Apostolos C. Raptis

Method for measuring liquid viscosity and ultrasonic viscometer

An ultrasonic viscometer and method for measuring fluid viscosity are provided. Ultrasonic shear and longitudinal waves are generated and coupled to the fluid. Reflections from the generated ultrasonic shear and longitudinal waves are detected. Phase velocity of the fluid is determined responsive to the detected ultrasonic longitudinal waves reflections. Viscosity of the fluid is determined responsive to the detected ultrasonic shear waves reflections. Unique features of the ultrasonic viscometer include the use of a two-interface fluid and air transducer wedge to measure relative signal change and to enable self calibration and the use of a ratio of reflection coefficients for two different frequencies to compensate for environmental changes, such as temperature.

Ultrasonic gas analyzer and method to analyze trace gases

An ultrasonic gas analyzer includes an acoustic cavity through which an air sample is drawn by a low speed air pump or other mechanism. The cavity has a pair of ultrasonic wave transmitters/receivers on opposite sides of the acoustic cavity. An electronic circuit controls the transmitters/receivers so that a high frequency ultrasonic wave is propagated across the cavity and thereby through the gas flowing through the cavity. This ultrasonic wave reflects back and forward across the acoustic cavity and the transmitters/receivers receive this wave and supply a signal indicative of the wave to an electronic circuit. Based on the time of flight data for the ultrasonic wave being reflected in a gas/air mixture and in air and the amplitude of those reflected ultrasonic waves, a determination is made as to the gases within the gas/air mixture. This determination then can be displayed and an audio signal can be generated depending on the amount of detected gases. In one embodiment of the gas analyzer, a switch valve is used to selectively provide the gas/air mixture or air through the acoustic cavity. In another embodiment of the gas analyzer, two acoustic cavities are provided with a double concave reflector lens separating the cavities and each with a transducer at an opposite end from the lens. Air is drawn through one of the acoustic cavities and the gas/air mixture is drawn through the other of the acoustic cavities

Ultrasonic Properties of Coal Slurries and Flow Measurements by Cross Correlation

The application of ultrasonic techniques to the measurement of coal concentration and flow velocity of coal slurries was investigated at the Hygas pilot plant. It was found that the sound attenuation in a coal slurry is linearly dependent on the coal concentration up to 35 wt% and provides a direct measurement with an uncertainty of 5 percent of actual coal concentration. An active crosscorrelation technique using an amplitude demodulation scheme can be used to measure the flow velocity of the coal slurry with an accuracy of 3 percent of full scale. Flow disturbances in the coal slurry, which are received by transducers spaced at 12.7-cm intervals, have frequency contents primarily in the range of 20-50 Hz. Based on the results of the feasibility test, an on-line ultrasonic mass flowmeter is proposed which would measure 1) the coal concentration based on the sound attenuation in the coal slurry and 2) the flow velocity for turbulent flow by means of an active cross correlation technique. I . INTRODUCTION HE MEASUREMENT of mass flow in coal conversion process streams is essential for the efficient, economic, T and safe operation of such plants. The streams are composed of crushed solids, usually coal char, or ash moving with liquids and/or gases. They range in composition from streams containing 2 5 0 vol% crushed solids to supposedly clean gas streams containing a few parts per million by volume of micron-size particles. Most of the existing commercial flowmeters are of the penetrating type and are not suitable for monitoring such streams because of the erosion problem, and they also tend to create plugging problems in the process lines [l] -[3]. In this paper the use of a nonpenetrating acoustic flowmeter based on the active cross-correlation principle will be discussed. The flowmeter is nonpenetrating in the sense that the transducers do not obstruct the flow,but transmit and receive through an acoustic window which fills an opening in the pipe wall. Feasibility studies and subsequent experiments have shown that acoustic flowmeters are feasible for flow measurements for turbulent and laminar flow regimes in coal conversion process streams [4] -[6] . The analyses in the feasibility studies and the interpretation of the experimental results were based on the sonar equation which states: “A received signal level is equal to the noise background level plus a measurement requirement [7] .” This equation considers such terms as the source level, the processing gain of the instrumentation, the directivity gain of the transducers, the transmission loss through the medium, and the noise background level. The first three terms are known quantities which depend on the Manuscript received May 10, 1980; revised February 14, 1981. The authors are with the Components Technology Division, Argonne National Laboratory, 9700 South Cass Ave., Argonne, IL 60439. choice of transducers and instrumentation. The latter two terms must be determined experimentally since the available literature data on them are limited [7], [8]. Data on the acoustic noise background and sound attenuation in the low-pressure coal slurry line of the Hygas pilot plant were first published by the authors in 1978 [9]. The Hygas Pilot Plant is a gasification process that utilizes a fluidized bed reactor, operating at pressures of 1000 to 1500 psig and temperatures in the range of 1300-180OoF to convert the major part of the carbon in coal to gases. Between 5 to 10 wt% of the coal feed is produced as a light aromatic oil, principally toluene. The process maximizes methane production in the reactor by using direct hydrogenation of coal [IO]. The concentration of solids in the line and the velocity of the medium, however, were not controlled. It was found that 1) acoustic background noise is negligible for sound frequencies above 100 kHz; 2 ) the noise level decreases as the coal concentration is increased; 3) sound attenuation in the Hygas slurry line at 200 kHz is about 2.5 dB/cm and 4 dB/cm for 18 percent and 33 percent coal concentration, respectively; and 4) acoustic techniques can be used to measure the mass flow of coal slurries in the frequency range of 100 kHz to 1 MHz, depending on pipe diameter and coal concentration. In this paper the results of an instrumentation feasibility test conducted under conditions of varying flow velocity and coal concentration are presented [ l ] . The feasibility test examined the noise background levels, the attenuation of sound and its relationshp to concentration, and the application of active cross correlation techniques to measure flow velocity. The flow velocity and coal concentration measurements can be used to determine the mass flow rate of the coal slurry. The results of the instrument feasibility test are summarized as follows: 1) an active cross correlation technique using an amplitude demodulation scheme is used to obtain the flow velocity with an accuracy of 3 percent of full scale; 2) sound attenuation is used to determine coal concentration; and 3) an on-line acoustic mass flowmeter can be designed to measure the coal slurry mass flow rate for coal concentrations above 1 wt%. A detailed discussion of the active cross-correlation flow measurement and an on-line acoustic mass flowmeter are presented in this paper. 11. DESCRIPTION OF EXPERIMENT A test section was designed, built, and installed in the low pressure line of the Hygas Pilot Plant. The test section is 5.08 cm in diameter and 182.82 cm (72 in) long with six transducer housings along its length. The distance between transducers is 0018-9537/81/0700-0248

Cavitation controlled acoustic probe for fabric spot cleaning and moisture monitoring

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Instrumentation for Fluid-Particle Flow: Electromagnetics

A method and apparatus are provided for monitoring a fabric. An acoustic probe generates acoustic waves relative to the fabric. An acoustic sensor, such as an accelerometer is coupled to the acoustic probe for generating a signal representative of cavitation activity in the fabric. The generated cavitation activity representative signal is processed to indicate moisture content of the fabric. A feature of the invention is a feedback control signal is generated responsive to the generated cavitation activity representative signal. The feedback control signal can be used to control the energy level of the generated acoustic waves and to control the application of a cleaning solution to the fabric.

Instrumentation for Fluid-Particle Flow: Acoustics

Publisher Summary This chapter reviews several instrumentations for measuring fluid-particle flow, focusing on electromagnetics. Electromagnetically based flow metering encompasses electrical, magnetic, and optical techniques. The chapter outlines the fundamental principle of each electromagnetic technique, with a focus on what each technique can measure. Electrical techniques primarily measure the electrical impedance of a mixed-phase medium. Optical or radiometric techniques for measuring solids concentration are based on the dependence of attenuation and scattering of an optical beam or radiation on the number of particles in the optical path. Magnetic flowmeter measures the induced electrical field strength when a conducting fluid flows through a magnetic field has been developed and applied to single-phase conducting flows, its application to the monitoring of solid/liquid flows is still infrequent..Electromagnetic flowmeters are mainly applied to single-phase conducting fluids, such as liquid metals, water-based industrial liquids, and blood. A brief description of the Coriolis flowmeter is also presented because it is widely used in industrial processes. A capacitive flowmeter, applicable only to slurries with nonconducting fluids, exhibits many attractive features that are often required by industrial processes.It is mentioned that the capacitive mass flowmeter can be a reliable instrument for measuring the flow of dilute suspended solids. It mentions the Pulsed Neutron Activation (PNA) Technique, which is an is an on-line tagging method.

Surface acoustic wave probe implant for predicting epileptic seizures

Publisher Summary This chapter describes several practical instrumentation for measuring fluid-particle flow. The chapter reviews the principles of acoustic measurement techniques and describes, in detail, acoustic flowmeters for solid/liquid and solid/gas pipe flows. The chapter also describe the use of ultrasound to monitor. Emphasis is given to the need for flow instruments in industrial processes. Because the environment of most industrial processes is adverse, flow instruments must meet several stringent requirements. Particularly, the instruments must be able to perform under high pressure and temperature while withstanding erosion, corrosion, and vibration. In addition, they must be rugged, low cost, and easy to operate. Electromagnetic flowmeters can be applied only to solid–liquid slurries that contain electrical conducting liquids. Coriolis flowmeters are used for solid-liquid flows, but their application is still limited because of their high cost and difficult installation requirements. Acoustic techniques applicable to solid suspensions are essentially based on measurements of three parameters—velocity, attenuation and scattering, and their dependence of these parameters on frequency (and angle of the scattering). Acoustic/ultrasonic techniques that have been developed into flow-monitoring instruments are Doppler, cross-correlation, and transit-time methods.. The chapter concludes by mentioning research needs for future sensors.