Many times we come around terms like Super Charged engine or Turbo Charged engine. In this post of my I will be discussing the concept of Super Charging an I.C. Engine.
A common I.C engine 2 stroke or 4 stroke which most of us are aware of can be also termed as naturally aspirated engine which in simple language means air or air fuel mixture taken into inlet is more or less is in natural state.
The power developed by a naturally aspirated engine depends upon following factors:-
1) Amount of air introduced into cylinder per cycle.
2) Degree of utilization of induced air.
3) The engine speed and thermal efficiency.
4) Quality of fuel admitted and its combustion characteristics like its calorific value.
Thus by increasing the engine speed or by increasing the density of air at the inlet, it is possible to increase the amount of air inducted in the engine per unit cylinder. But as the engine speed increases it leads to higher inertia load thereby requires a robust engine in order to stand the stresses.
Also higher engine speed cause for decrease in the volumetric efficiency, higher friction and increased bearing load.
Thus increasing the density of air the inlet is more suitable to avoid these complications and this process is called as “Super Charging”.
The following points needs to be noted in the process of Super Charging:-
1) It increases the power output of the engine.
2) It leads to higher forces so the engine should be designed to stand these higher forces.
3) The power for air compression has to be taken from the engine itself but the net power output will be more than the same engine without Supercharging.
4) The higher pressure & temperature may lead to detonation. Therefore fuel with better antiknock characteristics is required.
Method of Supercharging:-
The above figure shows the Super Charging of engine by a compressor.
As we can see that a certain amount of power is taken from the engine to run the compressor connected through gears to the engine. The compressor takes the air from inlet and compresses it and sends it to the cooler where it gets cooled and then the high density air sent to the engine through the inlet valve mixed with fuel for S.I. (Spark Ignited) engine or simply dense air is sent for C. I. (Compression Ignited) engine. This process thus increases the mass of air or air fuel mixture inducted for the same swept volume and thereby increases the power output of the engine.
Advantages of Super Charging:-
1) Power output of the engine is increased.
2) Better automization of fuel is possible.
3) Better mixing of air fuel is possible.
4) Better scavenging of exhaust gases is possible.
5) Torque is improved for whole speed range and better torque at lower speed hence it leads to faster acceleration of the engine.
6) Mechanical efficiency is improved and efficient combustion is possible hence specific fuel consumption is lowered slightly.
7) In C.I. engine exhaust smoke is reduced.
Disadvantages of Super Charging:-
1) Detonation tendency increases in S.I. engine
2) Heat losses due to turbulence and thermal stress are more.
3) The valve overlap period is increased up to 1600 of crank angle.
4) Better lubrication, cooling of piston and valves are required.
5) Cost of engine is increased.
This is how Super Charging an I.C. engine enhances its power output capacity. With this I would like to end my talk.
Your comments shall be highly appreciated
SIGNING OFF:-
MD. AFZAL ANSARI
7TH SEM MECHANICAL ENGINEERING
BANGALORE.