CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

Supersonic nozzle

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   May 16, 2005, 17:53
Default Supersonic nozzle
  #1
Danny Tan
Guest
 
Posts: n/a
Dear CFD people:

Is it possible to obtain uniform, isentropic, shock free flow through a minimum length nozzle (MLN), (the expansion section is eliminated) ?

I believe it is possible but..

My question is: If it is possible to obtain uniform, isentropic, shock free flow through MLN, why people want to design a long supersonic nozzle with gently curved expansion section.

Any comment is appreciated

Thank you

Danny
  Reply With Quote

Old   May 16, 2005, 18:29
Default Re: Supersonic nozzle
  #2
Mani
Guest
 
Posts: n/a
Theoretically, yes it's possible, neglecting viscous effects.

I think there are some practical issues with the expansion region. With the expansion concentrated on a single point (or curve), the wall of a MLN usually has a sharp edge, right at the throat, around which the flow accelerates from Mach 1 to the maximum Mach number.

One of the effects of viscosity could be flow separation at that edge. I am not sure if this is a big issue. It might not be, because of the acceleration.

Another problem is heat. In practice a perfectly sharp expansion edge (even if you could manufacture it) will be hard to maintain because of friction. Eventually the edge will burn off.

Anyhow, even though the exact MLN from inviscid theory may not be realistic, I am pretty sure that approximate MLNs (with very small expansion sections) are in use. How did you get the impression that this design is not used?
  Reply With Quote

Old   May 18, 2005, 05:09
Default Re: Supersonic nozzle
  #3
harish
Guest
 
Posts: n/a
Theoritically yes applying the 1-D isentropic relations you can define a back pressure at which the flow from the nozzle is supersonic. But in reality the effect of the boundary layer interaction plays the spoilsport.

-H
  Reply With Quote

Old   May 18, 2005, 13:52
Default Re: Supersonic nozzle
  #4
Pete
Guest
 
Posts: n/a
To get supersonic flow, the nozzle must have a expansion section, to allow the flow the expand from sonic to supersonic. Then the expansion section have to be extended further (with careful design) to absorb the expansion waves, and finally get a "uniform" flow. The design of the expansion section is crucial to the flow quality.

If you say there's a MLN, then, yes, there should be one based on inviscid assumption.

Hope this answers your question. Pete
  Reply With Quote

Old   May 19, 2005, 10:38
Default Re: Supersonic nozzle
  #5
Danny Tan
Guest
 
Posts: n/a
Thank you all for the responses.

Danny
  Reply With Quote

Old   April 14, 2009, 13:14
Default Axisymmetric Nozzle contour MOC
  #6
New Member
 
Logan Myers
Join Date: Apr 2009
Posts: 2
Rep Power: 0
logan is on a distinguished road
Hi,

Does anybody have a Matlab code for MOC contour design of an axisymmetric supersonic (Mach 2) nozzle they could send/sell me?

Thanks in advance,
Logan
logan is offline   Reply With Quote

Old   August 18, 2009, 04:14
Default
  #7
New Member
 
Dileep Mathews
Join Date: Aug 2009
Posts: 1
Rep Power: 0
kaleekal_dileep is on a distinguished road
Quote:
Originally Posted by Danny Tan
;34504
Dear CFD people:

Is it possible to obtain uniform, isentropic, shock free flow through a minimum length nozzle (MLN), (the expansion section is eliminated) ?

I believe it is possible but..

My question is: If it is possible to obtain uniform, isentropic, shock free flow through MLN, why people want to design a long supersonic nozzle with gently curved expansion section.

Any comment is appreciated

Thank you

Danny
i am searching for a code, to design supersonic nozzle .
kaleekal_dileep is offline   Reply With Quote

Old   August 18, 2009, 17:24
Default
  #8
New Member
 
Rich
Join Date: Aug 2009
Location: Montrose, Colorado, USA
Posts: 11
Rep Power: 7
Rich is on a distinguished road
Part of the issue is what you want to use the nozzle for. For a rocket nozzle, you want all of the gases moving the same direction (axially), to get maximum thrust. Early nozzles were conical (V-2, Redstone), and because some of the gases had a radial velocity component when leaving those nozzles, there was some degree of loss or inefficiency. If you wanted to, you could expand a gas through a simple orifice from high pressure directly to ambient, but the expansion fan at the exit will turn a great deal of the gas outward, radially, and hence, thrust is greatly reduced. To design a nozzle that directs all of the gases axially at the exit, the geometric angle of expansion at the throat can only be so large because the flow must be turned back onto itself without any shocks being generated. That takes a nozzle of finite length. Look for papers by G.V.R. Rao, who designed Rocketdyne's nozzles.

To my knowledge, the shortest nozzles ever developed are the "expansion-deflection" or "plug" nozzles. These were also developed by Rocketdyne (in fact they were even patented by Rocketdyne). Their Aerospike engine was just about as short as possible, and allowed for high efficiency even under highly off-design conditions. Pity NASA wasn't smart enough to employ those engines rather than the ones they ended up requiring for the Space Shuttle. But I digress...


Rich
Rich is offline   Reply With Quote

Old   March 7, 2011, 01:33
Default coding for supersonic 3d nozzle
  #9
New Member
 
DINESH KUMAR.T
Join Date: Mar 2011
Posts: 3
Rep Power: 6
dineshastronaut is on a distinguished road
Hi,

Does anybody have a Matlab code for MOC contour design of an axisymmetric supersonic (Mach 2) nozzle they could send me @

dinesh_astronaut@yahoo.co.in

Thanks in advance,
DINESH
dineshastronaut is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
C-D nozzle supersonic jet boundary Gland FLUENT 4 May 24, 2012 00:25
A supersonic combustion in a Laval nozzle argeus FLUENT 0 March 29, 2010 13:52
some questions for supersonic channel nozzle goldenland FLUENT 2 November 4, 2007 22:18
compressible flow in a counterflow nozzle d.vamsidhar FLUENT 0 November 24, 2005 02:45
jet structure at the end of a 2D supersonic nozzle N Menon CFX 1 November 7, 2001 09:04


All times are GMT -4. The time now is 01:05.