FIELD OF THE INVENTION [0001 ] The present invention relates to a method and system for measuring the velocity and flow rate of a body of fluid passing through a pipeline or open channel.

BACKGROUND OF THE INVENTION

[0002] Traditional methods for measuring velocity and flow rate through a pipe or open channel have measured the time for a waveform (usually acoustic) to travel through a fluid in order to estimate average velocity and therefor, flow. [0003] The two common approaches have been Transit Time' and Ooppler'. The transit time approach measures directly the time to travel between two sensors where the difference between times travelling with the flow is faster than the times against the flow. The time difference is used to derive average velocity. The Doppler approach, on the other hand, relies on the sound waves being reflected by particles in the fluid and the resultant flow is derived from the Doppler shift in the times obtained using this method. A fuller description may be found in the online reference Wikipedia for these two methods. OBJECTS OF THE INVENTION

[0004] It is an object of the present invention to provide a method and system for measuring the velocity and flow rate of fluid passing through a pipe or open channel that does not use the transit time or Doppler approach but can utilise the sensors of the prior art. SUMMARY OF THE INVENTION

[0005] The present invention in one aspect provides a method of measuring the velocity and flow rate of a body of a fluid passing through a pipe or open channel, said method including the steps of : monitoring the decay or attenuation rate of the amplitude of reflected waveforms from at least one sensor located within said pipe or said open channel, determining a relationship or algorithm for said flow rate using calculations derived from system identification techniques based on data received from the monitoring of the decay or attenuation rate of the amplitude of reflected waveforms from said at least one sensor, and once said relationship or algorithm has been determined, using said relationship or algorithm to subsequently measure said flow rate.

[0006] In a further aspect of the invention provides a method of determining the velocity and flow rate of a body of a fluid passing through a pipe or open channel, said method including the steps of : monitoring the decay or attenuation rate of the amplitude of reflected waveforms from at least one sensor located within said pipe or said open channel, and determining a relationship or algorithm for said flow rate using calculations derived from system identification techniques based on data received from the monitoring of the decay or attenuation rate of the amplitude of reflected waveforms from said at least one sensor.

[0007] Preferably when said fluid passes through said pipe, said reflected waveforms are reflected from an opposing inner wall of said pipe; and when said fluid passes through said open channel, said at least one sensor is located on the bottom of said open channel and said reflected waveforms are reflected from the top surface of said fluid. It is preferred that said at least one sensor is acoustic or radar based.

[0008] In a preferred embodiment a plurality of separate waveforms are generated by said at least one sensor. The separate waveforms can include a double pulse or variation in frequency. The embodiment may also include a time delay between said plurality of separate waveforms.

[0009] The embodiments may include the filtering of scattered reflected waveforms. The use of waveform shaping, waveform diversity and/or waveform design may provide an enhanced detection capability. A plurality of sensors may also be used.

[0010] In another aspect there is provided an apparatus to measure the velocity and flow rate of a body of a fluid passing through a pipe or open channel, the apparatus including at least one sensor that generate waveforms in said fluid and monitoring the decay or attenuation rate of the amplitude of reflected waveforms from at least one sensor located within said pipe or said open channel using a computer controller or software control, determining a relationship or algorithm for said flow rate using calculations derived from system identification techniques based on data received from the monitoring of the decay or attenuation rate of the amplitude of reflected waveforms from said at least one sensor, and once said relationship or algorithm has been determined, using said relationship or algorithm to subsequently measure said flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011 ] The structure and functional features of preferred

embodiments of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: -

[0012] Fig. 1 is a diagrammatic cross-sectional view of a first embodiment of the invention showing the use of a single sensor in a pipe where there is no flow through the pipe;

[0013] Fig. 2 is a similar view to that of Fig. 1 where there is flow through the pipe;

[0014] Fig. 3 is an enlarged view of the reflection of waves from the inner surface of the pipe in Fig. 1 where the pipe has a smooth inner surface;

[0015] Fig. 4 is a similar view to that of Fig. 3 where the pipe has an irregular inner surface;

[0016] Fig. 5 is a graph of the amplitude of the reflected waveforms measured by the sensor against time;

[0017] Fig. 6 is a similar view to that of Fig. 2 using a plurality of sensors; and

[0018] Fig. 7 is a diagrammatic cross-sectional view of a second embodiment of the invention showing the use of multiple sensors in an open channel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Throughout this specification the same reference numerals will be utilised, where applicable, to avoid repetition and duplication of description across all embodiments. The description of constructions and operation will be equally applicable.

[0020] Fig. 1 shows a pipe 10 through which a fluid, typically water, flows. The invention is not limited to the use with water as it could be used with gaseous mixtures or slurries. A sensor 12, typically a transceiver, which can transmit and receive a waveform is fitted to the inside of pipe 10 in a fluid tight manner. The transceiver 12 may produce ultrasonic or radar waveforms but is not limited to those waveforms. Transceiver 12 may be substituted by a separate

transmitter and separate receiver (not shown). The waveform

frequency spectrum is not restricted and can, for example, include light, sound and radio.

[0021 ] In use, transceiver 12 generates a waveform 14 that reflects off the inner surface 16 of pipe 10 to provide reflected waveforms 18. The amplitude of each reflected waveform 18 will generate respective signals by said transceiver 12. The invention relies on the reflection of the waveform (that originated from transceiver 12) many times within pipe 10 and transceiver 12 detecting each of the reflected waveforms 18 and in turn measuring the decay or attenuation of the amplitude of each of the reflected waveforms 18. There will be an attenuation or decay of the amplitude of reflected waveform 18 over time due to natural travel through the fluid and also scatter on inner surface 16. This new approach is to generate a wave (e.g. acoustic or radar waveform) and measure the decay in amplitude of the reflected waveforms over a period of time. In stationary water (as shown in Fig. 1 ), the amplitude of the returning waveform will have a repeatable amplitude decay characteristic. As the flow changes the decay characteristic will change and this will be repeatable for the given physical environment and the same flow. The rate of attenuation of the amplitude of the waveform will increase as the flow 20 increases (Fig. 2). This will be as a result of the deflection of the reflected wave caused by the moving fluid. All signals from transceiver 12 will be monitored and processed by computer(s) (not shown).

[0022] Using 'system identification' techniques, an algorithm can be developed which defines the relationship between flow and the decay characteristics of the amplitude of the reflected waveform. This relationship will be derived using experiments that gather a range of data over a wide flow range. The field of system

identification uses statistical methods to build mathematical

models of dynamical systems from measured data. System

identification also includes the optimal design of experiments for efficiently generating informative data for fitting such models as well as model reduction. A dynamical mathematical model in this context is a mathematical description of the dynamic behaviour of a system or process in either the time or frequency domain.

[0023] Once the relationship or algorithm has been determined by experimentation, the relationship or algorithm can be incorporated in an electronic, software or computer control device (not shown). The electronic, software or computer control device will then monitor the flow through pipeline 10 and accurately measure flow rate therethrough.

[0024] Fig. 5 is a graph of the amplitude of the reflected waveforms 18 measured by the sensor 12 against time. Q ₀ is the graph of the stationary fluid shown in Fig. 1 and Qi and Q ₂ shows the variation at predetermined flow rates. From these measurements and the use of system identification techniques the flow rate can be determined in real time.

[0025] The waveform scatter properties of the pipe inner surface 16 material will also be a dependent variable in the decay characteristics of the reflected waveforms 18. A preferred implementation may be to use a conduit lining material that minimizes the waveform scatter. Fig. 3 shows a smooth inner surface 16 where the incident waveforms 22 have consistent reflected waveforms 24 whereas Fig. 4 shows a roughened inner surface 16 where the reflected waveforms 26 are scattered. A smooth plastic pipe would be preferred but roughened metallic pipes could also be used. Electronic filtering techniques could be applied to the measured signals to smooth the measured scattered signals using software.

[0026] The physical implementation of this invention will be largely applicable to pipe flow measurement as previously discussed but does not exclude its application to other non-circular conduits.

In addition, this invention could also apply to flow measurement in open conduits. Fig. 7 shows an open channel 30 with a bottom 32 and plateaus 34, 36. One or more sensors 12 may be placed on the bottom 32 and/or plateaus 34, 36. The waveforms 14 would be reflected by the surface 38 of the fluid and returned as reflected waveforms 18. The depth A, B, C of the fluid at could also be derived using this technique using the sensors 12. The use of multiple sensors 12 in this

embodiment or the embodiment in Figs. 1 and 2 may be used to improve the flow measurement accuracy or to accommodate nonuniform profiles of the channel or pipeline in which the fluid is being transported. [0027] A further embodiment of this invention may employ waveform shaping (or waveform diversity or waveform design) to achieve improved detection performance. This approach would use the power, frequency and time domain aspects of the waveform in order to create a signal that results in enhanced detection capability.

[0028] In a further embodiment separate waveforms can be generated which could include a double pulse or variation in frequency. A time delay between the separate waveforms can also be applied.

[0029] The invention will be understood to embrace many further modifications as will be readily apparent to persons skilled in the art and which will be deemed to reside within the broad scope and ambit of the invention, there having been set forth herein only the broad nature of the invention and certain specific embodiments by way of example.