Tag: Standard Air Knife

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

EXAIR Standard Air Knives™: Overview

Published on by John BallLeave a comment
From left to right: Super, Standard, and Full Flow Air Knives.

EXAIR manufactures three different styles of Air Knives; Super, Standard, and the Full Flow.  Standard Air Knives are the first model of air knives EXAIR began to manufacture.

Standard Air Knife

The Standard Air Knife uses a Coanda profile for blowing.  The Coanda effect was named after a Romanian aerodynamic pioneer, Henri Coanda, where he found a phenomenon with fluid flow.  He stated that a jet of fluid emerging from an orifice will follow an adjacent flat or curved surface to entrain fluid from the surrounding.  Being that air is a fluid, it will react in the same way.

Compressed air flows through the inlet (1) to the Standard 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 EXAIR Standard Air Knife creates a high velocity air stream along an engineered profile.  So, as the air “hugs” the profile, a low pressure is created which will draw in ambient air.  What does this mean for you?  If we bring in “free” ambient air into the compressed air stream, we add mass to the blowing force.  So, we can use less compressed air which will save you money.  We call this the amplification ratio.  For our Standard Air Knife, it has an amplification ratio of 30:1.  (As in, for every 1 part of compressed air, 30 parts of ambient air is drawn into the stream).  This design makes this product very efficient.

We stock the Standard Air Knives in various lengths from 3” to 48” (76mm to 1219mm) in two types of material; aluminum and 303 stainless steel.  This unique design is very compact; so, it can fit into tight places for blowing and cooling.  The aluminum version uses a plastic shim to set the gap.  They come standard with a 0.002” (0.05mm) shim installed.  We have additional shims to make the Standard Air Knife more versatile.  The Shim Set will include a 0.001”, 0.003”, and a 0.004” thickness shim (.03mm, .08mm, and 0.1mm respectively) for controlling the air flow from a small breeze to a blast.  The shims are color coded for easy verification.  The stainless steel Standard Air Knife comes with a stainless steel shim for higher temperatures and chemical resistance.

Standard Air Knife Kit

We do offer the Standard Air Knives in kits for a more complete package.  The kit will include the Air Knife, a Filter Separator, a Pressure Regulator and the above-mentioned Shim Set.  The Filter Separator will remove the debris and liquid water from the compressed air line to optimize the air knife as well as keeping your products clean.  The Pressure Regulator is used to make “fine” adjustments to the blowing force while the shims are used for a “coarse” adjustment to the blowing force.  Together, you can “dial” in the right amount of air required to do the job without wasting compressed air.

For easy mounting, we do offer a Universal Air Knife Mounting System.  This system is used to position your air knife securely and precisely.  It comes with a bracket to mount to the Air Knife and can be articulated in any position with a reach up to 30” (762mm).  You can direct the Standard Air Knife to maximize the effectiveness.  It is easy to use as seen in this video: CLICK HERE.

With today’s cost to make compressed air, it is important to do it as efficiently as possible.  The Standard Air Knife has the ability to give you the effective blowing to remove debris, dry parts, or cool objects without using a large amount of compressed air.  As another feature, the Standard Air Knife is quiet.  It only has a sound level of 83 dBA at 80 psig (5.5 bar).  So, by using this EXAIR product, you are not creating a noise nuisance in the work environment.  If you have any questions about the Standard Air Knife or if you would like to discuss an application, you can contact an Application Engineer at EXAIR.  We will be happy to help. 

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

Henri Coanda: June 7, 1886 – November 25, 1972

Published on by John BallLeave a comment
Compressed air flows through the inlet (1) to the Standard 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.

How did a past inventor help generate efficient compressed air products for EXAIR?  In the early 20th century, Henri Coanda who was a Romanian aeronautical engineer built an experimental Coanda-1910 airplane.  There are some debates if the airplane actually flew, but he invented a curved surface for a wing to generate a Coanda effect. The Coanda effect is the “tendency of a fluid jet to stay attached to a convex surface”1.   Thus, a moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line.  The Wright Brothers who flew the first airplane in the state where EXAIR is located, Ohio, used the Coanda effect to create lift.  With a curved profile, the air will adhere to the surface, causing a low pressure which makes the airplane fly.

EXAIR also uses this Coanda profile to make some of our Intelligent Compressed Air Products™.  Like an airplane wing, our curved surface will create a low pressure.  How does this help?  Well, higher pressure will always travel to lower pressure.  Instead of lift, we use the low air pressure to entrain ambient air.  This ratio of entrained air to compressed air is what we call the amplification ratio.  The higher the amplification ratio, the higher the efficiency for a blowing device. Two main compressed air products that EXAIR manufactures use this type of profile; Air Knives and Air Amplifiers.  I will cover both below. 

The Air Knives that use the Coanda profile blows air along the length of the knife at a 90o angle from the exit.  We offer two types; the Standard Air Knife and the Full Flow Air Knife.  The Standard Air Knives are made in Aluminum or Stainless Steel with blowing widths up to 48” (1219mm).  The inlet ports are at each end; so, the overall length is 1” (25.4mm) longer than the blowing length.  The Full Flow Air Knives have a port, or ports, on the backside.  Like the name states, the air blows out the entire length of the air knife.  The maximum length is 36” (914mm).  Both types use the Coanda profile to generate a low pressure as the air exits the gap and “hugs” the curve (reference photo above).  This low pressure draws ambient air into the air stream at a 30:1 amplification ratio for both the Standard Air Knife and Full Flow Air Knife.  So, for every one part of compressed air, we entrain 30 parts of ambient air.  Besides efficiency, it also adds mass to the air stream for a hard-hitting force.  With the engineered profile, the airstream is laminar which gives a consistent force across the entire length and makes them quiet.  Not only will they save you money by using less compressed air, but they are also OSHA safe.    

Super Air Amplifier – flow region

The Air Amplifiers use the Coanda profile in a circular form to pull in large amounts of free surrounding air.  The Coanda effect is able to generate a low pressure in the center to blow air for cooling, cleaning or removing welding smoke and debris efficiently and quietly.  The Air Knives above will blow a flat stream of air while the Air Amplifiers will blow a conical air stream.  They can reach amplification ratios up to 25:1. The Super Air Amplifiers use a patented shim to increase efficiency.  Unlike fans, they blow a laminar air stream for quick cooling.  They do not have any moving parts or motors to wear, so they are very quiet.  EXAIR manufactures five different sizes from ¾” (19mm) to 8” (203mm).  The Adjustable Air Amplifiers have a plug that can be adjusted to control the blowing from a breeze to a blast.  For cleaning surfaces, this is a nice feature to “dial” in the correct amount of blowing force.  We also manufacture five different sizes ranging from ¾” (19mm) to 4” (102mm).  Both types can be ducted to remove debris, heat or smoke. 

Utilizing the Coanda effect allows for massive compressed air savings. Whether it is a flat or round air stream, EXAIR can do this with high amplification ratios.  If you would like to discuss further how our Air Knives or Air Amplifiers can help you in your application, please contact us. An Application Engineer will be happy to help you replace your inefficient blowing devices.  History has given us a way to increase efficiency for blowing compressed air.  Thank you, Henry Coanda. 

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

1note – Wikipedia – Coanda effect

What Is A Coanda Profile?

Published on by Russ BowmanLeave a comment

The big thing that sets engineered products like EXAIR Intelligent Compressed Air Products apart from other devices is the engineering that goes into their design.  Several principles of fluidics are key to those designs:

The one I wanted to discuss today, though, is the Coanda Effect, what it means for our engineered compressed air products, and what they can do for you:

The Coanda effect is named after Henri Coandă, who was the first to use the phenomenon in a practical application…in his case, aircraft design.  He described it as “the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops.”  Put simply, if fluid flows past a solid object, it keeps flowing along that surface (even through curves or bends) and pulls surrounding fluid into its flow.  Here’s a demonstration, using an EXAIR Super Air Amplifier and a plastic ball:

What’s interesting here is that the Super Air Amplifier is not only DEMONSTRATING the Coanda effect, it’s also USING it:

Air Amplifiers use the Coanda Effect to generate high flow with low consumption.

EXAIR Standard and Full Flow Air Knives also have Coanda profiles that the primary (compressed air) flow follows, and uses, to entrain “free” air from the surrounding environment:

Compressed air flows through the inlet (1) to the Standard 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.

EXAIR Air Wipes can be thought of as “circular Air Knives” – instead of a Coanda profile along the length of an Air Knife, an Air Wipe’s Coanda profile is on the ring of the Air Wipe, which entrains surrounding air into a 360° ring of converging air flow:

Air Wipe – How it works

So that’s the science incorporated in the design of our products.  But what does it mean to the user?

  • Efficiency.  Pulling in a tremendous amount of “free” air from the surrounding environment means minimal consumption of compressed air, while still getting a hard hitting, high velocity air flow.
  • Sound reduction.  This air entrainment also creates a boundary layer in the air flow, resulting in a much quieter air flow than you get from a simple open-end blow off.

EXAIR Corporation is committed to helping you get the most out of your compressed air system, and thanks to Mr. Coandă, that includes reducing your compressed air consumption and noise levels.  If you’d like to find out more, give me a call.

Russ Bowman, CCASS

 

 

 

Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook