Hi guys, newbie Dave here, I just introduced myself over in the introductions sticky about how to improve the website. I've downloaded RJSC from Glenn Olson's website, and it seems really cool. The only problem is that I can't find any sort of documentation about it, so I don't know how to determine most of the parameters that need to be filled in. Is there a help file I overlooked? Even a Google search for the terms along with "ramjet" turns up nothing. Any help? I've seen a couple of people reference it and talk about it like it's dead obvious...
Another slightly less important question about it relates to fuels. It seems to only include jet fuels that the amateur is going to have a tough time dealing with. Does anyone know if there is a config file or something where we might enter the data for different fuels?
Thanks guys!
how to use RJSC?
Moderator: Mike Everman
jet fuel
Welcome!
I'm not familiar with the RJSC so I can offer no help there. As for "jet fuel" RP1 and RP5 are two very common "jet fuels" that I know about and they are just kerosene at different levels of refinement and levels of contaminates. You can get away with using straight kerosene as jet fuel and see almost no difference in performance when it comes to things like a ramjet.
-Aaron
I'm not familiar with the RJSC so I can offer no help there. As for "jet fuel" RP1 and RP5 are two very common "jet fuels" that I know about and they are just kerosene at different levels of refinement and levels of contaminates. You can get away with using straight kerosene as jet fuel and see almost no difference in performance when it comes to things like a ramjet.
-Aaron
-
dgsharp
- Posts: 12
- Joined: Sat Nov 24, 2007 3:14 am
- Antipspambot question: 0
- Location: Audubon, NJ, USA
- Contact:
Re: how to use RJSC
I emailed Glenn and asked him the same question, and hopefully he won't mind that I am re-posting the relevant parts of his reply. This seems like a good start. If anyone has anything to add to it that would be much appreciated. I'll list out the remaining parameters that I don't think are explained so far:
- Combustor Exit, nk (greek letters, eta kappa). Default = 0.98. I'm guessing this one has something to do with turbulence and/or Reynolds numbers from a Google search, but can't make out what exactly.
- Capture Area, nke (actually greek letters, eta kappa epsilon). Default = 0.92. Same deal as above, maybe something to do with turbulence or Reynolds numbers...
- Nozzle, nN (greek letters, eta capital-nu). Default = 0.975
Under the Throat tab there is parameter A*, but it has a tool tip which says "A8 or A*", so presumably it represents the area of the nozzle. Anybody care to suggest how to get values to put in for the 3 unknown parameters? I guess I'll just use the defaults for now...
The relevant parts of Glenn's message follow:
--------------------------
Take a look at this NASA page which shows the stations and a simplified description of what the station number are.
http://www.grc.nasa.gov/WWW/K-12/airplane/turbdraw.html
Now, if I remember this right, the "A" is used by engineers to specify the area at a specific location as opposed to an engine component. They also may use either additional numbers or letters to describe a more specific location inside that component. For example, station 2 is the compressor in a turbine engine. A2 would describe the area at the beginning of station 2. A21 may be at the low-pressure compresser discharge but it may be described as A2a or A25 or some other designation the engineer or company chooses. But station 2 will always designate the compressor section. P2 would be the pressure at the beginning of station 2. C2 would be the flow velocity. T2 would be the temperature.
Station 8 is the exhaust nozzle throat while station 9 is the exhaust nozzle exit. The NASA page shows only a converging nozzle and therefore 8 and 9 are the same. For a converging/diverging nozzle they would be different.
For a ramjet (again, if I remember it right) not all engine station numbers are used because not all of the components are there, but the ones used are consistent with turbine engines. I hope this helps.
The book I refer to on engines is "Jet Engines, Fundamentals of Theory, Design and Operation," by Klaus Hunecke, Motorbooks International, 1997. It has some engineering but also a lot of good narrative description to make it understandable. It describes the turbine engine then goes through each section and includes different variations and lots of drawings, charts, and pictures.
- Combustor Exit, nk (greek letters, eta kappa). Default = 0.98. I'm guessing this one has something to do with turbulence and/or Reynolds numbers from a Google search, but can't make out what exactly.
- Capture Area, nke (actually greek letters, eta kappa epsilon). Default = 0.92. Same deal as above, maybe something to do with turbulence or Reynolds numbers...
- Nozzle, nN (greek letters, eta capital-nu). Default = 0.975
Under the Throat tab there is parameter A*, but it has a tool tip which says "A8 or A*", so presumably it represents the area of the nozzle. Anybody care to suggest how to get values to put in for the 3 unknown parameters? I guess I'll just use the defaults for now...
The relevant parts of Glenn's message follow:
--------------------------
Take a look at this NASA page which shows the stations and a simplified description of what the station number are.
http://www.grc.nasa.gov/WWW/K-12/airplane/turbdraw.html
Now, if I remember this right, the "A" is used by engineers to specify the area at a specific location as opposed to an engine component. They also may use either additional numbers or letters to describe a more specific location inside that component. For example, station 2 is the compressor in a turbine engine. A2 would describe the area at the beginning of station 2. A21 may be at the low-pressure compresser discharge but it may be described as A2a or A25 or some other designation the engineer or company chooses. But station 2 will always designate the compressor section. P2 would be the pressure at the beginning of station 2. C2 would be the flow velocity. T2 would be the temperature.
Station 8 is the exhaust nozzle throat while station 9 is the exhaust nozzle exit. The NASA page shows only a converging nozzle and therefore 8 and 9 are the same. For a converging/diverging nozzle they would be different.
For a ramjet (again, if I remember it right) not all engine station numbers are used because not all of the components are there, but the ones used are consistent with turbine engines. I hope this helps.
The book I refer to on engines is "Jet Engines, Fundamentals of Theory, Design and Operation," by Klaus Hunecke, Motorbooks International, 1997. It has some engineering but also a lot of good narrative description to make it understandable. It describes the turbine engine then goes through each section and includes different variations and lots of drawings, charts, and pictures.
ramjet stages
I ran across the NASA engine simulator before and it might be something you want to play with
http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html
(select ramjet on the top, then you can tweak the settings for a ramjet)
There is also basic design layout and the formulas needed to calculate thrust.
http://www.grc.nasa.gov/WWW/K-12/airplane/ramth.html
For some reason the unknown parameters seem to be pressure corrections to me. I seem to remember reading about them but I can't for the life of me remember where.
-Aaron
http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html
(select ramjet on the top, then you can tweak the settings for a ramjet)
There is also basic design layout and the formulas needed to calculate thrust.
http://www.grc.nasa.gov/WWW/K-12/airplane/ramth.html
For some reason the unknown parameters seem to be pressure corrections to me. I seem to remember reading about them but I can't for the life of me remember where.
-Aaron
-
Glenn Olson
- Posts: 16
- Joined: Fri Oct 10, 2003 2:25 am
- Antipspambot question: 0
- Location: US-California
- Contact:
I received RJSC as is, with no documentation. As I recall it was written for college engineers who already knew what everything was. When I posted it I didn't think to write up any documentation, though I think I was in a hurry at the time.
Anyway, here are a few quick notes.
1. I really don't recall what RJ-5 is but the other two are basically kerosene.
2. Freestream, A0, means the air conditions ahead of the vehicle. These are apparently taken from the atmosphere model for the altitude, A0.
3. The Capture Area, A1, is the inlet area subtracting for the inlet cone.
4. The Inlet, A2, is the total inlet area.
5. Use the same Capture Area for the Throat, A*.
6. For ramjets the Combustor Entrance, A3, is typically the same as the Combustor Exit, A4. Just use your combustion chamber cross sectional area.
7. Flameholder, A2a is the area of the flameholder. For example, if your flameholder is a square plate 4 inches on a side then the area is 16 square-inches. In the picture these are the "less than" symbols. Because it's part of the combustion chamber it probably should have been named A3b or A4a or something like that rather than A2a. The programmer was probably not an engine guy.
8. The Throat, A*, is the narrowest (pinch) part of the exhaust nozzle.
9. Nozzle, A9, is the area at the very tail end of the exhaust nozzle.
Hope that helps. The model I've used most is one I can't give you. It's older, DOS-based, and makes you specify many more parameters, and interpret a lot more. I haven't played with this one much but it's authorized for public distribution. I don't remember how this one reacts to subsonic flight but you can play with it and see what it does.
Anyway, here are a few quick notes.
1. I really don't recall what RJ-5 is but the other two are basically kerosene.
2. Freestream, A0, means the air conditions ahead of the vehicle. These are apparently taken from the atmosphere model for the altitude, A0.
3. The Capture Area, A1, is the inlet area subtracting for the inlet cone.
4. The Inlet, A2, is the total inlet area.
5. Use the same Capture Area for the Throat, A*.
6. For ramjets the Combustor Entrance, A3, is typically the same as the Combustor Exit, A4. Just use your combustion chamber cross sectional area.
7. Flameholder, A2a is the area of the flameholder. For example, if your flameholder is a square plate 4 inches on a side then the area is 16 square-inches. In the picture these are the "less than" symbols. Because it's part of the combustion chamber it probably should have been named A3b or A4a or something like that rather than A2a. The programmer was probably not an engine guy.
8. The Throat, A*, is the narrowest (pinch) part of the exhaust nozzle.
9. Nozzle, A9, is the area at the very tail end of the exhaust nozzle.
Hope that helps. The model I've used most is one I can't give you. It's older, DOS-based, and makes you specify many more parameters, and interpret a lot more. I haven't played with this one much but it's authorized for public distribution. I don't remember how this one reacts to subsonic flight but you can play with it and see what it does.