Does anyone have any information about the effect of rocket spin/roll on the flow rate of N2O in a hybrid motor? Intuitively you would expect the induced outward radial force in the N2O tank to affect the axial flow through the injector.
Flow rate of N2O in hybrid
- Thread starter Voyager1
- Start date
I think you'll be heading into a subject area that will get relegated to the research forum, which is not publically accessible. Discussion of details of motor design have been discouraged in this forum many times. I had to move my stuff there, for instance.
Sorry.
Gerald
PS - Short answer, radial and axial accelerations would affect liquid vs gas pickup opportunity, and flow rates through the injectors, if system is based on pressure differential.
Sorry.
Gerald
PS - Short answer, radial and axial accelerations would affect liquid vs gas pickup opportunity, and flow rates through the injectors, if system is based on pressure differential.
Thanks Gerald. We'll see what the moderators think.
- Joined
- Jan 23, 2009
- Messages
- 5,537
- Reaction score
- 3,521
The flow rate though the injectors is only a function of the delta P between the tank and the combustion chamber, the flow resistance of the injector and the Reynolds number for the flow which will have a density term in it.
Spin would not affect any of those parameters except maybe for density at the injector if the spin were very high or the radius of the tank was large. However I do not think the wr of hobby type hybrid motors would be large enough to generate any significant vapor/liquid radial density gradient.
Spin would not affect any of those parameters except maybe for density at the injector if the spin were very high or the radius of the tank was large. However I do not think the wr of hobby type hybrid motors would be large enough to generate any significant vapor/liquid radial density gradient.
Thanks very much for that information John. I haven't had any concerns about it, it was just a question that a fellow club member asked me recently and I had no answer for him.
John
John
The pressure at the injector consists of the vapor pressure and what could be called "hydrostatic pressure" or "inertial pressure". I'm not sure if either term in quotes is a good choice in a spinning rocket. The pressure is dominated by the vapor pressure, which is independent of spin rate. The "hydrostatic pressure" depends on the fill height of the tank, density and acceleration. This component of tank pressure, or its distribution, is affected by spin, although the absolute value is comparable small to the vapor pressure, unless the tank is quite long and the rocket accelerates violently. It would require something like a tank filled to 10m above the injector accelerating at 50g to match the vapor pressure. I'm not aware of any existing liquid or hybrid rockets that come close to that length x acceleration product.
However, it is possible to starve the injector when the rocket spins. In this case it will only receive gas, albeit still at a high pressure, while there is still some liquid remaining in the tank. The formula to describe the surface of the fluid can be found here:
https://physics.stackexchange.com/questions/293106/shape-of-water-in-rotating-bucket
Substitute the actual acceleration of the rocket instead of g to get to the right shape.
Reinhard
However, it is possible to starve the injector when the rocket spins. In this case it will only receive gas, albeit still at a high pressure, while there is still some liquid remaining in the tank. The formula to describe the surface of the fluid can be found here:
https://physics.stackexchange.com/questions/293106/shape-of-water-in-rotating-bucket
Substitute the actual acceleration of the rocket instead of g to get to the right shape.
Reinhard
Similar threads
