Diesel Premixed Methanol Combustion Test And Theoretical Simulation

This paper introduced a new partial premixed compound combustion mode engine in which some methanol was premixed in the introduction charge of the diesel. In such combustion mode^ the premixed combustion part was increased, the diffusion, ambient was changed from air to methanol/air mixture for decreasing soot emission of the engine. The results of the experiments show that the soot emission decreased greatly and the NOX emission was improved, while CO and HC emission increased but still lowered than gasoline engine, the power output and torque of the engine have not been influenced and the specific energy consumption was improved. A numerical model based on the chemical equilibrium equations was established to predict the concentrations of combustion products. The software MATLAB was used to solve the equations. The results of calculation were compared with the experimental data.In the experiment the methanol was injected into the induction manifold of the diesel engine and evaporated to form methanol/air mixture with the induction air. The methanol quantity was controlled by an electronic control system. The control system was consisted by a PC and an AT89C51 single chip. The commands are input through PC keyboard, and the communication between the PC and the single chip is realized by the RS-232 protocol through serial port. The AT89C51 executes the correspond command to open the injector and control the opening duration according to the command received from the PC and thus controls the methanol injecting and the quantity injected.The comparison of the results of the experiment and calculation of the model shows that the model prediction is agree with the experiment results in quality but not in quantity. That is mean the model has the ability to predict the emission of such engine in quality but lack the accuracy to predict the emissions. The reason of this may be as follows, firstly, the model has not including some important physical process such as gap effect, wall quenching extinction effect, which may greatly influence the emissions; secondly, the emissions formation in the cylinder are not all of equilibrium process but the process controlled by the chemical kinetics. That means, a model which not only includes the important physical process, but also based on the chemical kinetics should be established for predicting the emissions of such engine.