Thanks all for the responses. I realized this is a bit of a subjective exercise
but I wanted to just make sure my assumptions weren't way out of bounds and it
sounds like they weren't. I also did find a few other instances of projects
posted online in addition to Bob's comments below and it seems like most are
using a higher contraction ratio to get a short/fat chamber. At first I was a
bit worried that this would not provide enough particle stay-time but it sounds
like this is not the case.
From: Robert Watzlavick <rocket@xxxxxxxxxxxxxx>
To: arocket@xxxxxxxxxxxxx
Sent: Friday, November 11, 2016 9:27 PM
Subject: [AR] Re: Contraction Ratio and Characteristic Length Estimates for a
500 lbf Engine
That seems reasonable to me. For my 250 lbf 250 psia LOX/Kerosene engine, I
used an L* of 40. The throat diameter was 0.94 inches, the contraction ration
was 8, and the chamber length was 4.2 inches. Note that I monkeyed around with
the numbers to get something that I thought I could build on my existing
equipment. For example, I didn't feel comfortable drilling the cooling holes
much more than 4 inches deep. And I wanted the OD of the engine (including the
injector flange) to be less than 5 inches.
-Bob
