Subject: RE: Volvo poppet forces
Date: Sun, 16 May 1999 09:10:11 -0500
From: "Albright, Joe" <Joe.Albright@mts.com>
To: "Gram, Marty" <Marty.Gram@mts.com>
CC: "Lorenz, Josh" <Josh.Lorenz@mts.com>, "Chen, Hans" <Hans.Chen@mts.com>,
     "Saari, Byron" <Byron.Saari@mts.com>, "Kusner, Dave"
     <Dave.Kusner@mts.com>, "Larson, Rod" <Rod.Larson@mts.com>

Hi Marty,

Thanks for the flow force plots.  After looking at them, a variety of
other questions came to mind.  The most important question I believe is
why are there oscillations in the flow force/spool position, and how
much will they grow with larger poppet delta P.  That was my largest
concern when we started Toyota.  Thus far, we have only seen small
amplitude oscillations, at a relatively high frequency (>200 Hz).  So
far, so good.

The 990506 Volvo data shows cyclic delta P of more than 400 psi (10,000
lbs) on the return poppet.  The frequency is relatively low at 20 Hz.
The pressure poppet seems to be much lower in amplitude, although the
initial spike is similar in magnitude.  The basic frequency is similar
to the return poppet.  The return poppet also shows measurable poppet
position oscillation.  It has been our experience on Toyota that if you
can see the motion (when we had the LVDT), then you will definitely see
acceleration distortion.

My other questions relate just to better understanding the data, and
what it might indicate.  Would discussing them be worthwhile for you?
If so, I suggest that we meet and discuss, since I am sure there would
be real benefit in being able to look at the plots while we talk.  I
encourage the cc's to add any insights they may have on this issue.

Joe

> -----Original Message-----
> From: Gram, Marty
> Sent: Tuesday, May 11, 1999 2:46 PM
> To:   Albright, Joe
> Cc:   Lorenz, Josh; Chen, Hans; Saari, Byron
> Subject:      RE: Volvo poppet forces
>
> Joe --
>
> I think you are right about the 9 fold force increase with pressure
> versus the 3 fold that I suggested.  Forces should still be ok.
>
> Regarding the differences between the valves that could account for
> differences in flow forces; the width of the ends may be significant
> -- leading to the conclusion:  Wider is better!     I don't know how
> the flow distribution might change at higher pressures, but it did not
> seem to be a problem with UCSD and Watervleit.
>
> I will send you a copy of the plots by mail.
>
> --Marty
>
>       ----------
>       From:   Albright, Joe
>       Sent:   Tuesday, May 11, 1999 1:15 PM
>       To:     Gram, Marty
>       Cc:     Lorenz, Josh; Chen, Hans; Saari, Byron
>       Subject:        RE: Volvo poppet forces
>
>       Hi Marty,
>
>       Thanks for the update.  That sounds promising.  I would like to
> see some of the plots if practical.
>
>       Regarding what to expect at higher pressures, I just double
> checked in Merritt.  According to that reference, flow force is
> proportional to the pressure drop.  If that analysis is appropriate
> for your poppet, that would mean a 9 fold increase in flow force with
> a 9 fold increase in pressure drop.  Even at that increase you would
> still only be at about 36000 to 45000 lbs of flow force, which is less
> that 2000 psi delta P on you poppet.  Would that still work out OK for
> you?
>
>       Regarding possible errors in our measurement, I have thought
> about that many times, and don't see the error if there is one.  My
> conclusion at this time is that the flow force you measure will be
> very dependent on the end geometry of the poppet, and which pressure
> you feed to the back of the poppet.  One major difference between the
> Volvo poppet and the Toyota poppet is the large poppet end area that
> is on yours.  This presumably creates a larger surface area upon which
> the pressures will act.  My suspicion is that for your current tests
> the pressure has distributed favorably giving a low flow force.  Any
> thoughts on how it will distribute at higher pressure drops?
>
>       Joe
>
>               -----Original Message-----
>               From:   Gram, Marty
>               Sent:   Friday, May 07, 1999 4:17 PM
>               To:     Albright, Joe; Lorenz, Josh; Strand, Dick; Chen,
> Hans; Melander, Dan; Kusner, Dave; Gallagher, Steve; Saari, Byron;
> Larson, Rod; Hessburg, Thomas; Fullen, Mark
>               Cc:     Beduhn, Bill; Cohoon, Steve
>               Subject:        Volvo poppet forces
>
>               Poppet valve test results.  Good news.
>
>               On May 6, we ran a series of tests on the Volvo rear
> actuator.  In these test we kept the main pressure below 600 psi to
> avoid lifting the actuator off the floor.  We were able to flow 22000
> gpm through the valves in each direction and measure flow forces (we
> reached 28000 gpm when we opened the valves fast).  The valves have a
> 12" diameter poppet with a 25 sq in drive area --they are about 25%
> larger than the Toyota valve.  The Volvo valves were built without a
> flow deflecting "nose", and there is no insert in the center hole.  We
> use an LVDT to control valve position.
>
>               Flow force measurements were consistent with the flow
> forces measured on Watervliet and UCSD -- very low.  Flow force on the
> return valve was about 5000 lbf (flow in the same direction as
> Toyota).  Flow force on the pressure valve was about 4000 lbf.  The
> flow forces did not vary noticeably with valve opening.
>
>               When we run at full system pressure of 5000 psi, we
> expect the flows to increase by a factor of 3 and expect the flow
> forces to increase by the same factor.
>
>               Joe:  It may be worthwhile to revisit the Toyota valve
> flow force measurements.  Could the very high forces that you measured
> on the poppet be due to something other than flow force? --
> acceleration?  --effect of a loose LVDT?  --vibrations on the
> transducer?  --pressure taps seeing a venturi effect?
>
>               --Marty
>
