Turbine flow meter for use in fuel dispensing envirnoments

A turbine meter for measuring the flow of a fluid comprises a housing having an inlet port and an outlet port and defining a fluid flow path along a central axis thereof. A flow conditioner is mounted in the flow path downstream of the inlet port and has a plurality of flow deflectors canted in a first direction relative to the central axis. A first turbine rotor is located downstream of the flow conditioner and is mounted for rotation about the central axis. The first turbine rotor has a plurality of first rotor vanes canted in a second direction relative to the central axis, the second direction being opposite to the first direction. The meter further comprises a second turbine rotor located downstream of the first turbine rotor and mounted for rotation about the central axis. The second turbine rotor has a plurality of second rotor vanes canted in the first direction relative to the central axis such that the first and second turbine rotors rotate in opposite rotational directions when fluid flows through the housing at rotational speeds indicative of fluid flow rate.

BACKGROUND OF THE INVENTION

The present invention relates generally to turbine flow meters, such as those shown and described in U.S. Pat. Nos. 6,854,342, 6,692,535 and 5,689,071 (each of which is incorporated herein by reference in its entirety), for use in fuel dispensing environments. More particularly, the invention relates to a turbine flow meter adapted to have enhanced accuracy during low flow rate conditions.

Turbine flow meters may be used in a variety of applications in fuel dispensing environments. For example, turbine flow meters may be used to meter fuel being dispensed, measure the vapor being returned to the underground storage tank in a stage two vapor recovery system, or measure the vapor or air released to atmosphere from the ullage area of an underground storage tank when a pressure relief valve in a vent stack is opened to relieve pressure.

Turbine flow meters generally comprise a-housing having inlet and outlet ports at respective ends thereof. A shaft is located inside the housing along the housing's longitudinal axis. A turbine rotor mounted on the shaft rotates when fluid (liquid or gas) flows through the housing via the inlet and outlet ports. The rotor is made of a magnetic material such that its rotation is detected by a pickup coil mounted to the housing. As a result, the flow rate of the fluid flowing through the housing can be determined.

In some cases, the meter may have two turbine rotors, one located upstream of the other. If a respective pickup coil is provided for each rotor, the rotor frequency of each rotor can be determined. A controller divides the second rotor frequency by the first rotor frequency to derive a frequency ratio. This ratio can be used to determine the flow rate of the fluid flowing through the meter.

In a two-rotor meter, the downstream rotor will usually rotate even under low flow rate conditions. However, the velocity of the fluid may not be sufficient at low flow rates to rotate the upstream rotor. As a result, it may not be possible at low flow rates to determine the frequency ratio of the two rotors (and thus the fluid flow rate).

SUMMARY OF THE INVENTION

In accordance with one aspect, the present invention provides a turbine meter for measuring the flow of a fluid. The meter comprises a housing having an inlet port and an outlet port and defining a fluid flow path along a central axis thereof. A flow conditioner is mounted in the flow path downstream of the inlet port and has a plurality of flow deflectors canted in a first direction relative to the central axis. A first turbine rotor is located downstream of the flow conditioner and is mounted for rotation about the central axis. The first turbine rotor has a plurality of first rotor vanes canted in a second direction relative to the central axis, the second direction being opposite to the first direction.

The meter further comprises a second turbine rotor located downstream of the first turbine rotor and mounted for rotation about the central axis. The second turbine rotor has a plurality of second rotor vanes canted in the first direction relative to the central axis such that the first and second turbine rotors rotate in opposite rotational directions at rotational speeds indicative of fluid flow rate when fluid flows through the housing.

In some exemplary embodiments, the flow deflectors of the flow conditioner are rotor vanes and the flow conditioner is rotational about the central axis. For example, the flow conditioner may be configured to rotate in an opposite direction from the first turbine rotor when fluid flows through the housing. The vanes of the flow conditioner may be canted in an opposite direction but at substantially the same angle as the first rotor vanes. Alternatively, the flow conditioner may be nonrotatable.

Preferably, the meter may further comprise at least one detector affixed to the housing and operative to detect rotation of a corresponding one of the first and second turbine rotors. The at least one detector may comprise first and second detectors respectively associated with the first and second turbine rotors. In such embodiments, the detectors may be respective pickoff coils.

According to another aspect, the present invention provides a fuel dispenser for dispensing fuel to a vehicle. The dispenser comprises a nozzle, a hose connected to the nozzle and a control system. A fuel delivery line is in fluid communication with the hose. A valve is located inline the fuel delivery line and under control of the control system such that the control system opens the valve to allow fuel to flow through the fuel delivery line to be delivered through the hose and the nozzle to the vehicle.

The dispenser of the present invention further includes a turbine meter located inline the fuel delivery line. The turbine meter includes a housing defining a flow path between an inlet port and an outlet port. A flow conditioner having vanes canted in a first direction is mounted in the flow path. A first turbine rotor is mounted downstream of the flow conditioner and has vanes canted in a second direction opposite the first direction. A second turbine rotor is mounted on the shaft downstream of the first turbine rotor and is also rotational about the axis. The second turbine rotor has vanes canted in the first direction such that the first and second turbine rotors rotate in opposite directions when fuel flows through the housing. First and second detectors are operative to detect rotation of a respective one of the first and second turbine rotors.

A still further aspect of the present invention provides a turbine meter for measuring the flow of a fluid. The meter comprises a housing defining a fluid flow path. A flow conditioner is mounted in the flow path and has a plurality of flow deflectors canted in a first direction. A first turbine rotor located downstream of the flow conditioner has a plurality of first rotor vanes canted in a second direction opposite to the first direction. A second turbine rotor located downstream of the first turbine rotor has a plurality of second rotor vanes canted in the first direction such that the first and second turbine rotors rotate in opposite rotational directions when fluid flows through the housing. First and second detectors are respectively associated with the first and second turbine rotors to detect rotation thereof.

Other objects, features and aspects of the present invention are provided by various combinations and subcombinations of the disclosed elements, as well as methods of practicing same, which are discussed in greater detail below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1illustrates a pair of turbine flow meters10A and10B utilized in a fuel dispenser40. As is well-known, a fuel dispenser such as dispenser40is used to measure the amount of fuel being delivered to a vehicle (not shown). Accurate meters are required to measure fuel dispensing to comply with Weights & Measures regulatory requirements.

Fuel dispenser40may be a blending type fuel dispenser wherein a low-octane fuel41stored in a low-octane underground storage tank (UST)42and a high-octane fuel43stored in a high-octane underground storage tank (UST)44are blended such that fuel dispenser40may deliver either low-octane fuel41, high-octane fuel43, or a mixture of both to the vehicle. In this regard, low-octane fuel41is supplied to fuel dispenser40through a low-octane fuel supply conduit46. Likewise, high-octane fuel43is delivered to fuel dispenser40through a high-octane fuel supply conduit48. Both low-octane fuel41and high-octane fuel43pass through fuel dispenser40in their own independent flow paths. Each fuel41,43encounters a valve50,52that controls whether the fuel is allowed to enter into fuel dispenser40, and if so at what flow rate. U.S. Pat. No. 4,876,653 entitled “Programmable Multiple Blender,” incorporated herein by reference in its entirety, describes a system for blending low and high octane fuels. As either low-octane fuel41, high-octane fuel43, or both pass through their respective turbine meters10A,10B, the fuels come together in the blend manifold54to be delivered through a hose56and nozzle58into the vehicle. Valves50,52may be proportionally controlled by a controller60via control lines62,64.

Controller60determines when a fueling operation is allowed to begin. Typically, a customer is required to push a start button78and indicate which octane of fuel41,43is desired. Controller60thereafter controls valves50,52to allow low-octane fuel41or high-octane fuel43(or a blend of the two) to be dispensed, depending on the type of fuel selected by the customer.

After fuel41,43passes through respective valves50,52, it flows through the associated one of turbine meters10A,10B. If only a low-octane fuel41or high-octane fuel43was selected by the customer to be dispensed, controller60would only open one of the valves50,52. As fuels41,43flow through turbine meters10A,10B, pickoff coils on each of turbine meters10A,10B produce a pulser signal66,68that is input into controller60. Controller60determines the amount of fuel flowing through turbine meters10A,10B for the purpose of determining the amount to charge a customer for delivery of such fuel.

Controller60uses the data from the pulser signal66,68to generate a totals display70. Totals display70includes an amount to be charged to the customer display72, the amount of gallons (or liters) dispensed display74and the price per unit of fuel display76.

In other embodiments, a turbine meter of the present invention may be used in a vent stack of a underground storage tank at a service station. It may be desirable to measure the amount of air flowing through a vent stack using the meter to determine how often and how much air is separated by a membrane and released to atmosphere for any number of diagnostic or information purposes. The membrane may either permeate hydrocarbons or permeate oxygen or air as disclosed in U.S. Pat. Nos. 5,464,466 and 5,985,002, both of which are incorporated herein by reference in their entirety. In other embodiments, meter10may measure the amount of vapor being returned to the underground storage tank in a stage two vapor recovery system.

FIG. 2illustrates a meter10constructed in accordance with the present invention. Meter10includes a housing12that forms an inlet port14and an outlet port16for ingress and egress of fluid (liquid or gas), respectively. A shaft18or other support structure is located inside of housing12along a central axis A. A pair of turbine rotors20and21that rotate in a plane perpendicular to axis A are located at selected axial positions on shaft18. In this case, shaft18is stationary but supports rotors20and21for rotation. Generally, a bearing set will be interposed between each of the rotors and the shaft18to facilitate the respective rotor's rotation.

As shown, rotor20is located slightly upstream of rotor21. Accordingly, rotor20may be referred to as the “first turbine rotor,” with rotor21being referred to as the “second turbine rotor.” A flow conditioner24is also positioned in housing12, preferably located slightly upstream of first turbine rotor20.

Referring now also toFIG. 3, rotor20includes one or more vanes22(also known as blades) which cause rotation when impinged by the flowing fluid. Similarly, rotor21includes one or more vanes23. Vanes22and23are preferably spaced evenly around the periphery of the respective rotor hub. In addition, vanes22of rotor20are preferably canted oppositely from vanes23of rotor21. This orientation of vanes22and23causes the two rotors to rotate in opposite directions at a rotational speed related to the fluid flow rate. For example, a controller can determine the frequency ratio of one turbine rotor to the other in order to determine the fluid flow rate.

As will be described, flow conditioner24is provided to enhance performance of meter10at low flow rates (such as less than two gallons per minute in some embodiments). Flow conditioner24includes one or more vanes25(also known as blades) or other material deflectors, which cause flow through the meter to have a greater angle of incidence upon vanes22of upstream rotor20. As a result, rotor20will turn even under lower flow rate conditions. Thus, it is possible at very low flow rates to determine the frequency ratio.

In some embodiments, flow conditioner24may be stationary so that it does not rotate with respect to housing12. For example, flow conditioner24may be affixed to shaft18or housing12, or both. In other embodiments, flow conditioner24may be configured as a third rotor that rotates in a plane perpendicular to the axis of shaft18. Vanes25of flow conditioner24are preferably canted in an opposite direction from those of rotor20, as shown inFIG. 3.

In the illustrated embodiment, fluid entering housing12through inlet port14will encounter flow conditioner24generally in a direction parallel with axis A. (A flow straightener may be located upstream of flow conditioner24to further reduce turbulence in the entering fluid.) Because vanes25are canted, the straight fluid flow is converted into a generally swirling pattern with an angular trajectory based on angle27of vanes25. This angular trajectory is generally oblique to axis A, as shown. The angle of the flow impacting on the blades of the first rotor should be as close to perpendicular as possible to maximize the force component in the direction perpendicular to the rotation axis. This would accelerate each blade amplifying the effect of the flow conditioner.

After passing through flow conditioner24, the fluid impinges vanes22of rotor20. The angular trajectory of the flow due to flow conditioner24increases the fluid's angle of incidence with vanes22. As a result, the driving force used to impart rotational movement on turbine rotor20also increases. Accordingly, rotor20will rotate in direction32(in this case clockwise) as desired even during times of lower flow rates that are otherwise insufficient to turn rotor20if the flow is only axial.

In embodiments where flow conditioner24is rotatable, the flow may not be sufficient in some cases to turn flow conditioner24. Nevertheless, once the fluid travels through flow conditioner24, its angle of incidence will change. This facilitates rotation of rotor20in direction32, as desired. Rotor21will also rotate (in opposite direction36), thus permitting flow rate measurements to be taken. At higher flow rates, flow conditioner24will also begin to rotate as indicated at34(which is the same direction as36).

As vanes22and23of rotors20and21pass by respective pickoff coils29and30(FIG. 2) mounted to housing12, they create pulses at the respective coils. In particular, pickoff coils29and30are typically configured to generate a magnetic field that penetrates through housing12to reach the turbine rotors20and21. As the rotors20and21rotate, vanes22and23superimpose a pulse signal on the carrier waveform of the magnetic field. These pulse signals can be later analyzed by a microprocessor, such as controller60, or other suitable control system to determine fluid flow rate. For example, the frequency ratio of the signals at the two pickup coils can be determined as a basis for ascertaining the fluid flow rate. Instead of pickoff coils29and30, any other suitable technique for detecting the rotation of the rotors20and21may be used.

Referring now toFIG. 4, it may be desirable in some embodiments to have vanes25aof the flow conditioner (here designated24a) which are thicker on the downstream side (designated at38) in proximity to rotor20. This would choke the fluid somewhat with a smaller section to add some flow acceleration due to venturi effect. This may further help rotor20to move. It should also add some difference in speed between the two rotors20and21, but this could be compensated for in calibration.

While preferred embodiments of the invention have been shown and described, modifications and variations may be made thereto by those of ordinary skill in the art without departing from the spirit and scope of the present invention. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to be limitative of the invention as further described in the appended claims.