air speed

[abdel]

i need to regulate the air flow into an industrial oven ,and to do so :

i have an asynchronous motor which i will connect to a frequency converter (excuse my english if i dont use the correct technical terms i studied and work in a french country ) and then regulate the speed of which the ventilator rotates .and this is where i need help i need to find the connection or the equation between the rotation speed of the propellers and the speed of air that s being propelled  so that i multiply the latter by the section of the airway and finally regulate the air flow .

ps : i know i can just use a sensor to calculate the airflow and regulate it directly but that is not the purpose of this post .

also i have the measurements of the propellers ,i know that will be needed i juts fail to find the right equation to use.

thanks for your help in advance 

Edited February 19, 2020 by abdel

[studiot]

https://www.axair-fans.co.uk/news/applications/understanding-basic-fan-laws/

 

This should do ya.

[Strange]

1 hour ago, abdel said:

ps : i know i can just use a sensor to calculate the airflow and regulate it directly but that is not the purpose of this post .

I was going to suggest that, as a more accurate approach. But even then I guess you need to be able to calculate the airflow (range) in order to design the system.

[Bufofrog]

I worked in a factory with many dryers with different control schemes.  By FAR the best control method is to use an anemometer in the dryer to control the fan speed, that in conjunction with temperature and humidity control should get you what you need.

[abdel]

2 hours ago, Bufofrog said:

I worked in a factory with many dryers with different control schemes.  By FAR the best control method is to use an anemometer in the dryer to control the fan speed, that in conjunction with temperature and humidity control should get you what you need.

Yes that can most definitly work and give me the air speed value ( bear with me here  ) but how do i convert that air speed value to the appropriate fan rotation speed value so that the cpu (api) sends the right signal to the frequency converter to finally get through the motor the new air speed desired . It seems to me that even if i have the air speed  value im gonna still need the connection between it and the rotation speed of the fan .

4 hours ago, studiot said:

https://www.axair-fans.co.uk/news/applications/understanding-basic-fan-laws/

 

This should do 

First of all thank you very much for replying

Im currently working on something right now it ll take a minute. as soon as i check it out im gonna get back to you if i find what i was looking for .

[Bufofrog]

1 hour ago, abdel said:

Yes that can most definitly work and give me the air speed value ( bear with me here  ) but how do i convert that air speed value to the appropriate fan rotation speed value so that the cpu (api) sends the right signal to the frequency converter to finally get through the motor the new air speed desired . It seems to me that even if i have the air speed  value im gonna still need the connection between it and the rotation speed of the fan .

The last dryer we set up simply had a control loop that used the signal from the anemometers to the VFD for the fan.  The power source was 60 Hz so the full open speed was 60 Hz.  We did not care what the rotational speed of the fan was (obviously the fan was sized properly, well almost the motor was actually oversized...).  

Just tune the air speed reading to the frequency output of the VFD.   Worked like a champ.

Edit to add - Over time the actual air flow from the rotational speed of the fan can change due to debris build up or loading of the dryer, etc., but if you use the actual air speed at the product location in the dryer then changes in the efficiency of the fan doesn't matter.

Edited February 19, 2020 by Bufofrog

[abdel]

On 2/19/2020 at 5:17 PM, Bufofrog said:

The last dryer we set up simply had a control loop that used the signal from the anemometers to the VFD for the fan.  The power source was 60 Hz so the full open speed was 60 Hz.  We did not care what the rotational speed of the fan was (obviously the fan was sized properly, well almost the motor was actually oversized...).  

Just tune the air speed reading to the frequency output of the VFD.   Worked like a champ.

Edit to add - Over time the actual air flow from the rotational speed of the fan can change due to debris build up or loading of the dryer, etc., but if you use the actual air speed at the product location in the dryer then changes in the efficiency of the fan doesn't matter.

Thaaank you for your help .I will test this solution starting next monday when we have a halt of production.

 I ll give feedback of the results.

[Amrita Vishwa Vidyapeetham]

That is great.