Venturi meter experiment

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Venturi meter experiment

It is the function of the carburetter to provide good atomization and the correct mixture strength, under all operating conditions of the engine. The method used to do this in all carburetters is to speed up the velocity of the air by means of a venturi or choke, and to use the consequent reduction of pressure in the venturi to draw fuel from the float chamber through a suitable jet orifice into the air stream.

Venturi meter experiment

Since the power that an engine can develop is dependent upon the quantity of air consumed, it is desirable that the mixture of fuel and air should be carried out with as little restriction as possible to the overall air flow.

On a fixed choke carburetter the venturi must be sufficiently small to ensure adequate mixing during conditions of low air consumption. On engines that require to operate over a wide speed and power range, it is inevitable that a choke sufficiently small for use with low air consumption will give an excessive depression at maximum air flow.

An obvious solution to this problem is to arrange for the size of the choke to be increased at high engine output and decreased for bottom end performance.

The increasing number of cars using carburetters made to this same basic principle indicate that the idea was sound. The near constant depression, maintained in the carburetter under all operating conditions, is obtained by means of automatic regulation of the choke size. It is sufficiently high to ensure that good atomization is obtained, yet the depression is kept as small as possible in order to maintain engine filling at a maximum.

At the same time as the main passage above the jet is varied so too is the area of the fuel jet by means of a tapered' needle, the whole being regulated by the rise and fall of the piston under the influence of throttle opening and manifold depression.

This depression is itself dependent on the power requirement of the engine under the conditions at which it is being operated.

In this system one jet only is used and the avoidance of multiple jets means that any possibility of flat spots, which may occur during the change- over from one jet to another, is eliminated.


Correct jet discharge areas are obtained by the accurate dimensioning of the needle, which must be carefully matched to the requirement of the particular installation. In addition a dual choke instrument designated the DU6 has been manufactured in very limited quantities.

This latter type has, however, never been made in large production quantities, nor is it anticipated that it ever will be. The H type carburetter This is, perhaps, the most familiar type of S. It is shown in diagrammatic form in Fig.

It has been made in horizontal and semi-downdraught form with throttle disc sizes ranging from I i in.

As with all current S. This number indicates the diameter of the butterfly, and is the number of eighths of an inch that the diameter is larger than I in. The height to which the piston is lifted is controlled by the amount of air passing beneath it.

When the piston is at the bottom of its stroke, with the engine idling, opening the butterfly allows the manifold depression to be communicated to the main volume of the body and then through a cross drilling in the lower part of the piston into the suction chamber above the piston.

This depression immediately lifts the piston, allowing a mixture of air and fuel to pass the lower side of the piston and relieve the depression. The piston height is therefore stabilized at a depression controlled by the weight of the piston, the load of the piston spring, and: It will be noted that the underside of the large diameter of the piston is open to atmosphere.

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The optimum dimensions of this needle are normally found by experiment on an engine dynamometer, and by road testing of the vehicle. Once determined, a profile cam is made to give the desired needle dimensions, and production needles can then be very accurately reproduced to the desired shape.

From this it will be seen that once the correct needle has been specified, the jet has to be set to a datum dimension on the needle to ensure that the desired mixture is obtained throughout the range of the engine operating conditions.

This position is set when the carburetter is tuned for idling. This one way damping is obtained by means of a non-return valve situated at the base of the damper. When the speed of piston lift is retarded an additional air depression is put on the fuel in the jet resulting in an increase in the quantity of fuel discharged.

A richer mixture is thus obtained until the piston resumes its position of equilibrium. This enrichment is necessary to provide satisfactory pick-up. The piston damper also improves cold starting and driveability from cold. It is of the utmost importance that the fuel jet is assembled concentric with the needle.B.B., Discovering and knowing the origins of words and names has long been a fascination of mine, so I read this report with great interest.

Also, I have several 10 meter springers, each of which, save an FWB s Jr., is outfitted with a bull barrel sleeve. Venturi Meter. A. venturi meter is a measuring or also considered as a meter device that is usually used to measure the flow of a fluid in the pipe.A Venturi meter may also be used to increase the velocity of any type fluid in a pipe at any particular point.

It basically works on the principle of Bernoulli's Theorem.

Venturi meter experiment

Get up-to-the-minute environmentally-friendly (or egregiously unfriendly) car news, reviews, high-quality photos and commentary about living green. The major objective of this experiment was to construct, test and model a simple, inexpensive venturi meter.

More specifically, this simple venturi meter, constructed from materials available. Sep 14,  · Fig. 1 - Venturi Meter www. EXPERIMENTAL PROCEDURE - The apparatus was leveled by opening both the Bench Supply valve and the control valve downstream of the meter to allow water to flow and clear air pockets from the supply hose/5(24).

Aug 08,  · Atmospheric Pressure The earth's atmosphere exerts a force on everything within it. This force, divided by the area over which it acts, is the atmospheric pressure.

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