Tag: coanda

Entrainment: How it Works and Why EXAIR Products are Engineered to Use it.

Published on by John BallLeave a comment
EXAIR Super Air Nozzle entrainment

Because of the large amount of energy required to run an air compressor, the pneumatic system is considered the fourth utility in a manufacturing plant.  And saving this commodity and using it as efficiently as you can, should be a priority.  EXAIR has many products that can save energy by using less compressed air.  And the story behind this is entrainment explained by Bernoulli’s equation. 

Bernoulli’s principle explains how a high velocity fluid can generate a low pressure.  (You can read more about Bernoulli’s principle HERE.)  Let’s start by looking at Equation 1.

Equation 1:

P + d * V2/2 = C 

P – pressure

d – density of the fluid

V – velocity

C – a constant

As you can see from Equation 1, when the velocity goes up, the pressure must go down.  When we have a lower pressure, then the surrounding fluid will fill that void.  Since air is a fluid, we can use high velocity to entrain the surrounding ambient air.  The free air will add to the compressed air to give the airstream mass for a hard-hitting force.  This ratio of ambient air to compressed air is called entrainment.  The higher the entrainment, the more efficient the product.  Bernoulli’s Principle can be applied in two ways; as a Coanda and as a Venturi.  EXAIR uses both methods in our products for creating low-pressure effects. 

Compressed air flows through the inlet (1) to the Full Flow (left) or Standard (right) Air Knife, into the internal plenum. It then discharges through a thin gap (2), adhering to the Coanda profile (3) which directs it down the face of the Air Knife. The precision engineered & finished surfaces optimize entrainment of air (4) from the surrounding environment.

The first way is from a Coanda profile.  Coanda, named after Henri Coanda, noticed that a fluid would “hug” a curved surface.  (You can read more about Henri Coanda HERE.)  The high velocity air going around the curved surface will generate a low pressure above it.  You can imagine an airplane wing generating that low pressure to fly.  We use this with our FullFlow and Standard Air Knives, our Air Wipes, and our Air Amplifiers.  With a Coanda profile, we can get an amplification ratio up to 30:1, which means that for every 1 part of compressed air, 30 parts of ambient air is entrained.  We are able to create an efficient blow-off device by using the Coada profile. 

To generate even lower pressure, this can be done by a Venturi.  This phenomenon is named after Giovanni Venturi, who discovered that by increasing the velocity through an orifice, the surrounding fluid will move with it, generating a lower pressure.  (You can read more about Giovanni Venturi HERE.)  Remember the higher the velocity, the lower the pressure from Equation 1 above.  We use the Venturi effect on our Super Air Knives, E-Vacs, Line Vacs, and Super Air Nozzles.  As compared to our FullFlow and Standard Air Knives, the Super Air Knives can generate an amplification ratio of 40:1.  As an engineered product, we were able to increase efficiency even further. 

EXAIR has been manufacturing Intelligent Compressed Air® products since 1983.  We can provide solutions that are efficient, effective, and safe for blow-off systems.  In comparison, the other blow-off devices are like incandescent light bulbs, while EXAIR products are like LED light bulbs.  Entrainment of free ambient air can save you a lot of money when using your compressed air system.  If you would like to discuss solutions to use less compressed air and improve your bottom dollar, an Application Engineer at EXAIR is available to help.   

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

What’s So Great About EXAIR Air Jets?

Published on by Russ BowmanLeave a comment

For over 40 years now, EXAIR has been making engineered Air Nozzles and Air Jets for a wide range of industrial and commercial applications. Basically, if you need to blow air onto, into, towards, or through something, we’ve got something for that.

Our Super Air Nozzles seem to “get all the press” (based on an unscientific survey of the EXAIR Blog), and maybe they should, with their ease of installation onto the end of a pipe or tube that someone who’s never thought about the cost of compressed air has been using as a cheap to make but expensive to operate blowoff.

Compression fittings and Model 1100 Super Air Nozzles transformed the part ejection from “loud and wasteful” to “quiet and efficient.”

Like our engineered Super Air Nozzles, our Air Jet products use the Coanda effect to entrain enormous amounts of free air from the surrounding environment. While the Super Air Nozzles do this via an array of small holes recessed between a series of fins, the Air Jet uses an internal annular ring nozzle to draw the free air through its throat. There are a number of applications where either a Super Air Nozzle or an Air Jet can be used efficiently, safely, and quietly. Some jobs, however, benefit from the specific design of one or the other. Since this is an Air Jets blog, I’m going to focus on them:

  • Powerful, directed air stream. This makes EXAIR Air Jets ideal for part ejection, chip removal, and part drying.
Model 6013 Brass High Velocity Air Jet (left) blows rinse water off beverage cans on a high speed conveyor. An array of Model 6013SS SS High Velocity Air Jets (right) dries a finned component after washing.
  • Reliable and efficient blowoff. With no moving parts, as long as you supply them with clean compressed air, they’ll operate darn near indefinitely, maintenance free. And they’ll use a LOT less of that compressed air than similarly sized open-ended blowoff devices too, thanks to engineering:
Compressed air enters through the 1/8 MNPT fitting and discharges into the throat via an annular ring gap, where the Coanda profile of the plug directs the air towards the jet outlet (1). This primary, high velocity flow pulls in air from the entrainment plenum (2), creating a total developed flow up to 25 times the compressed air flow (3).
  • Safe to use. EXAIR Air Jets, like the rest of our Intelligent Compressed Air Products, are compliant with OSHA Standard 1910.242(b) which limits the downstream pressure at the nozzle or opening of a compressed air device used for cleaning purposes to 30psi. If you cover the entire outlet opening, the air simply flows out the entrainment plenum.
  • Remote positioning. Since both the inlet and outlet can be ducted, you can fit a 1″ ID hose over the entrainment plenum and run the other end to the location where you want to draw airflow from. This is beneficial if, for example, you want to position the Air Jet in a contaminated area, but want to eliminate any of that contamination from the Air Jet’s developed airflow. You can also fit a 1/2″ ID hose over the outlet to direct the airflow elsewhere.
  • Adjustability. For the Adjustable Air Jet, it’s right there in the name: the Plug can be threaded into, or out of, the body to reduce, or increase the annular ring nozzle’s gap, and hence, the airflow and force applied. There’s a micrometer gap indicator so you can set – and reset – the performance to different levels, as required. The High Velocity Air Jet’s annular ring nozzle gap is fixed with a shim (they come with a 0.015″ thick shim installed) but Shim Sets, containing one each of a 0.006″ and 0.009″ thick shim, can be used to make gross adjustments to the airflow and force applied. You can regulate the air supply pressure to either the Adjustable or High Velocity Air Jets to very precisely “dial in” the performance.
A 0.006″ or 0.009″ thick shim from the 6313 Air Jet Shim Set (top left) can be installed in a High Velocity Air Jet (bottom left) to put the Air Jet in a whole new performance band. You can do this to an Adjustable Air Jet (right) by turning the knurled ring on the plug to set (and reset) the air gap and hence the performance.
  • Materials of construction. Both the Adjustable and High Velocity Air Jets come in brass for general purpose applications, or 303SS for use in areas with high heat or corrosive elements in the environment.
The brass Air Jets (top) are rated for installation in areas with ambient temperatures up to 275°F, while the 303SS models (bottom) are good to 400°F.

If you’d like to find out more about EXAIR Air Jets, or how any of our Intelligent Compressed Air Products can help you get the most out of your compressed air system, give me a call.

Russ Bowman, CCASS

Application Engineer
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Entrainment: How It Works, and Why EXAIR Products Use It.

Published on by John BallLeave a comment
EXAIR Super Air Nozzle entrainment

Because of the large amount of energy required to run an air compressor, the pneumatic system is considered the fourth utility in a manufacturing plant.  And saving this commodity and using it as efficiently as you can, should be a priority.  EXAIR has many products that can save this energy safely and effectively.  And the story behind the efficiency of EXAIR products is Bernoulli’s equation. 

Bernoulli’s principle explains how a high velocity fluid can generate a low pressure.  (You can read more about Bernoulli’s principle HERE.)  Let’s start by looking at Equation 1.

Equation 1:

P + p * V2/2 = C 

P – pressure

p – density of the fluid

V – velocity

C – a constant

As you can see from Equation 1, when the velocity goes up, the pressure must go down.  When we have a lower pressure, then the surrounding fluid will have to fill that void.  Since air is a fluid, this is how we can entrain the free ambient air while only using a small amount of compressed air.  Bernoulli’s Principle can be applied in two ways; as a Coanda and as a Venturi.  EXAIR uses both methods in our products for creating low-pressure effects. 

Compressed air flows through the inlet (1) to the Full Flow (left) or Standard (right) Air Knife, into the internal plenum. It then discharges through a thin gap (2), adhering to the Coanda profile (3) which directs it down the face of the Air Knife. The precision engineered & finished surfaces optimize entrainment of air (4) from the surrounding environment.

The first way is from a Coanda profile.  Coanda, named after Henri Coanda, noticed that a fluid would “hug” a curved surface.  (You can read more about Henri Coanda HERE.)  The high velocity air going around the curved surface will generate a low pressure above it.  We use this with our Full Flow and Standard Air Knives, our Air Wipes, and our Air Amplifiers.  With a Coanda profile, the low pressure will entrain the surrounding air to add mass to the air stream.  We can get an amplification ratio up to 30:1, which means that for every 1 part of compressed, 30 parts of ambient air are entrained.  We are able to create an efficient air moving (blow-off) device by using the Coanda profile. 

Generating even lower pressures can be accomplished with a Venturi.  This phenomenon is named after Giovanni Venturi, who discovered that by increasing the velocity through an orifice, the surrounding fluid will move with it, generating a lower pressure.  (You can read more about Giovanni Venturi HERE.)  Remember the higher the velocity, the lower the pressure.  We use the Venturi effect on our Super Air Knives, E-Vacs, Line Vacs, and Super Air Nozzles.  When compared to our Full Flow and Standard Air Knives, the Super Air Knives can generate an amplification ratio of 40:1.  We were able to engineer the product to increase the air entrainment efficiency even further. 

EXAIR has been manufacturing Intelligent Compressed Air® products since 1983.  We provide solutions that are efficient, effective, and safe for air moving and blow-off systems.  Consider the following analogy; homemade air movers and blow-off devices are the equivalent to incandescent light bulbs. EXAIR products are the equivalent to LED light bulbs.  More efficient design leads to lower operating cost, higher efficiency and a higher level of effectiveness. Entrainment of free ambient air can save you a lot of money and increase your mass flow with your compressed air use to generate higher forces on your targets.  If you would like to discuss solutions to use less compressed air, an Application Engineer is available to help.    

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

How EXAIR Uses Fluidics To Make Efficient, Quiet, and Safe Compressed Air Products

Published on by Russ BowmanLeave a comment

EXAIR Intelligent Compressed Air Products incorporate several distinct principles of fluidics into our engineered designs. To be clear, these principles aren’t exclusive to making quiet and efficient compressed air products. I personally have used them all for business and pleasure over the years. In the Navy, for example, the air ejectors that pulled vacuum on the main condensers where our turbines dumped their ‘used’ steam were basically great big Venturis – they restricted the diameter through which a fluid (steam, in this case) flowed, gradually increased that diameter, and doing so, changed the velocity so that a low pressure area (or vacuum) developed in the throat:

Graphic representation of the Venturi effect.

EXAIR E-Vac Vacuum Generators use the Venturi effect to draw vacuum of up to 27″Hg. They’re typically used with Vacuum Cups for pick-and-place material handling applications.

Here are a few examples of Mr. Venturi’s discovery, implemented in modern industry.

I first learned about the Bernoulli principle on a grade school field trip to the National Air Force Museum at Wright Patterson Air Force Base, about an hour from where I grew up. See, this Bernoulli guy discovered that when there is an increase in the speed of a fluid, a simultaneous decrease in fluid pressure occurs at the same time. That’s why airplane wings are shaped like they are – flat on the bottom and curved on top…when the air flowing that extra distance over the top speeds up to get to the back of the wing as fast as the air that’s simply flowing underneath the wing does, the decrease in pressure on top causes the wing (and the plane it’s attached to) rise in the air.

Bernoulli’s Equation: this is the math that proves it works.

The Bernoulli principle is incorporated in to the design & operation of EXAIR engineered Air Knives, Air Wipes, Air Amplifiers, and Air Nozzles.

The Coanda effect is the third fluidics principle that’s incorporated into the design & operation of many EXAIR engineered compressed air products. Its namesake, Henri Coanda, was an early 20th Century aeronautical engineer who discovered that if a jet of fluid exiting an orifice flows across a surface, it’ll tend to not only adhere to and follow that surface (even if it curves or bends), but also entrain fluid from the surrounding area.

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier all use the Coanda effect to entrain enormous amounts of air from the surrounding environment.

There are a couple of easy – and interesting – experiments that demonstrate the Coanda effect, both of which I used when I was a Cub Scout leader and our Pack’s Webelos den was earning their Science Activity Pin:

Turn a faucet on and let the running water flow over the convex ‘bottom’ of a spoon. Everything we know about the laws of gravity say that when the water reaches the ‘bottom-most’ point on the spoon’s convex surface, it ought to fall straight down…but it doesn’t:

Another experiment that defies everything we think we know about gravity can be performed with a ball, and a source of air flow. Here’s a short video, showing how the air flow from an Air Amplifier ‘wraps’ around a ball and holds it in that jet of air:

The Webelos den did this with a leaf blower and a playground ball. Unlike a lot of things I’ve done, I DEFINITELY encourage you to try THAT at home.

For forty years now, EXAIR has been putting these principles of fluidics into practice by engineering & manufacturing the most efficient, quietest, and safest compressed air products on the market. If you’d like to find out how we can help you get the most out of our products – and your compressed air system – give me a call.

Russ Bowman, CCASS

Application Engineer
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