The subject of electric  water pumps keeps coming up once a year more
 or less for the last 10 years so I finally got around to writing an
 article on it and uploading it to the web site. Please read.


 http://www.rotaryeng.net/electric-pumps.html

 Paul Lamar


Hi Paul,

Nice article. I would read a bit easier if you had both USA units and SI unit
alongside  :-)

If one looks for efficiency, using an inefficient alternator is a good way to
start doing things wrong. The European alternator efficiency initiative tries to
change things in here. There are very promising leads. By the way you will find
some interesting info on alternators on [missing link]

Matching the pump delivery with engine requirement is however an important job
to get better efficiency. Keeping it mechanically linked seems good to me so you
avoid efficiency losses of alternator. A variable flow pump is quite elegant and
BMW has made nice demonstration of such with its oil pump. You could try finding
the right pump for your rotary.

For airplane applications i have a strong impression that the engine is
relatively often at the same power level and would require relatively constant
power in coolant delivery.
The dimension of automotive pump would probably not be adapted and one could try
to find the right pump. Does it really need adaptability in coolant flow in a
plane then?

About pump internals: Have you looked at racing pumps for high efficiency
versions? These might be slightly better.
The stamped sheet pumps work but have not optimal efficiency. Look at design of
BMW electric water pump below. The plastic impeller should have good
hydro-dynamic properties. However I wonder how efficient the electric motor is
as shown in photo below.

Another way to get better efficiency from cooling systems is related to radiator
aerodynamics. If the engine is designed to run at high coolant pressure and
temperature the pressure could be increased to 6-7 bar so it can run at 140-150
deg C. The heat transfer from radiator to air is higher and its size can be
reduced. This has been applied in Formula 1 until it was banned. You know more
than anyone else that F1 rules are written to have utterly inefficient cars  :-)

For planes that have high average cruising speeds and relatively important
aerodynamics component compared to road cars this makes sense to me.


Randolph Toom
Managing Director
heat2power

7 Rue Adolphe Focillon
75014 Paris - France

Thanks
Do you have a larger picture of that power train Randolf?

Paul Lamar

Randolph


Very nice pump design.  I don't think the  plastic impeller will last
very long though.  Most of the BWM enthusiasts have changed their
plastic impeller pumps out for the  Stewart Components stainless one.
Making it out of stainless allowed for tighter machining tolerances and
better performance.

Good call on running higher pressures.  Radiator construction and hose
connections then become paramount.

Doug in Japan.