FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - A METHOD FOR DETECTION OF AIR IN FUEL
AND CONTROL OPERATION IN A FUEL DISPENSING SYSTEM
2. Applicant(s)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company.
(c)ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for detection of air in fuel and control operation in fuel dispensing system. More particularly, the invention is concerned about a method for detection of air in the fuel and stopping the system thereupon. The method further relates to indication of presence of air in the fuel in the fuel dispensing system.
BACKGROUND AND THE PRIOR ART
Traditionally, the mechanical spring operated valves are used to stop the pump when air entry in the fuel dispensing system. But this makes design complex and maintenance prone. Moreover, the response time of such systems is comparatively large.
In the document US 5884809, the difference in the pressure at the periphery and the center of centrifugal chamber is measured which in turn is indicative of presence of air. But here, pressure measurement is necessary at two places which are situated very much intricately in the pumping unit. While current invention involves no transducer to be installed and merely detecting the definite pattern flow rate is enough, making it a simple and cost effective solution.
In the document US 5363988, a fairly complicated arrangement with the principle of venturi effect is used to detect the presence of air. But a separate air detector has to be installed in the system downstream the pumping unit. While in the current invention there is no extra special component is required making it a very compact arrangement.
To overcome the problems in the prior art, the present invention provided a method for detection of air in the fuel

and upon detecting air, the dispenser stops and raises an alarm to indicate an air entry in the system. In the present invention, detection of flow rate is done with the help of pump electronic controller, making it a simple, fast and maintenance free design.
OBJECTS OF THE INVENTION
One of the basic objects of the present invention is to overcome the disadvantages/problems of the prior art.
Another object of the present invention is to provide a method for detection of air in the fuel.
Another object of the present invention is to provide a method for controlling dispensing operations when level of air in the fuel exceeds a predetermined threshold value in the system.
Another object of the present invention is to provide a method to indicate possible leakage in the suction line.
Another object of the present invention is to provide a method to indicate possible shortage of fuel in the tank.
Another object of the present invention is to provide a method to avoid inaccurate measurement and dispensing of fluid.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a method for detection of air in fuel and control operation in a fuel dispensing system, said method comprising:

determining flow rates of fuel at appropriate intervals of
time in a predetermined order for detecting air in said fuel
by electronic controller means; and
thereafter deactivating the system if said flow rates drop
below a predetermined threshold value within predetermined
interval of time;
optionally, indicating air in said fuel if said flow rates
drop below said predetermined threshold value by indicator
means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: illustrates a fuel dispensing system
Figure 2: illustrates a Pumping unit
Figure 3: illustrates a centrifugal chamber
Figure 4: illustrates a Vortex tube
Figure 5: illustrates the schematic diagram of the whole pumping unit
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
A fuel dispensing system is indicating different parts of the system namely a motor (1), a pumping unit (2), a metering unit (3} and a nozzle (4) as shown in fig. (1).
As shown in Fig. (2), the pumping unit (2) is a fuel-dispensing pump unit having air separation arrangement. The pumping unit comprises a positive displacement pump to draw the fuel from an underground tank. The embodiment of the present invention uses a vane pump (5) for the same. However,

the present invention can also be performed by using internal gear pump for drawing fuel from the underground tank. The vane pump (5) generates the vacuum at its inlet so that the fuel is drawn from the underground tank. The Fuel containing traces of air is pumped by vane pump towards the centrifugal chamber. The area of the channel joining the pump casing and centrifugal chamber is gradually decreasing and at the inlet of centrifugal chamber, there is an air separator cover. The air separator cover has a profile with gradually changing radii on its periphery which releases the fuel stream tangentially at the top of centrifugal chamber. At this point, fuel has a highest velocity.
As shown in the fig. (3), a helical flow is created in the centrifugal chamber after the fuel enters into it tangentially. The helical flow results into the formation of vortex of aerated fuel.
Consider a small fuel element in the fuel with mass (m) and density (p) with the tangential velocity (v) . If the pressure force and the centrifugal force experienced by the fuel element are equated, neglecting the gravitational force, the following equation can easily be arrived at:

Where, əp/ər is the pressure gradient in the radial direction. Thus, it is evident that since the pressure gradient is positive, the pressure increases as radius increases in the radially outward direction because of centrifugal force experienced by the element.

As a result, the aerated fuel tends to diffuse into the central region while dense fuel without any air remains at the periphery. This aerated fuel is collected by a tube means which is a vortex tube (6) and is delivered to vent chamber (8) . Here, the air escapes the fuel and is accumulated on the top of fuel.
As shown in fig. (3), aerated fuel collected by the vortex tube (6) is delivered to vent chamber (8) through a mechanism which has a plunger seated at its position with the help of a spring. Since aerated fuel is not having much density and pressure, it can't apply enough pressure at the area of plunger ahead of it and tries to pass through the opening provided in the plunger and finally escapes through vortex tube assembly (6) . But in the event of fuel with not much air in it, the fuel in the vortex tube (6) is dense and pressurized. So it pushes the plunger against the spring and ultimately blocks the exit path preventing it from passing to vent chamber (8) which otherwise would have over flown.
A method for detection of air in fuel and control operation in fuel dispenser system is described herein below:
In normal operation without air, the instantaneous flow rates are nearby the value allowed by nozzle opening. But as air introduced in system, the fuel flow rate falls to a value, hereafter referred to as threshold flow rate. A drop in flow rate depends on how much air is introduced into the system. As the amount of air increases, the threshold flow rate decreases.
In the present invention, as shown in figure 5, the electronic controller card (7) keeps calculating instantaneous flow rates of fuel at a definite interval of time, typically 500

milliseconds. As amount of air in the system increases, the drop in flow rate has a definite pattern as:
a) Flow rate gradually drops from maximum flow rate at the starting of the delivery to threshold flow rate giving a definite drop in flow rate.
b) This change in flow rate happens in a definite period of time.
c) The successive instantaneous flow rates calculated by electronic controller are in descending order.
d) Successive flow rate values during the drop are more than zero.
Electronic controller (7) monitors the flow rate and deactivates the motor (1) that drives the pumping unit (2) when this pattern is observed, thereby stopping the fuel delivery. Optionally, an indicator means is a provision to raise an alarm in the form of an indication on dispenser display, an LED blinking or an audible alarm as required by the customer can also be provided.
It's necessary to differentiate the flow rate drop pattern with air from the flow rate drop pattern during any normal operation without air, to avoid stopping the fuel delivery unnecessarily. When user suddenly releases the nozzle, the flow rate sharply drops to zero. But in this condition, the successive flow rates are zero, hence electronic controller card (7) treats it as nozzle inactivity. Many times, operators on the field close and open the nozzle fast and repeatedly. This causes a pattern of increase and decrease in flow rates wherein there may be an appreciable decrease in flow rates between successive instantaneous flow rates. But since the successive flow rates are not in descending order, it is differentiated from the pattern during air injection.

ADVANTAGES OF THE INVENTION
i) Excess air is detected and fuel delivery is not allowed, avoiding any inaccurate deliveries to end customer.
ii) When there is excess air, an alarm is raised which is indicating excess air and alert the operators.
iii) Possible leaks in suction line are indicated.
iv) Since, leaks are indicated, possible soil pollution is avoided if leaks are fixed.
V) Possible fuel shortage in storage tank is indicated.

WE CLAIM
1. A method for detection of air in fuel and control
operation in a fuel dispensing system, said method
comprising:
determining flow rates of fuel at appropriate intervals of time in a predetermined order for detecting air in said fuel by electronic controller means; and thereafter deactivating the system if said flow rates drop below a predetermined threshold value within predetermined interval of time;
optionally, indicating air in said fuel if said flow rates drop below said predetermined threshold value by indicator means.
2. The method as claimed in claim 1, wherein said flow rates of fuel at appropriate intervals of time are more than zero during the drop of flow rates.
3. The method as claimed in claim 1, wherein said flow rates of fuel at appropriate intervals of time are in descending order.
4. The method as claimed in claim 1, wherein said indicating means comprises dispenser display unit, LED blinking and/or an audible alarm.
5. The method for detection of air in fuel and control operation in fuel dispenser system as herein substantially described and illustrated with the accompanying drawings.