Jiangping Tian

Development of an Improved Multi-Component Vaporization Model for Application in Oxygen-Enriched and EGR Conditions

An improved multi-component vaporization model was developed and applied to predict the vaporization characteristics of a fuel droplet under oxygen-enriched and exhaust gas recirculation (EGR) conditions in this study. The model was constructed including an improved enthalpy diffusion sub-model, a corrected Stefan flow velocity, and temporal variation of thermal physical properties. The computational results were validated with the experimental data and satisfactory agreements between the predictions and measurements can be achieved. The effects of O2, CO2 concentration, and EGR on the vaporization rate of fuel droplet in various ambient temperature and pressure conditions were investigated.

The influence of the enrichment injection angle on the performance of a pre-chamber spark ignition natural-gas engine

Using an enriched pre-chamber is an effective way to extend the lean limit, to reduce the nitrogen oxide emissions and to avoid abnormal combustion in spark ignition natural-gas engines. Enrichment injection in the pre-chamber of a spark ignition natural-gas engine determines the flow field and the fuel–air mixture formation quality in the pre-chamber and has a profound influence on the combustion performance of the engine. In order to study the characteristics of enrichment injection in the pre-chamber of a natural-gas engine, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics calculations were carried out. The influence of the enrichment injection angle on the engine performance was investigated with the aid of a computational fluid dynamics simulation tool. The results indicate that a change in the enrichment injection angle directly affects the gas motion, the fuel–air mixture formation, the flame propagation and the formation of nitrogen oxides in the pre-chamber and further influences the penetration of the flame jets, the combustion temperature distribution and the formation of nitrogen oxides in the main chamber. There is an optimal injection angle for this research engine. Of the four injection angles that were investigated, an injection angle of 14° results in the lowest nitrogen oxide emissions.

Investigation on the development and the controllability of a compact multi-functional, fully variable-valve-actuation system

A compact multi-functional, fully variable valve actuation system for six-cylinder engines was proposed. The system can run in both the drive mode and the brake mode of internal-combustion engines. With the help of a distributor, fully variable valve events were achieved with two oil-supply sets, two solenoid valves and one drain valve. The operational parameters of the valve can be adjusted independently for individual cylinders. A numerical study on the controllability of the system was carried out with AVL Hydsim. The calculation results revealed that the timing of the valve opening, the maximum lift, the duration and the time–area value can be adjusted independently or synchronously by controlling the solenoid valves and/or the drain valve. Further correlation analysis results revealed that all the operational parameters of the valve had approximately linear relationships with the corresponding control parameters, and all the correlation coefficients were larger than 0.95, indicating good controllability of the system.