Analysis Of Performance Of Biogas/Bio-diesel Dual-fuel Engine

In the recent years, with the rapid development of industry and agriculture, problems of dwindling oil resources, increasingly serious air pollution and increasingly stringent emissions regulations have put a great pressure to our mankind. People have to seek cleaner alternative sources of energy. Among many substitute fuels, we found that both biomass-based methane and bio-diesel are good renewable fuels. Because methane contains quite a large part of CO₂, the combustion of methane engine become quite slowly; the engine's CO and HC emissions grow up. And at heavier load oxygen deficiency in the engine becomes even more serious. Because bio-diesel contains some oxygen, so the engine has lower emission of CO and HC, but its NO_x emissions rise up.To achieve efficient mixed combustion of methane and bio-diesel in a direct injection (DI) diesel engine, and to make use adequately of the advantageous physicochemical and combustion characteristics of methane and bio-diesel, a special dual-core electronic control unit (ECU) with control model and methane electronic control injection system was developed. So the 295T DI diesel engine can be fueled successfully with methane/bio-diesel dual-fuel with the help of the electronic control multi-point methane injection system. Taking diesel oil and methane/bio-diesel as fuel respectively, performance tests of the refitted engine had been done under the same condition.Test results indicate that the refitted engine fueled with methane/bio-diesel dual fuel has a slightly higher power performance; a higher thermal efficiency and lower equivalent fuel consumption. Its NO_x emission becomes lower. And its CO level is closed to that of the prototype diesel engine. But its HC emission level becomes higher compared with the prototype diesel engine. The results further show that the development of electronically controlled gas injection system is reliable, stable, rapid corresponding and precise for control of gas jet quantity. Combination of methane and bio-diesel may help to reach complete combustion in the dual fuel engine. This combination enhances both fuels' advantages and offset their disadvantages. This arrangement can reduce NO_x emissions and to retard the decline of power in a gas engine. Because of the reduction of air into the cylinder which reduces the O₂, a direct result of the HC emission level was higher compared with the prototype diesel engine. To reduce the HC emissions a turbocharger or a HC absorber should be used. For the limit of test conditions, we have not adopted turbocharger and HC absorber.