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Outline
A three-dimensional numerical model for a direct injection hydrogen engine was initially constructed. Subsequently, simulations were conducted to investigate the impact of orifice quantity, installation position, and piston top shape on combustion performance. The results show that the performance of side injector position is better than that of center injector position, and the maximum indicated thermal efficiency is 47.28%. Based on the side injector position, the influence of piston top shape on combustion performance is further studied, and it is found that the shape of piston top shape has a significant impact on the development and distribution of mixture in the cylinder. The mixture concentration distribution formed by the combination of slope head piston and 1-hole nozzle will extend the ignition delay and combustion duration, but it will reduce wall heat transfer loss, increase work capacity, and make the indicating thermal efficiency higher than that of the flat top piston. To further verify the advantages of the slope head piston, the performance under different equivalence ratios was simulated. The result indicates that the maximum indicated thermal efficiency of the slope piston top increases by 0.29%, 0.67% and 0.52% respectively, under the equivalence ratios of 0.3, 0.5 and 0.7.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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