Motordyne - Tony
#121
05-15-2008, 12:51 PM
Originally Posted by Jeff92se
A total uneducated guess but for that rocket style expanded exhaust tip to function wouldn't two things have to be happening?
1) In order to increase velocity, the opening has to be necked down right before the expansion
2) For expansion/flow, wouldn't the gasses have to be increasing in temp vs decreasing at the end of the exhaust pipe?
1) In order to increase velocity, the opening has to be necked down right before the expansion
2) For expansion/flow, wouldn't the gasses have to be increasing in temp vs decreasing at the end of the exhaust pipe?
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
Last edited by Hydrazine; 05-15-2008 at 01:09 PM.
#122
05-15-2008, 01:57 PM
Originally Posted by Hydrazine
Right on Jeff!
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
I presume sedan is part of the production line... I'm wondering how much different it is though - tips like the pic will never fit (will they?)
#123
05-15-2008, 04:08 PM
Originally Posted by Hydrazine
Right on Jeff!
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
#124
05-15-2008, 04:10 PM
#126
05-23-2008, 03:28 PM
#127
05-23-2008, 03:32 PM
#128
05-23-2008, 03:51 PM
Originally Posted by Hydrazine
Right on Jeff!
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
You're in the right ball park, but you're thinking of a DeLaval nozzle. A diffuser is/does the exact opposite of a DeLaval nozzle even though they look similar.
A DeLaval nozzle (or rocket nozzle) speeds up the exhaust plume, decreases temperature, decreases static pressure and increases dynamic pressure. A DeLaval nozzle relies on the principle of adiabatic expansion.
Conversely, a diffuser slows down the exhaust plume, increases static temperature, increases static pressure and decreases dynamic pressure. A diffuser relies on the principle of adiabatic compression.
In this case, it is the decrease in dynamic pressure that is advantageous. Rather than wasting energy as a blast of high velocity gas out the exhaust tip, the diffuser slows it down before venting to atmosphere.
The conservation of kinetic energy (or RhoV^2/2G) means the engine can push out the exhaust gas with less resistance. Thus less pressure drop and better performance.
Maybe I'm making it more technical than it needs to be, but I'm not one pass up advantageous engineering techniques.
---
Edit: If automotive exhaust systems were designed and built by Boeing Rocketdyne, they would be doing the same thing.
E equals M C Squared 
#129
05-23-2008, 08:13 PM
#130
05-23-2008, 10:58 PM
#131
05-28-2008, 02:38 PM
#132
05-28-2008, 07:02 PM
#133
05-28-2008, 07:47 PM
#134
05-28-2008, 08:21 PM
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#135
05-28-2008, 10:43 PM
Hehehe. Maybe not a bad idea.