Spark Ignition Engine Research Articles

Engine Performance and Emission Evaluation of Gasoline-Ethanol Fuel Blend in SI Engines Under Various Conditions of Load and Speed

Ethanol fuel is considered a renewable energy source with a lower global warming potential than gasoline. The purpose of this paper is to analyze the emissions and performance of gasoline-ethanol blends in SI engines under various conditions. A computerized 4s, 1cyl, VCR spark ignition engine is used for the tests to measure the performance of Gasoline-Ethanol (GE) blends in particular E-10 (10% ethanol, 90% gasoline). For measuring exhaust emissions as well as performance, regular gasoline fuel is used for the additional tests. Engine performance using ethanol-gasoline blended fuel has been evaluated at different working conditions: 1200–1800 rpm, AFR 0.9, STs 300, CR10:1. When vehicles running on ethanol-gasoline blend indicated a decrease in the amounts of HC, NOx, and CO exhaust gases while 3.9% increase in CO2 emissions as compared to unleaded gasoline fuel. Furthermore, it has been shown that the brake power, torque, specific fuel consumption increases when a Gasoline-Ethanol (GE) blend is used over regular gasoline fuel.

Empirical study on butanol-ethanol-gasoline blends using Artocarpus heterophyllus peel resource for eco-friendly gasoline engine application

Since using current engine fuels contributes to climate change and global warming, there is intense competition to provide an ecologically friendly and less harmful substitute fuel. It proved to be rather feasible to mix engine-designed fuel with alcohol fuel. In this work, the peel of Artocarpus heterophyllus is used to produce the bioethanol. In three ratios—10 % butanol-ethanol + 90 % petrol (BEG10), 20 % butanol-ethanol + 80 % petrol (BEG20), and 30 % butanol-ethanol + 70 % petrol (BEG30)-butanol-ethanol and petrol were mixed in the present work. Using a four-stroke, spark ignition (SI) engine one-cylinder, the effect of the butanol-ethanol-gasoline combination on operational properties was examined and studied. Three test fuels (BEG10, BEG20, and BEG30) were studied in the engine speed range of 2500 rpm to 4500 rpm. The best practical responses found were brake thermal efficiency (43.21 %) and brake-specific fuel consumption (0.23 kg/kWh). The findings showed that more significant concentrations of ethanol-butanol improve the performance characteristics. In the end, engine emission parameters such as hydrocarbon (40 %), carbon monoxide (25 %), and nitrogen oxide (5.88 %) were reduced by the butanol-ethanol combination with petrol. Artificial neural network (ANN) models of multiple regression are used to forecast the engine performance parameters. An ANN model is trained using a database produced from the experimental findings. It shows that the suggested artificial neural network model can provide a precise correlation between input variables and output replies. The input parameters like Speed, Load, and Blend were predicted using the identified model. The R2 (0.9638, 0.9735) value of BTE and BSFC obtained indicated that the neural network approach model generated was more accurate for the prediction process. ANN application is thus a superior forecasting tool for SI engine performance characteristics.

Effect of ignition timing on combustion characteristics and emissions of an X-type rotary engine with the high efficiency hybrid cycle

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.

Numerical Analysis of the Effect of Ethanol-Gasoline Blends on a Single-Cylinder Spark-Ignition Engine Performance and Emissions

— With the rapid increase in the number of vehicles fueled by gasoline plying on the roads, there has been a rising need in the search for alternative fuels, which are more environmental friendly in order to reduce the amount of vehicular exhaust emissions. This can be achieved by using blended mixtures of gasoline with alcoholic fuels among which, ethanol is found to be most suitable due to its easy availability, low costs, safety and low impact on the engine performance. This study aims to investigate the performance of a single-cylinder, four-stroke spark-ignition engine using different ethanol-gasoline blends, namely E0, E10, E20 and E30. The engine's torque, brake power, brake thermal efficiency, brake-specific fuel consumption, and exhaust emissions were analysed using numerical simulation. Results revealed that raising the proportion of ethanol in the fuel mixture resulted in reduced brake power and torque upto 16% as a result of decrease in calorific value of the mixture. The engine's brake thermal efficiency decreased by upto 3% while the brake-specific fuel consumption increased upto 12% with increase in ethanol concentration. Exhaust emissions, including NOx and HC, were found to be influenced by engine speed, with NOx emissions increasing and HC emissions decreasing as speed increased. The study also revealed that increasing ethanol concentration in the fuel resulted in reduced engine exhaust emissions by upto 47% and 10% for NOX and HC emissions respectively. The study concluded that among all the blends used, optimum performance was obtained for E30 blend with reduction in exhaust emissions but at the expense of slight reduction in engine performance.

CFD Simulation of Pre-Chamber Spark-Ignition Engines—A Perspective Review

The growing demand to reduce emissions of pollutants and CO2 from internal combustion engines has led to a critical need for the development of ultra-lean burn engines that can maintain combustion stability while mitigating the risk of knock. One of the most effective techniques is the pre-chamber spark-ignition (PCSI) system, where the primary combustion within the cylinder is initiated by high-energy reactive gas jets generated by pilot combustion in the pre-chamber. Due to the complex physical and chemical processes involved in PCSI systems, performing 3D CFD simulations is crucial for in-depth analysis and achieving optimal design parameters. Moreover, combining a detailed CFDs model with a calibrated 0D/1D model is expected to provide a wealth of new insights that are difficult to gather through experimental methods alone, making it an indispensable tool for improving the understanding and optimization of these advanced engine systems. In this context, numerous previous studies have utilized CFD models to optimize key design parameters, including the geometric configuration of the pre-chamber, and to study combustion characteristics under various operating conditions in PCSI engines. Recent studies indicate that several advanced models designed for conventional spark-ignition (SI) engines may not accurately predict performance under the demanding conditions of Turbulent Jet Ignition (TJI) systems, particularly when operating in lean mixtures and environments with strong turbulence–chemistry interactions. This review highlights the pivotal role of Computational Fluid Dynamics (CFDs) in optimizing the design of pre-chamber spark-ignition (PCSI) engines. It explores key case studies and examines both the advantages and challenges of utilizing CFDs, not only as a predictive tool but also as a critical component in the design process for improving PCSI engine performance.

Influence of variable enhanced LIVC miller cycle coupled with high compression ratio on the performance and combustion of a supercharged spark ignition engine

A novel variable enhanced late intake valve closing (LIVC) Miller cycle with asynchronous valve opening was proposed. Relevant tests were carried out in a supercharged spark ignition (SI) engine with high compression ratio, which mainly included the effects of variable valve timing on performance and combustion characteristics, as well as the comparison with the baseline engine. The purpose of this study was to explore the effect of different intake and exhaust opening timing on the performance and combustion characteristics of the enhanced LIVC Miller cycle with asynchronous valve opening, and further explore the energy saving potential of this Miller cycle. The results showed that the application of variable enhanced Miller cycle effectively improved the anti-knock ability and pumping loss of the engine with high compression ratio. On the one hand, the optimization of pumping loss substantially improved the fuel economy under small load conditions. On the other hand, better combustion performance and air-fuel ratio could be achieved at medium and high loads. Meanwhile, the exhaust valve should be opened as earlier as possible to achieve the best fuel economy. Correspondingly, under optimal valve timing, compared with the baseline engine, the asynchronous intake valve opening variable enhanced Miller cycle engine with high compression ratio had a fuel economy optimization of more than 3.5 % under all loads, and the maximum fuel economy optimization was 12.74 % under the condition of 11 bar.

Optical Investigation of Sparks to Improve Ignition Simulation Models in Spark-Ignition Engines

The use of renewable fuels in place of fossil fuels in internal combustion engines is regarded as a viable method for achieving zero-impact-emission powertrains. However, to achieve the best performance with these fuels, these engines require further optimization, which is achieved through new combustion strategies and the use of advanced ignition systems such as prechambers. Since simulations greatly accelerate this development, accurate simulation models are needed to accurately predict the combustion phenomenon, which requires a deep understanding of the ignition phenomenon as it significantly affects combustion. This work presents a comprehensive experimental methodology to study sparks under engine conditions, providing quantitative data to improve and validate ignition simulation models. The goal was to determine the volume generated by sparks under engine conditions that can initiate combustion and use this information to improve simulation results to match the experimental results. The visible sparks were observed with high-speed cameras to understand their time-resolved evolution and interaction with the flow. The heat transfer from the plasma was also visualized using a modified Background-Oriented Schlieren technique. The information gained from the experimental observations was used to improve an ignition simulation model. Since the velocity of the plasma was found to be slower than the surrounding flow, a user-defined parameter was included to calibrate the velocity of the simulated plasma particles. This parameter was calibrated to match the simulated spark length to the experimental spark length. In addition, since the previous simulation model did not take the heat transfer from the plasma into account, the simulated plasma particles were coupled to have heat transfer to the surroundings. Based on a comparison of the simulation results with the experimental results, the improved approach was found to provide a better physical representation of the spark ignition phenomenon.

A consistent model of the initiation, early expansion, and possible extinction of a spark-ignited flame kernel

Modelling the establishment and growth of spark-ignited (SI) flame kernels has always been a topic of great interest, especially due to their key role in affecting the performance of SI engines. A major issue is that the unsteady conditions and the small kernel size hinder the application of the typical (both linear and non-linear) flame stretch correlations, valid only long after the ignition stage. Overcoming such limitations, this work presents a novel, mathematically consistent, and compact model that enables prediction of flame kernel initiation and early expansion, including its possible extinction. Firstly, spark-driven initiation models from literature are discussed, and an effective flame kernel initiation method is proposed. Then, the expansion model is defined complementing the mass, energy, and species conservation equations for the spherical kernel with the reactant and temperature profiles outside of it using the theory of transient thermodiffusive flames. After accounting for the convective flow caused by the combustion-induced density reduction and the variable thermodynamic properties of the reacting fuel/air mixture, the result is a two-equation model that predicts the kernel expansion even up to its possible extinction due to flame stretch. After calibration of the expansion model, successful validation is achieved against literature data on lean propane/air flames, and the influence of the model parameters is examined in detail. The proposed expansion model is formulated also aiming for inclusion into the simulation of combustion in SI engines, enabling more accurate predictions at part loads, as well as more effective estimation of the cycle-to-cycle variation thanks to the good model sensitivity to the parameters most affecting the ignition.

Effects of Various Bore–Stroke Ratios on Hydrogen Direct Injection Spark Ignition Engines With Variable Valve Timing Under Low-Load Conditions

Effects of Various Bore–Stroke Ratios on Hydrogen Direct Injection Spark Ignition Engines With Variable Valve Timing Under Low-Load Conditions

Effect of Fuel Injection Parameters on Engine Performance in A Conventional Single Cylinder Spark Ignition Engine

In this study, a 1D model was created using the Ricardo-Wave program for a single-cylinder, spark ignition, four-stroke, direct injection engine with a stroke volume of 398 cc. Air-fuel ratio (AFR), mixture temperature (MT), and start of injection (SOI) were used as fuel injection parameters. Using these parameters, 343 different cases were created. Brake power, thermal efficiency, and fuel consumption were used as engine performance parameters. By holding one injection parameter constant, a contour plot was created to examine the effect of the other two parameters on the engine performance parameter. According to the results, the effect of MT and SOI on brake power is 1%, the effect of AFR on brake power is 9.6%, the effect of MT and SOI on thermal efficiency is 1%, and the effect of AFR on thermal efficiency is 12.8%. The effect of MT and SOI on fuel consumption is 0.04%, the effect of AFR on fuel consumption is 22.9%, and the effect of AFR on brake specific fuel consumption is 22.9%. These results indicate that the most significant effect is provided by AFR, while MT and SOI also have a slight impact on engine performance.

RESEARCH OF THE COMBUSTION PARAMETERS OF GASOLINE WITH ADDITIONAL HYDROGEN IN A SPARK-IGNITION ENGINE IN EXTERNAL SPEED CHARACTERISTIC MODES

The directions of development and improvement of road transport around the world are inextricably linked to the desire to reduce the use of cars “on traditional fuels” due to limited oil and environmental safety of mankind. Since the modes of external speed characteristic are the most typical for the operation of cars in cities, the study of environmental performance of engines in these modes is an urgent task. Therefore, finding ways to reduce carbon dioxide emissions from automobile engines at high-speed modes is an urgent task. The rapid growth in the number of cars with internal combustion engines and the inevitable decline in world oil reserves necessitate the development and implementation of energy-saving technologies and the use of alternative fuels. Research aimed at finding ways to improve the fuel efficiency and environmental performance of automotive engines is relevant. One of the promising areas is the influence on the combustion process in gasoline engines by using additives of alternative fuels, which include hydrogen. The presented study of the parameters of combustion of gasoline with hydrogen additive in a spark ignition engine at external speed characteristics is a comprehensive analysis of the combustion process of a gasoline-hydrogen mixture and determination of its effect on the concentration of carbon dioxide in exhaust gases by developing a mathematical model that takes into account the composition of the mixture components and features of the combustion process, allows for sufficiently accurate calculation of the operating process of an engine with hydrogen additive at ψ ≤ 10%, its identification by the results of experiments. In the course of the study, dependencies were developed to determine the combustion parameters of the Wiebe model, taking into account the addition of hydrogen to gasoline in the modes of external speed characteristics, and the effect of hydrogen addition on the concentration of CO2 in exhaust gases was analyzed. It is shown that with an increase in the hydrogen additive to 10% by mass fraction to gasoline, there is a decrease in CO2 emissions to almost 30% in the external speed characteristic modes, which corresponds to modern environmental standards for gasoline internal combustion engines.

The performance of a spark ignition gasoline engine with hydrogen addition under low-load conditions

With continuously increasing populations and industrialization, more and more green consumers and stringent emission regulations promote low-carbon or zero-carbon alternative fuels in transportation sector. Hydrogen is considered carbon-free when produced using environmentally friendly methods, and could achieve zero carbon emission in the internal combustion engines. This study comprehensively explores the influences of the hydrogen addition on the performance of the gasoline spark ignition (SI) engine operated at low-load conditions. The experimental results showed that the abnormal combustion cycles of the test gasoline engine are greatly reduced with hydrogen enrichment. In addition, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) of the gasoline engine is 2.66 % under the 1500 rpm and 0.2 Mpa (brake mean effective pressure: BMEP) condition, while the COV of IMEP of the engine fuelled with gasoline and hydrogen is 2.34 % at the same condition. Furthermore, the knocking intensity of the gasoline engine is strengthened by adding hydrogen because the averaged maximum pressure rise rate (MPRR) of the gasoline SI engine is slightly increased. Besides, the indicated thermal efficiency (ITE) of the gasoline engine is increased 0.9 % and its maximum increase rate of the ITE is 4.27 % with hydrogen addition at the 1300 rpm and 0.2 MPa condition. Last, unburned HC, CO, and CO2 of the gasoline engine are reduced while NOx emissions increase with adding hydrogen due to high combustion temperature.

Effects of hydrogen addition on ignition characteristics and engine performance of ammonia-hydrogen blended fuel: A kinetic analysis

To investigate the effects of hydrogen addition on the ignition characteristics and engine performance of ammonia-hydrogen fuel, a reaction kinetics mechanism suitable for high-pressure engine conditions was proposed. The study explores the influence of hydrogen blending ratios on the ignition delay time (IDT) of ammonia-hydrogen fuel, revealing the sensitive reactions and evolution characteristics of reaction pathways during the ignition process of ammonia-hydrogen fuel promoted by hydrogen. The study also investigates the impact of hydrogen blending ratios on the engine performance of ammonia-hydrogen fuel. The results show that the IDT of ammonia significantly decreases with increasing hydrogen blending ratios and temperature. The addition of hydrogen to ammonia significantly lowers the autoignition temperature boundary of the mixture. Under low-temperature and low-pressure conditions, ammonia, which would not ignite originally, ignites due to the addition of hydrogen. The addition of hydrogen shifts the sensitive reactions of the mixture from NH3 and NH2-related reactions to H2/O2-related reactions, without altering the reaction pathway of ammonia, only changing the pathway flux of components such as NH2, H2NN, H2NO, and HONO. In a spark-ignition (SI) engine, maintaining the total fuel heat value and ignition timing constant, an increase in hydrogen blending ratio significantly raises the peak cylinder pressure. However, due to the forward movement of the heat release process, the power performance of engine experiences varying degrees of reduction. Therefore, it is necessary to delay the ignition timing of engine with the increase in hydrogen blending ratio, moving the combustion center beyond the top dead center (TDC). Furthermore, increasing the hydrogen concentration in the blend significantly raises the temperature and pressure during the engine combustion process, leading to an increase in the concentration of thermal NOX in the emissions.

THE INFLUENCE OF NITROUS OXIDE ADDITION TO THE AIR CHARGE ON THE INDICATORS OF A SPARK IGNITION ENGINE UNDER FULL LOAD OPERATION

The article presents the methodology and research results on the influence of nitrous oxide addition to the air charge on the energy and environmental indicators, as well as the fuel economy of a spark ignition engine with feedback and a three-way catalytic converter under full load conditions. Full load engine modes are often used in conditions of intense traffic of vehicles in cities and settlement. Increasing energy indicators is relevant for sports vehicles and stationary energy installations operating at full load. When determining the most efficient method of achieving high engine energy indicators, it is necessary to take into account the method's impact on the engine's environmental indicators and fuel economy. Several methods for increasing the energy indicators of spark ignition engines are known. One of the most utilized methods is enriching the fuel-air mixture. Engine operation on enriched fuel-air mixture leads to increased gasoline consumption and deterioration of environmental indicators, especially when using a catalytic converter. Therefore, research into methods that simultaneously improve the energy and environmental indicators of the engine in the mentioned operating modes without increasing fuel consumption is relevant. One such method is the use of oxygen-containing compounds, in particular nitrous oxide, added to the air charge. The article proposes a methodology for assessing the method's impact on engine performance indicators in relative terms compared to fuel-air mixture enrichment. We conducted a study of indicator indicators of engine operation, namely: energy indicators based on average indicator pressure, fuel efficiency indicators based on indicator coefficient of useful action, environmental indicators based on concentrations of pollutants in exhaust gases. Calculations using experimental data showed that by adding various amounts of nitrous oxide to the engine's air charge, it is possible to achieve higher energy indicators, improve environmental indicators without worsening fuel economy compared to fuel-air mixture enrichment.

The study on the engine pressure variation of utilizing n-butanol-gasoline blends at fueling spark ignition engines

Abstract Alternative fuel solutions are highly regarded as potential solutions to more emissions regulation as well as more efficient energetic consumption requirements. The more efficient combustion engines become, the lesser resources they require to propel vehicles thus resulting in lower carbon footprint and lower pollutants such as CO, HC and NOx. Alcohols are promising alternative fuels that can be used to fuel vehicles, on their own or in blends with conventional fuels such as gasoline and diesel. A lot of studies have been done on alcohols such as ethanol, butanol and methanol. Each of the mentioned solutions have their advantages and disadvantages. Butanol looks a promising solution due to its high miscibility properties making it possible to blend in higher percentages with other fuels such as gasoline for example. Compared to ethanol, butanol is also less corrosive, making it ideal for older vehicles as well without any modifications to the fuel systems. Many studies have shown that the high oxygen content of butanol can help improve the combustion process in spark ignition engines, may improve thermal efficiency resulting in lower emissions and better overall engine stability. An improved engine stability can be measured by a lower variability between engine cycles during engine functioning. The objective of this paper is to determine the impact of fueling a spark ignition engine with a blend of 15% vol. n-butanol – 85% vol. gasoline on pressure variability and combustion. No engine adjustments/optimizations are done at fueling with the blended fuel vs pure gasoline. The baseline was set at an engine speed of 2500 min-1 and load of 55% while fueling with pure gasoline. After setting the baseline, the same measurements are done at fueling with the blended fuel.

A study on the influence of utilizing hydrogen at fuelling spark ignition engines

Abstract In the last 30 years, remarkable progress has been made in reducing pollutant emissions and fuel consumption in conventional internal combustion engines. Active and passive methods of reducing exhaust emissions have caused them to decrease significantly over the level of the 1980s. However, the problems of air pollution and the greenhouse effect are far from being solved. International organizations and institutions are pushing for measures to reduce emissions, especially the implementation of “zero-emission” (ZEV) vehicles. Due to its excellent combustion properties and the very low pollutant emissions resulting from its combustion, hydrogen is seen as an alternative fuel of the future. Hydrogen can be used as a fuel in two ways: in internal combustion piston engines or in fuel cells. Research into the use of hydrogen as a fuel for spark ignition engines is divided into two directions: additive fuel or a total gasoline substitution with hydrogen. Compared to the gasoline-powered engine, the fully hydrogen-powered engine runs more economically at low loads but it can create a decrease of performance at high loads due to the high volumes of space needed in the combustion chamber. Because of the very low density, high volumes of hydrogen are difficult to storage, requiring also high pressure, so running only on hydrogen wouldn’t be practical. Combining the advantages of the two fuels came the use of gasoline with addition of hydrogen. An important aspect is that emissions are significantly reduced due to the very good combustion properties of hydrogen and the high diffusivity that helps to form a homogeneous mixture. This paper presents aspects of fuelling a spark ignition engine with gasoline and hydrogen. The influence of hydrogen on the cylinder mixture, on the energy and emissions of the engine is analysed. We will focus on: engine power, fuel consumption, the level of pollutant emissions and greenhouse gases, at the studied regimes.

Conversion of a small size passenger car to hydrogen fueling: simulation of full load performance

Abstract Hydrogen offers a valid choice when considering zero emissions transport. This alternative fuel is well suited for spark ignition (SI) engines and it can be implemented with relatively minor changes in terms of added components. Initial evaluations of feasibility with respect to available space for the fuel tank revealed that it is possible to convert a small size passenger car to hydrogen fueling and maintain a range comparable to the fully electric alternative. Peak power assessment showed that additional boosting was required compared to gasoline operation, close to the limit of compressor surge. As a result, the present study extended the engine speed range so as to evaluate full load performance levels that can be obtained when using hydrogen. 0D/1D simulation was applied for simulating power unit output as well as related control parameters. A dedicated laminar flame speed sub-model was implemented for including fuel chemistry effects. Predicted combustion phasing showed the required changes in ignition timing when switching fuels and revealed that the engine could be operated close to stoichiometry when using hydrogen. A reduction of torque was calculated at low engine speed, even if peak power ratings were practically the same as with gasoline fueling.

Experimental for depicting the influence upon gaseous emissions of an Otto engine by using hydrogen as fuel addition

Abstract Due to the higher pollution restrictions implemented globally upon the internal combustion engines, for new but also older vehicles, suitable solutions must be found, for solving major, attested incriminations concerning pollution. The present research focuses on the possibility of the reduction of the emission concentration values emitted by a classic Otto spark ignition engine (Otto ICE), by adding hydrogen to the normal used fuel (gasoline). The hydrogen is generated via a water electrolytic conversion technology, applied, in symbiosis with the internal combustion engine and it is known as hydrogen air (HHA). The hydrogen quantity, as resulted from the HHA generating process and fuelled into the engine, represents 10% (by volume) of the total volume of the intake capacity. Being directly correlated to the stoichiometric ratio used to create the fuel mixture, the intake of hydrogen is finally controlled; therefore, the total calorific power of the new fuel mixtures is increasing by approximate 30%. All the measurements have been achieved in a lab using certified and approved gas analyzers and measurement instruments. The novelty of the research consists of (i) presenting results of measurements with the gas analyzer, one at an engine speed of 800 RPM and the second at 2000 RPM using only gasoline as fuel (normal or standard fuel); (ii) concluding of comparative measurements at the same engine speeds, but with addition of hydrogen in the fuel mixture. Since carbon dioxide makes up the vast majority of greenhouse emissions, the results indicate also a more reduced CO2 concentration in the exhaust. One presents that the electrolytic convertor is capable of producing 1800 litters of HHO gas from 1 litre of water. By upgrading the oxyhydrogen system, one succeeded to produce more HHO gas and replacing the amount of conventional fuel. As conclusions one demonstrated that lower emission values can be obtained with the addition of hydrogen air (HHA).

Investigation on the reduction in unburned ammonia and nitrogen oxide emissions from ammonia direct injection SI engine by using SCR after-treatment system

Currently generated nitrogen oxides (NOx) and unburned ammonia (NH3) can be converted into nitrogen and moisture that are harmless to the human body and environment using selective catalytic reduction (SCR). The concentrations of NOx and unburned NH3 emitted from the ammonia combustion engines are significantly higher than those emitted by engines using existing hydrocarbon fuels. In this study, ammonia, a representative carbon-free fuel, was used in spark ignition engines for existing passenger vehicles to identify the trends in exhaust gases emitted from engines and conduct experiments on after-treatment strategies to reduce NOx and unburned NH3. The addition of oxygen significantly maximized the conversion efficiency of the SCR after-treatment system by changing the concentration of both NOx and NH3 in the exhaust gas.

Optimizing hydrogen spark-ignition engine performance and pollutants by combining VVT and EGR strategies through numerical simulation

Hydrogen combustion engines are considered one of the leading solutions for decarbonizing road transport, mainly due to the possibility of adapting current engines for hydrogen operation with minor changes. This research extensively analyzes the effect of combined EGR (exhaust gas recirculation) and VVT (variable valve timing) strategies on the performance and emissions of a commercial turbocharged SI engine fueled with hydrogen. To this end, a 1D model of the said engine, widely validated for gasoline operation, was adapted to simulate the engine's behavior with hydrogen. This adaptation involved hardware changes and the implementation of a predictive hydrogen combustion submodel, previously calibrated using experimental data from a single-cylinder engine of similar geometry. Firstly, 400 hydrogen engine simulations without EGR were conducted to optimize the VVT system for fuel efficiency over a wide operating range. A detailed explanation of the causality of varying valve overlap on pumping losses, in-cylinder gas composition, and combustion is provided from these simulations. Then, a series of EGR sweeps were simulated to study its impact on performance and NOx at various degrees of load; concluding that diluting with EGR, rather than air, leads to reduced NOx emissions in exchange for slightly increased fuel consumption.