EXAIR Corporation’s engineered Air Knife products have a number of uses in industry. The laminar, even flow is conducive to generating a stripping/sweeping action that is particularly effective for blowing off, cooling, cleaning, drying, etc. The way that they entrain enormous amounts of air from the surrounding environment makes them incredibly efficient. This entrainment also makes them very quiet, as it forms a boundary layer that attenuates the sound level of the high velocity flow of the compressed air exiting the Air Knife. These two features have a distinct benefit in a rather unique application in a decidedly non-industrial setting, though.
A company that services amusement parks & carnivals was making a “haunted house” type attraction. At one point, the victims visitors are to be surprised by animated figures “floating” in the air. Their idea was to project the animation on a wall/screen of smoke…spooky, right? They tried discharging the smoke through a series of holes, and even a thin slot, but could not get the effect they wanted, so they called EXAIR to talk about Air Knives.
Smoke escaping small holes or a thin slot doesn’t have much velocity, so it didn’t make a great ‘curtain’ for projection. It’s also turbulent in nature, so it tends to billow & plume (like the top graphic). Engineered compressed air products like EXAIR’s Air Knives generate a laminar flow (like the bottom graphic) whose velocity can be precisely controlled by regulating the air supply pressure.
They found their solution for this application in a Model 2836SS 36″ Stainless Steel Full Flow Air Knife Kit. The Full Flow Air Knife is the most compact design for any given length, and with rear ports for the compressed air supply, it was easy to conceal from the visitors’ sight. When smoke is introduced from behind, it gets pulled in (entrained), and discharges in a laminar, even curtain that the animated figures magically appear on. The extraordinarily low sound level contributes to the magic, as it can’t be heard over the din of eerie sound effects & music that are synonymous with the haunted house experience.
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.
EXAIR Corporation has been in the business of providing quiet, safe, and efficient compressed air products for all kinds of applications for almost 39 years now. If you want to find out more about introducing more quietness, safety, efficiency…or magic…into your operation, give me a call.
Russ Bowman, CCASS
Application Engineer EXAIR Corporation Visit us on the Web Follow me on Twitter Like us on Facebook
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.
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:
Bernoulli’s Principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluid’s potential energy. It’s explained further here, along with details on how EXAIR products use it.
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
Recently, I was working with a customer looking for a Premium Reversible Drum Vac and wanted it shipped to the Northwest Territories of Canada – which we could do! It got me to thinking, what are the farthest US state and territory locations EXAIR has shipped to in the North, South, West and East directions. I ‘scoured’ the records and came up with these.
Furthest North- We have shipped to Prudhoe Bay, Alaska. Most recently, believe it or not, we shipped a NEMA 4X Cabinet Cooler to an Oil and Natural Gas Exploration Company. Goes to show that even the coldest environments still have the need to provide cool, clean, dry air to cool and protect electronics in electrical enclosures.
Furthest South – We have shipped to the US Territory of Puerto Rico, city of Santa Isabel. An Aerospace company needed a strong, laminar blast of air and utilized a 6″ Stainless Steel Air Knife. An Air Knife offers a quiet, efficient way to clean, dry or cool parts, webs, or conveyors.
Furthest West- We have shipped to the US Territory of Guam. The local University ordered a model 1111-4 Super Air Nozzle Cluster, for a good strong blast of air flow for a cleaning operation. The model 1111-4 delivers 3.2 lbs of force, at just 82 dBA of sound. A safe and efficient nozzle for blowoff operations.
Furthest East- We have shipped to Eastport, Maine. The customer in Eastport ordered a Line Vac and a section of Conveyance Hose. The Line Vac is a great tool for conveying large volumes of material over long distances, through a standard hose or tube. The compact design features large throat diameters for maximum throughput capability.
It was interesting to look back and see all the places that EXAIR has shipped. We have customers from all over the globe. If you are outside the of 50 US States and Canada, we have a dedicated team of International Application Engineers that will work with you to select the best EXAIR product for your process and application, and direct you to your local International Distributor.
If you would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
