SU1242726A1 - Device for measuring temperature - Google Patents

Abstract

The invention relates to thermometry and can be used in systems for automatically controlling and regulating the gas flow temperature of a gas turbine engine. The aim of the invention is to improve the measurement accuracy by eliminating the error caused by the time delay of switching the tunable low-pass filter from one temperature mode of operation to another. The device is equipped with a second filter, a pressure sensor 9, a third differentiating amplifier, connected with each other and with other blocks. kami device in a certain way. 2 Il. with (From to Is :) ISD O)

Description

one.

The invention relates to thermometry and can be used to measure temperatures, for example, in systems for automatically controlling and regulating the temperature of a gas stream of a gas turbine engine (GTE).

The purpose of the invention is to improve the accuracy of temperature measurement by eliminating the error caused by the time delay of switching the tunable (| "low frequency from one temperature mode to another because the control signal of this filter is generated with a time delay due to the inertia of the filter.

FIG. 1 shows a functional diagram of the device; in fig. 2 shows an example implementation of a tunable low pass filter.

The device (Fig. 1) contains thermal converter 1 connected in series, amplifier 2, tunable low pass filter 3, first and second differentiating amplifiers 4 and 5, division blocks 6 and multiplication 7, adder 8, pressure sensor 9 in series, second filter 10, the third differentiating amplifier 1 1, the threshold circuit 12, the delay element 13 and the circuit 14, the output of the amplifier 2 being connected to the input of the tunable low-pass filter 3 and to the first input of the sum 8, the output of which is connected to the output of the device, and the second at od - with the output of the multiplier 7, the output of the first differentiating amplifier 4 is connected to a first input of multiplier blocks 7 and 6 divide.

During the operation of the CCD, there are two possible modes for changing the temperature of its gas flow: a mode of slow temperature change (for example, a steady state), when the rate of change of temperature T of the gas flow

dat dt

 ln n g, - 4 0.1-0.2} 2 - ms | ks

and a transitional regime, which is characterized by a rapid change in the temperature of the gas stream (e.g., re, -. acceleration or throttling pressure of the gas turbine engine), when

§C (0,, 2) () ,,,,. (2)

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The device works as follows

With a jump-like change in the temperature of the object being monitored, at the output of the temperature sensor, which is the first-order inertial element, after the time T has elapsed, the signal /

E, -1 Then + yT (1-е), (3) () where Е is the output signal of the thermal converter 1;

TO is the initial temperature value;

K. - coefficient of transfer of thermo- .5 converter;

dT is the temperature jump; TG is a time constant of the 1azovm termovatel. The voltage from the output of the amplifier 2 20 is fed to the first input of the adder 8

and the input of the tunable filter 3 / low frequency (PFNCH). The use of filter 3 in the device is caused by the presence of two modes of temperature variation. Interference suppression is more effective the higher the order of the filter used, i.e. the higher is the order of the polynomial in the expression for the transfer function of the 3: 0 function K (p) of filter 3, which can be represented as:

k (p) -5 + gP :: + p; s;

where N is the nominal transfer coefficient of the filter in the 5 band -.

start-up;

n is the order of the filter; p - complex variable; b1 | ...., the coefficient of a polynomial.

 O However, a high-order filter introduces a large delay (dynamic error) during fast-changing processes, which, in particular, adversely affects the quality of the process.

 S Tsesov regulate the temperature of the gas stream in the systems of automatic control of the CCD. Therefore . In the fast tempo change mode, the PFLS 3 is a filter.

50 low-order, making the shortest delay in the signal of the thermal sensor 1. In the mode of relatively slow temperature change, when the dynamic error caused by the delay 55 by the filter is small compared to the error caused by the interference, the TFEL 3 represents by itself (high-order filter. For

15

20

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effective suppression of PFNC 3 should meet the following requirements. With a rapid temperature change, its order must be minimal (first-second order) so that 5 does not introduce large phase and amplitude distortions into the useful signal, and with a slow change in temperature, third-fourth order, which increases the suppression efficiency of 10 interferences ( further filtering order 3 will result in significant distortion of the desired signal).

PFNC 3 consists (FIG. 2) of the first low-pass filter 15, the second low-pass filter 16 and the two-position switch 17.

Filters 15 and 16 low frequencies

can be made on the basis of operational amplifiers according to standard schemes and should be of the first or second order.

. The formation of the switching control signal of the PFNC 3 is carried out by a circuit consisting of the following elements: pressure sensor 9, second filter 10, third differentiating amplifier 11, threshold circuit 12, delay element 13, and H circuit. 14. Pressure and temperature in one section of the CCD change at the same time. At the same time, the time constant of the pressure sensor 9 is in the order of time the thermo sensor 1 constant. Moreover, unlike the latter, the time constant of the pressure sensor does not depend on the change

gas flow parameters.

Therefore, in the proposed device, the PFLS 3 control is performed not by a signal proportional to the rate of change of temperature, but by a signal proportional to speed. At

25

thirty.

35

40

pressure changes, i.e.

S

Perform measurement of a pressurizer press on a c mess PFN

hour long

giving

the first UQ schematics (1) for res time

half impu in si recl per pr prdlit cases behind the front force ad

45

This achieves an increase in the accuracy of temperature measurement, since the error existing at the control of the PFNS 3 is eliminated by a signal proportional to the rate of temperature change. This error is due to the time delay of switching PFNC 3 from one temperature to another due to the fact that the filter control signal 3 (proportional to the rate of change of temperature) is formed with a time delay due to the inertia of the filter-3. In the moment

five

0

50

the transition from the mode of slow temperature change to the mode of its quick change, the time delay of switching of the PFNC 3 leads to the introduction of additional dynamic error (delays in the last signal of the thermal sensor 1 to the differentiation channel), and at the moment of transition from the mode of fast temperature change to its slow changes - to a decrease in the quality of noise suppression by filter 3 (since the order of PFNC 3 is lower than that required for a given temperature mode).

The second filter 10 (low-pass filter of the standard structure) serves to suppress high-frequency noise present in the signal of the pressure sensor 9. Derivative Information

:. LR

time pressure --- (i.e., and

DT

25

0

five

0

five

0 5

the rate of change of temperature) from the output of the third differentiating amplifier 11 is fed to the input of the threshold circuit 12. If the signal value at the output of the third differential amplifier 11 is less than the UQ value of the trigger threshold of the threshold circuit 12, i.e. condition (1) is satisfied; then, at the output of the threshold circuit, a switching signal of the tunable low pass filter 3 to the high order filter state is generated. When the signal from the output of the third differential amplifier 11 threshold srabatshan U threshold scheme, i.e. when done-. The SRI of condition (2), at the output of the threshold circuit, a PFNC 3 switch signal is generated in the low-order filter state. The delay element and the circuit AND are used to eliminate the effect,. pulsed short-term noise in the signal of the pressure sensor when switching PFNC 3, i.e. PFNC 3 switching control is carried out in the proposed device by signals whose duration exceeds a certain amount (equal to the time delay of delay element 13. This increases the noise immunity of the forcing channel of the PFNC 3 switching control signal.

The signal from the output PFNCH 3 is fed to the input of the first differentiating amplifier 4.. The output signal of the differentiating amplifier A in block 9

division is divided by the output signal of the second differentiating amplifier 5; as a result, the output of block 6 generates a signal proportional to the time f of the thermostat 1, In multiplication unit 7, the signals from the output of division 6 and the first differentiating amplifier 4 are multiplied a) The tiring signal is fed to the second input of the summator 8 with the opposite positive sign. In this case, a signal is generated at the output of the adder 8, in which there is no dynamic error due to the inertia of the temperature sensor, t; e. the output signal of the device is proportional to the magnitude (To + LT).

Thermal converter 1, pressure sensor 9, differentiating amplifiers, 4, 5, and AND, adder 8, multiplication unit 7, and division block 6, the second filter 10 are standard blocks. The threshold circuit and the delay element can be performed by any schemes.

Claims (1)

Invention Formula A device for measuring: temperature, containing a thermal transducer in series and an amplifier whose output is connected . s 0 five 0 With the input of a tunable low-pass filter and the first input of the adder, the output of which is the output of the device, and the second input is connected to the output of the multiplication unit, the inputs of which are connected respectively to the output and the first input of the dividing unit; an amplifier whose input is connected to the output of a tunable low-pass filter, and the output is connected to the first input of the divider and connected via the second differential circuit to the second input of the delta block, the threshold circuit, o. in order to improve the measurement accuracy by eliminating the error caused by the time delay of switching the tunable low-pass filter from one temperature mode to another, sequentially connected sensors are inputted into it the second filter, the third differentiating amplifier, whose input is connected to the input of the threshold circuit, the delay element and the circuit AND whose output is connected to the control of the tunable low-pass filter input, the first input to the output of the elea: coagulant delay and the second delay vhod-- to the input element and the output of the threshold circuit. FIG. 2