Mass flow rate through De Laval Nozzle

In summary, the conversation is about a person seeking help with calculating the mass flow rate of a choked flow through a de laval nozzle. They have been given data and equations to use, but their theoretical and experimental results are significantly different. After further investigation, they discovered their error and were able to fix it, but expressed disappointment in not receiving any help from others.
  • #1
darksupernova
2
0
Hey guys,


Ive got a little stuck calculating the mass flow rate of a choked flow through a de laval nozzle.

I have been given a formula to use for theoretical max and experimental but they seem to be SO far apart, I am sure I am missing something.

Given data:

Density of water 1000 kg/m^3
Throat diameter (nozzle) 4.79mm
Exit diameter (nozzle) 5.54mm
Probe diameter 3.30mm
Coefficient of discharge of orifice plate 0.6
orifice diameter 27.03mm
pipe diameter 76.2mm
gamma ratio of specific heats 1.4
gas constant 287 J/(kg K)
Absolute zero 273 degrees c / 0 K
Delta H = 2" = 0.0508m

See useful equations in attached image.

The manometer had water in it, and thus rho g H uses water density and delta H as above.

Please also see my attempt in the attached images for the theoretical and experimental equations.

The problem, they seem to be miles apart, am I using the correct diameters?

What am I getting wrong?

I hope you can help!

Thanks,

Max
 

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  • #2
Update: I found the error. For p1-p2 I had the pressure difference in Pascals when of course the difference would be in Kilo Pascals, this unit change fixed the errors and gave me sensible answers. Little sad that nobody on here was any help! :(

Also I cannot see how to mark this thread as [Solved], it won't let me edit my original post.
 

1. What is a De Laval nozzle?

A De Laval nozzle is a type of nozzle used in rocket engines and supersonic aircrafts to accelerate the flow of gases to supersonic speeds.

2. How does a De Laval nozzle work?

A De Laval nozzle works by converting the thermal energy of gases into kinetic energy. The nozzle has a convergent section, where the gases are compressed and their velocity increases, and a divergent section, where the gases expand and accelerate to supersonic speeds.

3. What is the importance of mass flow rate in a De Laval nozzle?

The mass flow rate is the amount of gas passing through the nozzle per unit time. In a De Laval nozzle, it is important to maintain a high mass flow rate to achieve efficient propulsion and achieve the desired thrust.

4. How is the mass flow rate through a De Laval nozzle calculated?

The mass flow rate through a De Laval nozzle can be calculated using the equation: m = ρ * A * V, where m is the mass flow rate, ρ is the density of the gas, A is the cross-sectional area of the nozzle, and V is the velocity of the gas.

5. How can the mass flow rate through a De Laval nozzle be controlled?

The mass flow rate through a De Laval nozzle can be controlled by adjusting the pressure and temperature of the gases entering the nozzle, as well as the size and shape of the nozzle itself. By controlling these factors, the mass flow rate can be optimized for efficient propulsion.

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