The Research On The Application Of Fault Diagnosis Of Diesel Engine Using Instantaneous Speed And Torsional Vibration Signals

Condition monitoring and fault diagnosing for internal combustion engines is very important, so far as to improve the safety and the reliability of powertrain system, and to meet the need of modern predictive maintenance and automotive powertrain systems is concerned. However, it is difficult to monitor condition and to diagnose faults due to engine's complicated structure and working process. On the basis of such background, this dissertation intends to study the applications of the engine monitoring and diagnosing using instantaneous speed and torsional vibration signals, and to develop an monitoring system using torsional vibration of shafting for diesel engine. The main contents of the paper are as follows:1. The elements of measuring instantaneous speed are studied, several methods of measuing instantaneous speed are introduced, the primary factors to affect the measurement precision of the instantaneous speed, such as the gear precision, sample frequency etc., are analyzed, and in order to enhance the measurement precision, the instantaneous speed signals are processed and analyzed by the gear averaging, wave filtering, and whole cycle averaging methods.2. The elements of measuring torsional vibration, several methods of measuring torsional vibration are introduced, the primary factors to affect the measurement precision of torsional vibration, such as transverse vibration, precision of transducer etc., are analyzed, and in order to enhance the measurement precision, the method of fixing double-transducer and photoelectric encoder is indicated.3. A simplified model of diesel engine instantaneous speed has been developed based on the investigation of dynamic property of diesel engine, and the calculating software is developed with the language of LabVIEW, the impact that the instantaneous speed is fallen under the propeller is assayed, and three feature parameters, which can be used to detect diesel engine's faults and to locate fault cylinders, have been proposed, based on the simulation and signal analyses of the diesel instantaneous speed.4. The theory diagnosing the fault of diesel engine with torsional vibration signals is analyzed, and it is showed via the experiment: when the fuel in one cylinder is leaked, the amplitudes of low syntonies will increase evidently. And the system of testing torsional vibration is described with the language of Lab VIEW, after a brief introduction of the structure and functions of this system, the design of the hardware and software is explored in detail.A lot of experimental researches in real-world engines are accomplished, and the experimental results verify the above theoretical developments.