Effect of Supercharging on the Performance of the Engine?

Supercharging is used only for aircraft and racing car engines. This is because the increase in supercharging pressure increases the tendency to detonate and pre-ignition. Supercharging is used in the engine to increase the volumetric efficiency of the engine. In this article, I will discuss the effect of Supercharging on the Performance of the Engine. 

Effects of supercharging on the performance of the engine-

Effect of supercharging

Apart from increasing the volumetric efficiency of the engine supercharging results in an increase in the intake temperature of the engine. Supercharging affects the performance of the engine in various ways. Let's see the details- 

Power output- 

The power output of a supercharged engine is higher than its naturally aspirated counterpart due to the following reasons :

1. The amount of air inducted per cycle for a given swept volume is increased.
2. The mechanical efficiency is slightly improved.
3. During the gas exchange process, some of the work done on the supercharger is recovered.
4. Supercharging results in better scavenging and reduced exhaust gas temperatures in the engine. The reduced residual gas fraction helps in better combustion and reduced temperature improves volumetric efficiency.

Mechanical Efficiency- 

An increase in the supercharging pressure increases the gas load and hence large bearing areas and heavier components are needed. This increases the frictional forces. However, the increase in bmep is much more than an increase in frictional forces. The mechanical efficiencies of supercharged engines are slightly better than those of naturally aspirated engines.

Read more- What is the meaning of zero depreciation in car insurance. 

Fuel consumptions- 

This supercharger is directly driven by the engine, and some of the power developed by the engine will be used in running the supercharger. Moreover, at part loads, the compression of the supercharger is not fully utilized. this will result in greater loss, hence the specific fuel consumption for mechanically driven superchargers will be more at part loads.  In spite of better mixing and combustion due to reducing delay, a mechanically supercharged otto engine will almost always have specific fuel consumption higher than a naturally aspirated engine. The specific fuel consumption for the CI engine is somewhat less than that for naturally aspirated engines due to better combustion and increased mechanical efficiency. 

Supercharging of engines-

Supercharging does not result in any combustion problem, rather it improves combustion. in a diesel engine. An increase in pressure and temperature of the intake air reduces ignition delay and hence the rate of pressure rise resulting in better, quieter, and smoother combustion. This improvement in combustion allows a poor quality fuel to be used in a diesel engine and it is also not sensitive to the type of fuel used. The increase in intake air temperature reduces volumetric and thermal efficiency but the increase in the density due to pressure compensates for this and inter-cooling is not necessary except for highly supercharged engines. However. mechanical and thermal loading increases with an increase in supercharging. But this increases with an increase in supercharging. But this increase in mechanical and thermal loading is only moderate because of the use of lower compression ratios and the effect of cooling due to increased valve overlap of the supercharged engine. It is possible to use lower fuel-air ratios in a supercharged engine as the increase in fuel flow is less than the increase in airflow. This results in lower temperatures over the full engine cycle and reduced smoke from the engine. Low fuel-air ratio and high expansion ratio result in lower exhaust temperature. This results in an increased life of the exhaust valves.

Conclusion- 

Supercharged petrol engines have a greater fuel consumption than naturally aspirated engines. Because of its poor fuel economy, supercharging petrol engines are not very popular. In this article, I cover the topic of the effects of supercharging on the engine.