The Development And Application Of Data Acquisition And Combustion Analysis System Of Diesel Engine

Facing the reality of the severe energy crisis and environmental pollution, a reasonable organization and optimize the combustion process in cylinder has become one of the most important methods to realize an internal combustion engine with a high efficiency and energy saving, low emission pollution in the future, and whether it can accurately measure the dynamic parameters in the combustion process, and realize the combustion process analysis of heat release or not is the research foundation to design, improve and troubleshoot an internal combustion engine.Combined with the existing hardware resources and the experimental requirements, the parts selection, positioning installation etc. has been introduced in detail and at the same time the data acquisition system hardware platform also have been set. Based on the LabVIEW virtual instrument development platform, the data acquisition and combustion analysis software system have been developed successfully. In order to position the TDC accurately and make sure the real-time and continuity and accuracy of the sample data, a TDC positioning scheme has been proposed based on different trigger condition. In the process of data acquisition, the accurate positioning of TDC has been discussed, and at the same time, the cylinder pressure data also been smoothed and averaged in the subsequent data processing with the method of five point three times smoothing. The experimental result shows that with this combustion test system, we could measure and record all kinds of steady and instantaneous state parameters during the engine operation process, such as the temperature and pressure of kinds of fluids, the instantaneous and average speed, the combustion pressure in cylinder and emissions, etc. In addition, the pressure rise rate, average temperature in cylinder, instantaneous heat release rate and total heat release rate can also be calculated based on the analysis and calculation of indicator diagram.At the same time, in order to explore the influence on diesel engine combustion process under different operation parameters in idle, take the DK4 A type high pressure common rail diesel engine as the research object with the using of the data acquisition and combustion analysis system of diesel engine, the idle cycle fluctuation characteristics has been researched, and the results shows that: the injection timing has a two-sided influence on the combustion, with a too the front(-12°CA) or back(-2°CA) of the fuel injection timing can make the poor stability of the combustion in cylinder, and the coefficient of variation of maximum explosion pressure comes up; while the cyclic variation is sensitive to the coolant temperature, a higher coolant temperature can improve the progress of fuel atomization, evaporation and mixed and shorten the combustion delay period, and at the same time it also can reduce the cyclic variation effectively; improving the injection pressure in a certain range(such as 40MPa) can make the oil beam has a higher kinetic energy to get through the fluid layer and accelerate the progress of oil droplets and spray diffusion, the idle cyclic variation also get lower; while it is hard to keep a higher injection pressure with more useful work, and the higher injection pressure(such as 80MPa) makes the combustion get more uncontrolled and variable.