Concept of twining injector system for spark-ignition engine fueled with syngas-biogas-hydrogen operating in solar-biomass hybrid energy system

This paper presents the research results on an innovative concept of a twining injector system to supply a flexible syngas-biogas-hydrogen blend for engines working in a hybrid solar-biomass renewable energy system. The effects of nozzle diameter, injection pressure and nozzle location were considered. Simulation results showed that the twining injector system, including 2 injectors with a nozzle diameter of 5 mm located close to the inlet port and 1-bar injection pressure is suitable for Honda GX200 engine fueled with syngas-biogas-hydrogen. At engine speed of 3000 rpm, for syngas-biogas blend, the injection duration of the first injector is reduced from 120 CA to 23 CA while the second injector keeps the injection duration stable at 120 CA to 50% biogas, then reduced to 74 CA for full biogas injection. For syngas-hydrogen blend, the first injector keeps the stable injection duration of 120 CA to 50% hydrogen, then gradually decreases to 44 CA, corresponding to 100% hydrogen; the injection duration of the second injector decreases from 120 CA to 24 CA and then keeps constant until hydrogen content reaches 70%. The injection duration of each injector for syngas-biogas-hydrogen blend is within the limits between the injection duration of the syngas-biogas and that of the syngas-hydrogen blends. The mixture of syngas-biogas-hydrogen blend and air in the combustion chamber created by twining injector system was more homogeneous than that created by traditional port fuel injection system.     

Engine speed and air-fuel ratio effect on the combustion of methane augmented hydrogen rich syngas in DI SI engine

The main challenge on the fueling of pure hydrogen in the automotive vehicles is the limitation in the hydrogen separation from the product of steam reforming and gasification plants and the storage issues. On the other hand, hydrogen fueling in automotive engines has resulted in uncontrolled combustion. These are some of the factors which motivated for the fueling of raw syngas instead of further chemical or physical processes. However, fueling of syngas alone in the combustion chamber has resulted in decreased power output and increased in brake specific fuel consumption. Methane augmented hydrogen rich syngas was investigated experimentally to observe the behavior of the combustion with the variation of the fuel-air mixture and engine speed of a direct-injection spark-ignition (DI SI) engine. The molar ratio of the high hydrogen syngas is 50% H₂ and 50% CO composition. The amount of methane used for augmentation was 20% (V/V). The compression ratio of 14:1 gas engine operating at full throttle position (the throttle is fully opened) with the start of the injection selected to simulate the partial DI (180° before top dead center (BTDC)). The relative air-fuel ratio (λ) was set at lean mixture condition and the engine speed ranging from 1500 to 2400 revolutions per minute (rpm) with an interval of 300 rpm. The result indicated that coefficient of variation of the indicate mean effective pressure (COV of IMEP) was observed to increase with an increase with λ in all speeds. The durations of the flame development and rapid burning stages of the combustion has increased with an increase in λ. Besides, all the combustion durations are shown to be more sensitive to λ at the lowest speed as compared to the two engine speeds.     

Experimental investigations on the effect of fuel injection parameters on diesel engine fuelled with biodiesel blend in diesel with hydrogen enrichment

Fuel injection pressure and injection timing are two extensive injection parameters that affect engine performance, combustion, and emissions. This study aims to improve the performance, combustion, and emissions characteristics of a diesel engine by using karanja biodiesel with a flow rate of 10 L per minute (lpm) of enriched hydrogen. In addition, the research mainly focused on the use of biodiesel with hydrogen as an alternative to diesel fuel, which is in rapidly declining demand. The experiments were carried out at a constant speed of 1500 rpm on a single-cylinder, four-stroke, direct injection diesel engine. The experiments are carried out with variable fuel injection pressure of 220, 240, and 260 bar, and injection timings of 21, 23, and 25 °CA before top dead center (bTDC). Results show that karanja biodiesel with enriched hydrogen (KB20H10) increases BTE by 4% than diesel fuel at 240 bar injection pressure and 23° CA bTDC injection timing. For blend KB20H10, the emissions of UHC, CO, and smoke opacity are 33%, 16%, and 28.7% lower than for diesel. On the other hand NOx emissions, rises by 10.3%. The optimal injection parameters for blend KB20H10 were found to be 240 bar injection pressure and 23 °CA bTDC injection timing based on the significant improvement in performance, combustion, and reduction in exhaust emissions.     

Effect of fuel injection timing of hydrogen rich syngas augmented with methane in direct-injection spark-ignition engine

The product of gasification of solid biomass, also called syngas is believed to be good fuel for internal combustion engines in the move from the carbon based fuel to zero emission fuels. The only problem is its lower calorific value which is placed at one third of that of compressed natural gas (CNG). There are latest efforts to enhance the hydrogen rich syngas by augmenting it with methane so that the calorific value can be improved. This paper presents experimental results of the effect of the start of fuel injection timing (SOI) on the combustion characteristics, performance and emissions of a direct-injection spark-ignition engine fueled with a 20% methane augmented hydrogen rich syngas of molar ratio of 50% H₂ and 50% CO composition. The engine was operated at fully open throttle and the start of fuel injection (SOI) was varied at 90, 120 and 180° before top dead center (BTDC). The experiment was conducted at lean mixture conditions in the low and medium engine speed ranges (1500–2400 RPM). The spark advance was set to the minimum advance for a maximum brake torque in all the test parameters. The methane augmented hydrogen rich syngas was observed to perform well over wide range of operation with SOI = 180°CA BTDC. However, SOI = 120°CA BTDC performed well at lower speeds recording improved performance and emissions. Limitation of operable load was observed for both SOI = 120°CA BTDC and 90°CA BTDC due to an insufficient time for complete injection of fuel at lower relative air–fuel ratio (λ) with higher speeds.     

Modeling study on the production of hydrogen/syngas via partial oxidation using a homogeneous charge compression ignition engine fueled with natural gas

The production of hydrogen and syngas from natural gas using a homogeneous charge compression ignition reforming engine is investigated numerically. The simulation tool used was CHEMKIN 3.7, using the GRI-3 natural gas combustion mechanism. This simulation was conducted on the changes in hydrogen and syngas concentration according to the variations of equivalence ratio, intake temperature, oxygen enrichment, engine speed, initial pressure, and fuel additives with partial oxidation combustion. The simulation results indicate that the hydrogen/syngas yields are strongly dependent on the equivalence ratio with maxima occurring at an optimal equivalence ratio varying with engine speed. The hydrogen/syngas yields increase with increasing intake temperature and oxygen contents in air. The hydrogen/syngas yields also increase with increasing initial pressure, especially at lower temperatures, yet high temperature can suppress the pressure effect. Furthermore, it was found that the hydrogen/syngas yields increase when using fuel additives, especially hydrogen peroxide. Through the parametric screening studies, optimum operating conditions for natural gas partial oxidation reforming are recommended at 3.0 equivalence ratio, 530 K intake temperature, 0.3 oxygen enrichment, 500 rpm engine speed, 1 atm initial pressure, and 7.5% hydrogen peroxide.     

热裂解生物质气发动机燃烧特性试验

利用农林废弃物可控热裂解产生的生物质气作为火花点火发动机的燃料,测最火花点火生物质气发动机的示功图,分析了生物质气的燃烧放热特性.试验结果表明:发动机怠速点火性能较好,小功率时放热速度较慢,大功率时燃烧速度较快,燃烧较充分;火焰发展期随点火提前角的增大而变长,燃烧相位角随点火提前角、负荷的增大而提前,速燃期随负荷的增加、点火提前角的增大逐渐缩短;生物质气中的氢含量加快了生物质气发动机的燃烧速度.     

An investigation on effect of in-cylinder swirl flow on performance,combustion and cyclic variations in hydrogen fuelled spark ignition engine

This study investigates how engine performance, cyclic variations and combustion parameters are affected by swirling flow in hydrogen spark ignition (SI) engine. Swirling flow was produced in the cylinder during the induction stroke by intake port having entry angles of 0°, 10°, 20° and 30°. In addition, tumble angle of 8° was positioned for given entry angles. The engine was operated under lean mixture (ϕ = 0.6) conditions and engine speeds of 1400, 1600 and 1800 rpm. As a result, it was found that swirling flow enhances performance of hydrogen SI engine around 3% when operating engine with entry angle of 20°. The combustion duration and the cyclic variation in hydrogen SI engine can be reduced with optimum swirling flow. The stability of combustion in hydrogen SI engine is mainly dependent on cyclic variations in the flame initiation period and the cyclic variations in this period can be reduced with controlled swirling flow.     

CFD analysis of hydrogen injection pressure and valve profile law effects on backfire and pre-ignition phenomena in hydrogen-diesel dual fuel engine

This paper focuses on optimizing the hydrogen TMI (timed manifold injection) system through valve lift law and hydrogen injection parameters (pressure, injection inclination and timing) in order to prevent backfire phenomena and improve the volumetric efficiency and mixture formation quality of a dual fuel diesel engine operating at high load and high hydrogen energy share. This was achieved through a numerical simulation using CFD code ANSYS Fluent, developed for a single cylinder hydrogen-diesel dual fuel engine, at constant engine speed of 1500 rpm, 90% of load and 42.5% hydrogen energy share. The developed tool was validated using experimental data. As a results, the operating conditions of maximum valve lift = 10.60 mm and inlet valve closing = 30 °CA ABDC (MVL10 IVC30) prevent the engine from backfire and pre-ignition, and ensure a high volumetric efficiency. Moreover, a hydrogen start of injection of 60 °CA ATDC (HSOI60) is appropriate to provide a pre-cooling effect and thus, reduce the pre-ignition sources and helps to quench any hot residual combustion products. While, the hydrogen injection pressure of 2.7 bar and an inclination of 60°, stimulate a better quality of hydrogen-air mixture. Afterwards, a comparison between combustion characteristics of the optimized hydrogen-diesel dual fuel mode and the baseline (diesel mode) was conducted. The result was, under dual fuel mode there is an increase in combustion characteristics and NOx emissions as well as a decrease in CO2 emissions. For further improvement of dual fuel mode, retarding diesel start of injection (DSOI) strategy was used.     

Availability analysis of a coke oven gas fueled spark ignition engine

The current work investigates a coke oven gas fueled spark ignition (SI) engine from the perspective of the first and second laws in order to understand the energy conversion performance of fuels and achieve highly efficient utilization. A detailed energy and exergy analysis is applied to a quasi-dimensional two-zone spark ignition engine model which combines turbulence flame propagation speed model at 1500 rpm by changing gas fuel types, compression ratio, load and ignition timing. It was found that the irreversibility of methane is the maximum and that of syngas is the minimum among the three different fuels. The irreversibility in the combustion process of a coke oven gas fueled SI engine is reduced when the compression ratio or the throttle valve opening angle is increased and the ignition timing is delayed. Increasing the compression ratio and delaying the ignition timing can improve the first and second law efficiency and reduce the brake specific fuel consumption (BSFC). The power performance and fuel economy are good and the energy is also used effectively when the compression ratio is 11, the throttle angle is 90% and the ignition time is ?10° CA ATDC respectively.     

Direct injection of hydrogen main fuel and diesel pilot fuel in a retrofitted single-cylinder compression ignition engine

Up to 90% hydrogen energy fraction was achieved in a hydrogen diesel dual-fuel direct injection (H2DDI) light-duty single-cylinder compression ignition engine. An automotive-size inline single-cylinder diesel engine was modified to install an additional hydrogen direct injector. The engine was operated at a constant speed of 2000 revolutions per minute and fixed combustion phasing of ?10 crank angle degrees before top dead centre (°CA bTDC) while evaluating the power output, efficiency, combustion and engine-out emissions. A parametric study was conducted at an intermediate load with 20–90% hydrogen energy fraction and 180-0 °CA bTDC injection timing. High indicated mean effective pressure (IMEP) of up to 943 kPa and 57.2% indicated efficiency was achieved at 90% hydrogen energy fraction, at the expense of NO_x emissions. The hydrogen injection timing directly controls the mixture condition and combustion mode. Early hydrogen injection timings exhibited premixed combustion behaviour while late injection timings produced mixing-controlled combustion, with an intermediate point reached at 40 °CA bTDC hydrogen injection timing. At 90% hydrogen energy fraction, the earlier injection timing leads to higher IMEP/efficiency but the NO_x increase is inevitable due to enhanced premixed combustion. To keep the NO_x increase minimal and achieve the same combustion phasing of a diesel baseline, the 40 °CA bTDC hydrogen injection timing shows the best performance at which 85.9% CO₂ reduction and 13.3% IMEP/efficiency increase are achieved.     

Multi-objective optimization of diesel engine performance,vibration and emission parameters employing blends of biodiesel,hydrogen and cerium oxide nanoparticles with the aid of response surface methodology approach

Recent surges in crude oil prices have motivated researchers to find an alternative sustainable fuel called biodiesel from various inedible oils with lower carbo impact on the environment. The research is performed in diesel engine fuelled with blends of biodiesel coupled with cerium oxide nanoparticles and hydrogen content so as to optimize various factors which are responsible for performance, vibration and emission characteristics. Multi-objective optimization is achieved by employing RSM which also examines prime input parameters (engine load, nanoparticle concentration, compression ratio, hydrogen blend percentage and ignition pressure) responsible in varying engine characteristics. Henceforth, blends of Water Hyacinth can be successfully applied in diesel engine with lower environmental impact and enhanced cost effectiveness. Experimentation is performed on the central composite rotating design (CCRD) matrix with 5-level factor. Engine load was applied between 0 and 100%, NPC varied between 0 and 80 ppm, CR ranges between 17 and 19, hydrogen blend percentage varies between 0 and 40% and at a maximum injection pressure of 240 bar. Pareto-optimal conditions achieved for input conditions of 28.68% biofuel blend, 87.88 engine load, 80 ppm NPC, compression ratio of 19 and 194.54 bar infusion pressure were BTE, BSEC, NOx, UBHC and vibration reduction are 33.57%, 0.2550, 461.3002 ppm vol., and 28.08 ppm vol. And 22.21%, respectively.     

Effect of fuel opening injection pressure and injection timing of hydrogen enriched rice bran biodiesel fuelled in CI engine

Fuel opening injection pressure and injection timing are important injection parameters, and they have a significant influence on engine combustion, performance, and emissions. The focus of this work is to improve the performance and emissions of single-cylinder diesel engines by using injection parameters in engines running with rice bran biodiesel 10% blend (RB10+H₂) and 20% blend (RB20+H₂) with a fixed hydrogen flow rate of 7 lpm. In addition, hydrogen and biodiesel are excellent alternatives to conventional fuels, which can reduce energy consumption and strict emission standards. The investigation is conducted for three different opening injection pressure of 220, 240, 260 bar, and four different injection timings of 20°, 22°, 24°, and 26° bTDC. Results indicate that the sample ‘RB10+H₂’ provides 3.32% higher BTE and reduces the fuel consumption by 13% as diesel fuel. The blend RB10+H₂ attributes a maximum cylinder pressure of 68.7 bar and a peak HRR value of 49 J/ºCA. Further, compared to diesel, RB10+H₂ blend emits lower CO, HC, and smoke opacity by 17%, 22%, and 16%, respectively. However, an almost 12% increase of nitrogen oxides for the RB10+H₂ blend is observed. However, with advanced injection timing and higher opening injection pressure, NOx emissions is slightly increased.     

Explorations of the impacts on a hydrogen fuelled opposed rotary piston engine performance by ignition timing under part load conditions

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.     

Strategies to improve the performance of a spark ignition engine using fuel blends of biogas with natural gas,propane and hydrogen

This work presents the strategies applied to improve the performance of a spark ignition (SI) biogas engine. A diesel engine with a high compression ratio (CR) was converted to SI to be fueled with gaseous fuels. Biogas was used as the main fuel to increase knocking resistance of the blends. Biogas was blended with natural gas, propane, and hydrogen to improve fuel combustion properties. The spark timing (ST) was adjusted for optimum generating efficiencies close to the knocking threshold. The engine was operated on each blend at the maximum output power under stable combustion conditions. The maximum output power was measured at partial throttle limited by engine knocking threshold. The use of biogas in the engine resulted in a power derating of 6.25% compared with the original diesel engine (8 kW @ 1800 rpm). 50% biogas + 50% natural gas was the blend with the highest output power (8.66 kW @1800 rpm) and the highest generating efficiency (29.8%); this blend indeed got better results than the blends enriched with propane and hydrogen. Tests conditions were selected to achieve an average knocking peak pressure between 0.3 and 0.5 bar and COV of IMEP lower than 4% using 200 consecutive cycles as reference. With the blends of biogas, propane, and hydrogen, the output power obtained was just over 8 kW whereas the blends of biogas, natural gas, and hydrogen the output power were close to 8.6 kW. Moreover, a new approach to evaluate the maximum output power in gas engines is proposed, which does not depend on the engine % throttle but on the limit defined by the knocking threshold and cyclic variations.     

The effect of hydrogen on the performance and emissions of an SI engine having a high compression ratio fuelled by compressed natural gas

The aim of this paper is investigation of the effect of hydrogen on engine performance and emissions characteristics of an SI engine, having a high compression ratio, fuelled by HCNG (hydrogen enriched compressed natural gas) blend. The experiments were carried out at 1500, 2000 and 2500 rpm under full load conditions of a modified Isuzu 3.9 L engine, having a compression ratio of 12.5. The engine brake power, brake thermal efficiency, combustion analysis and emissions parameters were realized at 5, 10 15 and 20 deg. CA BTDC (crank angle before top dead center) ignition timings and in excess air ratios of 0.9–1.3 fuelled by hydrogen enriched compressed natural gas (100/0, 95/5, 90/10 and 80/20 of % natural gas/hydrogen).The experimental results showed that the maximum power values were generally obtained with HCNG5 (5% hydrogen in natural gas) fuel. The optimum ignition timing that was obtained according to the maximum brake torque was retarded by the addition of hydrogen to CNG (compressed natural gas), while it was advanced by increasing the engine speed. Furthermore, it was observed that the BTE (brake thermal efficiency) generally declined with the hydrogen addition to compressed natural gas and increasing the engine speed. Additionally, the curves of cylinder pressure and ROHR (rate of heat release values) generally closed to top dead center with the increasing of the hydrogen fraction in the blend and a decreasing engine speed. The hydrocarbon and carbon monoxide emissions generally obtained were lower than the Euro-5 and Euro-6 standards.     

Experimental investigation of SI engine characteristics using Acetone-Butanol-Ethanol (ABE) – Gasoline blends and optimization using Particle Swarm Optimization

This study conducts an experimental investigation of spark ignition (SI) engine characteristics using gasoline blended with Acetone-Butanol-Ethanol (ABE) that act as hydrogen and oxygen carriers. The number of experiments is planned and executed according to a design of experiments with full-factorial design, wherein ABE blend percentage and speed are taken as input parameters and brake thermal efficiency (BTE), emissions of carbon monoxide (CO), hydrocarbon (HC), and oxides of nitrogen (NOx) are taken as the responses. In the present study, a multi-objective optimization technique, Particle Swarm Optimization (PSO), is used to optimize spark ignition engine performance and emission parameters. The results predicted by the regression model are compared with the experimental results. PSO is used to study the Pareto front of BTE, CO, HC, and NOx, respectively. The results indicated that when the engine is run at 1500 rpm, with the fuel blend having 5.4% ethanol, a minimum value of 0.58% CO, 211 ppm of HC are obtained, giving a maximum BTE of 28%. Similarly, when the engine is run at 2264 rpm with a 5% ethanol blend, minimum NOx emission of 1029 ppm and a maximum BTE of 30% are obtained.     

Combined Effect of Air Intake Method and Hydrogen Injection Timing on Airflow Movement and Mixture Formation in a hydrogen direct injection rotary engine

The hydrogen rotary engine (HRE) has advantages of the high power-to-weight ratio and low emission performance. In this study, a three-dimensional dynamic simulation model of the hydrogen direct injection rotary engine is established, and the accuracy and reliability of the gas nozzle injection model are verified based on experimental data in detail. Then, the combined effects of the air intake method (AIM) and hydrogen injection timing (HIT) on airflow movement and mixture formation processes in the HRE are investigated. The numerical results show that the compound AIM improves the engine volumetric efficiency due to more air entering. As for air movement, the average airflow velocity and turbulent kinetic energy both increase significantly during hydrogen injection duration under different HITs and AIMs. In terms of mixture formation, using compound AIM, more hydrogen accumulates near the ignition chamber compared to the peripheral and side AIMs. Also, when HITs are ?286°CA and ?190°CA, hydrogen concentrates near the ignition chamber, which will be conducive to the subsequent combustion process due to the RE's flame forward propagation characteristics. Comprehensively considering the airflow movement characteristics and fuel distribution rule, the peripheral AIM and the compound AIM, which their HITs are set at the compression stage (?190°CA), namely Case7 and Case9, are preferred schemes. This paper can provide some theoretical guidance for the intake structure design, injection strategy optimization and mixture rational organization of the HRE.     

Effects of ignition advance on a dual sequential ignition engine at lean mixture for hydrogen enriched butane usage

In this study, the effects of ignition advance on dual sequential ignition engine characteristics and exhaust gas emissions for hydrogen enriched butane usage and lean mixture were investigated numerically and experimentally. The main purpose of this study is to reveal the effects of h-butane application in a commercial spark ignition gasoline engine. One cylinder of the commercially dual sequential spark ignition engine was modeled in the Star-CD software, taking into account all the components of the combustion chamber (intake-exhaust manifold connections, intake-exhaust valves, cylinder, cylinder head, piston, spark plugs). Angelberger wall approximation, k-ε RNG turbulence model and G-equation combustion model were used for analysis. In the dual sequential spark ignition, the difference between the spark plugs was defined as 5° CAD. At the numerical analysis; 10.8:1 compression ratio, 1.3 air-fuel ratio, 2800 rpm engine speed, 0.0010 m the flame radius and 0.0001 m the flame thickness were kept constant. The hydrogen-butane mixture was defined as 4%–96% by mass. In the analysis, the optimal ignition advance was determined by the working conditions. In addition, the effects of changes in ignition advance were examined in detail at lean mixture. For engine operating conditions under investigation, it has been determined that the 50° CAD ignition advance from the top dead center is the optimal ignition advance in terms of engine performance and emission balance. It has also been found that the NO_x formation rises up as the ignition advance increases. The BTE values were approximately 12.01% higher than butane experimental results. The experimental BTE values for h-butane were overall 3.01% lower than h-butane numerical results.     

Experimental investigation of combustion characteristics and NOx emission of a turbocharged hydrogen internal combustion engine

In order to alleviate the contradictions of increasingly prominent environmental pollution, greenhouse gas emissions and oil resource security issues, the search for renewable and clean alternative energy sources is getting more and more attention. Hydrogen energy is known as a future energy source because of its safety, reliability, wide range of resources and non-polluting products. Hydrogen internal combustion engine combines the technical advantages of traditional internal combustion engines and has comprehensive comparative advantages in terms of manufacturing cost, fuel adaptability and reliability. It is one of the practical ways to realize hydrogen energy utilization. In this paper, the combustion characteristics and NOx emission of a turbocharged hydrogen engine were investigated using the test data. The results showed the combustion duration (the crank angle of 10%–90% fuel burned) at 1500 rpm and 2000 rpm was equal and the combustion duration is much bigger than the other loads when the BMEP is 0.27 MPa. The reason is the effect of the turbocharger on the gas exchange process, which will influence the combustion process. The cylinder pressure and pressure rise rate were also investigated and the peak pressure rise rate was lower than 0.25 MPa/°CA at all working conditions. Moreover, the NOx emission changed from 300 ppm to 1200 ppm with engine speed increasing and the maximum value can reach to 7000 ppm when the equivalence ratio is 0.88 at 2500 rpm, maximum brake torque. The NOx emission shows different changing tendencies with different working conditions. Finally, these conclusions can be used to develop controlling strategies to solve the contradictions among power, brake thermal efficiency and NOx emission for the turbocharged hydrogen internal combustion engines.     

Hydrogen-rich syngas production and carbon dioxide formation using aqueous urea solution in biogas steam reforming by thermodynamic analysis

Biogas is a renewable biofuel that contains a lot of CH₄ and CO₂. Biogas can be used to produce heat and electric power while reducing CH₄, one of greenhouse gas emissions. As a result, it has been getting increasing academic attention. There are some application ways of biogas; biogas can produce hydrogen to feed a fuel cell by reforming process. Urea is also a hydrogen carrier and could produce hydrogen by steam reforming. This study then employes steam reforming of biogas and compares hydrogen-rich syngas production and carbon dioxide with various methane concentrations using steam and aqueous urea solution (AUS) by Thermodynamic analysis. The results show that the utilization of AUS as a replacement for steam enriches the production of H₂ and CO and has a slight CO₂ rise compared with pure biogas steam reforming at a temperature higher than 800 °C. However, CO₂ formation is less than the initial CO₂ in biogas. At the reaction temperature of 700 °C, carbon formation does not occur in the reforming process for steam/biogas ratios higher than 2. These conditions led to the highest H₂, CO production, and reforming efficiency (about 125%). The results can be used as operation data for systems that combine biogas reforming and applied to solid oxide fuel cell (SOFC), which usually operates between 700 °C to 900 °C to generate electric power in the future.