GESchwarz
Well-Known Member
I am particularly interested in seeing if it is possible to maintain laminar flow beyond the turn, where the sides of my fuselage go from divergent (4 degs from center line) to convergent (5 degrees from centerline), located at the wing trailing edge. The transition area is a 15" arc sector.
I've had this conversation in the past about utilizing engine exhaust in a venturi extractor to draw in the boundary layer, just as it has been used to draw cooling air for an air cooled engine and it was dismissed as impractical. If all we ever do is take no for an answer, we'd have nothing new.
I imagine an array of .050" diameter holes spaced about a quarter inch appart and the area of spanning several inches from front to back. The array would be located immediately forward of the transition.
Much has been said about the ineffeciency of the internal combustion engine. If the hot exhaust gasses are not driving a turbocharger it's all completely wasted into the atmosphere. Certainly if these hot gasses can be used to generate induction boost, it should also be able to generate a suction.
The big questions are...
What sort of CFM would be required at say a cruise speed of 175 mph, to thin the boundary layer to a point at which the airflow will remain laminar from the transition to the tail of the machine?
What sort of performance can a venturi extractor achieve, using the exhaust of a typical 200 hp internal combustion engine?
I don't imagine there is much data out there, therefore the only way to get it may be to experiment. The manifold could be made of a simple enclosure over the hole array, an exhaust venturi, and a thin wall vacuum hose connecting the two. The first challenge is in designing an effecient extractor. The prototype would have to be variable in order to discover the optimum geometry. The first question can be answered empirically as well simply by putting the whole works to the test. I'll just have to design the machine to accomodate this test after the build is complete and I've flown off the first 40 hours.
I've had this conversation in the past about utilizing engine exhaust in a venturi extractor to draw in the boundary layer, just as it has been used to draw cooling air for an air cooled engine and it was dismissed as impractical. If all we ever do is take no for an answer, we'd have nothing new.
I imagine an array of .050" diameter holes spaced about a quarter inch appart and the area of spanning several inches from front to back. The array would be located immediately forward of the transition.
Much has been said about the ineffeciency of the internal combustion engine. If the hot exhaust gasses are not driving a turbocharger it's all completely wasted into the atmosphere. Certainly if these hot gasses can be used to generate induction boost, it should also be able to generate a suction.
The big questions are...
What sort of CFM would be required at say a cruise speed of 175 mph, to thin the boundary layer to a point at which the airflow will remain laminar from the transition to the tail of the machine?
What sort of performance can a venturi extractor achieve, using the exhaust of a typical 200 hp internal combustion engine?
I don't imagine there is much data out there, therefore the only way to get it may be to experiment. The manifold could be made of a simple enclosure over the hole array, an exhaust venturi, and a thin wall vacuum hose connecting the two. The first challenge is in designing an effecient extractor. The prototype would have to be variable in order to discover the optimum geometry. The first question can be answered empirically as well simply by putting the whole works to the test. I'll just have to design the machine to accomodate this test after the build is complete and I've flown off the first 40 hours.
