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The mass flow through a convergent – divergent nozzle is maximum when the pressure at:

The mass flow through a convergent – divergent nozzle is maximum when the pressure at: Correct Answer Throat is equal to the critical pressure

Concept:

  • Convergent - Divergent nozzles are used to increase the flow of gas to supersonic speeds (as in the case of rockets).
  • Their cross-sectional area first decreases and then increases. The area where the diameter is minimum is called the throat.
  • As the gas enters the converging section, its velocity increases, considering the mass flow rate to be constant.
  • As the gas passes through the throat, it attains sonic velocity (Mach number = 1).
  • As the gas passes through the divergent nozzle, the velocity increases to supersonic (Mach number >1)
  • The flow rate is maximum for a given nozzle if the flow is sonic at the throat. This condition is achieved by managing the back pressure.
  • For the compressible fluid flow, the Mach number is an important dimensionless parameter. On the basis of the Mach number, the flow is defined.

Important Points

Mach Number

Type of flow

M < 0.8

Sub-sonic flow

0.8 < M <1.3

Trans-sonic

M = 1

Sonic flow

1.3 < M < 5

Super-sonic flow

M > 5

Hypersonic flow

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