氢发动机喷氢控制算法设计

在分析喷氢正时和喷氢量对氢发动机工作性能影响的基础上,设计了喷氢控制算法,并基于Pareto秩和决策偏好相结合的全自动标定算法,进行了喷氢提前角和喷氢脉宽电控系统的软硬件设计。实现了随工况变化动态寻优,使氢发动机动力性、经济性与排放等综合性能达到优化的目标。     

氢发动机排气污染及NOx排放优化控制

研究了在汽油中加入氢气后混合燃料发动机的排放特性,给出了氢汽油混合燃料可以全面改善汽油机的废气排放,然后进行了高压喷射型氢发动机的两个主要运转参数(点火提前角和喷氢提前角)对NOx排放影响的研究。试验表明点火提前角、喷氢提前角对NOx排放量有很大影响。在建立以点火提前角、喷氢提前角、喷氢量为控制变量,以动力性或经济性为性能指标泛函,且排放不超标等为约束条件的氢发动机最优控制模型的基础上,提出了分别以径向基(RBF)网络、模糊神经网络(FNN)求解最优控制模型的新方法,进行了仿真计算和试验数据的对比研究。研究结果给出了两种网络均可以成功取代传统MAP而满足要求。其中以模糊神经网络所用时间较短。     

氢燃料发动机的应用

叙述了氢燃料发动机的特点，结构和工作原理，以及氢燃料的储存及燃烧特性。给出了一些氢燃料发动机的排放试验数据，并与使用其它燃料时进行了比较。主要从发动机的新能源和排放污染等方面，探讨推广氢燃料发动机的必要性及其应用可行性。     

氢动力车研究与发展现状

评述了氢动力车的研究与发展现状，主要介绍了氢燃料的特性、燃氢车发动机的特点，随车贮氢技术以及氢动力车的最近发展动态。     

氢发动机性能的改进

本文论述了氢发动机的最新研究成果，着重描述了氢的储存和混合气形成及点火等技术问题，并提出了相应的措施。试验表明，采用氢的高压喷射、火花点火，并调整最佳点火正时，就能获得良好的经济和动力性能     

点火提前角对氢发动机性能的影响及智能控制技术

进行了进气管喷射的氢发动机点火提前角对发动机性能影响的研究，试验指出了点火提前角对氢发动机动力性，经济性和排放性能有较大影响。建立了模糊神经网络控制系统对点火提前角进行优化控制，建立了一个改进的模糊神经网络系统代替传统的试验方法来求解氢发动机的最佳点火提前角(MAP)。仿真和试验结果的对比研究给出该方法具有较高的运行精度。     

氢发动机工作过程的数值模拟研究

为了分析和研究氢发动机的运行特性，预测多种参数变化对性能的影响，对氢发动的燃烧过程建立零维模型，进行数值模拟。试验表明，模型的计算值和试验值具有良好的一致性，模拟计算弥补了试验测试中的不足，可以从更深层次地认识氢发动机的运行特性和规律。     

氢燃料发动机性能参数的研究

针对氢作为发动机燃料的优越性以及氢燃料发动机的特点、技术发展趋势进行了简要概括,并在此基础上,结合实验研究,对压缩比、当量比、过量空气系数对氢燃料发动机性能的影响进行了分析研究.     

氢发动机电控喷氢系统的设计

将奇瑞SQR480汽油机改装为氢发动机,开发了以Microchip公司PIC16F877单片机为核心的多点进气道内顺序喷射的电控喷氢系统.采用高速开关型数字电磁阀作为电控系统的执行元件,运用PWM驱动方式来控制实际的喷氢量.采用模块化方法设计了系统控制软件,开发了卖时监控系统.仿真结果表明:该系统能较好地实现对喷氢量的控制.     

氢-汽油双燃料发动机电控喷氢-喷油系统的设计

把嘉陵600汽油燃料摩托发动机改装为汽油-氢气双燃料发动机,开发了以freescale公司MC9S12XS128单片机为核心的单点进气道喷射的电控喷氢系统。采用智能化芯片MC33810对高速开关型数字电磁阀进行控制,采用输出比较对喷氢量和喷油量进行控制。使用定时监控系统并运用模块化的方法来对系统的软件进行设计。试验结果证明,这套系统能够很好地实现对喷油和喷氢量的控制。     

混氢对怠速工况发动机循环变动和排放的影响

针对汽油机怠速时循环变动大、排放高的问题,在一台加装了电控氢气喷射系统的1.6L汽油机上就混氢对发动机怠速性能的影响进行了试验研究。在怠速条件下,通过自主开发的电子控制单元调整氢气与汽油的喷射脉宽,使进气中混氢体积分数从0%逐渐增加至6.52%,同时减少汽油的喷射脉宽,以保证混氢后发动机仍工作在理论过量空气系数条件下。试验结果表明,混氢后发动机火焰发展期和快速传播期缩短;平均指示有效压力的循环变动系数由原机的9.97%减少至混氢体积分数为6.52%时的4.93%。NOx排放随混氢分数增加而减少;在混氢体积分数小于4.88%时,HC与CO随混氢比的增加而减少,但当混氢分数大于4.88%时,HC与CO排放再次升高。     

An experimental investigation on performance and emissions study with port injection using diesel as an ignition source for different EGR flow rates

Exhaust gas recirculation, EGR, is one of the most effective means of reducing NO_x emissions from IC engines and is widely used in order to meet the emission standards. In the present work, experimental investigation has been carried out to study the NO_x reduction characteristics by exhaust gas recirculation in a dual fueled engine using hydrogen and diesel. A single cylinder diesel engine was converted to operate on hydrogen-diesel dual fuel mode. Hydrogen was injected in intake port and diesel was injected directly inside the cylinder. The injection timing and injection duration of hydrogen were optimized initially based on the performance and emissions. It was observed that start of injection at 5° before gas exchange top dead center (BGTDC) and injection duration of 30° crank angle gives the best results. The flow rate of hydrogen was optimized as 7.5 lpm for the best start of injection and injection duration of hydrogen. Cold exhaust gas recirculation technique was adopted for the optimized injection parameter of hydrogen and flow rate. Maximum quantity of exhaust gases recycled during the test was 25% beyond this the combustion was not stable resulting in increase in smoke.     

基于遗传算法的氢发动机优化控制研究

建立了氢发动机动力性、经济性及排放特性与发动机运转参数间的优化控制模型,并通过Pareto秩与决策偏好相结合的多目标优化算法,在寻优过程中使多个目标的优化过程并行进行,实现了解的Pareto最优性,并使解向决策偏好的方向收敛,提高了收敛速度;同时通过加权函数实现了决策偏好随氢发动机运转工况的动态调整,从而将分变量、分目标、分工况的控制统一为单目标的集成优化控制技术.为解决氢燃料发动机优化目标的多样化和复杂化控制问题,以及进一步提高控制精度开辟了新途径.     

An insight on hydrogen fuel injection techniques with SCR system for NOX reduction in a hydrogen–diesel dual fuel engine

Internal combustion engines continue to dominate in many fields like transportation, agriculture and power generation. Among the various alternative fuels, hydrogen is a long-term renewable and less polluting fuel (Produced from renewable energy sources). In the present experimental investigation, the performance and emission characteristics were studied on a direct injection diesel engine in dual fuel mode with hydrogen inducted along with air adopting carburetion, timed port and manifold injection techniques. Results showed that in timed port injection, the specific energy consumption reduces by 15% and smoke level by 18%. The brake thermal efficiency and NO_X increases by 17% and 34% respectively compared to baseline diesel. The variation in performance between port and manifold injection is not significant. The unburnt hydrocarbons and carbon monoxide emissions are lesser in port injection. The oxides of nitrogen are higher in hydrogen operation (both port and manifold injection) compared to diesel engine. In order to reduce the NO_X emissions, a selective catalytic converter was used in hydrogen port fuel injection. The NO_X emission reduced upto a maximum of 74% for ANR (ratio of flow rate of ammonia to the flow rate of NO) of 1.1 with a marginal reduction in efficiency. Selective catalytic reduction technique has been found to be effective in reducing the NO_X emission from hydrogen fueled diesel engines.     

Emission and performance estimation in hydrogen injection strategies on diesel engines

Recently, the increasing demand for energy requires the use of alternative fuels, especially in fossil fueled power systems. As a promising alternative fuel for next-generation diesel engines that utilize fossil fuel, hydrogen fuel is one step ahead due to its positive properties. In this study, the effects of hydrogen on the performance of a diesel engine have been numerically investigated with respect to different injection ratios and timings. The numerical results of the study for 25% load conditions on a single-cylinder, four-stroke diesel engine have been validated against experimental data taken from literature and good agreement has been observed for pressure results. Emission parameters such as NO_x, CO and performance parameters such as cylinder temperature, pressure, power, thermal efficiency and IMEP are presented comparatively.The results of numerical analyses show that the maximum pressure, temperature and heat release rate are observed with injection ratio of H15 and early injection timing (20° CA BTDC). Besides that, engine power, thermal efficiency and IMEP are greatly improved with increasing injection ratio and early injection timing. Although combustion chamber performance parameters improve with rising the hydrogen injection ratio, higher NO_x emissions have also been detected as a negative side effect. Furthermore, while early injection timing increases diesel engine performance, it also causes an increase in NO_x emissions. Therefore, precise determination of injection timing together with the optimum amount of hydrogen has revealed that it brings crucial improvement in engine performance and emissions.     

Multi-objective optimization of the engine performance and emissions for a hydrogen/gasoline dual-fuel engine equipped with the port water injection system

Hydrogen is one of the most promising options being considered as the fuel of future. However, injection of hydrogen into modern gasoline fueled engines can cause some issues such as power loss. This study, therefore, aims to address this challenge in a simulated hydrogen/gasoline dual-fueled engine by developing a novel and innovative approach without possible side effects such as NOx increment. To achieve this goal, the impacts of water injection and the start of the combustion (SOC) modification in a gasoline/hydrogen duel fueled engine have been rigorously investigated. In current methodology, an engine is simulated using AVL BOOST software and the model is validated against the experimental data. The Latin Hypercube design of experiments method was employed to determine the design points in 3-dimensional space. Due to the existing trade-off between NOx and BMEP, multi-objective optimization using genetic algorithm (GA) was implemented to determine the optimum values of water injection and SOC in various hydrogen energy shares and the effects of optimum design parameters on the main engine performance and emission parameters were investigated. The results showed that the proposed solution could recover the brake mean effective pressure (BMEP) and in some hydrogen energy shares even increase it above the level of single fueled gasoline engine with the added benefit of there being no increase in NOx compared to the original level. Furthermore, other emissions and engine performance parameters are improved including the engine equivalent Brake specific fuel consumption (BSFC) which was shown to increased up to 4.61%.     

Hydrogen impacts on performance and CO2 emissions from a diesel power generator

This work investigates the performance and carbon dioxide (CO₂) emissions from a stationary diesel engine fueled with diesel oil (B5) and hydrogen (H₂). The performance parameters investigated were specific fuel consumption, effective engine efficiency and volumetric efficiency. The engine was operated varying the nominal load from 0 kW to 40 kW, with diesel oil being directly injected in the combustion chamber. Hydrogen was injected in the intake manifold, substituting diesel oil in concentrations of 5%, 10%, 15% and 20% on energy basis, keeping the original settings of diesel oil injection. The results show that partial substitution of diesel oil by hydrogen at the test conditions does not affect significantly specific fuel consumption and effective engine efficiency, and decreases the volumetric efficiency by up to 6%. On the other hand the use of hydrogen reduced CO₂ emissions by up to 12%, indicating that it can be applied to engines to reduce global warming effects.     

Effect of hydrogen addition on the idle performance of a spark ignited gasoline engine at stoichiometric condition

With regard to the improvement of efficiency, combustion stability, and emissions in a gasoline engine at idle condition, an experimental study aimed at improving engine idle performance through hydrogen addition was carried out on a 4-cylinder gasoline-fueled spark ignited (SI) engine. The engine was modified to be fueled with the mixture of gasoline and hydrogen injected into the intake ports simultaneously. A self-developed electronic control unit (DECU) was dedicatedly used to control the injection timings and injection durations of gasoline and hydrogen. Other parameters, such as spark timing and idle valve opening, were controlled by the original engine electronic control unit (OECU). Various hydrogen enrichment levels were selected to investigate the effect of hydrogen addition on engine speed fluctuation, thermal efficiency, combustion characteristics, cyclic variation and emissions under idle and stoichiometric conditions. The experimental results showed that thermal efficiency, combustion performance, NO_x emissions are improved with the increase of hydrogen addition level. The HC and CO emissions first decrease with the increasing hydrogen enrichment level, but when hydrogen energy fraction exceeds 14.44%, it begins to increase again at idle and stoichiometric conditions.     

氢内燃机缸内燃烧特性

介绍了氢内燃机试验分析系统,对比和分析了不同工况下的氢内燃机缸内燃烧特性,总结了不同运行参数下氢内燃机的燃烧特点.试验结果表明:由于燃烧速度较高,氢内燃机可以在上止点或上止点后点火,此时指示效率下降并不明显.在中低转速时,氢内燃机可以适应不同转速,能够及时燃烧.油门开度对氢内燃机的影响很大,小油门开度时残余废气多,氢气的浓度降低,使氢气燃烧速度受到影响,指示热效率降低,循环变动增加.