Choked Mass Flow Rate Calculator

Formula Used:

\[ \text{Choked Mass Flow Rate} = \frac{\text{Mass Flow Rate} \times \sqrt{\text{Specific Heat Capacity at Constant Pressure} \times \text{Temperature}}}{\text{Nozzle Throat Area} \times \text{Throat Pressure}} \]

Mass Flow Rate (m):

kg/s

Specific Heat Capacity at Constant Pressure (Cp):

J/kg·K

Temperature (T):

Nozzle Throat Area (Athroat):

m²

Throat Pressure (Po):

Choked Mass Flow Rate:

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1. What is Choked Mass Flow Rate?

Choked Mass Flow Rate refers to the maximum mass flow rate of a compressible fluid through a restricted flow area, reaching the critical sonic conditions. This occurs when the fluid velocity at the throat of a nozzle reaches the speed of sound.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

Mass Flow Rate — Mass passing through a cross-section per unit time (kg/s)
Specific Heat Capacity at Constant Pressure — Amount of heat required to raise temperature of a unit mass of gas by 1 degree at constant pressure (J/kg·K)
Temperature — Degree or intensity of heat present in a substance (K)
Nozzle Throat Area — Area of cross section at the throat of nozzle (m²)
Throat Pressure — Discharge pressure of an engine at a given mass flow rate through the throat of the nozzle (Pa)

Explanation: This formula calculates the maximum mass flow rate that can pass through a nozzle when the flow becomes choked (sonic conditions at the throat).

3. Importance of Choked Mass Flow Rate Calculation

Details: Accurate calculation of choked mass flow rate is crucial for designing and analyzing nozzle performance in various engineering applications, including rocket engines, gas turbines, and other propulsion systems where compressible flow occurs.

4. Using the Calculator

Tips: Enter all values in the appropriate units. Mass flow rate in kg/s, specific heat capacity in J/kg·K, temperature in Kelvin, nozzle throat area in m², and throat pressure in Pascals. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What does "choked flow" mean?
A: Choked flow occurs when the fluid velocity at the throat of a nozzle reaches the speed of sound, preventing any further increase in mass flow rate regardless of downstream pressure changes.

Q2: When does choked flow occur?
A: Choked flow occurs when the pressure ratio across the nozzle exceeds a critical value, typically around 1.893 for ideal gases with specific heat ratio of 1.4.

Q3: What are typical applications of this calculation?
A: This calculation is essential in rocket propulsion, jet engines, gas turbine design, and any system involving compressible fluid flow through nozzles or orifices.

Q4: How does temperature affect choked mass flow rate?
A: Higher temperatures generally increase choked mass flow rate due to the square root relationship in the numerator of the equation.

Q5: What are the limitations of this formula?
A: This formula assumes ideal gas behavior, isentropic flow, and perfect nozzle geometry. Real-world applications may require additional corrections for friction, heat transfer, and non-ideal gas effects.