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.

The Case Is Mounting For Stay Set Hoses

So, you’ve selected a quiet, efficient, and safe EXAIR Super Air Nozzle for your blow off application – good call! – and now you’re thinking about how to install it.  Sometimes, it’s as simple as replacing whatever you’re using right now:

EXAIR Intelligent Compressed Air Products have common NPT (or BSP) connections, making for easy replacement of most any existing threaded device.

Or maybe you’re using an open end blow off…in which case, you’re just an adapter away:

EXAIR Super Air Nozzles are quick and easy to install on existing copper tube, via a simple compression fitting.

Perhaps, though, it’s a new installation, or the existing supply lines aren’t suitable for one reason or another.  In those cases, we’ve still got you covered…consider the EXAIR Stay Set Hose:

Precise aiming and location is a breeze with EXAIR Stay Set Hoses.

Available in a variety of lengths from 6″ to 36″, they’re positionable, and re-positionable with a simple bending action.  They won’t kink or easily fatigue like copper tubing.  The supply end is 1/4  MNPT, and you have your choice of 1/4 MNPT or 1/8 FNPT on the other end, depending on which Super Air Nozzle, Air Jet you need to use it with.

We also offer Blow Off Systems, which are a combination of a specific Air Nozzle (or Air Jet,) fitted to a Stay Set Hose:

Model 1126-9262, for example, is a Model 1126 1″ Flat Super Air Nozzle with a 9262 Stay Set Hose.

For added convenience and ease of installation, these products can also come with a Magnetic Base:

Mag Bases come with one or two outlets. Stay Set Hoses come in lengths from 6″ to 36″.

Stay Set Hoses are also available with a variety of our Soft Grip Safety Air Guns, and they make the GEN4 Stay Set Ion Air Jet one of our most popular Static Eliminator products.  They’ve even been successfully applied with small Air Amplifiers and Air Knives…with certain limitations (spoiler alert: trying this with a 108″ Super Air Knife is going to be a definite “no.”)

Model 110003 3″ Aluminum Super Air Knife with 6″ Stay Set Hose & Magnetic Base.

From the beginning in 1983, EXAIR’s focus has been on being easy to do business with, and that goes from our friendly customer service to our expert technical support to our 99.9% on-time shipments (22 years and running) to designing our engineered products and value-added accessories with efficiency, safety, and ease of installation in mind.  If you want to find out more, give me a call.

Universal Air Knife Mounting System Saves You Time & Money

Using EXAIRS Universal Air Knife Mounting System greatly ease’s the installation of all Air Knives (Except PVDF).  It will save you the time and expense of designing and fabricating your own mounting system which will maximize your uptime and keep your staff focused on key plant tasks!

Please note the table below that highlights the recommended number of the Universal Air Knife Mounting System to use for the various length of Air Knives.

Length Of Air Knife Number of UAKMS
3″ – 18″ 1
24″ – 54″ 2
60″ 3
72″ – 95″ 4
96″ – 108″ 5

If you would like to discuss Universal Air Knife Mounting System, Air Knives or any EXAIR compressed air product, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer

Send me an email
Find us on the Web 
Follow me on Twitter
Like us on Facebook

 

Intelligent Compressed Air: Utilization of the Coanda Effect

Henri Coanda was a Romanian aeronautical engineer most known for his work developing what is today known as the Coanda effect. The Coanda effect is the propensity of a fluid to adhere to the walls of a curved surface. A moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line.  This effect is used in the design of an airplane wing to produce lift. The top of the wing is curved whereas the bottom of the wing remains straight. As the air comes across the wing, it adheres to the curved surface, causing it to slow down and create a higher pressure on the underside of the wing. This  is referred to as lift and is what allows an airplane to fly.

2695876474_d8e82d5ee4_z

The Coanda effect is also the driving force behind many of EXAIR’s Intelligent Compressed Air Products. Throughout the catalog you’ll see us talking about air amplification ratios. EXAIR products are designed to take advantage of this phenomenon and entrain ambient air into the primary air stream. Compressed air is ejected through the small orifices creating air motion in their surroundings. Using just a small amount of compressed air as the power source, Super Air Knives, Air Nozzles, and Air Amplifiers all draw in “free” ambient air amplifying both the force and the volume of airflow.

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.

Super Air Knives provide the greatest amount of air amplification at a rate of 40:1, one part being the compressed air supply and 40 parts ambient air from the environment. The design of the Super Air Knife allows air to be entrained at the top and bottom of the knife, maximizing the overall volume of air. Super Air Nozzles and Super Air Amplifiers also use this effect to provide air amplification ratios of up to 25:1, depending on the model.

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

The patented shim design of the Super Air Amplifier allows it to pull in dramatic amounts of free surrounding air while keeping sound levels as low as 69 dBA at 80 psig! The compressed air adheres to the Coanda profile of the plug and is directed at a high velocity through a ring-shaped nozzle. It adheres to the inside of the plug and is directed towards the outlet, inducing a high volume of surrounding air into the primary air stream. Take a look at this video below that demonstrates the air entrainment of a Super Air Amplifier with dry ice:

Utilizing the Coanda effect allows for massive compressed air savings. If you would like to discuss further how this effect is applied to our Super Air Knives, Air Amplifiers, and Air Nozzles give us a call. We’d be happy to help you replace an inefficient solution with an Engineered Intelligent Compressed Air Product.

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

Custom Shims – Literally A Breeze For EXAIR

As proud as we are of being able to ship most any catalog product, same day, from stock (99.9831% of the time for on-time shipping in 2017…22 years straight for 99.9% or better,) we take a certain amount of pride in our ability to offer custom solutions for challenging applications as well. Our Engineering and Production teams have a deep well of resources (knowledge, experience, and capability) to draw from, which allows us to meet those challenging applications head-on, in short order.

The one I’m writing about today isn’t exactly one of those challenging ones…

A machine fabricator had a special need for an Air Knife. It had to be Stainless Steel, and it had to be 30″ long. No problem so far…that’s a Model 110030SS 30″ Stainless Steel Air Knife, and it’s on the shelf. Thing is, they only needed 26″ worth of air flow; a full 30″ width was going to disturb, and maybe damage, the edges of the sheet of material that the air was being blown onto.

So we made a custom shim for the Air Knife.  Now, we make these all the time, in all kinds of configurations…hence the term “custom.”  Since this one was blowing onto a web where they didn’t want to disturb the material on the far edges, we made this shim to provide 26″ of flow, on center.  We could just as easily made it to provide 26″ of flow starting at one end or the other, or a specified distance from one end or the other.  Or 13″ of flow on both ends, with 4″ of no flow in the middle, for a total of 26″.

If your application is more challenging than a custom shim, we’ve also made Air Knives with (left to right) curved radius, special material (glass filled PEEK shown here,) flat, double-sided, and even one with end-mount threaded holes.

Regardless of how challenging (or not) your compressed air product application is, we’re here to discuss, any time you’re ready.  Call us.

 

Super Air Knife Improves Plastic Injection Molder Process

EXAIR commonly works with plastic injection molding companies. They produce top quality plastic parts from both commodity and engineering-grade resins for many diverse industries. The customer reached out to us with a problem. A mold that they were running was having some issues. The parts were not releasing and ejecting properly, causing the need to use a mold release, which was slowing down the process by a manual operation to the process.  Also, the parts were seeing push pin marks, causing cosmetic issues with the parts.  The customer wanted to explore using compressed air to blow the parts free.

Plastic Injection Mold
Typical Plastic Injection Mold

Based on the mold size and layout, a pair of 12″ Super Air Knives was installed.  The knives are oriented to blow straight down along the face of the mold, one knife per part tree.  The strong laminar flow of air hits the parts causing them to release and drop without the use of release agents.  Also, the push pin marks are within normal standards, eliminating the the cosmetic concerns.

gh_Super Air Knife 750x696

This is just one example of how intelligently using compressed air can help improve a process.  By using air knives for wide areas or using a 1″ Flat Super Air Nozzle for very small parts, or anywhere in between, we can help to solve your part ejection issues and make your process run better, faster, and with higher quality.

1126
1″ Flat Super Air Nozzle with Changeable Shims

If you would like to talk about Super Air Knives, Flat Nozzles or 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.

Brian Bergmann
Application Engineer

Send me an email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_BB

 

Injection Mold Photo – “Creative Commons Injection Mold” by Mitch Barrie is licensed under CC BY-SA 2.0

Line Loss: What It Means To Your Compressed Air Supply Pipe, Tubing, And Hose

“Leave the gun. Take the canolli.”

“What we’ve got here is failure to communicate.”

“I’ll get you my pretty, and your little dog too!”

“This EXAIR 42 inch Super Air Knife has ¼ NPT ports, but the Installation and Operation Instructions recommend feeding it with, at a minimum, a ¾ inch pipe…”

If you’re a movie buff like me, you probably recognize 75% of those quotes from famous movies. The OTHER one, dear reader, is from a production that strikes at the heart of this blog, and we’ll watch it soon enough. But first…

It is indeed a common question, especially with our Air Knives: if they have 1/4 NPT ports, why is such a large infeed supply pipe needed?  It all comes down to friction, which slows the velocity of the fluid all by itself, and also causes turbulence, which further hampers the flow.  This means you won’t have as much pressure at the end of the line as you do at the start, and the longer the line, the greater this drop will be.

This is from the Installation & Operation Guide that ships with your Super Air Knife. It’s also available from our PDF Library (registration required.)

If you want to do the math, here’s the empirical formula.  Like all good scientific work, it’s in metric units, so you may have to use some unit conversions, which I’ve put below, in blue (you’re welcome):

dp = 7.57 q1.85 L 104 / (d5 p)

where:

dp = pressure drop (kg/cm2) 1 kg/cm2=14.22psi

q = air volume flow at atmospheric conditions (FAD, or ‘free air delivery’) (m3/min) 1 m3/min = 35.31 CFM

L = length of pipe (m) 1m = 3.28ft

d = inside diameter of pipe (mm) 1mm = 0.039”

p = initial pressure – abs (kg/cm2) 1 kg/cm2=14.22psi

Let’s solve a problem:  What’s the pressure drop going to be from a header @80psig, through 10ft of 1″ pipe, feeding a Model 110084 84″ Aluminum Super Air Knife (243.6 SCFM compressed air consumption @80psig)…so…

q = 243.6 SCFM, or 6.9 m3/min

L = 10ft, or 3.0 m

d = 1″, or 25.6 mm

p = 80psig, or 94.7psia, or 6.7 kg/cm2

1.5 psi is a perfectly acceptable drop…but what if the pipe was actually 50 feet long?

Again, 1.5 psi isn’t bad at all.  8.2 psi, however, is going to be noticeable.  That’s why we’re going to recommend a 1-1/4″ pipe for this length (d=1.25″, or 32.1 mm):

I’m feeling much better now!  Oh, I said we were going to watch a movie earlier…here it is:

If you have questions about compressed air, we’re eager to hear them.   Call us.

Russ Bowman
Application Engineer
Find us on the Web 
Follow me on Twitter 
Like us on Facebook