Method and device for increasing the working capacity of the working blades of high-pressure gas turbines

Abstract

Method for increasing the working capacity of the working blades of the turbine of modern high-temperature gas turbines by reducing their temperature and dynamic stresses, characterized in that 1.1.The influence on the processes of segregation of the flow of "hot" and "cold" gases in the working wheel of the turbine is carried out in the device of the guide vanes (AL) of the turbine; 1.2.The mentioned effect on the process of segregation of the flow of “hot” and “cold” gases in the working wheel of the turbine is achieved by means of circular changes of the minimum area (the “throat”) of the AL F gmin and the flow exit angle from the AL α 1 be achieved, or only by means of the circular changes of the minimum area of ​​the AL F gmin be achieved, or only by means of the circular changes of the flow exit angle from the AL α ; 1.3.The mentioned circular changes F gmin and α1 in strict accordance with the circular change of the temperature of the gas at the outlet from the combustion chamber, ie the channels of the blades of the AL F gmin max with and α 1 the points with the local maximum of the temperature of the gas T gmax correspond, and the channels of the blades of the AL F gmin min with and α 1 the points with local minimum of the temperature of the gas T gmin are equivalent to.

Description

[0001] The invention relates to gas turbine engines (further engines), in particular to the working blades of a high-pressure turbine of modern high-temperature engines.

[0002] As is well known, the working blades of modern high-pressure gas turbines (hereinafter referred to as turbines) operate at the limits of the capabilities of heat-resistant materials. According to statistics, the most common causes of working blade failure are local overheating of the working blades and their bandages, as well as high levels of dynamic stress.

[0003] It is known that the gas temperature at the combustion chamber outlet of an engine is very unevenly distributed along the circumference. Reasons for this include the discrete arrangement of the fuel nozzles, incomplete combustion in the combustion chamber, and uneven mixing of the fuel gas with air jets. It is also known that at turbine guide vanes, the acceleration and ejection of the gas stream occurs at a certain angle into the axial clearance between the guide vanes and the working blades.

[0004] However, due to the above-mentioned temperature cycle irregularity, the flow around the working blades in the moments of passage of the "hot" and "cold" places of the guide vanes differs significantly.

[0005] The comparison of the triangular velocity at the inlet to the working blades at the moments of passage of the maximum and minimum of the circular temperatures provided by the combustion chamber is shown in Figure 1.

[0006] Obviously, in the case of passages of minimum temperature the velocity of the flow at the exit from the guide vanes is much lower than in the case of passages of maximum temperature.

[0007] Since the combustion chamber of modern high-temperature engines has a mass average temperature of gas at the outlet of about 1700...1800 K, which has a circular irregularity Δt = 200...250 K, the gas velocity at the outlet from the guide vanes in "hot" and "cold" places can differ by 5...10%, and the angle of attack - accordingly by 3...5 degrees.

[0008] As the engine approaches stoichiometric, and also due to the tendency to fill the shorter combustion chamber, this difference may increase.

[0009] It is also known that the guide vanes of the high pressure turbine (HDT) of modern high-temperature engines have the developed convection film cooling system and give out 6...7% of the cooling air, of which 1.5...2% of the cooling air is spent directly on the trailing edge, the rest is spent on creating the film protection.

[0010] Obviously, the guide vanes with such cooling system will generate sufficiently strong trails behind the blades, while the braking temperature and speed of the flow in the trail will be significantly lower than in the main gas flow.

[0011] The working blades of the turbine, rotating, "cut through" the tracks of the guide vanes and periodically appear in uncalculated conditions of flow around the gas stream with the relatively low speeds and temperatures.

[0012] In this way, two levels of unevenness of gas temperature and speed at the outlet from the guide vanes of the high-pressure turbine (HDT) of modern high-temperature engines are observed: - “the macro-irregularity”, which is caused by the circular irregularity of the combustion chamber, which is divisible by the number of nozzles of the combustion chamber, in the potential (T gmax - T gmin ) is relatively small, but significant in terms of mass expenditure (about 50%); - the “micro-irregularity” caused by the discharge from the guide vanes of the relatively cold air, which is divisible by the number of vanes, in the potential (T gmax - T k.L. ) is large, but according to the mass expenditure it is small (about 6...7%).

[0013] Considering the above, we will note that a series of research works clearly and firmly establish the redistribution of temperatures in the working wheel of the turbine, which consists of 2 processes: - 2-dimensional temperature segregation of the "hot" gas from the "cold" gas, with the "hot" gas being concentrated on the concave surface (trough) of the blades, and the "cold" gas being concentrated on the convex surface of the blades (rear); - the 3-dimensional temperature migrations, when the secondary flows near the end walls transport the "hot" and "cold" gas, redistributing the gas in the convective process.

[0014] Thus, in the work of Kerrerbrock, JL, Mikolajczak, AA (“Intrastator transport of rotor wakes and its effect on compressor performance”, ASME Journal of Engineering for Power, 1970, Vol.92) the explanation of such physical phenomenon as the segregation of the uneven flow on the surfaces of the trough and the backs of the working blades is proposed for the first time.

[0015] In the paper Shang, T., Epstein, AH ("Analysis of hot streak effects on turbine rotor heat load", Transaction of the ASME Journal of Turbomachinery, 1997,Vol.119,pp.544-553) the research of the influence of the irregularity of the combustion chamber on the temperature distribution on the surfaces of the trough and the backs of the working blades of the turbine is presented.

[0016] In the paper Takahashi RK, Ni RH ("Unsteady Euler Analysis of the Redistribution of an Inlet Temperature Distortion in a Turbine", AIAA Paper 90-2262), two effects are cited that can contribute to the redistribution of the hot gas in the rotor channel. The first is the secondary flow in the rotor channel, which is caused by the radial temperature inhomogeneity of the inlet flow. The second is the segregation of the "hot" and "cold" gases, which is caused by the difference in the flow entry angle into the rotor of the "hot" and "cold" gases.

[0017] Since the physics of segregation and migration processes is not yet very clear, it is still impossible to accurately predict the local temperatures of the gas in the rotor channels and clearly determine the contributions to these processes that contribute to the “macro-” and “micro-irregularities”.

[0018] In this situation, research on gas flow irregularities in the gas tract of the turbine wheel, carried out using modern methods, becomes extremely relevant.

[0019] In the work of Abrosimov VN, Blyumin YI etc. ("Experimental determination of the temperature of the gas flowing around the working blades of the turbine of high-temperature gas turbine engines", in the collection "Aviation Industry", issue 5, Moscow, Machine Building, 1986, pages 19-22) the experience of measuring the temperature of the gas flowing around the working blades of the turbines of aircraft engines is described and some results of such measurements are given.

[0020] The measurements were carried out by the modern method, at a distance of 3 mm from the profile, practically without distortion of the flow around the working blades with the author's participation.

[0021] As a result of the analysis of numerous measurements of the temperature of the gas flowing around the working blades of the turbine of modern high-temperature turbofan engines, performed in three characteristic places (on the leading edge, on the trough and on the back of the working blades), the author believes that the general picture of the temperature distribution along the height of the working blades should be close to that presented in Figure 2.

[0022] If the temperature on the leading edge (Figure 2, curve a) is taken as the average temperature field at the inlet to the working wheel, then the temperature curves b (the temperature on the trough) and c (the temperature on the back) would demonstrate the segregation of the temperature in the working wheel (the temperature of the gas on the trough is much higher than the temperature on the back) and the migration of the temperature in the working wheel (the temperature of the gas on the trough in averages lower than the average, less than the temperature on the leading edge, ie the temperature which was in these averages at the inlet to the working wheel).

[0023] In the work of Lapotko VM, Kuhtin JP, Blyumin YI ("The influence of hot and cold gas zones at the inlet to the turbine rotor on the thermal load of the working blades", a presentation at the conference at the Institute of Technical Thermal Physics of the Academy of Sciences of Ukraine, 2001), the influence of the process of segregation of the uneven gas flow on the thermal state of the working blades of the turbine as a result of numerical experiments is shown.

[0024] Thus, qualitatively, the facts of segregation and migration of temperature in the working wheel are no longer in doubt, as is their negative impact on the working blades of the turbine, since the higher temperature of the bypassing gas - this is a higher probability of local overheating of the working blades and bandage, increased thermal stress and expenditure of cooling air, which is necessary to maintain the given working capacity.

[0025] There is no doubt that the main cause of forced vibrations of the working blades is the force interaction of the working blades with the uneven and periodically non-stationary flow. It is obvious that the circular irregularity of the angle of attack at the inlet to the working blades also contributes to the level of their vibratory stresses.

[0026] In our case, the task was to reduce the maximum temperature of the gas in the working wheel of the turbine of the high-temperature gas turbine engine by reducing the segregation of the "hot" and "cold" gas in the relative motion and reducing the dynamic stresses in the working blades.

[0027] The turbine guide vane apparatus according to British Patent N1275970, Class F01D 9 / 02 "The turbine guide vane apparatus or straightening apparatus" is known.

[0028] According to this patent, the guide vane device or turbine directing device consists of at least one row of blades arranged in a circular direction, and the said row has at least two sectors, in each of which the pitch of the blades is such that it determines the same areas of gas entry into the blades, but the pitch of at least one of the sectors differs from the rest (from the rest) in such a way as to compensate for the circular irregularity of the temperature of the incoming gas flow.

[0029] The patent provides for the possibility of additional compensation by changing the profile of the blades or the angle of attack.

[0030] However, the present patent reserves that the mentioned device of guide vanes is inserted behind the high pressure turbine, as it is intended for the alignment of the static pressure on the inlet and the reduction, as a result, of the circumferential flow of the gas and the overheating of the disks and diaphragms.

[0031] In addition, the device of the guide vanes according to the patent N1275970 cannot be used to solve the problem in our case, because the proposed solution concerns only the inlet into the grid of the guide vanes, ensuring the correspondence of the maxima and minima of the circular temperature of the gas to the maxima and minima of the area of ​​the inlet into the blades, does not change the areas of the outlet from the blades, the so-called "throat" of the grid, their minimum area F gmin , which determines the magnitude of the velocity of the flow exiting the guide vanes.

[0032] Nevertheless, the device of guide vanes according to the British patent N1275970 as the prototype of the proposed device can be adopted.

[0033] Thus, the aim of the proposed invention was to increase the efficiency of the working blades of the high pressure turbine by reducing their temperature and thermal stresses in the conditions when the temperature of the gas from the trough will decrease thanks to the proposed method.

[0034] The aim is achieved by introducing into the known technical solution according to patent N 1275970 the improvement which consists in the device of the guide vanes of the HDT with the variable area of ​​the throat of the channel F gmin along the circle.

[0035] The agreement of the maxima T gmax and the Minima T gmin the circle temperature of the gas of the maximum (F gmin max) and minimal (F gmin min ) the area of ​​the throat of the channel of the blades is ensured the area of ​​the throat of the channel of the blades is ensured.

[0036] This means that the area of ​​the combustion chamber discharge section with the maximum gas temperature is assigned the group of guide vanes or one guide vane of the HDT with (F gmin max ), and the area of ​​the discharge section of the combustion chamber with the minimum temperature of the gas - the group of guide vanes or one guide vane of the HDT with

[0037] It is quite obvious that the same result can be achieved by changing the flow exit angles from the guide vanes or by combining the changes in the minimum areas (the “throat”) of the guide vanes and the flow exit angles from the guide vanes.

[0038] Figure 3 shows an example of the design of the guide vane sector of the HDT according to the present invention, where the part of the gas temperature distribution along the circumference of the combustion chamber is also shown schematically and the principle of correspondence of the maximum and minimum temperature values ​​to the maximum and minimum values ​​of the throat area F gmin is illustrated accordingly.

[0039] The proposed improvement allows to ensure the alignment of the speeds of the outlet from the guide vanes along the circle , since at the point of maximum temperature due to the fact that the area of ​​the throat F gmin maximum is met, the relative reduction of the speed is ensured, and at the point of the temperature minimum as a result of the execution the areas of the throat F gmin minimum is met, the relative increase in speed is ensured. F

[0040] The orientation of the velocities of the gas exit from the guide vanes C 1 In the circular direction, the alignment of the triangular speeds will ensure, and this will lead to a reduction in the segregation of the gas temperature in the working wheel and will also lead to a reduction in the circular irregularity of the angles of attack of the profile of the blades of the working wheel.

[0041] The proposed technical solution was analyzed for the significance of its differences. Technical solutions with the specific features of the declared device were not found.

[0042] For this reason, the author considers that the declared technical decision has the essential differences.

[0043] The invention is illustrated by the drawings, where:

[0044] Figure 1 - comparison of the triangular speeds at the inlet to the working blades at the moments of passage of the maximum and minimum gas temperature; The designations: a - scanning of a part of the gas temperature distribution in the perimeter of the combustion chamber; b - scanning of the section of the guide vanes, which is satisfied on the mean diameter.

[0045] Figure 2 - the results of measuring the temperature of the gas flowing around the working blades of the HDT of the modern turbofan engine. The designations: - H- the height of the working blades a,b,c - the temperature of the gas, which was measured on the inlet edge, on the trough, on the back, respectively.

[0046] Figure 3 - the scheme of the design of the guide vanes of the HDT according to the proposed invention, which shows the correspondence of the maxima and minima of the circular gas temperature to the maximum and minimum of the area of ​​the throat of the guide vanes F gmin illustrated. The designations: a - scanning of a part of the gas temperature distribution in the perimeter of the combustion chamber; b - scanning of the section of the guide vanes, which is satisfied on the mean diameter.

[0047] The application of the proposed invention will allow reducing the temperature of the gas flowing around the working blades from the trough (while maintaining the same value as the average gas temperature at the turbine inlet). This will ensure an increase in the service life of the working blades or, while preserving the service life, will allow improving the specific parameters of the engine. At the same time, the use of the invention will lead to a reduction in the level of dynamic stresses in the working blades, which will also ensure an increase in service life. Patent literature 1. Kerrerbrock, JL, Mikolajczak, AA (“Intrastator transport of rotor wakes and its effect on compressor performance”, ASME Journal of Engineering for Power, 1970, Vol.92) 2. Shang, T., Epstein, AH (“Analysis of hot streak effects on turbine rotor heat load”, Transaction of the ASME Journal of Turbomachinery, 1997, Vol. 119, pp. 544-553) 3. Takahashi RK, Ni RH ("Unsteady Euler Analysis of the Redistribution of an inlet Temperature Distortion in a Turbine", AIAA Paper 90-2262) 4. Abrosimov VN, Blyumin YI etc. ("Experimental determination of the temperature of the gas flowing around the working blades of the turbine of high-temperature gas turbine engines", in the collection "The Aviation Industry", Issue 5, Moscow, Machine Building, 1986, pages 19-22) 5. Lapotko VM, Kuhtin JP, Blyumin YI ("The influence of hot and cold gas zones at the turbine rotor inlet on the thermal load of the working blades", presentation at the conference at the Institute of Technical Thermal Physics of the Academy of Sciences of Ukraine, 2001)

Claims

[1] Methods for increasing the efficiency of the working blades of the turbine of modern high-temperature gas turbines by reducing their temperature and dynamic stresses, characterized by , that 1.1.The influence on the processes of segregation of the flow of "hot" and "cold" gases in the working wheel of the turbine is carried out in the device of the guide vanes (AL) of the turbine; 1.2.The mentioned effect on the process of segregation of the flow of “hot” and “cold” gases in the working wheel of the turbine is achieved by means of circular changes of the minimum area (the “throat”) of the AL F gmin and the flow exit angle from the AL α 1 be achieved, or only by means of the circular changes of the minimum area of ​​the AL F gmin be achieved, or only by means of the circular changes of the flow exit angle from the AL α ; 1.3.The mentioned circular changes F gmin and α1 in strict accordance with the circular change of the temperature of the gas at the outlet from the combustion chamber, ie the channels of the blades of the AL F gmin max with and α 1 the points with the local maximum of the temperature of the gas T gmax correspond, and the channels of the blades of the AL F gmin min with and α 1 the points with local minimum of the temperature of the gas T gmin are equivalent to. [2] Device for the turbine guide vane apparatus (AL), characterized by , that the AL with the variable area of ​​the “throat” of the channels of the blades F gmin and with the variable angle of exit α 1 of the gmin Flow from the guide vanes along the circle is fulfilled. The correspondence of the local maxima of the circular temperature of the gas to the maximum areas F gmin max and angles α 1 max is guaranteed. Analogously, the correspondence of the local minima of the circular temperature of the gas to the minimum areas F gmin min and angles α 1 min is guaranteed, ie, the area of ​​the exhaust section of the combustion chamber with the local circular maximum of the gas temperature corresponds to the group of blades of the AL with F gmin max and α 1 max and the area of Exhaust section of the combustion chamber with the circle minimum of the temperature of the gas the group of blades of the AL with F gmin min and α 1 min corresponds. [3] Device for the guide vane apparatus (AL) according to claim 2, characterized by that it only has the variable minimum area of ​​the “throat” of the guide vanes F gmin along the circle is fulfilled. [4] Device for AL according to claim 2, characterized by that it only depends on the variable angle of the flow exit from the guide vanes α 1 along the circle is fulfilled. [5] Device for AL according to claim 2, characterized by that the ratio of the maximum, minimum and nominal areas of the “throat” of the channel of the blades F gmin max , F gmin min , and F gmin are located within: (F gmin max ) / (F gmin ) = 1.02... 1.10 (F gmin min ) / (F gmin ) = 0.9... 0.98

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