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| Simulation Research on Two-Stroke Braking Performance of Heavy-Duty Low Compression-Ratio Engine |
| DOI：10.13949/j.cnki.nrjgc.2023.01.006 |
| Key Words:medium and heavy truck two-stroke braking mode four-stroke compression release braking mode compression ratio altitude |
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| Abstract:The effects of different braking modes， compression ratios and altitudes on braking performance were studied by numerical simulation. The results show that the reduction of compression ratio and the increase of altitude can greatly reduce the engine braking power. Increasing the compression ratio and adopting two-stroke braking mode are effective in improving the braking power of low compression-ratio engines. Compared with four-stroke braking mode， the braking power of two-stroke braking mode with the compression ratio of 11.6 can increase by 69.6%~80.5%， the maximum cylinder pressure is lower than the limit of 6.0 MPa， and its operating speed range is not limited by the turbocharger’s danger zone. The application of four-stroke compression release braking mode on a high compression-ratio（17.0） engine has the highest braking power in the current application field. Since it is difficult to increase the compression ratio in a short term， only the application of two-stroke braking mode on a low compression-ratio（11.6） engine can still increase the braking power by 17.5%~30.4% and reduce the maximum cylinder pressure by 25.2%~29.3%. Therefore， two-stroke braking mode is recommended for medium and heavy trucks with low compression-ratio engines such as natural gas engines， which will greatly improve the vehicle braking safety. |
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