Patent ID: 6293156
Filing Date: 2001-09-25
Classification: G01F

Abstract:
An ultrasonic measurement system for measuring a fluid flow of a low density gas, steam or two-phase fluid in a conduit, the conduit having a conduit wall, said system comprisingan ultrasonic signal transmitter which clamps to the conduit to launch an ultrasonic signal in the wall of the conduita first receiving transducer and a second receiving transducer clamped to the conduitthe ultrasonic signal transmitter being coupled to the wall to launch the ultrasonic signal such that said ultrasonic signal skips within the conduit wall with a characteristic skip distance L.sub.p coherently energizing a region of the wall such that ultrasonic signal energy effectively enters the fluid along spaced-apart paths obliquely crossing said flow and travels across the conduit being modulated by flowing inhomogeneities therein, said ultrasonic transmitter being mounted so as to create a shadow zone distinct from said coherently energized regionthe first receiving transducer and the second receiving transducer being spaced apart and positioned on said conduit in the shadow zone of the ultrasonic signal transmitter to receive signal energy from the ultrasonic signal that has been modulated in passing along different ones of said paths thereby producing respective first and second receiver output signals, anda processing system associated with the first receiving transducer and the second receiving transducer to correlate the first and second receiver output signals to determine a time delay indicative of flow velocity in the conduit.