The potential of increased efficiency and power for a turbocharged PFI-SI engine through variable valve actuation and DEP

Abstract: New legislation involving emissions from internal combustion engines are pushing the manu-facturers to develop new technology faster than ever before with the amount of greenhouse gases. To meet the standards new concepts need to be developed with lower fuel consumption and emissions. This thesis covers the implementation of a couple of methods to achieve this. These concepts are DEP with fully variable valves in a port fuel SI engine with high compres-sion ratio (CR). The results show an increase in efficiency followed by lowered fuel consump-tion. The improvements in fuel consumption are mainly found to be the result of raising the CR and because of decreases in pumping losses due to de-throttling via the Miller-cycle. The reduction in pumping losses by implementing the DEP concept was not as great as expected. The results show a decrease of fuel consumption of 9.5% at part load and 5 % at high load. The main improvement with the DEP concept was the reduction of the in-cylinder residual gases at 40 CAD before top dead centre firing (TDCF). This could be enough to be able to use such high CR that otherwise just wouldn´t be possible. The thesis reveals many of the difficulties involving combustion simulation and with no ex-perimental work available in particular. The thesis would gain a lot from implementing a pre-dicted combustion model to simulate EGR and the full capability of the DEP concept in terms of affecting the combustion, by for example changing the burn rate.