Here is a picture of the test set up. It is a closed loop system
with a ball valve using 1-1/2 ID pipe through out.
Well as I suspected there are some significant differences in the
closed loop system compared to the open loop system.
Kind of blew me away when I saw 40 GPM on the flow
meter with a wide open valve at only 2000 pump RPM.
With the valve partial closed (fully closed is 90 degrees)
the flows are as follows.
25 GPM and 15 GPM at 2000 pump RPM's see the pictures below.
The flow is a very sensitive function of the total restriction
in the system. At low RPM's small increases in restriction will
generate rapid losses in total flow. Pressure increases are
minimal. The highest pressure I have seen on the outlet of
the pump so far is about 3 psi.
At 4200 pump RPM wide open it pegged the flow meter at well over 75 GPM.
I adjusted the valve partially closed for 75 GPM at 4200 pump RPM and the
30
amp 110 volt circuit breaker blew in about 30 seconds.
I need to borrow a more powerful mill. No doubt about it these pumps
suck the HP. The pump gets quite warm on only a few seconds of running.
Paul Lamar
Paul,
We need you to generate a "pump curve" with your test setup.
1. At a given RPM, Close the valve totally, and measure the pressure head
generated by the pump. This is at zero flow.
2. begin opening the valve, and measure the pressure and flow values all the
wayup to full open and essentially no restriction.
You may be having a 'venturi' effect on your pressure guages that surround
the flow meter. Flow in the main pipe is whistling by the end of the
pressure guage, and could be sucking down the indicated pressure reading. I
noticed this on some of my early setups.
If your vertical standpipe were clear, then you could check your air-water
interface also.
The stock Mazda pump with no flow generated about 19 psi delta-P total head.
All pressure readings with flow (in my tests) have the pressure drop across
the block included, see attached
Next project but I am not going to be able to do that at 4200 RPM.
Apparently two Chinese horses are smaller than two American horses :)
I also need to get a pressure gage on the inlet side that reads both
positive and negative pressure. Next week.
The two pressure gages surrounding the flow meter were designed
to measure the pressure drop caused by the flow meter. I suspect it is
substantial.
Paul Lamar
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