# Calculating force input to air cylinder by airflow rate

• jphd
In summary: The system will use a cylinder of known volume and stroke length, with sudden contraction to a smaller diameter at the mouth. The airflow rate at the outlet of the mouth will be 400 litres/min at its peak, with a breathing pattern that is a sine wave. The pressure in the cylinder is unknown.
jphd
Hello there

I'm having real difficulty with a problem to do with air cylinders and would really appreciate some help. I'm attempting to replicate the human breathing system in a simplistic form but I'm having trouble calculating the force required to provide the correct airflow rate at the mouth. My system will be some form of air cylinder or bellows driven by a linear actuator/servo motor. The trachea, larynx, pharynx, etc will be replicated using standardised garden hose (very basic but the diameters are very similar).

I have an air cylinder of diameter, D1, where the piston is driven by an external force, Fd. This cylinder is of a known volume (approximately 5 litres), therefore, I know what the stroke length of the piston will be. D1 will then suddenly contract to a smaller diameter, D2 (20 mm) and continue as this diameter until the exit of the mouth 375 mm from the lungs. The airflow at the outlet of the hose/mouth will be 400 litres/min at it's peak, although the flow pattern is a sine wave and the average is lower. The pressure in the cylinder is unknown.

My question is: how can I calculate the force, Fd, required to provide the 400 litres/min airflow at the output of the hose/mouth?

Thanks in advance and sorry if the question is scrappy

Jon

(1) Have you read this : http://mj.mefanet.cz/mj-04141203

(2) Please clarify what you mean by " flow pattern is a sine wave " ?

Hi Nidum,

Thanks for the link. That system is a lot more sophisticated than the one I am after but I think it's along the right tracks of what I need so thank you again! Might be a life-saver there.

And in response to (2): my mistake. That was the wrong term to use. I meant the breathing pattern, not the flow pattern.

Jon

## 1. How do you calculate the force input to an air cylinder by airflow rate?

The force input to an air cylinder can be calculated by multiplying the airflow rate (in cubic feet per minute or CFM) by the air pressure (in pounds per square inch or PSI) and dividing by the area of the air cylinder's piston. The formula for this is: Force = (CFM * PSI) / Piston Area.

## 2. What is the significance of calculating force input to an air cylinder?

Calculating the force input to an air cylinder is important because it allows us to determine the amount of power or strength that the cylinder can generate. This information is crucial for designing and using pneumatic systems in various industries, such as manufacturing, transportation, and construction.

## 3. How does the airflow rate affect the force input to an air cylinder?

The airflow rate has a direct impact on the force input to an air cylinder. A higher airflow rate means more air molecules are being pushed through the cylinder, resulting in a greater force being generated. Therefore, increasing the airflow rate can increase the force output of the cylinder.

## 4. Are there any limitations to using this calculation method?

While this calculation method is commonly used, it is important to note that it may not account for all factors that can affect the force input to an air cylinder, such as friction, leakage, or changes in temperature. It is always best to consult with a professional engineer or conduct thorough testing to ensure accurate results.

## 5. Can this calculation be used for all types of air cylinders?

This calculation is generally applicable to pneumatic cylinders, which use compressed air as their power source. However, the specific design and characteristics of each cylinder may vary, so it is important to confirm that the formula is suitable for the particular cylinder in question.

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