Ralph Wiggum Moar Powar Babeh Lifetime Members 19,323 Member For: 19y 1m 19d Gender: Male Location: Perth Posted 13/01/12 10:34 AM Share Posted 13/01/12 10:34 AM whats driving the compressor in the 737 apu? a fairly significant fuel air energy conversion in the arse end?whats driving the compressor wheel in a turbo? the left overs of significant fuel air energy conversion. that happens too cease once the throttle is closed and the compressor surge starts?not same/same Link to comment Share on other sites More sharing options...
Paulie2256 Donating Members 7,441 Member For: 15y 11m 20d Gender: Male Location: SE Melbourne Posted 13/01/12 11:19 AM Share Posted 13/01/12 11:19 AM True, when the throttle is shut the force spinning the turbo dies down too so the only opposing force to the air from the surge is the momentum of the small impeller of the turbo. Bov's help throttle response on gear changes by letting the surge out so the turbo can keep spinning. Link to comment Share on other sites More sharing options...
1600dave Donating Members 872 Member For: 13y 10m 1d Posted 13/01/12 11:27 AM Share Posted 13/01/12 11:27 AM Someone get one of those Garrett turbo rpm gauges and test with/without a BOV. Be interesting to see the differences. Link to comment Share on other sites More sharing options...
getuted Member 34 Member For: 15y 5m 2d Gender: Male Location: brisbane Posted 13/01/12 11:36 AM Share Posted 13/01/12 11:36 AM I'm not saying don't make your car flutter nor do I care if you do, just pointing out the fact the it does damage the turbo,as for a fairly significant fuel air energy conversion you can be the judge,an APU in a 737-400 is basically a GT60 sized turbo with a combustion chamber coupled to the turbine housing and a small gearbox on the compressor housing, much like the home made "jet engines" on youtube. They make approx 420 hp and burn around 350 kg of fuel per hour, about the same as a 420hp xr6t would if you held it flat-out in 6th for an hour, they are a "starter motor" for the main engines and work the same as a turbo which is why they have surge valves (BOV"s) on them. Link to comment Share on other sites More sharing options...
Impellor Member 835 Member For: 14y 3m 22d Gender: Not Telling Posted 13/01/12 11:48 AM Share Posted 13/01/12 11:48 AM (edited) Some time back I did do some research on the above, and from memory the evidence suggested that a bov was crucial for turbo durability, but there was no evidence that could categorically state to what extent durability was compromised. But logic suggests that a turbine wheel spinning one way and then back pressurised air inturn creating forces trying to spin the wheel in the opposite direction, surely creates stresses on fins, shaft and bearings. Now as I said, this is from memory so please correct me if I am not understanding this correctly, Cheers Edited 13/01/12 11:49 AM by Impellor Link to comment Share on other sites More sharing options...
1600dave Donating Members 872 Member For: 13y 10m 1d Posted 13/01/12 10:02 PM Share Posted 13/01/12 10:02 PM I liked Simon from Nizpro's view on them, made sense to me anyway.At the end of the day everyone is going to have their own opinion and its a hard thing to prove. Link to comment Share on other sites More sharing options...
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