Modeling And Validation Of HCNG Mean Value Engine Model

A series of energy and environmental problems were brought by conventional combustion-engined vehicles due to fast development of the automobile industry. With the advantage of low emissions and high efficiency, HCNG(Hydrogen enriched Compressed Natural Gas) engine is the ideal alternative to conventional internal combustion engine. Nowadays, development of ECU is mostly based on model and simulation, which is called the "V Type" method. Gas engine is different from traditional oilfueled engine. So the sophisticated mean value models developed for oilfueled engine is not fit for gas engine’s simulations. It’s of great value to develop a mean value model dedicated for HCNG engine. Aimed at the HCNG engine intake subsystem, gas fuel subsystem, power subsystem, experiment research, formulas fitting, modeling and simulation are included in this thesis..Experiment on a CNG engine was conducted. Based on the correlation between air-gas fuel mixture flowrate, manifold absolute pressure, engine speed and throttle position, three empirical formulas were proposed in this thesis. Formulas were validated by steady state experiment data. Experiment research on another HCNG engine with the hydrogen volume fraction of 0%, 20% and 55% gives the same results with the CNG engine. Based on the correlation between coefficients of the polynomial and hydrogen fraction, formulas fit for 30%HCNG engine was predicted. Calculations of predicted formulas are close to experiment data. Under the condition of same engine speed, obvious linear correlation can be found between effective torque and air-gas fuel mixture into the cylinders. Further, an linear fitting formula between Pman?ηe and Pman?n was obtained. One degree term of the formula is related to engine speed.HCNG engine’s subsystems were modeled. Then the HCNG Mean Value Engine Model was completed. The open-loop simulation results show that settling time and errors of the model is not satisfying. In order to improve the performances, PID controller was added to the model. Parameters of PID controller were optimized based on engineering tuning method. Better performances with shorter settling time and smaller errors were got in closed-loop simulation. Based on the closed-loop model, CNG, 20%HCNG and 55%HCNG engine steady state simulations at full load were finished. After that, comparison between experiment results and simulation results under 20%HCNG engine dynamic conditions was done. The HCNG mean value engine model simulation results are reasonable. It has important value of both academic and engineering.