Paul,
Do we have anyone on this newsletter with experience with engine testing
within a hypobaric chamber? I am curious to know how they work.
I believe the chambers would have to have a means of blowing in fresh air
while sucking the exhaust out at a greater rate than the input air to keep
the chamber at partial vacuums.
With the Poor Mans hypobaric Chamber, PMHC, lets us say that our purpose is
to only test how much the recovery turbine increases in power at higher
altitudes. We won't have to test heat exchangers and electronics because we
are confident our over-designed systems will function well at high
altitudes. Yea right:) In any case the oil and water cooling is handled
remotely like on standard dyno set ups.
Background info:
A turbocompound engine must be boosted for the recovery of energy to occur.
Let us assume we want to test the traditionally turbocompounding method
first. In operation both a supercharger and blow down turbine are connected
to the drive shaft albeit in different locations. The supercharger is taking
energy from the drive shaft and the blow down turbine is putting that loss
and some 'plus alpha' power back into the shaft. In other words there is a
net gain. Sort of like 'compounded interest'
Testing:
First the supercharger. Factory test data curves showing power consumption
at different pressures and airflows can be confirmed by running the
supercharger connected to a large electric motor and confirming the results.
By the putting a torque arm on the free-to-rotate blower, and running it
through a manifold simulating the manifold resistance, the compressor
becomes the load. Temp., pressure, and air flows are documented as well.
Running the intake through a hypobaric (partial vacuum) chamber of lets say
a 10 cubic foot thick steel pipe with a control valve set on the intake set
to maintain a certain partial vacuum might work I think.
Second the exhaust.
Now imagine the exhaust pipe is connected to our test turbine and from
there into a another pipe hypobaric chamber. Connected to the outlet of
this pipe would be a blower which was reversed so as to suck. This powerful
vacuum unit will be driven by the same supercharge 25kW 3phase electric test
motor and interfaced with a vacuum sensor set to keep the exhaust hypobaric
chamber at 14.95" of Hg if we were simulating 18,000 ft. Running the test
in winter would give us our low STP intake temperatures.
Let me back up and say that this testing would be done only after the engine
is running stable and in the boosted conditions. Next the blowdown turbine
needs to be connected to a dyno. After the output is confirmed from
different turbines we can connect the best candidate to the drive shaft.
So what are we testing here? We can understand that at a given CFM of air
input, MAP, and altitude, how much power the blowdown turbine is putting
out. We hold the altitude and vary the MAP and/or RPM and note the results.
In short we know how the turbine's will perform at increasing high
altitudes.
Now if the goal was to test a turbochargers at altitude than this system
would work as well. We replace the supercharger, with a turbo charger and
compressor, and either a flexible shaft from the compressor to the dyno set
or the turbo exhaust to another blow down turbine and then dyno.
I would appreciate comment on any of these premises.
Sincerely
Doug in Japan
You could test at the top of Pikes Peak or mount Fuji.
Or you could rent Pratt & Whitney test chamber.
--
Paul Lamar ...No rotor no motor.
Paul,
The local gods won't let me test on Fuji and the drive to Pikes Peak is a
bit far:) The highest navigable road in Japan is about an hour from my
house and that is around 2800 meters or just shy of 9,000 foot. If I had the
engine at my place in Nepal I could just take put it in a truck and bring it
up to the border of Tibet. That pass is over 17K but presents a few other
logistical problems.
Doug in Japan.
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