Here is my experimentation into this very issue. http://kr2spacemodulator.blogspot.com.au/search/label/KR2S-02%20Fuselage Basically a thrust augmentation/extraction system.
As I am not flying yet I can't give you any results. Paul. Brisbane, Australia -----Original Message----- From: Sid Wood via KRnet Pete, The idea for the larger opening size is to accommodate the increased air volume due to engine heating. However, the exit methodology is particularly critical to the overall efficiency for getting the cooling air overboard and back into the airstream. Simply cutting a big hole in the bottom of the otherwise streamlined lower cowl will not get the job done. The positive incidence angle of most lower cowls will have air going into the lower cowl instead of exiting. You need to create a negative pressure area at the exit. Some designs put a down-turned lip at the forward edge to attempt creating the negative pressure. This works, but is terribly inefficient. A better scheme is to make a rear facing ramp to get the air flowing smoothly toward the exit with the exit cut off square with the slip stream. That way, maximum negative pressure is created at the exit, and the flow rate is maximized. If the ramp is tuned right for the cooling flow, a net increase in thrust can be obtained. Wind tunnel tests on the P-51 confirmed 8 percent increase in thrust just cooling the water radiator. The 4 engine exhaust pipes exit the same ramps as for the cooling air exit. So, there is some flow augmentation due to the engine exhaust blast. ---------------------------------------------------------------------------- -- I working on the lower half of my cowling and need to know the multiplier to size the exit area. I vaguely remember that the exit area should be approx. 1.5 times the total size of the inlet area. Need to qualify that memory. I have Tony Bingelis' "Firewal Forward" book, but can't find that multiplier listed anywhere. Any help or info greatly appreciated. Thanks, Pete Klapp, building N729PK, Canton, Ohio _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected] _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
