Research On Cylinder Pressure Acquisition And Combustion Analysis System In Multi-Cylinder Engine

According to current equipment in laboratory, multi-cylinder engine pressure acquisition and combustion analysis system are investigated. The system consists of data acquisition system and multi-cylinder engine cylinder pressure acquisition and combustion analysis software.The information of indicator diagram is important to investigate in-cylinder working process in engine. We can get many physical parameters through indicator diagram acquired in the experiment. Such as indicator work, mean indicated pressure, maximal pressure and corresponding crank angle, maximal rate of pressure rise and corresponding crank angle and mass fraction burned, heat release rate, etc. These physical parameters can analyze and show primary in-cylinder combustion process in engine. Modern cylinder pressure acquisition system is deeply affected by the advanced computer hardware technology. A/D card with the capabilities of high resolution, high sampling rate, non discrepancy and setting sampling rate at will is combined with a lot of excellent measuring equipment such as crank shaft angle encoder, charge amplifier, industrial control computer, etc. We use four type 6117A46 spark plug cylinder pressure sensors made by Kistler corp., Switzerland. Four cylinder pressure data can be sampled and conveniently analyzed to identify the combustion conditions in all cylinders. In order to reduce system errors of sampling channels and insure coherence, sampling channels are calibrated. The engine is motored in search of position of dynamic TDC for combustion analysis needs exact reference information. Considering the different disturbance signals in the laboratory, hardware and software setting measures were taken to reduce these disturbances.Visual C++ 6.0 is used to develop multi-cylinder engine cylinder pressure acquisition and combustion analysis software. Based on Software Engineering guidance, the idea of object-oriented programming runs through whole developing process. The software interface is designed simply and easily operated and independent modules are convenient for extending more functions. Eight channels can sample TDC signals, crank angle signals and 4 cylinder pressure signals, two spare channels are reserved. The acquired data need to be analyzed and treated with some mathematic methods, and4 cylinder indicator diagrams, 4 cylinder phase diagrams, rate of pressure rise diagrams and the burned mass fraction diagrams can be drawn. Cylinder pressure data at different oil temperatures (20℃,30℃,40℃) and corresponding different spark angles (0oBTDC,6oBTDC,12oBTDC ) were sampled in experiments of BN491DQ engine. Emissions at start were measured. Ignition advance angle, combustion cycle variation, intake system difference affect cold start. The deeply research has got some important conclusions. At lean burn condition the research indicated that by adjusting fuel injection pulse width, cylinder maximal pressure, maximal rate of pressure rise and corresponding crank angle fluctuation, NOx, CO emissions were reduced largely, but HC emissions were increased when excess air ratio exceeded 1.3. Based on the above experimental research, suggestions have been made to improve engine structure and control system.