Venturi or pitot for measuring air flow?
Venturi or pitot for measuring air flow?
(OP)
Hi, Im working on a project that requires a need for me to measure airflow into an engine. Im after a mechanical means to do this rather than an automotive electronic style air flow meter. As the title states, what would give me the most acurate, or strongest signals out of a venturi or pitot tube setup? Thanks in advance.
Brad
Brad





RE: Venturi or pitot for measuring air flow?
Pitot tube isn't usually employed for various reasons (low turndown ratio, fouling etc.) but the main one is that measuring local velocity in order to calculate global flow rate isn't practical as you should know the velocity profile in the pipe. The usual solution is the annubar, which measures the average pressure in pipe section.
Anyway, I would suggest you to employ an ISO 5167 Venturi tube for the following reasons:
- design is standardised, but not below 2" diameter (ID 50 mm) pipe. In this case you have to perform an individual calibration of the flow element;
- lowest permanent pressure drop among standard diff. pressure flow elements;
- upstream & downstream straight run requirement is the lowest among standard diff. pressure flow elements;
- within the limits of ISO 5167, accuracy is easily calculated and predictable, due to the large amount of data available.
Anyway, keep in mind that a Venturi Tube is usually long compared to pipe diameter, due to the little angles of convergent and divergent cones.
Hope it helps.
Stefano
RE: Venturi or pitot for measuring air flow?
----------------------------------------
The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
RE: Venturi or pitot for measuring air flow?
Is the section where the venturi flares back out important in its operation? Could I just do the following... 3in start, tapering down to 2in(where my mesuring takes place, then straight into my engine at the 2in size? Rather than going back out to the 3in again???
I hope that make sense.
Brad
RE: Venturi or pitot for measuring air flow?
Hope it helps.
Regards,
Stefano