Issue: Air flowing through the fuselage NACA inlet, located just aft of the cowling along the left side, is significantly hotter than ambient temp whenever airspeed is below 130mph or during descents. I suspect the slow moving boundary layer air is being heated through conduction of the engine compartment via the cowling. I added a small vortex generator upstream from the NACA vent in an effort to entrain cooler air outside the boundary layer. It has been suggested heated air spilling from the engine compartment through the cowl inlets maybe the cause or possibly air flowing from the cowl and exhaust exit area from under the fuselage. This TUFT test was conducted to understand the flow path from cowl inlet to fuselage NACA inlet throughout the full airspeed envelope during level flight as well as typical climb and descent profiles.
Test and Test Conditions:
A/S: 0-175 mias
ALT: 20-2500ft PA
DA: 2000-4100ft DA
GW: 1550lbs CG 80.3"
OAT 86-72F
RPM range - 450-2700rpm
Climbs @ Vy (110 mias) max RPM, clean
Descents @ 130 mias 1650 RPM
Landing configuration: Flap 20 deg, gear down![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Sequence
T/O Climbout @ 110 imph full power (2400 rpm)
Level off at 1000 ft PA (2900ft DA) accel to 130 mias stabilize
accel to 175 mias
climb to 2500 ft PA (4000ft DA) @ 110 mias (Vy) full power approx 1600 fpm
descend to 1000 ft @130 imph 1650 rpm approx 800 fpm
Level off at 1000 ft PA, decel to 80 mias, flaps @ 20 deg
decel to 70 mias, flaps 20 deg
descent to landing @ 80 mias, power idle from 180 to touch-down
Results: flow remains mostly longitudinally aligned with AOA. Some perturbations noted just aft of the VG. Prop wash appears to have little affect from idle to full RPM while in flight. Flow around cowl inlet appears to flow parallel with the flow further aft and above the NACA inlet suggesting this isn't contributing to heating. No flow noted from cowl or exhaust exit area.
Please see pics and youtube video.
youtube link:
http://www.youtube.com/watch?v=QsdkD6fLzOE
camera was a CONTOUR HD set at 135deg FOV @720p, 30FPS frame rate.
Test and Test Conditions:
A/S: 0-175 mias
ALT: 20-2500ft PA
DA: 2000-4100ft DA
GW: 1550lbs CG 80.3"
OAT 86-72F
RPM range - 450-2700rpm
Climbs @ Vy (110 mias) max RPM, clean
Descents @ 130 mias 1650 RPM
Landing configuration: Flap 20 deg, gear down
Sequence
T/O Climbout @ 110 imph full power (2400 rpm)
Level off at 1000 ft PA (2900ft DA) accel to 130 mias stabilize
accel to 175 mias
climb to 2500 ft PA (4000ft DA) @ 110 mias (Vy) full power approx 1600 fpm
descend to 1000 ft @130 imph 1650 rpm approx 800 fpm
Level off at 1000 ft PA, decel to 80 mias, flaps @ 20 deg
decel to 70 mias, flaps 20 deg
descent to landing @ 80 mias, power idle from 180 to touch-down
Results: flow remains mostly longitudinally aligned with AOA. Some perturbations noted just aft of the VG. Prop wash appears to have little affect from idle to full RPM while in flight. Flow around cowl inlet appears to flow parallel with the flow further aft and above the NACA inlet suggesting this isn't contributing to heating. No flow noted from cowl or exhaust exit area.
Please see pics and youtube video.
![111oyf7.jpg](/proxy.php?image=http%3A%2F%2Fi56.tinypic.com%2F111oyf7.jpg&hash=bc50c088e41f440caf8b149fe64e1085)
![x4nltt.jpg](/proxy.php?image=http%3A%2F%2Fi53.tinypic.com%2Fx4nltt.jpg&hash=0b1d9818e888199b69249f640e2a1222)
![rk7f9d.jpg](/proxy.php?image=http%3A%2F%2Fi55.tinypic.com%2Frk7f9d.jpg&hash=c72655b2752e1d4e8a63d20e844e55d0)
youtube link:
http://www.youtube.com/watch?v=QsdkD6fLzOE
camera was a CONTOUR HD set at 135deg FOV @720p, 30FPS frame rate.