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Of course exhaust thrust was known of, you'd only have to stand behind a '20's Le Mans racer to know it
 However, inlines lend them selves to unrestricted ejector style exhaust stubs, while _as far as I know_ radials seem to use a collector system. Can you mention any radials where exhaust thrust was exploited? I seem to remember a figure of 400 lbs thrust being posted for a packard Mustang at full chat, but that seems quite a bit over the top to me. |
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The A6M5 went to ejector exhaust from collector exhaust of previous models.
 The truth, the whole truth and nothing but the truth to the best of my knowledge, always. swept wings on the Me262 to correct CG problem A Sealion success is a delusional fantasy |
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How about the one we are spending several hundred thousand dollars on and own some 28 examples to get three running? The BMW801 series...   Our Museum glorifies no state, but strives to use these aircraft as a memorial for all lost in war. Our freedom can only be truly appreciated when held in contrast to those who sought to destroy it. Our staff is proudly made up of people from many cultures and religions. Click the photos for details of our projects. "Those who do not remember history are destined to repeat it." - Winston Churchill |
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The Fw gills produced thrust? Cool, I never knew that!
Any idea if the effect was measured? I've heard it say (but don't really know) that Merlin exhausts went from being design for ultimate motor efficiency (terrestial racing thinking) to being deliberately designed for thrust at the possible expense of ultimate horse power because the effect was sufficient enough to warrent it. I wonder what a difference the 60's east german research into two stroke expansion exhausts could have made if it hadn't had to compete with jets |
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Henri Coanda had a short lived piston engine with augmented exhaust thrust plane.
Then it caught fire from that exhaust during takeoff.... And there was a Caproni, IIRC, that was a piston driven jet that at least did fly. "My views are solely my own and do not reflect the views of my Squad or its members" |
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IL2 Moderator |
Just a bit more on what M_Gunz said.
In the classic (Whittle) jet the compressor at the front of the engine is driven by a turbine in the exhaust flow. In the Italian engine, though, the compressor was driven by a reciprocating engine. There have been other engines of a compound nature, e.g. the turborocket which is a ramjet with auxiliary compression for low speed driven by a rocket motor exhaust. The Italian engine had the advantage that you weren't relying on the feedback between the turbine to compressor being exactly right to keep the engine going - the early jets were prone to runaway, flameout, etc. if the feedback got out of kilter. With a compound engine with the compressor driven by a reciprocating engine you could simply change the throttle settings on the reciprocating engine to change the compressor settings to suit the fuel flow and airspeed. |
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The cowl flaps are part of the cooling system not the engine exhaust system. http://www.white1foundation.org/parts/cowlflaps18.jpg AFAIK they produce no significant thrust.
Exhaust thrust is significant especially at high velocity and high altitudes. Look at it like this: Thrust at altitude is a function of density ratio to the power of an experimentally determined exponent. Many references use X=1 and some use X=.8. This means that a WWII era jet engine producing 1600lbs of thrust at sea level is able to produce some 716lbs of thrust at 25,000ft. The BMW801D2 produces ~264lbs of exhaust thrust at 25,000ft. This means the engine is producing some 37% of the thrust a WWII jet engine is making at that altitude from the exhaust alone. Another way to look at it is than in the FW190 at 25,000ft, 25% of the thrust at top level speed comes from the exhaust. That is rather simple explanation but you get the trend and the idea. All the best, Crumpp Our Museum glorifies no state, but strives to use these aircraft as a memorial for all lost in war. Our freedom can only be truly appreciated when held in contrast to those who sought to destroy it. Our staff is proudly made up of people from many cultures and religions. Click the photos for details of our projects. "Those who do not remember history are destined to repeat it." - Winston Churchill |
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