Simulation Research On Combustion And Emission Of Dual-Spark Plug Ignition Direct Injection Methanol Engine

On the background of energy crisis and environmental pollution problems have becoming a dominant problem, looking for a new alternative energy fuel which adapt to China’s energy structure has been an urgent thing. Methanol as a most promising alternative fuel, it not only has a very distinct superiority in natural gas storage and transportation but also has more desirable combustion and emission performance compared with gasoline and diesel. However, methanol engines have high unregulated emissions and difficulties in cold start. In this paper the dual-spark plug ignition methanol engine model is established and a direct injection spark ignition gasoline as the prototype. Through research of dual-saprk ignition structure is conducted on the combustion and emission process under the cold start and steady conditions, which can provide a new idea to improve combustion and emissions performance of methanol engine.First, the combustion model is corrected by experimental data.Secondly, it is discussed that the influence of combustion and emission under the cold start and steady conditions when change the spark plug location, ignition timing,injection timing and equivalence ratio.The results obtained: With the rise of the distance between dual-spark plug, the max value of cylinder pressure and cylinder temperature decrease gradually, the peak value of heat release rate show a trend of decrease after an initial increase and its angle postpone gradually, the unburned methanol emission increases gradually. The flame propagation velocity goes up gradually. If the distance of dual-spark plugs is too long, the SOOT emissions will increase, If the distance of dual-spark plugs is too short, the NO_X emissions will increase.In the cold start conditions, with retarding of the injection timing, the peak value of cylinder pressure, cylinder temperature and heat release rate increase gradually and reach their maximum value in the 70°CA BTDC, the peak value will decrease when retard the injection timing again.Their peak corresponding angle is becoming more and more in advance. The flame development period and unburned methanol emission decrease slowly, when the injection timing is 70°CA BTDC reach their minimum value, their both value will go up when retard the injection timing again. With the delay of injection timing, the NO_X emissions go up gradually and reach their maximum value in the 70°CA BTDC. The SOOT emission decreases with the advance of the injection timing and reach their minimum value in the 70°CA BTDC, when delay the injection timing again, the SOOT emission value began to rise. In the cold start conditions, with the ignition timing advance, the peak value of cylinder pressure, cylinder temperature and heat release rate increase gradually, their peak corresponding angle gradually advance. The impact on the flame development period is not significant. The unburned methanol emission decrease gradually with the advance of ignition timing. The NO_X emissions increase gradually with advance of the ignition timing, however the SOOT emission have the opposite trend. Considering the combustion and emission factors, the optimum ignition advance Angle is 21°CA BTDC. In the cold start conditions and dual-spark plug ignition mode, with the increase of equivalence ratio, the peak value of cylinder pressure, cylinder temperature and heat release rate increase gradually. Compared with single spark plug system, dual-spark plug ignition improve engine performance of methanol and flame propagation rate, reducing the combustion duration, methanol engine enables rapid combustion. In the single spark plug ignition mode, the peak value of cylinder pressure, cylinder temperature and heat release rate less than lean combustion state of dual-spark plug ignition mode when the equivalence ratio is 0,9. In addition, dual spark plug ignition also reduce unburned methanol quality. In the steady conditions, with the advance of injection timing, the peak value of cylinder pressure, cylinder temperature and heat release rate is higher and higher. The flame development period, the unburned methanol emission and the SOOT emissions decreases gradually as the injection timing advance. The NO_X emissions gradually increase as injection timing advance.When the injection timing is 110°CA BTDC, the density near the dual-spark plug can form good concentration gradient. In the steady conditions, with the advance of ignition timing, the peak value of cylinder pressure and cylinder temperature increase gradually. The flame development period increases gradually as the ignition timing advanced. The unburned methanol emission decrease gradually with the advance of ignition timing. The NO_X emissions increase gradually with advance of the ignition timing, however the SOOT emission have the opposite trend.