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.

 

On Mon, Jul 15, 2013 at 3:33 PM, Bobby J. Hughes <bhughes@qnsi.net> wrote:

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

 

 

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David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net