Turbo engine Blow Off Valve location, advantages and detriments?
Turbo engine Blow Off Valve location, advantages and detriments?
(OP)
Gentlemen,
When I look at the pictures of BOV installations for small turbo engines, some questions came to my mind.
Is the BOV placement in an immediate proximity of the compressor outlet a bit counterproductive?
When the BOV valve opens, it creates a reverse flow of the large volume of air from the plenum and the chargecooler towards the turbo.
When the pressure in the duct drops and valve closes, a shock wave hits the compressor inducer in reverse direction creating a surge (which we are trying to mitigate by installing the BOV!).
BOV location between the plenum and the chargecooler seems to be a better solution; however it may have similar adverse effect.
BOV location at the plenum (or close to it) may be the best, because it will not create a reverse surge in the pipe connecting the plenum to compressor outlet.
Your thoughts?
When I look at the pictures of BOV installations for small turbo engines, some questions came to my mind.
Is the BOV placement in an immediate proximity of the compressor outlet a bit counterproductive?
When the BOV valve opens, it creates a reverse flow of the large volume of air from the plenum and the chargecooler towards the turbo.
When the pressure in the duct drops and valve closes, a shock wave hits the compressor inducer in reverse direction creating a surge (which we are trying to mitigate by installing the BOV!).
BOV location between the plenum and the chargecooler seems to be a better solution; however it may have similar adverse effect.
BOV location at the plenum (or close to it) may be the best, because it will not create a reverse surge in the pipe connecting the plenum to compressor outlet.
Your thoughts?





RE: Turbo engine Blow Off Valve location, advantages and detriments?
RE: Turbo engine Blow Off Valve location, advantages and detriments?
RE: Turbo engine Blow Off Valve location, advantages and detriments?
RE: Turbo engine Blow Off Valve location, advantages and detriments?
I don't think there is any back flow from the CAC, just a reduction in the airflow rate into the cooler.
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RE: Turbo engine Blow Off Valve location, advantages and detriments?
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Turbo engine Blow Off Valve location, advantages and detriments?
You are right, closer to TB-s is better.
Brian,
Could you elaborate on your notion of "non issue" and "arrange" in non-presumptuous way?
RE: Turbo engine Blow Off Valve location, advantages and detriments?
Even if it does open violently ... there is no need for it to close violently. I can understand wanting to open it quickly to keep the compressor out of surge, but it need not close so quickly. Even if it takes (say) a quarter of a second to close, that's not fast enough to create a "shock wave". The only way the driver would notice is if they got back on the throttle during the closing period ... but if the valve is sized to release only enough flow to keep the compressor out of surge (as opposed to being grossly oversized), the turbo will easily overwhelm that slight temporary "boost leak" if it is actually operating under load.
And even if all that is disregarded ... The real thing that the turbo won't like is a surge condition (approaching dead-heading) under load (while it still has significant pressure ratio across it). The blow-off valve itself is responsive to the pressure in the intake duct at the location where it is installed. If there were to be something approaching a "shock wave" caused by the backflowing air, the blow-off valve itself would see the increased pressure at that location and simply open again (or stop its closing motion, as the only foreseeable condition in which this might happen is while the valve is in the process of closing).
I have never heard of the issue proposed by the original poster being a real-world cause of turbo failures.