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flow rate of the oil question


glen english LIST
 

What is the flow rate at the oil pump in a Jabiru in cruise ops

approx?

(for some rpm/temperature condition)

-glen


David Amsler
 

On my bench test with the stock Jabiru 4 lobe pump for a 3300 engine, at about 50 PSI,  total flow was about 25 L per min or about 6.5 gallons per minute at 3300 RPM.  That is total from the pump, less than that will go through the PRV, still it is a lot of oil.

David A.

On Thu, Feb 11, 2021 at 3:40 PM glen english LIST <glenlist@...> wrote:
What is the flow rate at the oil pump in a Jabiru in cruise ops

approx?

(for some rpm/temperature condition)

-glen






glen english LIST
 

thanks David

I was doing the numbers to what oil flow would be required if flooding of the rocker compartments was done for additional cooling.

If the maximum amount of cooling was to be done with the available head surface area (does not include the cover of course, we are removing heat from the head material) - which is about 550 Watts , the flow (for each) needs to be changed at a rate of 4x per second ! or a flow of >= 19 litres per minute ...

On 2/12/2021 8:00 AM, David Amsler wrote:
On my bench test with the stock Jabiru 4 lobe pump for a 3300 engine, at about 50 PSI,  total flow was about 25 L per min or about 6.5 gallons per minute at 3300 RPM.  That is total from the pump, less than that will go through the PRV, still it is a lot of oil.
David A.
On Thu, Feb 11, 2021 at 3:40 PM glen english LIST <glenlist@cortexrf.com.au <mailto:glenlist@cortexrf.com.au>> wrote:
What is the flow rate at the oil pump in a Jabiru in cruise ops
approx?
(for some rpm/temperature condition)
-glen


glen english LIST
 

Thanks David

On cooling options:

The surface area available in the rocker compartment in contact with the meat of the head - there is useful surface area of 8000 mm2

Let's assume a layer between the metal and the cool oil of 80 deg C of 0.1mm. It will be turbulent, not laminar.

If the oil circulating is 90 deg C, and the metal temp is 150C, we have 60deg difference

The thermal conductivity of oil is about 0.15 W/mK
which gives us a maximum heat flux of q= -kdeltaT(grad) per sqM
= 90kW per m2, (9W/cm2) or about 720W for our 8000mm2. Not much.

Due to the irregular shape, we can probably manage 50% of that, so 360W.

The specific heat capacity is about 1600J/kg or about 1750J/litre.
For 360J/sec , that is 360/1750 = 0.205 l per second, or about 12 litres per minute (per rocker compartment). Quite alot.

Estimated head heat power per pot at maximum output is 4.5kW.

Our 9W/cm / delta T of 60
= 0.15W/cm2.K is about the middle of the chart for oil based convection cooling.

If we just boiled water (like the cyl-head forming the the bottom of a saucepan of water), about 2W/cm2.K are expected.

If optimized spray vapour phase cooling of water we could expect up to about 6W/cm2.K with no special techniques.

In contrast, our forced air convection is good for 0.06 W/cm2.C at best.
so we need about 750cm2 per pot for 100 C rise and heaps of airflow.

Extended hot weather ground running solution is probably as simple as a fine mist spray in the front of the ram duct. at say 1/3 max dissipation of 1.5kW per pot, that , per second, 600uL of water , or 36mL per minute, per pot. About 1/4 of that will actually do its job if just fired in the front duct inlets so 40mL x 4 x 6 pots = 862mL/minute.

If the sprayer were over the top of the cylinder heads, spray velocity high enough to that half if the water actually hits the fins and doesnt pass straight through, we could expect 2x I think, so 430mL/m for the 6 cylinders. So for the vapor phase to work well, haphazardly blowing droplets of water through fins isnt that great.

Because of the small area required to do the vapor cooling job, the best water efficiency would be a spray bar in the fins at the roots of the fins near the CC. Now we might approax 75%.

Hmm !

what about an open oil bath over all those fins ? The spark plugs can be immersed of course, oil is a great high voltage dielectric.
Back to our 0.15W/cm2/K, 4500 W needs 500 cm2 to do the job.

We easily have 1344cm2 with 1/2 of the finning.

Problem is it needs flow. there are no gaps between the cylinders which makes it hard. fiddly to retrofit

So my forced air cooling jackets are still my best solution I think.

On 2/12/2021 8:00 AM, David Amsler wrote:
On my bench test with the stock Jabiru 4 lobe pump for a 3300 engine, at about 50 PSI,  total flow was about 25 L per min or about 6.5 gallons per minute at 3300 RPM.  That is total from the pump, less than that will go through the PRV, still it is a lot of oil.
David A.
On Thu, Feb 11, 2021 at 3:40 PM glen english LIST <glenlist@cortexrf.com.au <mailto:glenlist@cortexrf.com.au>> wrote:
What is the flow rate at the oil pump in a Jabiru in cruise ops
approx?
(for some rpm/temperature condition)
-glen