I am sure that most of you have already made so many thoughts in your mind by just reading the title; A Supercharged Two Stroke engine. It is one step ahead of two stroke engine. Let’s first discuss some common advantages and disadvantages of two stroke engine. Most of us know how the two stroke engine works. It uses only two strokes to produce power from air fuel mixture. We cannot distinguish between the suction, compression, power and exhaust strokes.
Two stroke engine uses ports instead of inlet and exhaust valves: Inlet port, Transfer port and Exhaust port. Opening of these ports are controlled by piston movement only. No separate mechanisms are provided to operate these ports.
At high speed of two stroke engine, these ports overlap with each other and increase the loss of fresh charge from the cylinder. Let’s have some pros and cons of two stroke engine over four stroke.
- Two stroke engine is very light in weight because of fewer parts
- More mechanical power output because of better turbulence in cylinder
- Easier to manufacture and assemble
- Less unbalance forces due to few reciprocating parts
- Loss of fresh charge from the cylinder at the time of scavenging, resulting in poor fuel efficiency
- More emissions because of incomplete combustion at high speed
- Very noisy
Despite of many more drawbacks from the two stroke engines, they are very popular for getting more mechanical power. One of my students thought to bring out some modifications for the two stroke engine to have improved fuel efficiency with more power at the same time. The only solution we got in our minds was supercharger. Some big machine like marine engines uses superchargers in two stroke engines.
Supercharger works like a turbine to throw the air in to the cylinder. This provides more air in to the cylinder than the engine naturally does. Excess air helps to ignite more fuel particles which generally left the engine without having combustion. This helps the engine to improve the power output at same RPM. But still we also have to improve the fuel efficiency.
Carburettor supplies the fuel air mixture to the cylinder without measuring the amount needed. Engine has to burn the supplied amount of air fuel mixture and if fails, it throws this charge in to the exhaust port without any combustion. That’s why, for getting better fuel consumption, we are planning to incorporate fuel injection rather than carburettor.
No doubt, we will have to work more to have correct injection timing, otherwise it will again leads to more fuel consumption. Finally let me explain you hoe these all components going to work for our triumph. We are going to shut down the transfer port which is originally used to transfer the fresh air fuel mixture. At this place, we are planning to generate air vent for crank case ventilation.
The supercharger will be run by engine itself and will provide excess amount of air to the cylinder. This air will try to scavenge all exhaust gases from the cylinder to the exhaust port. Write now, this scavenging is done by fresh air fuel mixture coming from the transfer port, which also helps the fresh charge to escape from the cylinder. In our set up, only the air will be going to escape the cylinder.
After the proper scavenging and at the right time, we will inject the fuel in the inlet port of the engine. After the injection, air and fuel will get mix because of turbulence and will get combust with the help of spark plug. As we are going to supply sufficient air for the fuel for combustion, the efficiency will also improve and so as the emissions.
At present, we are doing literature survey on this type of combinations. This will help us to locate and operate the systems efficiently. We can also defend our work on the basis of this literature survey. We have planned to complete the fabrication and commissioning of this project till December 2011. I assure you all that we will definitely discuss the results of my project whatever and whenever it may be. Please share your ideas and experience to improve my success rate for this project.
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