Turbo rotational speed sensor/meter
Turbo rotational speed sensor/meter
(OP)
Does anyone know of a sensor that would be adaptable to or is designed for measuring the rotational speed of a turbo? Any help/suggestions are highly appreciated. as for the motives, for the application I have in mind, a boost guage is just not good enough.
Cheers
Cheers





RE: Turbo rotational speed sensor/meter
You may be familiar with the plastic light-pipes that are used to move LED illumination from a circuit board to a front panel ? Same thing - use two pipes, running along the inside of the intake tract and terminating just in front of the intake wheel.
The other end has a bright LED shining into one pipe, the other has a photodiode. A microcontroller turns on the LED, then counts the pulses coming from the photodiode over a given period. Divide by the number of vanes in the turbine wheel and you get revolutions per period.
The plastic light-pipes are easy to shape - just heat and bend.
Dean.
RE: Turbo rotational speed sensor/meter
Another option would be to drill a small (1/8") hole right through the whole housing, crossing through the outer edge of the compressor inducer. A light source in one end, and a receiver in the other will count the light blocked and passed by the passing blades, and will give higher contrast for the sensor.
I saw once a setup that used a microwave transducer embedded inthe side of the housing at the inducer. The impedance of the transducer would change as the blades passed it as it would cause small eddy currents in the compressor.
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
Here's one that is 4uS rise and 6uS fall time.
http://www.pacer.co.uk/db_pdf/VTT1212%20&%20VTT1214.pdf
And 2uS rise 3uS fall.
http://www.pacer.co.uk/db_pdf/VTT1222W%20&%20VTT1223W.pdf
I don't think we'll have any trouble getting one fast enough. Hrm - anyone know if light-pipe plastic will transmit IR as well as it does visible light ?
Dean.
RE: Turbo rotational speed sensor/meter
then with anything capable of sensing 300000 optical signals a minute will do or if you drilled the hole not though the middle but to one side and you put your sensors in line with it you would get a signal per turn.
RE: Turbo rotational speed sensor/meter
Then drill a small hole in the intake hose flange, so a piece of brass tubing would fit. Run a pair of fibers through it, pointing at the nut. The other end goes back into the cabin to the unit, where the ends terminate at an IR LED and photodiode/transistor.
Would normal multimode or singlemode fiber work here ? That brass tube will get pretty hot ...
Dean.
RE: Turbo rotational speed sensor/meter
Sensing the speed of a turbocharger could be a very difficult task. My main concern is that the high temperatures involved could fry any sensor in a short period of time. From my limited experience in working with speed pickups used in diesel engines (engine RPM that is), I can offer some possible suggestions.
Do not interface your speed pickup sensor directly at the turbine wheel where the maximum temperatures will be seen. There is no need to count the number of blades on the turbine wheel. On diesel engines, a magnetic pickup (“mag-pickup for short) is mounted on the bell housing of the starter gear and the sensor “counts” the teeth on the flywheel as the engine spins. I think a similar approach would work for your application. Instead of counting blades, you could mount your mag-pickup at the coolest part of the turbo shaft (assuming the temperatures there will not melt the sensor) and trigger the sensor off some single part of the shaft (keyway or whatever). Now you have one digital pulse from the sensor per revolution (MUCH easier, no need to beat yourself up). I have worked mainly on the software side of these applications, but I know the Electrical Engineers feed the pulse signal from the mag-pickup into an electrical hardware circuit called a phase-locked-loop (PLL). The PLL processes the signal and increments a dedicated counter once for every pulse from the mag-pickup. This frees up the ECU or microcontroller from operating in a dedicated mode where it’s trying to run code to count input signals, convert the count to RPM and do something with the value obtained, all while performing the other tasks required to run the application. By setting up the microcontroller to trigger on a DEDICATED interrupt schedule (e.g. every 20 milliseconds the microcontroller stops whatever it’s doing and runs this routine) you can read the elapsed counter value at the start of the interrupt, and since you know the micro is reading this counter EVERY 20 milliseconds (i.e. a standard timebase), you can easily use a simple lookup table to convert counts to RPM. This may be the only practical approach in acquiring pulses at the speeds you’re looking at. My best suggestion would be to find an Electrical person with some experience in PLL’s and see if you could get some assistance with a prototype circuit. What you are trying to do has been done before in other applications (they do measure the shaft speed of turbine engines), but I’m not sure the extreme temperatures will cooperate in your application. Best of luck!
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
This definitley sounds interesting. Umm, given that's it's aerospace, how does pricing look ?
Dean.
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
We test the speed of the turbos on all gas and diesel engine dynamometer test stands. We record this speed with the data acquisition system. Typical is using a magnetic pickup as several above people suggested. This is typically used to pick up 2-PPR off the turbo. There aren't magnets on the shaft, but you can find where you can get some offset steel 'teeth' on each side, typically designed in by the manufacturer.
Visit
http://www.speed-position.invensys.com/pdf_aero_b1-1.asp
to help choosing the correct mag-pickup. You can then take the frequency output ie typical diesel engine turbo operates at about 120kRPM, or with 2-ppr at about 4kHz. For a cheap monitoring device, choose a signal conditioner that takes the 0-4khz and changes it into a 0-5VDC output, then put that into a calibratable panel meter, Newport or someone. For our data acquisition we use Dyne Systems Company's "Companion" system (dynesystems.com), but we're monitoring way more channels of data than just turbo speed.
-Bob
RE: Turbo rotational speed sensor/meter
I'd like feedback on whether any of my plan is feasable and if so, what components might be used for the project.
Thank you,
Roger
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
Alternatively, maybe an inductive sensor such as is used on ring-gear teeth on flywheels for tachometers. That ought to go close to the frequency, if not maybe a vane/reluctor secured to the compressor shaft
RE: Turbo rotational speed sensor/meter
RE: Turbo rotational speed sensor/meter
motors with back_EMF_sensor. Electronics is cheap in quantity !!!
<nbucska@pcperipherals.com>
RE: Turbo rotational speed sensor/meter
Alternatively, a sensor capable of use in the hot zone of gas turbines is being developed by these people:
http://www.isis-innovation.com/licensing/818.html
Otherwise, hope you find what you want.
RE: Turbo rotational speed sensor/meter
The turbo has an extended magnetic nut holding the inlet turbine wheel on, and an inductive speed sensor pressed against the rubber pipe that connects the turbo to the intercooler tubing. This sensor is basically the same as the wheel sensors used in Bosch ABS systems.
Any modifications will need to be done by someone that can rebalance the turbo.
Good luck,
B