Giovanni

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

I know it has been a little while since I blogged about something with a motor so it should be no surprise that this one ties to something with a combustion chamber. This all starts with an Italian physicist, Giovanni Battista Venturi. His career was as a historian of science and a professor at the University of Modena. He gave Leonardo da Vinci’s creations a different perspective by crediting da Vinci to be a scientist with many of his creations rather than just an amazing artist. He then began to study fluid flow through tubes. This study became known as the Venturi Tube. The first patents in 1888 came to fruition long after Giovanni passed away. So what was this Venturi effect and how does it tie in to carburetors let alone compressed air?

The illustration below showcases the Venturi effect of a fluid within a pipe that has a constriction. The principle states that a fluid’s velocity must increase as it passes through a constricted pipe. As this occurs, the velocity increases while the static pressure decreases. The pressure drop that accompanies the increase in velocity is fundamental to the laws of physics. This is another principle we like to discuss known as Bernoulli’s principle.

Some of the first patents using Venturi’s began to appear in 1888. One of the key inventors for this was Karl Benz who founded Mercedes. This is how the Venturi principle ties into combustion engines for those that do not know the history. This patent is one of many that came out referencing the Venturi principle and carburetors. The carburetors can vary considerably in the complexity of their design. Many of the units all have a pipe that narrows in the center and expands back out, thus causing the pressure to fall and the velocity to increase. Yes, I just described a Venturi, this effect is what causes the fuel to be drawn into the carburetor. The higher velocity on the input (due to this narrowing restriction) results in higher volumes of fuel which results in higher engine rpms. The image below showcases Benz’s first patent using the Venturi.

While carburetors slowly disappear and now can mainly be found in small engines such as weed eaters, lawn mowers, and leaf blowers, the Venturi principle continues to be found in industry and other items. Needless to say, I think Giovanni Battista Venturi would be proud of his findings and understanding how monumental they have been for technological advancements. For this, we will recognize the upcoming day of his passing 199 years ago on April 24, 1822.

Brian Farno
Application Engineer
BrianFarno@exair.com
@EXAIR_BF

1 – Thierry Dugnolle, CC0, Venturi.gif, retrieved via Wikimedia Commons https://upload.wikimedia.org/wikipedia/commons/1/16/Venturi.gif

2 – United States Patent and Trademark Office – Benz, Karl, Carburetor – Retrieved from https://pdfpiw.uspto.gov/.piw?Docid=00382585&homeurl=http%3A%2F%2Fpatft.uspto.gov%2Fnetacgi%2Fnph-Parser%3FSect1%3DPTO1%2526Sect2%3DHITOFF%2526d%3DPALL%2526p%3D1%2526u%3D%25252Fnetahtml%25252FPTO%25252Fsrchnum.htm%2526r%3D1%2526f%3DG%2526l%3D50%2526s1%3D0382,585.PN.%2526OS%3DPN%2F0382,585%2526RS%3DPN%2F0382,585&PageNum=&Rtype=&SectionNum=&idkey=NONE&Input=View+first+page

Tag: Giovanni

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

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