CRITICAL PRESSURE RATIO

From Eq. (6.4), we have

The mass flow rate per unit area is maximum at the throat because it has minimum area of cross-section. Therefore,  will be maximum when  is maximum

Equation (6.5) gives the critical pressure ratio at which the discharge through the nozzle is maximum.

Substituting for  from Eq. (6.5), we get

where c_s2 = velocity of sound at exit of the nozzle.

where c_s1 = velocity of sound at entry of nozzle.