Dimethyl ether (DME) can be converted easily from methanol in a catalytic reactor, and it has very good compression ignition characteristics. This paper presents experimental results on a compression ignition methanol engine with DME as an ignition improver. The results show that engine operation is sufficiently smooth with high efficiency without spark or glow plugs.
In the experiments, two methods for DME introduction were investigated: an aspiration and a torch ignition method. The aspiration method introduces DME into the intake manifold, and is structurally simple but suffers from poor emission characteristics at partial loads, and a large amount of DME is required for ignition. With the torch ignition method, DME is introduced into a torch ignition chamber during the intake stroke, and significant reductions in both the necessary DME quantity and emissions were obtained. Engine operation was also attempted with DME-dissolved methanol fuel without ignition aids.
METHANOL is a clean burning alternative fuel for diesel engines, and its applications have been extensively investigated. The purpose of this research is to demonstrate operation of compression ignition engines (diesel engines) with pure methanol without ignition plugs. In the study, dimethyl ether (DME) was used as an ignition improver. The DME has very good compression ignition characteristics and it is easily converted from methanol with an alumina catalyst.
Using DME in methanol engines, Kozole et al. have reported that cold startability with spark ignition was improved from 10°C to -15°C by aspirating DME into the intake manifold[1]. Green et al. showed that compared to glow plug engines, combustion and emissions of compression ignition methanol engines improved remarkably at partial loads by aspirating DME[2]. Galvin et al., Cipolat et al., and Karpuk et al. also showed stable ignition and combustion of methanol engines by introducing DME into the intake manifold[3], [4] and [5].
The present study first examined engine performance and emissions with DME aspirated into the intake manifold, and identified the potential and problems of the method. Next, a new combustion system with a torch ignition chamber (TIC) was developed to reduce the DME quantity and emissions. Additionally, as DME easily dissolves in methanol, engine operation with DME-dissolved methanol fuel was investigated. Finally, the effect of the DME conversion rate on engine performance was investigated by changing the DME to methanol vapor ratio.