An Investigation On Rapid Lean-Buring And Emission Control Of Spark Ignition LPG Engines

With human being getting increasingly consciousness of environment problem, the research of internal combustion engine is focusing on environmental benefits such as fuel consumption, emissions, noise and so on. LPG as a new alternative fuel with high octane is being used broadly. Today, the key issue is enhancing flame propagation, combustion velocity, mixture flowing in cylinder and improvement and controlling enhanced ignition process for high heat efficiency and low emissions. This dissertation presents a novel solution of rapid lean-burning in a high-speed LPG engine with EFI for steady operation. The details as follows:1. A sole-fuel gaseous LPG PFI system has been developed with a thermoregulation reducer as a constant low pressure LPG resource for controlling A/F ratio precisely within required mixture concentration on a test bench in different operation conditions.2. Multi-channel transient SI engine combustion analyzer has been developed. Pressure inside cylinder,λand exhaust emissions can be measured by this analyzer. The d p/dφ, heat release ratio, MFB and thermal circulation changes are calculated through the numerical analysis.3. An electronic control rapid burning system with high-energy, duel-spark plug ignition system is developed creatively, including modified cylinder head(compression ratio, spark plug location and organization of flow motion inside cylinder), two independently adjustable high-energy-ignition system. Synchronizing and asynchronous ignition timing can be realized by ECU and control strategy according to engine operation condition. Flame core propagation is improved by enhanced ignition energy intensity in this system. To cooperate with combustion chamber and spark location, the flame propagation distance is shortened for rapid burning.4. The LPG rapid lean-burning research is carried out by using the developed system. Reasonable organization of swirl and tumble flow movement in cylinder associating with spark plug location improve flame velocity ,extend limitation of lean burn and reduce the emissions in the mean time control knock. The LPG engine with EFI performance is investigated in diverse compression rate, ignition mode, ignition energy and flow movement. EGR system of LPG engine is developed. Rapid lean-burning characteristic and emission performance is investigated in condition of EGR. The research results show that in the mode of high-energy synchronizing and asynchronous ignition, the flammability limit of LPG mixture is extended significantly comparing with normal single spark ignition mode in whole range of EGR.5. Based on above research, it can conclude that the exhaust emissions such as CO, HC and NOx can be controlled by LPG rapid lean-burning associating with EGR for NOx emission control...