From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] cooling modes
Date: Sat, 21 Nov 2020 13:03:32 +0800
References: <list-967589@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-967589@logan.com>
Message-Id: <DCD0AC56-CB94-4A22-A801-9915BC2DA02E@gmail.com>

Hi guys.

I think we are talking about two different beasts.
K&W Chapter 12 describes the Streamline (Trumpet) shape.
However we also use Oblique Flow (Wedge) diffusers as descibed by London =
Clopfer and Wolf.
And we use both together, a Streamline diffuser feeding an Oblique =
diffuser as in Tracy=E2=80=99s RV8 setup that many of us modelled from.

Steve Izett


> On 21 Nov 2020, at 11:34 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>=20
> I agree, but I'd describe it more like the core was down the =
centerline of a streamline diffuser, and the air feeds from the wide =
end. Half the original diffuser disappears.
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> On 11/20/2020 8:22 PM, David COOK hoursaway1@comcast.net wrote:
>> Wedge is kind of a poor term for what is needed, more of a bell mouth =
like on a trumpet with the rad. being at the large end. DRC RV6A Rotary
>>> On 11/20/2020 9:03 PM Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>>> =20
>>> =20
>>> Hi Bruce,=20
>>>=20
>>> The driver for me was trying to remain within the constraints of =
money, a stock cowl with minimum 'surgery', with nothing hanging out of =
the cowl. Another driver was due to 'standing on the shoulders of =
giants'; Tracy Crook does really light weight installations, and his =
calcs showed that at least in his RV4, he needed the weight of the heat =
exchangers to be up front, to keep CG in the right place. My FWF weighs =
almost exactly the same as an O-320, so for now, I'll keep the  wedge in =
place. Please be aware that my setup may not survive to the 2nd flight. =
:-)=20
>>>=20
>>> In retrospect, I might well have done the same as Steve mentioned, =
and at least try to tuck the rad into the space behind/below the engine =
and feed it with a duct up to the prop.=20
>>>=20
>>> Charlie=20
>>>=20
>>> On 11/20/2020 6:59 PM, Bruce Cosgrove bcosgrove@mac.com wrote:
>>>> Hi Steve, Charlie, Matt, Roy and others
>>>> I am in the process making up a  cooling system for a Tango 2 and =
was also planning to use the wedge shaped diffuser design, however the =
information that I have been reading from the homebuilt airplanes site =
discussing alternate approaches with less drag and improved efficiency? =
has me re thinking my design towards a belly mounted radiator.  The =
comments under the heading  Successful Auto Conversion Trials, =
Tribulations and Tips, I found particularly interesting - in particular =
input from Russell and RJ6ejGUY who both have devised systems that are =
working well for them  Belly radiators may not be everyones idea of how =
to proceed but I like the idea of relatively unimpeded air flow and =
freeing up space in the cowling.  any feedback would be much =
appreciated.
>>>> =20
>>>> Bruce
>>>>=20
>>>> On 21 November 2020 at 10:00:57, Stephen Izett =
stephen.izett@gmail.com (flyrotary@lancaironline.net) wrote:
>>>>=20
>>>>> Nice work Charlie.=20
>>>>>=20
>>>>> Steve=20
>>>>>=20
>>>>> > On 21 Nov 2020, at 6:50 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:=20
>>>>> >=20
>>>>> > My (untested in combat) version for my radiator looks similar, =
but because the inlet is offset, I had to use a turning vane to get flow =
into the lower front of the core. The outside doesn't give a good idea =
on how 'tight' the inner surface is. I had to use expanding foam to fill =
the inside, then re-shape, then glass over the foam. As I said, the back =
1/4-1/3 of the diffuser tapers tightly to almost touch the core at the =
back.=20
>>>>> >=20
>>>>> > After observing both rotary and piston installations that work, =
I'm beginning to think that turning vanes may be the 'good enough' vs =
fighting for perfection in diffuser shape. My oil cooler core has a much =
more elaborate vane setup, driven by the very short duct length and even =
greater offset to the bottom edge of the core.=20
>>>>> >=20
>>>>> > Charlie=20
>>>>> >=20
>>>>> >=20
>>>>> > On 11/20/2020 4:22 PM, Stephen Izett stephen.izett@gmail.com =
wrote:=20
>>>>> >> Hi Roy=20
>>>>> >>=20
>>>>> >> Here is a photo of our Mocal 44 row oil cooler with diffuser. A =
K&M Streamline into a wedge.=20
>>>>> >> Not sure of the dimensions of hand. The Mocal web site will =
have specs so you could get a rough idea of size.=20
>>>>> >> I tested this one recently with a leaf blower approximating 100 =
knot air flow and in that test it was very even.=20
>>>>> >>=20
>>>>> >> Having said that, I tested our water radiator wedge diffuser =
when I built it years ago and had it reasonably even=20
>>>>> >> measuring pressures across the exit face, but now instrumenting =
it in flight its flow is vastly uneven.=20
>>>>> >>=20
>>>>> >> I have found that the flow is dependant not only on getting the =
diffuser shape right according to the various papers (eg. K&W, London, =
Oblique Flow Diffusers - Streamline )=20
>>>>> >> But importantly the environment it ends up in. The papers share =
data for ideal conditions with for example unobstructed exit air paths.=20=

>>>>> >> My thoughts now are that this has a significant impact on the =
performance and therefore the advantage of instrumenting in flight and =
reshaping for actual conditions.=20
>>>>> >>=20
>>>>> >> The data I collected yesterday of our H2O diffuser reveals that =
the air flow in various points across the face are very different.=20
>>>>> >> Simplified, if I average the pressures at the five points I =
measured, then comparatively the back is up 20%, the centre up 25% and =
the front down 60% from that average figure.=20
>>>>> >> I=E2=80=99m figuring a 20% difference is probably OK, but my =
front to back/middle difference of ~80% down in the front top of that =
radiator may hold significant room for improvement.=20
>>>>> >> Further, my data suggests that as IAS rises those differences =
are amplified.=20
>>>>> >> So I am now targeting the modifications for our worst case =
conditions of WOT sea level ~200hp and initial climb numbers of 115KIAS.=20=

>>>>> >>=20
>>>>> >> Cheers.=20
>>>>> >>=20
>>>>> >> Steve Izett=20
>>>>> >>=20
>>>>> >>=20
>>>>> >>=20
>>>>> >>> On 21 Nov 2020, at 3:37 am, ROY GLENN rglenn14@sbcglobal.net =
<flyrotary@lancaironline.net> wrote:=20
>>>>> >>>=20
>>>>> >>> Could some ne post a photo of their wedge shape and =
dimensions.=20
>>>>> >>> Thanks Roy=20
>>>>> >>>=20
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>  =09
> This email has been checked for viruses by Avast antivirus software.=20=

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