Graham,
That does make a lot of sense now. What I was missing was that your percentages
were of the total oxidizer flow and total fuel flow, respectively, rather than
the percentages of (fuel + oxidizer) flow through a given set of injectors.
Your approach makes sense to me, but take that with a grain of salt, as I
haven't personally done any liquids work yet. My personal experience is all
solids and nitrous hybrids at this point.
However, my physical intuition says this passes the sniff test, and I suspect
it'd be worth trying, so as to get some hard data.
Cheers,
Rick Dickinson
On November 26, 2016 10:21:26 AM PST, Graham Sortino
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
Hi Rick-
Apologies, I may have made a mistake. Let me use the actual mass flow
numbers for my design and I'll try to illustrate:Total Ox Flow = 0.5709
kg/sec
Total Fuel Flow = 0.3172 kg/secTarget Mixture Ratio ~= 1.8:1 O/F
Now, what I was proposing is having an inner core of injection orifices
where the mixture ratio is slightly higher. This would be approximately
2.1:1 O/F.Inner Core Ox Flow = 70% of 0.5709 or 0.3996 kg/secInner Core
Fuel Flow = 60% of 0.3172 or 0.1903 kg/secInner Core Mixture Ratio =
0.3996 / 0.1903 ~= 2.1 O/F
Then there would be an outer core closer to the chamber walls that is
fuel rich in order to reduce the adiabatic combustion gas temp near the
wall as well as gas side heat transfer. This would be approximately
1.35 O/FOuter Ox Flow = 30% of 0.5709 or 0.1713 kg/secOuter Fuel Flow =
40% of 0.3172 kg/sec or 0.1269 kg/secOuter Mixture Ratio = 0.1713 /
0.1269 ~= 1.35 O/F
If I add up the Fuel and Oxidizer flows I *believe* the total O/F ratio
is the same but the lower mixture ratio toward the walls could (might)
theoretically help more with cooling without the subsequent reduction
in performance caused by more traditional film cooling.(Recalculated)
Total Ox Flow = 0.3996 + 0.1713 = 0.5709 kg/sec(Recalculated) Total
Fuel Flow = 0.19032 + 0.1269 = 0.3172 kg/sec(Recalculated) Mixture
Ratio = 0.5709 / 0.3172 ~= 1.8:1 0/F
Kind Regards,Graham
On Saturday, November 26, 2016, 12:07:08 PM EST, Rick Dickinson
<rtd@xxxxxxxxxxxx> wrote:Graham,
Your numbers don't seem to add up to 100% for either the inner or outer
injectors, so I'm a little bit confused by what you're asking, and how
you got from those percentages to your mixture ratios. Can you clarify
a bit, please?
Thanks,
Rick "confused" Dickinson
On November 26, 2016 8:47:00 AM PST, Graham Sortino
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
Hi -and
I was reading through the heat transfer / cooling sections in Huzel
Huang and I wanted to ask two questions, which I’m struggling a bit
with:
[Snip]
In regards to #2, I’m working on a LOX/Kerosene 500 lbf engine runningbut
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
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
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
