• Energy Research

Abstract This research aims to numerically investigate the combined effect of ignition position and injection method on the gasoline rotary engine. The three-dimensional dynamic model was established by CONVERGE software and validated by the experimental data. The results indicate that compared with port injection, the direct injection leads to obvious fuel stratification in the combustion chamber, and the local equivalence ratios around the two spark plugs are different. The index of in-cylinder fuel inhomogeneity corresponding to direct injection decreases linearly with the progress of the mixing process. Adopting the double spark plug can obtain a higher release heat rate and combustion efficiency than adopting the single spark plug ignition. Higher in-cylinder peak pressure and indicated thermal efficiency also can be obtained by using double spark plugs ignition. Only using leading spark plug ignition would cause a large in-cylinder unburned area, resulting in poor power performance of the rotary engine. In particular, the direct injection can obtain higher mean in-cylinder pressure than the port injection, but the indicated thermal efficiency of port injection is higher than that of direct injection. In the aspect of emissions, double spark plugs ignition would lead to higher in-cylinder temperature and NOx content than other ignition modes, but double spark plugs ignition can alleviate incomplete combustion and reduce HC emission. Under the same ignition strategy, the port injection can effectively reduce CO emission than direct injection.

Abstract This research aims to numerically investigate the combined effect of ignition position and injection method on the gasoline rotary engine. The three-dimensional dynamic model was established by CONVERGE software and validated by the experimental data. The results indicate that compared with port injection, the direct injection leads to obvious fuel stratification in the combustion chamber, and the local equivalence ratios around the two spark plugs are different. The index of in-cylinder fuel inhomogeneity corresponding to direct injection decreases linearly with the progress of the mixing process. Adopting the double spark plug can obtain a higher release heat rate and combustion efficiency than adopting the single spark plug ignition. Higher in-cylinder peak pressure and indicated thermal efficiency also can be obtained by using double spark plugs ignition. Only using leading spark plug ignition would cause a large in-cylinder unburned area, resulting in poor power performance of the rotary engine. In particular, the direct injection can obtain higher mean in-cylinder pressure than the port injection, but the indicated thermal efficiency of port injection is higher than that of direct injection. In the aspect of emissions, double spark plugs ignition would lead to higher in-cylinder temperature and NOx content than other ignition modes, but double spark plugs ignition can alleviate incomplete combustion and reduce HC emission. Under the same ignition strategy, the port injection can effectively reduce CO emission than direct injection.

Abstract Hydrogen two-stage direct-injection enrichment is a novel injection strategy to utilize hydrogen more efficiently and effectively in gasoline rotary engines by inheriting the merits of hydrogen and direct injection simultaneously, such as flexible control, efficiency improvement, and emissions reduction. Based on the CONVERGE code with detailed chemistry solvers, a full-cycle CFD modeling including hydrogen jet-flow and combustion processes was presented and validated by experimental data. To understand the role of hydrogen two-stage injection in improving engine performance at part-load and lean-burn regime, six different injection arrangements for which two-stage injection strategies with variable hydrogen amount for each pulse (up to 30% for post-injection) had considered. The different effects on species evolution, combustion characteristics, knock propensity, and emissions formation were analyzed step-by-step. The simulation results showed that compared with direct-injected hydrogen for single-pulse, injecting adequate hydrogen in the second pulse after spark-ignition onwards performed a significant beneficial effect on the mixture stratification and flame propagation, especially for the trailing part of the rotor chamber, which contributed to the improvement in both combustion characteristics and thermal efficiency. The assessment of knock propensity demonstrated that the two-stage direct-injected hydrogen had the potential of mitigating the knock under lean operations. Using split injection accompanied by an optimized hydrogen allocation strategy allowed substantial unburned hydrocarbon and carbon monoxide reductions with a slight nitrogen oxide penalty rate due to the elevated combustion temperature.

Abstract Hydrogen two-stage direct-injection enrichment is a novel injection strategy to utilize hydrogen more efficiently and effectively in gasoline rotary engines by inheriting the merits of hydrogen and direct injection simultaneously, such as flexible control, efficiency improvement, and emissions reduction. Based on the CONVERGE code with detailed chemistry solvers, a full-cycle CFD modeling including hydrogen jet-flow and combustion processes was presented and validated by experimental data. To understand the role of hydrogen two-stage injection in improving engine performance at part-load and lean-burn regime, six different injection arrangements for which two-stage injection strategies with variable hydrogen amount for each pulse (up to 30% for post-injection) had considered. The different effects on species evolution, combustion characteristics, knock propensity, and emissions formation were analyzed step-by-step. The simulation results showed that compared with direct-injected hydrogen for single-pulse, injecting adequate hydrogen in the second pulse after spark-ignition onwards performed a significant beneficial effect on the mixture stratification and flame propagation, especially for the trailing part of the rotor chamber, which contributed to the improvement in both combustion characteristics and thermal efficiency. The assessment of knock propensity demonstrated that the two-stage direct-injected hydrogen had the potential of mitigating the knock under lean operations. Using split injection accompanied by an optimized hydrogen allocation strategy allowed substantial unburned hydrocarbon and carbon monoxide reductions with a slight nitrogen oxide penalty rate due to the elevated combustion temperature.