RU143783U1 - DEVICE FOR MEASURING PULSING FLOW PARAMETERS - Google Patents

Abstract

A device for measuring pulsating flow parameters, comprising nozzles, a block for digital conversion and registration of analog signals, comprising a unit for setting the sampling frequency of the conversion of incoming analog signals, pressure pulsation sensors located in the nozzle, characterized in that the nozzles are fixedly mounted relative to the flow, determining the pulsations of the three components of the flow velocity and contains a receiving device made in the form of a hemisphere with a given radius, There are receiving holes connected to at least three pressure pulsation sensors in the hemisphere, and the distance between the receiving holes is less than one third of the hemisphere radius, the unit for digital conversion and registration of analog signals additionally contains a unit for accounting calibration curves, an algorithm block for a mathematical model for determining gas-dynamic functions and approximating coefficients , a unit for determining the three components of the flow rate and visualization of the processing results, an indication unit for three components t flow rate, angle of attack and sliding compression ratio and the total pressure loss.

Description

The utility model relates to aviation technology and can be used to diagnose the technical condition of gas turbine engines, to study the flow in pipelines and channels with a flow separation.

The utility model is designed to determine the dynamics of changes in the gas-dynamic parameters of the flow in blade machines and channels, for example, in blade compressors, pipelines and diffusers in predetermined flow areas, both in the boundary zones and in the core of the gas flow.

Known devices for determining the averaged (stationary) magnitude of the reduced flow velocity in a section perpendicular to the direction of flow, measuring in one section the total and static pressure using probes or nozzles installed in the bore of the pipeline, recording the measurements and processing the measurement results (C .M. Gorlin, Experimental Aeromechanics, Moscow: Higher School 1970, pp. 173-178).

The disadvantage of these devices is the low accuracy of the measurements and the lack of completeness of information to determine the structure of the stream.

These measurements are not enough to observe the change in the flow structure and the velocity vector components over time, since these devices do not provide the necessary information about the instantaneous values of the absolute flow velocity and its three components: axial velocity, radial velocity, and peripheral velocity and their directions.

The Kulite receiver device (Kulite Semiconductor Products, Inc.) known as the “Ultra-miniature Piezoresistive Sensor” is known, which is described in (Alexander A. Ned, Dr. Tonghuo Shang, Scott Goodman, Adam Hurst, Dr. John Chivers // Fully integrated miniature, high frequency flow probe utilizing leadless, soi technology suitable for gas turbines // http://www.a-tech.ca/doc_series/FAP-250_ATI.pdf). The device allows you to determine flow angles, uses five high-temperature miniature absolute pressure sensors located in a spherical head. At the same time, the non-uniformity of the spherical surface of the sensor can lead to unstable measurement results.

The main disadvantages of this device are: the fragility (fragility) of the design of the receiving element, the insecurity of the sensors from ingress of solid particles, the use of absolute pressure sensors, the location of the central sensor in the direction of flow, and as a result, the measurement of lateral pressure by four others - on the inhomogeneous spherical surface of the sensor - almost conical surface , where perturbations caused by the appearance of vortex structures on its surface can occur.

The disadvantages include the similar proximity of the head to the holder and, as a consequence, the occurrence of disturbances from the holder.

Closest to the claimed technical solution is a device for determining pulsations of the flow rate (RU 2285244, G01P 5/14, 2006). The device contains nozzles, a receiver position correction block, a nozzle consisting of a flow angle determiner and a correction device, a digital conversion and registration unit for analog signals, which includes a unit for setting the sampling frequency of the conversion of incoming analog signals, a unit for converting electrical quantities into physical ones, a unit for monitoring converted analog signals, block for the duration of conversion of analog signals, block for recording analog signals, block synchronization a alogovyh signals, and a determination unit given flow rate and processing imaging results. The nozzle receiver is equipped with pulsation sensors for full and static pressure and a flow direction detector. One sensor is installed in the nozzle parallel to the direction of flow and provides measurement of pulsations of static pressure, and the other sensor is perpendicular to the direction of flow and provides measurement of pulsations of total pressure, while the sensors are located in the receiver of the nozzle at one given point and do not have attached volumes. The nozzles are connected to the unit for correcting the position of the receiver of the nozzle relative to the flow direction and to the unit for digital conversion and registration of analog signals that are interconnected, and the unit for digital conversion and registration of analog signals is connected to the unit for determining the reduced flow rate and visualization of the processing results.

The use of the device described above showed that in real conditions the flow velocity at the field point is a variable, largely due to the turbulence of the flow, the propagation of disturbances from structural elements, the viscosity of the medium and other processes.

The experiments conducted to determine the structure of the gas flow in the compressor and to change the gas-dynamic parameters of the flow with time during continuous, synchronous measurement of the total and static pressure in the direction-changing incident non-stationary flow (with the construction of isolines of the total and static pressures and the reduced flow velocity in absolute motion, increase isolines and / or loss of total pressure, by determining the reduced flow rate, and the gas-dynamic parameters of the flow in a wide frequency range, which which, under conditions of changing the compressor operating mode, is from 5 to 10,000 Hz or more) showed that the flow structure and, accordingly, the instantaneous values of the parameters in the compressor change depending on the location of the interscapular channels and blades of their generators near the measuring device. Two pressure sensors are not enough to identify the three velocity components.

The utility model is based on the following tasks:

- determination of the three components of the velocity of the pulsating flow: U - axial speed, V - radial speed, W - peripheral speed;

- simultaneous determination of the three components of speed, static and total pressure of the pulsating flow;

- determination of the static and total pressure of the pulsating flow in a wide range of flow angles (up to ± 85 °).

The tasks are solved in that the device for measuring the parameters of the pulsating flow contains nozzles, a unit for digital conversion and registration of analog signals, containing a unit for setting the sampling frequency of the conversion of incoming analog signals, while pressure pulsation sensors are located in the nozzle.

What is new in the utility model is that the nozzles are fixedly mounted relative to the flow, made with the possibility of determining the pulsations of the three components of the flow velocity, and contains a receiving device made in the form of a hemisphere with a given radius. On the surface of the hemisphere are receiving openings connected to at least three pressure pulsation sensors. The distance between the receiving holes is less than one third of the hemisphere radius. The block for digital conversion and registration of analog signals additionally contains a unit for accounting calibration curves, a block for the mathematical model algorithm for determining gas-dynamic functions and approximating coefficients, a unit for determining three components of the flow velocity and visualization of processing results, an indication unit for three components of the flow velocity, angle of attack and slip, and compression ratio and total pressure loss.

In this application, the goal is to create a nozzle - a meter of three components of the velocity of the pulsating flow when using high-frequency small-sized pressure pulsation sensors as sensitive elements. The nozzles are designed for the simultaneous measurement of three velocity components (U, V, W), static (P) and total pressure (P ^∗ ) of the flow in a wide frequency range, for example, 100 kHz in the range of average values of the flow velocity λ = 0.01-0.8.

To obtain the values of the three velocity components (U, V, W) and the pressures P, P ^{∗, the} minimum number of sensors is three; however, to increase the accuracy, it is necessary to use a larger number of sensors — four or more.

In order to achieve the task, low-inertia pressure pulsation sensors were used as sensitive elements. Purging an existing nozzle for measuring the pulsations of the axial flow velocity in the wind tunnel showed that when using inertial pressure pulsation sensors as sensitive elements, it is possible to obtain a pulsating flow velocity meter with an accuracy of 0.7-3% in the constant component in the range of the bevel from 0 to 15-20 °. The difference between the speed determined by the constant component of the pulsations of the total and static pressures and the flow rate obtained by averaging all the data over a long period of time from the speed values obtained using the inertial reference nozzle is not more than 2%. The accuracy of determining the velocity pulsations is 1.1% at a zero bevel and 1.6% -1.2% at a bevel in the range of ± 20 °. The use of high-frequency sensors and the small size of the receiving device in the form of a hemisphere due to synchronous measurement and registration allow you to get instantaneous pressure values. Reducing the size of the sensors reduces the distance between the receiving holes in the hemisphere, which allows you to expand the frequency range. In addition, an increase in the number of sensors makes it possible to expand the range of determining the flow velocity and the range of angles of attack (α) and slip (φ) due to the placement of a larger number of holes on the surface of the hemisphere. In this case, the hemisphere surface size is 08 mm, due to the location of four small sensors in it, having the shape of cylinders with ⌀1.6 mm. In this case, a registrar having a sampling frequency of 200 kHz during synchronous registration can be used as a registrar.

In connection with the foregoing, it is assumed possible, to achieve the objectives, the use of low-inertia pressure pulsation sensors as sensitive elements in the nozzle to determine the three components of the velocity of the pulsating flow, static and total pressure of the pulsating flow in a wide range of flow angles.

The present utility model is illustrated by the following detailed description of the design of a device for measuring pulsating flow parameters and a description of its operation with reference to FIG. 1-4, where:

in FIG. 1 shows a nozzle layout with the placement of four pressure pulsation sensors;

in FIG. 2 shows a nozzle diagram showing the incident flow with Mach number (M), angle of attack (α) and slip (φ), certain pressure values P ₁ , P ₂ , P ₃ , P ₄ in the nozzle receiving holes;

in FIG. 3 shows a block diagram of the operation of a hardware unit for converting signals from pressure pulsation sensors to the values of the three components of the velocity (U, V, W) of the pulsating flow, static pressure (P) and total pressure (P ^∗ ) of the flow in a wide frequency range;

in FIG. 4 in the form of a graph shows the type of calibration curves for the proposed device.

A device for measuring the parameters of a pulsating flow contains nozzles 1 (see Fig. 1). The nozzles 1 are mounted motionless with respect to the flow, configured to determine the three components of the velocity of the pulsating flow and contains a receiving device 2 made in the form of a hemisphere with a given radius (⌀8 mm). On the surface of the hemisphere there are receiving holes 3 connected to four pressure pulsation sensors 4, 5, 6, 7, and the distance between the receiving holes 3 is less than one third of the radius of the hemisphere.

The incident flow with the Mach number (M) (see Fig. 2), the angle of attack (α) and slip (φ) creates certain pressure values P ₁ , P ₂ , P ₃ , P ₄ in the receiving holes 3 of the nozzle 1.

According to the block diagram shown in FIG. 3, the analog signals from sensors 4, 5, 6, 7 of the pressure pulsation are received in block 8 for digital conversion and registration of analog signals. Block 8 contains:

- block 9 sets the sampling frequency of the conversion of incoming analog signals;

- block 10 synchronization of readings of sensors 4, 5, 6, 7;

- block 11 accounting calibration curves;

- block 12 of the mathematical model algorithm for determining gas-dynamic functions and approximating coefficients;

- block 13 determining the angle of attack (α), the angle of slip (φ);

- block 14 determining the pressure coefficient π _λ ;

- block 15 determining the three components of the flow rate and visualizing the processing results;

- a block 16 for indicating three components of the flow velocity, angle of attack and slip, compression ratio and total pressure loss.

All blocks are interconnected by feedbacks to improve the accuracy of determining the velocity components and pressure values.

Block 8 of the digital conversion and registration of analog signals contains a block 11 for accounting for individual calibrations of sensors 4, 5, 6, 7 of pressure pulsations, as well as a block for determining the Mach number of the incoming flow (not shown), block 13 for determining the angle of attack (α), sliding angle (φ) and the pressure coefficient determination unit (π _λ ) 14 using the approximating coefficients a _ijk , b _ijk and the coefficients C _α , C _φ , C _M determined from the measured pressures P ₁ , P ₂ , P ₃ , P ₄ .

An example of a mathematical model based on approximation by a three-dimensional second-order polynomial of the main flow parameters is presented below:

;

;

;

;

Block 8 of the digital conversion and registration of analog signals contains a unit for visualization of the converted analog signals, registration of the converted analog signals and a block for synchronizing analog signals (not shown).

Blocks are a set of programs with which the collection, digital conversion and registration of analog data coming from sensors 4, 5, 6, 7 to a computer for their subsequent processing is carried out.

Below is an exemplary form of formulas for determining the coefficients C _α , C _φ , C _M and the gas-dynamic function πλ:

C _α = (P ₂ -P ₁ ) / (P ₂ - (P ₁ + P ₃ + P ₄ ) / 3);

C _φ = (P ₃ -P ₄ ) / (P ₂ - (P ₁ + P ₃ + P ₄ ) / 3);

C _M = (P ₂ - (P ₁ + P ₃ + P ₄ ) / 3) / P ₂ ;

π _λ = (P ₁ + P ₃ + P ₄ ) / 3 / P ^∗ = (P ₁ + P ₃ + P ₄ ) / 3 / P · (1- (k + 1) / (k-1) · λ ² ) ^{k / (k-1)} .

The operation of the device.

The pressure with the help of sensors 4, 5, 6, 7 is converted into electrical pulses, which are recorded using a digital recorder and converted to pressure, after which they are compared with the nozzle 1 calibrations, which determine the deviation of the receiving device angle 2, nozzle 1 from the flow direction angle . The digital recorder simultaneously converts the readings of sensors 4, 5, 6, 7 into analog data from all sensors 4, 5, 6, 7 and records the converted analog signals. The visualized unit of the converted analog signals (not shown) produces a visualization of the recorded values. The digital files received in block 8 for digital conversion and registration of analog signals are sent to block 15 for determining the three components of the flow rate and visualizing the processing results. Block 15 is a complex of programs, including a program for determining the reduced flow velocity λ = f (t), a program for graphical images in the form of oscillograms, and a program for constructing lines λ = Const of the reduced flow velocity that visualize the flow structure.

As a base nozzle for measuring non-stationary parameters , , P ^∗ and P in a three-dimensional flow, nozzles are used, designed to measure similar stationary and non-stationary parameters, with which you can measure the above stationary parameters, using to determine the flow angle and angle calibration curves and, using calibrations, determine the ratio of the true and measured pressures P ^∗ and static pressure P from the angle values. Calibration curves are determined by preliminary purges and a collection and processing system, the algorithm of which is shown in the graph in FIG. 4, where the graph shows the type of calibration curves for the proposed device, obtained in one of the flow rates in a special wind tunnel.

A device for measuring the parameters of a pulsating flow allows you to determine the flow structure (using preliminary calibration curves) without correcting the position of the receiving device 2 and the measuring elements (sensors).

The technical solution provides the determination of not only one longitudinal velocity component, but all three: U - axial, V - radial, W - circumferential. To determine the three components of the velocity of the pulsating flow, this device does not require rotation of the nozzle head. The device provides a wide range of flow angles. The design of the device is technologically simple and affordable, thanks to the use of standard purchased sensors.

Claims (1)

A device for measuring pulsating flow parameters, comprising nozzles, a block for digital conversion and registration of analog signals, comprising a unit for setting the sampling frequency of the conversion of incoming analog signals, pressure pulsation sensors located in the nozzle, characterized in that the nozzles are fixedly mounted relative to the flow, determining the pulsations of the three components of the flow velocity and contains a receiving device made in the form of a hemisphere with a given radius, There are receiving holes connected to at least three pressure pulsation sensors in the hemisphere, and the distance between the receiving holes is less than one third of the hemisphere radius, the unit for digital conversion and registration of analog signals additionally contains a unit for accounting calibration curves, an algorithm block for a mathematical model for determining gas-dynamic functions and approximating coefficients , a unit for determining three components of the flow rate and visualization of the processing results, an indication unit for three t flow rate, angle of attack and sliding compression ratio and the total pressure loss.