From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: cooling system troubeshooting
Date: Thu, 28 Dec 2017 22:07:01 +0800
References: <list-10480760@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Message-Id: <9B8A46B1-D5FA-4058-89F6-6AAF2B929FB1@gmail.com>

Hi Bobby
With the top cowl off she cools a little better.=20
I put this down to air circulating/tumbling around the back of the =
radiator.
Cant remember what happened when we ran it a while back with the bottom =
cowl off.

Last week I did do some quick pressure tests and one troubled me.
I had the differential pressure pickups in the cowl and water diffuser =
and though the wool tufts say a small amount of air is flowing through =
the rad, the pressure reading said it should be flowing backwards.
This why I=E2=80=99m really keen to do the science and work out what the =
pressures are doing.

Steve




> On 28 Dec 2017, at 9:56 pm, Bobby J. Hughes bhughes@qnsi.net =
<flyrotary@lancaironline.net> wrote:
>=20
> Steve,
>=20
> How does it cool with the cowling removed?=20
>=20
> Bobby
>=20
> Sent from my iPad
>=20
> On Dec 28, 2017, at 7:12 AM, Stephen Izett stephen.izett@gmail.com =
<flyrotary@lancaironline.net> wrote:
>=20
>> Hi Guys
>> In search of cooler running this is what we did today and plan to do =
next.
>> Any insights/thoughts welcome.
>>=20
>> Today we:
>> 1. Installed a new pressurised tank with 21psi cap at the highest =
point possible. It is fed from:
>>  A. Rear Iron.=20
>>  B. Top of the coolant out manifold (engine heading for radiator).=20
>>  C. Top of radiator inlet tank
>> It returns to the pump inlet via a hose with a 1/8=E2=80=9D =
restriction.
>> It overflows into an expansion tank accessible via a hatch in the top =
cowl
>>=20
>> 2. Tested new config:
>> A. I wondered why she wasn=E2=80=99t running as sweet as usual and =
realised the Leading plugs weren=E2=80=99t firing so fixed the problem.
>> 	With an OAT of ~ 80F after 20 mins of idle at 1800 rpm water =
gets to over 225 and I shut it down. (No significant change from last =
setup)
>> B. Measured Cowl pressure at a point between water radiator and cowl =
flap referenced to Static -=20
>> 	At idle the pressure is 0 inches of water
>> 	At 6000rpm (fine pitch) it hits about negative 1/2 inch of water =
(the exit shape, exhaust augmenter and cowl flap appear to be producing =
some negative pressure in the cowl)
>> 	I=E2=80=99ve currently stuffed the gear opening full of pillows =
and rags to emulate the gear being up and door closed.
>>=20
>> So here is the detail:
>> The 193 inch^3 oil cooler is fed by a 7.4 inch^2 inlet well below the =
spinner and into a trumpet diffuser.=20
>> The 540 inch^3 water cooler is fed by the 16.5 inch^2 right cheek =
inlet very close to the spinner and into a trumpet and then wedge =
diffuser. (Tried to copy Tracy=E2=80=99s RV8 cooler design)
>> Ive put a matrix of wool tufts over the back of the water cooler and =
distribution appears quite even.
>> See photo showing oil cooler inlet below spinner vs cheeks.
>> Currently the oil temps lag the water temps by a good 30F.
>>=20
>> So next opportunity I=E2=80=99m thinking:
>> 1. Because its a quick and easy test, I=E2=80=99m planning to close =
off part of the oil cooler inlet and see what this does to the water =
temps.
>> Will this provide a better balance between oil and water with the =
water rad getting a better share of the exit air flow?
>>=20
>> 2. Seek to plot a set of pressure measurements at various locations =
around the cowl and diffusers for various;
>> 1. RPM=E2=80=99s
>> 2. Cowl Flap position
>> 3. Gear door open / closed (stuffed full of pillow and rag).
>>=20
>> Many thanks for your ponderings and any of your thoughts.
>>=20
>> Cheers
>>=20
>> Steve
>> Perth Western Australia
>> Glasair Super IIRG - Renesis 4 port RD1C EC3 EM3=20
>>=20
>>=20
>>=20
>> 	<VH-EXPsmall.jpeg>
>> =20
>>> On 28 Dec 2017, at 7:37 am, Stephen Izett stephen.izett@gmail.com =
<flyrotary@lancaironline.net> wrote:
>>>=20
>>> Hi Steve
>>>=20
>>> Aeroplane has not flown. We are still testing on the ground in =
OAT=E2=80=99s of 80-100F
>>> At idle (1900rpm) Delta T=E2=80=99s across Oil coiler - 18F, Water =
coiler - 8F
>>>=20
>>> We are seeking to do two things:
>>> 1. Review our design - have we made a clear mistake somewhere -
>>> a. We managed to not have an air bleed at the engine coolant in/out =
which is the highest point!
>>> We only have returns to the pressurised expansion tank/cap from rear =
iron and one from the top of the radiator in tank (returning to pump =
in).
>>> b. We do not have a small hole in the Renesis bypass which we =
plugged.
>>> c. Lynn uses a restrictor in the outlet to make sure the pump =
isn=E2=80=99t cavitating. Our coolant out plumbing has far less =
restriction than the stock setup (All be it the radiator is a dual pass =
so presents  significantly more resistance)
>>> d. We have just finished building a cowl flap in an attempt to =
control cowl pressure.
>>>=20
>>> 2. Do the science and seek to measure what the air and water are =
doing.
>>> a. Not sure how to measure the water flow easily.=20
>>> b. We are testing today to see what air pressures exist around the =
diffusers and cowl.
>>>=20
>>> Cheers
>>>=20
>>> Steve
>>>=20
>>>> On 28 Dec 2017, at 3:00 am, Steven W. Boese SBoese@uwyo.edu =
<flyrotary@lancaironline.net> wrote:
>>>>=20
>>>> Simply determining radiator coolant delta T may be useful in =
troubleshooting the cooling system.  The water cooling system is a =
closed system with two heat exchangers: one is the engine putting heat =
into the coolant and the other is the radiator removing heat from the =
coolant.  When all of the coolant flows through the engine and radiator =
(coolant bypass passage blocked by either a plug or a fully open =
thermostat) the engine and radiator must have the same coolant delta T.  =
At a given power level and coolant flow rate we all should see similar =
delta T's since we are using very similar engines.  At sea level full =
throttle, that coolant delta T should be close to 15 degrees F.  Since =
the heat exchanger characteristics of a clean engine are essentially =
fixed, a coolant delta T of much more than15 degrees F at full throttle =
would most likely be a result of insufficient coolant flow rate through =
the system.  This could result from a defective water pump or too much =
coolant bypassing the radiator such as due to an incompletely closed =
thermostat bypass passage, too large air bleeds from engine coolant high =
points, or an open cabin heater coolant loop.  An EWP would introduce an =
additional variable. =20
>>>>=20
>>>> With proper coolant flow rate, when the radiator cannot remove =
enough heat from the system, the overall coolant temperature will rise =
until one of two conditions are achieved.  First, the radiator may be =
capable of removing enough heat with a greater delta T between the =
coolant and the air.   The system will stabilize, but the delta T's of =
the coolant across the engine and across the radiator will remain =
essentially equal and unchanged.  This type of behavior is demonstrated =
in the attached data plot for a full throttle climb from 7,000 to =
14,0000 ft msl with a typical OAT decrease.
>>>>=20
>>>> The second condition would be to boil the coolant and remove heat =
due to the phase change.  This may not maintain a closed system and the =
stable condition would then, of course, be temporary.
>>>>=20
>>>> The goal of designing the radiator side of the cooling system is to =
size the radiator and air flow through its core to achieve the desired =
overall coolant temperature.  Trying to change the coolant delta T at a =
given RPM and power level will prove frustrating.
>>>>=20
>>>> The same would be true of the oil cooling system if the oil flow =
rate was consistent between our systems.  However, if part of the oil =
flow is returned to the sump at the front cover relief valve, =
comparisons between different setups will be of limited value unless the =
actual oil flow rates through the oil coolers are known. =20
>>>>=20
>>>> Steve Boese
>>>> RV6A, 1986 13B NA, RD1A, EC2
>>>>=20
>>>>=20
>>>> <coolant delta T.jpg>--
>>>> Homepage:  http://www.flyrotary.com/
>>>> Archive and UnSub:   =
http://mail.lancaironline.net:81/lists/flyrotary/List.html
>>>=20
>>>=20
>>> --
>>> Homepage:  http://www.flyrotary.com/
>>> Archive and UnSub:   =
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>>=20