Instrument Design And Development For Testing Coking Tendency Of Lubricating Oil

The engine bench test is an important experiment used for the evaluation of key quality indicators of engine oil.The lubricating oil coking tendency tester(LOCTT)is developed for the simulation of engine bench test and evaluation of engine oil’s properties,such as antioxidation and cleanliness.The slow control system response and the individual evaluation difference of the paint film are two main problems of the mainstream instruments.This thesis is mainly dedicated to the design of LOCTT with improved performance,including a splash stick speed regulating system,two temperature control systems used for the adjustment of aluminum plate temperature and oil temperature and a specified oil performance evaluation system.Accordingly,some experiment studies are conducted.The related work and conclusions are as follows:Firstly,a literature review on the state of the art technology of LOCTT is presented.The principles of LOCCT are clarified by a comparison study with the engine bench test,and in the meanwhile define its evaluation criteria.Some strategies for the optimization and upgrade of LOCCT are presented by considering the structure and operation procedure of a commercial prototype as example.Secondly,the software and hardware design and implementation of the speed regulating system and the two temperature control systems are introduced.The two temperature PID controllers are tuned by classical relay feedback tuning method and modified relay feedback tuning method.The experimental results show that the rapidity and stability performance of speed regulating system and the two temperature control systems are considerably improved compared with the commercial products.Thirdly,through the HSV color space feature vector joint distribution histogram,the cause of individual evaluation difference of the paint film is discussed.A new method to quantify the paint film rating based on gray histogram is put forward and the specific grading of different grades of the paint film is given,which improves the accuracy of paint film evaluation.Finally,based on 3 lubricating oil samples with bench test data,optimum test conditions are determined by comparing the consistency of the difference between the top ring groove filling carbon rate(TRGFCR)and the amount of cokes under different conditions,i.e.,different aluminum plate temperatures,different splashing oil ways and different test time.Using 17 CCgrade oil samples and 23 CD-grade oil samples as test samples,and according to the one-toone mapping between the TRGFCR and the amount of different oil samples cokes,the correlation between the self-made tester coke amounts and the TRGFCR of the Caterpillar 1-H2 and 1-G2 engine bench test are established through the four-quadrant analysis,which lays a good foundation for the further development and application of the instrument.