Fan Cooling of Radials

[davparlr]

How much power does a coolant pump require?

 

[MIflyer]

This British wartime study by the RAE in December 1942, may provide some answers. Despite the power required to run the fan, it seems that (providing it runs contra-rotationally to the prop) a net gain in thrust is achieved.

Wow! Now that is fascinating! And as a Mechanical Engineer I hate to admit that I do not understand it. Does that mean equivalent power compared to just whatever the prop is doing in regards to forcing air in the cowling?

My WWII maintenance chief friend said that cuffs on props were meant mainly to streamline the primarily circular cross section of the base of prop blades but I could see how they could help force air down the radial engine cowlings. I think that cuffs were done away with except for the KC-97.

And I did see a cuff-like base extension on a light aircraft prop recently. I can only assume it was to shove more air into that flat-four cowl.

 

[rinkol]

I seem to recall that the PBM-3D Mariner had engine cooling fans to help with overheating in tropical climate. This was not retained in the PBM-5, which replaced the earlier R-2600 with an R-2800 and a longer, more streamlined cowling. Not sure what effect the fan or its removal had on performance

A relatively slow plane would require extra attention to cooling issues. I understand the AW Albemarles had a lot of trouble with the cooling of their Hercules engines in glider towing applications.

 

[Juha3]

Mitsubishi J2M Raiden also had an intake fan.

 

[pbehn]

A relatively slow plane would require extra attention to cooling issues. I understand the AW Albemarles had a lot of trouble with the cooling of their Hercules engines in glider towing applications.

That would be because it's engines were producing power to tow a glider not provide airspeed, like a fighter climbing, or like a Hawker Henley when towing targets.

 

[Rato Marczak]

I found this photo in the 1938 Aviation Year Book. Apparently, NACA was exploring the concept of 'air bleeding' cowling ring.

 

[Bretoal2]

I found this photo in the 1938 Aviation Year Book. Apparently, NACA was exploring the concept of 'air bleeding' cowling ring.

Yes. See Naca Technical report 595 (1937) and Technical note 720 (1939) about "NACA nose-slot cowlings".

And see, for special blower cooling with nose-slot (and others) NACA Special report 121 (July 1939).

Nose slot cowling was patented in France by Pierre-Ernest Mercier : patent 826 706, 1936/23/12, with many addendas in 1937 (05/02, 10/03, 29/07, 11/08 and 26/08) . The "Capot Mercier" or "capot à retour" were widely used in SNCASE LeO 451 and many others prototypes.

Regards

Alain

 

[z42]

(replying to this zombie thread as it was something I looked at recently, so just for posterity)

How much power does a coolant pump require?

A company that sells electric water pumps (EWP) for cars Frequently Asked Questions - Davies Craig mentions a max power draw of around 120 W. So increase by an order of magnitude for a big aero engine and you should be comfortably within single digit kW.

The deal with an EWP is that it can be run independently of the engine RPM, whereas a traditional belt driven one must be sized for the worst case scenario which is high load low rpm. But for an aero engine particularly with a constant speed prop such a situation shouldn't occur so a relatively smaller belt driven pump should be fine.

 

[SaparotRob]

Okay, not too much of a thread jack but something I wondered about.
Starting up my 4 banger on a cold day, how long would the car have to idle until the draw of the start was "compensated"?

 

[Deleted member 68059]

(replying to this zombie thread as it was something I looked at recently, so just for posterity)



A company that sells electric water pumps (EWP) for cars Frequently Asked Questions - Davies Craig mentions a max power draw of around 120 W. So increase by an order of magnitude for a big aero engine and you should be comfortably within single digit kW.

The deal with an EWP is that it can be run independently of the engine RPM, whereas a traditional belt driven one must be sized for the worst case scenario which is high load low rpm. But for an aero engine particularly with a constant speed prop such a situation shouldn't occur so a relatively smaller belt driven pump should be fine.

An example for a 2000hp aero engine is water pump power is 12.7kW

 

[z42]

An example for a 2000hp aero engine is water pump power is 12.7kW

Thanks, always good to have someone who actually knows their stuff!

A bit higher than I was expecting, though still (almost?) within shouting distance of my quick napkin math.

 

[Tom Fey]

Thanks for that, Calum. 12.7 kilowatts is 17 horsepower or about 1% of the 2,000 hp output at takeoff.

 

[Simon Thomas]

At the other end of the scale, the coolant pump power for the IOL-200 used in Voyager would have been around 0.25 hp. This is approx. 0.23% of takeoff power. Note that the IOL-200 was only liquid cooling the cylinder heads. The rest of the engine relied on oil for cooling.

"Design and Development of the Voyager 200/300 Liquid Cooled Aircraft Engine"

https://www.jstor.org/stable/44472934

Coolant flow rate was 13 gpm. Temperature rise across the head was 20°F. Pressure delta was 1 - 2 psi. Power was calculated assuming a centrifugal pump efficiency around 10%.