What Wikipedia Can't Tell You About Supercharger And Turbocharger?
Need Of Supercharger Or The Turbocharger:
As we all know the power output of any engine is depends upon the amount of air inducted per unit time, degree of the utilization of air and the thermal efficiency of the engine. Thus the power output can be improved by following methods:
1) By Increasing The Cubic Capacity ( Displacement):
By increasing the cubic capacity (displacement) of engine more air can be induced in the combustion chamber, but that will increase the size and weight of the engine and cooling problems are also incresed. It only becomes helpful, if power to weight ratio of that engine is enhances in positive manner.
2) By Running The Engine At High Speed:
As engine runs at high speed, the amount of air induced per unit time also increases, but operating the engines at high speed is not good for the engine as its life lowers and maintenance problems may arise. Because due to high operating speed mechanical friction losses are also more and due to the inertia, stresses are developed in the engine parts.
3) By Increasing The Density Of Charge:
This method allows inducting the denser charge into the combustion chamber by keeping other constraints same.i.e. stroke or bore etc.
Finally inducting the denser charge for combustion process is better than other methods and this is called as the 'supercharging'. In that case the amount of air entering the combustion chamber per cycle is increased by some external means. The device used for providing the denser charge is a blower or compressor and that is called as 'supercharger'.
The supercharger is fitted in generally aircraft and racing engines to produce and maintain higher output. Due to the induction of the densor charge the volumetric efficiency of engine also increases.
But in case of SI engines, the supercharging results in increased intake temperature due to air comression (P ∝ T) and this reduces the ignition delay and increases the flame propogation speed. Both this effects of the supercharging result in the pre-ignition or knocking of engine and severelly affects engine components.
For that reason, supercharged SI engines are designed with lower compression ratio and low maximum-rpm. The best way to get rid of this problem is to equip aftercooler or intercooler to reduce the temperature of the air. It may either air to air heat exchanger or air to liquid heat exchanger for the even better cooling purpose.
In the case of CI engine, the supercharging does not create the combustion problem, rather it improves combustion. Increase in temperature and pressure due to the supercharging process reduces the ignition delay. And this rise in pressure results in better,smoother and quieter combustion. Because in CI engine, only air is compressed and fuel is injected through fuel injector according to ignition timing and no chance of pre-ignition.
Difference Between Supercharger & Turbocharger:
In Case of the supercharger, the air compressor is generally blower or positive displacement type compressor and it is driven by the engine crankshaft itself through the arrangement of belt or gear transmission. This allows quick throttle response, as supercharger or air compressor is directly driven by the engine. For high altitude planes or more pressure requirement, multi-staging of the compressor is done in order to maintain optimum weight and size of the compressor and overall system.
In the turbocharged engine, the blower or air compressor are mounted on the same shaft. First of all the engine runs normally. As the exhaust gases pass over the turbine, it starts running and drives the compressor, and power required to drive the blower or air compressor is not taken by the crankshaft. This is the concept behind the turbocharger.
As the power required to drive the compressor is not taken from the crankshaft directly, so that turbocharger is supposed to more efficient. But due to the turbine is run by the exhaust gases, turbocharged engine has the slower response to the throttle. This slower response is called as turbo lag.
The main problem with the turbocharged engine is, it does not provide quick power boost i.e. turbo lag, due to it require few seconds after pressing the throttle to get the turbo on the move.
That turbo lag can be reduced by reducing the inertia of the rotating parts. As inertia depends on the distance and mass (we generally say weight), we can reduce the turbo lag by the reduction in the weight of the moving parts. This will allow the turbine and compressor to react earlier, and it will provide quick turbo boost.
As we all know the power output of any engine is depends upon the amount of air inducted per unit time, degree of the utilization of air and the thermal efficiency of the engine. Thus the power output can be improved by following methods:
1) By Increasing The Cubic Capacity ( Displacement):
By increasing the cubic capacity (displacement) of engine more air can be induced in the combustion chamber, but that will increase the size and weight of the engine and cooling problems are also incresed. It only becomes helpful, if power to weight ratio of that engine is enhances in positive manner.
2) By Running The Engine At High Speed:
As engine runs at high speed, the amount of air induced per unit time also increases, but operating the engines at high speed is not good for the engine as its life lowers and maintenance problems may arise. Because due to high operating speed mechanical friction losses are also more and due to the inertia, stresses are developed in the engine parts.
3) By Increasing The Density Of Charge:
This method allows inducting the denser charge into the combustion chamber by keeping other constraints same.i.e. stroke or bore etc.
Finally inducting the denser charge for combustion process is better than other methods and this is called as the 'supercharging'. In that case the amount of air entering the combustion chamber per cycle is increased by some external means. The device used for providing the denser charge is a blower or compressor and that is called as 'supercharger'.
The supercharger is fitted in generally aircraft and racing engines to produce and maintain higher output. Due to the induction of the densor charge the volumetric efficiency of engine also increases.
But in case of SI engines, the supercharging results in increased intake temperature due to air comression (P ∝ T) and this reduces the ignition delay and increases the flame propogation speed. Both this effects of the supercharging result in the pre-ignition or knocking of engine and severelly affects engine components.
For that reason, supercharged SI engines are designed with lower compression ratio and low maximum-rpm. The best way to get rid of this problem is to equip aftercooler or intercooler to reduce the temperature of the air. It may either air to air heat exchanger or air to liquid heat exchanger for the even better cooling purpose.
In the case of CI engine, the supercharging does not create the combustion problem, rather it improves combustion. Increase in temperature and pressure due to the supercharging process reduces the ignition delay. And this rise in pressure results in better,smoother and quieter combustion. Because in CI engine, only air is compressed and fuel is injected through fuel injector according to ignition timing and no chance of pre-ignition.
Difference Between Supercharger & Turbocharger:
In Case of the supercharger, the air compressor is generally blower or positive displacement type compressor and it is driven by the engine crankshaft itself through the arrangement of belt or gear transmission. This allows quick throttle response, as supercharger or air compressor is directly driven by the engine. For high altitude planes or more pressure requirement, multi-staging of the compressor is done in order to maintain optimum weight and size of the compressor and overall system.
In the turbocharged engine, the blower or air compressor are mounted on the same shaft. First of all the engine runs normally. As the exhaust gases pass over the turbine, it starts running and drives the compressor, and power required to drive the blower or air compressor is not taken by the crankshaft. This is the concept behind the turbocharger.
As the power required to drive the compressor is not taken from the crankshaft directly, so that turbocharger is supposed to more efficient. But due to the turbine is run by the exhaust gases, turbocharged engine has the slower response to the throttle. This slower response is called as turbo lag.
The main problem with the turbocharged engine is, it does not provide quick power boost i.e. turbo lag, due to it require few seconds after pressing the throttle to get the turbo on the move.
That turbo lag can be reduced by reducing the inertia of the rotating parts. As inertia depends on the distance and mass (we generally say weight), we can reduce the turbo lag by the reduction in the weight of the moving parts. This will allow the turbine and compressor to react earlier, and it will provide quick turbo boost.
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