Some advantages and challenges of running a Euro IV, V6 diesel engine on a gasoline fuel

Previous work has demonstrated that single-cylinder CI engines, with relatively modest changes to operating conditions over a wide operating range, can be run with both very low NOx and low smoke as well as at high efficiency on fuels with high resistance to autoignition such as gasoline. The purpose of this work was to run a multi-cylinder engine without any major changes to the engine system on a gasoline fuel at constant fuel demand to get better understanding of the possible practical advantages and challenges. A 2.7 dm ³ Euro IV V6 diesel engine was run on a European standard diesel fuel of 54 CN (Cetane Number) according to the engine map at 1000 rpm and 1500 rpm at different loads. At the same speeds and loads, it was also run on a 84 RON gasoline but with different injection strategies and operating parameters, such as EGR levels. With gasoline, NOx levels comparable to the diesel map point could be obtained but at lower EGR rates, at lower injection pressures and lower brake specific fuel consumption and with extremely low smoke; however the CO and HC emissions were higher. The engine could not be run at high speeds or at loads greater than 12 bar IMEP on gasoline because, without introducing modifications, the fuel overheated and gave rise to vapour-lock problems. Also at high loads, in order to limit NOx emissions, high EGR rates were required but the CO levels were excessive, because the particular turbocharger could not deliver adequate intake pressure at such conditions and hence the intake oxygen levels were too low. Thus further modifications to the fuel system and an alternative turbocharger would be needed to extend the operating range on gasoline. There appears to be potential for simplifying future CI engines e.g. by using lower injection pressures and replacing lean NOx after-treatment by CO and HC control by using gasoline-like fuels.