Research On Knock Recognition System Of Two Stroke Ignition Heavy Oil Engine

Due to the mechanical structure is simple, high efficiency, light weight, high power, etc, spark ignition piston engine, especially the two stroke engine have a widely range of applications in the military special vehicles and aviation, small unmanned helicopter and other fields. Compared with gasoline, kerosene has advantages in safety of transportation and usage, as well as in difficultly of evaporation and high flash point; but the flame propagation speed is low, and poor antiknock, the knock was a kind of abnormal combustion phenomenon in the spark ignition engine, which can affect the power output, fuel consumption, and even damage to the important parts of the engine. Therefore, designed a two- stroke kerosene engine knock identification system, and set up the experimental platform of a certain type of two- stroke engine. In this paper, the method of collecting and analyzing the vibration signals of the body is described in detail, and the vibration signal of the engine was analyzed and processed, and accurately extracted the frequency of the signal and other information, designed the two stroke kerosene engine knock identification system, and set up the function of the semi physical simulation test bench and verified its function. And the experiments have been carried out in the test bench, the results show that its function and stability reached the expected requirements. The main work as follows:(1) Studied on the method of acquisition and analysis of engine knock, compared three kinds of main knock signal detection and processing method. In this paper, adopted the body vibration signal processing method as the research methods, and analyzed the advantages and disadvantages and feasibility of the fast Fourier transform algorithm and intrinsic mode feature energy method, This paper selected the method of mode feature energy method as knock signal feature extraction method;(2) In this paper, the hardware of the knock detection system is selected, and the design of hardware system is completed. According to the logic of the body vibration signal processing and knock, knock intensity recognition, the software design of knock recognition system was carried out, and completed the compiling and debugging of the system; the communication protocol of the upper and lower computer is defined, and the design of the host computer system is completed, achieved real time feedback engine's state information, knock status and knock intensity, and achieved beautiful and practical effect.(3) Set up the semi physical simulation test bench, and carried out the functional verification of the knock recognition system, using the vibration signal of the real experiment bench collected as input signal, by changing the frequency and amplitude of the input signal to verify the function of the knock detection system.(4) Set up the experimental platform of the two stroke kerosene engine, and the experimental study of knock identification system was carried out, to test its function is normal. Through the experimental verification, the results show that the two stroke kerosene engine knock identification system can accurately determine the engine knock status and timely feedback knock strength.