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Thanks to its carbon-free nature, it is possible to say that hydrogen is a potential fuel for future automotive systems. Its main favourable properties include high burning rate, wide range of flammability and low ignition energy. In combination with hybrid electric technology, the hydrogen combustion engine has the potential for further development with the goal of maximum efficiency in energy conversion. For more efficient hydrogen combustion, a dual fuel injection hybrid system is designed, where one injector is designed for direct hydrogen injection into the engine cylinder and the other injector is supply fuel to the engine's intake pipe. The greatest challenge is development of a control algorithm intended for management of the combustion process in hydrogen engine and optimization of fuel injection divided into individual doses. [ABSTRACT FROM AUTHOR]

Ammonia-hydrogen engines are promising for heavy-duty, long-distance transportation, while the lower hydrogen energy share (X H2) in ammonia-hydrogen fuels facilitates hydrogen storage and use. In this study, a numerical investigation of engine performance based on an engine with ammonia port injection and different hydrogen jet ignition strategies at a fixed X H2 of 3% was conducted. The results show that too-early hydrogen injection results in lower hydrogen concentration and weak ignition in the pre-chamber, while too-late injection results in less hydrogen entering the main chamber, making more ammonia not mix well with the hydrogen, both of which increase the combustion duration. Hydrogen injection at the bottom dead center before the compression stroke mixes the hydrogen with the ammonia preliminary and leads to the formation of a high-temperature, slightly lean-burn region during the combustion, which worsens NO emission but reduces N 2 O emission. Compared with hydrogen single injection, splitting the same mass into two equal-mass injections favors higher peak pressures, shorter combustion durations, and higher indicated thermal efficiency (ITE). Injections at 360 and 90 °CA before the top dead center, respectively, achieve at least 1% relatively higher ITE with similar NO, NH 3 , and N 2 O emission performance compared with the single injection. • Study of a large bore H 2 active jet ignition NH 3 –H 2 engine at 3% H 2 energy share. • Multiple injection favors shorter combustion durations and higher engine efficiency. • Injection at the bottom dead center likely to lead to high NO and low N 2 O emissions. • Injecting hydrogen too early or too late both prolongs the combustion duration. [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]

The atomization and mixing process in a linearized rotating detonation engine supplied with non-premixed kerosene was optically analyzed by experiment. Schlieren, simultaneous LIF/Mie technique and particle/droplet image analysis (PDIA) system were applied to study flow field structure and spray properties under various conditions, including air flow rate, fuel flow rate and flow velocity at injector position. Aerodynamic shearing force and fuel injection pressure contribute to the refinement and uniformity of the spray. The distribution of fuel in the combustor has obvious stratification, which makes the local equivalence ratio higher than the set global equivalence ratio. Compared with full-scale RDE experiments, the detonation wave exists in a dual-wave collision mode. The increased kerosene flow rate refines the droplets, which raises the detonation wave velocity. Furthermore, the detonation wave will propagate more stably due to the slower airflow velocity at higher combustor pressure. [ABSTRACT FROM AUTHOR]

With the continuous development of hydrogen energy technology, mixing hydrogen has become a potential method to enhance the performance of natural gas engines and reduce emissions. Aiming to offer guidance for optimizing strategies for mixing hydrogen from the perspectives of knock control and thermal efficiency enhancement, a three-dimensional model of a commercial heavy-duty natural gas engine is constructed based on the actual boundary conditions from a high load bench test. In this study, simulations were conducted under conditions where the hydrogen volume fraction ranged from 0% to 40%. The study explored the effects of two injection strategies, port fuel injection of hydrogen-enriched natural gas (PFI) and port fuel injection of natural gas combined with direct injection of hydrogen into the cylinder (PFI + DI), on engine knocking, performance, and emissions. Results indicate that for various injection strategies, there is an increasing trend in knock intensity (KI) with the higher hydrogen mixing ratio. When the hydrogen volume fraction exceeds 20%, the timing of direct hydrogen injection significantly affects KI. This effect is mainly caused by the distribution of unburned hydrogen at the knock onset crank angle (KOCA). Compared to other injection strategies, the PFI + DI strategy when the direct hydrogen injection time at 120°CA BTDC results in a high concentration of hydrogen near the spark plug at the ignition moment, combined with good mixture uniformity in the cylinder. This leads to the shortest CA0-10 and CA10-90, and achieves a maximum indicated thermal efficiency (ITE) of 44.68% under 20% hydrogen volume fraction. Compared to the original natural gas engine, the ITE increased by 2.9% and the NO x emissions increased by 166%, while the HC and CO emissions decreased by 88% and 53%. • Effects of different hydrogen mixing strategies on a natural gas engine are studied. • Knock intensity correlates with unburned hydrogen distribution at knock onset crank angle. • Hydrogen mixing methods affect mixture uniformity and TKE in cylinder. • At 20% hydrogen volume fraction, direct hydrogen injection timing of 120°CA BTDC maximizes ITE. [ABSTRACT FROM AUTHOR]

In recent years, developments in the automotive sector have impacted consumer preferences in transportation, creating more options for consumer needs in this area. Changing consumer needs raises a number of complex issues, such as how automotive companies should develop their products and what actions should be taken to ensure that their brands are popular with consumers and increase their loyalty. It is necessary to investigate the preferences of consumers regarding electric cars, which are expected to be among the types of vehicles that will become increasingly popular in the near future in terms of efficiency and utility. The aim of this study is to investigate consumers' purchasing processes, to determine the preferred brands and car features in this process and to determine consumers' expectations of new car models. At the same time, this study aimed to assess car users' perspectives on electric vehicles and examine participants' preferences for traditional fuel types such as gasoline, diesel and LPG, as well as electric and hybrid vehicles. The study used a questionnaire to collect data from customers of an automotive company to identify the factors that influence consumer preferences in the automotive sector. As part of the study, a 16-question questionnaire was randomly distributed to 405 respondents. In analysing the data, descriptive statistics were used to determine the demographic characteristics of the participants, chi-square tests were used to examine the relationships between demographic characteristics and factors influencing consumers' purchasing decisions, and multidimensional preference analysis methods were used to determine the most important and most preferred characteristics of customers when purchasing. The multidimensional preference analysis method, a multivariate statistical method, provides valuable information about the factors that determine consumers' preferences and decisions. Multidimensional preference analysis provides companies with an important perspective on both competition and the identification of gaps in the market. According to the results of the data analysis, participants indicated that a new generation car should have low fuel consumption and a good safety system. While the environmental friendliness of electric vehicles and the increase in diesel and gasoline prices were the main reasons for their preference, the reasons for nonpreference were problems with recharging. [ABSTRACT FROM AUTHOR]

The high efficiency and environmental friendliness make hydrogen and fuel cell technology important players in today's energy market. However, the durability issue is a major setback for fuel cells' adoption in various applications, including automotive. As automotive fuel cells exhibit non-linearity and dynamic behavior, predicting their performance has become a complex task since their response changes rapidly to varying operating conditions. To enhance performance prediction reliability, this study proposes a novel recursive multi-step performance prediction method for automotive fuel cells based on conditional time series forecasting with convolutional neural network (CNN). The method incorporates a conditional CNN architecture to extract representative features from the input data and a recursive strategy to iteratively predict future values based on previous predictions. Moreover, the seasonality in the data is detected to correct the prediction results by considering the intermittent performance recoveries. Experimental results show that the proposed approach achieves high prediction accuracy, particularly for long-term performance prediction. The proposed method could have significant implications for improving the reliability and efficiency of automotive fuel cell systems. • Interval of recoverable degradation is identified by seasonality identification. • A conditional CNN is developed to mitigate error accumulation problem. • Dynamic durability test data are used for model training and validation. [ABSTRACT FROM AUTHOR]

Compressed Natural Gas (CNG) is recognized as an environmentally friendly alternative vehicle fuel, but it has a low flame speed. Combining hydrogen with CNG to create 'hydrogen compressed natural gas' (HCNG) allows for faster and leaner combustion. Additionally, OME 2 − 4 with varying cetane numbers, from 63 for OME 2 to 90 for OME 4 , serves as a highly reactive fuel suitable for use in a dual fuel strategy known as RCCI (reactivity-controlled compression ignition). This project investigates the impact of adding OME 2 − 4 to HCNG, focusing on pressure, temperature, and emissions. Results indicate that lengthening the OME chain advances the peak heat release rate but delays the second combustion phase. In diesel + HCNG , the first-phase combustion is 2 °CA shorter than OME 2 + HCNG , resulting in a 6.5% higher peak pressure than OME 2 + HCNG and a 20% increase over basic diesel. Lengthening the OME chain from OME 2 to OME 4 raises the peak pressure by about 6.2%. The addition of gaseous fuels, especially hydrogen, increases peak temperature by 16%. OME 4 + HCNG has a similar peak temperature to OME 3 + HCNG , while OME 2 + HCNG is about 1.5% lower than OME 4 + HCNG. [Display omitted] • The peak pressure for diesel + HCNG is approximately 20% higher than that of basic diesel (115.0 bar). • Lengthening the OME chain from OME 2 to OME 4 increases the peak pressure by 6.2% (from 134.9 bar to 143.3 bar). • The OME n + HCNG configurations decrease soot formation, reducing it from 1466 ppm in basic diesel to 6 ppm for OME 2 + HCNG. [ABSTRACT FROM AUTHOR]

The proton exchange membrane fuel cell gas control has been one key point in fuel cell management systems. The complexity and coupling of the air management system make it difficult to achieve precise air intake adjustment. In this paper, an accurate joint control method for the air flow and pressure regulation is proposed. The nonlinear mathematical model of the air management system is developed to describe the output characteristic and state change. Based on this, the feedback linearization method is proposed to obtain the direct correspondence between control variables and controlled variables. In addition, to solve the problem that the controlled variables cannot be measured directly, an extended state observer is applied to estimate the stack cathode pressure. The sliding mode predictive control method is proposed to control the oxygen excess ratio and cathode pressure simultaneously. The relative order of the system is used to design the sliding mode surface, and the corresponding predictive model is proposed. The results obtained by simulation experiments show that pressure and mass flow have little effect on each other through decoupling. The proposed algorithm has been verified to have high precision, fast response, and robustness through comparative experiments. [ABSTRACT FROM AUTHOR]

Natural gas (NG) is a low-carbon fuel that can achieve low carbon emissions and high efficiencies. However, the low mean molecular mass and low energy density of methane result in low engine performance, and blending methane with gasoline is an effective way of improving the performance of NG engines. In this study, flame characteristics (including abnormal combustion) and engine performance are optically studied under methane port injection and isooctane direct injection conditions. The results indicate that the addition of isooctane can significantly increase the power output of NG engines. Under partial-load conditions, the minimum ignition advance for best IMEP is delayed with the addition of isooctane because of the higher flame speed of isooctane, and isooctane addition primarily improves the turbulent flame propagation rather than the initial flame formation. As for the isooctane injection timing, the indicated mean effective pressure (IMEP) first increases and then decreases with the delay in isooctane injection. The hot spots in the flame images confirm that late injection results in isooctane inhomogeneity, which reduces the engine's thermal efficiency. At high loads, the low energy density of methane can lower the knocking intensity, even in the presence of auto-ignition at a speed of 120.7 m/s. The knocking pressure can lead to the ejection of oil droplets, which can increase the flame speed in the subsequent cycle. [ABSTRACT FROM AUTHOR]

Gasoline compression ignition (GCI) has been considered as a promising combustion concept to yield ultralow NOX and soot emissions while maintaining high thermal efficiency. However, how to improve the low-load performance becomes an urgent issue to be solved. In this paper, a GCI engine model was built to investigate the effects of internal EGR (i-EGR) and pre-injection on in-cylinder temperature, spatial concentration of mixture and OH radical, combustion and emission characteristics, and the control strategy for improving the combustion performance was further explored. The results showed an obvious expansion of the zone with an equivalence ratio between 0.8~1.2 is realized by higher pre-injection ratios, and the s decreases with the increase of pre-injection ratio, but increases with the increase of i-EGR ratio. The high overlap among the equivalentmixture zone, the hightemperature zone, and the OH radical-rich zone can be achieved by higher i-EGR ratio coupled with higher preinjection ratio. By increasing the pre-injection ratio, the combustion efficiency increases first and then decreases, also achieves the peak value with a pre-injection ratio of 60% and is unaffected by i-EGR. The emissions of CO, HC, NOX, and soot can also be reduced to low levels by the combination of higher i-EGR ratios and a pre-injection ratio of 60%. [ABSTRACT FROM AUTHOR]

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As an important component of the fuel injection system, the fuel injector is crucial for ensuring the power, economy, and emissions for a whole ME (machine electronically-controlled) marine diesel engine. However, injectors are most prone to failures such as reduced pressure at the opening valve, clogged spray holes and worn needle valves, because of the harsh working conditions. The failure characteristics are non-stationary and non-linear. Therefore, to efficiently extract fault features, an improved refined composite multi-scale dispersion entropy (IRCMDE) is proposed, which uses the energy distribution of sampling points as weights for coarse-grained calculation, then fast correlation-based filter(FCBF) and support vector machine (SVM) are used for feature selection and fault classification, respectively. The experimental results from a MAN B&W 6S35ME-B9 marine diesel engine show that the proposed algorithm can achieve 92.12% fault accuracy for injector faults, which is higher than multiscale dispersion entropy (MDE), refined composite multiscale dispersion entropy (RCMDE) and multiscale permutation entropy (MPE). Moreover, the experiment has also proved that, due to the double-walled structure of the high-pressure fuel pipe, the fuel injection pressure signal is more accurate than the vibration signal in reflecting the injector operating conditions. [ABSTRACT FROM AUTHOR]

The shutdown process is one of the critical stages when the proton exchange membrane fuel cell system runs as an actual application. Finding the effect of system operating conditions on shutdown purging could improve the purging effect of liquid water and the dehydration of the stack. In this study, an automotive fuel cell system of 350 single cells was developed on the vehicle scale and tested for factors that influence shutdown process. Seven shutdown purge cases for about 150 s were studied to investigate the shutdown purge strategy. It was found that 100% bypass valve opening reduced the purge time and improved the purge efficiency. The HCP speed should not be too slow or too fast in the shutdown process. The higher temperature of coolant water favored rapid shutdown and purge, and a large stoichiometric ratio of the cathode inlet improved the purge effect but enhanced the energy consumption of the air compressor. Neither too high nor too low purge pressure could blow out the liquid water more efficiently and improve the ohmic resistance. During purging, current density mainly influenced the water production rate and the maintenance state of stack temperature. With a higher stack temperature, purge process with a small current density could quickly reduce the stack humidity and enhance the ohmic resistance. Accelerating the opening rate of the anode purge valve could not effectively accelerate purge effect of the stack, while extending the valve closing time could improve hydrogen utilization. Future studies to investigate the combined impact of these factors on the fuel cell system shutdown purge will be carried out to develop the most effective strategy. • Water transport and balance in the PEMFC were summarized. • An automotive fuel cell system was developed on the vehicle scale. • Seven shutdown purge cases for about 150 s were tested. • The influences of these system parameters on the purging effect was studied. [ABSTRACT FROM AUTHOR]

The current study is focused on how varying injection pressure in the fuel supply system of multi-point injection systems can improve fuel atomization and injection jet range. The aim is to achieve a more efficient mix dosage, thus improving combustion and reducing exhaust emissions. In addition, it is intended to develop a characterization of the injection actuators, specifically the injectors, through a series of tests in which the injector pressure, engine speed and injection pulse are modified. To carry out these tests, a heuristic testing technique, like the empirical approach, was implemented, and a mobile device was used to capture the spray frames of the injectors. These data were then used to generate a correlation model between injection and spray angles, considering 0.5 bar pressure variation intervals within the established ranges. This approach made it possible to visualize and record the behavior of the spray in the injector, including the spray angle, the injected fuel flow rate and the working pressure during the operation process. Following the guidelines established in the proposed methodology, a significant result was obtained by varying the pressure at 5 bar and with an injection pulse of 2 ms. In this case, a flow reduction of 66 mL of the injected fluid was achieved, which corresponds to a significant reduction in fuel consumption. Additionally, a spray angle of 10.48° was observed with optimized atomization. These results were verified on vehicles with similar injection systems by testing on the GT-600-PRO injection test bench. In summary, this study shows that by varying the injection pressure and optimizing other parameters, it is possible to achieve a significant reduction in fuel consumption and improve fuel atomization in multipoint injection systems. These findings have a significant impact on the Ecuadorian vehicle fleet and provide a scientific approach to improving fuel efficiency and performance. [ABSTRACT FROM AUTHOR]

The cold start-up of a proton exchange membrane fuel cell is considered one of the main factors affecting the commercialization of fuel cell vehicles. In this study, an automotive fuel cell system was designed and tested for cold start-up at low temperatures. In the absence of PTC (Positive Temperature Coefficient) heating device, the stack was directly loaded to generate heat, which provided the cold start-up characteristics of system at low temperatures. Cold start-up process and purging control strategies were analyzed at −20 °C and −30 °C. It was found that the fuel cell system could produce 50% power in 25 s at −20 °C, the coolant temperature's heating rate was 0.78 °C/s, the coolant outlet temperature could reach 20 °C within 40 s and no apparent low voltage of single cell occurred. While, the cell close to the end plate had low cell voltage and reverse polar phenomena throughout the −30 °C cold start-up process. The heating rate of the coolant temperature was 0.44 °C/s, and the temperature of coolant outlet reached 20 °C within 90 s. The purging time ranged from 180 to 260 s according to the voltage drop value of stack and the ohmic resistance of stack was 360–470 mΩ after the high-volume air purging at different tests. After 30 cold start-up tests, the rated point performance of the stack declined by about 1%, and the consistency of cell voltages did not change significantly. Future work will focus on optimizing cold start-up strategy and speeding up purging time to minimize the performance impact of the cold start-up. • An automotive fuel cell system was tested for cold start-up without PTC heating. • Cold start-up process and purging control strategies were analyzed. • Voltage changes at different stack sections were showed and discussed. • The performance declined by 1% and the consistency did not differ significantly. [ABSTRACT FROM AUTHOR]

The efficiency enhancement of argon power cycle engines through theoretical means has been substantiated. However, the escalation of in-cylinder temperatures engenders abnormal combustion phenomena, impeding the augmentation of compression ratios and practical efficiency. This study presents a comprehensive investigation employing experimental and simulation techniques, aiming to extend the boundaries of thermal efficiency and operational capabilities for hydrogen-powered argon cycle engines. The impact of hydrogen direct injection, intake boost, and port water injection is evaluated in conjunction with an argon power cycle hydrogen engine. The hydrogen direct injection, particularly at an engine speed of 1000 rpm, significantly increases the indicated mean effective pressure from 0.39 MPa to 0.72 Mpa, surpassing the performance of the port hydrogen injection. Manipulating the hydrogen direct injection timing results in the formation of a stratified mixture, effectively attenuating the combustion rate, and resolving the issue of excessively rapid hydrogen combustion within an Ar/O2 environment. The implementation of super lean combustion, combined with intake-boosting, achieves a maximum gross indicated thermal efficiency of 57.89%. Furthermore, the port water injection proves to be an effective measure against knock, broadening the operational range of intake-boosted conditions. Notably, the maximum gross indicated thermal efficiency recorded for the port water injection group under intake-boosted conditions reaches 59.35%. [ABSTRACT FROM AUTHOR]

The direct injection (DI) hydrogen-fueled internal combustion engine (H 2 -ICE), as a promising carbon-neutral power device, has attracted more and more attention. However, the effects of the hydrogen injection strategy on the performance of H 2 -ICE lack in-depth analysis, even under the high injection pressure. Therefore, the present work investigated the thermal efficiency and NO x emissions with a single-hole injector over a wide range of high injection pressure and injection timing in a 3-cylinder turbocharged DI H 2 -ICE. The results show the strong dependence of high thermal efficiency on turbocharging and lean-burn strategies. The late-injection strategy can achieve higher thermal efficiency than the early-injection strategy, which can be applied at a wide range of loads. The effect of injection strategy on the brake thermal efficiency (BTE) mainly depends on the wall heat loss. Hydrogen late injection can reduce the wall heat loss by about 2% through strong mixture stratification. Furthermore, hydrogen late injection is always accompanied by a sharp increase in NO x emissions, even by orders of magnitude. This trade-off relationship between thermal efficiency and NO x emissions can be well optimized by a moderate late-injection strategy with an end-of-injection (EOI) of about 40 °CA. At the given load and start of injection (SOI), increasing the injection pressure from 5 MPa to 15 MPa can reduce the hydrogen injection duration by about 3 times. Under the higher injection pressure, the BTE performs a strong sensitivity to SOI. The BTE is improved by about 0.5% by optimizing SOI at P I n j = 5 MPa mainly due to the reduced compression loss caused by further delay to the SOI allowed by higher injection pressure, while this improvement increases to about 2.3% at P I n j = 15 MPa. However, at a given SOI, the highest BTE at P I n j = 5 MPa is nearly 1.5% higher than that at P I n j = 15 MPa, which implies the potential of low-pressure injection coupled with large-flow injectors. Finally, the DI H2-ICE performs well in terms of efficiency with a maximum BTE of 44.08%. • The interactions among injection pressure and injection phasing were clarified. • Engine performance under the high injection pressure was investigated in an actual engine. • NO x emissions can be reduced by a moderate late-injection strategy without decreasing BTE. • BTE is improved with the increased injection pressure due to the extended SOI windows. [ABSTRACT FROM AUTHOR]

The development of innovative technologies based on employing green energy carriers, such as hydrogen, is becoming high in demand, especially in the automotive sector, as a result of the challenges associated with sustainable mobility. In the present review, a detailed overview of the entire hydrogen supply chain is proposed, spanning from its production to storage and final use in cars. Notably, the main focus is on Polymer Electrolyte Membrane Fuel Cells (PEMFC) as the fuel-cell type most typically used in fuel cell electric vehicles. The analysis also includes a cost assessment of the various systems involved; specifically, the materials commonly employed to manufacture fuel cells, stacks, and hydrogen storage systems are considered, emphasizing the strengths and weaknesses of the selected strategies, together with assessing the solutions to current problems. Moreover, as a sought-after parallelism, a comparison is also proposed and discussed between traditional diesel or gasoline cars, battery-powered electric cars, and fuel cell electric cars, thus highlighting the advantages and main drawbacks of the propulsion systems currently available on the market. [ABSTRACT FROM AUTHOR]

Engine vibration is one of the main excitation sources of vehicle vibration. In order to study the problem of excessive vibration in the cabin of a light vehicle when the air conditioning is turned on at the idle speed, this study is conducted from the point of view of in-cylinder combustion caused by sudden load. The vibrations of the engine with the air conditioning on and off at the idle condition were studied experimentally. The results show that when the air conditioning is turned on at low idle speed, the cylinder pressure rise rate increases with the increase of fuel injection. In addition, the combustion pressure in the cylinder also increases, which leads to the increase of engine vibration. At the same time, a spectrum analysis is carried out in terms of the vibration signal in the maximum direction of the vibration intensity of the suspension system, and the vibration isolation rate is calculated. The results show that the vibration intensity at the second order is the largest, and the vibration isolation effect of the rear suspension is poor. [ABSTRACT FROM AUTHOR]

Exhaust gas emissions from ships are an aspect of the global maritime industry which has been given great importance in recent years. Increasing the efficiency of maritime transport regarding fuel consumption and exhaust gas emissions is an ongoing effort which requires a detailed analysis of all ship systems that have an effect on the aforementioned issue. One aspect that can be analyzed in this regard are the various machinery faults which influence the ships exploitation efficiency. This paper will focus on the analysis of the two stroke slow speed diesel main engine with early and late fuel injection faults. This analysis is based on a set of data acquired from a simulation model of a LCC tanker vessel including fuel consumption and emission pollutants such as carbon monoxide (CO), sulphur oxides (SOX) and carbon dioxide (CO2) as a greenhouse gas with early and late fuel injection fault introduced to different number of main engine cylinders. This methodology of research has the advantage of analyzing various scenarios which are not as easily reproduced on actual vessels. [ABSTRACT FROM AUTHOR]

Natural gas has emerged as one of the preferred alternative fuels for vehicles owing to its advantages of abundant reserves, cleaner combustion and lower cost. At present, the gas supply methods for natural-gas engines are mainly port fuel injection (PFI) and direct injection (DI). The transient injection characteristics of a gas fuel injection device, as the terminal executive component of the PFI or DI mode, will directly affect the key performance of a gas fuel engine. Therefore, gas fuel injection devices have been selected as the research object of this paper, with a focus on the transient injection process. To explore the impacts of valve vibration amplitude, period, frequency and velocity on transient injection characteristics, one transient computational fluid dynamics (CFD) model for gas fuel injection devices was established. The findings thereof demonstrated that there is a linear relationship between the instantaneous mass flow rate and instantaneous lift during the vibration process. However, this relationship is somewhat impacted when the valve speed is high enough. A shorter valve vibration period tends to preclude a shorter period of flow-hysteresis fluctuation. The near-field pressure fluctuation at the throat of an injection device, caused by valve vibration, initiates flow fluctuation. [ABSTRACT FROM AUTHOR]

PEM fuel cell systems face highly dynamic load profiles in automotive application. This work showcases the impact of media supply adaption, system architecture and test rig restrictions on the transient voltage response of an automotive fuel cell stack. Current step and load profile experiments were conducted on a system test rig, featuring automotive balance of plant components, and a short stack test bench. A time scale analysis allowed us to identify the predominant effect for the voltage response in each test case. The voltage response measured in the test cases was dominated either by air supply, membrane humidification or coolant temperature dynamics. This systematic comparison of different types of test setups highlights the importance of application-like system level testing as, in contrast to common experiments, different phenomena shape the electrical stack behavior. [ABSTRACT FROM AUTHOR]

High strain piezoceramics are required for various sensor and actuator applications such as opening and closing of valves in fuel injector systems, for controlled flow of fuel in automobiles, applications for micro-propulsion in satellites, and other engineering applications. The precision control of fuel flow in automobiles is necessary for fuel efficiency and pollution control. In this article, lead free piezo systems having higher strain are reviewed with a focus on origin/mechanisms of high strain behavior with critical comments and future directions. Lead zirconate titanate (PZT) delivers linear but low strain of ~0.15% of total length due to the piezoelectric effect. However, lead free piezoceramic material systems such as bismuth sodium titanate (BNT), potassium sodium niobate (KNN), barium zirconate titanate (BZT) etc. deliver high but non-linear strains, as high as 0.79% due to electrostriction. [ABSTRACT FROM AUTHOR]

Hydrogen addition can improve the performance and extend the lean burn limit of gasoline engines. Different hydrogen injection strategies lead to different types of hydrogen mixture distribution (HMD), which affects the engine performance. Therefore, the present study experimentally investigated the effects of hydrogen injection strategy on the combustion and emissions of a hydrogen/gasoline dual-fuel port-injection engine under lean-burn conditions. Four different hydrogen injection strategies were explored: hydrogen direct injection (HDI), forming a stratified hydrogen mixture distribution (SHMD); hydrogen intake port injection, forming a premixed hydrogen mixture distribution (PHMD); split hydrogen direct injection (SHDI), forming a partially premixed hydrogen mixture distribution (PPHMD); and no hydrogen addition (NHMD). The results showed that 20% hydrogen addition could extend the lean burn limit from 1.5 to 2.8. With the increase in the excess air ratio, the optimum HMD changed from PPHMD to SHMD. The maximum brake thermal efficiency was obtained with an excess air ratio of 1.5 with PPHMD. The coefficient of variation (COV) with NHMD was higher than that with hydrogen addition, since the hydrogen enhanced the stability of ignition and combustion. The engine presented the lowest emissions with PHMD. There were almost no carbon monoxide (CO) and nitrogen oxides (NOx) emissions when the excess air ratio was, respectively, more than 1.4 and 2.0. [ABSTRACT FROM AUTHOR]

Highlights: What are the main findings? ABE is an excellent alternative fuel for spark ignition engines ABE fuel enables spark ignition engines to have good power performance and emissions performances What is the implications of the main findings? Gasoline port injection plus ABE direct injection was adopted in this paper In total, an 80% ABE direct injection ratio can obtain excellent power performance at low and medium engine speeds and loads With the further increase in the engine speed and load, pure ABE is optimal to meet power demands A direct injection ratio between 60% and 80% ABE can keep gaseous and particle emissions at low levels ABE plus gasoline combined injection can improve the combustion performance and emission performances effectively ABE can be used as an alternative fuel for engines. This paper studies the combustion and emission performances of an SI engine with GPI plus ABEDI at different engine speeds and loads. The engine operating conditions included speeds of 1000–2600 rpm at the MAP = 50 kPa and loads of MAP = 30–70 kPa at a speed of 1800 rpm. The ABEDIr contained 0%, 20%, 40%, 60%, 80%, and 100%. At speeds = 1000–1800 or 2200–2600 rpm, the testing results showed the ABEDIr corresponding to the maximum IMEP at 80% or 100%. When the ABEDIr = 60%, HC and NOx emissions were the lowest at speeds of 1000–2600 rpm. Meanwhile, NPN and APN both decreased with the increasing of ABEDIr. As the MAP increased, CA0-90 decreased. At different loads, ABE-added fuels had lower HC and NOx emissions and higher IMEP values than pure gasoline. PN was lower than 4 × 104 n/cm3 when the ABEDIr was over 80%. Overall, 80% ABEDIr is a great choice for engine performance at the test range of loads and speeds, and pure ABE fuel is better if the power performance is the main requirement at high speeds and loads. [ABSTRACT FROM AUTHOR]

The present study numerically investigates the use of gas/liquid slug flows for the thermal management of a proton exchange membrane fuel cell (PEMFC). Given that a significant portion of the energy produced by PEMFCs is dissipated as heat, effective thermal management is crucial for enhancing their efficiency and operational stability. To address this, a three-dimensional, multi-phase, and non-isothermal model of a PEMFC is developed using OpenFOAM. The governing equations are discretized using the finite volume method, and the volume of fluid method (VOF) is adopted to capture the gas/liquid interface across the cooling channels. The effect of two-phase cooling is examined on the temperature distribution, water content distribution, proton conductivity, and the current density of the PEMFC for different two-phase Reynolds numbers. Moreover, the thermohydraulic performance of the slug flow is evaluated using a well-defined performance evaluation criterion (PEC). The results indicate that two-phase cooling outperforms single-phase cooling of PEMFC, achieving up to 65 % enhancement in the convective heat transfer coefficient, which leads to a 9.6 % reduction in the membrane temperature. Additionally, PECs up to 1.4 are reported for the slug flows. These enhancements indicate possible uses in automobile fuel cell systems, portable power sources, and backup power systems. This study may stimulate additional research via experimental endeavors and the investigation of novel cooling methodologies. • Thermal management of PEMFC systems using gas/liquid slug flow technique. • Innovative segregated method for the numerical simulations for PEMFC systems. • Convection coefficient improved by up to 65 % compared to single-phase flow. • Slug flow thermal management achieves a PEC of up to 1.4. • New performance criteria for two-phase thermal management in PEMFC systems. [ABSTRACT FROM AUTHOR]

• Annular flow replaces plug flow as new flow pattern under vibrating conditions. • The onset time of slug flow is earlier and its duration is longer under vibration. • Vibration effectively reduces wall superheat. • Vibration promotes occurrence of the onset of nucleate boiling. • Propose a correlation for vibration boiling heat transfer. In automotive fuel cell systems, thermal management plays a key role in maintaining the efficient operation of the cells. As the core component of the fuel cell cooling system, the performance of the micro heat exchanger has a direct impact on the efficiency and lifespan of the fuel cells. When a vehicle runs on rough roads, vibrations are inevitably generated, which can be simplified as sinusoidal vibrations. To further investigate the impact of vibration on heat transfer performance, the flow patterns and boiling heat transfer characteristics in horizontal rectangular microchannels are examined in this study. In the investigation, refrigerant R141b is employed as the working fluid. The experiments are conducted with vibration frequencies ranging from 7 to 21 Hz and vibration amplitudes ranging from 2 to 12 mm. The results highlight three flow patterns in the non-vibrated boiling flow microchannel: bubble flow, slug flow, and plug flow, with plug flow having the greatest impact on flow boiling heat transfer. When the microchannel was subjected to sinusoidal vibrations, plug flow disappeared, and annular flow emerged as a new flow pattern. Vibration stimulated more nucleation sites, causing the onset of nucleate boiling to occur earlier. Moreover, vibration effectively reduced wall superheat and improved convective heat transfer. Compared to non-vibration conditions, heat transfer improved from 5.29 % to 109.89 % as the vibration frequency increased from 7 to 21 Hz at a vibration amplitude of 2 mm. Similarly, heat transfer improved from 5.29 % to 93.25 % as the vibration amplitude increased from 2 to 12 mm at a frequency of 7 Hz. This indicates that vibration has a positive impact on boiling heat transfer. Finally, a heat transfer coefficient calculation model suitable for vibration is established by introducing the vibrational Weber number. This work has significant practical implications for improving the operational reliability of automotive fuel cells. [ABSTRACT FROM AUTHOR]

The increasing use of bioethanol fuel, as a promising carbon-neutral alternative to petroleum-based gasoline, has raised concerns on compatibility issues between bioethanol and the polymer components used in the automotive fuel system. Here, the performance of two commercial glass-fiber reinforced polyamide composites (polyamide 12 (PA12) and an aromatic highly-biobased polyamide (polyphthalamide, PPA)) exposed to a mixture of ethanol and gasoline (E25 fuel), was investigated at high temperature (120 °C). The polyamide matrices showed a fast and remarkably high fuel uptake. The sorbed fuel had a strong plasticizing effect on both materials, as revealed by the large decrease in the glass transition temperature and a 60% decrease in stiffness and strength. The PPA, however, sustained degradation better than the PA12, which experienced swelling-induced surface cracking and oxidation-induced embrittlement. The results suggest that care should be taken when using polyamide composites in ethanol-based fuel applications at this high temperature level. [ABSTRACT FROM AUTHOR]

In recent decades, research on alternative fuel engines is becoming more and more popular. Compressed natural gas (CNG) has the advantages of abundant reserves and a lower cost. It can reduce vehicle emissions relatively quickly and has little impact on the entire transportation infrastructure. As the fourth generation of a gas fuel supply method, gas fuel direct injection (DI) technology can effectively avoid volumetric efficiency reduction and power reduction problems of the port fuel injection (PFI) method. However, the former's mixing path and duration are shortened greatly, which often leads to poor mixing uniformity. In order to improve the in-cylinder mixing uniformity, the in-cylinder mixing process of the CNG-fueled engine is taken as the research object in this study. The computational fluid dynamics (CFDs) models of the mixing process for the PFI and DI modes are established, and their mixing uniformities are compared. Besides, based on the authors' previous research, the influence mechanism of the piston crown shape and fuel injection angle on the mixing process of the CNG DI engine is explored. The results show that the probability distribution frequency (PDF) of the best mixture concentration region (BMCR) is as high as 72% for the PFI mode, which is much higher than for the DI mode. The shorter jet impingement distance of the flat top piston leads to higher turbulent kinetic energy (TKE) intensity, and the in-cylinder mixing uniformity will be improved. When gas fuel is injected into an area with a higher in-cylinder TKE, the average in-cylinder TKE will be higher, and the in-cylinder mixture will be more homogeneous. [ABSTRACT FROM AUTHOR]

The global rush for decarbonization and the more restrictive emission regulations are pushing the research for cleaner powertrains to the transport sector. In this sense, this work contributes with an experimental investigation of the performance and emissions of a single-cylinder SI engine operating under lean-burn hydrogen combustion. Its performance, combustion parameters, exhaust emissions, and indicated efficiency for a wide range of mixture dilutions are then compared to methane under similar engine load conditions. Hydrogen achieved stable combustion up to lambda 3.4, presenting zero CO emission and very low HC emission for all tested operating conditions. Hydrogen operation also presented zero NOx emissions for conditions leaner than lambda 2.2 and 3.0 at 2000 and 3000 rpm, respectively, however, the NOx emissions increase as the mixture is enriched. The high in-cylinder pressure rise rate limited the operation at mixtures richer than lambda 1.3 at 2000 rpm. When compared to methane, the hydrogen allows de-throttle the engine to burn lean mixtures maintaining a proper flame speed, resulting in lower pumping losses, lower pollutants emissions for most of the conditions tested, and higher indicated efficiency, making hydrogen a promising fuel to replace conventional fuels on cleaner SI engines. • H 2 de-throttled operation decreased pumping losses and increased indicated efficiency. • H 2 presented higher indicated efficiency than CH 4 for all operating condition. • H 2 presented zero NOx emissions at λ = 2.2 and 3.0 at 2000 and 3000 rpm, respectively. • H 2 direct-injection ensured knock-safe operation for all tested conditions. • Very lean H 2 mixtures require alternative strategies to shorten combustion duration. [ABSTRACT FROM AUTHOR]

As the most advanced fuel injection system, the common rail system can achieve the flexible control of injection pressure, injection timing and injection rate. Thus, the pressure control strategy of high-pressure common rail system (HPCRS) will be critical for the performance of the diesel engine, as it affects its injection characteristics. In this paper, model in loop (MIL) simulation studies were carried out, a high-precision common rail hydraulic model and analytical rail pressure control strategy based on flow continuity equation were established. The delay of the high-pressure pump was accounted for and included in the proposed strategy, making it more targeted for HPCRS. The delay can be extremely important for high-pressure common rail overshoot especially in variable working condition. Next, the proposed strategy was compared to the traditional PI-based control strategy in both the start-up and transient conditions. Results indicated that the proposed strategy performs better regarding the overshoot, notably improving the control effect (compared to traditional PI-based strategy). The advances of using the proposed strategy primarily include improvements in working conditions with the obvious change in cycle injection quantity and engine speed. Both the proposed control strategy and PI-based strategy can track pressure effectively in various working conditions. [ABSTRACT FROM AUTHOR]

In reactivity-controlled compression ignition (RCCI) engines, the ignition and combustion of premixed low reactive fuel (LRF) such as natural gas (NG) is controlled by the injection of high reactive fuel (HRF) such as diesel fuel during the compression stroke. In this study, the effects of six different input parameters on the performance and emissions of the natural gas/diesel fueled RCCI engine are studied using fractional factorial design (FFD) method, which is one of the design of experiment (DOE) methods. In this method, the effects of the interactions of input parameters, referred to as "factors," on the outputs, referred to as "responses," are investigated. The factors include premixed ratio (PR), start of first injection (SOI1), spray angle (SA), exhaust gas recirculation (EGR), start of second injection (SOI2), and mass fraction of first injection. Sixteen runs were conducted to evaluate the effects of the interaction between input factors on performance and emissions of a RCCI engine using a validated computational fluid dynamics (CFD) model. DOE results indicate that in order to increase gross indicated efficiency (GIE), higher premixed ratio, 85%, with wider spray angle, 150°, is an effective way. Meanwhile, carbon monoxide (CO) and unburned hydrocarbons (UHC) emissions as well as ringing intensity (RI) are decreased at this condition. To reduce NOx emissions, it is beneficial to raise premixed ratio from 55% to 85% or to use 40% EGR, independently. [ABSTRACT FROM AUTHOR]

Biogas has been a promising alternative fuel for IC engines. However, its CO 2 content reduces calorific value and ignitability. The CO 2 fraction of raw biogas can be separated out by various techniques, which are collectively called methane enrichment. The present study explores the effect of methane enrichment on the output parameters of a Homogeneous Charge Compression Ignition (HCCI) engine. A single cylinder CI engine is altered for this purpose. Biogas (CH 4 + CO 2) is supplied along with air. Diethyl Ether (DEE) is used as the secondary fuel to initiate auto-ignition. The effects of injecting DEE at the inlet port and upstream in the intake manifold are also compared. Performance, emission and combustion characteristics such as brake thermal efficiency, equivalence ratio, HC, CO, CO 2 , NO x and smoke emissions, start and duration of combustion, in-cylinder pressure and maximum heat release rate are compared for operation with raw biogas (50% methane) and methane enriched biogas (100% methane) for various biogas flow rates and engine torques. Results show that methane enrichment enhances brake thermal efficiency by up to 2% compared to raw biogas. Methane enrichment advances and speeds up combustion. HC, CO and CO 2 emissions, maximum cylinder pressure and maximum heat release rate are also improved with methane enrichment. Ultra-low NO x and smoke emissions can be obtained using raw biogas as well as methane enriched biogas. Low biogas flow rates provide better brake thermal efficiency and HC emissions. Manifold injection of DEE enhances brake thermal efficiency by up to 2% compared to port injection by virtue of greater mixture homogeneity. • Methane enrichment improves brake thermal efficiency, CO 2 , CO and HC emissions. • Ultra-low NO x and smoke emissions can be obtained using HCCI mode. • 2% improvement in brake thermal efficiency using methane enriched biogas. • Manifold injection of DEE gives better brake thermal efficiency than port injection. • Methane enrichment advances and speeds up combustion. [ABSTRACT FROM AUTHOR]

Opposed rotary piston (ORP) engines can deliver high power density and have few moving parts, being suitable for the power sources of hybrid electric vehicles, range extended electric vehicles, and unmanned aerial vehicles. Hydrogen as a promising alternative fuel is free of carbon emissions during combustion. Hydrogen direct injection avoids the significant power losses of port injection scenarios resulting from the low hydrogen energy density by volume. This paper firstly investigated the ORP engine performance using a 3D numerical simulation method over various hydrogen direct injection strategies (start of hydrogen injection and injection durations). Hydrogen diffusions in combustion chambers, combustion characteristics, engine performance, nitrogen oxides (NO x) emissions, and knock tendency were researched over various hydrogen injection strategies. Hydrogen was unevenly distributed in the combustion chambers for high equivalence ratio scenarios, leading to low combustion efficiency; additionally, the unburned hydrogen was mainly in the cylinder bowls and bottoms. Combustion durations were the shortest within the equivalence ratio range of 0.577–0.865, being approximately 18° crank angle (CA). The maximum in-cylinder pressure was higher than 8.0 MPa over the equivalence ratio of 0.961; and the corresponding heat release rates were higher than 45 J·(°CA)−1. The indicated thermal efficiency was higher than 38%, and it was increased generally by dropping equivalence ratios, with the maximum efficiency being approximately 42.5%. NO x emission factors, approximately 35 g (kW h)−1, reached the maximum value under the equivalence ratio of 0.673 conditions. Knock tendency was decreased continuously by lowering equivalence ratios. This research made a foundation of improving the engine fuel economy and mitigating NO x emissions for hydrogen direct injection ORP engines. • Hydrogen direct injection applied to ORP engines maintains high power density. • Hydrogen injection strategy affects mixture formation and combustion characteristics. • High ER cases had low combustion efficiency due to uneven hydrogen distributions. • Thermal efficiency was increased by low ER due to less heat loss by cylinder walls. • Cylinder bowls were the man regions having high NO x concentration for all the cases. [ABSTRACT FROM AUTHOR]

There is an increasing interest in properly representing local driving patterns. The most frequent alternative to describe driving patterns is through a representative time series of speed, denominated driving cycle (DC). However, the DC duration is an important factor in achieving DC representativeness. Long DCs involve high testing costs, while short DCs tend to increase the uncertainty of the fuel consumption and tailpipe emissions results. There is not a defined methodology to establish the DC duration. This study aims to study the effect of different durations of the DCs on their representativeness. We used data of speed, time, fuel consumption, and emissions obtained by monitoring for two months the regular operation of a fleet of 15 buses running in two flat urban regions with different traffic conditions. Using the micro-trips method, we constructed DCs with a duration of 5, 10, 15, 20, 25, 30, 45, 60, and 120 min for each region. For each duration, we repeated the process 500 times in order to establish the trend and dispersion of the DC characteristic parameters. The results indicate that to obtain driving pattern representativeness, the DCs must last at least 25 min. This duration also guarantees the DC representativeness in terms of energy consumption and tailpipe emissions. [ABSTRACT FROM AUTHOR]

The development of alternative fuels is important in the fight against climate change. Both hydrogen and ammonia are renewable energy sources and are carbon-free combustible fuels. In a recent experimental study, the performance and emission characteristics of a spark-ignition engine burning a premixed hydrogen/ammonia/air mixture were evaluated. The manifold absolute pressure was adjusted to 61 kPa and the engine speed was stabilized at 1300 rpm. The difference between a mixture with a 2.2% volume fraction of ammonia and a pure hydrogen fuel was analyzed in comparison. Specifically, the addition of ammonia increased the ignition delay and flame development periods and reduced the rate of in-cylinder pressure rise. In conjunction with the ignition timing strategy, the addition of ammonia did not affect the engine performance. Nitrogen oxides emissions are increased due to the addition of ammonia. The experimental results suggest that ammonia can be used as a combustion inhibitor, which provides a new reference for the development of hydrogen-fuelled engines. • The effect of ammonia addition on hydrogen-fueled engines was studied. • Direct injection and port injection were used for H 2 and NH 3 respectively. • Reduces the rate of pressure rise after ammonia was added. • The addition of ammonia has little effect on peak IMEP and ITE. [ABSTRACT FROM AUTHOR]

The dynamic of a full-power fuel cell vehicle highly depends on the proton exchange membrane fuel cell power response. However, when frequent load changes in full-power fuel cell vehicle, proton exchange membrane fuel cell air shortage often occurs, leading to its poor power response. Predictive control of proton exchange membrane fuel cell is considered an effective solution, in which its demand power is a key input variable and must be predicted accurately. Proton exchange membrane fuel cell demand power has a strong nonlinear trend, which leads to large prediction errors. This paper proposes a hybrid prediction model that further extracts the data trendiness through the seasonal and trend decomposition using loess method and extracts the global features using the attention mechanism. The proposed prediction model is validated using real data under different driving conditions. Experimental results show that the proposed prediction model captures data characteristics and trendiness well and can better predict proton exchange membrane fuel cell demand power compared to other models. The proposed prediction model provides a prerequisite for improving the proton exchange membrane fuel cell power response and dynamics of full-power fuel cell vehicle. [Display omitted] • A hybrid prediction model for PEMFC demand power is proposed. • Prediction length is determined for different driving conditions. • The STL method is used for efficiently extracting data series trendiness. • Proposed prediction model has better performance than other two models. • PEMFC demand power prediction favors subsequent power response control. [ABSTRACT FROM AUTHOR]