I read somewhere a few years ago there is not a cert aircraft turbo
installation with a turbo A/R less than 1, fwiw a data point.
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In a message dated 7/15/2013 8:55:25 P.M. Central Daylight Time,
bhughes@qnsi.net writes:
Dave,
With
the super charger I typically cruise with engine rpm’s between 4850 and 5400
set with the prop controller. Cruise climb around 5800-6200. Throttle Body is
wide open and MP controlled with a vernier cable to the super charger bypass.
Applying these settings to the published turbo compressor maps puts me outside
the surge line at low engine rpm and high altitude. Several things could be
done to move the pressure ratio lower. Run higher rpm at altitudes above 15K,
use a ram air inlet to eliminate and boost air pressure at the turbo inlet or
use an intercooler with a lower pressure drop. I have not been able to
find compressor maps that compare different turbine A/R’s for the same
compressor components. My concern would be using a .96 or 1.0 A/R and moving
further toward the surge line. That may not be the case.
Bobby
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of David
Leonard
Sent: Monday, July 15, 2013 7:16 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Turbo Selection
Workbook- Rev1
Should be no effect. Compressor map is a function of
variables independent of what harnessed the energy(ie, the turbine section).
That it not to say that changing the turbine A/R does not effect overall
efficiency and a host of other things, just not the compressor map
itself.
Compressor sections also have an A/R, but changing that
would mean that a whole new compressor map needs to be
generated.
I think I located and corrected two errors. Can anyone
explain how the turbine housing A/R affects the compressor
map?
Bobby
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J.
Hughes
Sent: Sunday, July 14, 2013 6:51 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Turbo Selection Workbook-
Initial Draft
I’ve modified a
turbo sizing workbook I found on the internet. The modification allow for 8
operational scenarios to account for altitude, target HP, OAT etc. Each
scenario provides a corrected airflow and pressure ratio needed to select an
appropriate turbo. The workbook may contain errors so I’m sending it out for
input. Hopefully Ed or someone can validate the formulas and those flying
turbo aircraft will commit on real world experience.
Bobby Hughes