A Ramesh

In this work a two-stroke scooter engine was modified to work with semi-direct injection of gasoline at a pressure of 8 bar from an injector in the cylinder barrel pointed toward the cylinder head. The influence of injection timing, injection pressure, spark plug location and air-fuel ratio, on performance, emissions and combustion characteristics has been investigated. In addition, a comparison has been made with manifold injection of gasoline on the same engine at a given speed and various outputs. A significant reduction in HC emissions and fuel consumption with no adverse effects on NOx emissions and combustion stability was observed. A small drop in power and increase in CO emission were observed disadvantages of the new injection system. Injection timing was found to be the most important factor and a balance between reduction in shortcircuited fuel by late injection, and time for mixture preparation by advancing the injection, was found to be essential. © 2009 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg GmbH.

In this work a novel mixture injection system has been developed and tested on a two stroke scooter engine. This system admits finely atomized gasoline directly into the combustion chamber. It employs many components that were individually developed, fabricated, tested and then coupled together. A small compressor driven by the engine sends pressurized air at the correct crank angle through a timing valve. This is connected to a mechanical injector through a high pressure pipe. Fuel is metered into the high pressure pipe using a standard low pressure injector. The developed mixture injection system resulted in considerable improvements in thermal efficiency and reduction in HC emissions over the manifold injection method at all engine outputs. A considerable reduction in short circuiting losses was seen. The highest brake thermal efficiency achieved was 25.5% as against 23% with the manifold injection system. The minimum HC level is 460 ppm where as for manifold injection it is 1360 ppm. Better combustion with the developed system lead to a small increase in the peak NO level as compared to the manifold injection system. Further improvements are possible by redesigning the compressor and combustion chamber.

Gasoline and liquefied petroleum gas (LPG) were injected into the manifold of a 145 cc two stroke engine using a specially developed electronic circuit to have a close control over the air fuel ratio. Experiments were carried out at 3000 rev min-1 and fixed throttle positions of 10, 15, 25, 40, 50 and 100% of full opening. The amount of fuel injected (air fuel ratio), injection timing and injection pressure were varied. The maximum brake thermal efficiency with LPG was 25% and that with gasoline was 23%. The engine could generally operate with much leaner mixtures with LPG due to its good mixture formation capability. HC levels and exhaust gas temperature were slightly higher with LPG while NO levels were comparable. It was found that the injection pressure had to be reduced at part throttle conditions in order to get better engine stability and performance. The maximum power output with LPG was lesser than that with gasoline. © 2007 Energy Institute.

Simple and cost effective electronically controlled injection systems have to be developed to combat the problem of urban pollution. In this work an electronically controlled fuel injection system developed in the Internal Combustion Engine Laboratory of Indian Institute of Technology Madras has been tested in detail on a two-stroke SI engine. The system is fitted on the intake manifold of a single cylinder, air cooled two-stroke scooter engine. Tests have been done at 3000 rpm and 4000 rpm at different throttle positions. The optimum injector pulse widths for thermal efficiency, lowest HC emissions and highest power are all different. The maximum brake thermal efficiency values are 22.6% and 23% at 3000 and 4000 rpm respectively. At a power output of 3 kW and 4000 rpm the brake thermal efficiency is about 21% for the carbureted engine. It increases to 23% with the fuel injection system. HC emissions are considerably lower than the carbureted version at all operating conditions and speeds. The engine can work with leaner mixtures with the injection system in general as compared to the carburetor. The maximum power increases with the injection system. The developed system can be used for mapping the engine for the development of software for injection system control.