One-Dimensional Thermodynamic Model Of 167FML Gasoline Engine And Its Application

This paper makes 167 FML gasoline engine as the research object. Based on relevant experimental tests the one-dimensional thermodynamics numerical simulation model was established. After model calibration, engine performance was optimized according to the development target. Meanwhile, in view of various fault modes in the process of product development, the diagnostic analysis is made by using the numerical method of cycle simulation and the corresponding improvement measures were put forward. In this paper, the specific works are as follows:Firstly, with a large number of tests, including engine bench test, air-fuel ratio test, port steady flow test, the valve lift test, motored test, air filter inlet characteristic test and the dynamic pressure measurement, etc., the building process of 167 FML gasoline engine numerical model was elaborated in detail. After model calibration, the error between simulation and experimental values were kept within 5%, so the numerical model can accurately reflect the operating characteristics of the engine with high credibility.According to the development target, the influence of intake and exhaust system structure and valve timing on engine power performance were simulated, and the optimization scheme of separately advancing intake valve closing angle 20 DegCA was proposed. It is validated by experiments that engine low speed torque is obviously improved, and the torque of 5000r/min increase about 10.63%, so the scheme ws applied in the final product design. For the problem of high thermal loads during engine optimization, two well-cooled cylinder heads were designed and engine performance was simulated, test results show that under the new cylinder head engine heat loads is greatly reduced, and the maximum engine torque increase about 5.3%. Considering the vehicle arrangement and engine performance, the paper re-matched the muffler through numerical simulation and experimental tests, which make the maximum torque increased by 6.9%.The thermodynamic numerical model was used to simulate and analyze various fault modes during the development of engine with related test. For the problem of high speed instability of the new cylinder head, the possible reasons were analyzed from two aspects: the residual gas and combustion tests. Secondly, for the instability problem of prototype without secondary gulp under idling condition, the paper established the secondary gulp thermodynamic model to compare, and analyzed the impact of secondary gulp to residual gas, then proposed improvement measures of advancing exhaust phase 10 DegCA. In addition, for the noise problem of prototype valve train, the paper put forward improvement measures of enhancing the buffer segments, then the influence of different buffer segment design schemes of intake and exhaust cam on engine performance were simulated and design suggestions were proposed.