Research On The Combustion Process Of High-speed Marine Diesel Engine

In recent years, in order to mitigate the energy crisis caused by excessive cost ofresources and ensure basic human survival environment, reducing power and energyconsumption of diesel engines is imperative and all countries have developed increasinglystringent emission regulations. Thus, improve diesel engine power, economy and reduce itsemissions is the only way to meet the more stringent modified emission regulations. Thecombustion process of diesel engine is the most fundamental factor to determine thecombustion and emissions performance. In this paper, the diesel combustion process wassimulated. On this foundation, some structural parameters as well as the combustion chamberstructure were optimized, on the purpose of improving diesel power, reducing fuelconsumption and reducing emission pollutions.The paper simulated the combustion process of a certain type of high-speed marinediesel engine using the AVL FIRE software. In order to obtain more accurate initial cylinderstatus parameter, the working process of diesel engine was simulated in the AVL BOOSTsoftware. Since there is no measured injection curve, the accurate fuel injection curve isobtained by the simulation model of fuel injection system in the AVL HTDSYM software.After the completion of parameter settings, the diesel combustion process is calculated andthe simulation model is validated using experimental data.Calculations of the diesel combustion process under different intake valve closing anglesshow that the indicated power increases first and then decreases when the intake valve closingangle increases from20°CA to40°CA. But the effective fuel consumption rate has anopposite trend. At the closing angle of30°CA, the indicated power is maximum and theefficient fuel consumption rate is minimum, while NO mass fraction is also a minimum value.The SOOT mass fraction is increasing with the increase of the closing angle. Taking the dieselengine power, economy and emission characteristics into consideration, the recommendedvalue of the intake valve closing angle is30°CA.The diesel combustion process under different injection advance angles is calculated.The results show that as the angle increases from14°CA to22°CA, the indicated powerincreases and the effective fuel consumption rate decreases, while the NO mass fraction risesand the SOOT mass fraction has an opposite trend. So the appropriate adjustments can be made depending on the different requirements.Three different combustion chamber structures are designed and calculated. The resultsshow that the first scheme gets better power and economy with higher NO emission; the lastscheme has better power and lowest NO emission but higher fuel consumption. The fuelconsumption of second scheme is lower, but power is also lower.