Compressor Digitization

[aerospacian]

hi i m new to lab view.actually i want to digitize a air compressor using DAQ card and Lab view.there are 10 tubes wchich are coming out from the compressor at different stages containing air in them.initially there were inserted in pressure manometer now i want to replace manometer with a computerize software.kindly help me over this issue.

Actually i only know about the pressure readings coming out on Manometer panel whose range is between 3-16 inches of water where 1 inch of water = 5.2 psf

this axial flow compressor is having three stages of rotors and stators.A LP compressor is attached with it to provide it constant 80 psig pressure for its cooling.

The 3-stage compressor sucks in atmospheric air (air pressure is 1 atm = 14.7 psi) and after passing through 3 stages of rotors and stators it gives out pressure reading on manometer panel via small rubber tubes installed at different locations on the axial flow compressor.

kindly help me out now for choosing relevant pressure transducer and DAQ card to digitize this apparatus so that there will be no need of Manometer Panel instead of Software based PC giving final results.

thanx a lot..

[aerospacian]

hi i m new to lab view.actually i want to digitize a air compressor using DAQ card and Lab view.there are 10 tubes wchich are coming out from the compressor at different stages containing air in them.initially there were inserted in pressure manometer now i want to replace manometer with a computerize software.kindly help me over this issue.

Actually i only know about the pressure readings coming out on Manometer panel whose range is between 3-16 inches of water where 1 inch of water = 5.2 psf

this axial flow compressor is having three stages of rotors and stators.A LP compressor is attached with it to provide it constant 80 psig pressure for its cooling.

The 3-stage compressor sucks in atmospheric air (air pressure is 1 atm = 14.7 psi) and after passing through 3 stages of rotors and stators it gives out pressure reading on manometer panel via small rubber tubes installed at different locations on the axial flow compressor.

kindly help me out now for choosing relevant pressure transducer and DAQ card to digitize this apparatus so that there will be no need of Manometer Panel instead of Software based PC giving final results.

thanx a lot..

[GerdW]

Hi,

the aerospace industry still don't uses any of those worldwide standardized SI units?

No wonder all those planes crash regularly...

Doh!

Beside of that:

Just call your local NI sales guy to get information about suitable DAQ hardware!

[Dave_Karon]

aerospacian,

good luck with your research project.

With a bit more information, we may be able to make some better suggestions for you.

It is not clear what you are trying to do.  If you are only interested in pressure rise, that is one thing. 

If you are trying to assess compressor performance you will need more than the pressure measurements.

You also do not say whether you are interested in quasi-steady pressures or you are interested in the time-varying nature of the pressures.

Presumably, since you are presently using manometers, you are interested in the quasi-steady pressure values

As far as instrumentation, you can replace your manometers with appropriate pressure transducers and measure their signals with an NI low cost multifunction DAQ device.

I would suggest that you contact your local vendor of transducers.  In the US, there are many choices, but I think you mentioned in another post that you are located in Dubai, so perhaps some of our US based vendors are not available there.

[aerospacian]

I m interested in compressor performance and quasi pressure is used too.but there are many types of pressure transducer.i-e over pressure,differential,absolute pressure transducer etc.so which one is suitable for me in this case.

[Dave_Karon]

If you want to measure compressor performance, you must measure certain quantities:

1. Inlet pressure and inlet temperature. You must do this to determine fluid properties.

2. The pressures and temperatures used form your performance calculations must be absolute, so kPa and K.

   You don't have to do that in one step, though. You can make a separate ambient pressure measurement and then add gauge pressures from there. (Gauge pressure is differential from absolute) 

3. pressure rise will be your basis for work input.

depending on whether you want to measure machine overall performance, or stage by stage performance, will determine how much additional instrumentation you will need to use.

you'll also need to measure  work input. If you are measuring machine overall performance, you can use drive power.

if you want performance of each stage, you'll have to measure work input on each stage, so you'll end up wanting to measure inlet and discharge temperatures for each stage.

You'll also have to account for other energy losses, such as heat loss from intercoolers and from the outside of the compressor casing, bearing losses, seal losses, etc... 

Absolute and relative accuracy of the measurements will significantly affect your results.

i strongly suggest you do a sensitivity study, to determine the relationship of your measurement accuracies to your performance calculations' accuracies.

There's really too much involved to be able to give this adequate treatment in this kind of environment, but maybe this will help. Feel free ask if you have more questions.

[aerospacian]

i have some snaps and data for my machine.can you give me your E-mail ID so that i can mail you and you can exactly come to know the scenerio for this.Thanx waiting for reply...

[Dave_Karon]

you may post them here.

[JÞB]

While the forums really are a great place to get lots of information it might be a good idea to start here and contact a Honewell app engineer who would have a lot of experience in this area.

Once you've chosen some sensors we will know what the output is (I2C, DIO, Serial, Analog... so many sensors to chose frm)

[aerospacian]

can i use pressure sensor of 1 psi as per the calculation given in my earlier text.since gage pressure reading after 3rd stage is  11.2 inches of water.

in my experimentation there was change of 5 inches in height of manometer column when pressure tube was inserted in the manometer.(5 in is the mean value of 10 pressure tubes inserted in the manometer panel).I m using water in the manometer not the mercury.

[Dave_Karon]

If all of your 10 pressure readings are within a few percent of each other, then the 1 psi transducer might be okay.

that would be a compromise between best resolution and some margin to full scale.

you must be careful, as some transducers can handle over pressured.

how will you be switching the  transducer between the pressure tubes?