Research On Emission Performance In Lpg Bus Engine Based On Modern Emission Regulations

Under the conditions of the global economic cycle, car ownership continued to increase in China, Meanwhile, the emerging energy and environmental issues made LPGV(Liquefied Petroleum Gas Vehicle) use more and more. Currently, some domestic cities buses also use liquefied petroleum gas fuel, an example of Guangzhou bus,but buses with LPG also face the emission problems which EuroIIIstandard LPG engines actually can't reach Euro II emission standards. According to the existing application status in LPG, the paper starts from the formation mechanism of emissions in YC6112LPG engine, analyzing the impact of purified factors on engine emissions and emission characteristics, studying on emission control methods in LPG engine based on modern emission regulations, in order to solve the problem that CO,HC and NOx have low conversion rates under the city bus cycle conditions, then, make an emission test in single-point LPG engine, indirectly study that LPG engine using multi-point injection control also make a influence in engine emissions, that will meet modern emission regulations.Firstly, the paper starts from the formation mechanism of emissions in YC6112LPG engine, analyzing the formative processes of CO, HC and NOx. Starting from the combustion mechanism, establish the combustion and chemical reaction model, gain the relationship between the reaction rate, temperature, air-fuel ratio and emissions. on this basis, establish an engine emission simulation model based on YC6112 LPG engine, including turbo model, throttle body model, intake and exhaust system model, fuel nozzle model, engine cylinder model, intake and exhaust valve model and other parts, then, make an analysis between simulation and experimental data under the external characteristic conditions.Secondly, study on the impact of purified factors on engine emission which is based on LPG bus engine emission simulation model established. The factors in engine include mainly intake-air composition, intake-air non-uniformity and air-fuel ratio, while the factor out engine is mainly three way catalyst converter. Meanwhile, Research on emission performance when LPG bus engine is used respectively under the stable and instantaneous conditions, whereby, the instantaneous conditions include mainly start, acceleration and deceleration, then study on emission performance of LPG engine based on the city bus driving cycle.Thirdly, LPG bus YC6112 engine is the object studied, the gas composition is LPG(70% propane and 30% butane), using the multi-point injection and real-time changes in fuel injection pulse width in order to realize an air-fuel ratio MAP open-loop PID closed-loop composite control, MAP control method is mainly according to speed and load to determine fuel injection quantity, MAP closed-loop control method is through the error between the oxygen sensor feedback value and theoretical value to compensate for injection pulse width, then, realizing the multi-point injection air-fuel ratio control based on modern emission regulations, making the excess air ratio in the vicinity of theoretical value. Meanwhile, theλand emissions in simulation make a contrast between single-point injection control engine and multi-point injection control engine, make an emission test for the multi-point injection LPG bus engine under the city bus driving cycle.Finally, make an emission test on LPG engine and bus, then, comparing and analyzing GT-POWER simulation results and experimental data.