>
> > Buly,
> >
> > Before you make any changes, install a pressure differential
> > system
> > to measure the inlet pressure, pressure under the cowl on the
> > 'downstream' side, and static pressure. Then make a flight and
> > record the data . You need to have this as a base line for any
> > changes to see if the problem is being made better or
worse. Some
> > changes that seem 'obvious' have a negative effect. The only
> > way to
> > be sure is to make the measurements.
> >
> > Bill Schertz
> >
>
> Hi Bill,
> I have good cooling performance when flying and even if I'm
facing
> the wind, on the taxiway I'm fine.
> If I'm waiting for takeoff and have my back to the wind, or
even
taxi
> downwind, I can see the temp's
> ticking up. So, obviously there is no movement of the air
thru the
> cores. I don't think even the irrigation system will make
too much
> difference
> if the air is not moving. BTW I have installed two fogging
nipples
> on the radiator, but still have to buy a pump and wire it up.
> Will keep you posted.
> Buly
>
Buly,
You might want to experiment with the geometry of your augmentor,
before you cut another hole in your cowling. Proper placement
of the
exhaust entering the augmentor, shape of the augmentor, etc. can
have a marked effect on the efficiency and performance. You might
want to contact Jack Morrison, he is on the Cozy list, about his
experience. I believe he was getting several inches of water
pressure when in ground taxiing operations with his augmentors.
I am
on the road right now, so I don't have his email address handy.
Bill schertz
I don't think they work well at idle Bill. Some sort of fan
will be required. One can put it on the prop which will
help mitigate the flat hub of the IVO or one can use an electric
fan.
However; If one wants to learn more about Ejectors one could
download these pdf files from the NACA-NASA web site:
http://ntrs.nasa.gov/search.jsp?N=17&Ne=2
<http://ntrs.nasa.gov/search.jsp?N=17&Ne=2>
Here is a partial list of pertinent papers known as "Ejectors".
1. An experimental investigation of rectangular exhaust-gas ejectors
applicable for engine cooling Manganiello, Eugene J Bogatsky, Donald
, NACA
Aircraft Engine Research Laboratory (Cleveland, Ohio., United
States) NACA
Report 818, 19 pp. , 1945
An experimental investigation of rectangular exhaust-gas ejector
pumps was
conducted to provide data that would serve as a guide to the design of
ejector applications for aircraft engines with marginal cooling. The
pumping
characteristics of rectangular ejectors actuated by the exhaust of a
single-cylinder aircraft engine were determined for a range of ejector
mixing-section area from 20 to 50 square inches, over-all length
from 12 to
42 inches, aspect ratio from 1 to 5, diffusing exit area from 20 to 81
square inches, and exhaust-nozzle aspect ratio from 1 to 42.
2. Preliminary investigation of cooling-air ejector performance at
pressure
ratios from 1 to 10 Ellis, C. W. , Hollister, D. P. , Sargent, A.
F., Jr. ,
Lewis Flight Propulsion Laboratory, Cleveland, Ohio. NACA Research
Memorandum E51H21, 23 pp. , 1951
Preliminary investigation was made of conical cooling air ejector at
primary
pressure ratios from 1 to 10. The cooling-air flow was maintained at
zero
and the resulting pressure variation in the shroud indicated pumping
ability. The cooling-air flow was maintained at zero and the resulting
pressure variation in the shroud indicated pumping ability. The
gross thrust
of the ejector and nozzle were compared. Several ratios of the spacing
between the nozzle and shroud exit to the nozzle exit diameter were
investigated for several shroud to nozzle exit diameter ratios. Maximum
gross thrust loss occurred under conditions of zero cooling-air flow
and was
as much as 35 percent below nozzle jet thrust. For minimum thrust loss,
ejector should be designed with as low diameter and spacing ratio as
possible.
3. Preliminary air-flow and thrust calibrations of several conical
cooling-air ejectors with a primary to secondary temperature ratio
of 1.0 I
:diameter ratios of 1.21 and 1.10 Greathouse, W. K. , Hollister, D. P. ,
Lewis Flight Propulsion Laboratory, Cleveland, Ohio. NACA Research
Memorandum E52E21, 26 pp. , 1952
An investigation of the performance of several conical cooling-air
ejectors
was made at primary jet pressure ratios from 1 to 10, secondary shroud
pressure ratios from 0.60 to 4.00, and a primary to secondary
temperature
ratio of 1.0. Primary air flow, secondary air flow, primary nozzle
thrust,
and gross ejector thrust were measured. The data are presented in
terms of
secondary to primary weight-flow ratio and gross ejector to primary
nozzle
thrust ratio. This phase of the investigation was limited to
ejectors having
shroud-exit to primary-nozzle-exit diameter ratios of 1.21 and 1.10 with
several spacing ratios for each. The experimental results indicated
that for
an ejector having a given diameter ratio, the spacing ratio for maximum
thrust was considerably less than the spacing ratio for maximum
pumping. The
smaller-diameter-ratio ejector produced less thrust loss at secondary
pressure ratios below 1.00 than did the large-diameter-ratio
ejector. The
data indicated that significant losses in gross thrust will occur if the
cooling-air flow is controlled by throttling in the upstream
secondary flow
passage.
4. Preliminary air-flow and thrust calibrations of several conical
cooling-air ejectors with a primary to secondary temperature ratio
of 1.0.
II :diameter ratios of 1.06 and 1.40 Greathouse, W. K. , Hollister,
D. P. ,
Lewis Flight Propulsion Laboratory, Cleveland, Ohio. NACA Research
Memorandum E52F26, 35 pp. , 1952
An investigation was made of the performance of nine conical cooling-air
ejectors at primary jet pressure ratios from 1 to 10, secondary
pressure
ratios to 4.0, and a temperature ratio of unity. This phase of the
investigation was limited to conical ejectors having shroud-exit to
primary-nozzle-exit diameter ratios of 1.06 and 1.40, with several
spacing
ratios for each. The experimental results indicated that the pumping
range
and amount of cooling-air flow obtained with a 1.06-diameter-ratio
ejector
were relatively small for cooling purposes but that the maximum
possible
thrust loss, which occurred with no secondary flow, was only 7
percent of
convergent-nozzle thrust. The 1.40-diameter-ratio ejector produced a
large
cooling-air flow and showed a possible thrust loss of 29.5 percent
with no
cooling-air flow. Thrust gains were attained with ejectors of both
diameter
ratios at secondary pressure ratios greater than 1.0. The limiting
primary
pressure ratio below which an ejector can operate at a specific
secondary
pressure ratio (cut-off-point) may be estimated for various flight
conditions from data contained here in.
Paul Lamar
How much heat do we have to get rid of? Maybe roughly 10% of the amount
at cruise power? What happens to heat exchanger efficiency at low flow
rates (water and air)?
What's Buly's idle RPM? Too high? Do you have to cary brakes while
taxiing downwind (beyond steering)?
Can a moveable cowl flap/vent be installed on the top of the engine
compartment to take advantage of convective flow? Maybe a blow-closed
style vent would be adequate?
A crude eductor/ejector/augmenter may flow enough air at idle to get
over the hump. It doesn't have to be perfect to be adequate.
It doesn't sound like Buly needs a dramatic improvement in ground
cooling - taxiing downwind is the only time he reports a problem.
Matt-
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