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Abstract
A compression ignition engine with a mechanical fuel system was converted into common rail fuel system by means of a self-developed electronic control unit. The engine was modified to be operated with mixtures of diesel and natural gas fuels in dual-fuel mode. Then, diesel fuel was injected into the cylinder while natural gas was injected into intake manifold with both injectors controlled with the electronic control unit. Energy content of the sprayed gas fuel was varied in the amounts of 0% (only diesel fuel), 15%, 40%, and 75% of total fuel's energy content. All tests were carried out at constant engine speed of 1500 r/min at full load. In addition to the experiments, the engine was modeled with a one-dimensional commercial software. The experimental and numerical results were compared and found to be in reasonable agreement with each other. Both NOx and soot emissions were dropped with 15% and 40%, respectively, energy content rates in gas-fuel mixture compared to only diesel fuel. However, an increase was observed in carbon monoxide emissions with 15% natural gas fuel addition compared to only diesel fuel. Although smoke emission was reduced with natural gas fuel addition, there was a dramatic increase in NOx emissions with 75% natural gas fuel addition.
Keywords
Diesel engine, natural gas, emissions, NOx, smoke, engine performance
Date received: 14 December 2015; accepted: 7 March 2016
Academic Editor: Jose Ramon Serrano
(ProQuest: ... denotes formulae omitted.)
Introduction
Fast extinction of fossil fuels and increasing oil prices impose engine manufacturers to work on alternative fuels and power trains.1 Due to the negative effects of petroleum-derived fuels on the environment and human health, studies on alternative, reliable, and environmental fuels have become an inevitable requirement.2 Nowadays, an important part of the energy requirements in the transport sector is still covered by fossil fuels. In spite of Kyoto Protocol, carbon dioxide (CO2) emissions increased by 27%, while the amount of CO2 emissions stemming from transport vehicles increased by 37% in the world between 1990 and 2004.3
More rigorous emission regulations are demanding nearly ''0'' NOx emissions.4 Despite high efficiency of diesel engines, they have a disadvantage in terms of NOx and soot particles emissions.5 NOx gases react to form soot and acid rain which are really hazardous...