Operation and Cold Start Mechanisms of Internal Combustion Engines with Alternative Fuels 2007-01-3609
A novel mechanism for the cold start of internal combustion engines is described in this paper. The cold-start mechanism is based on a modified prechamber configuration by adding a chamber valve to the prechamber, which could establish or block the communication of the prechamber with the cylinder space. The cold-start procedure includes a stroke that conserves the energy content of the first compressed charge through expansion against a low-pressure environment, and a subsequent recompression stroke to compress the charge to a much higher temperature. An analytical evaluation on the cold-start process is undertaken, and it is found that the charge could be compressed effectively to a temperature above the ignition temperature of ethanol or methanol. The same engine configuration may also enable combustion under a closed-chamber condition and is employed during the engine warm-up process to reduce excessive hydrocarbon emissions due to incomplete combustion.
The cold-start/warm-up mechanisms introduced in this paper will provide a useful tool for cold starting an engine using both conventional and alternative fuels. The mechanisms could even cold start a compression-ignition engine using pure ethanol or pure methanol, thus overcoming one of the most serious problems related to ethanol or methanol fuel. Since the mechanisms can drastically reduce the hydrocarbon emissions from both conventional and alternative fuel engines during the cold-start/warm-up processes, they may also represent an effective solution for hydrocarbon-emission related environmental problems.