Research On Knock’s Test And Analysis Of Two-stroke Engine

Compared with four-stroke engine, two-stroke engine has advantages in power of the samedisplacement, performance of acceleration, simplicity of the structure, light weight and low cost.Compared with gasoline, kerosene has advantages in safety of transportation and usage, as well as infuel management. Knock phenomenon is an abnormal combustion in spark ignition engine. Thedetection and the analysis methods of knock were analyzed in this paper. The engine cylinder pressuresignal and body vibration signal were collected by the engine knock bench test. Engine knockcharacteristics were extracted by analyse engine cylinder pressure signal as well as the body vibrationsignal. Based on the engine knock characteristics, the engine knock on-line analysis system wasdesigned and its stability and function were verified in this paper. The main work is as follows:(1) Test methods and analytical methods of engine knock signal were researched by this paper.Three test methods of the knock signal were compared and some test methods were selected in thispaper. The feasibility of extracting knock signal characteristic frequency by FFT and power spectrumestimation was analyzed by this paper. The feasibility of extracting engine knock signal by differentdigital filtering methods was analyzed in this paper.(2) The test bench of two-stroke kerosene engine knock was built and the hardware of the testbed was selected in this paper. Engine knock signal acquisition system was designed. The engineknock bench test was completed and the engine cylinder pressure signal and body vibration signalwere collected. The engine knock conditions were determined by spectral analysis and filter analysisof engine cylinder pressure signals. The frequency of the knocking characteristics and the knockdetermination reference of the engine were extracted by the same conditions of the engine bodyvibration signals analysis.(3) Based on the knocking characteristics of the engine, LabVIEW development platform andNI-PXI were used to design the engine knock on-line analysis system, which on-line to analysiswhether the engine knock. The hardware of the system was selected in the paper. Functions of eachmodule in the software were detailed introduced and the signal generator and analog signals wereused to test the software module.(4) The function and stability of the engine knock on-line analysis system were verified by theengine half-physical simulation test, which the external excitation signal was applied to the enginebody. The system was verified by the engine bench test and the results of the test showed that the function and stability of the engine knock on-line analysis system were reached the requirements.