylinder deactivation, we introduced a refined control strategy encompassing fixed cycle frequency with fixed deactivation frequency, variable cycle frequency with fixed deactivation frequency, and variable cycle frequency with variable deactivation frequency. The cycle cylinder deactivation rate is determined by controlling the cycle frequency and the cylinder deactivation frequency, which provides a new method for exploring the torque fluctuation of the cycle cylinder deactivation. Furthermore, we introduced an intake compensation method based on the cylinder deactivation compensation coordinate system is proposed. The non-uniformity of the intake air volume of each cylinder of the cycle cylinder deactivation is improved by changing the valve lift. After compensation, the non-uniformity of the intake air volume and the mean indicated pressure of each cylinder are within 2%, and the maximum torque fluctuation is reduced by 52%. It provides a useful reference for enhancing the dynamic smoothness of cylinder deactivation in engines. [ABSTRACT FROM AUTHOR]

This study used the two-dimensional particle image velocimetry technique to quantify the in-cylinder horizontal plane velocity field evolution in a swirl-supported light-duty single-cylinder diesel engine. The data were acquired at a constant engine speed of 1600 revolutions per minute. For each case, the distance of the laser sheet from the fire deck was varied (z = 5, 10, and 20 mm) to investigate the axial variations in the flow field during the flow evolution in the compression stroke. A vortex identification algorithm was used to detect the swirl center and its deviation from the rigid body rotation. A Bessel fit was obtained using the experimental data. The result revealed that the in-cylinder flow was not axisymmetric. The swirl center approached the geometrical center as the piston approached the top dead center. The flow evolved at the farthest plane from the fire deck. The axial diffusion of angular momentum resulted in the formation of the swirl flow structure in the plane closer to the fire deck. Angular momentum analysis of a simplified geometry has been presented to explain the swirl amplification. The estimated results were compared with the experimental results to show the momentum stratification in the engine cylinder later in the compression stroke. [ABSTRACT FROM AUTHOR]

Although homogeneous charge compression ignition (HCCI) diesel engines are the favored source of power with near zero oxides of nitrogen (NOx) and particulate matter emissions owing to a higher degree of homogeneity and elimination of diffusion phase combustion, the main drawback is the uncontrolled start of combustion along with high CO and unburned hydrocarbon emissions. In the present work, experimental investigations were carried out on a single cylinder diesel engine operating in HCCI combustion mode using external air-fuel mixture preparation. The regulated percentage of steam is added inside the mixing chamber and the effects on the combustion, performance and emission characteristics were reported for various steam injection rates at different brake mean effective pressures. The results obtained show that the brake thermal efficiency was improved to 21.048% with the addition of 20% steam addition and the NOx emissions were also reduced significantly. The emissions of CO and unburned hydrocarbon were found 0.7% and 93 ppmrespectively at the steam addition rate of 20%, however a rapid increase was observed if the steam injection rate was increased further. Overall, the present work shows that by the addition of steam, the CO and unburned hydrocarbon emissions can be reduced significantly along with NOx emissions and also there is a greater potential to control the start of combustion. [ABSTRACT FROM AUTHOR]

Al-Si-Cu-Mg alloys are among the most significant types of aluminum alloys, accounting for 85–90% of all castings used in the automotive sector. These alloys are used, for example, in the manufacturing of engine blocks and cylinder heads due to their excellent specific strength (ratio of strength to specific weight) and superior castability and thermal conductivity. This study investigated the effect of using Zr as an alternative grain refiner in the novel AlSi5Cu2Mg cylinder head alloy. The microstructure of this alloy could not be refined via common Al-Ti-B grain refiners due to its specifically designed chemical composition, which limits the maximum Ti content to 0.03 wt.%. The results showed that the addition of Zr via the AlZr20 master alloy led to a gradual increase in the solidus temperature and to the grain refinement of the microstructure with the addition of as little as 0.05 wt.% Zr. The addition of more Zr (0.10, 0.15, and 0.20 wt.%) led to a gradual grain refinement effect for the alloy. The presence of Zr in the AlSi5Cu2Mg alloy was reflected in the formation of Zr-rich intermetallic phases with acicular morphology. Such phases acted as potent nucleants for the α-Al grain. [ABSTRACT FROM AUTHOR]

Internal combustion engines have played a crucial role in the advancement of society. Consequently, there has been a persistent need to enhance their efficiency and performance. The water-injected six-stroke engine is based on conventional four-stroke engines, producing additional power by injecting water into the hot combustion products during the expansion stroke, thereby increasing the overall engine efficiency. However, a comprehensive review that consolidates existing knowledge and identifies future research opportunities in six-stroke engine technology is lacking. This study addresses this gap by thoroughly examining the thermodynamic operation of six-stroke engines and analyzing the impact of water injection on engine performance. The review covers literature from 1994 to 2023, categorizing studies based on the modeling approach, working fluid, thermodynamic cycle, and consideration of heat transfer. Among the 18 analyzed articles, predominantly published from 2015 to 2019, half utilize analytical models, while the rest employ experimental models addressing heat transfer losses. Notably, water injection exhibits a substantial influence, manifesting as a 5.18% increase in brake power and a 1.55% enhancement in thermal efficiency, particularly with acetylene as the working fluid. Finally, a literature overview of water injection in hot gas environments within the engine cylinder was conducted in addition to a preliminary thermodynamic analysis of the Otto and Diesel cycles to compare different configurations outlined in the literature. The lack of studies, experimental setups, and non-idealized models that consider factors such as heat transfer or water evaporation during injection is evident. By critically synthesizing the available literature, this study offers valuable insights into the potential advantages, limitations, and prospects of six-stroke engine studies. [ABSTRACT FROM AUTHOR]

To evaluate the rationality of the cooling system design for a four cylinder engine, computational fluid dynamics method was used to analyze the engine cooling system from layout design, system flowrate determination, flow field of the cooling system and engine temperature field. The optimization design of adding a throttling notch to the cylinder block water jacket was proposed to solve the problem of significant differences in coolant flow velocity in the cylinder block water jacket. The results show that the coolant flow velocity uniformity in cylinder block water jacket is significantly improved, and the wall temperature of each cylinder liner can be reduced by 1~3 °C. The thermal balance test results at an engine speed of 12 000 r/min show that the maximum difference in cylinder temperature is about 4 °C. The oil temperature is about 129 °C, which is controllable (less than 140 °C), indicating that the cooling system of the four cylinder engine is designed reasonably to ensure uniform cooling of each cylinder and oil cooling. [ABSTRACT FROM AUTHOR]

Microalgae biofuel has gained notoriety as a third-generation renewable fuel due to its high yield, rapid growth rate, and capability to absorb CO2. The current study provides insights into the combustion, performance and emission characteristics of neat algae oil and biodiesel from the Chlorella vulgaris microalgae as an alternative fuel source for compression ignition (CI) engine in comparison with diesel. In addition, elemental analysis and fuel characterisation studies of Chlorella vulgaris methyl ester (CVME) algae with GC–MS, FTIR, and UV–Vis are accorded. The spectral studies of CVME algae confess the existence of (C–H) along with (C–O), (C=O), (O–CH3), etc. Further, the spectral study of CVME algae with GCMS imposes the presence of methyl oleate as a significant constituent and the chemical structure of algae biofuel is C19H36O2. Conversely, the elemental compositions of CVME algae with a CHN analyser illustrate the existence of carbon, hydrogen and oxygen in the proportions of 66.80%, 11.80%, and 21.40%, respectively. The BTE of the engine fuelled with CVME shows a closer resemblance with diesel, whereas the NCVO deteriorates owing to its higher viscosity. Regardless, the combustion phenomenon such as ignition delay period, in-cylinder pressure, combustion duration and heat release rate (HRR) of NCVO and CVME are significantly lower at maximum load conditions in comparison with diesel. However, the emissions of carbon monoxide (CO), unburned hydrocarbons (UBHC) and smoke are lesser with diesel than NCVO and CVME. In contrast, the emissions of nitrous oxide (NOx) are higher for CVME compared to diesel and NCVO. [ABSTRACT FROM AUTHOR]

In this experiment, it was experimentally investigated the combustion and exhaust characteristics, as well as the thermal efficiency, of RCCI combustion using gasoline, ethanol, and propane as low-reactivity fuels under four operating conditions. For each operating condition, gISNOx was limited to 0.15 g/kWh, and gISSmoke was limited to below 15 mg/kWh. The experiment was conducted by determining the operating conditions that satisfied these limitations and resulted in the highest city thermal efficiency. The low-reactivity fuels were supplied by port injection, while diesel was directly injected into the combustion chamber using a diesel injector. As a result, when gasoline is replaced with low-carbon fuels like ethanol and propane, the reduction in CO2 emissions occurred. Under maximum power conditions, using ethanol allowed for a maximum reduction in CO2 emissions of 6.81%. Depending on the driving conditions, ethanol showed a reduction ranging from 3.60 to 6.81%, while propane exhibited a reduction ranging from 3.10 to 5.64%. Additionally, by substituting with ethanol and propane, the GIE could be improved up to 44.73 and 43.56%, respectively. [ABSTRACT FROM AUTHOR]

Natural gas/Diesel RCCI engines suffer from a lack of combustion efficiency and a high level of unburned hydrocarbon and carbon monoxide emissions, especially at low load ranges. Therefore, this study seeks to enhance RCCI engine combustion efficiency and also reduce engine emissions, especially greenhouse gases, through the complete replacement of natural gas by hydrogen as a low-reactivity fuel. To achieve this objective, a single-cylinder heavy-duty diesel engine tested as an NG/Diesel RCCI engine was nominated to operate as an H2/Diesel RCCI engine. For better control of H2/Diesel RCCI engine performance, the exhaust gas recirculation method and nitrogen addition were simultaneously used to dilute the engine intake mixture. The simulation results show that complete natural gas replacement by hydrogen in the single-cylinder NG/Diesel RCCI engine under investigation leads to a reduction in natural gas consumption up to 27,000 cubic meters per year. However, the RCCI engine operating cost would be increased more than 4.0 times by replacing the hydrogen fuel. The use of hydrogen as the sole low-reactivity fuel guarantees a 2 % increase in the RCCI engine's output power and an efficiency of more than 50 %. By reducing the fossil fuel energy share to 22 % in the RCCI engine at low load, reductions in carbon dioxide levels more than 4.0 times, unburned Methane up to 33,000 times, carbon monoxide up to 500 times, and Formaldehyde emission levels up to 2600 times can be achieved only in the absence of natural gas consumption. However, it is possible to control the thermal NOx level to less than 0.2 g/kWh in the range of EURO VI. Of course, considering the concern about the high risk of hydrogen explosions, the results confirm that the amount of unburned hydrogen emitted by the engine is less than 0.3 % of the amount of hydrogen entering the engine cylinder as a fuel. [Display omitted] • Save the natural gas consumption up to 27,000 cubic meters per year. • Achieving the gross indicated efficiency more than 50 %. • Improving the engine output power to 2 %. • Reduction in the amount of CO2 more than 4.0 times. [ABSTRACT FROM AUTHOR]

In this study, lacquer thinner (LT) has been utilized as an addition to pure gasoline in a single cylinder SI engine for increasing performance and reducing emissions. The tests were done at wide open throttle condition and 2400, 2700, 3000, 3300, 3600 and 3900 rpm engine speeds. The influences of lacquer thinner were observed on the engine torque, thermal efficiency, specific fuel consumption (SFC) and HC, CO and CO2 emissions. The findings demonstrated that with the addition of the lacquer thinner caused engine torque and power output values to decrease as the amount of lacquer thinner increased. SFC was increased by about 4.36%, 9.13% and 11.64% with LT10, LT20 and LT30 compared to full gasoline at 2700 rpm respectively. But fairly noticeable reductions were observed at CO and HC emissions as lacquer thinner added to the gasoline. HC decreased by 3.4%, 5.6% and 12.13% with LT10, LT20 and LT30 according to gasoline at 3900 rpm respectively. Similarly, CO has decreased by 1.09%, 2.18% and 3.56% with LT10, LT20 and LT30 according to gasoline at 3900 rpm respectively. Lacquer thinner showed positive and impressive results compared to pure gasoline on exhaust emissions. However thermal efficiency decreased, and SFC has increased with lacquer thinner addition to gasoline, but the reduction in engine torque and power can be acceptable considering the drastic improvements at emission levels. Also, it has been observed that lacquer thinner can be used as a gasoline additive without any modifications in spark ignition engines. Still further research is needed on Lacquer thinner on SI engines. [ABSTRACT FROM AUTHOR]

As a clean alternative fuel oil for marine engines, methanol has received increasing attention, but its low cetane number requires diesel ignition, which increases the difficulty of retrofitting existing engine fuel injection systems. Polymethoxy dimethyl ether (PODEn) is an ether fuel mixture whose chemical structural formula can be expressed as CH3O(CH2O)nCH3 ( n ≥ 2 ). PODE3 is the predominant component in the blend, and its properties are representative of the blend. PODE is a low-carbon fuel with a high cetane number and is easy to compression ignite, and, as such, can be used to ignite methanol in a marine diesel engine. This article explores the combustion mechanism of mixed methanol–PODE fuel using the characteristics of PODE that can be easily mixed with methanol for combustion. Taking methanol and PODE3 as representative fuels, the detailed combustion mechanism of PODE3 and the detailed combustion mechanism of methanol are simplified using a DRGEPSA (direct relationship graph with error propagation (DRGEP) and sensitivity analysis (SA)) method. Based on the target engine cylinder combustion environment, a simplified mechanism for mixed methanol–PODE fuel is obtained, and the new mechanism is validated in terms of the ignition delay period and laminar flame speed. The results indicate that the newly constructed simplified mechanism is basically consistent with the ignition delay data and flame propagation speed data measured by a rapid compression machine (RCM), laying the foundation for the application of alternative methanol fuels in marine engines. [ABSTRACT FROM AUTHOR]

The arrangement of a pit-shaped surface texture on the surface of a cylinder liner significantly affects reductions in piston ring friction, and the influence of the structural parameters and spatial distribution on piston ring friction power consumption is unclear. In this paper, the diameter, depth, axial spacing distance, and radial spacing distance of the pits on the inner surface of a cylinder liner were used as variable parameters to process the surface textures of different schemes, and then a friction and wear test was carried out on UMT piston ring–cylinder liner specimens, several texture schemes with the best anti-friction effect were selected, an engine bench test was carried out by comparing these texture schemes with non-texture schemes, and the frictional torque and fuel consumption of the engine were studied at different oil temperatures. The results show that the depth of the pits in the surface texture of a cylinder liner has a greater influence on the friction reduction effect, followed by the radius. The higher the oil temperature in the engine bench test, the greater the impact of the surface texture. The reduction in fuel consumption was greater in the lower-speed region after structuring the textured cylinder liner compared to the non-textured cylinder liner. Specifically, the friction coefficient was mainly affected by the depth of the pits, and the depths of the pits in the texture schemes with good friction reduction effect were all 17–19 μm. The best friction reduction could be achieved when the pit radius is around 50 μm, with little difference in pit depth. When the oil temperature was 95 °C, the average drag torque reduction was about 1.69 Nm; when the oil temperature was 105 °C, the decrease was about 2.54 Nm; and when the oil temperature was 105 °C, the decrease was about 4.53 Nm. After adding the surface texture of the cylinder liner, the fuel consumption rate of the engine equipped with the structured cylinder liner was generally reduced compared with that of the original cylinder liner engine. Among them, the average and subsequent consumption rate of surface assembly scheme 11 decreased the most, with a value of 1.3 g/kwh. [ABSTRACT FROM AUTHOR]

In pursuit of carbon neutrality, the adoption of zero-carbon fuels in internal combustion engines offers a path to zero carbon emissions. Among such fuels, ammonia (NH 3) stands out as an effective hydrogen energy carrier with a higher energy density and a more advanced production-storage-transportation lifecycle than hydrogen (H 2) fuel, making it a superior alternative. Nevertheless, achieving high combustion efficiencies in engine cylinders requires the use of fuels with fast flame speeds, since the time scales of the combustion event are practically milliseconds. The inherent flame speed of NH 3 falls short, typically necessitating augmentation with H 2. Yet, the in-situ generation of H 2 from NH 3 remains constrained, rendering the flame speed of NH 3 less competitive against traditional fuels like gasoline and natural gas. To address the dual challenges of slow flame speed of NH 3 and the difficulty of generating large amounts of H 2 from NH 3 onboard, this study evaluates an alternative method of accelerating the ammonia combustion in the engine combustion chamber through the use of multiple spark plugs, which is limited discussed in existing research. Numerical simulations performed in this study show that the application of the multi-spark strategy increases the mass burn rate, advances the combustion phasing, shortens the combustion duration, increases the engine power output, improves the fuel economy, and reduces the unburned ammonia emissions, all of which indicate that rapid combustion of pure ammonia is achieved in the combustion chamber. Moreover, the use of multiple spark points does not lead to a marked increase in nitrogen oxides emissions, thereby ensuring no added stress on exhaust aftertreatment systems. In addition, pure ammonia combustion appears to be very well adapted to this strategy, as evidenced by the avoidance of excessive cylinder pressures and pressure rise rates—a challenge faced by conventional spark ignition engines, given ammonia notably slower flame speed relative to conventional petroleum-based fuels. Overall, all these findings strongly support that the multi-spark ignition system presents a compelling direction for future zero-carbon ammonia engines. However, it is crucial to address design challenges to ensure that the engine head layout provides sufficient cooling, structural robustness, optimal breathing efficiency, and reliable multi-ignition events within the confined space. • Multi-spark strategy enlarges flame-front area, shortening flame travel length. • Multiple sparks enable pure ammonia rapid combustion in engines. • Pressure rise rate of ammonia operation stays safe with multi-spark ignition. • Additional sparks cannot notably increase nitrogen oxides emissions in ammonia engines. • Engine head layout needs optimization for the multi-spark system. [ABSTRACT FROM AUTHOR]

A novel three-equation turbulence model has been proposed as a potential solution to overcome some of the issues related to the k–ε models of turbulence. A number of turbulence models found in the literature designed for compressed turbulence within internal combustion engine cylinders tend to exhibit limitations when applied to turbulent shear flows, such as those occurring through intake or exhaust valves of the engine. In the event that the flow is out of equilibrium where Pk deviates from ε, the turbulence models require a separate turbulence time-scale determiner along with the dissipation, ε. In the current research, this is accomplished by resolving an additional equation that accounts for turbulence time scale, τ. After presenting the rationale behind the model, its application to three types of free shear flows were given. It has been shown that the three-equation k–ε–τ model outperforms the standard k–ε model as well as a number of two-equation models in these flows. Initially, the k–ε–τ model handles the issue of the plane jet/round jet anomaly in an effective manner. Secondly, it outperforms the two-equation models in predicting the flow behavior in the case of plane wake, one that is distinguished by its weak shear form. [ABSTRACT FROM AUTHOR]

A computational study has been performed to evaluate the use of jet impingement for cooling applications in the automotive industry. The current study uses an entire internal combustion engine cylinder with its components as a computational domain. An unsteady numerical solution for the Navier-Stokes equations was carried out using Improved Delayed Detached Eddy Simulation (IDDES). The volume of fluid approach is proposed to track and locate the liquid jet surface that is in contact with the air. The conjugate heat transfer approach is used to link the heat transfer solution between the fluid and the solid. The boundary conditions that are employed in the study are provided from lab experiments and one-dimensional simulations. The cooling jet in this study targets the hottest region in the piston, i.e., the region underneath the exhaust valve. Three nozzle sizes with flows at different Reynolds numbers are chosen to examine the thermal characteristics of the cooling jet. The computational study reveals that for a specific Reynolds number, the smaller diameter nozzle provides the highest heat transfer coefficient around the impingement point. The maximum relative velocity location at the impingement point slightly leads the location of the maximum Nusselt number. The maximum temperature in the piston decreases by 7% to 11% as the nozzle diameter changes from 1.0 to 3.0mm for a jet Reynolds number of 4,500. If a correct selection is made for the nozzle size, the cooling jet can be efficiently used to reduce the temperature and alleviate the thermal stresses in the piston in the region underneath the exhaust valve where the maximum temperature occurs. [ABSTRACT FROM AUTHOR]

With the increasing temperature and pressure in the cylinder of the diesel engine, the in-cylinder environment gradually exceeded the thermodynamic critical point of hydrocarbon fuel. Compared with subcritical spray, the phase transformation mechanism of supercritical spray is essentially changed. In this paper, the n-heptane fuel sprays in three conditions case 1 (T1 = 400 K P1 = 2 MPa), case 2 (T2 = 600 K P2 = 2 MPa), and case 3 (T3 = 800 K P3 = 6 MPa) were obtained by high-speed digital schlieren method on the test platform of a constant volume combustion bomb. The spray liquid phase, liquid–gas mixed layer, and mixture were divided, and the variation rules of the spray cone angle, the liquid phase length, maximum interface thickness, and liquid– gas mixed layer area were discussed. The results showed that the higher the ambient temperature and pressure, the more severe the fragmentation of the spray. Compared with the subcritical condition, the spray penetration distance in the supercritical condition tended to be flat faster. Compared with 400 K, 2 MPa condition, the spray cone angle was about 33° and 50% larger at 800 K, 6 MPa condition. The liquid core area at 800 K, 6 MPa condition was 60 cm², reduced by 75% compared with 400 K, 2 MPa condition, resulting in better spray diffusion and mixing with atmospheric gas. The sensitivity analysis of ambient temperature and pressure on spray characteristic parameters shows that temperature has a greater impact on the interface mixing layer area (VIP = 1.23), and pressure has a greater on penetration distance and spray penetration rate (VIP = 1.23). When the environmental conditions exceed the thermodynamic critical point, the area of the liquid–gas mixed layer increases due to the transformation of spray from evaporation to diffusion and the phenomenon of interfacial layer enrichment. In summary, the supercritical condition promotes the mixing of spray and environment and has a positive effect on spray diffusion and atomization. [ABSTRACT FROM AUTHOR]

The importance of renewable fuels as an alternative to fossil fuels is increasing due to environmental problems such as the decrease in the reserves of fossil fuels, their presence in certain regions, air pollution and global warming. Two important parameters of biodiesel fuel, which is one of these fuel types, such as high viscosity and density, negatively affect its use. One of the ways to overcome this negative situation is to improve the fuel properties by adding nano fuel additives into biodiesel. In this study, titanium dioxide nano fuel additive was added to biodiesel obtained from cottonseed oil at the rates of 50 ppm and 75 ppm. Specific fuel consumption, brake thermal efficiency and cylinder pressure values, which are the basic performance parameters of the fuel mixtures, were determined in a single cylinder engine at 1800 rpm at 4 different engine loads. According to C100 fuel SFC decreased by 5.03% and 6.29% at 10 Nm load, respectively in CTi-50 and CTi-75 fuels. This improvement rate was 8.73% and 12.58% at 40 Nm load. BTE increased by 8.97% and 13.17% with NPs additives. Thanks to the thermophysical properties of the titanium dioxide fuel additive, the combustion reaction has improved and cylinder pressure increased. It was determined in the study that it positively affected the engine performance and fuel economy. [ABSTRACT FROM AUTHOR]

The experimental study was conducted to investigate the effect of using Cresson oil biodiesel on CI engine emissions and performance. This research aimed to examine how using innovative biodiesel blend formulations made from Cresson oil affected the performance and emissions of CI engines. The proportion of Cresson oil biodiesel added to conventional Iraqi diesel fuel into volume amounted to 10%, 20%, 40%, 60%, 80%, and 100%. The engine compression ratio was set to 18, and the fuel injection timing was set at 23° bTDC. The experiments show that this biodiesel reduces the thermal efficiency, heat release, delay time, and cylinder pressure of the engine while increasing the exhaust temperature (EGT) and brake-specific fuel consumption (BSFC). There has been an increase in emissions of nitrogen oxides (NOX) and carbon dioxide (CO2), in addition to a reduction in emissions of carbon monoxide (CO), soot, and unburned hydrocarbons (HC). [ABSTRACT FROM AUTHOR]

Gas motion in the engine cylinder plays a critical role in diesel engines' air-fuel mixing and combustion processes. Moreover, it influences the engine's performance, emissions, and heat transfer. The intake air motion regulates the main phases of the flow in the cylinder, which is characterized by swirl, squish, and turbulence. Inducing swirl and tumble in the intake process provides high turbulence levels at ignition, resulting in more effective flame speeds and better combustion for lean air-fuel ratios or with EGR. Computational fluid dynamics (CFD) software is used to enhance in-cylinder flow characteristics. In this study, a cold flow simulation of a naturally aspirated, direct injection diesel engine was conducted with different piston bowls using AVL Fire M R2022.2. Swirl, tumble, and TKE parameters were investigated to make a detailed analysis of the in-cylinder flow for the relevant engine. Contrary to the expectation, the swirl ratio for the Piston B configuration is less than that for the original piston configuration. It causes a decrement of swirl ratio compared to the initial piston geometry and the maximum decrement is about 19%. In both cases, the second peak of TKE corresponding to the reverse-squish is around at the -30 CA and the difference between the curves is about ±8%. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) is emerging as a potential favoured fuel for longer range decarbonised heavy transport, particularly in the marine sector, predominantly due to highly favourable characteristics as an effective hydrogen carrier. This is despite generally unfavourable combustion and toxicity attributes, restricting end use to applications where robust health and safety protocols can always be upheld. In the currently reported work, a spark ignited thermodynamic single cylinder research engine equipped with gasoline direct injection was upgraded to include gaseous ammonia port injection fuelling, with the aim of understanding maximum viable ammonia substitution ratios across the speed-load operating map. The work was conducted at varied effective compression ratios under overall stoichiometric conditions, with the spark timing re-optimised for maximum brake torque at all stable logged sites. The experiments included industry standard measurements of combustion, performance, and engine-out emissions (including NH3 "slip"). With a geometric compression ratio of 11.2:1, it was found possible to run the engine on pure ammonia at low engine speeds (1000-1800 rpm) and loads of 12 bar net IMEP. When progressively dropping down below this load limit an increasing amount of gasoline co-firing was required to avoid engine misfire. When operating at 1800 rpm and 12 bar net IMEP, all emissions of carbon (CO2, CO, unburned hydrocarbons) and NOx decreased considerably when switching to higher NH3 substitution ratios, with NOx reduced by ~ 45% at 1800 rpm/12 bar when switching from pure gasoline to pure NH3 (associated with longer and cooler combustion). By further increasing the geometric compression ratio to 12.4 and reducing the intake camshaft duration for maximum effective compression ratio, it was possible to operate the engine on pure ammonia at much lower loads in a fully warmed up state (e.g., linear low load limit line from 1000 rpm/6 bar net IMEP to 1800 rpm/9 bar net IMEP). Under all conditions, the indicated thermal efficiency of the engine was either equivalent to or slightly higher than that obtained using gasoline-only due to the favourable anti-knock rating of NH3. Ongoing work is concerned with detailed breakdown of individual NOx species together with measuring the impact of hydrogen enrichment across the operating map. [ABSTRACT FROM AUTHOR]

The push for decarbonization of internal combustion engines (ICEs) has spurred interest in alternative fuels, such as hydrogen and ammonia. To optimize combustion efficiency and reduce emissions, a closer look at the intake system and in-cylinder flows is crucial, especially when a hard-to-burn fuel, such as ammonia is utilized. In port fuel injection ICEs, airflow within cylinders profoundly affects combustion and emissions by influencing the air–fuel mixing phenomenon. Adjusting intake port openings is an important factor in controlling the in-cylinder airflow. In previous experiments with a transparent cylinder, tangential and helical ports demonstrated that varying the helical port's opening significantly impacts flow velocities, swirl ratios, and swirl center positions (SCPs). In this study, we used a particle image velocimetry technique to investigate how the tangential port's opening affects intake and in-cylinder flows. Flow velocities were assessed at different planes near the cylinder head, evaluating streamline maps, turbulent kinetic energy (TKE), and SCPs. Under the given experimental conditions, swirl flows were successfully generated early in the compression stroke when the tangential port opening exceeded 25%. Our findings emphasize the importance of minimizing TKE and SCP variation for successful swirl flow generation in engine cylinders equipped with both tangential and helical ports. [ABSTRACT FROM AUTHOR]

The main concern of any automobile is to improve efficiency and reduce emissions. The depletion of Fossil Fuels has posed an alarming consequence for the field of Automobile engineering. To reduce emissions and increase efficiency, Butanol is adopted as an alternative fuel and tetra nitro methane (TNM) as an additive. The experiments were carried out on a 4-stroke single-cylinder diesel engine 5Hp rated power at different loads. The performance parameters like brake power, total fuel consumption, brake thermal efficiency and the emissions CO, CO2, HC and NOx are measured carefully. Among all the blends, 70%D-30%B has shown a more interesting change in thermal efficiency and emissions. At this proportion, TNM was added as an additive in different proportions. All the performance parameters were calculated, and emissions were measured at all proportions of TNM. There was a further increase in thermal efficiency and a reduction in emissions when the TNM was added. The higher thermal efficiency was achieved at a 70%D-30%B- 15%TNM proportion with lower emissions when compared to diesel alone. [ABSTRACT FROM AUTHOR]

As fossil fuel is depleted day by day, there is a vast gap in the market and supply of fuel to the different industries that consume oil. In order to improve fuel properties, performance, combustion, and emissions from diesel engines, microalgae oil biodiesels are used as fuel with 20% of diesel on a mass basis by volume and 50 and 100 ppm of CeO2 nanoparticles as additives in combinations of biodiesel/diesel blends. The engine configuration consists of a single-cylinder, four-stroke, 3.5 kW, 1500 rpm diesel engine. Experiments were performed at constant speed on experimental test fuels for various load conditions. The addition of cerium oxide (CeO2) in the added biodiesel diesel blends improved the brake thermal performance (45%) compared to engine output. With CeO2 in the B20 blends, better combustion properties were observed, such as increased length of combustion (36 CA°), ignition delay (16 CA°), and heat release rate (55 J/deg) in the cylinder. The enhanced and improved fuel characteristics and combustion characteristics of CeO2 in the added biodiesel diesel blends minimise HC (0.54 g/kWh) and CO (4.6 g/kWh) emissions and smoke (0.61%) while increasing NOx (10.2 g/kWh) emissions from the engine cylinder. [ABSTRACT FROM AUTHOR]

Due to the fact that emission reduction has become an important topic and due to the upcoming EURO 7 standard, the automotive industry is focusing on reducing the carbon footprint. One of the ways to do so is enhancing the efficiency of internal combustion engines by technologies such as cylinder deactivation. This technology offers fuel economy benefit, therefore, also CO2 emission reduction. However, implementing cylinder deactivation to modern engines with lower cylinder count can be challenging. The implementation requires numerous design modifications and some negative consequences like higher torsional vibration are associated with the technology. This paper focuses on investigating these constraints of cylinder deactivation. [ABSTRACT FROM AUTHOR]