Research of vibroacoustic method of technical condition control of diesel engine of combine harvesters for detection of defects appearance

Abstract

The authors research the vibroacoustic method of technical condition monitoring the diesel engine of combine harvesters as result of analysis of propagating elastic vibrations through the block and details interaction. Therefore, the authors solved the problem of this method – the detection of vibrating acoustic signal caused by interaction of details of studied kinematic pair. The decision took into account that increase in number of cylinders of engine leads to increase in density of vibration pulses per phase space unit, so cycle of operation of combine harvesters’ diesel engine was estimated by angle of rotation of crankshaft. Therefore, it is established that only phase space of gas distribution mechanism is filled with vibration pulses, that it is impossible to determine the technical state of the i-th connection of this mechanism by one parameter. To improve the accuracy of diagnosis, the authors considered the nature of oscillations in combine harvester engine. Engine work is characterized by the fact that workflows in different sections pass at different periods of time, so they use temporary selection to distinguish the vibrational process associated with work of single section or single element of one section. The impact of fluctuation of engine is impulsive, caused by high rate of increased pressure in combustion chamber, by transfer of pistons and processes of fuel injection. Therefore, changes in moment of fuel injection, malfunction of gas distribution mechanism, wearing of piston rings and increasing in gap between piston and sleeve are related to operation of these mechanisms, so the pulses shift in phase, their amplitude and duration change and new pulses appear. At the same time there are several factors that cause some kind of complication of vibroacoustic signal. For engines with more than 5 cylinders, signal timing (overlapping) and imbalance of parts during rotation causes appearance of 606.5 Hz frequency spectrum.