ESTIMATION OF THE INFLUENCE OF DIESEL ENGINE VALVE CLEARANCE ON INTAKE MANIFOLD PRESSURE PULSATIONS

The paper considers the influence of the out-of-adjustment degree of a D-240 diesel engine valve clearance on angular acceleration at the crankshaft speedup, fuel consumption and a type of absolute pressure waveform in the intake manifold. The laboratory bench includes: a D-240 diesel engine of an MTZ-82 tractor, a MotoDoc III engine tester with a low air pressure sensor and a fuel pipe pulse detector, a digital engine power indicator IMD-C, and digital fuel flow meter DFM-100. The nominal valve clearance of 0.25 mm was set for all valves. The experiment involved three phases (without valve clearance control, with nominal valve clearance values and with valve clearance values much higher than nominal) and two variants: with a mounted and dismantled air filter. The nominal valve clearance values give better acceleration and fuel consumption, which can be caused by both better air supply and the device inaccuracy. The waveforms obtained differ insignificantly, which can be attributed to their low practical utility for diagnosing the out-of-adjustment condition of valve clearances. However, the wider valve clearances cause an iterative echo vibration impulse, which is definitely related to impact processes in the valve mechanism. It has been experimentally proved that a method of analyzing vibro-acoustic waveforms of a running engine is more informative for detecting the considered defect.