Hawker Hurricane´s & early Spitfire´s ´each had an exhaust each side with three exhaust ports. Later Spitfire´s have individual exhaust ports for each cylinder, ie six each side. All Mustangs, even the early ones had six each side. Did the change to individual exhaust ports give more horsepower, etc. Who in the “know” can tell if this is the reason! Advantages & Disadvantages?
By: MerlinPete - 20th October 2007 at 22:07
Whilst we’re talking about exhaust stubs, what was the purpose of siamesing the rear two ports and not the rest on some versions of the Mossie and, I think, Lanc?
To keep the heat away from the wing leading edge on the Mossie when fitted with single-stage (short) Merlins. I haven`t seen it on Lancasters though.
Pete
By: Mark12 - 19th October 2007 at 08:31
The airflow through the radiator ducting of the Mustang will never add to the lift of the airframe. Lift is only produced by an airflow over an airfoil profile and that isn’t present there. The clue is in the previous sentence (highlighted above): the combination of radiator and ducting managed to decrease the total drag of the airframe a bit and that translates into extra knots of speed for the same powerplant and weight.
‘Meredith Effect’
Mark
By: mike currill - 19th October 2007 at 03:14
The airflow through the radiator ducting of the Mustang will never add to the lift of the airframe. Lift is only produced by an airflow over an airfoil profile and that isn’t present there. The clue is in the previous sentence (highlighted above): the combination of radiator and ducting managed to decrease the total drag of the airframe a bit and that translates into extra knots of speed for the same powerplant and weight.
Plus the jet effect of the radiator heated air expanding and pushing on the slightly open exit gate if some writings on the subject are to be believed (sounds feasible but was it?). Whilst we’re talking about exhaust stubs, what was the purpose of siamesing the rear two ports and not the rest on some versions of the Mossie and, I think, Lanc?
By: MerlinPete - 18th October 2007 at 18:30
Peter – you can add Whitley to 1B2 as well.
Cheers Elliott, I had a feeling about that but I certainly couldn`t find a picture to prove it!
Regarding my comment about the Barracuda, of course both those systems were aimed at night flying! I had had a long day!
Pete
By: Whitley_Project - 17th October 2007 at 23:36
Peter – you can add Whitley to 1B2 as well.
By: MerlinPete - 17th October 2007 at 23:17
1D Barrcuda.
1F Sea Hornet. (less outlets)
John
Just noticed that some Barracudas had multi ejector flame dampers as fitted to the Lanc, which I assume means that they were being used at night?
Pete
By: Good Vibs - 11th October 2007 at 15:31
Thanks to all for the interesting & professional replys.
It looks like the designers at the time were busy looking for the best and found many answers.
By: John Aeroclub - 9th October 2007 at 08:26
1A: Spitfire, Battle
1B1: Spitfire, Hurricane, Fulmar, Wellington, Whitley, Defiant, Battle, Henley
1B2: Spitfire, Hurricane, Wellington
1C: Halifax
1D: Beaufighter IIF
1E1: Lancaster and derivatives, Beaufighter IIF
1E2: Spitfire Mk VIII and IX
1F: Mosquito, Lincoln, Casa III (with no1 and 6 outlets deleted)Anyone think of any more?
Pete
1D Barrcuda.
1F Sea Hornet. (less outlets)
John
By: MerlinPete - 8th October 2007 at 16:19
What an exhausting question. Some of the variations of Merlin exhausts. Now name the types to which these examples were fitted.
John
1A: Spitfire, Battle
1B1: Spitfire, Hurricane, Fulmar, Wellington, Whitley, Defiant, Battle, Henley
1B2: Spitfire, Hurricane, Wellington
1C: Halifax
1D: Beaufighter IIF
1E1: Lancaster and derivatives, Beaufighter IIF
1E2: Spitfire Mk VIII and IX
1F: Mosquito, Lincoln, Casa III (with no1 and 6 outlets deleted)
Anyone think of any more?
Pete
By: Archer - 8th October 2007 at 10:59
In the Mustang’s case I understood that it didn’t necessarily give any increase in speed (beyond that added by the decrease in drag of course), but did create some lift. Could be a load of rubbish of course…
greg v.
The airflow through the radiator ducting of the Mustang will never add to the lift of the airframe. Lift is only produced by an airflow over an airfoil profile and that isn’t present there. The clue is in the previous sentence (highlighted above): the combination of radiator and ducting managed to decrease the total drag of the airframe a bit and that translates into extra knots of speed for the same powerplant and weight.
By: gregv - 8th October 2007 at 00:04
A similar development was the expansion and compression chambers in radiator intake exhaust design, seen at its peak in the Mustang and MB-5, but also used earlier on the Spitfire and 109. This went some way to negate the drag created, and (I think – anyone?) actually added MPH to the Mustang.
In the Mustang’s case I understood that it didn’t necessarily give any increase in speed (beyond that added by the decrease in drag of course), but did create some lift. Could be a load of rubbish of course…
greg v.
By: John Aeroclub - 7th October 2007 at 22:44
An exhaustive answer.
The real question is the development of the ‘ejector’ type exhaust which includes the ‘Siamesed’ three stub efforts as well as the six stub. Previously, both prototype Spitfire and Hurricane had exhausts that just exited to the air at right angles to the direction of the airflow. Previous to that were either the long pipe or the bizarre type seen on the Hawker Hart family (example on the Hart trainer in the RAFM) which had no speed advantage, but (I think) helped with disguising the exhaust flame.
A similar development was the expansion and compression chambers in radiator intake exhaust design, seen at its peak in the Mustang and MB-5, but also used earlier on the Spitfire and 109. This went some way to negate the drag created, and (I think – anyone?) actually added MPH to the Mustang.
None add horsepower, they all remove drag and / or add to thrust or remove factors that choke or make the engine less efficient.
Short, simple and point them aft is the best!
What an exhausting question. Some of the variations of Merlin exhausts. Now name the types to which these examples were fitted.
John
By: JDK - 7th October 2007 at 02:27
The real question is the development of the ‘ejector’ type exhaust which includes the ‘Siamesed’ three stub efforts as well as the six stub. Previously, both prototype Spitfire and Hurricane had exhausts that just exited to the air at right angles to the direction of the airflow. Previous to that were either the long pipe or the bizarre type seen on the Hawker Hart family (example on the Hart trainer in the RAFM) which had no speed advantage, but (I think) helped with disguising the exhaust flame.
A similar development was the expansion and compression chambers in radiator intake exhaust design, seen at its peak in the Mustang and MB-5, but also used earlier on the Spitfire and 109. This went some way to negate the drag created, and (I think – anyone?) actually added MPH to the Mustang.
None add horsepower, they all remove drag and / or add to thrust or remove factors that choke or make the engine less efficient.
Short, simple and point them aft is the best!
By: antoni - 7th October 2007 at 00:25
Spitfire Mk Vb EN946 was tested at Boscombe Down in late 1943. It was found that replacing the exhausts with fishtail units increased the speed by 7 mph. The hot gases leaving the exhausts can act like small rockets. Highly tuned engines used in the Reno Races make use of this. At the very high boost pressures used there is a decrease in the horse power output because more hp is needed to drive the supercharger. It is the jet effect of the exhausts that gives an increase in air speed.
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October 6, 2007 at 11:21 pm