Air Entrainment & EXAIR’s Intelligent Compressed Air Products

Air entrainment is a term that we bring up quite often here at EXAIR. It’s this concept that allows many of our products to dramatically reduce compressed air consumption. The energy costs associated with producing compressed air make it an expensive utility for manufacturers. Utilizing engineered compressed air products that will entrain ambient air from the environment allow you to reduce the compressed air consumption without sacrificing force or flow.

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

Products such as the Super Air Knife, Super Air Nozzle, Air Amplifier, and Super Air Wipe all take advantage of “free” air that is entrained into the primary supplied airstream. This air entrainment occurs due to what is known as the Coanda effect. Named after renowned Romanian physicist, Henri Coanda, the Coanda effect is used in the design of airplane wings to produce lift. As air comes across the convex surface on the top, it slows down creating a higher pressure on the underside of the wing. This creates lift and is what allows an airplane to fly.

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EXAIR Super Air Nozzle entrainment

This is also the same principle which is allowing us to entrain ambient air. As the compressed air is ejected through a small orifice, a low-pressure area is created that draws in additional air. Our products are engineered to maximize this entrained air, creating greater force and flow without additional compressed air. Super Air Amplifiers and Super Air Nozzles are capable of up to a 25:1 air entrainment ratio, with just 1 part being the supplied air and up to 25 times entrained air for free!! The greatest air entrainment is achieved with the Super Air Knife at an incredible ratio of 40:1!

This air entrainment principle allows you to utilize any of these products efficiently for a wide variety of cooling, drying, cleaning, or general blowoff applications. In addition to reducing your compressed air consumption, replacing inefficient devices with engineered products will also dramatically lower your sound level in the plant. Sound level in some applications can even be reduced down to a point that would eliminate the need for hearing protection with the OSHA maximum allowable exposure limits set at 90 dBA for an 8-hour shift.

If you have inefficient blowoff devices in your facility, give us a call. An Application Engineer will be happy to help you select a product that will “quietly” reduce your compressed air consumption!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Types of Air Amplifiers: Amplify Volume or Amplify Pressure

EXAIR Air Amplifiers use a small amount of compressed air to create a tremendous amount of air flow.

As Application Engineers, we help many customers with finding solutions with effective, safe, and efficient EXAIR products.  But, in some instances, we get a request for an air amplifier to increase line pressures.  EXAIR does not manufacture this type of Air Amplifier.  In doing some research on the internet, I was able to find two different types of air amplifiers.  In this blog, I will describe the difference between the pressure-type and volume-type.

The EXAIR Super Air Amplifiers are defined as a volume-type of an amplifier.  They use compressed air to generate a large volume of air flow.  The amplification ratio is the comparison between the inlet air flow and the outlet air flow.  With the EXAIR Super Air Amplifiers, we can reach an amplification ratio of 25 to 1.  They use a Coanda profile with a patented shim to create a low pressure to draw in a large volume of the surrounding air.  EXAIR manufactures a variety of different sizes, materials, and types.  But they all do the same thing, amplify the volume of air.  To give an example, model 120024 Super Air Amplifier has a 25:1 amplification ratio.  It uses 29.2 SCFM (826 SLPM) of compressed air at 80 PSIG (5.5 bar).  So, the outlet air flow is amplified from 29.2 SCFM to 730 SCFM (20,659 SLPM) of air.  This large volume of air works great for cooling, exhausting, and transferring.  But, with any type of amplification, you have to lose something.  With the volume type Air Amplifiers, the outlet pressure is reduced dramatically.

The pressure-type air amplifiers are different from the Super Air Amplifiers as this device will amplify the outlet air pressure, not the volume.  It is an air pump that has a direct dual piston that uses two different diameters.  The larger diameter uses the drive inlet pressure while the smaller diameter is used for the boost pressure.  The amplification ratio is determined by the difference in volume from the drive piston to the boost piston.  They also come in a variety of ranges and sizes.  As an example, an amplification ratio of 15:1 will increase an inlet pressure from 100 PSI (7 bar) to an outlet pressure of 1,500 PSI (103 bar).  Since the pressure-type air amplifier is an air pump, the system has to cycle.  To do this, they use pilot valves to either add the inlet compressed air to the drive piston or to relieve the air pressure from the drive piston.  This cycling portion of the operation does reduce the efficiency of the air amplifier.  The pressure-type air amplifiers are used to generate high pressure for a specific application or area and eliminate the purchase of a high-pressure air compressor.  The applications include air clamps and presses, pressure testing, air brakes, and also blow molding.  Like stated above about losing something with amplifications, the volume of air is reduced dramatically.  Generally, a reservoir tank and over-sizing will be needed for a good system.

The Application Engineers at EXAIR enjoy talking to customers about compressed air applications.  If you need more information about Air Amplifiers, you can contact us directly.  We can explain the volume-type that we manufacture or refer you to a company that makes the pressure-type.  Either way, we will be happy to hear from you.

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

Super Air Amplifier Overview – Vent, Exhaust, Cool, Dry, Clean

Vent, exhaust, cool, dry, clean -with no moving parts!  That tag line from the catalog section pretty much says it all about the EXAIR Air Amplifiers, both the Super Air Amplifier and the Adjustable Air Amplifiers. I want to share some more information about the Super Air Amplifiers.

In general, the air amplifiers employ the Coanda effect – a basic principle of fluid flow – to create air motion in their surrounding.  Through intelligent design, this surrounding fluid flow can be manipulated and exploited, creating an amplification of a small amount of compressed air.

AirAmplifiers
Super Air Amplifier

How do they work? In the figure below – a small amount of compressed air flows into the unit (1) to an annular chamber (2). The air is then throttled through a small ring nozzle (3) at high velocity. This primary air stream adheres to the Coanda profile (4), which directs it towards the outlet. A low pressure area is created at the center (5), inducing a high volume flow of the surrounding air into the primary stream. At the exit, you have the combination of flows, resulting in a high volume, high velocity flow.

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How Air Amplifiers Work
Super Air Amplifier Coanda Profile
Close Up of the Coanda Profile

The amplification ratio – the outlet airflow compared to the compressed air flow is dependent upon the cross sectional area of the inlet, and the 3/4″ Super Air Amplifiers have 12:1 amplification ratios all the way up to the 4″ and 8″ Super Air Amplifiers with 25:1 amplification ratios! That is a lot of ‘free air’ to use for cooling, drying and cleaning.  And a lot of air or smoke that can be drawn at the inlet and vented away from the area. For more on the amplification ratios, see this -blog-

Each Super Air Amplifier has a patented shim (patent#5402938) that precisely sets the compressed air flow, and shim sets are available to install to increase the force and flow as needed.

Super Air Amplifier Shims
Patented Shims for the Super Air Amplifier

The balanced outflow of air minimizes wind shear to produce a very quiet, powerful flow at sound levels up to three (3) times quieter than other air movers.  A 4″ Super Air Amplifier operated at 80 PSIG will have a Sound Level of just 73 dBA.

The video below shows the power of the Super Air Amplifier in inducing a high volume flow of surrounding air (for venting) into the primary air stream (for cooling/drying/cleaning)

Typical applications include venting weld smoke, cooling hot parts, drying wet parts, cleaning machined parts, distributing heat in mold & ovens, dust collection, and exhausting vent fumes.

If you have questions about the Super Air Amplifier or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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Henri Coanda: June 7, 1886 – November 25, 1972

Henri Coanda was a Romanian aeronautical engineer best known for his work on the fluid dynamic principle with his namesake, the Coanda effect. Before this, Henri patented what he labeled as a jet engine.

Jet Engine 1
Jet Engine

Henri’s patent (French patent No. 416,54, dated October 22, 1910) gives more information into how he envisioned the motor working. When air entered the front, it passed through different cavities that caused the air stream to first contract and then expand. In Henri’s opinion this contraction and expansion converted the air’s kinetic energy into potential energy.  The air ultimately was channeled to a diffuser where it was discharged.

Henri stated that the efficiency of this engine could be improved by heating the air in the cavities, Henri’s logic was that this would increase the pressure of the air passing through.

What is obviously lacking in the patent (including identical ones taken out in England and the United States) is any mention of injecting fuel, which in a true jet engine would combust with the incoming air. Judging only by Henri’s patent, it was little more than a large ducted fan and it could not have flown.  Throughout Henri’s career he changed his story many times on whether this plane actually flew or not.

Not to cast too much shade on Henri’s accomplishments he did discover the Coanda effect.  The Coanda effect states that a fluid will adhere to the surface of a curved shape that it is flowing over.  One might think that a stream of fluid would continue in a straight line as it flows over a surface, however the opposite is true.  A moving stream of fluid will follow the curvature of the surface it is flowing over and not continue in a straight line. This effect is what causes an airplane wing to produce lift, and enhance lift when the ailerons are extended while at lower air speeds such as occurs during takeoff and landing.

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Ailerons positioned for cruising speed

EXAIR uses the Coanda effect to offer you highly engineered, intelligent and very efficient compressed air products.  Our designs take a small amount of compressed air and actually entrain the surrounding ambient air with the high velocity exiting compressed air stream to amplify the volume of air hitting a surface.

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Surrounding Air Captured (Entrained) In Exiting Compressed Air Stream
How Air Knife Works
1). Compressed Air Inlet, 2). Compressed Air Exiting EXAIR Super Air Knife 3). Surrounding Air Being Entrained With Exiting Compressed Air Stream
Super Air Amplifier
EXAIR Super Air Amplifier Entraiment

When you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you.

Steve Harrison
Application Engineer
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Great Stuff About Jets

There are a number of fascinating facts about jets…both the aircraft engines and the EXAIR Intelligent Compressed Air Products:

  • Because they don’t require dense air to engage spinning blades (like their propeller driven counterparts,) they can operate at much higher altitudes. (Jet aircraft engines only)
  • They provide a high thrust, directed airstream, which makes them great for part ejection, chip removal, and part drying. (EXAIR Air Jets only)
  • With few or no moving parts, they are extremely reliable, durable, and safe. (Both jet aircraft engines and EXAIR Air Jets)
  • They use the Coanda effect (a principle of fluidics whereby a fluid flow tends to attach itself to a nearby surface, and follow that surface regardless of the flow’s initial direction) to do what they do.
    • EXAIR Air Jets use this principle to generate a vacuum in their throat, pulling in a large amount of “free” air from the surround environment, making their use of compressed air very, very efficient.
    • Jet (and propeller driven) aircraft wings employ the Coanda effect to create aerodynamic lift, enabling the plane to fly.

Now, since I’m not a pilot, nor do I particularly like to fly, but I AM a fluid dynamics nerd, the rest of this blog will be about the Air Jets that EXAIR makes.

All of our Air Jet products operate on the same principle…using the Coanda effect (as described above) to generate a high volume air flow while minimizing compressed air consumption:

(1) Compressed air enters and is distributed through an annular ring, and directed towards the discharge via the Coanda effect.
(2) This causes entrainment of surrounding air, both through the throat, and at the discharge.
(3) The total developed flow has tremendous force and velocity, for a minimal consumption of valuable compressed air.(1) Compressed air enters and is distributed through an annular ring, and directed towards the discharge via the Coanda effect.
(2) This causes entrainment of surrounding air, both through the throat, and at the discharge.
(3) The total developed flow has tremendous force and velocity, for a minimal consumption of valuable compressed air.

There are four distinct models of the EXAIR Air Jet:

  • Model 6013 High Velocity Air Jet is made of brass for economy and durability.  The annular ring gap (see 1, above) is fixed by a 0.015″ thick shim.  Performance can be modified by changing to a 0.006″ or 0.009″ thick shim, which come in the Model 6313 Shim Set.
  • Model 6013SS is a Type 303 Stainless Steel version, for higher temperatures – good to 400°F (204°C) – and superior corrosion resistance.
  • Model 6019 Adjustable Air Jet is brass construction, and dimensionally identical to the Model 6103.  Instead of a shim that sets the annular ring gap, though, it has a threaded plug, with a micrometer-style indicator, to “fine tune” the gap.
  • Model 6019SS is the Type 303 Stainless Steel version…fine tuning adjustability, good for high heat and/or corrosive elements.
Four distinct models to meet the needs of your air blowing application.

If you’d like to find out more about EXAIR’s quiet, efficient, and safe Air Jets, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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People of Interest: Henri Coanda June 7, 1886 – November 25, 1972

Henri Coanda was born in Bucharest, Romania on June 7 1886 in a large family with five brothers and two sisters. His father, Constantin M. Coanda, was a decorated Romanian soldier and following in his footsteps he also enlisted in the military. He finished his military education with high honors, but his keen interest in flying and his desire to achieve this sent him down a much different path.

Coanda attended a technical university in Germany and also attended the Superior Aeronautical School in Paris where he graduated at the top of his class with the highest of honors. In less than a year, he had partnered with Gianni Caproni, another known aviator, to construct what was called the Coanda-1910. This aircraft was displayed in Paris at the Second International Aeronautical Exhibition. But, unlike other planes of this time, Coanda’s aircraft did not have a propeller. The plane had an oddly shaped front with built-in rotary blades arranged in a swirling pattern. It was driven by an internal turbine screw that would suck air in through the turbine while the exhausting gases exited from the rear, driving the plane forward by propulsion.

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As impressive as this jet engine was, no one believed that it could fly. It is not believed that it ever did achieve flight, despite some contradictory claims by Coanda himself, but was instead struck by disaster. It is rumored that as Coanda injected more fuel into the engine, he was surrounded by flames, thrown from the craft and was lucky to make it out alive. Coanda is not credited as the inventor of the first jet plane, but it is his technology that sky rocketed future aviation research and provided perspective into how jet engines should be built.

Coanda is most known today for his research into what is now known as the Coanda Effect, or propensity of a fluid to adhere to the walls of a convex surface. It is this principle that creates lift on an airplane wing and is also the driving force behind many of EXAIR’s Intelligent Compressed Air Products. If you’d like to discuss how the Coanda effect is utilized in a Super Air Knife, Super Air Amplifier, or Super Air Nozzle give us a call!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

 

Jet Engine image courtesy of Luke Healy via Creative Commons License

Fluidics, Boundary Layers, And Engineered Compressed Air Products

Fluidics is an interesting discipline of physics.  Air, in particular, can be made to behave quite peculiarly by flowing it across a solid surface.  Consider the EXAIR Standard and Full Flow Air Knives:

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 serve to optimize the entrainment of air (4) from the surrounding environment.

If you’ve ever used a leaf blower, or rolled down the car window while traveling at highway speed, you’re familiar with the power of a high velocity air flow.  Now consider that the Coanda effect can cause such a drastic redirection of this kind of air flow, and that’s a prime example of just how interesting the science of fluidics can be.

EXAIR Air Amplifiers, Air Wipes, and Super Air Nozzles also employ the Coanda effect to entrain air, and the Super Air Knife employs similar precision engineered surfaces to optimize entrainment, resulting in a 40:1 amplification ratio:

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

As fascinating as all that is, the entrainment of air that these products employ contributes to another principle of fluidics: the creation of a boundary layer.  In addition to the Coanda effect causing the fluid to follow the path of the surface it’s flowing past, the flow is also affected in direct proportion to its velocity, and inversely by its viscosity, in the formation of a boundary layer.

High velocity, low viscosity fluids (like air) are prone to develop a more laminar boundary layer, as depicted on the left.

This laminar, lower velocity boundary layer travels with the primary air stream as it discharges from the EXAIR products shown above.  In addition to amplifying the total developed flow, it also serves to attenuate the sound level of the higher velocity primary air stream.  This makes EXAIR Intelligent Compressed Air Products not only as efficient as possible in regard to their use of compressed air, but as quiet as possible as well.

If you’d like to find out more about how the science behind our products can improve your air consumption, give me a call.