柴油/汽油反应活性控制压燃发动机喷油协调控制与排放特性研究

对某4缸高压共轨柴油机进气道进行改造,搭建了柴油/汽油双燃料反应活性控制压燃(reactivity controlled compression ignition,RCCI)发动机专用试验台架,设计了柴油/汽油双燃料RCCI燃烧汽油喷射控制策略,实现了全工况下汽油与柴油的协调喷射控制,系统地研究了不同运行工况下,不同汽油替代率对柴油机燃烧与排放性能的影响规律。结果表明:采用柴油/汽油双燃料RCCI燃烧控制策略,发动机可在其运行工况范围内实现高效清洁燃烧,随着汽油替代率的增加,发动机缸内最高压力逐渐增大,缸压峰值出现时刻推迟,放热率峰值降低,燃烧持续期延长,燃油消耗率降低,有效热效率升高,全碳氢、CO排放增加,NOx和碳烟排放降低。     

燃烧系统参数对增压中冷柴油-天然气双燃料发动机排放特性和经济性影响的实验研究

将一台6缸、增压中冷柴油机改装为混合器进气方式的柴油—天然气双燃料发动机，对其燃烧系统参数对双燃料发动机排放和经济性的影响进行了实验研究，包括引燃柴油喷油时刻、天然气替代率、中冷后进气温度的影响。双燃料发动机的排放与空燃比及燃烧系统参数密切相关。替代率增加时，排气烟度降低，HC排放升高，当量燃油消耗率升高，CO排放在替代率较小时随替代率增加而升高，但在替代率较高时随替代率增加而略有降低。替代率对NOx排放的影响则与发动机工况有关，在最大转矩和低速大负荷工况，空燃比值较小，NOx排放随替代率的升高而增大；在标定功率工况，空燃比较大，NOx排放随替代率的升高而减小。提前角减小，NOx排放降低。中冷后温度升高，碳烟排放和NOx排放升高，HC和CO排放降低，当量燃油消耗率降低。研究结果表明，采用增压中冷技术、提高CNG替代率、减小引燃柴油喷油提前角，能够有效地降低双燃料发动机的有害排放物。     

汽油/柴油双燃料发动机的低速高负荷扩展

在一台改造的单缸发动机上开展了进气道喷射汽油、缸内直喷柴油的双燃料燃烧模式的低速高负荷扩展研究.结果表明:汽油/柴油双燃料发动机高负荷工况需配合高比例废气再循环(EGR),当采用原机相同工况的进气压力时,由于进气量不足抑制了高EGR率的应用,导致高NO_x排放.通过提高进气压力,稳定燃烧对应的柴油喷油时刻范围变宽,汽油比例上限提高,降低了燃烧控制的难度.但由于汽油/柴油双燃料发动机的汽油高度预混合特性及直喷柴油引起的局部不均匀性,导致缸内最大压力升高率(MPRR)及碳烟排放偏高,限制了其向更高负荷的扩展.在提高进气压力的同时,通过提高汽油比例及EGR率,实现了在限定条件下向更高负荷的扩展及燃油消耗率的降低.相比于原柴油机,汽油/柴油双燃料发动机高负荷扩展的受限因素由进气增压前的高NO_x排放转变为增压后的高压力升高率.     

乙醇/柴油双燃料发动机的燃烧及排放特性研究

在柴油机试验台架上,研究了进气道口电控喷射乙醇,缸内直喷柴油引燃乙醇的方式,开发了电控乙醇/柴油双燃料发动机。研究了乙醇/柴油双燃料模式的燃烧及排放特性.随着引燃柴油量的降低,最大爆发压力下降,NOx和排烟下降幅度加大,但THC和CO排放均有升高.通过调整控制参数如乙醇/柴油的喷射比例,可使发动机达最佳燃烧状态及较低的有害排放,因此说乙醇/柴油双燃料模式是一种有前途的、可行的发动机发展方向.     

甲醇/柴油双燃料发动机的性能

在一台柴油机基础上，采用气道口电控喷射甲醇，缸内柴油引燃甲醇的方式，开发了电控甲醇／柴油双燃料样机，并通过发动机台架实验，研究了柴油／甲醇双燃料燃烧模式在燃烧特性、燃油经济性及排放性能方面的特点．与原发动机相比，双燃料模式的最高爆发压力下降，压力升高率上升，排烟和NOx大幅度下降，但THC和CO排放均升高．该方法能使甲醇喷射量得到精确控制以便燃烧达到最佳状态，是甲醇／柴油双燃料发动机可行的技术方案．     

柴油/天然气双燃料发动机数值优化

利用CONVERGE搭建了柴油/天然气双燃料发动机三维数值模拟平台,在大负荷工况下研究了压缩比和不同喷油策略对发动机燃烧性能的影响．研究结果表明,相同条件下,降低压缩比到14.8能够有效降低最大压升率,从而有助于进一步增大天然气的替代比例．采用单次喷射策略时,通过提高喷射压力并提前柴油直喷时刻,在最大压升率限值内,能在85%天然气替代比例的同时获得48.1%的热效率．采用两次喷射策略时,随着预喷油量的增加,缸内着火时刻提前．并且预喷时刻提前能够有效降低最大压升率．对比发现,与单次喷射策略相比,两次喷射策略能够实现更为灵活的缸内燃烧控制,获得90%的天然气替代比例．最终,两次喷油策略实现了48.4%的最高热效率．     

LPG/柴油双燃料发动机压缩比优化研究

采用燃料复合供给方式 ,在单缸直喷式柴油机上进行了LPG/柴油双燃料发动机压缩比的优化试验研究 ,对比分析了使用纯柴油和LPG/柴油双燃料的燃烧特性 ,着重研究分析了双燃料发动机在不同压缩比下的最高燃烧压力、最大压力升高率、压力循环波动及燃烧放热率 ,并以此为依据优选了双燃料发动机的压缩比。试验结果表明 :降低压缩比后 ,双燃料发动机的最高燃烧压力及最大压力升高率均有较大降低 ,同时压力循环波动变小 ,但滞燃期、燃烧持续期都会有所增加。经过优化 ,压缩比确定为 14.5时 ,ZH110 5W柴油机改燃LPG/柴油双燃料后在高负荷工况下无严重爆震现象 ,压力循环波动较小 ,且经济性较好 ,热效率损失不大     

汽油/柴油双燃料低温燃烧过程和排放的试验

在转速为1,900,r/min、平均指示压力为0.8,MPa的工况下,通过一台单缸高压共轨柴油机进行了不同参数对汽油/柴油双燃料低温燃烧过程影响的试验,结果表明:在给定的试验工况及边界条件下,通过调整汽油和柴油的混合比例、EGR率、柴油喷射压力及喷射正时,可以实现燃烧过程的控制和优化,发动机热效率显著提升,氮氧化物(NOx)和碳烟(soot)排放大幅降低.在汽油比例为90%,、EGR率为40%,的条件下,发动机热效率随柴油喷射压力的升高有所改善,HC排放呈降低趋势,soot排放则一直保持极低水平,但NOx排放升高.在此基础上进一步对柴油喷射正时进行了试验,结果表明:柴油喷射正时对该工况下的低温燃烧过程有明显影响,若柴油喷射靠近上止点,其燃烧过程受柴油传统扩散燃烧影响;若喷射正时过于提前,其燃烧过程受预混燃烧控制.通过优化第二次柴油喷射正时,发动机指示热效率达到了53.2%,.     

增压中冷柴油-天然气双燃料发动机燃烧特性的实验研究

对天然气替代率、引燃柴油喷油时刻和中冷后进气温度等燃烧系统参数对增压中冷柴油—天然气双燃料发动机燃烧特性的影响进行了实验研究。研究结果表明：增压中冷柴油—天然气双燃料发动机的燃烧放热速率比纯柴油快，引燃柴油的着火时刻和缸内燃料空燃比值决定着双燃料发动机的燃烧特性，即着火时刻在上止点前且空燃比值较小时，其燃烧接近于定容燃烧过程，随着天然气替代率的升高，缸内最大爆发压力和最高燃烧温度升高；而着火时刻在上止点后且空燃比值较大时，其燃烧接近于等压燃烧过程，随着天然气替代率升高，缸内最大爆发压力和最高燃烧温度降低。最大爆发压力、最高燃烧放热率和最高燃烧温度随引燃柴油喷油提前角的增大而升高；而随着进气温度升高，最大爆发压力和缸内温度增大。     

甲醇替代率对双燃料发动机燃烧及其循环变动的影响

为研究甲醇/柴油双燃料发动机甲醇替代率对燃烧及其循环变动的影响,通过在单缸柴油机上加装进气道甲醇喷射系统,进行了不同甲醇替代率的试验研究。研究表明,随着甲醇替代率增加,缸内着火时刻推迟,放热率双峰现象逐渐消失,放热率峰值、最高燃烧压力和最大压力升高率均增加。甲醇替代率对不同工况下指示热效率的影响不同,低速工况指示热效率随甲醇替代率的增加而降低,高速高负荷工况指示热效率随甲醇替代率的增加而略有增加。不同工况下的排放影响也存在明显差异,随甲醇替代率的增加,低速低负荷工况排放变化较小,而在高速高负荷下排放变化大。甲醇替代率对燃烧循环变动影响表明,低速低负荷循环变动随甲醇替代率增加而明显增加,当替代率增加至28.7%时,峰值压力的循环变动率增加2.5%,峰值压力对应曲轴转角分布也更加分散。     

Thermodynamic analysis of a Stirling engine including dead volumes of hot space, cold space and regenerator

This paper provides a theoretical investigation on the thermodynamic analysis of a Stirling engine. An isothermal model is developed for an imperfect regeneration Stirling engine with dead volumes of hot space, cold space and regenerator that the regenerator effective temperature is an arithmetic mean of the heater and cooler temperature. Numerical simulation is performed and the effects of the regenerator effectiveness and dead volumes are studied. Results from this study indicate that the engine net work is affected by only the dead volumes while the heat input and engine efficiency are affected by both the regenerator effectiveness and dead volumes. The engine net work decreases with increasing dead volume. The heat input increases with increasing dead volume and decreasing regenerator effectiveness. The engine efficiency decreases with increasing dead volume and decreasing regenerator effectiveness.     

Investigation on power output of the gamma-configuration low temperature differential Stirling engines

This paper provides a study on power output determination of a gamma-configuration, low temperature differential Stirling engine. The former works on the calculation of Stirling engine power output are discussed. Results from this study indicate that the mean pressure power formula is most appropriate for the calculation of a gamma-configuration, low temperature differential Stirling engine power output.     

The ANU solar thermal steam engine: performance analysis

This paper describes the results of a series of experiments that were performed to define the performance of the uniflow piston-operated valve steam engine developed by the Australian National University (ANU) for solar thermal applications. The results are fitted by least-squares regression to simple power series expressions that correlate the power output and engine inlet pressure to steam temperature, thermal power input and condenser pressure. The performance of the engine is examined by comparison with an idealized frictionless and quasi-static model. The idealized model is used to assess the relative importance of the effects of friction and non equilibrium thermodynamic conditions in the engine. The exergetic performance of the ideal engine is examined to demonstrate the fundamental limitations of this engine technology. It is concluded that high piston/cylinder forces during the first stages of expansion pose a significant barrier to the enhancement of engine efficiency through the use of higher temperatures and expansion ratios. © 1998 John Wiley & Sons, Ltd.     

小型发动机燃用汽油、乙醇和LPG燃料的排放对比

对125mL发动机燃用汽油、乙醇和液化石油气(LPG)时的过量空气系数和点火提前角与排放性能之间的关系进行了试验研究．指出了影响这三种燃料发动机排放性能的敏感参数的合理取值范围．通过对比试验，验证了发动机燃烧乙醇可降低NOx排放浓度．发动机燃烧LPG时，低HC排放的空燃比范围比其它两种发动机空燃比范围广．研究结果可为小型汽油、乙醇和LPG发动机参数匹配提供参考。     

国产航空斯贝发动机的工业及船用化发展

本文介绍了改型航空发动机应用概况,提出了航空斯贝发动机作母型机改装为工业和船用系列化机型的途径及优点。     

Energy system feasibility study of an Otto cycle/Stirling cycle hybrid automotive engine

The aim of this study was to investigate the feasibility of utilising a Stirling cycle engine as an exhaust gas waste heat recovery device for an Otto cycle internal combustion engine (ICE) in the context of an automotive power plant. The hybrid arrangement would produce increased brake power output for a given fuel consumption rate when compared to an ICE alone. The study was dealt with from an energy system perspective with design practicalities such as power train integration, location of auxiliaries, manufacture costs and other general plant design considerations neglected. The study necessitated work in two distinct areas: experimental assessment of the performance characteristics of an existing automotive Otto cycle ICE and mathematical modelling of the Stirling cycle engine based on the output parameters of the ICE. It was subsequently found to be feasible in principle to generate approximately further 30% useful power in addition to that created by the ICE by using a Stirling cycle engine to capture waste heat expelled from the ICE exhaust gases over the complete range of engine operating speeds.     

A four power-piston low-temperature differential Stirling engine using simulated solar energy as a heat source

In this paper, the performances of a four power-piston, gamma-configuration, low-temperature differential Stirling engine are presented. The engine is tested with air at atmospheric pressure by using a solar simulator with four different solar intensities as a heat source. Variations in engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number obtained from the testing of the engine is also investigated. The results indicate that at the maximum actual energy input of 1378 W and a heater temperature of 439 K, the engine approximately produces a maximum torque of 2.91 N m, a maximum shaft power of 6.1 W, and a maximum brake thermal efficiency of 0.44% at 20 rpm.     

Performance of a twin power piston low temperature differential Stirling engine powered by a solar simulator

This paper provides an experimental investigation on the performance of a low-temperature differential Stirling engine. In this study, a twin power piston, gamma-configuration, low-temperature differential Stirling engine is tested with non-pressurized air by using a solar simulator as a heat source. The engine testing is performed with four different simulated solar intensities. Variations of engine torque, shaft power and brake thermal efficiency with engine speed and engine performance at various heat inputs are presented. The Beale number, obtained from the testing of the engine, is also investigated. The results indicate that at the maximum simulated solar intensity of 7145 W/m², or heat input of 261.9 J/s, with a heater temperature of 436 K, the engine produces a maximum torque of 0.352 N m at 23.8 rpm, a maximum shaft power of 1.69 W at 52.1 rpm, and a maximum brake thermal efficiency of 0.645% at 52.1 rpm, approximately.     

三角转子发动机的特点及其发展概况综述

介绍了新型发动机——三角转子发动机的结构特点和工作过程,在与往复式发动机进行比较的基础上阐述了转子发动机的工作特点,并介绍了转子发动机的发展新技术和国内外发展状况,以及应努力的方向。     

我国高效利用燃料乙醇的建议

对比国外的发展情况,结合国情建议在柴油机上使用乙醇并提出具体的技术方法。在柴油机上使用乙醇,可以大幅度提高燃料效率,减少二氧化碳排放,其他排放也能随之改善。