Combustion-derived soot is a hazardous contributor to air pollution and poses significant health risks. n-decane and methyl butanoate (MB) are key constituents of diesel and biodiesel fuels, respectively. This study examines how varying MB concentrations (0-80%) affect soot formation in n-decane laminar diffusion flames to explore ways to reduce these harmful emissions. The concentrations of soot, polycyclic aromatic hydrocarbons (PAHs), and hydroxyl radical (OH) were measured using laser-induced incandescence (LII) and laser-induced fluorescence (LIF) techniques. Results show that increasing MB concentration decreases OH, PAHs and soot concentrations, indicating that MB weakens combustion intensity and inhibits PAH and soot formation. A chemical reaction mechanism comprising 225 species and 1,321 reactions was developed and validated for n-decane, MB, and PAHs against literature data on ignition delay times, laminar flame velocities, and major specises. Chemical kinetic analysis revealed that increasing MB reduces aromatic hydrocarbon mole fractions. Rate of production (ROP) and sensitivity analyses for A1 (benzene), a key PAH precursor for soot formation, indicate that A1 is primarily formed through the sequential combination of C3 and smaller chain radicals produced during fuel pyrolysis. However, the addition of MB results in the generation of significant amounts of CO and CO2, which reduces the formation of key soot precursor radicals (e.g., C2H2, C2H4, C3H3), thereby reducing soot formation. These findings provide insights into the impact of oxygenated fuel additives on soot formation, offering potential applications for optimizing fuel formulations to reduce soot emissions.

Experimental and chemical kinetics studies on the combustion of linear and cyclic carbonates are essential for gaining insight into the complex chemical reaction processes associated with thermal runaway in lithium-ion batteries (LIBs). In a constant-volume combustion chamber, experiments were conducted at initial temperatures of 403/473/543 K, initial pressures of 1/2/3 atm, and equivalence ratios ranging from 0.7 to 1.5. Laminar burning velocities (LBV) were measured for commonly used linear carbonates, including dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and a cyclic carbonate, ethyl carbonate (EC), which are frequently used in LIBs. The results indicate that the gas-phase reactivity of these carbonates under the same experimental conditions can be summarized as DEC = EMC > DMC > EC. The obtained LBV data have been utilized to validate a new comprehensive chemical kinetics mechanism (CEL) for both linear and cyclic carbonates. CEL places particular emphasis on accurately describing fuel-specific reactions and the CH2CO sub-model. Throughout the entire scope of this study, the predictions made by CEL align well with the experimental data. A detailed kinetics analysis using CEL has revealed that the differences in reaction activity among the four carbonate species primarily arise from variations in the concentrations of active radical species such as H and OH, as well as differences in the initial oxidation reactions that control fuel consumption. All four carbonates generate CO2 from two main sources: one is the CO2 elimination reactions from intermediate species, and the other is the oxidation of CO.

To promote the transition to a carbon neutral society, it is necessary to conduct a comprehensive research on the utilization of ammonia contained in gasoline engine. In the present study, the laminar burning velocity (S-L), Markstein length (L-b) and flame instability of isooctane/ammonia (IC8H18/NH3)-air mixtures were analyzed at the initial temperatures (T) of 400 K and 470 K, initial pressure (P) of 1-4 atm, ammonia mole fraction (XNH3) of 0%-70% and an equivalence ratio (1:1)) ranging from 0.8 to 1.3. Also, the kinetic mechanism of IC8H18/NH3 as proposed by Cai et al. [Combust. Flame, 162, 2015] was further optimized and compared with the mechanism of CRECK and Cai. The results show that the difference between the Cai and present mechanisms is largely attributable to the variation in sensitivity of NH3 oxidation-related reaction to SL. In addition, it is widely known that SL is dependent on the initial temperature and pressure. In order to improve the applicability of IC8H18/ NH3 fuel mixtures, their temperature (alpha) and pressure (13) coefficients were determined given varying 1:1) and XNH3. Meanwhile, a mathematical correlation for SL was also conducted. The analysis of Lb was also conducted to obtain the results showing that Lb decreases with 1:1) increasing, except for NH3-air flame. Moreover, as XNH3 increases, Lb varies between lean and rich flames. For lean-flames, NH3 addition leads to a significant decrease in Lb, while for rich-flames, NH3 addition causes a marginal increase in Lb. All these are attributed to the variation in Zel'dovich number (Ze), effective Lewis number (Le(eff)) and flame thickness (8). Furthermore, the instability of flame suggests that the addition of ammonia enhances the stability of the flame due to the reduced molecular diffusion effect. Moreover, an increase in XNH3 contributes only to a slight decrease of critical Peclect number (Pecr), and a sharp rise in the critical flame radius (Rcr) results from the increase of flame thickness (8).

An experimental study was conducted to investigate the oxidation of methyl butyrate (MB), n-butanol, RP-3 aviation kerosene, and their binary mixtures in laminar premixed flames. The experiments were carried out using the spherical flame method under conditions of P0 = 0.1/0.2/0.3 MPa, T0 = 470 K, phi = 0.8-1.4, and the volume mixing ratio is 20%, 50% and 80%. The effects of adding two potential C4 oxygenated fuels to RP-3 on the laminar burning velocity (SL) and flame instability were first evaluated. A new skeletal mechanism was proposed for this blended fuel system based on the CRECK mechanism, and the new experimental results were extensively used to validate this skeletal mechanism. The results showed that the addition of MB and n-butanol caused a slight decrease and increase, respectively, in the SL of RP-3. After adding 50 % MB and 50% n-butanol, the peak SL of RP-3 decreased by 3.5 cm/s and increased by 2.1 cm/s, respectively. Furthermore, the addition of esters was more favorable for reducing flame instability. Reaction path analysis and flame structure analysis revealed that the effects of adding MB and n-butanol on the oxidation pathway of RP-3 were mainly concentrated in primary oxidation reactions, and their effects on the SL were mainly attributed to changes in the concentrations of OH and H radicals.

The super adiabatic flame temperature (SAFT) phenomenon is important for understanding and controlling the flame stability, NO emission, reaction rate and other aspects of combustion. Therefore, a numerical study was conducted to study the SAFT phenomenon for NH3/O2/N2 mixtures under different initial conditions. It was found that the main characteristics of SAFT for NH3/O2/N2 mixture are the negative heat release in the post-flame zone and the overshoot of H2O. The chemical nature of SAFT was also analyzed and found that the reverse reaction of R4 (H2 + OH = H2O + H) in the post-flame zone, resulting in the overshoot of H2O concentration, is one of the reasons of SAFT. The study also found that H radical plays an important role in SAFT phenomenon, and the relative lack of H radical in the main reaction zone is another one of the important factors of SAFT phenomenon. In addition, the study found that the effects of initial temperatures, pressures and oxygen content on SAFT have opposite trends at different equivalence ratios. When the equivalence ratio is less than 1.6, the increase of initial temperatures and oxygen contents leads to the increase of SAFT; the increase of initial pressure leads to the decrease of SAFT. The opposite tendency occurs when the equivalence ratio exceeds 1.6. This is because the flame temperature and structure changes with the equivalence ratio increasing, and the chemical nature of SAFT changes accordingly.

The laminar burning velocity and Markstein length of TRF (n-heptane, isooctane, and toluene)-air mixtures were investigated at the initial temperature of 400 K and 453 K, initial pressure of 1 bar, and an equivalence ratio range of 0.8-1.5. The effects of extrapolation radius (Rf) and Markstein length (Lb) were discussed on the linear and nonlinear extrapolation models. The results showed that the linear model leads to higher extrapolation result for all equivalence ratios compared with the nonlinear model due to the differences in the third term of Taylor expansion. Finally, the laminar burning velocity and Markstein length uncertainty caused by the extrapolation model can be minimized by adjusting RfLb1 (Rf1 refers to the flame initial extrapolated radius). When the value of Lb Rf1 was below 0.012, the laminar burning velocity and Markstein length uncertainty can be controlled at < 0.05 and < 0.5, respectively.

The method of installing a duct in the front of the injector nozzle has been proved to be effective. This paper mainly studies the effects of fuel properties on ducted fuel injection (DFI). The gas-liquid two phases of spray under different working conditions are captured by using an optical testing system in a constant volume combustion chamber. According to the experimental results, it was found that increasing the back pressure has a promotional effect on the DFI spray, enhancing the spray penetra-tion and spray area relative to the free spray for diesel and gasoline. Furthermore, increasing ambient temperature can promote the effect of DFI spray for gasoline by increasing the spray penetration and spray area. However, the boosting effect is weaker for diesel DFI spray. Whether it is gasoline or diesel, increasing the injection pressure can further enhance the DFI spray to increase the potential of the spray penetration and spray area. However, it should be mentioned that DFI boosts the spray dispersion under high back pressure conditions but worsens the spray dispersion under low back pressure conditions, especially under flash boiling conditions for gasoline. To a large extent, DFI spray can improve spray characteristics and the fuel/air mixture compared to free spray.

The direct injection spark ignition (DISI) engine has received considerable attention due to its potential to increase the power density of traditional spark ignition engines while significantly improving fuel economy through lean, unthrottled combustion. However, the market introduction of DISI engines operated in a lean combustion mode is inhibited by their unsatisfactory emissions, especially during cold start conditions that make proper mixture formation more challenging. Ethanol-blended gasoline, now a widely used fuel, makes the cold start of a DISI engine more difficult, leading to higher HC and soot emissions because of the high latent heat of vaporization of ethanol relative to gasoline. This work investigated the impact of coolant temperature on the characteristics of combustion and emissions in a stratified-charge DISI engine fueled with an E30 fuel (i.e. 30% ethanol in gasoline), while the coolant temperature was alternated between four levels (45, 60, 75, and 90 degrees C) to simulate different conditions throughout the warm-up process. The experiments showed that the coolant temperature affected the post-spark inflammation time, as well as the speed, intensity, and stability of the combustion process in the engine. When the coolant temperature rose, the engine produced more NOX and less CO, PM and HC. In addition, high-speed direct photography was used to obtain crank-angle resolved images of fuel sprays and flames in the cylinder. As the coolant temperature rose, the liquid spray lengths became shorter, reducing the possibility of wall wetting, and reduced irradiance from soot particles also indicated less nonpremixed combustion. The in-cylinder imaging results are consistent with the observed combustion and emission characteristics and shed light on the underlying processes. Some potential solutions to the emissions challenges faced here could be either raising in-cylinder temperatures by using trapped residuals or modifying the injection schedule, for example by increasing the number of injections or to inject later in the cycle into a higher-density environment.

柴油机冷起动时缸内压缩上止点的温度和密度低,喷雾撞壁量大,且形成的油膜蒸发缓慢,在后续燃烧过程中极易产生池火,不利于碳烟排放控制.本研究在流动式定容燃烧弹中结合背光法和折射率匹配法,研究了柴油机冷起动过程中不同环境温度和密度对附壁油膜生成特性的影响.研究表明环境温度对附壁油膜面积、体积和厚度分布的影响较大,环境温度为500 K时附壁油膜的峰值体积为600 K时的6倍,高环境温度下油膜厚度减小且分布趋向于均匀,600 K条件下不同厚度油膜占比均低于15％.不同环境密度工况下,附壁油膜的蒸发速率较为稳定,高环境密度会促进油膜的蒸发.

实验教学是"新工科"专业培养创新型人才的重要途径.本研究针对能源与动力专业核心课程"内燃机原理"传统实验教学存在的观摩为主、无法独立操作、难以开展极限条件研究、进行自主探索等问题,采用先进的虚拟仿真技术,建设"内燃机原理"实验慕课.通过对真实实验场景的重现,学生可以对设备进行认知和操作,独立完成全部实验过程,在复习和巩固理论课学习成果的同时,掌握开展内燃机性能实验的基本技能.在此基础上,通过课后自主实验设计,进行探索式研究,并结合课堂理论教学环节的讨论分析,展示实验结果.该课程已被认定为"国家虚拟仿真实验教学项目",具有良好的应用前景,不但对"新工科"背景下的研究型教学进行了有益的探索和尝试,也可为虚拟仿真教学资源建设提供参考依据.

Ethanol is regarded as one of the most promising alternative renewable fuels and as well as an oxygenate blending component in gasoline fuels, with widespread usage in many countries around the world. Laminar flame speeds can have strong influence on the stability and operability of Spark-Ignition combustion in certain operating regimes, and so the effects of different initial conditions on laminar combustion characteristics of E30 (gasoline blended with ethanol of 30% liquid volume) were analyzed in a constant-volume combustion vessel using the high-speed Schlieren method. This work presents results for equivalence ratios of 0.7-1.4, dilution ratios of 0%, 5%, 10%, and at different initial temperatures (408, 453 and 498 K) and initial pressures (1, 2 and 3 bar). It can be concluded that the laminar burning velocity has a positive correlation with initial temperature, but negative correlation with initial pressure and dilution ratio. The laminar burning velocity always reaches its maximum value at an equivalence ratio of 1.1 and does not change with varying initial conditions' the adiabatic flame temperature displays a similar variation with the initial conditions. The flame instability of E30-air mixture is enhanced as the initial pressure increases. Flame stability at lean and rich mixtures are exactly opposite at different initial temperature and dilution ratio. The laminar burning velocity was significantly promoted relative to gasoline and E10 by the addition of higher volume fractions of ethanol, highlighting one of the benefits of ethanol's use as a blending component in gasoline fuels.

Flash-boiling in Direct Injection Spark Ignition (DISI) engines is very common. Flash-boiling atomization is one of the most effective ways to generate fully developed atomization and homogeneous mixtures. However, despite the positive effects of flash-boiling, this phenomenon may also lead to negative effects such as longer spray penetration, piston wall wetting, and increased soot emissions, due to increased interactions among the spray plumes which can result in spray collapse and the aforementioned problems. In this study, high-speed direct photography and Refractive Index Matching (RIM) were utilized to investigate the characteristics of n-hexane sprays and impingement using a constant volume vessel. Under low-pressure conditions, flash-boiling drives the collapsed spray to a quick impingement and small spray area. Through the volume distribution of the liquid fuel film acquired by RIM and the spray outline derived from the morphology of images, it was again confirmed that the spray collapse took place not only at a high degree of superheating, but also under conditions of high ambient pressure without flash-boiling. The spray collapse under high pressure conditions is characterized by a late-phase impingement and large spray-swept area. Varying fuel-film behavior was observed following spray-impingement. Under high-density conditions with spray collapse, the fuel film evaporated slowly after the injection, but the higher ambient pressures reduced the total impingement. At low-density conditions with flash-boiling, the resultant fuel-films evaporated more quickly, and reduced ambient pressures reduced the total fuel-film volumes, although flash-boiling could not completely inhibit spray impingement.

The double-solenoid-valve fuel injection system consists of an electronic unit pump and an electronic injector. It can realize the separate control of fuel supply and injection and has the advantages of adjusting pressure by cycle and flexible controlling of the injection rate. The interval angle between the pilot and main injection directly affects the action degree and the characteristics of two adjacent injections, affecting engine performance. This work realizes multiple injection processes on the test platform of a high-pressure double-solenoid-valve fuel injection system, with maximum injection pressure reaching 200 MPa. In this study, the interval between driven current signal of pilot injection termination and that of main injection initiation is defined as the signal interval (DT1), whereas the interval between pilot injection termination and main injection initiation is defined as the injection interval (DT2). The differences between the signal and the injection intervals are calculated, and the variation rule of the difference with respect to the signal interval is analyzed. Results show that the variation rule of the difference with the signal interval first decreases, then increases, and finally decreases. The variation rule of the delay angle from the start of needle movement to the start of fuel injection is found to be the root cause of this rule. The influence of the injection pressure on needle deformation and fuel flow rate of the nozzle results in the variation rule. In addition, the influence of the cam speed, temperature, and pipe length on the difference between the signal and injection interval is determined. This research provides guidance for an optimal control strategy of the fuel injection process.

This paper investigated the effects of hydrogen addition to gasoline surrogates fuel-air mixture on the premixed spherical flame laminar combustion characteristics. The experiments were carried out by high speed Schlieren photography on a constant-volume combustion vessel. Combining with nonlinear fitting technique, the variation of flame propagation speed, laminar burning velocity, Markstein length, flame thickness, thermal expansion coefficient and mass burning flux were studied at various equivalence ratios (0.8–1.4) and hydrogen mixing ratios (0%–50%). The results suggested that the nonlinear fitting method had a better agreement with the experimental data in this paper and the flame propagation was strongly effected by stretch at low equivalence ratios. The stretched propagation speed increased with the increase of hydrogen fraction at the same equivalence ratio. For a given hydrogen fraction, Markstein length decreased with the increase of equivalence ratio; flame propagation speed and laminar burning velocity first increased and then decreased with the increase of equivalence ratio while the peaks of the burning velocity shifted toward the richer side with the increase of hydrogen fraction.

对喷射压力达到250 MPa的超高压共轨燃油系统进行试验研究,得到不同压力与温度条件下高压油管内的压力波动特性.利用喷油器端与共轨管端压力波动的对比计算得出压力波传播速度、燃油与高压油管的总体积弹性模量,并得到了喷射压力在180～250MPa范围内,燃油温度在20～40℃范围内压力波传播速度和总体积弹性模量的计算公式.

为保证新能源车用电机在复杂的道路工况稳定运行,需对电机的动态性能进行有效评估.在电机动态测试系统的基础上,根据电机的阶跃特性曲线完成了系统参数辨识,设计了基于前馈补偿PID的电机动态控制策略,对控制策略的有效性进行了仿真验证,并在LabVIEW的电机动态测试平台上通过FTP72工况验证了控制策略的有效性.实验结果表明,该控制策略可有效地优化系统的动态跟踪性能,提高系统的跟随精度.

为探究喷油系统各参数对发动机性能的影响规律,得出各参数影响规律的作用机理.利用DIESEL-RK建立一台增压柴油机仿真模型,对喷油系统结构参数和喷油策略参数进行优化匹配,依据RK-model对油束发展区域的划分,对比分析燃油在各个区域的分布情况,同时利用燃油喷雾可视化程序,直观观察油束发展特性,分析油束与燃烧室壁面的相互作用规律.结果表明:最佳喷油器孔数、孔径方案为6×0.23mm,最佳喷孔锥角为74°,最佳主喷正时应选择在12°CABTDC.优化方案相对原模型功率增加5.58kW,有效燃油消耗率降低3.35g/kW·h,在满足动力性的基础上,节油效果明显.

Based on Atkinson theoretical cycle ,the performance simulation model of hybrid gasoline engine was built and the compression ratio and valve timing were determined .The requirements of compression ratio for Atkinson gasoline engine has been met with increasing the bumped height of piston top surface (convex combustion chamber) and decreasing the height of cylinder head combustion chamber (compact combustion chamber) .With three‐dimensional CFD analysis ,the combustion and flow characteristics of the two types of combustion chambers were compared .The results show that the compact combustion chamber can produce the higher turbulent kinetic energy in the period of flame kernel formation and diffusion ,accelerate the flame propagation and shorten the combustion duration by 9 .8% ~24 .4% with improved fuel economy .The application of compact combustion chamber in the development of hybrid Atkinson cycle engine is of great value .

For the electronic unit pump (EUP) fuel system ,the influence of opening pressure on fuel injection quantity per cy‐cle was researched .The sensitivity of fuel injection quantity to opening pressure was revealed by calculating the changed per‐centage of fuel injection quantity per cycle to opening pressure and the influencing mechanism of opening pressure on fuel injec‐tion quantity per cycle was researched .The results show that the fuel injection quantity decreases with the increase of opening pressure and is less influenced by the opening pressure with the increase of speed .At each certain speed ,the sensitivity of fuel injection quantity per cycle to opening pressure becomes weaker with the increase of injection pulse width .The fuel injection quantity per cycle is influenced by the opening and closing movement of injector needle valve at low speed and is influenced by the change of effective injection pulse width at medium and high speed .