【作者】 刘博；

【导师】 邓康耀；

【作者基本信息】 上海交通大学 ， 动力机械及工程， 2011， 博士

【摘要】 提高柴油机的增压压力以实现高平均有效压力是降低燃油消耗率及C02温室气体排放的一个有效手段。另一方面,面对越来越严格的有害物排放法规,较高的增压压力也为废气再循环、米勒循环和均质燃烧等技术措施提供了足够新鲜充量的保障。因此,柴油机的增压压力有必要进一步的提高,宽转速运行范围的柴油机与高增压系统的优化匹配成为亟须解决的问题。可调二级涡轮增压系统集合了二级增压和可调增压技术的优点,能够兼顾高压比和宽流量范围,是极具潜力的一种的涡轮增压技术,为此本文对其开展了相关研究。首先应用等效增压器的概念对柴油机可调二级涡轮增压系统进行了理论研究,建立了可调二级涡轮增压系统的等效增压器模型,得到了基于旁通流量比的等效涡轮流通面积表达式和基于旁通流量比与涡轮焓降比的等效增压器效率的表达式。等效增压器效率表达式从经济性角度指明了排气能量分配与效率的相适应可以实现增压系统效率的最大化。调节等效涡轮流通面积可以使增压系统适应更宽的发动机转速范围,基于调节能力的要求提出并研究了可调二级涡轮增压系统的匹配方法,揭示了可调二级涡轮增压系统总压比、压比分配、低高压级涡轮流通面积比以及系统调节能力等关键参数间的相互关系。设计了涡轮旁通阀和压气机旁通阀等关键部件,建立了可调二级涡轮增压柴油机以及试验台架。进行了匹配方法的验证性试验,证明了基于调节能力的匹配方法的适用性。对可调二级涡轮增压柴油机进行了全工况稳态试验,分析了高压级压气机旁通阀的开启时刻特性,以及高压级涡轮旁通阀对增压系统的调节特性和对发动机油耗性能和烟度排放的影响规律。在此基础上,提出了济性和动力性两种调节规律。结合进一步的瞬态试验对两种调节规律进行了综合评价:稳态性能方面,经济性调节规律优于动力性调节规律;瞬态特性方面,直接开环应用调节规律时,在模拟起步过程的加速加载加载工况和中低转速范围内(900 r/min和1100r/min)的定转速加载工况时,动力性调节规律会取得较快的响应和较低的瞬态烟度排放,而在中高转速范围内的1400r/min转速线上的加载工况试验则表明,由于存在高压级增压器的旁通过程使得动力性调节规律的优势不再明显。对增压压力闭环控制策略进行了计算研究。应用仿真模型对涡轮旁通阀开度命令到增压压力的动态过程进行了系统辨识,基于区域线性化的方法,设计了参数可变PI反馈控制器结合前馈模块的控制系统。对1400r/min的加载工况进行计算分析表明,动力性型调节规律结合PI反馈控制器的闭环控制系统实现了最快的响应过程,而且即使是经济性调节规律结合PI反馈控制器的闭环控制系统也比直接应用动力性调节规律的开环控制响应要快,证明闭环控制可以实现经济性和动力性的兼顾。更多还原

【Abstract】 Increasing the break mean effective pressure of diesel engine through improving the boost pressure is one of the effective ways of reducing fuel consumption (aka. carbon emission reducing). Meanwhile, the higher boost pressure guarantees enough fresh charge for the techniques of Exhaust Gas Recirculation (EGR), Miller Cycle and Homogeneous Charge Compression Ignition (HCCI) which are valid to fulfil the increasing strict regulation of harmful emission. Thus the boost pressure of diesel engine need to be improved further, however the problem of matching the wide speed range diesel engine and the high pressure turbocharging system has to be resolved firstly. The regulating two stage (R2S) turbocharging system, that combines the advantages of two stage turbocharging and regulating turbocharging, can provide high boost pressure level over a wide range of engine speed. For the purpose of knowing a potential turbocharging technology, a comprehensive study will be carried out on regulating two stage turbocharging system in this thesis.First, theoretical study on the regulated two stage turbocharging system is conducted based on the equivalent turbocharger concept. Expressions for the equivalent turbine flow area and the equivalent turbocharger efficiency of the R2S system were derived. The equivalent turbocharger efficiency expression gives a criterion for matching of the R2S system based on the economy principle which is making more exhaust energy conversion at the stage with higher turbocharger efficiency. The equivalent turbine flow area can be used to analyze the regulating ability of the R2S system. Based on the regulating ability requirement, a new method for match of R2S system and diesel engine has been developed which clearly reveals the correlation between the total pressure ratio, the distribution of pressure ratio between the two stages, the turbine flow area ratio of low pressure stage to high pressure stage and the system regulating ability.For Further Study, key components of the R2S system are designed, furthermore the prototype engine and test bench are established. Firstly, a proof experiment is conducted to verify the new match method of R2S system, which turns out that the method is appropriate. After that, comprehensive testes focus on the steady performance are executed within the whole operation range of the engine, and the open time of the compressor bypass valve which is parallel located with the high pressure stage compressor and the regulating characteristics of the turbine bypass valve which is parallel located with the high pressure stage turbine are analyzed. On the basis of the above analysis, two regulating MAP of R2S system whose objective is maximum of economy or dynamic respectively are proposed. Combined with the further load transit and starting tests, conclusions can be made that the regulating MAP of economy is superior to the regulating MAP of dynamic with regard to the steady performance in open loop control mode. However concerning the transit performance, the regulating MAP of dynamic can achieve more rapid respond and lower smoke than the regulating MAP of economy during the load transit test of 900 r/min and 1100r/min which are both in the low-middle engine speed range. But the result from the load transit test of 1400 r/min which is in the middle-high engine speed range reveal that superiority of the regulating MAP of dynamic isn’t obvious any more because of the bypass process of the high pressure turbocharger.To make up the shortage of using regulating MAP in open loop mode directly, close loop boost pressure control strategy is studied numerically on a mean value model at the last chapter. System identification from turbine bypass open command to boost pressure is conducted under different operation points, based on which a control system consist of a gain-scheduling PI feedback controller and a feedforward module is designed. Simulation results from load transit process at 1400 r/min reveal that, control system consist of PI feedback controller and the regulating MAP of dynamic achieve the fastest respond process, even the control system consist of PI feedback controller and the regulating MAP of economy is faster than open loop using of the regulating MAP of dynamic, which means that the close loop boost pressure control strategy can realize the economy and dynamic simultaneously.更多还原