On-Board Manufactured Ethers as an Ignition Improver for Alcohol Engines (Sub-Project)

Rapport, 1998

Alcohol fuels, ethanol or methanol, have low cetane number, 9 respectively 3, and are therefore not possible to use in diesel engines without engine modifications. Normal practice is to add an ignition improver to the alcohol fuel. Ignition improvers available on the market are rather expensive and are normally mixed directly into the alcohol fuel. An early concept was to inject a small amount of diesel fuel into the cylinders before injecting the alcohol. This gives satisfactory operation but requires two fuel injection systems which increase cost and maintenance. Dissolved ignition improvers of type polyethylene glycoI (PEG) are used in Scania and Volvo engines with good success but alternative additives are of interest to investigate. A prornising solution is to use an on-board reactor to generate ethers from the alcohol fuel. From ethanol (EtOH), diethyl ether (DEE) may be dehydrated and from methanol (MeOH), dimethylether (DME) may be dehydrated. Both these ethers have high cetane numbers, 90 respectively 60, and may be used as ignition improvers. This research program has been set up to evaluate the effectiveness of ethers as ignition improvers and compare the results with the conventional PEG improvers. The project was approved by the Combustion Engine Research Center (CERC) at the board meeting 1996-0] -30 and has been performed at the Department of Thermo and Fluid Dynamics. Within CERC, the partners Scania and Volvo LV have been co-sponsoring the project from the start and Aspen Petroleum. An external interested party, the Swedish Transport & Communications Research Board (KFB), has co-sponsored the ethanol part of the project. Part of the funding comes from NUTEK and CTH as partners in CERC