Question

Question2 a. Referring to the effect on the thermodynamic cycle, explain how bleeding of air to cool turbine blades leads to improvement in engine performance, despite the fact that such bleed air undergoes minimal momentum change and thus contributes negligible thrust. A turbojet engine flies at Mach 2, and 60,000ft, whe the airflow is bled from the high pressure end of the compressor, which has a pressure ratio of 8:1. This bleed air is used to cool the turbine blades so that the turbine inlet temperature is allowed to be as high as 1700 K. The bleed air is exhausted at the same velocity with which it entered the engine. Determine: b. the ambient temperature is 217 K. 10% of i. Specific thrust ii. Thrust specific fuel consumption iii. ηΡ,nth and no For simplicity assume all components to be reversible and p, Pa. QR Note: Before combustion,仁1.4 and Cp-1.0 k/kgK. During and after combustion, cp 1.1 k/kgK. 1.35 and

Answer 1

A turbine blade is an individual component which makes up the turbine section of the gas turbine or steam turbine. The blades are responsible for extracting energy from high temperature , high pressure produced by compressor. Blade fatigue is a major source of failure in steam turbine. Fatigue is caused by stress, vibration, high temperature.

At a constant pressure ratio, thermal efficiency increases as the maximum temperature increases. But, high temperature can damage blades as they are under large centrifugal stresses and material are weaker at high temperature.

Bleed air is compressed air taken from the compressor stage of a turbine upstream of it's fuel burning section. ASCPCs Automatic air supply and cabin pressure controller valves bleeds air from high or low stage engine compressor.

So that's how bleed air system for cooling of blades works, and how it effects turbine performance.

sivelocit

age No. Es

1). Fuel consumption for turbines and jets are generally represented in terms of T.S.F.C (Thrust specific fuel consumption).

2). The thrust specific fuel consumption varies with R.P.M of engine.