An Experimental Study On The Influence Of Technology State Detection Of Valve Mechanism And Changes Of Diagnosis Parameters On Performance Of Engine

This thesis firstly states simply the build-up of valve mechanism, valve clearance and valve timing. Then, it is analysed systematically that the technology state of each assemblage of valve mechanism, which includes valve group and valve transmission group. Therefore, the diagnosis parameters of technology state of valve mechanism, which are valve timing and valve clearance are determined. Furthermore, this thesis also states the checking and adjusting method of valve timing and valve clearance. Next, the experiment iscarried out on N485Q DI diesel engine as an example. First of all, the performance parameters are measured under normal technology state of diesel engine. Then, the four keys of displacement are assembled in diesel engine in order to change the valve timing. The performance parameters are measured ahead or behind valve timing of 20,4?6?80 of diesel engine .And contrasted with the performance parameters under normal technology state, these parameters can give us the influence laws of power, economic performance and smoke emission of diesel engine ahead or behind valve timing. And then following this using orthogonal regression rotation design method, the experiment of five adjusting parameters (valve timing, admission valve clearance, emission valve clearance, rotation speed, load rate)is designed. The influence laws of power, oil consumption rate and smoke emission are researched under the circumstances of these five adjusting parameters' (valve timing, admission valve clearance, emission valve clearance, rotation speed, load rate) mutual matching. Thus mathematical models including power, oil consumption rate and smoke emission concerning five adjusting parameters have been established with statistical software SPSS, the effects on power, economic performance and smoke emission are descripted batchingly of the five adjusting parameters. Finally, with computer looking for the best parameters, the six regression equations at maximum torque and at maximum power are optimized. The best values of each performance index in theory and the corresponding values of adjusting parameters are concluded. Based on these parameters, the engine is adjusted again, and each practical performance index is measured by experiment, and contrasted with the theoretical values. Finally, the best adjusting parameters of valve timing, admission valve clearance and emission valve clearance have been determined by theoretical and experimental method.The research result shows that the increases of admission and emission ahead angles to the running of diesel engine when valve timing advances is beneficial to the high speed running of diesel engine ,the decreases of admission and emission behind angles to the running of diesel engine when valve timing advances is beneficial to the low speed running of diesel engine ;and when valve timing falls behind, the decreases of admission andemission ahead angles to the running of diesel engine is beneficial to the middle speed running of diesel engine, the increases of admission and emission behind angles to the running of diesel engine is no benefit to the low speed running of diesel engine. The effects of five adjusting parameters of valve timing, admission valve clearance, emission valve clearance, rotational speed ,load rate are interacted. In the course of using internal combustion engine, because of the wear of some parts and loose of fasteners of valve mechanism, the best adjustment of each parameter should change and shouldn't be adjusted invariably according to factory-produced value. The experimental result is satisfactory as the errors of the outcomes found out by computer for the best value and the experiment outcomes are within 2 percent.