This experimental study examined the possible alternative fuels for heavy-duty engines, while the focus was on two specific renewable fuels: hydrotreated vegetable oil (HVO) and ethanol. These two fuels represent two extremities of fragmented fields of alternative fuels since HVO, as a "drop-in" fuel, can be di- rectly used in current diesel engine and ethanol will require significant modifications for existing engines. In this study ethanol was utilized in dual-fuel combustion concept, where ethanol was injected to intake manifold to form homogenous premixed charge to engine cylinder. Near engine top-dead-center, high-reactive diesel fuel was injected into cylinder to initialize the ignition. In studies with HVO the main focus was on exhaust gas emission – especially on nitrogen oxides (NOx) and on particulate matter (PM). As HVO has paraffinic compound and high cetane number, it enabled reduction of both NOx and PM emissions, while the effect on PM was the most evident. It was noteworthy that, as the trade-off between these two emission components is traditionally very strong, with HVO NOx and PM emissions decreased simultaneously. This behavior came more evident as the engine parameters (injection timing, exhaust gas recirculation and intake valve closure) were calibrated. In spite the PM emissions reduced significantly with HVO, the soot particle characteristics were found to be similar with the ones of fossil diesel fuel. The ethanol dual-fuel studies were carried out with both, neat ethanol and E85 blend (85% ethanol and 15% "gasoline-like" component). In these studies the focus was mainly on feasibility of the concept that was weighted mainly by the achieved ethanol share and exhaust gas emissions. The maximum ethanol share (energy based) at different engine conditions varied between circa 30% and 90%, while main limitiations were high cylinder pressure rise rate and the minimum diesel injection quantity of standard diesel injector. On exhaust gas emissions ethanol dual-fuel increased significantly both carbon monoxide and unburned hydrocarbon concentrations. This thesis focused on two different alternative fuel strategies that had significant difference on technological readiness level. HVO has already made its way to markets and has clear potential to reduce the harmful emissions of existing diesel engines. Ethanol in dual-fuel concept has evident potential, but to make its way to the markets, it will require significant research and development. The concept also will require dedicated engines, which will be a major drawback for commercial break-through. Additional advantage for HVO is that it can be distributed by existing diesel fuel logistic system, which is the case for ethanol in the most countries.
|Translated title of the contribution||Tutkimuksia vaihtoehtoisista polttoaineista työkonemoottoreihin|
|Publication status||Published - 2015|
|MoE publication type||G5 Doctoral dissertation (article)|
- alternative fuel
- heavy-duty engine
- hydrotreated vegetable oil