NASASpaceFlight.com Forum
General Discussion => Q&A Section => Topic started by: aero on 02/21/2014 06:44 pm
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Several questions.
I'm trying to model the SpaceX Merlin D engine gas generator. Can anyone answer these questions in general?
1 - How much pressure beyond the combustion chamber pressure (9.7 MPa) is needed for injector performance?
2 - What is a good, conservative efficiency for the turbo pumps? I am using 0.8 for both the LOX and RP-1 pumps but they are probably not equally efficient.
3 - What is a good, conservative efficiency for the gas turbine? I am using about 0.394, is that to high? (It's a single shaft system.)
4 - What is a realistic number for the turbine blade temperature? I'm using 1000 deg. C but wonder if that is to low.
Thanks for any help.
aero
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You can look for the Markusic Propulsion presentation (PDF) (http://images.spaceref.com/news/2010/SpaceX_Propulsion.pdf). There's a point scheme of the proposed Merlin 2. Merlin 1 has a chamber pressure of about 1,000psi, and 1D was supposedly 1,400psi. Big TP like the Merlin 2 would be more efficient. But is not a bad starting point.
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Couple links that maybe of interest:
http://www.space-propulsion.info/resources/articles/AIAA-2005-3946.pdf
http://ftp.rta.nato.int/public/PubFullText/RTO/EN/RTO-EN-AVT-150/EN-AVT-150-06.pdf
1 - Sutton puts injector pressure drop at 15-25% of chamber pressure. IIRC coolant channel pressure drop is in the same ballpark.
4 - 1000C sound too high .. most numbers been around 800-1000K.
The latest RPA (http://www.propulsion-analysis.com/) has tools for turbopump and cooling characteristics computations.
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R7: Thanks for those links. I just had Sutton to date. I like reading the same stuff by different authors. Sometimes author #1 glosses over a 'basic' something that the amateur needs to know, but author #2 does not.
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I just had Sutton to date. I like reading the same stuff by different authors.
Then NASA SP-125 Huzel & Huang - Design of Liquid Propellant Rocket Engines (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710019929.pdf) is a must have too. Better turbopump section than Sutton.