LRWRP_Design_Report_Appendix_E.pdf

APPENDIX E

MGD ADFM Velocity Profiler

GENWAL

The ADFM Velocity ProfilerTM (ADFM) is a flow meter based on unique, pulse-Doppler technology. Pulse Doppler acoustics, combined with range-gating signal processing, allows the ADFM to measure a velocity profile - something that no other flow meter can do.

The ADFM consists of a transducer assembly mounted in the flow, a signal processing unit and an interface cable.

PRlNClPLES OF QPERATlON FIGURE 1 shows a typical ADFM installation for measuring open channel flow in a pipe. A transducer assembly is mounted on the invert of a pipe or channel. Piezoelectric ceramics emit short pulses along narrow acoustic beams pointing in different directions. Echoes of these pulses are backscattered from material suspended in the flow. As this material has rrotion relative to the transducer, the echoes are Doppler shifted in frequency. Measurement of this frequency enables the calculation of the flow speed. A fifth ceramic mounted in the center of the transducer assembly, and aimed vertically, is used to measure the depth.

The A ,DFM divides the return signal into discrete regular intervals that correspond to different depths in the flow. Velocity is calculated from the frequency shift measured in each interval. The result is a profile, or linear distribution of velocities, along the direction of the beam. Each of the rectangular yellow segments in FIGURE^ represent an individual velocity measurement in a small volume known as a depth cell.

The directions of the velocity profiles in FIGURE 1 are based on the geometry of the ADFM's transducer assembly. FIGURE 2 shows a side view of the transducer assembly. The profiles shown in FIGURE 1 are generated from velocity data measured by an upstream and downstream beam pair.

The data from one beam pair are averaged to generate Profile #I, and a beam pair on the opposite side of the transducer assembly generates Profile #2.

Since Doppler measurements are directional, only the component of velocity along the direction of transmit and receive is measured, as shown in FIGURE 2. Narrow acoustic beams are required to accurately determine the horizontal velocity from the measured component. The narrow acoustic beams of the ADFM insure that this measurement is accurate. Also, the range-gate times are short and the depth cells occupy a small volume - cylinders approximately 5 centimeters (2 inches) long and 5 centimeters (2 inches) n diameter. This insures that the velocity measurements are truly representative of that portion of the flow.

Potential bias in the return energy spectrum due to range dependent variables is avoided. The result is a very precise measurement of the vertical and transverse distribution of flow velocities.

Flow Velocity Vector The velocity data from the two profiles are entered into an algorithm to determine a

Vector Component mathematical description of the flow velocities throughout the entire cross-section of the flow.

The algorithm fits the basis functions of a parametric model to the actual data. The result predicts flow velocities at all points throughout the flow. These results are integrated over the cross-sectional area to determine the discharge.

The key benefit to this approach is that the system will operate accurately under different hydraulic conditions. As hydraulic conditions change, the change will manifest itself in the distribution of velocity throughout the depth of flow. AS the ADFM is measuring the velocity distribution directly, it will adapt to the changes in hydraulics, and generate a flow pattern that is representative of the new hydraulic conditions, insuring an accurate estimate of flow rate.

PHYSICAL SPECIFICATION

The ADFM consists of a transducer assembly placed in the flow connected to a controlling set of electronics by a waterproof cable. The transducer assembly is designed to be intrinsically safe (IS) compliant. An optional IS Zener diode barrier may be mounted in an electronics assembly for interface to the transducer. The electronics can record data in a stand-alone mode, output data real-time via modem or serial communications, or do both. External AC, DC, or internal alkaline batteries power the system.

The ADFM Velocity ProfilerTM transducer assembly (shown to the right) contains four individual velocity transducers that use piezoelectric ceramics for emitting and receiving acoustic signals.

These four transducers measure velocity throughout the depth of flow. A fifth transducer is mounted in the center, pointed 204.00 vertically, to measure the depth of flow. The transducer assembly (8.03) casing is manufactured of plastic to provide years of corrosion free service.

(in.).

The electronics assembly contains the signal processing system. The assembly contains all signal processing boards, internal battery supply, and available options - a modem for telemetry, solid state memory for stand alone operation, and IS Zener diode barriers. An RS-422 and 232 serial interface is standard, as is a 4 line by 16 character LCD for quick determination of the system's status.

The electronics assembly housing for a permanent installation is shown at left and is rated NEMA 4X. The electronics assembly housing is also available in a canister form for installation in a manhole or other wet environment.

The canister is rated NEMA 6P.

All Dimensions are in millimeters

DATA MAWGEM ENT:

ADFM Velacity P&pflw" Data Qutpuk Q, V, 0: Discharge, average velocity, depth Velocity: Velocity profile data (relative to acoustic beam directions) per beam and bin Echo Intensity: Echo intensity data (relative backscatter intensity) per beam and bin velo~ity:

Velocity Range:

Velocity Bin Size:

+ 30.0 ftls 2 to 12 in. - user selectable

0.75 to 20 ft. nominal, for particle concentrations of 50 to 1000 ppm, operation down to 2 ppm 0.5% + 0.01 fffs of reading

Vertical Profiling Range:

Data Quality: Profile data quality indicators (Correlation magnitude, %-Good) per beam and bin Temperature: Transducer temperature output, range = 2 0 S T l 1 2 5 " F Accuracy:

Sound Speed:

Leader:

One output for speed of sound data Outputs of general leader information Water Level:

Measurement Range:

Accuracy:

(time, data, record number, etc.), and for vertical beam data

4.5 in. to 30 ft 0.5% f. 0.2 in. of reading

Bat@ Stamga f~ptlonalj:

Storage Capacity:

Electronics Unit:

Operating Temperature:

Storage Temperature:

Packaging:

20 MB std. (up to 440MB optional)

-15 to 125" F -65 to 160" F

IP 68 (NEMA 6P)

compliant 30 Ib.

Data: Interfaces:

Data 110: RS-232; RS-422;

Modem port (optional);

4-20 mA (optional)

Weight:

Transducer Signal Cable:

Operating Temperature:

Physical:

Length:

-40 to 125" F Polyethylene jacket 50 ft std. (up to 150 ft nntinnall

0.5 ft.

0.08 lblft nominal

0.5 in. nominal

POWER:

Internal Battery Voltage:

Internal Battery Capacity:

24 VDC nominal 13 Ah @ 75" F - Alkaline 22 weeks battery life @ 15 m i n ~ ~ t n samnlinn intanid

230 + 10% VAC;

115+ lO%VAC;

50160Hz 24 VDC - 12 VDC absolute minimum; 36 VDC absolute rncavirn~ am

Minimum Bend Radius:

Weight:

Outer Diameter: External AC:

Acoustic Frequency:

Frequency:

External DC:

1.23 MHz

ADFM VELOCITY PROFILERTM SOFTWARE:

WinADFM software for Windows '95

Hot Tap Ins.ertion Transducer:

Open Channel Transducer: Operating Temperature: 23 to 95" F Operating Temperature: 23 to 95' F Housing Material: Plastic transducer assembly Housing Material: Plastic on corrosion resistant Static Pressure: 250 psi Nominal stainless steel stem Weight: 2.2 Ib Static Pressure: 250 psi Nominal

Weight: 9 Ib

D CITY PROFILERTM

OW M

Sensor Mounting Band Installation For Circular Pipes

Full Band for Pipes s 48" Diameter Partial Band for Pipes > 48" Diameter

Pipe Walls

ADFM Sensor

ADFM Sensor

I

\ ~ o u n t i n ~ Band 4" Wide

3 Channels (Maximum) and Pulse Output

ADFM Electronics Unit

RS-2 3 2

Communications

Cable

A s--,

- Laptop Computer for Local ADFM System Configuration

-. & Data Downloads

ADFM

Sensor Cable

ADFM

Sensor :