Odd Sensor Design

[Richard]

You say this is turbocharged with an intercooler, so you must be running
some serious boost. So my question is does the turbo still work when it
starts leaking oil?

About 20 psig Boost, When the turbo starts leaking while running it very
little oil, a small enough amount that the engine will actually burn it and
never look back, when the unit goes down, any accumalated oil starts
draining into the intake manifold, which is a integral part of the engine
(Built into the V of the engine).


If so, you could install a small tube that rests on the

bottom of manifold or aftercooler, and have the tube drain at the top in a
tall, skinny container with a float switch. As long as the tube is small
enough, or long enough, very little of the boost pressures would escape. I
would also be looking for some way to make it drain, even if it requires
modifying the intake/intercooler (remember under boost it can be forced to
go in any direction). Also, what about measuring the oil level in the
sump?

We do have high low level shutdowns on the engine oil sump, with automatic
make-up controllers. However, a quart of two of oil in the manifold on a
large sump like this isn't hardly measurable, so if we set the oil level
switch that close, we would be going down on a pretty routine basis on false
level problems.

If it drops significantly in a short time, something is wrong. You could
also supply oil to the turbocharger from it's own source, with a electric
pump. The oil supply could have limited amounts of *pumpable* oil, say 250
ml, or an accurate level gauge. This gives the advantage of running
special
oils in the turbo bearings separately from the engine, and being able to
keep the oil for the turbo relatively pure and easy to change. And, being
able to keep oiling to the turbo while it's still spinning, long after the
engine is shut down. A pressure switch can be incorporated to prevent
turbo
seizure if the oil stops flowing by shutting the engine down.

A excellent point. And a very costly one. Seperate pumps, tanks, oil

coolers. Most likely the reason the manufacturer doesn't do it. But again,
a $100,000 failure versus a Completely new Turbo oiling system, hum, may
have merit.

Again, thanks for the ideas.
Richard




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[nospam]

"Richard" <rwskinner ATawesomenet Dot net> wrote:

What we're looking for, is some sort of sensor that can detect presence of
oil in the intake manifold. Oil can reach up to a 1/4" deep. We have a
port we can screw into, now we have to determine the best way of detection.

One of my old cars (can't remember which) had an oil level sensor built
into the dipstick.

I searched around the web/usenet looking for comments about oil level
warning lights and dipstick and found almost nothing - so I guess they are
either pretty rare or pretty reliable .

I don't know how it worked but suspect the only realistic options are hot
wire and optical.

I have seen the odd reference to optical oil level sensors using a prism.
I suspect when you immerse a prism in a liquid with about the same
refractive index it isn't a prism any more and you can detect the lack of
refraction or something like that.

Either way I suspect you will have to mount the sensor in a bit of a well
to collect oil and give you more than 1/4" maximum depth.

 

[Richard]

Lots of great feedback and I appreciate each and every one of them.





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[Richard]

Thermistors are good for this sort of work - read their resistance when
they are dissipating 10uW (0.01C of self-heating in air) and again at
1mW (1.0C of self-heating in air) and if you can't detect a 4% lower
resistance at the higher dissipation, the thermistor is immersed in oil
or water ...

Betatherm make mounted thermistors specifically for this sort of job

I like this idea. But maybe you can help clarify. Since the engine manifold
temperature can vary so much, wouldn't that also screw up our known
resistance or cause a large variance as well? Or is the self heating temp
higher than what we would expect to see in the manifold? Manifold would
vary from say 90F to 180F.

If so, then would that require two sensors. Measure the one in raws
air/gas, versus the one that may be covered in oil?

Then last, if the oil level may only get 1/8" to 1/4" deep, do some of these
sensor measure from the Tip only, and would that be accurate enough?

Again, thanks for the ideas.
Richard




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[jtaylor]

"Richard" <rwskinner ATawesomenet Dot net> wrote in message
news:41ecfca5$1_2@127.0.0.1...

We have an engine model which is prone to a particular problem. When the
engine goes down after it fails a turbo charger, it slowly fills the
aftercooler and intake manifold up with oil. When the engine shutsdown,
the
aftercooler drains the oil into the manifold. When a operator tries to
restart the engine, the cylinders fill up with oil (only after it actually
starts) then hydro locks and spits a connecting rod out the side of the
block. {yes, the engine generally starts fine with no hydrolock until it
starts coming up to speed, then it sucks the oil in and BAM!}

"when it fails a turbo charger" - what does this mean - does the turbo
break?

If it does break, you could detect that, couldn't you? Put some kind of
interlock so if that happens the thing won't start.

 

[Pat Ford]

"jtaylor" <jtaylor@deletethis.hfx.andara.com> wrote in message
newsZsHd.89015$vO1.544052@nnrp1.uunet.ca...

"Richard" <rwskinner ATawesomenet Dot net> wrote in message
news:41ecfca5$1_2@127.0.0.1...
We have an engine model which is prone to a particular problem. When
the
engine goes down after it fails a turbo charger, it slowly fills the
aftercooler and intake manifold up with oil. When the engine shutsdown,
the
aftercooler drains the oil into the manifold. When a operator tries to
restart the engine, the cylinders fill up with oil (only after it
actually
starts) then hydro locks and spits a connecting rod out the side of the
block. {yes, the engine generally starts fine with no hydrolock until
it
starts coming up to speed, then it sucks the oil in and BAM!}


"when it fails a turbo charger" - what does this mean - does the turbo
break?

If it does break, you could detect that, couldn't you? Put some kind of
interlock so if that happens the thing won't start.

Maybe talk to an aircraft maintainence engineer about how they do the
lockout on a turbine engine after a seal failure.
Pat

 

[Frithiof Andreas Jensen]

"Richard" <rwskinner ATawesomenet Dot net> wrote in message
news:41ee4f81$1_1@127.0.0.1...

A excellent point. And a very costly one. Seperate pumps, tanks, oil
coolers. Most likely the reason the manufacturer doesn't do it.

Hmmmm -

My long-sold Renault Espace 2.1 TDi had a separate oil pump for the Turbo to
keep the oil flowing for minutes after the engine switched off to cool those
Turbo bearings. Cars usually epitomize "Cheap".

 

[Guy Macon]

I think he should run a thin aluminum tube to wherever he was
thinking of putting the sensor and have a pump pump out any
oil that has collected. Have it run for X amount of time as
part of the startup sequence.

 

[CBarn24050]

Subject: Re: Odd Sensor Design
From: "Richard" rwskinnerATawesomenet Dot net
Date: 19/01/2005 12:42 GMT Standard Time
Message-id: <41ee56bb$1_2@127.0.0.1


Thermistors are good for this sort of work - read their resistance when
they are dissipating 10uW (0.01C of self-heating in air) and again at
1mW (1.0C of self-heating in air) and if you can't detect a 4% lower
resistance at the higher dissipation, the thermistor is immersed in oil
or water ...

I like this idea. But maybe you can help clarify. Since the engine manifold
temperature can vary so much, wouldn't that also screw up our known
resistance or cause a large variance as well? Or is the self heating temp
higher than what we would expect to see in the manifold? Manifold would
vary from say 90F to 180F.



If so, then would that require two sensors. Measure the one in raws
air/gas, versus the one that may be covered in oil?

No, you measure the differential temp diference which compensates for the
ambient.

Then last, if the oil level may only get 1/8" to 1/4" deep, do some of these
sensor measure from the Tip only, and would that be accurate enough?

The 1 I made would easily measure 0.5 mm.

 

[Frithiof Andreas Jensen]

"Pat Ford" <pat.ford@nrc.ca> skrev i en meddelelse
news:cslqtv$sm5$1@nrc-news.nrc.ca...

They Dont!!!

They do! a PT6 wont start without someone reseting a mechanical lock if
the
turbin play is out of spec!

You are correct the engine wont shutdown if flight but it will not start
after certain turbine faults.
Pat

Thanks for the correction - I am not an aircraft engineer ;-)

 

Your Nichrome wires are doing the same job as thermistors, but with
much lower sensitivity to the temeprature differences you are trying to
detect. Thermocouples don't normally dissipate any power at all, so
they would be perfectly useless.

You don't need two sensors - if you measure the the self-heating of a
single sensor at two different current levels in quick succession (the
time constant of a bare thermistor is about a second) you've got all
the information you need.

----------------
Bill Sloman, Nijmegen

 

[Mike Fields]

"Richard" <rwskinner ATawesomenet Dot net> wrote in message
news:41ee4c68$1_1@127.0.0.1...

Hmm. Remember the intake manifold is under a variable vacuum -
getting oil to flow into a resevoir (especially from an area of high
turbulence) may not be as simple as it sounds.

Also the OP has stated there is no room for fittings and hoses.

Fitting everything through a 0.25" orifice is a bit constraining (kind
of like being a feline gynecologist, I suppose). But that's what makes
it fun.

Well, I'm going to check back - this is my third post to this thread in
about five minutes - but my suggestion is, diagnose what's pumping the
oil into the manifold in the first place, and fix that. Band-aids suck.

Good Luck!
Rich


Oh, that is the easy part. Again, a turbo charger is prone to extreme
temps
and speeds, they all wear out. Yes, prevenative maintenance can eliminate
much of this by taking axial and radial clearance measurements on a
routine
basis and change "before" a failure, but not failures give you such an
advance warning.

Kind of like having a blow out on your vehicle. Sometimes you can prevent
it by keeping an good eye on your tires and properly maintaining them,
other
times, it just happens. When it does, well, hopefully you can pull over
and
change the tire, or to some people, they loose control and drive off a
cliff.

I don't consider a safety shutdown to save a $100,000 engine as a bandaid,
besides, there are approx. 40 total safety shutdowns for one of these
engines. Surely they aren't all considered bandaids. They are there to
shut the engine down in case something is abnormal or something breaks.
Since they are industrial engines and run un-manned they are needed.

I guess we could take all the safeties off, and then have Cat build a
perfect engine. Heck, then we wouldn't need technicians <grin>.

RS

I remember seeing some liquid sensors in the past that consisted of a
LED/Photodiode pair on the end of a piece of plastic rod with a
"wedge" at the other end arranged so the light from the led went down
the rod and was reflected by the two sides of the wedge back to the
photodiode. When the end of the probe was immersed in a liquid with
a similar index of refraction, the light quit reflecting back and could
be detected as "fluid present". Perhaps something along that line ??

mikey

 

[Paul Hovnanian P.E.]

Guy Macon wrote:

I think he should run a thin aluminum tube to wherever he was
thinking of putting the sensor and have a pump pump out any
oil that has collected. Have it run for X amount of time as
part of the startup sequence.

This solution seems to be the best approach. If you know where the oil
will pool and can get a sensor to that location, why not put in a pickup
to clear it?

The system could be designed with an orifice and some method of
measuring the pressure drop across it to detect when it was drawing in
oil or just sucking air. This signal would keep the evacuate pump
running and inhibit engine starting.

The advantage of such a system is that it would (eventually) allow the
engine to be restarted after the sensor had determined that the oil had
been evacuated.

I think a few people have suggested variations on this approach already.

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
Bloody typical, they've gone back to metric without telling us.

 

[Rich Grise]

On Wed, 19 Jan 2005 12:00:34 +0000, Goran Larsson wrote:

In article <pan.2005.01.19.04.03.38.576440@example.net>,
Rich Grise <richgrise@example.net> wrote:

Wouldn't "eliminate the problem at source" involve something more akin to
determining what design flaw is putting the oil in its wrong place first?

The OP wrote that the oil problem is caused by a failed turbo. The
bearings in a turbo is commonly an oil bearing and if the bearing seals
break the turbo will leak oil into the air ducting, e.g. the wrong
place. Things do break in real life and failures aren't always caused
by a design flaw.

Ah. Thanks for this. Then, I'll just get in the "drain hole" line. ;-)

But a sensor that says that the turbo's bearings have failed, so that you
can turn it off before it destroys more stuff, that's an
interesting problem. Temperature? Pressure at the feed? I guess
capacitative would be the least intrusive.

Good Luck!
Rich

 

[Rich Grise]

On Wed, 19 Jan 2005 05:58:13 -0600, Richard wrote:

Hmm. Remember the intake manifold is under a variable vacuum -
getting oil to flow into a resevoir (especially from an area of high
turbulence) may not be as simple as it sounds.

Also the OP has stated there is no room for fittings and hoses.

Fitting everything through a 0.25" orifice is a bit constraining (kind
of like being a feline gynecologist, I suppose). But that's what makes
it fun.

Well, I'm going to check back - this is my third post to this thread in
about five minutes - but my suggestion is, diagnose what's pumping the
oil into the manifold in the first place, and fix that. Band-aids suck.

Good Luck!
Rich


Oh, that is the easy part. Again, a turbo charger is prone to extreme temps
and speeds, they all wear out. Yes, prevenative maintenance can eliminate
much of this by taking axial and radial clearance measurements on a routine
basis and change "before" a failure, but not failures give you such an
advance warning.

Kind of like having a blow out on your vehicle. Sometimes you can prevent
it by keeping an good eye on your tires and properly maintaining them, other
times, it just happens. When it does, well, hopefully you can pull over and
change the tire, or to some people, they loose control and drive off a
cliff.

I don't consider a safety shutdown to save a $100,000 engine as a bandaid,
besides, there are approx. 40 total safety shutdowns for one of these
engines. Surely they aren't all considered bandaids. They are there to
shut the engine down in case something is abnormal or something breaks.
Since they are industrial engines and run un-manned they are needed.

I guess we could take all the safeties off, and then have Cat build a
perfect engine. Heck, then we wouldn't need technicians <grin>.

Yes, thanks, I've finally clued in on that, in another branch. My little
voice is saying, "pressure sensor in the supply line", which might or
might not even be worth bringing up, but hey, when you're out of your
league, you bluff, right? ;-)

Thanks!
Rich

 

[Guy Macon]

Rich Grise wrote:

But a sensor that says that the turbo's bearings have failed, so that you
can turn it off before it destroys more stuff, that's an
interesting problem. Temperature? Pressure at the feed? I guess
capacitative would be the least intrusive.

Acoustic? Do failed turbo bearings make noise or vibration?

RPM? Do turbos with bad bearings run slower or spin up slower?

 

[Rolavine]

Subject: Re: Odd Sensor Design
From: "Jeff" levy_jeff@hotmail.com
Date: 1/18/05 10:19 PM Pacific Standard Time
Message-id: <SZmHd.214239$Np3.8997542@ursa-nb00s0.nbnet.nb.ca


"Richard" <rwskinner ATawesomenet Dot net> wrote in message
news:41ecfca5$1_2@127.0.0.1...
We have an engine model which is prone to a particular problem. When the
engine goes down after it fails a turbo charger, it slowly fills the
aftercooler and intake manifold up with oil. When the engine shutsdown,
the
aftercooler drains the oil into the manifold. When a operator tries to
restart the engine, the cylinders fill up with oil (only after it actually
starts) then hydro locks and spits a connecting rod out the side of the
block. {yes, the engine generally starts fine with no hydrolock until it
starts coming up to speed, then it sucks the oil in and BAM!}

This is an industrial engine, which runs un-manned 24/7 and has a
shutdown/safety panel. We have several hundred of them.

What we're looking for, is some sort of sensor that can detect presence of
oil in the intake manifold. Oil can reach up to a 1/4" deep. We have a
port we can screw into, now we have to determine the best way of
detection.

Since oil is a pretty good insulator, it will have an affect on what type
of
sensor to use or design. Items we thought of....

Float style or tip level sensor - Hard to read a 1/4" level
Small, low temp hot wire, measure the current, if submerged in oil it may
change, vrs air/gas mixture
Capacitance measurement? - Possibly the best method???

The method can not cause combustion of a combustable mixture.
We have 24 vdc on skid.
Normal shutdown method is to pull down inputs from our panel (3.3 vdc TTL
with pull ups) grounding an input forces it low thus a fault.

Any clever ideas for this one?

Richard


You say this is turbocharged with an intercooler, so you must be running
some serious boost. So my question is does the turbo still work when it
starts leaking oil? If so, you could install a small tube that rests on the
bottom of manifold or aftercooler, and have the tube drain at the top in a
tall, skinny container with a float switch. As long as the tube is small
enough, or long enough, very little of the boost pressures would escape. I
would also be looking for some way to make it drain, even if it requires
modifying the intake/intercooler (remember under boost it can be forced to
go in any direction). Also, what about measuring the oil level in the sump?
If it drops significantly in a short time, something is wrong. You could
also supply oil to the turbocharger from it's own source, with a electric
pump. The oil supply could have limited amounts of *pumpable* oil, say 250
ml, or an accurate level gauge. This gives the advantage of running special
oils in the turbo bearings separately from the engine, and being able to
keep the oil for the turbo relatively pure and easy to change. And, being
able to keep oiling to the turbo while it's still spinning, long after the
engine is shut down. A pressure switch can be incorporated to prevent turbo
seizure if the oil stops flowing by shutting the engine down.

I supose you've considered using opto electronics?

Rocky

 

[Richard]

I'm thinking, thermal (wouldn't the un-oiled bearings get terribly hot,
quite quickly?) or a pressure sensor, but don't know what the pressure
characteristics of a turbo with unblown/blown seals are. An abrupt drop in
feed pressure could be an indication, for the price of one tapped hole and
an oil pressure sender, and electronics that'd keep this group occupied
for about three minutes. ;-)

We have thermocouples already on the turbo. Normally a seal failure doesn't
show an increase in temp because the turbo is still getting plenty of oil,
the problem is, the oil is put into the intake system instead of being
returned to the sump.

Pressure gets pretty hard to measure as well, bearing clearances are small,
so a seal failure doesn't show a pressure drop due to the pressure and
volume of the oil going to the turbo. Seals are after the pressure drop or
clearance of the bearing. Think about a center oil cavity, a bearing on the
left and right (Sleeve) and then the seals on the very outside. Drain holes
from between the bearings and seals for return oil to the sump.

Installing a restrictor in there then reduce the oil flow enough to measure
the pressure drop? Already has restrictors, but the less oil (GPM) to the
turbo then the risk of damage increases, plus the temperature increases (at
the bearing) not the turbo. Again, Unless the bearing totally wipes out, it
would not be detected anyway by oil pressure. A 800 deg.F turbo is very
difficult to acutally measure the bearing temp, best bet is to measure the
oil temp leaving the turbo to determine temp at the bearings. Ahhh, but if
there was "no" oil returning then you could tell by the lack of temperature,
but that is blown out of the water because we are pumping a high volume to
the turbos, in the even of a seal failure, huge amounts of oil still flow to
the sump, however some goes into the intake.

Beleive me, I'm pretty darn creative and we have ruled out all (Sorry -
Most) simple solutions. We have already thought of the pump with a tube,
with an orifice at the end, the oil would cause a high deltaP as gas would
not.

We thought of drain tubes, just no low place to get to. Temps, pressures,
and Starter Slip Clutches. Starter slip clutch doesn't work either.
Manifold fullof oil, doesn't flow into the cylinders until the engine is
"restarted" as the engine is reving up, it then sucks the oil out of the
intake into the cylinders, then Wam!

We really like the idea of the tuning fork design, but not sure how it will
operate inside a running engine. Seriously looking into thermistors and
also capacitance sensors.

any way we go, it will have to be a permissive start or lock out.

Again, tons of good ideas, we have to see which combination would come
closest to working.
Nice, long, interesting thread huh? <grin>

Richard




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[Rolavine]

Subject: Re: Odd Sensor Design
From: Rich Grise richgrise@example.net
Date: 1/20/05 6:34 PM Pacific Standard Time
Message-id: <pan.2005.01.21.02.39.33.435111@example.net

On Thu, 20 Jan 2005 00:44:09 -0800, Paul Hovnanian P.E. wrote:

Guy Macon wrote:

I think he should run a thin aluminum tube to wherever he was
thinking of putting the sensor and have a pump pump out any
oil that has collected. Have it run for X amount of time as
part of the startup sequence.

This solution seems to be the best approach. If you know where the oil
will pool and can get a sensor to that location, why not put in a pickup
to clear it?


Wow, Guy that is pretty good, I think he should do that. Not only can they save

the engine but they can detect the problem too. Since the start up may have a
manual procedure, maybe they could just use a hand pump. If they suck more than
a few ounces of oil they know the bearings are shot. Heck, they could just put
in a dip stick to check first.

Rocky

Rocky

 

[Paul Hovnanian P.E.]

Richard wrote:

[snip]

We thought of drain tubes, just no low place to get to. Temps, pressures,
and Starter Slip Clutches. Starter slip clutch doesn't work either.
Manifold fullof oil, doesn't flow into the cylinders until the engine is
"restarted" as the engine is reving up, it then sucks the oil out of the
intake into the cylinders, then Wam!

We really like the idea of the tuning fork design, but not sure how it will
operate inside a running engine. Seriously looking into thermistors and
also capacitance sensors.

If you don't know where the oil might be pooling inside the manifold,
there may be no sensor solution that will suffice.

Is there someplace between the turbo and the intake manifold that the
oil leak might be intercepted and/or detected? From your original
problem description, it sounds like the problem is caused by a volume of
oil pooling in the intercooler and manifold after the engine shuts down.
Oil that leaks during engine run just runs through and gets burned off.

Can you put a 'low spot' between the turbo and the intercooler to give
the oil a place to collect before it reaches the manifold?

--
Paul Hovnanian mailtoaul@Hovnanian.com
------------------------------------------------------------------
Plaese porrf raed befre postng.