Hi -
I was reading through the heat transfer / cooling sections in Huzel and Huang
and I wanted to ask two questions, which I’m struggling a bit with:
- Huzel and Huang (Fig 4-29 and equation 4-18) p87
https://books.google.com/books?id=TKdIbLX51NQC&lpg=PA86&ots=slcX6Gcpta&dq=thermal%20resistance%20of%20carbon%20deposits&pg=PA87#v=onepage&q=thermal%20resistance%20of%20carbon%20deposits&f=false
discusses adjusting the gas side heat transfer coefficient based on thermal
deposits for hydrocarbon fuels such as RP-1. The units they use to describe for
thermal deposits are in2*sec*oR/Btu. I would like to translate this into the
units used by RPA mainly W/m*K and thickness of deposits mm. Unfortunately, I’m
not familiar enough with the Imperial units convention used in this book or how
to convert them to metric thermal and thickness.
- Also in Huzel & Huang p100 & p101
https://books.google.com/books?id=TKdIbLX51NQC&lpg=PA100&ots=slcX6Kfrx6&dq=mixture-ratio%20bias&pg=PA100#v=onepage&q=mixture-ratio%20bias&f=false
there is an interesting section on Mixture-Ratio Bias. In short it talks about
changing the mixture ratio in the outer ring of injectors to be fuel rich (as
opposed to doing more traditional film cooling) and notes that it leads to a
very significant decrease in heat flux with no noticeable drop in performance.
In regards to #2, I’m working on a LOX/Kerosene 500 lbf engine running at a
1.8:1 mixture ratio and I’m very tempted to try this but I wanted to see if
anyone has experience or advice with this? I'm not sure that I recall anyone on
Arocket who mentioned using this injector patter but it seems like it could be
quite beneficial. Essentially, what I was thinking of doing is as follows:
Inner Injector Rings:
60% Kerosene Flow / 70% LOX = 2.1:1 mixture ratio
Either unlike triplet or like doublet configuration
Outer Injector Ring:
40% Kerosene Flow / 30% LOX = 1.35:1 mixture Ratio
Unlike doublet configuration
Kind Regards,Graham
