A two-stroke engine is a type of internal combustion (IC) engine that completes the power cycle in one crankshaft revolution, which is half the number in comparison with four-stroke engine. Spark Ignition (SI) two-stroke engines are commonly found in the small power tools such as chain saw and scooter. While Compression Ignition (CI) engines are commonly used in large machines such as marine propulsion and electricity generator.
Two-stroke engines have several inherent advantages over four stroke engines such as simple and compact design, high power-to-weight ratio, lower NOx emissions etc. The piston of the two-stroke reciprocating engine takes over valve functions in order to obtain a power stroke for each revolution of the crankshaft. The valve overlap period in case of two stroke SI engines is greater than four stroke SI engines; this loss of fresh fuel is called short-circuiting [1]. This accounts for major source of hydro-carbon (HC) emissions and increased specific fuel consumption in two stroke SI engines. Independent fuel supply system could easily reduce inherent disadvantages of higher hydrocarbon emissions and low fuel economy.
The most essential issue to be tended to by a conventional two stroke SI Engines is the consistence with stringent emission standards, which relies upon the combustion pattern and the scavenging efficiency Gasoline direct injection is the only practical solution for emissions, generated by short-circuiting as well as incomplete combustion. The impact of injection variables on the performance parameter along with combustion, its extend feasibility and complexity are reviewed in present work. The injection variables include injection timing (start of injection), injection pressure, injector axis and injection pattern (wall guided/spray guided/air guided). The review comes up with the need of optimization for mixture formation to reduce in-cylinder wall wetting, increase combustion stability and performance parameters in GDI engine. The current study reviews the development process, assisted by 1D & 3D CFD analysis tool. Engine performance parameters have been predicted using well-established commercial software AVL Boost, while 3D CFD analysis have been carried out using ANSYS Fluent 18.0. The simulated 1D model and 3D CFD model shows good co-relationship with the experimental results of baseline two stroke carburetted engine tested at wide open throttle condition. CFD based optimization is performed to choose injection strategy for maximizing the engine power output and ensuring complete combustion prior to exhaust port opening. The improvement in results are due to inherent advantages of two stroke engines along with the capability to inject fuel post exhaust port closing and charge stratification using gasoline direct injection system.