Study On Optimization Of Ignition Timing For Variable Stroke Engine Power Mode

The variable stroke engine, which has the characteristic of higher power per liter and quality power ratio, also with variable load rate and lightweight, combines two-stroke mode and four-stroke mode together as well as good fuel economy of four-stroke mode and strong power of two-stroke mode which makes full use of the advantages of the two kinds of engine. Taking ignition timing as the breakthrough point, the paper integrates bench test, integrated simulating, and optimization aims at improving two-stroke mode power performance.The two-stroke mode adopted the appropriate combustion heat model and heat transfer model based on the retrofitted variable stroke engine by refrigerant cylinder gasoline engine combustion theory and the cylinder combustion conditions. Furthermore, according to the thermodynamic theory, the refrigerant replacement of two stroke model has been probed; the reflux scavenging and homogeneous mixing model were used, which are more suitable for two stroke mode operation.Based on the bench test, engine performance, the cylinder pressure curves and the bench structure have achieved to verify the simulation model in the BOOST. Under different conditions, the vehicle power performance and economical performance has been analyzed.Through setting theory and structural data of different components, the numerical simulation model of two-stroke engine in the BOOST was established by theoretical and experimental engine thermodynamics and verified by the cylinder pressure and power curves. Moreover, two-stroke mode initial injection MAP were calculated in the numerical simulation model as well as the influence of different ignition timing to engine power performance.By applying Multi-island genetic algorithm and NLPQL, the paper integrated i SIGHT and AVL BOOST with the goal of maximum engine power, which taking ignition timing as design parameters, also taking IMEP, peak firing pressure, and peak firing pressure crank angle as constraint conditions. Simultaneously, optimal ignition timing is achieved and reaches the goal.