ENH: Enable only radial burning #801
Comments
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does it happen with every hybrid motor? |
I can't ensure you that it happens to every hybrid motor. It's a model, as the combustion happens in the boundary layer between the liquid oxidizer and the solid fuel, the hypothesis is that the reaction is much more prominent in the port, where the burn is axial, because of the stronger oxidizer flow velocity, while the reaction in the bases of the grain are negligible. But this model is based on the source below, which is largely cited, including in NASA SP7002-02. |
only_radial_burn optional parameter added and used in the functions related to the grain regression as a conditon to change the applied equations. Still need to update the comment section, the CHANGELOG and maybe the dict related functions, but not sure about the last one yet.
The new parameter of the SolidMotor class was removed from super, since it's not on the Motor class. The dict functions were updated to take this new parameter into acount. Also the comments about the SolidMotor class parameters were updated. Still need to do some tests running the code to be sure everything is ok, then I can open the PR.
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I runned some sanity check tests, just to see if the physical behaviour is correct, I used the motor Pro75M1670, defined in the getting started file.
The results are coherent since
I will keep trying to interpret the results and correct the physical behaviour. |
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Discovered the error, I forgot to change the grain_height_derivative, so, besides all te calculations were being done with only the port area, the height was still being consumed.
Now I just changed that and the behaviour is correct, so I will open the PR.
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Corrected some minor code erros, like calling evaluate geometry before defining self.only_radial_burn. Also had to change the grain_height_derivative to zero in the case of only radial burn, it was leading to some physical incoherences, because the grain was still burning axially. The last tests to evaluate the physical behaviour went pretty well, so I'll open the PR.
The "only_radial_burning" parameter was added and set as default on the hybrid class. Also, the description of the new parameter was updated and 2 coments about derivatives set to zero were added.
Is your feature request related to a problem? Please describe.
Rocketpy SolidMotor class only simulates radial and axial simoultaneos burn, but the regression rate on hybrid motor are modeled to be a function of the oxidizer mass flux entering the grain, so it only takes into consideration the radial burn.
Describe the solution you'd like
The idea is to implement the option to simulate only radial burn for the cases of a axially inhibited grain or hybrid motors.
Additional context
Heeg, F., Kilzer, L., Seitz, R., & Stoll, E. (05 2020). Design and Test of a Student Hybrid Rocket Engine with an External Carbon Fiber Composite Structure. Aerospace, 7, 57. doi:10.3390/aerospace7050057
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