Titan Fluid Flow Sensors – Jet Engine Oil Consumption – Do I know enough about my fluid?

Titan Enterprises recently supplied a set of fluid flow sensors with appropriate electronic package to a highly regarded company to meter the oil consumption of a jet engine to an accuracy of better than ±0.5%.

The flow sensors were calibrated on the actual fluid used in the jet engine and oil manufacturer’s density charts were used to apply the corrections for temperature changes. A calibrated PT100 was incorporated into the flowmeter body to ensure accurate temperature measurement.

During testing the customer weighed the oil at the start of the run, ran the engine for a pre-determined period and weighed the remaining oil to see how much the engine had consumed. After the initial test the customer reported that the supplied fluid flow sensor was over 0.5% out from their mass tests. They returned the flow sensor to the factory and we re-calibrated and attained virtually identical results to our first run. Doubting our calibration rigs we did a mass calibration on our flow rigs but this appeared to confirm that everything was calibrated correctly.

I was invited to witness a flow-calibration run on the engine and jumped at the opportunity. I observed the fluid flow sensor calibration procedure and could see no problems with the techniques used but could not explain the offset in the answer which was repeatable but wrong. I decided to check the density correction matrix we had entered into the system in case we had made a repeated error. I had forgotten to bring the suppliers data sheets so asked for a copy from the customer. You’ve guessed it I was presented with their own density correction chart which was 0.5% offset from the manufacturers. Entering the customer’s empirically collated data the fluid flow sensor performed perfectly.

The moral of this rather long winded story is very simple, do you know what you are actually metering and always check that tests have used the correct start parameters!

Here is a checklist you might want to follow if you encounter a similar problem:

  • Is the fluid that you are using the correct fluid?
  • Is the data on the product sheets correct? Can the published data be verified?
  • Are the density and viscosity parameters acceptable? Both vary with temperature. Should I be measuring temperature and applying a correction?
  • Are there any suspended solids? Where is the filter in the system? The filter should always be before the fluid flow sensor and preferably immediately before it.
  • There are a raft of other considerations you have to be sure of. Is the fluid thixotropic? Are there corrosion considerations? Does the fluid “build up” on the walls of the pipe and/or the flow sensor?

Contact Titan here regarding fluid flow sensors and/or flow measurement for determining jet engine oil consumption