Search Results

Using the KVIA code as a reference, a two dimensional computational fluid dynamics program is used to analyze the scavenge and fuel injection processes in a two--stroke engine: By calculation, the flow velocity, the mass distribution and density distribution of compositions (including the air, fuel and exhaust) and the escaped mass of fuel from the exhaust ports are known. It models the work process of the direct--injected two--stroke engine. By analysing the computational results, the best injector location, injection angle and injection timing can he determined. IT IS A WELL KNOWN FACT THAT THE TWO--STROKE ENGINE'S ADVANTAGES ARE high specific power, simple structure, light weight and the small outline. The main disadvantage of the two--stroke engine with the carburettor is that some 25-40% of the unburnt fresh charge during the gas exchange process is lost due to the short circuiting to the exhaust ports. This inevitably results in poor fuel economy and high hydrocarbon emissions.

Using methanol to replace the diesel fuel in diesel engine is a simple way in using of alternative fuel. But the main problems are that the max. cylinder pressure and the cylinder pressure rising will be increased. This increases the mechanical load engine noise and affects the engine reliability. Also limits increasing the ratio of methanol to diesel fuel. This paper presents an new way of using EGR to control the cylinder pressure and to raise the ratio of methanol to diesel fuel. There are many ways to burn methanol in diesel engines. Generally, the liquid methanol is vaporized by heating of exhaust pipe or and cooling water, then it mixes with air through intake pipe, finally, burns in the cylinder. The advantages of this method are that the structure of diesel engine needs no change. By using the exhaust heat to vaporize the liquid methanol, the wasted heat can be utilized again. So it is helpful to improve the thermal efficiency. However, there are some shortages.

An expert system for analysing the performance and diagnosing faults of d.I. diesel engine is presented in this paper. This system consists of three parts. First is the transient data acquiring part by which the incylinder pressure, fuel pipe pressure and other parameters can be acquired through the A / D transforming circuits. Second is the simulative calculation and analysis part by which most of the parameters, such as the fuel injection rate, fuel heat release rate etc. can be calculated. Third is the expert diagnostic part established on the fuzzy theory, which is applied to evaluate the matching relations among various transient parameters. Some faults of engine can be detected by this part. Furthermore, the proposals to improve the performance of engine can be put forward by this system.