COMPARISON OF GAS TURBINES WITH IC ENGINES

1 Advantages

1. Perfect balancing of the rotating parts is possible.
2. Mechanical efficiency is very high (≈95%) compared with 85% of IC engine because of its large number of sliding parts.
3. Torque on the turbine shaft is continuous and uniform; therefore, flywheel is not required.
4. Work developed is more because expansion of gases up to atmospheric pressure is possible.
5. The weight of the gas turbine per kW of power developed is less, and therefore, they are superior for use in aircraft.
6. The compression, combustion, and expansion take place in different units. Therefore, these units can be designed, tested, and developed individually.
7. The gas turbine can be driven at much higher speeds.
8. The maximum pressure used in gas turbines is very low; therefore, its components can be made lighter.
9. The lubrication and ignition systems are much simpler.
10. Cheaper fuels can be used in gas turbine.
11. The installation and maintenance costs are less.
12. The exhaust is free from smoke and is less polluting.

2 Disadvantages

1. The thermal efficiency of a simple gas turbine is low.
2. There is very poor thermal efficiency at part loads.
3. The temperature of gases supplied to the turbine is limited to 1100 K as there are no metals which can be used for blades to sustain this temperature at high centrifugal stresses.
4. The manufacturing of blades is difficult and costly as Ni-Cr alloy is used.
5. The control of fuel is difficult with wide operating speeds and output.
6. A special cooling system is required for the blades.
7. The starting is more difficult than IC engines.
8. It produces five times exhaust gases than an IC engine for same output.
9. Speed reduction device is always required due to higher operating speed.
10. The life of blades and combustion chamber is low due to high temperature.