Full
Outline
The fourth stage of China’s fuel consumption limits for heavy-duty commercial vehicles has set higher requirements for the brake thermal efficiency(BTE). Based on a 7.7L diesel engine, a one-dimensional simulation was firstly conducted with experimental verification, and the mechanism of the influence of Miller-cycle coupling compression ratio on the BTE was explored through exergy analysis. The results indicate that the irreversible combustion loss and exhaust loss decrease with the increase of Miller degree. Under the equal torque conditions, an increase in the compression ratio can reduce the exhaust loss. The use of two-stage turbochargers increases the intake flow rate and total heat capacity in the cylinder, which helps to reduce the heat transfer loss and the exhaust loss. Under high combustion pressure targets, compared to the late intake valve closing strategy, the early intake valve closing scheme increases the heat transfer loss and exhaust loss. Then, an actual engine development plan was completed based on the above calculation results. Engine test was run under the speed of 1200r/min and the torque of 1200N·m. The BTE increases by 4.0% and the brake specific fuel consumption rate(BSFC) decreases by 16g/(kW·h), when the intake valve closing angle is delayed by 40°CA, the compression ratio is increased from 17.2 to 20.5 and the peak combustion pressure is increased from 16.5MPa to 25.0MPa.
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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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