SU1171671A1 - Jet-acoustic temperature-sensitive element - Google Patents

Abstract

SPRAY-ACOUSTIC TEMPERATURE SENSOR containing an input tapering nozzle with a profiled nozzle, a cylindrical resonator located opposite the input tapering nozzle, and a pressure pulsation transducer placed in a chamber with outlet openings, characterized in that in order to expand the range of measured temperatures. equipped with a length-adjustable cylindrical nozzle coaxial with the inlet nozzle and a cylindrical resonator, with the pressure pulsation converter mounted at the blind end of the of cylindrical nozzle and outlets formed on the side wall of the chamber. (L O5

Description

The invention relates to the field of thermometers and can be used to measure the temperature of gas streams.

The aim of the invention is to expand the range of measured temperatures.

FIG. 1 shows the flow diagram of the proposed sensor; in fig. 2 shows section A-A in FIG. one; in fig. 3 - dependence of the relative amplitude of the output signal on the relative diameter of the chamber - the chimney; in fig. 4 - flow part; in fig. 5 shows the dependence of the output signal of the sensor — the relative frequency — for the two forms of the output channel on the ratio of pressures on the device as a whole.

The device contains a tapering nozzle 1 with a profiled nozzle, a cylindrical resonator 2 placed in chamber 3 with an output tapering-expansion port with channel 4 and a pressure pulsation converter 5.

The device works as follows.

By creating the minimum pressure ratio required for the operation of the sensor, Pi Pi / Pj on the output channel 4, a close to critical pressure ratio G1b) g Pg / Pj is established. Due to the fact that the area of the minimum cross section of the output channel 4 exceeds the cut-off area of the nozzle 1, a supersonic outflow of an underexpanded gas jet with characteristic "barrel-shaped shock wave structures" occurs at the exit of the nozzle. Due to the interaction of the gas jet with the resonator 2, high-frequency pressure oscillations occur, which propagate from the interaction zone along chamber 3 and are sensed by the pressure pulse converter 5. In a transducer, usually of the piezoelectric type, pressure pulsations are converted into electrical pulses, the frequency of which is associated with the temperature of deceleration of the gas jet by the ratio f

The location of the pressure pulsation transducer at the blind end of a large elongation chamber (d // l 10) makes it possible, in the measurement of high temperatures, to take it to a zone of low temperature and to maintain the efficiency of the sensor.

On the other hand, it is known that when transmitting an acoustic signal through the sound duct, its amplitude decreases with increasing relative length of the sound duct 1 / d. The experiments performed to determine the attenuation of the amplitude of the signal of the jet acoustic sensor are shown in FIG. 3. As these studies have shown, when the ratio of the chamber length to its diameter is 10: 1, the relative drop in amplitude is less than 10%, and at 1 / d 100: 1, the amplitude decreases by a factor of 2.5. Since in this case the absolute values of the signal amplitude reach a level of 200 mv and the acceptable value of the input signal for stable operation of the secondary equipment lOmv 15 (A 0.05– 0.075), the maximum elongation of the camera - sound duct should be limited (see Fig. 2).

The location of the chamber outlet, playing its role as a stabilizer of the pressure ratio at the nozzle, in the side wall of the chamber does not create obstacles in the transmission of an acoustic signal through the sound conduit chamber from the generation zone to the pressure pulsation transducer. Performing the outlet in the form of a narrowing expansion channel reduces the total pressure loss during gas flow and increases the efficiency of the device as a whole.

The model of the axially symmetric jet-acoustic temperature sensor, the flow part of which is shown in FIG. 4. The sensor operates at frequencies from 2 to 8 kHz depending on the length of the resonator L with the amplitude of the signal from the converter placed at the end of the camera sound line 1000 mm long with an internal diameter of 10 mm (extension l / d 100) from 150 mv at f 3 kHz to 30mv at f 6 kHz. The dependences of the relative frequency of the output signal on the pressure ratio for the two types of output channel (Fig. 5) show that the minimum required pressure-ratio ratio to achieve a sensor frequency error of less than 1%, respectively, equal to a narrowing-broadening channel, 0, for output holes, 0.

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Claims (1)

ACRYNIC-ACOUSTIC TEMPERATURE SENSOR, comprising an inlet narrowing nozzle with a profiled nozzle, a cylindrical resonator located opposite the inlet narrowing nozzle, and a pressure pulsation transducer located in the chamber with outlet openings, characterized in that, in order to expand the range of measured temperatures, the chamber is equipped with an adjustable along the length of the cylindrical nozzle, coaxial with the inlet nozzle and the cylindrical resonator, while the pressure pulsation transducer is installed on the blind end of the cylinder a natural nozzle, and the outlet openings are made on the side wall of the chamber. Figure 1