# Air standard cycle: Definition, Efficiency, Assumptions, Difference [with Pdf]

Contents

## What is Air standard cycle?

1] The air standard cycle is a thermodynamic power cycle that converts heat energy into mechanical power by considering air as a working fluid with constant specific heats (Cp & Cv).

2] In this cycle, the air is the only working fluid that goes through changes in its thermodynamic properties to convert heat into mechanical power.

3] In this cycle, there is no internal energy generation by means of burning any fuel inside of the engine.

4] The heat is extremely added by means of a heat exchanger & also it is rejected by using heat exchange to the sink.

5] It is consists of a non-flow process. It means that a certain amount of air is continuously performing successive cycles. No intake or exhaust of air is permitted into the cycle.

6] Hence it works as a closed cycle with no mass transfer. Working fluid air is considered an ideal gas with constant specific heat.

7] Following are examples of air standard cycle:-

## Air standard cycle assumptions:

The Air standard cycle assumptions are as follows:-

• Air is considered as working fluid.
• Air has constant specific heat.
• Air behave as ideal gas.
• All processes in cycle as internally reversible.
• For air Change in K.E.= 0, Change in P.E.= 0
• No internal heat generation.
• heat is added & rejected externally.
• The cycle is closed & processes are non-flow processes.
• There is no frictional losses.

## Important formulae:

1] Thermal efficiency:-

Air standard cycle thermal efficiency is given by

eta _{th}= frac{W_{Net}}{Q_{s}}

Where
W_{Net} = Net work = W_{\text{Turbine}}-W_{\text{compressor}}
Q_{s} = Heat supplied

2] Net work ratio (WR_{Net}):-

It is given by,

WR_{Net}=frac{W_{Net}}{W_{\text{Turbine}}}

WR_{Net} = frac{W_{\text{Turbine}}-W_{\text{compressor}}}{W_{\text{Turbine}}}

WR_{Net}=1-frac{W_{\text{compressor}}}{W_{\text{Turbine}}}

3] Back work ratio:-

It is given by,

WR_{Back}=frac{W_{\text{compressor}}}{W_{\text{Turbine}}}