【作者】 崔海龙；

【导师】 纪常伟；

【作者基本信息】 北京工业大学 ， 热能工程， 2003， 硕士

【摘要】 根据实验室现有设备，进行了多缸发动机气缸压力采集与燃烧分析系统的研究，该系统由数据采集系统、发动机缸压数据采集和燃烧分析软件组成。基于示功图的信息是研究发动机缸内工作过程的重要手段。通过实测的示功图，经过计算整理可以获得诸如指示功、平均指示压力、最高燃烧压力及其对应曲轴转角、最高压力升高率及其对应曲轴转角、已燃质量分数、燃烧放热率等物理量，可供进一步分析和揭示发动机缸内燃烧过程。高速发展的计算机硬件技术深刻影响着现代气缸压力数据采集系统的发展，高分辨率、高采集率、多通道、无相差和可以任意设定采样频率等特性的A/D板卡及一大批性能优越的相关测试仪器如转角信号发生器、电荷放大器、工控计算机等。数据采集系统选用4个瑞士Kistler公司生产的6117A46型火花塞式缸压传感器，可以同时采集4个缸的气缸压力数据，非常方便分析发动机各缸的燃烧状况。为了保证高速数据采集系统正常工作，减少采样通道系统误差影响，研究了采样通道一致性标定方法。倒拖发动机确定动态上止点的位置，为燃烧分析提供准确的基准信息。考虑实验室本身的干扰信号，采取相应措施，通过硬件、软件两方面减少这方面的影响。使用Visual C++6.0独立开发了发动机缸压数据采集和燃烧分析软件。该软件在软件工程学的指导下，面向对象编程思想贯穿整个开发过程。软件界面设计简单、易操作，独立的模块方便进一步扩充功能。软件设定8个通道可以同时采集上止点信号、曲轴转角信号、1至4气缸压力信号，留有两个备用通道。采集到的数据经过气缸压力数据标定处理和一系列光顺处理后，可绘制出4个缸的示功图、4个缸的相位图、压力升高率图、已燃质量分数等图。实验采集了BN491DQ发动机在不同机油温度（20℃、30℃、40℃）对应不同点火提前角（0oBTDC、6oBTDC、12oBTDC）的气缸压力数据，对冷起动的排放，点火提前角、燃烧循环变动、进气系统差异对冷起动的影响进行了深入研究。稀薄燃烧工况初步研究，调节喷油脉宽气缸最高压力、最高压力升高率及对应曲轴转角的变化，CO、NOx排放明显降低，HC排放在过量空气系数大于1.3时升高。基于以上实验研究，提出一些改进发动机结构和技术发展方向的建议。更多还原

【Abstract】 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, and<WP=5>4 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.更多还原