【作者】 李玥；

【导师】 高青；

【作者基本信息】 吉林大学 ， 热能工程， 2008， 硕士

【摘要】 空气通过膜分离富集氧气或氮气,形成富氧或富氮进气,为发动机完善燃烧和排放过程控制提供有效手段。富氧空气促进燃烧,有利于低质燃料、冷起动下的燃烧,对提升动力性、降低排放具有显著作用。富氮空气可以抑制燃烧,减轻NOx排放,被认为是一种替代废气再循环(EGR)的有效方法。本文根据发动机进气富集氧气或氮气的需要,设计了专用可变进气组分分离膜装置,建立正压和负压实验模拟系统。针对增压发动机采用正压法压力模式,以及针对自然吸气发动机采用负压法真空模式,系统研究了富氧气流和富氮气流的分离气流特性,以及分离过程的主要性能。在建立进气组分气体分离系统数学模型基础上,应用此模型对膜分离空气组分(富氧和富氮)过程进行模拟计算,从理论上分析了理想分离系数、氧的渗透系数以及进气量对富氧空气流的影响,并将负压真空模式的模拟结果与实验数据进行了比较。研究结果表明,压力模式具有明显的气体成分浓度与流量逆向反比关系,有利于富集氮气制备调节;真空模式具有明显的富氧气流浓度与流量同向正比关系,富氮空气流的流量和浓度基本不变,有利于富集氧气制备调节。指出供气压力、吸气真空度和分离膜两侧压力差起到决定性的作用,温度具有重要的影响。需要气流调节中多项因素融合,保证流量和浓度协同,满足发动机进气工况要求。更多还原

【Abstract】 The development of engine combustion technology and the enhancement of the emission restriction need improve the combustion process control for higher power, better economics and lower emission. Application of engine is always a weakness in the tableland and the special air environment: low power performance, combustion deterioration, emission increase and engine overheating, even deflagrate, deteriorated stability of work and tempestuously circulation changing.Air could become oxygen-enriched air (OEA) and nitrogen-enriched air (NEA) selectively through organic polymer membrane. This feature has offered engine great potential. Using oxygen-enriched air to support combustion can decrease ignition point of the fuel accelerate combustion speed, facilitate complete combustion, enhance temperature of blaze, decrease exhaust, make much more heat, available and reduce superfluous air coefficient. Using nitrogen-enriched air will reduce the oxygen concentration, Combustion temperature and emissions of NOx combustion. Nitrogen was considered to be an effective method stead of gas recirculation (EGR).Many emissions problem could be effectively solved by variable intake-air composition.Early oxygen-enriched air combustion tests for engine affected by larger sizes of separation membrane device and higher power consumption. The sizes and power consumption of separation membrane device have reduced with the appearance of new membrane materials and the development of membrane separation technology. Now using the membrane separation technology on engine is feasible and attractive.But looking at the progress of research work, to a certain extent, the research of engine performance and the process of membrane separation were independent of each other in the application and research area of variable composition intake-air in engines. The study on variable composition intake-air in engines is to be undertaken, especially the study on characteristics of airflow separated in a variable system. So this paper in allusion to variable composition intake-air system has carried out research and exploration, study on the characteristics of airflow and separation performance in different modes and control debug methods by designing device and simulating the operation system experiment. Lay the foundation for ulterior engine application matching.Meeting the requirement of intake-air in engines, we have designed membrane-based separating variable composition intake-air device and set up respectively experimental simulation systems in the pressure mode and the vacuum mode. Study on compact membrane-based air separating technology and separator, carried out research in membrane-based separating variable composition intake-air device. The pressure mode is in allusion to turbocharged engine and the vacuum mode is in allusion to naturally aspirated engine. This paper studied on characteristics of airflow of oxygen-enriched air and nitrogen-enriched air, indicated that membrane-based separating performance were affected by operating conditions (pressure and operating temperature), also stated the existing problems in practical applications. The conclusions of the experiment are follows:(1) The composition density of both streams is in inverse proportion to the flow mass on the adjustment of pressure mode, but in direct proportion as to the NEA stream and both parameters (composition density and flow mass) of the stream of NEA hardly changed on the adjustment of vacuum mode. Furthermore, it is clear that the pressure mode is fit for the operation of NEA stream and the vacuum mode is fit for the OEA stream.(2) The supply air pressure and inspiration vacuum degree, being equivalent to the pressure difference, play a crucial role in the air separation with membrane and the temperature take an important part. And the temperature also takes an important part. (3) Considering the influence of concentration polarization of membrane, regulate methods played an important role in membrane-based separating process.(4) The correspondence and match of both composition density and flow mass in the certain pressure and temperature must be kept to meet the requirement of intake-air in engines.In this paper, according to variable membrane-based separating air composition intake-air system, we have set up a mathematical model. Using this mathematical model, the process of membrane-based separating air composition (OEA/NEA) was simulated. This paper analyzed the influences of ideal separation factor, permeability coefficient of oxygen and flow of feed air to OEA. The conclusions of the simulated calculation are follows:(1) The concentration of OEA has reduced with permeability coefficient of oxygen’s increasing, the recovery (θ) has increased in evidence.(2) The concentration of OEA has increased with the increasing of the ideal separation factor (αo), the impact is very obvious Compared to the other factors, the recovery (θ) has reduced.(3) The concentration of OEA has a little increase with flow of feed air (Ff) increasing. the recovery (θ) with the flow of feed air (Ff) increasing has decreased in proportion. Maintain the constant OEA flow.(4) Simulation results slightly higher than the experimental data because of neglecting the concentration polarization of membrane in simulation. Error within 5%, meet the requirement.更多还原