Engine Performance and Exhaust Emission Characteristics of a Methanol-Fueled Automobile
Laboratory and road tests showed methanol to be a very attractive, clean-burning alternative fuel for automobiles with relatively minor problems which can be overcome. A number of VW production vehicles have been converted to methanol operation through the use of an exhaust-heated intake manifold combined with a heating feature using engine coolant and, of course, a modified carburetor. Tests indicated that more power is obtained with methanol because its higher heat of vaporization cools the mixture entering the engine much more than gasoline. This increases the air-fuel mixture density and the mass flow. The gain in power output with pure methanol is about 10%.
When the vehicle is operated on pure methanol, it needs some form of cold starting aid for ambient temperatures below 8°G. There are several possibilities for improving cold starting and warm-up, such as adding volatile starting additives to methanol, using special “cold start” substances (e.g. butane, methyl ether, gasoline) which are sprayed into the intake air during starting, or employing a small flame preheater in the intake manifold.
Vapor lock is not a problem when pure methanol is used. Furthermore, tests with cars modified to run on methanol indicated acceptable to good cold-start driveability.
Fuel economy was measured during exhaust emission tests, driveability tests, and specific fuel economy tests. Because of methanol’s lower energy content, mass specific fuel consumption is noticeably greater than that with gasoline. However, fuel consumption related to consumed energy is considerably lower than that with gasoline. This means that methanol burned more efficiently than gasoline. At 2,000 rpm and wide-open-throttle, a 17% increase in brake efficiency has been observed.
Automobile exhaust emissions and air pollution can be reduced by use of methanol fueled engines. Carbon monoxide (CO) emissions from the methanol fueled engine correspond approximately to those from the gasoline engine. However, tests on a VW PASSAT 4-cylinder engine at WOT and various engine speeds showed that it is possible to reduce CO emissions from the methanol fueled engine especially at low engine speeds as compared to gasoline.
When methanol is used as engine fuel, a significant reduction in nitrogen oxides (NOx) emissions is possible. Furthermore, very low levels of hydrocarbon (HC) emissions were observed for methanol. Only about 10% of the organic emissions measured with the FID are hydrocarbons, as demonstrated by gas chromatographic techniques. Thus, methanol fueled automobiles are environmentally sound with regard to hydrocarbon emissions.
At the same compression ratio, aldehyde emissions from a methanol fueled engine are noticeably higher than from a gasoline fueled engine. However, aldehyde emission can be reduced by increasing the compression ratio, controlling the combustion process and by adding up to 10% water to methanol.
Polynuclear aromatic hydrocarbon emissions, some of which are regarded as severely carcinogenic, are more than one order of magnitude lower with methanol than with gasoline.
KeywordsCompression Ratio Engine Speed Gasoline Engine Engine Performance Exhaust Emission
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