| 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. |
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