船用柴油机实现低NOx燃烧的数值模拟

Numerical simulation of low-NO_x combustion in marine diesel engine

为研究"浅坑型"燃烧室缸内高温燃油的雾化与燃烧过程,建立了L23/30H柴油机的CFD计算模型,应用台架试验验证了计算模型的有效性,在提高燃油喷射温度的条件下模拟了缸内平均压力和温度的变化,对比分析了排放物的生成情况.结果表明:燃油喷射温度对L23/30H柴油机的动力性能影响不大,对NO_x生成有显著影响,燃油喷射温度上升至413 K时,NO_x生成速率减小,NO_x最终生成量有量级上的减小,能满足MARPOL公约73/78附则Ⅵ修正案的排放规定,燃油喷射温度继续升高,NO_x生成量变化甚微;燃油喷射温度的升高使得扩散燃烧过程中Soot的再氧化效应减小,最终Soot生成量有所升高.

To investigate the spray and combustion processes of the L23/30H diesel with shallow-pit combustion chamber, the computational model was established based on AVL-FIRE and validated by the on- line bench experiment. The inner cylinder pressure, temperature and emissions under the condition of high-temperature fuel injection were numerically simulated. The results show that high-temperature fuel injection can markedly reduce the NOx emission under the substantially unchanged circumstance of the output power. The NOx emission can meet the supplementary provisions VI amendment of MARPOL 73/78 when the fuel injection temperature is heated more than 413 K. The NOx emission shows the tiny variation with the increased fuel injection temperature, while the Soot emission increases with the reduced re-oxidation in the diffusion combustion.