RU2562361C1 - Cooling method of turbine work blade of gas-turbine engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: cooling method of turbine work blade of gas-turbine engine includes exhaust of the cooling air from the air cavity of the combustion chamber, its transportation to the swirling assembly, made on the stator against the turbine disk, and further cooling air supply from the swirling assembly to the rotating channel of each work blade. Via the nozzles of the ring swirling assembly located along the circle tangentially with rotation in the direction of the turbine rotation and coaxially with input to the smooth channel of each blade the intermittent supply of the cooling air is ensured. As result of the periodic movement of the impact waves from the nozzles of the swirling assembly in each blade channel the forced oscillation of the cooling air are excited with frequency of the first resonant harmonics. The cooling air oscillations are created with frequency determined by the resonance conditions, air speed and wave length as per the set ratios, intensifying the heat exchange in channel between the blade and the cooling air.

EFFECT: invention increases engine economical efficiency upon keeping the reliability and increasing the engine service life.

2 cl, 10 dwg

Description

The invention relates to methods for intensifying heat transfer in heat exchangers used in various industries, for example, high-temperature rotary machines. It is on aircraft engines, where the maximum engine operating mode for power is short-term, and cruising long-term modes require intensive cooling of the turbine blades.

A known turbine turbine cooling system (RF Patent 2159335, MKI F01D 25/12, publ. 2000) containing a sequentially mounted manifold with controlled valves at the outlet, communicated by its inlet with the air cavity of the combustion chamber, a multi-channel duct passing through the internal cavity of the nozzle blades , spin nozzle apparatus and impeller cooling channels.

In this design, the elements of the turbine are cooled by air taken after the last stage of the compressor, which has a very high temperature level in the gas-air path of the engine. This air is supplied to cool the blades through the impeller disk in its middle and peripheral zones. On the other hand, the heat supply to the disk comes from the gas-air path of the turbine through the working blades and their locking part. The high temperature of the impeller elements leads to significant temperature expansions of the impellers, as a result of which the radial clearance between the stator and the impeller decreases and the efficiency increases turbines. However, the high temperature of the cooling air leads to an increase in the temperature of the peripheral and middle zones with a relatively "cold" disk hub. Such an uneven temperature in the disk leads to a high level of stresses in it, which reduces the engine resource at maximum speeds.

A known method of intensifying heat transfer by communicating the flow of coolant in the heat transfer channel of forced vibrations by applying periodic disturbing pulses (USSR Author's Certificate 1368612, MKI F28F 13/10, publ. 1988). Here, an autonomous electric motor is used to drive the pulsator. The disadvantage of this design is the presence of a bulky source of oscillations for only one stationary channel of the coolant.

The closest analogue to the same purpose as the claimed technical solution is a method of cooling the working blades of a turbine of a double-circuit gas turbine engine and a device for its implementation (RF Patent 2387846, IPC F01D 5/18, publ. 2006).

In accordance with the technical solution of the prototype, the method of cooling the working blades of a turbine of a double-circuit gas turbine engine includes the selection of cooling air from the air cavity of the combustion chamber, its transportation to the swirling apparatus and the subsequent supply of cooling air from the swirling apparatus to the channel of the working blades.

The prototype increases the efficiency of a gas turbine engine with a high temperature turbine by optimizing the flow of cooling air in the working blades of the high pressure turbine while maintaining the reliability and service life of the engine. However, this technical solution does not fully utilize the possibilities of intensifying heat transfer between cooling air in the channel and the working blade.

The invention is based on the solution of the problems of increasing the efficiency of gas turbine engines with high-temperature turbines by intensifying heat transfer by communicating forced vibrations to the flow of cooling air in the heat exchange channel of each working blade of the turbine by applying periodic disturbing pulses while maintaining reliability and increasing engine life.

The tasks are solved in that the method of cooling the working blade of a turbine of a gas turbine engine includes the selection of cooling air from the air cavity of the combustion chamber, its transportation to a swirling apparatus made on a stator opposite the turbine’s disk, and then supplying cooling air from the swirling apparatus to the rotating channel of each working blades.

, скоростью звука

и длиной волны

, определяемой соотношением

,A new method for cooling a turbine working blade is that through the nozzles of the annular swirl apparatus, tangentially spaced along the circumference tangentially with rotation in the direction of rotation of the turbine coaxially with the entrance to the smooth channel of each working blade, an intermittent supply of cooling air is performed. As a result of the periodic movement of shock waves from the nozzles of the swirling device, forced vibrations of cooling air with the frequency of the first resonant harmonic are excited in the channel of the blade. Moreover, the oscillations of the cooled air create with a frequency due to resonance conditions

sound speed

and wavelength

defined by the relation

,

where n is the number of revolutions of the turbine rotor at the steady-state mode of operation, in which the gas turbine engine can work for unlimited time, and n is selected from the condition n = (0.7-0.9) n _(max) ;

n _(max) - the number of revolutions of the turbine rotor at maximum power;

- число воздухоподводящих сопел к каналам охлаждения рабочих лопаток турбины в аппарате закрутки статора;

- the number of air supply nozzles to the cooling channels of the turbine blades in the stator spin apparatus;

λ is the wavelength of the oscillations of the flow of cooling air in the channel;

K is the adiabatic exponent for air;

g is the acceleration of gravity;

R is the gas constant;

T _okh.vozd - the temperature of the cooling air at the entrance to the channel of the working blades;

ι is the length of the channel of the scapula.

These essential features provide a solution to the tasks, as:

- the intermittent supply of cooling air through the nozzles of the annular swirling apparatus located tangentially with a rotation in the direction of rotation of the turbine coaxially with the entrance to the channel of each blade due to the cyclical coincidence of the axes of the channels of the nozzles of the swirling device with the entrance to the channel of each working blade located tangentially with a turn on the front end of the shank of the blade, as a result of the periodic movement of shock waves in the cooling channel of each working blade provides deformation of the boundary o layer in the channel and intensifies heat transfer between the heated blade and the air flow, which reduces the flow of cooling air and increases the efficiency of the engine;

- the excitation in the channel of each blade of forced oscillations of cooling air with a frequency of the first resonant harmonic due to the periodic movement of shock waves from the nozzles of the swirl apparatus turbulents the air flow in the channel, which enhances heat transfer between the blade and cooling air and reduces the temperature of the blade, while maintaining reliability and increasing engine life ;

, скоростью звука

и длиной волны

, определяемой соотношением

, обеспечивает понижение температуры в средней части рабочей лопатки, то есть в поле максимальной температуры потока газа из камеры сгорания. Это также сохраняет надежность и увеличивает ресурс двигателя.- the creation of oscillations of the cooled air with a frequency determined by the resonance conditions

sound speed

and wavelength

defined by the relation

, provides a decrease in temperature in the middle part of the working blade, that is, in the field of the maximum temperature of the gas flow from the combustion chamber. It also maintains reliability and increases engine life.

The essential features for the method of cooling the turbine blade can be developed and supplemented.

The supply of cooling air from the nozzles of the swirling device coaxially to the entrance to the channel of each working blade, located tangentially with rotation relative to the longitudinal axis of the engine at the front end of the shank of the blade, increases engine reliability.

Thus, the objectives have been solved to increase the efficiency of gas turbine engines with high-temperature turbines due to the intensification of heat transfer by communicating to the flow of cooling air in the heat exchange channel of each working blade of the turbine the forced oscillations by applying periodic disturbing pulses while maintaining reliability and increasing engine life.

The present invention is illustrated by the following description of a method for cooling a rotor blade of a turbine of a gas turbine engine shown in the drawings of FIG. 1-10, where:

in FIG. 1 is a longitudinal section through a turbine that implements a method for cooling a turbine blade of a gas turbine engine;

in FIG. 2 - view And on the front end of the annular spin apparatus;

in FIG. 3 - distribution of relative heat transfer along the length of the cooling channel;

in FIG. 4 is an oscillogram of the pulsation of the air flow velocity at the entrance to the working blade when the resonance oscillations are excited in the channels of the working blades;

in FIG. 5 is an oscillogram of the pulsation of the air flow velocity at the entrance to the working blade in the absence of resonant vibrations in the channels of the working blades;

in FIG. 6 is a diagram for thermometering a gas turbine engine;

in FIG. 7 is a diagram of the location of measuring points of the surface temperature of the profile of the working blade in the middle section along the height of the blade;

in FIG. 8 is a diagram of measuring gas temperature on a rotating blade;

in FIG. 9 is a diagram of the location of the temperature measuring point of the cooling air at the entrance to the channel of the working blade;

in FIG. 10 is a view B in FIG. 6 front end of the shank of the working blade.

The cooling device for the working blade 1 of a turbine 2 of a gas turbine engine (see Fig. 1, 2) has an air cavity 3 in the combustion chamber 4 and a smooth channel 5 in each blade 1. The device also contains an annular air swirl 6 located on the stator opposite the turbine 2 The air swirling apparatus 6 is provided with nozzles uniformly spaced around the circumference 7. The nozzles 7 are placed tangentially with rotation in the direction of rotation of the turbine 2 coaxially with the inlet 8 into the channel 5 of each blade 1. The inlet 8 into the channel 5 of each working blade 1 is located tangentially rotation about the longitudinal axis of the engine at the front end of the blade root 1.

The cooling of each working blade of a gas turbine engine according to the proposed method is carried out in the following order. When the engine is running, cooling air is taken from the air cavity 3 in the combustion chamber 4 and transported to the swirling apparatus 6. Through the nozzles 7, the interruption of cooling air is carried out from the air swirling apparatus 6 to the inlet 8 into the channel 5 of each working blade 1 of the turbine 2. As a result the periodic movement of shock waves from the nozzles 7 of the spin apparatus 6 excite in each channel 5 of the blade 1 forced vibrations of the cooling air with a frequency of the first resonant harmonic. Oscillations of the cooled air are created with a frequency determined by the resonance conditions, the speed of sound and the wavelength according to predetermined ratios. Thus, the heat transfer in the channel 5 between the blade 1 and the cooling air is intensified, ensuring gas-turbine engine economy while maintaining reliability and increasing the life of the gas turbine engine.

To verify and justify the proposed technical solution, experimental studies were conducted.

According to the author and other sources, both domestic and foreign (SU 699314, 909564, 1368612, 1605129, 1740957; US 5397217), it follows that when the pressure fluctuates in smooth channels, the heat transfer coefficient undergoes a change, in particular, there is an increase in the coefficient heat transfer.

The results of experiments with longitudinal fluctuations in the air flow in the channel were presented in the form of a dependence of the relative heat transfer coefficient on the channel length (see Fig. 3:

where N _u , N _uo is the Nusselt number for pulsation of the air flow and in the absence of ripple, respectively;

x is the current length of the cooling channel of the turbine blade;

d is the diameter of the cooling channel of the turbine blade.

вдоль канала приведены на фиг. 3. Откуда следует, что по длине канала при частоте колебаний, соответствующей первой резонансной гармонике для

At a constant air flow rate, a fixed amplitude of pressure fluctuations and frequency, a change in the local heat transfer coefficient

along the channel are shown in FIG. 3. Whence it follows that along the length of the channel at the oscillation frequency corresponding to the first resonant harmonic for

- средняя амплитуда колебаний давления в трубопроводе,Where

- the average amplitude of pressure fluctuations in the pipeline,

- среднее давление в трубопроводе, коэффициент теплоотдачи может возрастать до двух раз по сравнению с условием, когда резонансные колебания воздушного потока отсутствуют. $$\overline{P}$$

- the average pressure in the pipeline, the heat transfer coefficient can increase up to two times compared with the condition when there are no resonant fluctuations in the air flow.

From FIG. 3 it also follows that when half the wavelength is laid along the length of the channel 5, and the maximum heat transfer falls in the middle of the channel 5. The results of static studies of the heat transfer of the pulsating air flow in the channel were transferred to the channels of the rotating working blades.

In order to assess the nature of the oscillations and their intensity at the entrance to the cooling channels, we measured the pulsations of the cooling air velocity. Measurements of air flow from velocity pulsations were compared with the case of air flow when resonant vibrations were not excited in the channels of the working blades.

When the jets interact with the receiving holes of the blades at the entrance to the cooling channels, oscillations occur with a frequency

- число воздухоподводящих сопел;where for example

- the number of air supply nozzles;

n = 8800 rpm - the number of revolutions of the rotor in cruising mode.

где

To fit half the wavelength along the length of the air cooling channel of the turbine blade, the number of air supply nozzles must be calculated based on the expression

Where

Thus C - speed of sound, f - frequency of oscillations and T _OHL ≅618,2K - cooling air temperature at the inlet of the blades, we have λ = 120 mm, which corresponds to λ / 2 = L, where L -. The length of the rotor blade.

This follows from the oscillogram of the velocity pulsations (see Fig. 4) obtained at the input 8 to the channel 5 of the working blade 1 (see Fig. 1).

Provided that resonant vibrations were not excited in the channels of the working blades, the effect described above was not detected (see Fig. 5).

With resonant vibrations of cooling air in the channels of the working blades, it is necessary that half the wavelength (λ / 2) is laid along the channel length, then the heat exchange undergoes a significant change compared to the condition when it was absent (see table).

Experimental studies of the temperature state of GTE rotor blades were carried out on a single-shaft turbocharger, which was a gas generator assembly (see Fig. 6). For greater reliability of the experimental test results, the cooling efficiency was evaluated under the same conditions: the initial version (without a pulsating supply of cooling air) and the variant with a pulsating air flow. In total, the gas generator was tested 3 times.

Two times the tests were carried out with a pulsating inlet (first and second assembly) and with the original air supply system (third assembly in the absence of ripple).

To determine the relative cooling depth, the GTE rotor blades were finalized and prepared with chromel - alumel thermocouples. The temperature measurement on the surface profile of the standard working blades was carried out in the middle section along the height of the rotating blades (see Fig. 7). The measurement of gas temperature on a rotating blade was carried out according to the circuit shown in FIG. 8. The temperature of the cooling air was measured by thermocouples at the entrance to the channels of the blades (see Fig. 9).

The emf from the thermocouples of the rotor blades was transmitted through insulated wires 9 (see Fig. 6), laid along the disk, and then through a pipeline installed in the shaft of the turbocompressor, to the collector 10 (see Fig. 6) located in the VNA of the high-pressure compressor , and then through copper wires to temperature measuring devices such as EPP-09.

In order to compare the cooling efficiency of the blades with a pulsating flow during the excitation of resonant vibrations in the channels of the working blades with the option when there were no resonant vibrations, the assemblies were selected so that the operating modes for the three gas generator assemblies were the same.

The results of thermometering the working blades of the gas generator for different sections of the profile for all three assemblies are presented in dimensionless form θ in table 1:

,

,

- температура газа на вращающейся лопатке,Where

- gas temperature on a rotating blade,

t _l - the temperature of the scapula,

t _in - temperature of the cooling air.

Based on the experimental study, we can conclude that with resonant vibrations of cooling air in the channels of the blades it is necessary that half the wavelength (λ / 2) is laid along the channel length, then the heat exchange undergoes a significant increase compared to the condition when there are no such vibrations.

To confirm the occurrence of resonant fluctuations in the air flow in the cooling channels of the blades for various methods of supplying cooling air, a measurement was made of the velocity pulsation at the inlet 8 to the channel 5 of the blades 1 (see Fig. 1). The measurement was carried out using the sensor 11 of the hot-wire anemometer (see Fig. 10), the working element of which was a tungsten or platinum thread with a diameter of 10-15 microns and a length L = 3-3.5 mm. In FIG. 10 shows a diagram of the installation of the sensor thread 11 at the input 8 to the channel 5 of the working blades.

The sensor-heated thread 11 of the sensor 11 (Fig. 10) is included in the electrical circuit of the anemometer (not shown) through a current collector, signal converter amplifier, and switch (RU patent No. 137610). The input data input unit, the rotational speed sensor and the hot-wire anemometer are connected by the installation wires 12 (see Fig. 6) to the signal programming and processing unit. The output of the programming and signal processing unit is connected to an indicator input (not shown). The input of the cooling channel is made on the side of the front end of the shank of the blade, and the current of the sensor 11 heated by current is installed radially therein (see FIG. 10) at the inlet 8 to the cooling channel 5 of the blade (see FIG. 1).

n=8800об/ мин - об/мин),Based on an experimental study conducted on a gas generator (

n = 8800 rpm - rpm),

- степень понижения давления на турбине;Where

- the degree of pressure reduction on the turbine;

- температура охлаждающего воздуха на входе в канал охлаждения рабочей лопатки;

- the temperature of the cooling air at the entrance to the cooling channel of the working blades;

- средняя температура газа на рабочих лопатках турбины,

- the average temperature of the gas on the working blades of the turbine,

the following conclusions can be drawn:

- the combination of the jet air supply to the GTE rotor blades with the excitation of resonant vibrations in the internal channels of the rotor blades leads to a noticeable increase in the cooling efficiency of the rotor blades I and II of the assembly (see table 1);

- comparative tests performed on a gas generator with a uniform air supply (III assembly) and pulsating air supply (I and II assembly), provided that half the wavelength is laid along the length of the channel 5 of the working blade 1, showed that with the same operating parameters the relative increase cooling efficiency θ is 55% (see table 1);

- the influence of the method of supplying cooling air to the rotor blades to increase the relative cooling efficiency is also confirmed by direct measurements of the velocity pulsation at the entrance to the rotor blades (see Fig. 4).

Claims (2)

1. The method of cooling the working blades of the turbine of a gas turbine engine, including the selection of cooling air from the air cavity of the combustion chamber, its transportation to the swirl apparatus, made on a stator opposite the turbine disk, and the subsequent supply of cooling air from the swirl apparatus to the rotating channel of each blades, characterized in that, through the nozzles of the annular apparatus, swirls equally spaced along the circumference tangentially with rotation in the direction of rotation of the turbine coaxially with the entrance to the smooth channel of each shovel and perform the intermittent supply of the cooling air, resulting in a periodic motion of shock waves from the nozzles twist apparatus excite each channel in the blade cooling air forced oscillation with the resonance frequency of the first harmonic oscillation with the cooling air created at a frequency determined by the resonance condition

at the speed of sound

and wavelength

defined by the relation

,
where n is the number of revolutions of the turbine rotor at a steady-state mode of operation, in which the engine can run for unlimited time, and n is selected from the condition n = (0.7-0.9) n _(max) ;
n _(max) - the number of revolutions of the turbine rotor at maximum power;
Z is the number of air supply nozzles to the cooling channels of the turbine blades in the stator spin apparatus;
λ is the wavelength of the oscillations of the flow of cooling air in the channel;
K is the adiabatic exponent for air;
g is the acceleration of gravity;
R is the gas constant;
T _okh.vozd - the temperature of the cooling air at the entrance to the channel of the working blades;

- the length of the channel of the scapula. 2. The method according to p. 1, characterized in that the supply of cooling air from the nozzles of the swirl apparatus is carried out coaxially at the entrance to the channel of each working blade, located tangentially with rotation relative to the longitudinal axis of the engine at the front end of the shank of the blade.

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