I think it is time to take a look at the automotive water pump.

 There are 2 major types of pumps, centrifugal and positive

displacement, we are interested in the centrifugal group.



Within that group there are 2 types of designs; open impellor and closed

impellor. Open impellor are used in almost all automotive water pumps.

The open impellor type are used for their low cost of manufacture and

their relative ease of cleaning, should they become blocked.





The closed style is however far more efficient but is substantially far

higher in cost to produce, and far harder to clean if they become

blocked. Blockage in our situation is not a factor. Open style impellor

pumps are never used on flammable or explosive materials as the

clearance between the impellor and the volute can be reduced to zero by

thermal expansion. Automotive pumps run with very high clearances to

avoid the same problem, this makes them low efficiency.





We must now consider the application they are being used on.

In Industry the pump is designed around a set of parameters that suit

the customers requirements, and in general used at a constant speed.

In the case of the automobile and other internal combustion engines this

speed can vary considerably.







The automotive pump must be able to deliver sufficient flow at low rpm

and or low speed and high engine load to cool adequately.

 If you double the speed of this pump you require the cube in energy,

i.e. 2x2x2=8.





Consider an engine running at 2000 rpm at idle and then at 6000rpm or

higher as we do at cruise, the auto environment never for domestic use

run at so high rpm for any length of time.

You have increased the speed by a factor of 3, so now you require the

cube of 3, 3x3x3=27.







I have no argument with Pauls formulae for Volts x Amps = watts, and the

conversion between HP to Watts, what is in dispute is that you have

increased the rpm by a factor of 3 but have not increased the flow by

anywhere near that factor, but are consuming 27 times the power. You

could only possibly hope to increase the flow rate by a factor of 3 by

using variable geometry impellors and volute. This aint going to happen.





In any case to increase the flow by this amount and be able to exchange

3 times the heat is also not going to happen with a heat exchanger

designed to suit the output of the pump So where does this leave us.

It leaves us with a pump that is highly inefficient and a vast waste of

energy, but is acceptable to the auto manufactures, and where do you

think all that energy goes? Some is lost in slippage within the pump due

to high clearances, the higher pressure is able to pass easily to the

low pressure side thus reducing pumping efficiency, but the rest goes

into heating the cooling water!!!





 Some European car manufactures have woken up to this and are using

electric pumps, also many of the rotary racing boys here and probably

elsewhere are using electric pumps.

They consume a fraction of the power of a mechanical pump, but are

highly efficient.

I will be running an electric pump made by Davis Craig of Australia,

check them out.

I also Know of a tri rotor here in Tauranga that is a race car that has

run an electric pump for some years.



Andrew.  Campbell



   What kind of race car? What brand of electric pump? What size is the

fuse?



Paul Lamar





Hi!: thanks for the good info.



I'd always consider having hot water going out of block from the upper

part, then entering, as usual, radiator in its upper part, and the

return piping from lower radiator part, entering the low part of block

or housing, in order that, provided the case in pumping failures, no

wall in pipes exist, some Thermal-siphon effect always exists, making

liquid circulate.



is this a reasonable concern, or too childish, already implemented from

very early times?



Regards, Salut †



Jose Gros-Aymerich



 Madrid, Spain



The liquid cooled aircraft engines of WW II have pump impellers that

look just like

the pump impellers available today. Therefor the same pump HP needed per

prop HP

out is the same. The Mazda impellers have proven to be effective in

aircraft use. Use a smaller impeller or less pump HP at your own peril.



If you want to try  an electric pump  use a small starter motor.

 They will develop 3 HP at 200 amps out of the battery.

You will need two alternators :-) I know of no car alternators that will put

out 200 amps. There may be one out there but check the weight :-)



Paul Lamar



A starter motor is not designed for continuous duty, and will likely burn up in about 10 min of use.

Craig. Smith


I agree. I know that:-)  Just an illustration.

Maybe it could be water cooled :-)

Paul Lamar


Whilst on the subject of cooling, is there any value in routing the water from the radiator to a (aluminum) centre housing, to direct the coolest water to the spark plug? Could it possibly cause stress cracking of the rotor housing or even retard the flame front? Your thoughts/ Knowledge requested.

Vern Taylor

Darwin (Aus)


Vern are you using a cell phone? It sure screws up a forwarded message.
What brand is it?

The early Power Sport did some experimenting on that but apparently it did not help enough
to make it worthwhile converting the Mazda.

If I were doing new end housing I would certainly use it. The early NSU Wankel Spider had rotor
housing cracking problems so that might be the cause. I would think you might
have to warm it up before applying full power.

Unlikely to retard the flame front in a windy combustion chamber or any combustion chamber for
that matter :-). You would probably need more than a 3 HP water pump :-)

Paul Lamar

The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove  you.  ACRE NL web
site. http://www.rotaryeng.net You Tube http://tinyurl.com/beqqxas
Copyright 1998-2017 All world wide rights reserved.