Friday, May 22, 2009

Rocket Propellant Injection

Here are some tables with calculations for propane and oxygen. I think if you are going to do something like this, propane is what you want to use. It has a huge liquid range, and so can be subcooled very deeply. Oxygen is the most likely oxidizer - but note that it is far less useful, because of it's narrower liquid range.

Perhaps the best option would be propane and hydrogen peroxide - though peroxide has it's own issues, and a peroxide injector could be quite dangerous!

Anyway, the key to good injection is subcooling! (Well, don't superheat the steam too far either - you want it to exit the nozzle just above boiling.)




















































































































Substance Propane Propane Propane Propane
Gas Heat Capacity 1.67 1.67 1.67 1.67
Liquid Heat Capacity 2.23 2.23 2.23 2.23
Latent heat of evaporation 425 425 425 425
Boiling point (C ) -42.1 -42.1 -42.1 -42.1





Gas Velocity (m/s) 300 300 300 600
Gas Temperature (C ) 0 0 0 0





Liquid Temperature (C ) -180 -180 -180 -180
Liquid Density (kg/m3) 582 582 582 582
Mass Mixture Ratio 0.9 0.8 0.55 0.55





Mixed velocity (m/s) 30 60 135 270
Mixed temperature (C ) -146.23 -116.89 -62.99 -62.99
Stopped Pressure (Atm) 2.59 10.37 52.51 210.04





















































































































Substance Oxygen Oxygen Oxygen Oxygen
Gas Heat Capacity 1.84 1.84 1.84 1.84
Liquid Heat Capacity 2 2 2 2
Latent heat of evaporation 426.25 426.25 426.25 426.25
Boiling point (C ) -182.95 -182.95 -182.95 -182.95





Gas Velocity (m/s) 300 300 600 1200
Gas Temperature (C ) -150 -180 -180 -180





Liquid Temperature (C ) -215 -215 -215 -215
Liquid Density (kg/m3) 1140 1140 1140 1140
Mass Mixture Ratio 0.9 0.85 0.85 0.85





Mixed velocity (m/s) 30 45 90 180
Mixed temperature (C ) -189.89 -182.67 -182.67 -182.67
Stopped Pressure (Atm) 5.08 11.43 45.71 182.85

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