From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] cooling system troubeshooting
Date: Thu, 28 Dec 2017 07:37:29 +0800
References: <list-10478457@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Message-Id: <0A98924C-79EB-450F-80B7-82123D733757@gmail.com>

Hi Steve

Aeroplane has not flown. We are still testing on the ground in OAT=E2=80=99=
s of 80-100F
At idle (1900rpm) Delta T=E2=80=99s across Oil coiler - 18F, Water =
coiler - 8F

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=99=
t 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.

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.

Cheers

Steve

> 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:   =
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