CFD Study of Heat Transfer Reduction by Using Multiple Injectors in a DCEE Concept 2019-01-0070
Higher efficiency has for a long time been a major area of interest for the internal combustion engine research. One way to increase the efficiency is to reduce the heat transfer losses through the cylinder walls, which becomes even more significant if it is possible to utilize the exhaust heat for a compound cycle. One such cycle is called the double compression expansion engine, DCEE.
In this cycle the leftover exhaust energy can be used during the second expansion.
In this study, well validated RANS CFD simulations in the software Converge were performed on a 2.33 liter displacement Volvo D13 single cylinder engine. The focus of this study was to reduce the heat transfer losses normally occurring in a diesel engine through spray-wall impingement. A reference case with one centrally mounted injector was compared to a case with two injectors placed at the rim of the bowl. These two cases were optimized in terms of indicated efficiency and compared in terms of heat transfer losses. The placement and umbrella angle of the injectors were chosen to avoid wall impingement. To be able to compare the two cases, the amount of diesel fuel, the injection pressure, and the number of injector holes were kept the same.
The results from this study showed that the heat transfer can be reduced significantly by using multiple injectors due to a changed spray pattern. It was shown that the reduction is caused by a smaller wall area subjected to high temperature. The heat losses to the walls are estimated to be in the order of 10% reduced. Most of this is due to reduction of heat transfer to the piston.
Gustav Nyrenstedt, Tariq Alturkestani, Hong Im, Bengt Johansson
King Abdullah University of Science & Technology
International Powertrains, Fuels & Lubricants Meeting