Direct Fuel Injection of LPG in Small Two-Stroke Engines

The commonly used carburetted two-stroke engines in developing countries have high exhaust emission and poor fuel efficiency. To meet more rigid emissions requirements, two-stroke vehicles are typically phase out in favour of four-stroke engines. The problems of ubiquitous legacy two-stroke vehicles remain unsolved by these measures and they are likely to be a major source of transport for many years to come. A number of technologies are available for solving the problems associated with two-stroke engines such as catalytic after-treatment and direct fuel injection (DI). However, these solutions are relatively high cost and have shown only slow market acceptance for applications in developing countries. Research in recent years has demonstrated that direct fuel injection is a well developed and readily deployable solution to existing two-stroke engines. Gaseous fuels such as Liquefied Petroleum Gas (LPG) are considered a promising energy source and in many countries provide fuel cost savings. LPG coupled with DI two-stroke technologies, is expected to be clean and cost effective retrofit solution for two-stroke engines. In this research project, direct injection (DI) of Liquefied Petroleum Gas (LPG) is introduced and tested on a typical two-stroke engine. Results of in cylinder combustion pressure translated to fuel mass fraction burned, engine performance and exhaust emissions are taken and compared for various injection timings from premixed (early injection) to fully direct injection mode (late injection). Results show that DI of LPG effectively reduces exhaust hydrocarbon and can substantially improve the fuel economy of two-stroke engines

Genset Optimization for Biomass Syngas Operation

Although biomass is underrepresented in current methods for power generation, it has great potential to help meet the growing need for clean energy. This chapter details the modification of a gasoline-powered two-stroke genset for operation on syngas from a woodchip-powered gasifier. Generator and engine modifications along with a flexible air/fuel control system are described. Results from genset operation indicate a sustainable power output of 360 W with a biomass consumption rate of approximately 6 kg/hour. Optimum power production was achieved at an air/fuel ratio close to 1. After several hours of operation the engine was disassembled and inspected, revealing significant deposits on the piston and crank case parts, indicating that the engine would require weekly maintenance under such operating conditions

Variation of Air Flow Pattern Through Dissimilar Valve Lift In A Spark Ignition Engine

Bi-fuel conversions are a common alternative fuelling option for mono-fuel gasoline SI vehicles because of the minor vehicle modifications required. In Malaysia, most bi-fuel vehicles are fuelled with compressed natural gas (CNG) and gasoline. However, CNG flame speed is lower than gasoline reducing the power and range of the vehicle when operating on CNG. This situation can be improved by increasing the flame speed via higher swirl generation. A computational fluid dynamics model is used to analyse swirl generated by dissimilar valve lift (DVL) profiles on the intake valve. A three-dimensional engine simulation shows differences in swirl motion and turbulence between the original symmetric valve lift profile and the DVL. The higher swirl number reduces the turbulence kinetic energy level slightly. The best case profile is selected for further experimental testing

Effect of Dissimilar Valve Lift on a bi-fuel CNG Engine Operation

Abstract The combustion of spark ignition engines converted to bi-fuel CNG is unstable and proper air and fuel mixing strategy is a concern. Also, CNG fuel causes the coefficient of variation for indicated mean effective pressure (COVimep) higher than 10 which is into the region of unstable combustion. In order to create stable combustion more turbulence is required. This paper studies the valve movement with dissimilar valve lift (DVL) to increase swirl in the engine. The intake valve is the last point of airflow entry into an engine and the modification of the movement can contribute to increase turbulence. Three {DVL} setting simulated via computational fluid dynamics (CFD) gave improvement in peak pressure by 4 and a 32.2 improvement in flame propagation speed compared to baseline CNG. Engine testing shows that, the engine {COVimep} improves up to 8.7, while efficiency improves by 5.7 and {BSFC} is reduced by 5.4 respectively with the 1Â mm {DVL} at 4000Â rpm compared to baseline CNG. The rate of heat release (ROHR) also shows early heat release of the fuel. The novelty is better mileage for future {CNG} engine design