RU137610U1 - DEVICE FOR MEASURING AIR CONSUMPTION IN THE COOLING CHANNEL OF A ROTATING TURBULAR SHOVEL - Google Patents

Abstract

1. A device for measuring air flow in the cooling channel of a rotating blade of a turbomachine, comprising a hot-wire anemometer with a sensitive element and a signal programming and processing unit, where the sensitive element is included in the bridge measuring circuit of the hot-wire anemometer, the input of the cooling channel is located in the shank of the blade, and the sensitive element is made in the form of a heated the current of the thread installed at the inlet to the blade cooling channel, and the blade cooling channel is made with outlet openings, characterized in that optionally contains at least one other current-heated thread of another blade, a primary data input unit, a current collector, signal amplifiers-converters, a switch, a rotational speed sensor and an indicator, where the current-heated threads are included in the bridge measuring circuit of the hot-wire anemometer through installation wires, a current collector , signal converters and a switch, moreover, a primary data input unit, a rotational speed sensor and a hot-wire anemometer are connected by installation wires to the programming unit and quipment signals, and the output unit of programming and signal processing connected to the input of the indicator, the input of cooling channels formed by the front ends of the shanks of the blades and the heated filament current installed at the entrances of the cooling channels radialno.2 blades. The device according to claim 1, characterized in that the current collector is installed along the axis of the rotor of the turbomachine. The device according to claim 1, characterized in that it is equipped with an additional circuit of the installation wires located similarly to the installation wires of the heated current

Description

The utility model relates to test equipment and can be used to measure air flow in the cooling systems of the blades of working turbomachines, such as gas turbine engines (GTE) and to determine malfunctions in the turbine cooling system.

One of the ways to improve the basic parameters of turbomachines is to increase the gas temperature in front of the turbine, therefore, when designing turbomachines, much attention is paid to the efficiency of the cooling system.

Malfunctions due to a decrease in air flow in the cooling system can arise due to clogging of the cooling channels of the blades by particles in the combustion products, an increase in the gaps in the labyrinth seals of the turbine, burnouts of the turbine blades, and other reasons.

To eliminate the occurrence of malfunctions, continuous or periodic monitoring of the air flow in the cooling system of the blades is required, both during their manufacture and during operation.

A known hot-wire gas flow meter (SU No. 135247, IPC G01F 1/68, 1960) using a wire heated by an electric current included in a bridge measuring circuit, and a vertical nozzle through which a controlled gas flow is expired. In the flowmeter, the wire is longer than the diameter of the nozzle and stretched horizontally at the exit of the nozzle, and the gas flow is directed upward. The flowmeter provides an extension of the range and reduces the measurement error. However, the flow meter does not allow measuring the gas flow rate under rotation conditions.

Known thermoanemometric mass air flow sensor (patent RU No. 16792, IPC G01P 5/12, 1999). The sensor contains a sensitive probe installed in the pipe, consisting of a ring, a thermistor, a V-shaped heated thread, each end of which is rigidly connected to the ring by means of conductive supports. The middle of the heated thread is suspended through a spring hook mounted in the ring by welding. The proposed sensor eliminates the instability of the output characteristic due to the shunting effect of the metal hook on the conductive thread, since the tension of the thread can change over time due to temperature factors, as well as due to the appearance of oxide films on the surface of the metal hook, which leads to a change in the shunt effect on the conductive heated a thread. However, the disadvantages of such sensors are the complexity of manufacturing and instability in the conditions of vibration and rotation.

The closest analogue of the claimed utility model in technical essence and purpose is a method and device for detecting failures in a turbine cooling system (patent EP 1580537, G01F 1/68, 2005-09-28). A device for detecting failures in a turbine cooling system comprises at least one wire-type sensing element that has a temperature-dependent characteristic. This characteristic is the dependence of the electrical resistance of the wire element or the voltage drop across it. To determine the temperature-dependent characteristics, a direct current is supplied from the power source to the sensor. The sensing element is fixed to a specific section of the blade cooling channel. This characteristic is determined using the programming and signal processing unit. The sensing element may be a resistor. In addition, the device contains a direct current source, voltmeter, ammeter and is considered as a sensor of air flow. The voltage drop across the sensing element or the resistance of this element is an indicator of air flow. The wire element is made of tantalum material or Invar alloy.

The technical solution provides failure detection in the turbine cooling system in static conditions. This technical solution cannot be used for rotating blades mounted simultaneously next to each other due to the large dimensions of the instrument part and the absence of a current collector.

The objectives of the proposed technical solution are:

- improving the reliability of cooling control of the working blades of turbomachines;

- expanding the measurement range and reducing the measurement error of the cooling parameters of the working blades of the turbomachine in the conditions of their rotation;

- measurement of the cooling parameters of several working blades in the conditions of their rotation;

- visibility of the display of the measured cooling parameters of several working blades in the conditions of their rotation.

The tasks are solved in that the device for measuring air flow in the cooling channel of a rotating blade of a turbomachine contains a hot-wire anemometer with a sensitive element and a unit for programming and processing signals. The sensitive element is included in the bridge measuring circuit of the hot-wire anemometer. The inlet of the cooling channel is located in the shank of the blade. The sensitive element is made in the form of a current-heated thread installed at the inlet to the cooling channel of the blade. The cooling channel of the blade is made with exhaust holes.

In accordance with the utility model, the device further comprises at least one current-heated thread of another blade, a primary data input unit, a current collector, signal converting amplifiers, a switch, a turbomachine rotor speed sensor and an indicator. Threads heated by current are included in the bridge measuring circuit of the hot-wire anemometer through installation wires, a current collector, signal converting amplifiers and a switch. The primary data input unit, speed sensor and hot-wire anemometer are connected by installation wires to the programming and signal processing unit. The output of the programming and signal processing unit is connected to the indicator input. The inputs of the cooling channels are made from the front ends of the shanks of the blades, and the current-heated threads are installed at the inputs to the cooling channels of the blades radially.

The essential features of the claimed technical solution allow to obtain the following technical results:

- the presence of at least one more current-heated filament of another blade, a primary data input unit, a current collector, a signal conversion amplifier, a turbomachine rotor speed sensor and an indicator provides an extension of the measurement range and a decrease in the measurement error of the cooling parameters of the working blades of the turbomachine;

- the inclusion of current-heated filaments in the circuit of the hot-wire anemometer through a current collector and an amplifier-converter of signals provides a temperature measurement of heated filaments depending on the speed of the air flow around them under the conditions of rotation of the working blades of the turbomachine;

- the inclusion of current-heated filaments in the circuit of the hot-wire anemometer through a switch allows you to separately connect current-heated threads to the hot-wire anemometer, which is due to the design of the hot-wire anemometer.

- connecting the input data input unit, the rotational speed sensor and the hot-wire anemometer with the installation wires to the programming and signal processing unit reduces the measurement errors of the blades cooling parameters;

- connection of the output of the programming and signal processing unit with the indicator input provides the display of the measured cooling parameters in a form convenient for perception;

- the implementation of the inputs of the cooling channels from the front ends of the shanks of the blades and the installation of them radially at the inlet of the current-heated filaments provides the same parameters of the air flow simultaneously for several measured working blades in conditions of their rotation.

The development and refinement of the set of essential features of a utility model for particular cases of its implementation is given below:

- installing a current collector along the axis of the rotor of the turbomachine provides current heating of the threads of the air flow measuring devices in the rotor blades of the turbomachine from the power source and transmitting to the indicator signals from the heated threads about the change in electrical resistance when the threads are blown with cooling air;

- supplying the device with an additional circuit of the installation wires located similarly to the installation wires of connecting the current-heated filament of one of the blades, where the additional circuit of the installation wires is connected to the programming and signal processing unit via the current collector, and the signal amplifier-converter provides accounting for changes in wire resistance depending on changes in the working cooling air flow temperature;

- the implementation of the programming and signal processing unit on the basis of a personal computer allows you to quickly change the signal processing algorithm;

- the use of an interface and input device of a personal computer as an input unit of primary data allows the use of a set of proven unified, hardware and software tools;

- the implementation of the indicator in the form of a set of digital indicator lamps provides a visual display of information in the form of luminous images of numbers or other symbols;

- the implementation of the indicator in the form of a printer provides automatic printing of the results of processing the measured cooling parameters of the working blades in the programming and information processing unit;

- the implementation of the indicator in the form of a personal computer monitor expands the possibilities of visual display of information;

- the implementation of a current-heated filament from tungsten allows a working temperature in the stream up to 730K. A tungsten filament operates in an atmosphere of hydrogen, a neutral gas, or in a vacuum;

- the implementation of a current-heated filament of platinum allows a working temperature in the stream up to 1000K. A platinum thread has stable electrical, thermoelectric and mechanical properties and high corrosion and thermal resistance.

It should be noted that the heating of filaments from tungsten or platinum is performed in the mode of maintaining a constant temperature of the filaments.

Thus, the tasks set in the utility model are solved.

- increased reliability of cooling control of the working blades of turbomachines;

- the measurement range has been expanded and the measurement errors of the cooling parameters of the working blades of the turbomachine in the conditions of their rotation have been reduced;

- measured the parameters of the cooling systems of several working blades in the conditions of their rotation;

- The measured cooling parameters of several working blades in the conditions of their rotation are clearly displayed.

The present utility model is illustrated by the following detailed description of a device for measuring air flow in a cooling channel of a rotating blade of a turbomachine and its operation with reference to the illustrations shown in FIG. 1-5, where:

in FIG. 1 is a schematic longitudinal section of a turbomachine;

in FIG. 2 - view A on the front end of the shank of the scapula;

in FIG. 3 - electrical diagram of the hot-wire anemometer:

in FIG. 4 - dependence of the Reynolds criterion (Re) on the Nusselt criterion (Nu);

in FIG. 5 is a structural diagram of a device for measuring air flow.

A device for measuring air flow in the cooling channel 1 of a rotating blade 2 of a turbomachine contains (see Fig. 1-5) a hot-wire anemometer 3 with a sensing element 4 and a signal programming and processing unit 5. The sensitive element 4 is included in the bridge measuring circuit 6 of the hot-wire anemometer 3.

The input of the cooling channel 1 is located in the shank of the blade 2. The sensitive element 4 is made in the form of a current-heated thread installed at the inlet in the cooling channel 1 of the blade 2. The cooling channel 1 of the blade 2 is made with exhaust holes. The device further comprises at least one current-heated thread 7 of another blade 2, a primary data input unit 8, a current collector 9, signal amplifiers-converters 10, 11, a turbomachine rotor speed sensor 12 and an indicator 13. Threads 4 or heated by current 7 are included in the electrical circuit of the anemometer 3 through the installation wires 14 or 15, respectively, the current collector 9, respectively, signal converters 10 or 11 and the switch 16. The primary data input unit 8 and the rotation speed sensor 12 are connected respectively installation wires 17 and 18 to the unit 5 for programming and signal processing. The output of the programming and signal processing unit 5 is connected to the input of the indicator 13. In this case, the input of the cooling channels 1 is made from the front ends of the shanks of the blades 2. The current-heated threads 4 or 7 are installed radially at the entrance to the cooling channels 1 of the blades 2 (see Fig. 2 ) The current collector 9 is installed along the axis of the rotor of the turbomachine.

The device is equipped with an additional circuit of the installation wires 19 located similarly to the installation wire 14, 15 for connecting current-heated threads of 4 or 7 blades 2. An additional circuit of the installation wires 19 is connected to the programming and signal processing unit 5 through a current collector 9, an amplifier-converter 20 of the signals, and an installation wire 21 An additional circuit of the installation wires 19 is designed to determine changes in the electrical resistance of the installation wires 14, 15 in a wide range of operating temperatures tour. The indicator 13 can be made in the form of a set of digital indicator lamps, a printer or a personal computer monitor. Filament 4 or 7 heated by current can be made of tungsten or platinum with a diameter of about 10 microns and a length of 3.5-4 mm, depending on the temperature regime and the conditions of their operation.

The principle of operation of the hot-wire anemometer 3 is based on the dependence of the current flowing through the heated filaments 4 or 7 on the speed of the air flowing around them in the cooling channels 1 of the blades 2. A functional diagram of a hot-wire anemometer 3 with strands 4, 7 heated to a constant temperature is given in FIG. 3. Filaments 4 or 7 heated from a direct current source are connected to one of the arms of the resistance measuring bridge 6.

The hot-wire anemometer 3, in addition to the current-heated threads 4 or 7 and the resistance measuring bridge 6, includes a unit 22 for automatically controlling the temperature of the heated threads 4 or 7. The current-heated threads 4 or 7 and the automatic temperature control unit 22 are electrically connected (see Fig. 3) between themselves into an electric circuit in a hot-wire anemometer 3. The hot-air anemometer 3 is connected to the programming and signal processing unit 5 by an installation wire 23.

To determine the flow rate of cooling air, calibrations of current-heated filaments 4 or 7 are carried out as part of a hot-wire anemometer 3, working together with working blades 2 in static conditions (without rotation).

The calculation results showed that the influence of centrifugal forces arising from the rotation of the blades 2 on the heat transfer of the heated threads 4, 7 can be neglected.

As a result, calibration results under static conditions (see Fig. 4) can be used to determine the flow of cooling air through the working blades under conditions of their rotation.

High measurement accuracy is ensured by using the algorithm in block 5 for programming and signal processing that consists in calculating the dependence of the heat transfer coefficient of threads 4 or 7 on the flow rate of cooling air:

; критерий Рейнольдса -

;where is the Nusselt criterion -

; Reynolds criterion -

;

A, B - coefficients determined experimentally;

α is the heat transfer coefficient;

λ is the coefficient of thermal conductivity;

ρ is the flux density;

u is the flow rate;

d is the diameter of the filament heated by current;

µ is the coefficient of viscosity of air.

The heat transfer coefficient is determined from the conditions of the heat balance:

where α is the heat transfer coefficient;

;

;

I is the strength of the current flowing in the wire of the "sensor";

R is the resistance of the heated thread;

ΔT is the difference between the temperature of the heated thread T _p and the temperature of the inhibited air flow T _about ;

l, d are the length and diameter of the filament heated by current, respectively. The temperature difference is calculated through the resistance of the heated filament according to the formula:

where R _o is the resistance of the current-heated filament at a drag temperature;

R _n - resistance of the current-heated filament during overheating (overheating by 50%);

a is a coefficient depending on the material heated by the current of the filament, for tungsten a = 3.5 · 10 ^-3 .

The calibration results of the current-heated air flow threads (see Fig. 4) are consistent with the generalized dependence

constructed at various blowing speeds of a filament heated by current and at a flow velocity u = 0

In experiments, to exclude the effect of a temperature change in the resistance of the supply chain on the resistance of the current-heated filament, the latter was calculated by the difference in the resistances of the main circuit (installation wires 14, 15 with current-heated filaments 4.7) and the additional circuit (installation wire 19 laid next to the wires 14, 15 ) not having a current-heated filament. The resistance value R _{o of the} heated filaments 4 or 7 and the current strength can be used to calculate the voltage, which makes it possible to determine the value of the Nusselt number (Nu). Then, using the calibration dependence (Fig. 4), determine the value of the Re number and then the air flow rate by the ratio:

where Re _n is the Reynolds number;

g - acceleration of gravity:

µ is the coefficient of viscosity of air;

F _k - the area of the holes in the receiving part of the scapula;

d _n - the diameter of the heated current thread.

Before testing, the calculation and display parameters are entered into the programming and signal processing unit 5 using the primary data input unit 8. The calculation parameters, for example, include the numbers of the blades on which the heated threads are installed. We also introduce an algorithm for calculating formulas (a, b, c, d, e) and the dependence of the Re criterion on the Nu criterion (see Fig. 4) for each blade 2 with a current-heated filament 4 or 7, as well as calculation constants and parameters indication. Display parameters include, for example, the display mode of information on the indicator.

As amplifiers-converters 10, 11, 20 can be used, for example, amplifiers 2210A manufacturer VISHAY. Block 5 programming and signal processing can be performed, for example, on the basis of a personal computer. As block 8 input primary data can be used, for example, the interface and input devices of a personal computer.

The device operates as follows (see Fig. 1-5). As the heat transfer between the filaments 4 or 7 and the air flow in the channel 1 of each measured blade 2 changes, the electrical resistance of the filaments 4 or 7 changes. The heated filament 4 or 7 is turned on by the switch 16. An unbalance voltage appears on the measuring diagonal of the resistance bridge 6, which is fed to the input control unit 22. From the output of unit 22, the current in the feedback circuit 24 is supplied to the supply diagonal of the bridge 6. This aligns the imbalance in the circuit of the bridge 6.

Any changes in the temperature of filaments 4 or 7 heated by the current due to heat transfer to the air stream are compensated by the energy of the electric current flowing in the filaments, which is recorded by a hot-wire anemometer 3. Air flow measurement is provided (see Fig. 4) by preliminary calibration of the heated filaments 4 or 7 under stationary conditions in the complex with working blades 2 in which these threads are installed.

The presence of threads heated by current 4 or 7 on several blades 2 allows you to measure the flow of cooling air in these blades separately through switch 16.

During the tests, the signals of the values of the flow rate of the cooled air heated by the current of the threads in the blades, the rotational speed of the rotor of the test product and through the current collector 9, amplifiers-converters 10, 11, switch 16 and the hot-wire anemometer 3 are recorded, these signals are transmitted to the processing and programming unit 5 signals.

Signal processing is performed using primary data, an algorithm (formulas a, b, c, d, e). The results of signal processing are displayed on indicator 13.

Thus, the measuring device is a visual tool for obtaining a picture of the distribution of air flow over the rotating blades of a turbomachine, for example a gas turbine engine. This provides the necessary information for the refinement of the exploited and designed promising cooling systems for rotor blades of turbomachines.

Claims (10)

1. A device for measuring air flow in the cooling channel of a rotating blade of a turbomachine, comprising a hot-wire anemometer with a sensitive element and a signal programming and processing unit, where the sensitive element is included in the bridge measuring circuit of the hot-wire anemometer, the input of the cooling channel is located in the shank of the blade, and the sensitive element is made in the form of a heated the current of the thread installed at the inlet to the blade cooling channel, and the blade cooling channel is made with outlet openings, characterized in that optionally contains at least one other current-heated thread of another blade, a primary data input unit, a current collector, signal amplifiers-converters, a switch, a rotational speed sensor and an indicator, where the current-heated threads are included in the bridge measuring circuit of the hot-wire anemometer through installation wires, a current collector , signal converters and a switch, moreover, a primary data input unit, a rotational speed sensor and a hot-wire anemometer are connected by installation wires to the programming unit and quipment signals, and the output unit of programming and signal processing connected to the input of the indicator, the input of cooling channels formed by the front ends of the shanks of the blades and the heated filament current installed at the entrances of the cooling channels radially blades. 2. The device according to claim 1, characterized in that the current collector is installed along the axis of the rotor of the turbomachine. 3. The device according to claim 1, characterized in that it is equipped with an additional circuit of the installation wires located similarly to the installation wires of the current-heated thread of one of the blades, the additional circuit of the installation wires connected to the programming and signal processing unit through a current collector and an amplifier-signal converter. 4. The device according to claim 1, characterized in that the programming and signal processing unit is based on a personal computer. 5. The device according to claim 1, characterized in that, for example, an interface and input devices of a personal computer are used as a primary data input unit. 6. The device according to claim 1, characterized in that the indicator is made in the form of a set of digital indicator lamps. 7. The device according to claim 1, characterized in that the indicator is made in the form of a printer. 8. The device according to claim 1, characterized in that the indicator is made in the form of a personal computer monitor. 9. The device according to claim 1, characterized in that the current-heated thread is made of tungsten. 10. The device according to claim 1, characterized in that the current-heated thread is made of platinum.

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