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Hydrogen engines show great potential as a power source with good combustion performance, zero carbon emissions, and diverse sources. However, the exhaust emission characteristics with high water vapor (H 2 O) content have not yet been clarified. This study presents the exhaust emissions of a heavy-duty direct-injection hydrogen engine under various operational parameters, with a focus on the H 2 O content. The results reveal important exhaust emissions characteristics of the hydrogen engine, including lower exhaust temperature (200 °C–400 °C), higher unburned H 2 emissions (up to 17100 ppm), less nitrogen oxide (NO) generation (<1000 ppm), and higher H 2 O content (6%–40%). Additionally, unburned H 2 rises, and NO and H 2 O decrease as the excess air ratio (λ) increases. When λ is greater than 3, NO levels fall sharply to below 100 ppm. Optimal emissions performance is achieved with a 5 °CA BTDC ignition timing where low levels of H 2 , H 2 O, and NO are maintained. Increasing hydrogen injection pressure decreases H 2 but raises exhaust temperature, H 2 O, and NO emissions. Excessively delaying hydrogen injection timing adversely affects the concentration gradient in the cylinder, increasing unburned H 2 emissions. The best emissions performance is observed at a hydrogen injection timing of 110 °CA BTDC. • Studied the exhaust emissions of heavy-duty direct-injection hydrogen engine. • Clarified the high H 2 O and H 2 emission characteristics of hydrogen engines. • Analyzed lower NO emissions and exhaust temperature from hydrogen engines. • Explored the effects of operating conditions on emission characteristics. [ABSTRACT FROM AUTHOR]

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To reduce knock and keeping low NOx emissions and high indicated thermal efficiency (ITE) in a hydrogen fuel engine, the comprehensive effects of ammonia substitution rate (ASR), compression ratio (CR), and ignition timing (IT) on its combustion and its NOx emissions were studied numerically. Based on a four‐cylinder gasoline direct injection (GDI) engine, it was modified into an ammonia/hydrogen dual‐fuel (AHDF) spark ignition (SI) engine. The simulation was conducted by GT‐Power software, and simulation data were validated through experiments. 2500 rpm_50% load was selected for the research. ASR, CR and IT vary from 0% to 20%, 10.5 to 8.5, and −24 to 0°CA ATDC, respectively. The findings indicate that increasing ASR decreases the maximum pressure rise rate (MPRR) and the knock index (KI), improving the ITE, but increasing NOx emissions. Based on 20% ASR, CR was optimized. The findings indicate that decreasing CR reduces the MPRR and KI, but increasing NOx emissions and decreasing the ITE. Finally, based on CR of 9, IT was optimized. The findings indicate that delaying IT reduces the MPRR and KI, but also has a certain impact on NOx emissions and ITE. After compromise consideration, the optimal IT in this study was selected as −9°CA ATDC. [ABSTRACT FROM AUTHOR]

Ammonia is a very promising alternative fuel for internal combustion engines, but there are some disadvantages, such as difficulty in ignition and slow combustion rate when ammonia is used alone. Aiming to address the problem of ammonia combustion difficulty, measures are proposed to improve ammonia combustion by blending hydrogen. A one-dimensional turbocharged ammonia-hydrogen engine simulation model was established, and the combustion model was corrected and verified. Using the verified one-dimensional model, the effects of different ratios of hydrogen to ammonia, different rotational speeds and loads on the combustion performance are investigated. The results show that the ignition delay and combustion duration is shortened with the increase of the hydrogen blending ratio. The appropriate amount of hydrogen blending can improve the brake's thermal efficiency. With the increase in engine speed, increasing the proportion of hydrogen blending is necessary to ensure reliable ignition. In conclusion, the ammonia-hydrogen fuel engine has good combustion performance, but it is necessary to choose the appropriate hydrogen blending ratio according to the engine's operating conditions and requirements. [ABSTRACT FROM AUTHOR]

Green hydrogen has become more attractive as a fuel for engines to reduce greenhouse gas emissions. By mixing it with natural gas (NG), the modification work on the engine can be minimized but the carbon dioxide emissions from combustion can still be decreased. In this paper, an experimental study was accomplished to investigate the performance of a spark-ignition engine fueled with hydrogen-natural gas blends by either keeping a constant ignition timing or changing it. Up to 25 mol-% hydrogen was mixed into natural gases with different compositions and the methane number and Wobbe index were calculated and compared to the requirements set by Euromot. The results show that up to 15 mol-% hydrogen can be blended into NG to meet the limits of Euromot. However, when 25 mol-% hydrogen was mixed into NG the methane number varied between 56 and 64 depending on the gas composition. This would most likely cause knock for a mixture consisting of higher hydrocarbons but during the executed tests knock was never a problem. Furthermore, it was detected that the methane number alone cannot tell the knock tendency of a gas in a certain engine and an additional condition is needed such as the hydrogen level. An adjusted ignition timing was also preferable compared to a constant one to keep the engine component temperature at a moderate level. • A SI-engine was fueled with different hydrogen-natural gas (H 2 -NG) mixtures. • Wobbe index and methane number (MN) were calculated for all test points. • Efficiency was improved and emissions were decreased with higher hydrogen content. • No tendency of knock when 25 mol-% hydrogen was mixed into natural gas with a low MN. • Additional condition is needed for MN eg. H 2 -level to be sure if knock can happen. [ABSTRACT FROM AUTHOR]

Efficient energy exploitation is a necessary issue because it helps reduce fuel consumption and environmental pollution. Finding the optimal ignition timing (IT) for diesel engines to create high power and efficiency deserves attention. This study utilizes AVL BOOST simulation software with the Vibe 2-Zone combustion model to investigate the effect of IT and combustion duration on engine characteristics such as power, torque, and brake-specific fuel consumption (BSFC) at different engine loads and speeds. Then, the prediction models of the optimal ITs versus combustion durations for maximum power and minimum BSPFC were computed. The results show that ITs strongly affect engine performance characteristics. The optimal ITs that the engine produces maximum power at different combustion durations are unaffected by engine load. In contrast, they are considerably influenced by engine load when considering the engine-generated BSFC. The correlations of optimal IT versus combustion duration are linear functions. The prediction models can be utilized to predict the optimal ignition timings of the engine since the experimental time can be reduced when applied to the actual engine.

This study presents an experimental investigation into the impact of blending bioethanol (E100) with conventional gasoline (E0), incrementally increasing biofuel levels up to E10, E50, and E70. The test was carried out in two stages: Stage I assessed the engine's performance under fixed speeds (n = 2000 rpm and n = 2500 rpm) and fixed throttle positions (15%, 20%, and 25%) to measure changes in engine torque, efficiency, and environmental metrics by varying the concentration of bioethanol in the fuel. Stage II aimed to enrich the initial findings by conducting an additional test, running the engine at a fixed speed (n = 2000 rpm) and braking torque (MB = 80 Nm) and varying the ignition timing. Results indicated slight improvements in engine brake torque and thermal efficiency (up to 1.7%) with bioethanol content increased to 70%, and a notable reduction in incomplete combustion byproducts—carbon monoxide and hydrocarbons emissions (up 15% and 43%). Nitrogen oxide emissions were reduced by up to 23%, but carbon dioxide emissions decreased by a mere 1.1%. In order to increase thermal efficiency by adding higher bioethanol blend concentrations, adjusting the ignition timing to counter the longer ignition delay is necessary; however, higher emissions of nitrogen oxides and hydrocarbons are a major drawback of such a strategy. The results of the research are important in determining the optimal concentration of bioethanol in the mixture with gasoline for the energy and environmental sustainability of a spark ignition engine. [ABSTRACT FROM AUTHOR]

Changing the ignition advance angle has a significant impact on the performance of a combustion engine. Optimization of ignition advance angle is a major task of adjusting the engine concerning emission standards, fuel consumption, torque value, etc. The results of the research showed that the process of optimizing the ignition advance curve can noticeably increase engine efficiency, as well as torque and power output from the engine while reducing fuel consumption as a result of lower indications of the air flow mass per second from MAF sensor (mass air flow sensor). The highest impact of the ignition advanced angle modifications can be seen in the area of the highest volumetric efficiency of the tested combustion engine. Almost no impact is observed within high engine speed levels. Simultaneously increasing engine load and rotation speed increases the possibility of engine knocking, which has a devastating effect on engine durability. [ABSTRACT FROM AUTHOR]

Background: Wildfires are thought to become more prevalent during periods of extended dry weather. This issue is examined using two dryness metrics commonly applied in Australian fire management agencies. Aims: This paper investigated links between wildfire incidence and the Keetch–Byram Drought Index (KBDI) and McArthur's Drought Factor (DF) across the state of Victoria, Australia. Methods: Weather records and data from 41 418 wildfires that occurred across the State over a 17-year period were compiled to examine the distributions of KBDI and DF on days with fires smaller and larger than 5 ha in area and all days, using kernel density plots. Key results: Days with fires, particularly days with fires that escaped initial attack, have higher DFs and KBDIs compared with all days. These differences vary between regions and are greatest in areas with moist climates. Conclusions and implications: An appreciation of dryness conditions using tools such as KBDI and DF is useful for understanding fire potential, particularly in areas that experience higher and more regular rainfall. McArthur's Drought Factor and the Keetch–Byram Drought Index are higher than normal on days with fires in Victoria, Australia. These metrics provide a more reliable indication of fire potential in high-rainfall areas than in lower-rainfall areas. This article belongs to the Collection Fire and Climate. [ABSTRACT FROM AUTHOR]

Ammonia is a very promising alternative fuel for internal combustion engines, but there are some disadvantages, such as difficulty in ignition and slow combustion rate when ammonia is used alone. Aiming to address the problem of ammonia combustion difficulty, measures are proposed to improve ammonia combustion by blending hydrogen. A one-dimensional turbocharged ammonia-hydrogen engine simulation model was established, and the combustion model was corrected and verified. Using the verified one-dimensional model, the effects of different ratios of hydrogen to ammonia, different rotational speeds and loads on the combustion performance are investigated. The results show that the ignition delay and combustion duration is shortened with the increase of the hydrogen blending ratio. The appropriate amount of hydrogen blending can improve the brake’s thermal efficiency. With the increase in engine speed, increasing the proportion of hydrogen blending is necessary to ensure reliable ignition. In conclusion, the ammonia-hydrogen fuel engine has good combustion performance, but it is necessary to choose the appropriate hydrogen blending ratio according to the engine’s operating conditions and requirements.

Natural gas (NG) is a potential alternative fuel for carbon neutral and has been received increasing attentions on its combustion behaviors in engine. However, there is little systematic quantitative investigation on the combustion characteristic of purified NG (methane) engine. In this study, the sweeping tests for compression ratio (CR), ignition timing, and hydrogen addition were conducted on a heavy-duty truck liquid methane engine, and the influence factors of ignition delay and combustion rate at each stage were quantitatively investigated. Some new findings and interesting conclusions were obtained. Overall, CR especially the higher CR has small effect on the ignition delay of methane engine (less than 2 deg). Under all the conditions discussed, the ignition delay almost linearly increases with the advance of ignition timing, resulting in the slight advance of start of combustion (SOC). Compared with ignition timing, hydrogen addition has larger effect on SOC since it reduces ignition delay largely (up to 7.3 deg at 1400rpm). By increasing hydrogen addition, the CA10–50 shortens slightly while CA50–90 elongates largely, resulting in a rising trend in CA10–90 finally. All these have extended the research on methane engine and are useful to improve its combustion performance. [ABSTRACT FROM AUTHOR]

Abstract The spark plug of an opposed‐piston two‐stroke (OP2S) gasoline engine is arranged on the side wall of the cylinder liner, far from the center of the combustion chamber; the ignition core of the mixture is offset, the flame propagation distance is increased, the combustion duration is prolonged, and the knock tendency is severe. In this paper, a quasi‐dimensional two‐zone combustion model is used in GT‐Power software to establish a thermodynamic process simulation model and a knock prediction model is included to analyze the effect and matching of the compression ratio, ignition timing, and other thermodynamic process parameters on the knock intensity and engine performance. The extended coherent flame model combustion model is coupled with the Huh–Gosman spray model in AVL‐Fire software, and the An B knock model is used to establish an in‐cylinder combustion model and analyze the flame propagation and the knock response rate of the flat and pit piston during the combustion process. With an increase of the compression ratio, the temperature and pressure of the mixture in the combustion chamber increase at the time of ignition, which leads to the knocking combustion in the cylinder. With an increase of the ignition advance angle, the in‐cylinder pressure and temperature increase rapidly, which increases the likelihood of knocking combustion. In comparison with the pit piston combustion chamber, the flame propagation speed of the flat piston combustion chamber is relatively slow, which increases the knock tendency. The results show that lowering the compression ratio and delaying the ignition can reduce the in‐cylinder knock tendency by setting a compression ratio of 10.5 and an ignition advance angle of 20°CA. When the pit piston is used to organize the squish and inverse squish before and after the inner dead center, the flame propagation process can be promoted. The knock response rate of pit piston is 24.7% lower than that of flat top piston.

This study investigates a direct injection (DI) engine fueled with compressed natural gas (CNG) enrichment with hydrogen blend (HCNG) in counter from the conversion of the port injection gasoline engine. The intention of the investigation was to examine the performance and exhaust gases from the effect of excess air ratio and timing angle changes in consequence of hydrogen increment to natural gas in comparison to gasoline engine performance and exhaust gases as a single fuel. The compression ratio was set at 14:1 with varying load at 3000 rpm, and the ignition timing was applied at −17, −19, −21, and −34°bTDC at WOT, and the amount of hydrogen enrichment to natural gas was applied at 10%, 20%, 30%, and 40%. The conditions on torque, power, heat release rate, brake specific fuel consumption, CO, and NOx were studied. Results showed that the power and torque increased by 8% with increasing the hydrogen content to 40% in fuel composition and advancing ignition timing and heat release rate as well as decreasing λ from 1.4 to 1.2 relative to the stoichiometric state. Also, the specific fuel consumption decreased by 18.5% in the optimal condition. [ABSTRACT FROM AUTHOR]

Hydrogen internal combustion engines (H2-ICEs) have advantages such as clean combustion and zero carbon emissions, and have become one of the important technical routes for decarbonization in the internal combustion engine industry. In this paper, several key factors affecting the performance and emissions of hydrogen internal combustion engines, such as ignition timing, excess air coefficient, and hydrogen injection timing, were systematically studied on a spark ignition multi-point injection (MPI) hydrogen internal combustion engine bench. The experimental results indicate that the ignition timing controls the combustion phase of hydrogen. Moderate early ignition can improve the brake thermal efficiency (BTE) while having little impact on the NOX emissions. Excess air coefficient(λ) can significantly affect the performance and emissions of H2-ICE. Along with the increase of the λ, the NOX emissions first increases and then continues to decline. When the λ reaching 2.1 or above, near zero emissions of NOX can be achieved. The advance of hydrogen injection timing will slightly increase the peak of cylinder pressure and instantaneous heat release rate. However, overall, the impact of hydrogen injection timing on BTE and NOX emissions is not significant on MPI H2-ICE.

HHO gas is a gas produced from electrolysis, which is the decomposition of an electrolyte using an electric current which produces Hydrogen Gas and Oxygen Gas / Hydrogen Hydrogen Oxygen. The purpose of this study was to determine the application of HHO gas by increasing ignition timing by 3º, 6º, and 9º using an aftermarket ECU on engine performance and injection motor emissions. The method used in this study is an experiment, testing using a dinotest measuring instrument and a gas analyzer. The results obtained are the highest average power value in all tests obtained on the variable use of HHO Gas without variations in ignition timing using an aftermarket ECU of 5.90 HP at 3500 Rpm engine speed, an increase of 0.13% from the conditions of HHO Gas usage and forward time. . ignition of 3º and 6º, an increase of 0.27% from HHO gas usage conditions and a forward ignition time of 9º. Then the highest average torque value from all tests was obtained on the variable using HHO Gas and variations in ignition timing using an aftermarket ECU with an advance of 3º of 14.39 Nm at 3000 rpm engine speed, an increase of 0.29% from conditions using HHO Gas without using Variation ignition timing using aftermarket ECU.

In the present investigation, experiments were conducted in wide open throttle condition (WOT) for different speed ranging from 1400 rpm to 1800 rpm at an interval of 200 on a single-cylinder four-stroke port-injected; spark-ignition engine. The engine fueled with equi-volume blend of methanol/gasoline was tested for different ignition timing and its effects on engine characteristics. The experiment results shown, retardation of ignition timing to 14⁰ BTDC exhibits excellent results compared to 24⁰ BTDC ignition timing. The results obtained show a good agreement of improvisation observed with M50 fuel in terms of BTE and BSEC at a speed of 1600 rpm when compared to gasoline fuel. The optimal ignition timing attributes to good combustion efficiency with increasing cylinder pressure and heat release rate. However, low carbon–hydrogen ratio and oxygen content in methanol aids to reduced NOx, HC, and CO emissions by 50%, 35%, and 40%, respectively. The small increase of 10% in CO2 emission is observed; this is due to retardation of ignition time, which allows the M50 fuel to absorb sufficient energy and achieve complete combustion. [ABSTRACT FROM AUTHOR]

An innovative analytical approach combining game theory and particle swarm algorithms is used for the performance optimisation problem of hydrogen engines.An innovative analysis method combining game theory and particle swarm optimization algorithm was adopted to optimize the performance of hydrogen engines. Firstly, the power performance, fuel economy and emission of hydrogen internal combustion engines are studied in detail, and a three-way game model is constructed with the three as the main players, with strategic attribution for ignition timing, hydrogen injection timing and compression ratio.The simulation process of the model is then transformed into numerical optimisation by integrating the game utility function. Finally, the particle swarm algorithm is used to determine the initial set of strategies to obtain the Nash equilibrium solution.The results of the study showed that the optimized hydrogen internal combustion engine improved its power performance by 3.6%; economic efficiency increased by 5.7%; and emissions were reduced by 2% compared to the original engine. • Transforming the optimisation problem of the H2-ICE into a game theoretic problem. • A multi-objective optimization strategy based on game theory is proposed. • Determine the initial set of strategies and find the Nash equilibrium solution using particle swarm algorithm. • The operating parameters of the H2-ICE at variable compression ratios were optimally designed. [ABSTRACT FROM AUTHOR]

The effect of various ignition timing on spark ignition (SI) engines with bioethanol-isooctane mixtures has been widely studied. In the present studies, we used three different ignition angle positions, namely 9°, 12°, and 15° BTDC to increase the combustion pressure in the combustion chamber. In addition to macroscopic observations through engine performance, observations are also carried out from a molecular perspective, i.e.; atomic, bond, and bond angle properties of bioethanol-isooctane fuel. The result shows that more atoms of the isooctane carbon chain are non-rotatable (23 atomic bonds) than the 8 bonds of the bioethanol carbon chain. Furthermore, isooctane also has a wider bond angle (around 121.1745°) than the bond angle of ethanol (around 110.0476°). The unique properties of the atoms in the carbon chains of these two fuels have a direct impact on engine performance. The results show that the viscosity of bioethanol is lower when compared to isooctane, which indicates that the bioethanol molecules are more reactive and flammable. The result also found that at an ignition angle of 12° the BE50 engine has the best performance. Moreover, the test results also show that bioethanol produces clean combustion as evidenced by the lowest CO and HC gas emissions.

The spark plug of an opposed‐piston two‐stroke (OP2S) gasoline engine is arranged on the side wall of the cylinder liner, far from the center of the combustion chamber; the ignition core of the mixture is offset, the flame propagation distance is increased, the combustion duration is prolonged, and the knock tendency is severe. In this paper, a quasi‐dimensional two‐zone combustion model is used in GT‐Power software to establish a thermodynamic process simulation model and a knock prediction model is included to analyze the effect and matching of the compression ratio, ignition timing, and other thermodynamic process parameters on the knock intensity and engine performance. The extended coherent flame model combustion model is coupled with the Huh–Gosman spray model in AVL‐Fire software, and the An B knock model is used to establish an in‐cylinder combustion model and analyze the flame propagation and the knock response rate of the flat and pit piston during the combustion process. With an increase of the compression ratio, the temperature and pressure of the mixture in the combustion chamber increase at the time of ignition, which leads to the knocking combustion in the cylinder. With an increase of the ignition advance angle, the in‐cylinder pressure and temperature increase rapidly, which increases the likelihood of knocking combustion. In comparison with the pit piston combustion chamber, the flame propagation speed of the flat piston combustion chamber is relatively slow, which increases the knock tendency. The results show that lowering the compression ratio and delaying the ignition can reduce the in‐cylinder knock tendency by setting a compression ratio of 10.5 and an ignition advance angle of 20°CA. When the pit piston is used to organize the squish and inverse squish before and after the inner dead center, the flame propagation process can be promoted. The knock response rate of pit piston is 24.7% lower than that of flat top piston. [ABSTRACT FROM AUTHOR]

In this analytical investigation, preheated palm oil was used in the direct injection diesel engine with various optimization methods. The main purpose of the optimization was to get better results than the conventional engine. Raw palm oil was heated using the heat exchange process to reduce the density and viscosity. The relationship between the output process and factors response was evaluated in the design of experiment methods. The Taguchi method is an important method for optimization of the output response performance and emission characteristics of a diesel engine. Two important factors—output and input—were calculated. The input factors considered were preheated palm biodiesel blend, torque, injection pressure, compression ratio, and injection timing. The output factors calculated were smoke opacity, carbon monoxide emission, and brake-specific fuel consumption by using the signal-to-noise (S/N) ratio and analysis of variance. Carbon monoxide was most impacted by torque conditions through injection timing and injecting pressure, and opacity of smoke emission. Among them, injection timing had a higher impact. Different biodiesel blends were prepared: B10 (90% diesel + 10% oil), B20 (80% diesel + 20% oil), B30 (70% diesel + 30% oil) and B40 (60% diesel + 40% oil). Silver nanoparticles (50 ppm) were constantly mixed with the various biodiesel blends. The smoke opacity emission for the biodiesel blend B30 + 50 ppm silver nanoparticle showed the lowest S/N ratio and achieved better optimum results compared with the other blends. The blend B30 + 50 ppm silver nanoparticle showed the lowest S/N ratio value of 9.7 compared with the other blends. The smoke opacity, carbon monoxide emission, and brake-specific fuel consumption of all the response optimal factors were found to be 46.77 ppm, 0.32%, and 0.288 kg/kW·h, respectively. [ABSTRACT FROM AUTHOR]

In the present study, the countermeasures are proposed to minimize the problem on torque and power output performance and exhaust gas emissions of natural gas engine with use of lower calorific gas. An experiment was conducted to identify thermal efficiency and harmful exhaust gas emission characteristics under partial load conditions in order to improve efficient fuel use in engines affected by the introduction of low calorific gases. A countermeasure for coping with emission gas regulations and preventing thermal efficiency deterioration under rated power operating conditions was then presented. An 11 L six-cylinder turbo-charged engine for city buses compliant with the EURO 6 regulation was used in the experiment, and the results obtained using the reference natural gas fuel were compared with those obtained using simulated low calorific gases. Pure methane (CH 4) was also used to investigate the effects of gas composition changes on thermal efficiency and exhaust gas emissions.When N2is added or pure CH 4 is used under partial load operating conditions, the combustion rate decreases; consequently, the optimum ignition timing is additionally advanced relative to that obtained when the reference natural gas fuel is used. If the N2mixing ratio is increased to a minimum of 4.7% under rated power operating conditions, combustion becomes unstable. Stable operation can be secured by increasing the set base fuel amount, 2.35% and 9.41% for pure CH 4 and 8% N2, respectively; however, torque decreases in proportion to the combustion speed of the gas fuel. The strategy of boost pressure control for the torque compensation can minimize the decrease in thermal efficiency.

Natural gas (NG) has many advantages of clean fuels and can replace gasoline in spark ignition (SI) engines. However, it comes with disadvantages such as low energy density. Hydrogen blended NG can improve the fuel characteristics. Ignition timing also plays an important role in engine performance, especially at lean limits. Experiments were conducted for performance and emissions with hydrogen-compressed natural gas (HCNG) blends in a spark ignition (SI) engine with fixed ignition timing. HCNG blends with 0–15% hydrogen were tested with maximum brake torque (MBT) spark timing 30° before top dead center (BTDC) ignition. Significant reduction of carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) along with improved break thermal efficiency was observed with higher hydrogen fraction. There was no significant benefit in indicated thermal efficiency or NOx reduction by using MBT ignition. Hence, the expensive retrofitting of using variable spark timing apparatus can be avoided for on-road vehicles.

For electric reliability and to save energy, the distributed power generation combining cooling and heating supply called a CCHP system for architectures has many potential advantages and is widely adopted to provide electric power and to satisfy local heating and cooling loads by waste heat recovery with low carbon intensity. However, the current CCHP system usually has a fixed ratio of the power and heat due to the features of its power unit, which leads to difficulties in the load management. In this paper, based on the operation of an internal combustion engine fueled with natural gas, a novel method is proposed and studied to achieve a controllable rate of heat/power to meet different load requirements of the electricity and heat (cooling or heating loads). By varying the ignition timing of the spark ignition engine, the combustion process within the cylinder can be adjusted to occur at different crank angles so that the engine crank shaft output power (related to the generated electricity) and the heat from the exhaust gas are changed accordingly. To study the effects of ignition timing on engine power and exhaust heat energy, a two-zone model was established with a predictive combustion model. The changes in the combustion process, output power, exhaust gas temperature, and heat energy were mostly our concern. The results show that the heat/electricity ratio can be adjusted from normally 1.0 to 1.6, and they can be controlled independently under partial load operating conditions. To solve the potential thermal failure of the turbine, the extraordinarily high exhaust temperature will be adjusted by compressed air. [ABSTRACT FROM AUTHOR]

The application of hydrogen fuel in ORP engines makes the engine power density much higher than that of a reciprocating engine. This paper investigated the impacts of combustion characteristics, energy loss, and NOx emissions of a hydrogen-fuelled ORP engine by ignition timing over various equivalence ratios using a simulation approach based on FLUENT code without considering experiments. The simulations were conducted under the equivalence ratio of 0.5~0.9 and ignition timing of −20.8~8.3° CA before top dead centre (TDC). The engine was operated under 1000 RPM and wide-open throttle condition which was around the maximum engine torque. The results indicated that significant early ignition of the ORP engine restrained the flame development in combustion chambers due to the special relative positions of ignition systems to combustion chambers. In-cylinder pressure evolutions were insensitive to early ignition. The start of combustion was the earliest over the ignition timing of −17.3° CA for individual equivalence ratios; the correlations of the combustion durations and equivalence ratios were dependent on the ignition timing. Combustion durations were less sensitive to equivalence ratios in the ignition timing range of −14.2~−11.1° CA before TDC. The minimum and maximum heat release rates were 15 J·(°CA)−1 and 22 J·(°CA)−1 over the equivalence ratios of 0.5 and 0.9, respectively. Indicated thermal efficiency was higher than 41% for early ignition scenarios, and it was significantly affected by late ignition. Energy loss by cylinder walls and exhaust was in the range of 10~16% and 42~58% of the total fuel energy, respectively. The impacts of equivalence ratios on NOx emission factors were affected by ignition timing. [ABSTRACT FROM AUTHOR]

X-type rotary engines (XREs), using the high efficiency hybrid cycle, possess advantages of simple structure, high power-to-weight ratio, and high theoretical efficiency, making XREs as potential power sources in hybrid vehicles and small unmanned aerial vehicles. Typically, ignition timing has a promising potential to improve the combustion performance of spark ignition engines. In this work, the effects of ignition timing on flame propagation, combustion characteristics, and pollutants formation were studied adopting a three-dimensional simulation method. The results showed that at different engine speeds, significantly different flow forms and flow velocities in the larger chamber recess of the XRE were formed, resulting in large differences in flame propagation velocities at leading side and trailing side of the combustion chamber. Advancing ignition timing increased the flame propagation velocity at the given engine speed. Ignition timing had a more significant effect on peak pressure at medium-high speeds compared to low engine speeds. At 3000 RPM and 5000 RPM, the peak pressure was increased significantly with advancing ignition timing, but when ignition timing was advanced to -30 °CA, the increment in the in-housing pressure was minimal. As ignition timing was retarded, the ignition delay was slowly reduced. The effect of ignition timing on ignition delay was more significant for low speeds than for medium-high speeds. However, the influence of ignition timing on combustion duration showed the opposite trend. Delayed ignition showed a slight increase in indicated thermal efficiency and indicated mean effective pressure at low speeds, while the opposite was true at medium-high speeds. Nevertheless, the effect of ignition timing and engine speed on indicated specific fuel consumption is opposite to the trend of the above laws. With the increase of ignition timing, the NOx mass fraction first increased and then decreased at low speeds, with the maximum occurred at -30 °CA, but the NOx mass fraction continued to increase at high speeds. Soot and CO productions were slightly affected by ignition timing. To sum up, this XRE, setting the ignition timing of -30 °CA, achieved better flame propagation and engine performance at the price of a smaller increment of NOx emissions. • The three-dimensional CFD model of the XRE was established and validated. • Effect of ignition timing on combustion characteristics of an XRE was analyzed numerically. • Large differences in flame propagation velocities in the cylinder of the XRE were caused due to larger chamber recess. • Ignition timing had a more significant effect on the ignition delay at low speeds compared to medium-high speeds. • Retarding ignition timing increased ITE and IMEP at low engine speeds. [ABSTRACT FROM AUTHOR]

This study presents a new knock control criterion based on different loads and engine power output loss. By utilizing a modified port fuel injection (PFI) spark-ignition (SI) methanol marine engine, the suppressive effects of retarding ignition timing, reducing air-fuel ratio and delaying injection timing on knock intensity at different loads were investigated. Subsequently, a comparative analysis of three knock control strategies was conducted to determine their impacts on power output and thermal efficiency, thus proposing the optimal knock control strategy at different loads. The results show that at both low load (MAP = 73 kPa) and high load (MAP = 139 kPa), the high knock intensity in KLSA (knock-limited spark advance) +5 case is reduced to the safety limitation by retarding ignition timing and reducing air-fuel ratio, while retarding injection timing can effectively suppress knock only at low load. Furthermore, under KLSA+5 condition, there is a significant increase in the probability of severe knock for CA05 earlier than the knock boundary. As the knock tendency is mitigated, IMEP reduces monotonically. There is lower power output loss by optimizing injection timing and air-fuel ratio at low load, and optimizing ignition timing at high load, while the air dilution strategy consistently results in minimal thermal efficiency loss. • The effects of ignition timing, air dilution, and injection strategy on knock suppression are investigated. • The comparative analysis of combustion characteristic under three control strategies is conducted. • Delaying injection timing and decreasing air-fuel ratio at low load obtain the smaller power loss under knock limit. • For high load, retarding ignition timing can maintain minimal power loss within knock limitation. • A new knock control criterion is proposed. [ABSTRACT FROM AUTHOR]

As a hydrogen carrier, ammonia can suppress knock and enhance thermal efficiency of the hydrogen-fueled Wankel rotary engine (WRE), and achieve zero carbon emissions. This research established a three-dimensional fluid dynamics model coupled with detailed reaction kinetics of ammonia and hydrogen and verified it based on experiments. Incorporating 10% volume fraction of ammonia into the hydrogen-fueled WRE eliminates knock and decreases the excess air ratio (λ) from 1.8 to 1.4, effectively improving the indicated mean effective pressure (IMEP). The results indicate that when λ exceeds 1.4, flame propagation accelerates with higher concentration of the mixture. This enhances peak in-cylinder pressure and heat release rate, but it results higher NOx emissions. As λ varies from 1.8 to 1.4, NOx emission levels rise by 47.4%. At λ ≤ 1.2, the rapid flame propagation leads to short combustion duration, diminishing the power output. At this stage, the NO formation is dominated by H radicals, and the NOx production reaches its minimum value at λ of 1.0. In summary, the ammonia-hydrogen WRE achieves optimal performance at λ of 1.4 and ignition timing of −5 °CA after top dead center, the indicated thermal efficiency reaches 36.9% and the IMEP achieves 0.683 MPa. • The effect of ammonia addition on hydrogen-fueled WRE is analyzed. • The addition of ammonia is an effective way to prevent abnormal combustion. • The effects of excess air ratio on combustion and emission are analyzed. • The optimum ignition timing corresponding the optimal performance is given. • The optimum IMEP and ITE is obtained when the excess air ratio equals 1.4. [ABSTRACT FROM AUTHOR]

The hydrogen-fueled Wanke rotary engine is a promising power system that has both high power and eco-friendly properties. This work investigated the effect of ignition timing on a dual-spark plugs synchronous-ignition hydrogen-fueled Wankel rotary engine under low speed, part load and lean combustion. The results show that with delaying the ignition timing, CA0-10 is shortened first and then lengthened and CA10-90 is consistently shortened. When the CA50 is located between 35 and 40°CA ATDC, the maximum brake torque can be realized. Besides, the selection of ignition timing needs to consider the "trade-off" relationship between the combustion phase and corresponding in-cylinder pressure. The maximum brake torque ignition timing is between 5 and 10°CA ATDC. And there is also a "trade-off" relationship between stability and thermal load when ignition timing is selected. In addition, HC and NO emissions will not become the problem limiting the power performance of hydrogen-fueled Wankel rotary engine under this operating condition. • A modified synchronous ignition hydrogen Wankel rotary engine was used. • The effect of ignition timing on performance of rotary engine was studied. • The power depends mainly on the in-cylinder pressure near 135°CA ATDC. • Selecting ignition timing needs to weigh the stability and thermal load. • Suitable ignition timing makes CA50 located between 35 and 40°CA ATDC. [ABSTRACT FROM AUTHOR]

Hydrogen can be used as a fuel for internal combustion engines to realize a carbon-neutral transport society. By extending the lean limit of spark ignition engines, their efficiency, and emission characteristics can be improved. In this study, stratified charge combustion (SCC) using monofueled hydrogen direct injection was used to extend the lean limit of a spark ignition engine. The injection and ignition timing were varied to examine their effect on the SCC characteristics. An engine experiment was performed in a spray-guided single-cylinder research engine, and the nitrogen oxide and particulate emissions were measured. Depending on the injection timing, two different types of combustion were characterized: mild and hard combustion. The advancement and retardation of the ignition timing resulted in a high and low combustion stability, respectively. The lubricant-based particulate emission was attributed to the in-cylinder temperature and area of the flame surface. Therefore, the results of the study suggest that the optimization of the hydrogen SCC based on the injection and ignition timing could contribute to a clean and efficient transport sector. [ABSTRACT FROM AUTHOR]

Hydrogen internal combustion engines (ICE) will play an important role in reducing carbon emissions, but low power density and abnormal combustion problems are the main obstacles restricting the promotion of hydrogen ICE. Ammonia is a low-reactivity renewable fuel. The purpose of this study is to study the effect of different ammonia-added volume fractions on hydrogen ICE. In this experimental study, the combustion and emission characteristics of an engine fueled by a hydrogen/ammonia mixture were evaluated at part-load operating conditions. The experiment was carried out on a modified engine, the engine speed was 1300 rpm, the absolute pressure of the manifold was 61 kPa, and the volume fraction of ammonia added was 5.2%, 7.96%, and 10.68%, respectively. The test results show that the addition of ammonia changes the combustion characteristics of hydrogen. As the volume fraction of ammonia added increases, the flame development period and flame propagation period are both prolonged, and the peak heat release rate decreases. The addition of ammonia increases the power of the engine and reduces the indicated thermal efficiency. At the ignition timing of the maximum braking torque, as the volume fraction of ammonia added increases, the indicated mean effective pressure and indicated thermal efficiency increase. Adding ammonia volume fraction has little effect on Nitrogen oxides (NOx) emissions, and NOx emissions gradually increase with the delay of ignition timing. • Study the effect of ammonia addition on hydrogen-fueled engines. • The addition of ammonia improves the IMEP of hydrogen-fueled engines. • The addition of ammonia reduces the heat release rate of hydrogen-fueled engines. • Ammonia addition fraction has less effect on NOx emission. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) is a carbon-free fuel with many excellent combustion characteristics, but abnormal combustion is one of the main obstacles to the promotion and application of hydrogen-fueled engines. This experimental study aims to investigate the suppression of the heat release rate (HRR) of a hydrogen-fueled engine through the addition of ammonia (NH 3). The engine was run at 1300 rpm, with manifold absolute pressure (MAP) of 61 kPa and NH 3 addition ratio of 0% and 2.2%, under lean-burn conditions. The results showed that the addition of small amounts of ammonia reduced the combustion rate of the fuel mixture, prolonged the flame development period (CA0-10) and propagation durations (CA10-90) of the engine, and reduced the peak in-cylinder pressure and peak HRR under lean-burn conditions. The addition of ammonia increased the peak indicated mean effective pressure (IMEP) and the peak indicated thermal efficiency (ITE) of the engine. The addition of ammonia resulted in increased nitrogen oxides (NOx) emissions. • The effect of ignition timing of an H 2 /NH 3 dual-injection engine was studied. • Reduces the peak heat release rate after ammonia was added. • CA0-10 and CA10-90 were extended after ammonia was added. • The peak IMEP and ITE were increased after ammonia was added. [ABSTRACT FROM AUTHOR]

Natural gas (NG) has many advantages of clean fuels and can replace gasoline in spark ignition (SI) engines. However, it comes with disadvantages such as low energy density. Hydrogen blended NG can improve the fuel characteristics. Ignition timing also plays an important role in engine performance, especially at lean limits. Experiments were conducted for performance and emissions with hydrogen-compressed natural gas (HCNG) blends in a spark ignition (SI) engine with fixed ignition timing. HCNG blends with 0–15% hydrogen were tested with maximum brake torque (MBT) spark timing 30° before top dead center (BTDC) ignition. Significant reduction of carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) along with improved break thermal efficiency was observed with higher hydrogen fraction. There was no significant benefit in indicated thermal efficiency or NOx reduction by using MBT ignition. Hence, the expensive retrofitting of using variable spark timing apparatus can be avoided for on-road vehicles. [ABSTRACT FROM AUTHOR]

Abstract Biodiesels produced from various feedstocks have been considered as alternative fuels used in internal combustion engines without major modifications. This research focuses on producing biodiesel from waste cooking oil (WCOSD) by the catalytic cracking method using MgO as the catalyst and comparing the engine operating characteristics of the test engine when using WCOSD and traditional diesel (CD) as test fuels. As a result, the brake power of the test engine fueled WCOSD, and traditional diesel is similar. However, the engine fuel consumption in the case of using WCOSD is slight increases in some operating conditions. Also, the nitrogen oxides emissions of the test engine fueled WCOSD are higher than those of CD at all tested conditions. The trend is opposite for hydrocarbon emission as the HC emission of the engine fueled by WCOSD reduces 26.3% on average. The smoke emission of the test engine in case of using WCOSD is lower 17% on average than that of CD. However, the carbon monoxide emissions are lower at the low and medium loads and higher at the full loads. These results show that the new biodiesel has the same characteristics as those of commercial biodiesel and can be used as fuel for diesel engines.

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]

Hydrogen/natural gas blends fuel is considered one of the ideal alternative fuels for improving the thermal efficiency and reducing carbon emissions of rotary engine. In order to further enhance the combustion and power performance of rotary engine, a new method of the setting of bluff bodies in the cylinder was proposed. The influence of bluff-body settings in the cylinder on the combustion, power performance, and NO generation was numerically studied under different ignition timings. The results indicated that in-cylinder bluff-body settings could influence flame propagation by affecting the turbulent kinetic energy and mixture distribution during the process from the late compression stroke to the combustion stroke. Further, for any fixed bluff-body shape in the cylinder, there is a trade-off relationship between the non-blockage ratio and squish velocity at the cylinder block center section as the ignition timing is progressively advanced or delayed. Consequently, considering the above trade-off relationship, the triangular slotted bluff-body in combination with an ignition timing of 30° CA (BTDC) could be used to achieve the maximum improvement in the combustion and power performance of rotary engine. The peak pressure exhibited a growth of 4.83%, and the indicated mean effective pressure increased by 1.46%. • Using hydrogen/natural gas blend fuel to reduce carbon emissions from the rotary engine. • A novel in-cylinder bluff-body structure in the rotary engine is proposed. • Systematic study of in-cylinder bluff-body effects on the combustion process. • A trade-off relationship influenced by the bluff body is identified. • The optimal structure of the bluff-body is provided for improving performance. [ABSTRACT FROM AUTHOR]

The Miller cycle has significant advantages of suppressing knocking and improving nitrogen oxide (NO X) emissions without the penalties of reducing engine fuel consumption and power output. In the study, the effect of non-Miller cycle and Miller cycle on the exhaust gas recirculation (EGR) introduction capability and the knocking boundary were evaluated on a stoichiometric combustion natural gas engine at three different loads. Additionally, the effect of Miller cycle coupled EGR and ignition timing on engine performance and combustion process was discussed. The results indicate that, for the same condition, the Miller cycle could reduce peak temperature and pressure, increased combustion duration, and delayed combustion phase, which makes for effective knocking suppression. Therefore, the Miller cycle has less dependence on the EGR strategy to control knock. Moreover, the Miller cycle can also reduce the ability to introduce EGR, which could up to 3.8%. By matching the ignition timing and EGR rate, the BSFC of the Miller cycle were decreased by 0.6g/kW·h, 2.4 g/kW·h and 2.9 g/kW·h respectively for three test conditions compared with non-Miller cycle. In terms of emissions, the Miller cycle and EGR can both suppress NO X emissions, while the EGR being more effective. The study will provide valid information for the application of the Miller cycle to achieve efficiency clean combustion of natural gas engine. • The effect of different cycles on the boundary parameters of the engine is compared. • The effect of the Miller cycle on the combustion process of the engine is investigated. • The potential for optimizing fuel economy and improving NO X emissions of Miller cycle coupled EGR is explored. [ABSTRACT FROM AUTHOR]

For electric reliability and to save energy, the distributed power generation combining cooling and heating supply called a CCHP system for architectures has many potential advantages and is widely adopted to provide electric power and to satisfy local heating and cooling loads by waste heat recovery with low carbon intensity. However, the current CCHP system usually has a fixed ratio of the power and heat due to the features of its power unit, which leads to difficulties in the load management. In this paper, based on the operation of an internal combustion engine fueled with natural gas, a novel method is proposed and studied to achieve a controllable rate of heat/power to meet different load requirements of the electricity and heat (cooling or heating loads). By varying the ignition timing of the spark ignition engine, the combustion process within the cylinder can be adjusted to occur at different crank angles so that the engine crank shaft output power (related to the generated electricity) and the heat from the exhaust gas are changed accordingly. To study the effects of ignition timing on engine power and exhaust heat energy, a two-zone model was established with a predictive combustion model. The changes in the combustion process, output power, exhaust gas temperature, and heat energy were mostly our concern. The results show that the heat/electricity ratio can be adjusted from normally 1.0 to 1.6, and they can be controlled independently under partial load operating conditions. To solve the potential thermal failure of the turbine, the extraordinarily high exhaust temperature will be adjusted by compressed air.

High power density of opposed rotary piston (ORP) engines provides a possibility for the applications to hybrid vehicles. Under real driving conditions, internal combustion engines as the power sources of hybrid vehicles run under part load conditions in majorities of operation time. Hydrogen applications in internal combustion engines will promote zero-carbon travel, contributing to alleviating global warming. In this investigation, 3D numerical simulations were conducted to explore the performance of an ORP engine fuelled with hydrogen under part load and various ignition timing conditions. The results indicated that peak in-cylinder pressure and corresponding crank angle (CA) changed slightly within the early ignition range of −20.85º CA~ −14.23º CA; peak in-cylinder pressure was decreased significantly by late ignition. Heat release rates were more sensitive to late ignition than early ignition. Start of combustion, combustion phase, and combustion durations presented minor impacts by early ignition and engine loads. Ignition timing of −20.85º CA~ −11.06º CA showed limited impacts on indicated mean effective pressure and indicated power over individual intake manifold pressure. Indicated thermal efficiency was around 40% for the ignition timing of −20.85º CA~ −11.06º CA over the intake manifold pressure of 0.8 bar; indicated thermal efficiency drop caused by ignition timing of −8.33º CA was higher than 7% compared with optimal conditions. Heat loss by cylinder walls in proportions of fuel energy was lower than 25%, 20%, 18% for the intake manifold pressure of 0.4 bar, 0.6 bar, 0.8 bar respectively. Energy loss by the exhaust was higher than 41% for all the scenarios, with the maximum value being approximately 57%. Nitrogen oxides (NO x) emission factors were higher than 11 g (kW h)−1, and they were increased significantly by early ignition. [Display omitted] • Spark plugs layout led to special combustion characteristics and engine performance. • In-cylinder pressure evolutions were dependent less on early ignition timing. • Combustion durations presented the smallest value over ignition timing of −11.06º CA. • Exhaust energy accounted for higher than 41% of the total fuel chemical energy. • NO x were higher than 11 g (kW h)−1, being increased greatly by early ignition. [ABSTRACT FROM AUTHOR]

Alcohol-based fuels are slowly emerging as most promising alternative fuel. Among different alcohols, diethyl ether (DEE) appears to have the largest potential to be used as fuel. In this study, a constant speed, diesel engine was tested for the change in its performance when fueled with diesel – diethyl ether blends. Three blends of diethyl ether and diesel, DEE6 (6% diethyl ether and 94% diesel), DEE8 (8% diethyl ether and 92% diesel), and DEE10 (10% diethyl ether and 90% diesel) were used for the experimentation. Full factorial experiments were conducted by varying engine compression ratio and injection timing. The results reveal improvement in engine performance with the compression ratio of 19:1 for the blends. The oxides of nitrogen emission was highest and the smoke, unburned hydrocarbon and carbon monoxide emissions were lowest. Engine operation with DEE8 at 21°bTDC and 19:1 compression ratio gave a thermal efficiency improvement of 6.15%, and smoke, HC and CO reduced by 14.3%, 25% and 20.93%, respectively. For finding the best parameters for operating the engine, Fuzzy logic-based Taguchi method was applied. The results show that the best parameters for operating the engine are 21°bTDC injection timing and 19:1 compression ratio. [ABSTRACT FROM AUTHOR]

Penelitian ini bertujuan untuk: (1) Mendeskripsikan bagaimana sensor-sensor dalam sistem EFI bekerja pada putaran idle, mesin rotasi tingkat menengah dan tinggi, dengan melihat sensor output. (2) Mengetahui pekerjaan aktuator pada Sistem EFI pada putaran idle, mesin rotasi tingkat menengah dan tinggi. Metode eksperimen digunakan untuk penelitian ini. Mesin EFI dengan tipe D EFI yang digunakan telah dianalisis. Alat pindai digunakan untuk mengamati untuk mengukur output yang dihasilkan oleh sensor dan mengukur kerja aktuator sistem EFI menggunakan alat Pindai. Dari percobaan ditemukan bahwa peningkatan putaran mesin akan menghasilkan peningkatan kerja aktuator pada Sistem EFI, yang terdiri dari Injeksi Waktu dan Pengisi Waktu Pengapian, tetapi untuk Idle Speed ​​Control Valve (ISCV) dan Intake Camshaft Timing perubahan relatif stabil.