Research On Some Basic Problems Of The Intergrated Design Of The Inlet System Of The Diesel Engine

With the explosive development of Automobile and the deterioration of the environment, energy saving and emission reduction has become a basic policy of1025planning. As for the traditional internal combustion engine (ICE), the key technology to explore its energy saving potential is to improve its combustibility. Especially, diesel engine faces great challenge due to its feature of compression ignition. The realization of combustion optimization requires the cooperation of fuel injection, valve mechanism and other systems, and none of them could work without the inlet system. The inlet system is the main factor to the economic and dynamic properties of diesel engine, as well as its emission characteristic. Recently the inlet system is a hot spot in research, however, there is a common problem that the research on inlet system happened to be independent and scattered, and there are no ensemble development, matching research and collaborative design based on the whole system. Therefore, it could regard that the design cycle of inlet system is still far from perfection.As an exploratory research, one diesel engine was taken as the research object in the dissertation. According to the principle of systematic analysis, numerical research together with experimental examination were completed on the flow characteristic, matching properties and the effects on engine performance. The main contents are as follows:The development of diesel engine inlet system test platform. The test platform of comprehensive flow characteristic of inlet system was established. Though the application of the platform,the independent performance test of inlet components, as well as matching examination could be realized with the platform. The test was regarded as the foundation of systematic research and data-accumulation.The research on inlet system evaluation methodology. The evaluation methods on inlet system performance is compared and analyzed, and the main three constant pressure differential methods were researched to reveal their difference, communication and limitation. Then the common evaluation method was raised upon it according to the principle of similitude and the energy conservation law, providing the standard for the following research.The experiment research on diesel engine inlet system. The reasonable experiment method was settled through the calibration. The test and result analyze of flow characteristic was completed on the research object, so that the systematic matching and the effects on components performance could be revealed.The simulation on diesel engine inlet system. The simulation platform of inlet system was set up to explain the phenomena in the experiment on a systematic level. By the flow test and cylinder visiable result comparison, the feasibility of simulation to predict the inlet system performance is examined.The analysis of the effect of inlet system on engine performance. On the base of1-D simulation model, the relation between the performance of inlet system and that of engine was explored. Then the complete inlet system design cycle was set up and the range of design parameters was settled following the principle of the collaborative design.By researches mentioned above, the following conclusions were achieved:Ⅰ. Since the swirl pressure number could be weakened by the pressure coefficient, the swirl pressure number and swirl rate could be used as the ordinary evaluation parameters of inlet system to achieve the overall measurement. In order to eliminate the effect of independent variable, the weighted average should be taken.Ⅱ. The flow resistance of inlet components has main effect on swirl pressure number. The change of swirl rate agreed with that of swirl pressure number. The flow characteristic of inlet system was mainly affected by the exit position of inlet manifold.Ⅲ. The performance of inlet system could be predicted by S transfer excitation function and MLP neural network of RPROP reverse error transfer, so that the analyze efficiency of inlet system could be improved and the mean absolute error was below3%.Ⅳ. The error between simulation and experiment was less than5%when choosing the right of porous media parameters. The deviation between simulation and the test result decreased along with the increase of the valve lift and could be limited below5%using the weighted average method. The uniformity of inlet system was2.74%, and it has no influence on the uniformity with or without the cylinder head.V. The engine performance could be examined through1-D simulation and error of the parameters such as power and torque could be below5%comparing with test results.VI. Within1-D simulation, the swirl rate could only reflect the flow pattern and the character of the engine, while the swirl pressure number could reflect the pressure loss and the change of the engine.VII. The adjacent angle presented the structure of the filter element should be between three degree to four degree following the principle of the collaborative design.The method combined with experiment and simulation was adopted within the dissertation to analyze the flow characteristic of the inlet system. The evaluation methodology was studied, and the simulation model and test platform of inlet system and engine were built up to provide a firm base and an oriental guide for the collaborative design and matching optimization of inlet system.