Method and apparatus for measuring mass flow
First Claim
1. Method for measuring the mass flow M of a fluid flowing through a pipe having a cross-sectional area A, said method comprisinga) causing an ultrasonic pulse (U1) to traverse a distance (L) in the cocurrent direction of the fluid N times, where N is greater than or equal to 1;
- b) measuring the time (T1) it takes the ultrasonic pulse (U1) to traverse said distance (L) in the cocurrent direction of said fluid N times;
c) causing an ultrasonic pulse (U2) to traverse said distance (L) in the countercurrent direction of said fluid N times;
d) measuring the time (T2) it takes the ultrasonic pulse (U2) to traverse said distance (L) in the countercurrent direction of said fluid N times;
e) determining the flow velocity (v) of said fluid as
space="preserve" listing-type="equation">v=L (N/T.sub.1 -N/T.sub.2)/2 cosθ
where θ
is the angle between the longitudinal axis of the pipe and the direction of propagation of said ultrasonic pulse (U1 or U2),f) determining the sound velocity (c2) in said fluid as
space="preserve" listing-type="equation">c.sub.2 =L (N/T.sub.1 +N/T.sub.2)/2g) causing an ultrasonic pulse (U1, U2) to traverse a distance x0 in a first material having a density ρ
0 and thereafter a distance x1 in a second material having a density ρ
1, before being caused to traverse said fluid;
h) determining the sound velocity c0 and c1 in said first and said second material, respectively;
i) measuring the amplitude Ar1 of a part of said ultrasonic pulse (U1, U2) which is reflected in a boundary between said first and said second material and which thereafter again traverses the distance x0 in said first material;
j) measuring the amplitude At2r1 of a part of said ultrasonic pulse (U1, U2) which is reflected in a boundary between said second material and said fluid and which thereafter again traverses the distance x1 in said second material and the distance x0 in said first material;
k) determining the density ρ
2 of the fluid as ##EQU10## l) determining the mass flow M of said fluid as M=v×
A×
ρ
2.
1 Assignment
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Accused Products
Abstract
In a method for measuring the mass flow M of a fluid flowing through a pipe having a cross-sectional area A, the sound velocity c2 in the fluid is determined as well as the flow velocity v of the fluid by sing-around technique. Further, reflection technique is used which comprises measuring the amplitude both of an ultrasonic pulse which has been reflected in a boundary between a first and a second material having different acoustic impedances, and of an ultrasonic pulse which has been reflected in the boundary between the second material and the fluid, it being possible to determine the density of the fluid on the basis of the measured amplitudes, the sound velocity c2 in the fluid and the acoustic impedances of the first and the second material. The mass flow M is then obtainable as M=v×A×ρ2. A mass flowmeter especially has a transducer with a piezoelectric crystal (5), a first block (6) of a first material disposed adjacent said crystal, and a second block (7) of a second material disposed between the first block and the fluid, and calculating and amplitude metering means (10 and 12).
55 Citations
9 Claims
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1. Method for measuring the mass flow M of a fluid flowing through a pipe having a cross-sectional area A, said method comprising
a) causing an ultrasonic pulse (U1) to traverse a distance (L) in the cocurrent direction of the fluid N times, where N is greater than or equal to 1; -
b) measuring the time (T1) it takes the ultrasonic pulse (U1) to traverse said distance (L) in the cocurrent direction of said fluid N times; c) causing an ultrasonic pulse (U2) to traverse said distance (L) in the countercurrent direction of said fluid N times; d) measuring the time (T2) it takes the ultrasonic pulse (U2) to traverse said distance (L) in the countercurrent direction of said fluid N times; e) determining the flow velocity (v) of said fluid as
space="preserve" listing-type="equation">v=L (N/T.sub.1 -N/T.sub.2)/2 cosθwhere θ
is the angle between the longitudinal axis of the pipe and the direction of propagation of said ultrasonic pulse (U1 or U2),f) determining the sound velocity (c2) in said fluid as
space="preserve" listing-type="equation">c.sub.2 =L (N/T.sub.1 +N/T.sub.2)/2g) causing an ultrasonic pulse (U1, U2) to traverse a distance x0 in a first material having a density ρ
0 and thereafter a distance x1 in a second material having a density ρ
1, before being caused to traverse said fluid;h) determining the sound velocity c0 and c1 in said first and said second material, respectively; i) measuring the amplitude Ar1 of a part of said ultrasonic pulse (U1, U2) which is reflected in a boundary between said first and said second material and which thereafter again traverses the distance x0 in said first material; j) measuring the amplitude At2r1 of a part of said ultrasonic pulse (U1, U2) which is reflected in a boundary between said second material and said fluid and which thereafter again traverses the distance x1 in said second material and the distance x0 in said first material; k) determining the density ρ
2 of the fluid as ##EQU10## l) determining the mass flow M of said fluid as M=v×
A×
ρ
2. - View Dependent Claims (2, 3, 4)
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5. Apparatus for measuring the mass flow M of a fluid having an acoustic impedance Z2, comprising two means (3, 4) for transmitting and receiving ultrasonic pulses, said means being located opposite each other and at a distance L from each other in a pipe section having a cross-sectional area A, time metering means (9) for measuring the time it takes an ultrasonic pulse to traverse said distance L in the fluid N times, where N is greater than or equal to 1, calculating means (10) for calculating the flow velocity v of the fluid, and means for measuring the density ρ
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2 of the fluid, wherein said means for measuring the density ρ
2 comprises a first block (6) of a material having an acoustic impedance Z0 is disposed adjacent one of said means (3,
4) for transmitting and receiving ultrasonic pulses, a second block (7) of a material having an acoustic impedance Z1 is disposed between said first block (6) and the fluid, and amplitude metering means (12) for measuring the amplitude of ultrasonic pulses which have been reflected in the boundary between said first and said second block and between said second block and the fluid, and that the apparatus further comprises calculating means (10) for calculating the sound velocity c2 in the fluid on the basis of the times measured by said time metering means, the density ρ
2 of the fluid on the basis of the sound velocity c2, the acoustic impedances Z0 and Z1, and the amplitudes measured by said amplitude metering means (12), as well as the mass flow M according to the formula M=ρ
2 ×
A×
v, are included. - View Dependent Claims (6, 7, 8, 9)
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2 of the fluid, wherein said means for measuring the density ρ
Specification