In developed and developing countries considerable emphasis is being laid on the minimization of pollutants from internal combustion engines. A two-stroke cycle engine produces a considerable amount of pollutants when gasoline is used as a fuel due to short-circuiting. These pollutants, which include unburnt hydrocarbons and carbon monoxide, which are harmful to beings. There is a strong need to develop a kind of new technology which could minimize pollution from these engines.
Direct fuel injection has been demonstrated to significantly reduce unburned hydrocarbon emissions by timing the injection of fuel in such way as to prevent the escape of unburned fuel from the exhaust port during the scavenging process.
The increased use of petroleum fuels by automobiles has not only caused fuel scarcities, price hikes, higher import bills, and economic imbalance but also causes health hazards due to its toxic emissions. Conventional fuels used in automobiles emit toxic pollutants, which cause asthma, chronic cough, skin degradation, breathlessness, eye and throat problems, and even cancer.
In recent years, environmental improvement (CO2, NOx and Ozone reduction) and energy issues have become more and more important in worldwide concerns. Natural gas is a good alternative fuel to improve these problems because of its abundant availability and clean burning characteristics.
1.1. The objectives of present study are:
To compare the performance of a carbureted and injected engine at constant speed. Direct injection system was developed which eliminates short circuiting losses completely and injection timing was optimized for the best engine performance and lower emissions.
In a lean burn engine, air fuel ratio is extremely critical. Operation near the lean mixture limit is necessary to obtain the lowest possible emission and the best fuel economy. However, near the lean limit, a slight error in air-fuel ratio can drive the engine to misfire. This condition causes drastic increase in hydrocarbon emission; engine roughness and poor throttle response.
A reliable electronic gaseous fuel injection system was designed and built in order to control the engine and also for the evaluation of control strategies. The electronic control unit is used to estimate the pulse width of the signal that would actuate the fuel injector and the start of fuel injection. The experiments were carried out on the engine using state-of-art instrumentation.