Carburetors and Venturi Tubes: Thank You Giovanni Battista Venturi

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.

1 – Venturi

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.

2 – Venturi Patent

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

Turn It Off: Saving Compressed Air The Easy Way

A major benefit to utilizing compressed air is the speed at which it can be shut off and re-energized for use – in fact, this can be done instantaneously. Shutting down the supply of compressed air to an application while it is not needed can drastically reduce the compressed air consumption of the process. This is an easy remedy that can produce significant savings.

Think about a place where you have a compressed air blow off with spaces between the parts or dwell times in conveyor travel. What about break times, do operators continue to keep the air on when they leave for a break or even worse, for the day?

Step number four in EXAIR’s Six Steps to Optimization is:

A simple manual ball valve and a responsible operator can provide savings at every opportunity to shut down the airflow. But an automated solution is a no-brainer and can provide significant savings.

Quarter Turn Ball Valves are low-maintenance and easy to install/use.

For a more automated approach, you can add a solenoid valve that would tie into your existing PLC or e-stop circuit, into your compressed air supply lines to aid in turning the compressed air on and off.

For an automated on/off solution can be found by using the EXAIR EFC (Electronic Flow Control). The EFC is made to accept 110V or 220V AC, and convert it to 24V DC to operate a sensor, timer, and solenoid valve. Its multiple operating modes allow you delay on, delay-off, and delay on/off among others. The operating mode can then be set to the specific time necessary for a successful application.

The spaces between parts can be turned into money saved. Every time you reach the end of a batch run, the EFC can turn the air off. You can also add solenoid valves and run them from your machine controls. If the machine is off, or the conveyor has stopped – close the solenoid valve and save the air. The modes are all defined in the video below.

So, take a look, or even better a listen, around the plant and see what you can find that could benefit from turning the air off; even if it is just for a moment it will help put money back into your bottom line.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Tools Of The Trade: The Rotameter

EXAIR’s Free Efficiency Lab

One of the free services we offer to customers here at EXAIR is our Efficiency Lab. In case you are not familiar here is a brief synopsis. Speak with an Application Engineer about your existing compressed air blowoff/point of use product and that you would like to know how much air it consumes. Fill out the brief survey and send the product you use in to our facility. Let us perform tests on calibrated test equipment to determine the force, flow, and noise level. We will then issue you a report that states what the EXAIR model would best be suited (if applicable) as well as how much compressed air you will be able to save. Order the recommendation and start saving money.

To do these evaluations, we have to have calibrated equipment that is reliable and capable of handling vast range of products we may receive in. For this, we could use a Digital Flowmeter, in some cases that is what has to be done due to large flow rates. For the majority of these though we go old school. We utilize a piece of equipment called a rotameter.

A rotameter pairs nicely with a calibrated pressure gauge as well.

The float can be seen with graduated marks for readings. The taper of the chamber is not easily seen with the naked eye.

This is a device that is designed to measure the flow rate of a fluid within a closed tube. The inside diameter of the tube is varied which causes the float within the meter to raise or lower.  They are calibrated for a specific gas at a given pressure and temperature, most are calibrated for atmospheric conditions, 14.7 psi (1.014 Bar). The meter must be mounted vertically and this is not always best suited for industrial environments.

When testing products the compressed air within the meter is pressurized which means we have to correct the reading for the given pressure, if the temperature is outside of the calibration temp then we must also perform that correction. We do this using a table provided by the manufacturer of the meter or by using the calculations shown to get exact values that may be in between the pressures in the table.

Pressure Correction Table

 

This will allow us to then multiply the Correction Factor by the meter reading and calculate our corrected flow for the point of use device at a given operating pressure and temperature.

Temperature correction table

Knowing where the values that are measured and calculated come from add validity to the reports and understanding all of the variables that go into reading like this helps to better validate the cost savings that can be seen.

In a pinch, for a field estimation, we can also use these Correction Factors and determine an approximate consumption rate of a device that has been measured at a pressure such as our cataloged 80 psig (5.5 Bar). This can often be done on the fly to help determine the flowrates currently on a system. This can be helpful when troubleshooting, giving estimated simple ROIs, and help justify results and reasons for future purchases of engineered solutions.

If you want to discuss the Efficiency Lab or any of the math behind our calculations, contact any Application Engineer, we can all help out.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Super Air Wipe at Sea

I recently worked with a Chief Engineer on a large shipping boat who was having issues with water being brought in by the mooring cables. That salt water was getting into the maintenance room where the mooring cables were wound around a large spool. He wanted to remove the water from the cable before it went below deck so the extra water could just run off the deck back into the ocean.

After talking a bit we decided on a 4″ Super Air Wipe constructed of 303 stainless steel. This way the extra water would be removed and any debris the cable pulled in with it.

Mooring Cable going thru a EXAIR Super AirWipe

The Super Air Wipes provide a full 360° conical airflow that is used to blow-off, cool, clean and dry products. A Coanda profile is designed into the body of the unit to maximize entrainment of ambient air as well as give the precision angle for the air to exit from. This gives the air stream impacting the target zone a 30° angle to the surface in order to provide a substantial shear force for debris removal. This also ensures the large volume of ambient air entrained will all travel the correct direction and not become turbulent before impinging on the surface.

To meet all the tasks at hand, the Super Air Wipes are offered in two main materials of construction. Aluminum body with brass air fittings, connected with stainless steel hardware, shim and connecting hose for up to 4” (102mm). As well as 303 stainless steel body with stainless steel bolts, shim, the connecting hose for up to 4” (102mm) and fittings. The stainless-steel components give the units better corrosion resistance, higher temperature ratings, and more durability in harsh industrial environments.

The aluminum Super Air Wipe is available in 11 sizes; the stainless steel Super Air Wipe comes in 5 sizes…all from stock.

EXAIR stocks the aluminum Super Air Wipes with inner diameters from 3/8” (10 mm) for wire and cables up to 11” (279mm) for large pipes and hoses. The aluminum models have a temperature rating up to 400oF (204oC). We also stock the stainless-steel models from ½” (13mm) to 4” (102mm) inner diameters, and they have a temperature range up to 800oF (427oC). If you require different diameters or materials, we can do that as well easily.

With the creation of the Super Air Wipe, uniform cleaning, cooling, and blowing around the outside of parts is a simple task. You don’t have to worry about a variety of nozzles to target the circumference or a fabricated blow-off device that will waste air and take much time out of your day. A simple purchase of the Super Air Wipe Kit will solve the problem and keep production going. If you need help in selecting the proper size or want to know what material we would recommend for your application, contact us.

Jordan Shouse
Application Engineer

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