Numerical Simulation About Hydrocarbon Emission Of Gasoline Engine In Cold Starting Condition

In cold start condition of the gasoline engine, the concentration of mixture gas in the chamber is so rare that it is hard to be ignited, because of the low temperature of inlets and combustion chamber, the fuel injected evaporates very slowly, and many of the drops adsorb onto the wall. So the amount of the fuel injection should be increased in order to reach a high concentration of mixture gas. Otherwise too much residual exhaust gas, combustion instability, combustion incompletion and thick rapidly quenched layer make lots of unburned hydrocarbon (HC) left in the cylinder. The ternary catalytic converter does not reach its most effective working temperature in the cold start process, so it can't be catalyzed. Large amounts of residual HC are emitted directly into the atmosphere, of course, it will cause severe pollution. According to a testing method named FTP invented by USA, the amount of emission of HC in the period of cold start is 60%-80% of the whole testing process. We can deduce that there is a great significance in controlling the emission of HC in the period of cold start.Gasoline is a mixture with multiple components, which is no fix ratio about the component. So it is hard to recognize the formation mechanism of HC and also difficult to analyze through chemical reaction equations. The author uses isooctane instead of gasoline and constructs a new framework mechanism of isooctane oxidation reaction, which is added to the overall reaction of KIVA-3V in order to study the generation and transformation of HC in the cold start condition. Otherwise, the O'Rourke model about spray drop collision used by KIVA-3V is not fit for the cold start condition of the gasoline engine. The author use the collision theory proposed by Nordin, create a new spray drop collision model, inset into the KIVA-3V code,and debug it very successfully.After the completion of the task about chemical reaction principle and model standardization and improvement, takes the temperature and pressure and rotate speed so on, which are measured from different cold start experiment stages as the primary condition, and simulates the HC generation in the different cold start stages, study the effect factor of HC generation in cold start condition of the gasoline engine about ignition advance angle, inlet temperature, ignition energy, air movement, supercharge ratio, and so on, provides consultation about the reducing of HC generation in cold start condition of the gasoline engine.