Pre-chamber turbulent jet ignition of methane/air mixtures with multiple orifices in a large bore constant volume chamber: effect of air-fuel equivalence ratio and pre-mixed pressure

Liquefied natural gas (LNG), mainly composed of methane, is in progress to substitute diesel fuel in heavy-duty marine engine for practical, economic, and environmental considerations. However, natural gas is relatively difficult to be ignited in a large bore combustion chamber. A combustion enhancement technique called pre-chamber turbulent jet ignition (TJI) can permit combustion and flame propagation in a large-bore volume. To investigate the effect of air-fuel equivalence ratio and pre-mixed pressure on pre-chamber TJI of methane/air mixtures with multiple orifices in a large bore volume, experimental tests and computational simulations were implemented to study the discharge of hot turbulent jets from six orifices of the pre-chamber. Different initial pressures and air-fuel equivalence ratios were considered to analyze the characteristics of TJI. The asymmetry of the turbulent jet actuated from six different orifices were found due to the asymmetric orientation of the spark plug, resulting in the inhomogeneous distribution of combustion in the constant volume chamber, which should be considered seriously in the marine engine design. Besides, as the premixed pressure increases, it has more effect on the flame propagation and plays a more important role, as it further increases.     

预燃室式天然气掺氢发动机燃烧及排放模拟

为探索掺氢对预燃室式大功率中速天然气发动机燃烧和排放的影响,采用计算流体动力学耦合化学动力学方法,在一台6ACD320型天然气发动机上,对氢气体积分数为0～ 30％的天然气-氢气混合燃料的燃烧过程进行了数值模拟.结果表明:在天然气中掺氢促使缸内产生了更多的0、OH等活性自由基,从而加速了缸内火焰传播,发动机的指示燃气消...     

Reactivity controlled turbulent jet ignition (RCTJI) for ammonia engine

Ammonia (NH₃) fuel is a promising hydrogen carrier for engine carbon neutrality. However, the high auto-ignition temperature and low flame velocity of NH₃ substantially restrain its application in internal combustion engines (ICE). In previous works, hydrogen and pre-chamber turbulent jet ignition (TJI) have shown the potential abilities to solve critical combustion issues. Therefore, in this work, a concept of reactivity controlled turbulent jet ignition (RCTJI) for ammonia engines is proposed, where a newly designed air-assisted pre-chamber system with scavenging and hydrogen injection is adopted.     

Diesel-like and HCCI-like operation of a truck engine converted to hydrogen

In addition to the traditional spark ignition (SI), premixed, gasoline-like and compression ignition (CI), diffusion, Diesel-like operation of internal combustion engines, premixed, homogeneous charge, compression ignition (HCCI) operation has also been proposed to improve the fuel conversion efficiency and reduce the pollutant formation. To be attractive, the operation in HCCI mode has to be coupled with the other traditional operations, being HCCI in general difficult to be controlled and limited to values of the air-to-fuel equivalence ratio λ within a narrow windows set by the lean burn limits with large λ and the peak pressure limits with small λ. Furthermore, the specific kinetics of hydrogen makes this fuel more difficult than other hydrocarbons to work in an engine operating HCCI without assistance. In a recent paper, the design of a 12.8 L in-line six cylinder turbo charged directly injected heavy duty truck Diesel engine fuelled with hydrogen has been discussed. Conversion of a latest Diesel engine with a novel power turbine has been studied replacing the in-cylinder Diesel injector and glow plug with a hydrogen injector and a jet ignition pre-chamber. The pre-chamber is a small volume accommodating another hydrogen injector and a glow plug being connected to the in-cylinder through calibrated orifices. This design permits to operate the engine in four different modes:

-

diffusion with jet ignition M₁ - an injection occurs in the jet ignition pre-chamber before the main chamber fuel is injected and the engine operates therefore Diesel-like;

-

mixed diffusion/premixed Diesel/gasoline like M₂ - an injection occurs in the jet ignition pre-chamber after only part of the main chamber fuel is injected and mixed with air;

-

premixed with jet ignition M₃ - an injection occurs in the jet ignition pre-chamber after the main chamber fuel is injected and mixed with air and the engine operates gasoline-like;

-

premixed without jet ignition M₄ - no injection occurs in the jet ignition pre-chamber and the engine operates HCCI-like.

While only the Diesel-like operation was previously considered full load, all the modes including the operation HCCI-like are considered here over the full range of loads where the power turbine is either connected to the crankshaft or disconnected and the exhaust gases pass through this turbine or bypass the turbine.This paper deals with computational rather than experimental work. Computations are made with the latest predictive HCCI model using detailed kinetics of GT-POWER and the well established correlative Wiebe models for Diesel and gasoline combustion. HCCI-like operation is considered over a range of air-to-fuel equivalence ratio λ much wider than usually considered with other fuels being perhaps even more suitable than hydrogen to this operation thanks to the jet ignition assistance.     

The ignition characteristics of the pre-chamber turbulent jet ignition of the hydrogen and methane based on different orifices

In this paper, the combustion characteristics of premixed CH₄-air and H₂-air mixtures with different excess air coefficients ignited by hot jet or jet flame are investigated experimentally in a constant volume combustion chamber (CVCC). The small volume pre-chambers with different orifices (2 or 3 mm in diameter) in the passive or active pre-chamber were selected. Both the high-speed Schlieren and OH1 chemiluminescence imaging are applied to visualize the turbulent jet ignition (TJI) process in the main chamber. Results show that the variation of orifice has diverse influences on the turbulent jet ignitions of methane and hydrogen. Smaller orifices will reduce the temperature of the jet due to the stronger stretch and throttling effect, including change of lean flammability limit, ignition delay, and re-ignition location. Furthermore, shock waves and pressure oscillations were captured in the experiments with hydrogen jets. The former is related to the jet velocity, while the latter is mainly affected by the mixture thermodynamic states in the main chamber. Furthermore, the re-ignition location is discussed. If the mixture reactivity and the jet energy are sufficiently high, the reaction will be initiated at the tip of the jet in a short time. On the contrary, a relatively long time is required to prepare the mixture during the entrainment when the reactivity is not high enough, and the corresponding re-ignition location will move towards the orifice exit owing to the temperature decline at the tip. Finally, the ignition mode transition of hydrogen jet in lean cases with a 2 mm orifice is explained.     

Effect of pre-chamber geometrical parameters and operating conditions on the combustion characteristics of the hydrogen-air mixtures in a pre-chamber spark ignition system

The pre-chamber spark ignition system is a promising advanced ignition system adopted for lean burn spark ignition engines as it enables stable combustion and enhances engine efficiency. The performance of the PCSI system is governed by the turbulent flame jet ejected from the pre-chamber, which is influenced by the pre-chamber geometrical parameters and the operating conditions. Hence, the current study aims to understand the effects of pre-chamber volume, nozzle hole diameter, equivalence ratio, and initial chamber pressure on the combustion and flame jet characteristics of hydrogen-air mixture in a passive PCSI system. Pre-chamber with different nozzle hole diameters (1 mm, 2 mm, 3 mm, and 4 mm) and volumes (2%, 4%, and 6% of the engine clearance volume) were selected and manufactured in-house. The experimental investigation of these pre-chamber configurations was carried out in a constant-volume combustion chamber with optical access. The flame development process was captured using a high-speed camera at a rate of 20000 fps, and the images were processed in MATLAB to obtain quantitative data. The combustion characteristics of hydrogen-air mixtures with the PCSI system improved when compared to the conventional SI system; however, the improvement was more significant for ultra-lean mixtures. Early start of combustion and shorter combustion duration were observed for PCSI – D2 and PCSI – D3 configurations, respectively and improved combustion and flame jet characteristics were also noted for these configurations. With the increase in pre-chamber volume, ignition energy associated with the flame jet increases, which reduces the combustion duration and the ignition lag.     

The effect of turbulent jet induced by pre-chamber sparkplug on combustion characteristics of hydrogen-air pre-mixture

Effect of turbulent jet ignition induced by pre-chamber sparkplug (PCSP), a simper version of turbulent jet ignition pre-chamber system without fuel injection, on the air-hydrogen combustion characteristics was conducted based on an optical constant volume chamber under varied equivalence ratio conditions. The dynamic pressure sensor and schlieren system were used to evaluate the heat release and flame propagation characteristics. The results confirm the feasibility of PCSP type turbulent jet. The jet increase the flame propagation speed significantly compared to standard ignition, which shorten ignition delay and combustion duration, advance T50 largely, and increase the maximum combustion pressure slightly. As a result, the combustion intensity is increased largely, especially under lean regime, the combustion intensity index can be as high as 1.7 at certain equivalence ratio. In addition, the PCSP turbulent jet reduces the sensitivity of heat release to variation of equivalence ratio, which is helpful to simplify the combustion controlling strategy. Furthermore, with the enhancement of the flame propagation, the tendency of knocking combustion can be suppressed potentially.     

Research on the hydrogen injection strategy of a direct injection natural gas/hydrogen rotary engine considering apex seal leakage

The purpose of the present paper is to investigate the hydrogen injection strategy on the combustion performance of a natural gas/hydrogen rotary engine. Considering that apex seal leakage (ASL) is an inevitable problem in the actual working process of a rotary engine, the action of ASL cannot be ignored for an in-depth study of its combustion performance. Therefore, in this paper, a 3D dynamic simulation model that put the effect of ASL into consideration was established. Furthermore, based on the established 3D model, the combustion process of a natural gas/hydrogen rotary engine under various hydrogen injection angle (HIA) and hydrogen injection timing (HIT) was investigated. The results indicated that the hydrogen jet flow first impacted on the rotor wall after entering the cylinder, and then diffused under the action of the vortexes in the cylinder. Therefore, the HIA and HIT could change the hydrogen distribution by changing the hydrogen impact location and the intensities of the vortexes in the cylinder. In addition, the ideal hydrogen distribution at the ignition timing which could improve the combustion efficiency was given. That is, under the premise of ensuring minimized hydrogen leakage, the hydrogen should mainly distribute in the middle and the front of the cylinder, and a high hydrogen concentration is maintained near the spark plug.     

Effects of direct water injection on engine performance in a hydrogen (H2)-fueled engine at varied amounts of injected water and water injection timing

In this paper, the effects of direct water injection (WI) on characteristics of combustion and emission for a hydrogen (H₂)-fueled spark ignition (SI) engine were experimentally investigated. The experiments conducted under different amounts of water injection (AWI) and varied water injection timing (WIT). The experimental results showed that in-cylinder pressure decreased, indicated thermal efficiency (ITE) increased, and the flame development (CA0-10) and propagation (CA10-90) periods prolonged when AWI raised. When AIW grew to 4.5 mg/cycle, Nitrogen oxides (NOx) expelled from the original engine decreased by 53.7% when excess air ratio (λ) was 1.15. Early WIT had positive effects on the reduction of NOx emissions. When WIT retarded, in-cylinder pressure increased, ITE decreased and CA0-10 and CA10-90 shortened, NOx emissions rapidly increased.     

不同过量空气系数下射流点火发动机燃烧、排放和爆震特性的试验研究

基于单缸试验机研究了过量空气系数对射流点火发动机性能的影响.通过分析发动机性能曲线、缸内燃烧情况及爆震特性探究射流点火最佳运行区间,并与火花点火燃烧方式进行对比.结果表明,射流点火可以有效提升瞬时放热率并拓展发动机稀燃极限,缩短缸内混合气滞燃期与燃烧持续期,同时燃油经济性有一定提升.在稀燃条件下氮氧化物排放极低.爆震方...     

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.     

Improving burning speed by using hydrogen enrichment and turbulent jet ignition system in a rotary engine

Low flame speed restrains engine efficiency and increases HC emissions in rotary engines. Hydrogen addition and turbulent jet ignition have a great potential in increasing engine performance as they increase fuel burning speed. In this study, the classical R13b-Renesis Wankel engine and a modified one with a turbulent jet ignition configuration are numerically investigated by using hydrogen as a supplement. Eccentric motion of the rotor was generated by using User Defined Function in ANSYS-Fluent software. Pure methane and methane blended with 3% and 6% hydrogen energy fractions were used as fuels in the calculations. Combustion was modeled by using reduced mechanism of hydrogen-methane combustion having 22 species and 104 reactions. The Wankel engine was simulated at 2000 rpm speed and partial load conditions. At first, classical engine configuration having two spark plugs was simulated with pure methane. Then, hydrogen blended methane simulations were conducted to investigate the benefits of the hydrogen addition. Similar procedure was applied for the turbulent jet ignition application. The results show that both approaches are effective on increasing the burning speed of the fuel. It is revealed that hydrogen addition increases the indicated mean effective pressure (IMEP) by 1.8% and 5.2% for 3% and 6% hydrogen fraction cases respectively in the classical engine. Turbulent jet ignition with pure methane increases IMEP by 4.7% compared to the classical engine. Hydrogen addition only in pre-chamber is effective as much as 6% hydrogen fraction of classical engine. As the burning speed is increased by the application of these methods, CO and HC emissions are reduced and NO emission is increased. It is concluded that benefits of hydrogen addition and turbulent jet ignition applications can be optimized for both reducing harmful emissions and increasing engine performance.     

Novel heavy duty engine concept for operation dual fuel H2–NH3

A prior paper has presented a novel design of a heavy duty truck engine fuelled with H₂. In this design, the customary in-cylinder Diesel injector and glow plug are replaced with a main chamber fuel injector and a jet ignition pre-chamber. The jet ignition pre-chamber is a small volume that is connected to the in-cylinder through calibrated orifices accommodating another fuel injector and a glow or a spark plug that controls the start of combustion. This design permits to operate the engine in four different modes: traditional compression ignition (CI), diffusion, Diesel-like (M₁); mixed gasoline/Diesel-like (M₂); traditional spark ignition (SI), premixed, gasoline-like (M₃); premixed, homogeneous charge compression ignition HCCI-like (M₄). In the mode diffusion with jet ignition (M₁), an injection occurs in the jet ignition pre-chamber before the main chamber fuel is injected and the engine operates therefore mostly Diesel-like. In the mode mixed diffusion/premixed Diesel/gasoline-like (M₂) an injection occurs in the jet ignition pre-chamber after only part of the main chamber fuel is injected and mixed with air. In the mode premixed with jet ignition (M₃), an injection occurs in the jet ignition pre-chamber after the main chamber fuel is injected and mixed with air and the engine operates gasoline-like. Finally, in the mode premixed without jet ignition (M₄), no injection occurs in the jet ignition pre-chamber and the engine operates HCCI-like. Modelling results have already been presented and discussed with H₂ as the main chamber and pre-chamber fuel. This paper considers the option to accommodate a second main chamber injector that will inject the NH₃ that will then burn in air thanks to the hot combusting gases from the combustion of H₂ and air using the modes M₁ and M₂ described above. The mode M₃ also of interest is not considered here. First results of simulations show the opportunity to achieve better than Diesel fuel energy conversion efficiency thanks to the reduced heat losses of the “cold burning” NH₃ and suggest to perform the experiments needed to further support the findings.     

Experimental investigation on the combustion process in a spark ignition optically accessible engine fueled with methane/hydrogen blends

The combustion process of a four-stroke optically accessible single cylinder Port Fuel Injection spark ignition (PFI SI) engine was experimentally investigated. It was fueled with two methane/hydrogen blends. The in-cylinder pressure and the related data were analyzed as indicators of the combustion quality. 2D-digital imaging measurements were performed to evaluate the flame propagation. UV–visible spectroscopy allows to characterize the combustion by means of the detection of OH* and CH*. The exhaust was characterized using conventional analyzers. For the methane/hydrogen blends the indicated data suggests an increase of the thermal efficiency and a decrease of the combustion duration with the increase of the hydrogen fraction. The optical results highlight a more homogeneous mixture that increases the combustion reaction rate and provides a more uniform and rapid flame propagation. On the other hand, high NO_x emissions were measured likely because of the higher combustion temperature due to hydrogen addition.     

Improvement of thermal efficiency and reduction of NOx emissions by burning a controlled jet plume in high-pressure direct-injection hydrogen engines

A new combustion process called the Plume Ignition Combustion Concept (PCC), in which the plume tail of the hydrogen jet is spark-ignited immediately after the completion of fuel injection to accomplish combustion of a rich mixture has been proposed by the authors. This PCC combustion process markedly reduces nitrogen oxides (NOx) emissions in the high-output region while maintaining high levels of thermal efficiency and power. On the other hand, as burning lean mixture of fuel and air is the conventional way to improve thermal efficiency and reduce NOx, a high λ premixed mixture of hydrogen and air formed by injecting hydrogen in the early stage of the compression stroke has been used in direct-injection hydrogen engines. It was recently reported, however, that this mixture condition does not always offer expected improved thermal efficiency under even lean mixture conditions by increasing unburned hydrogen emissions caused by incomplete flame propagation in the non-uniform and extremely lean portion of the mixture. In this study, the effect of retarding the injection timing to late in the compression stroke but slightly advanced from original PCC was examined as a way of reducing unburned hydrogen emissions and improving thermal efficiency. These effects result from a centroidal axially stratified mixture that positions a fairly rich charge near the spark plug. This stratified mixture is presumably effective in reducing incomplete flame propagation thought to be the cause of unburned hydrogen emissions and also promoting increasing burning velocity of the mixture that improve thermal efficiency. Finally, this research is characterized by measuring the hydrogen fuel concentration at the point and the time of spark ignition quantitatively by spark-induced breakdown spectroscopy in order to identify the changes in mixture ratio mentioned above caused by the parameters involved.     

Research on combustion and emission characteristics of a hydrous ethanol/hydrogen combined injection spark ignition engine under lean-burn conditions

Ethanol, as one of the carbon-neutral fuels for spark ignition (SI) engine, has been widely used. Dehydration and purification of ethanol during production process will lead to high energy consumption. If hydrous ethanol can be directly applied to the engine, the cost of use will be greatly reduced. Due to the high latent heat of vaporization of ethanol and water, it is necessary to consider the performance of atomization, evaporation and combustion stability when hydrous ethanol is used in engine. As a zero-carbon fuel, hydrogen has excellent characteristics such as low ignition energy, fast flame propagation speed and wide combustion limit. The combination of hydrous ethanol and hydrogen can reduce the use cost and ensure better combustion performance. Therefore, this study explores the performance of hydrous ethanol/hydrogen in SI combined injection engine. The hydrous ethanol is injected into the intake port and the hydrogen is directly injected into the cylinder during the compression stroke. In this study, we firstly analyze the optimal water blending ratio (ω) of hydrous ethanol, which including 0, 3%, 6%, 9% and 12%. The experimental results show that the hydrous ethanol with 9% water ratio has the best performance without hydrogen addition. Based on the 9% water ratio, the effects of hydrogen blending ratio (0, 5%, 10%, 15% and 20%) on the combustion and emission under different excess air ratio (λ) (1, 1.1, 1.2, 1.3, 1.4). Hydrogen addition can increase the degree of constant volume combustion, so that the maximum cylinder pressure and temperature increase with the increase of the hydrogen blending ratio (HBR). When λ = 1.3 and HBR = 20%, the maximum in-cylinder pressure can be increased by 108.64% compared to pure hydrous ethanol. Hydrogen effectively increases the indicated mean effective pressure (IMEP) and reduces the coefficient of variation of IMEP (COV_IMEP). Adding hydrogen can reduce CO and HC emissions, while NO_x emissions will increase. When λ = 1.2 and HBR increasing from 0 to 20%, the NOx emissions increase by 106.75%, but it is still less than the NOx emissions of pure hydrous ethanol at λ = 1. On the whole, hydrogen direct injection can improve the combustion performance of hydrous ethanol and achieve stable combustion under lean-burn conditions.     

Effects of second hydrogen direct injection proportion and injection timing on combustion and emission characteristics of hydrogen/n-butanol combined injection engine

Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy.     

Research on emission characteristics of hydrogen fuel internal combustion engine based on more detailed mechanism

A CFD simulation model with simplified chemical reaction mechanism was built based on CONVERGE software to study the in-cylinder combustion progress and NO generation mechanism of hydrogen fueled internal combustion engine (HICE). Simulation results show that the in-cylinder combustion progress experiences the ellipsoidal flame stable propagation stage and the rapid turbulent combustion stage. At the end of rapid turbulent combustion the OH concentration decreases quickly, the peak temperature and maximum NO mass appear at that time, and then the in-cylinder temperature and NO mass decrease step by step. The final emission depends on the peak temperature and NO decomposition time of high-temperature regions. The higher the maximum temperature, the greater the NO peak mass; and the faster the temperature drop, the less the NO decomposes. Adoption of EGR can reduce the in-cylinder maximum temperature, and NO decomposes sufficiently at low speed, which in turn leads to lower NO emission of HICE.     

Investigation of the gas injection rate shape on combustion,knock and emissions behavior of a rotary engine with hydrogen direct-injection enrichment

The application of hydrogen direct-injection enrichment improves the performance of gasoline Wankel rotary engine, and the hydrogen injection strategy has a significant impact on combustion, knock, and emissions. The Z160F Wankel rotary engine was used as the investigated compact engine, and the simulation model was developed using CONVERGE software. The combustion, knock and emissions characteristics of the engine were studied with the different mass flow of hydrogen injection, i.e., the trapezoid, wedge, slope, triangle and rectangle type of gas injection rate shape. In the numerical simulations, the in-cylinder pressure oscillations were monitored using monitoring points, and the knock index (KI) was used as an evaluation indicator. The study revealed that the gas injection rate shape significantly affected the mixture of hydrogen and air, thus impacting combustion, knock and emissions. When the injection rate shape was rectangle, the flame speed was faster, the peak pressure in the cylinder was higher, and the corresponding crank angle was earlier, which led to higher pressure oscillations in the cylinder and larger KI. Based on the rectangle injection rate shape, the KI decreased by 75.81%, 33.47%, 26.46% and 76.58% for trapezoid, wedge, slope, and triangle, respectively, and the indicated mean effective pressure increased by 15.68%, 5.07%, 0.56% and 14.98%, respectively. Due to the small difference in maximum temperature, which resulted in very little variation in nitrogen oxides for each injection rate shape, the total hydrocarbon emissions of the trapezoid and triangle injection rate shape was high due to the delayed combustion phase. This paper provides a solution for direct hydrogen injection to improve the combustion, knock and emissions behavior of the rotary engine.     

CO_2进气道和缸内喷射对柴油准HCCI燃烧的影响

通过开发的气体喷射系统,研究并对比了进气道和缸内喷射CO2对准均质压燃燃烧排放的影响.准HCCI燃烧由两段喷油实现.结果表明:随着缸内和进气道CO2循环喷射量的增大,缸内最高平均温度降低,燃烧相位推迟,最大压力升高率变化不大;NOX排放减小,HC和CO排放增大.等CO2喷射量下,NOx随着缸内CO2喷射始点的提前而减小;缸内喷射的HC和CO排放较进气道喷射的大.随着CO2循环喷射量的增大,进气道喷射的烟度开始变化不大,然后急剧上升;而缸内喷射的烟度变化不大.