LRE Project - 10/17/2021

Its been a while but I'm back to working this for a bit. Had to take some time for work, life, going to weddings, traveling, etc.

In the interim I have worked a few things on my list. From where I left off the open areas I was hoping to work on were:

• A literature review to determine if chamber sizing looked reasonable from a Lc/Dc standpoint
• Literature review of injector designs used with this combo
• Work to baseline test setup on the side
• size tank volumes
• draft a Plumbing and Instrumentation Diagram (P&ID, etc) for the test setup and engine

So starting from the top of the list, after reviewing some papers (I'll add a references page to the blog that I'll be recording papers I'm gathering during the project), I've determined that the L* used and Lc/Dc ratio the engine falls in isn't unusual for LOX/Ethanol. Though with taxes on the ethanol and not wanting to deal with denatured, etc I've decided just to switch to Kerosene, I'm baselining Jet A as I've had good experience acquiring at the local general aviation airport/FBO and heating Kerosene is oddly hard to come by in very warm sunny Florida.

The next item on the list is injector design. This is an area I am not all too versed in so its probably going to be a bit iterative to get this right. First thing is to review what others have implemented and the ease of manufacturing of each design. I'm heading down an impinging doublet style for now, with the oxidizer centered in the injector (green section) and the fuel orifices surrounding (red section). Playing with number of elements and angles to get reasonable quantity for good spread of the propellant while also while biasing towards residual momentum pointing towards the centerline of the engine and away from the wall. I ended up with 24 pairs of elements.

Additionally, I ended with an 18° angle for the Oxidizer orifices and a 42° angle for the Fuel Orifices

Chamber and cooling design is going to be rather simple with boundary layer cooling at the injector around the diameter of the chamber with a heatsink design/operation. If you want to see the direct numbers from the sizing they are below:

Hopefully next entry I can take a little longer actually discussing the math behind all this but as of this entry its a little too late to dig into it.

For another item on my to-do list was to start drafting up a quick Plumbing and Instrumentation Diagram (P&ID) for the test setup. So for this setup I plan to integrate the engine and test tankage in a a way that will emulate integrating it into a singular package for a flight. The nitrogen for blowdown will be provided by a regulated blowdown tank and this will also supply pneumatics for the single run valve for the engine. I'll have a backup source checked off just in case the pneumatics droop on the tank but should allow for the whole system to be tested as a unit. There will be additional facility systems upstream of these lines but wanted to get the concept of the engine/fluids package in a single P&ID.

Next update I want to give a more thorough dive into how I sized the injector as well as a better update on the engine CAD/Design. Currently I'm in sealing purgatory for the seals between injector and chamber but I'll have a workable solution by the next update. 

Additionally I'll start generating the P&ID for the facility plus a first scratch at tank sizing and line sizing for engine and facility.

Until next time, thanks for reading!