|
|
Mike brought up a very good point about using turbochargers at altitude that
were selected/ designed for sea level conditions. One of the major
considerations is how the new operating conditions are relative to the
surge limit shown on compressor maps.(left hand side of the pressure/flow
curves)
Attached is an example of a compressor map. As you can see by the red lines
I drew on the map, if you decrease boost and/or increase flow, you move away
from the surge limit. That is why I believe that the Aussie modification to
a stock HT18 RX-7 turbo (i.e. increasing its flow rate) improves its ability
to operate at high altitudes. Assuming you keep the boost modest (around 7
psi), the increased flow claimed should move you further from the
compressors surge limit area. So this should make it better than a plain
stock HT18 turbo for aircraft use. However, once again I agree with Mike,
if you don't understand the impacts of the different operation environment
(high altitude) on your turbo or have the maps to determine the likely
effect, then seek guidance from turbo experts - but make certain that they
experts that do undestand high alittude operation , because not all
"experts" do..
Ed anderson
----- Original Message -----
From: "Michael D. Callahan (by way of marv@lancaironline.net)"
<micallahan@worldnet.att.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, October 02, 2002 6:24 PM
Subject: [FlyRotary] Re: Turbocharger Hiflows 12A 13B Series IV & V
> Ed,
> I think this turbo may not be well suited for aircraft use, either.
> Just like the stock turbo, this is intended for low altitude applications
> and will be pushing, if not exceeding it's surge limits when it gets up
> there where the air is thin. These small diameter automotive units are
> designed to spin up fast to avoid lag. They are of small diameter to
reduce
> rotational inertia, but that small diameter also means they are going to
> have to really be humming to manage to compress the air to a desirable
> ratio at 7Kft+. Those who are thinking of turboing a 13B for aircraft use
> need to check with somebody who really knows turbos to get the
> correct unit for the applications we will be facing vs an auto
> installation. Turbonetics is a good source of this info, but probably not
> the cheapest, if you know someone who is a turbo guru.
> BTW, Turbonetics is a US owned company. I went to the turbo forum at
> Oshkosh this year, which was put on by Kelly Aerospace, who now owns
> Rayjay, Garret/Airesearch, and Turbonetics.
>
> [Mike.... I had to deep six the formatting in your post... couldn't read
> the bright green text at all. <Marv> ]
>
|
|