High pressure turbine blades. Turbine rotor blades and guide vanes. There are two main types of turbine blades

1. Angle of installation of the profile.

g mouth = 68.7 + 9.33 × 10 -4 (b 1 - b 2) - 6.052 × 10 -3 (b 1 - b 2) 2

g mouth cor. = 57.03 °

g set Wed = 67.09 °

g set per. = 60.52 °

2. The size of the chord of the profile.

b L.sr = S Lav / sin g set av = 0.0381 / sin 67.09 ° = 0.0414 m;

b L.corn = S L.korn / sin g set.korn = 0.0438 / sin 57.03 ° = 0.0522 m;

b L.per = S L.per / sin g set.per = 0.0347 / sin 60.52 ° = 0.0397 m;

S L.corn = To S. root ∙ S HP = 1.15 ∙ 0.0381 = 0.0438 m 2;

S L.per = To S. lane ∙ S HP = 0.91 ∙ 0.0381 = 0.0347 m 2;

3. Step of the cooled working grate.

= TO t ∙

where , TO L = 0.6 - for rotor blades

including cooling

= TO t ∙ = 1.13 ∙ 0.541 = 0.611

where TO t = 1.1 ... 1.15

t L.sr = b HP ∙ = 0.0414 ∙ 0.611 = 0.0253 m

The resulting value t L. sr should be clarified in order to obtain an integer number of blades in the working lattice, which is necessary for the strength calculations of the HPP elements

5. The relative radius of rounding of the trailing edge of the blades is selected in fractions of the lattice spacing 2 = R 2 / t(the value of 2av in the middle section is presented in Table 3). In root sections, the value 2 increases by 15 ... 20%, in peripheral sections it decreases by 10 ... 15%.

Table 3

In our example, we choose: 2cr = 0.07; 2korn = 0.084; 2per = 0.06. Then the fillet radii of the trailing edges can be determined R 2 = 2 ∙t for design sections: R 2av = 0.07 ∙ 0.0252 = 1.76 ∙ 10 -3 m; R 2korn = 0.084 ∙ 0.02323 = 1.95 ∙ 10 -3 m; R 2l.per = 0.06 ∙ 0.02721 = 1.63 ∙ 10 -3 m.

6. Taper angle of the trailing edge of cooled nozzle blades g 2с = 6… 8 °; workers - g 2l = 8 ... 12 °. These figures are on average 1.5 ... 2 times higher than in uncooled blades. In our case, when profiling the rotor blades, we assign g 2l = 10º in all design sections.

7). Constructive angle at the outlet of the nozzle blades a 1l = a 1cm; at the outlet of the rotor blades b 2l = b 2cm + ∆b k, where the middle section Db k = 0;

for root Db k = + (1 ... 1.5) °; for peripheral Db k = - (1 ... 1.5) °, and a 1cm, b 2cm are taken from the table. 2. In our example, we take for the working lattice: Db k = 1.5º; b 2l.sr = 32º18 ′; b 2l.kor = 36º5 ′; b 2 liters of lane = 28º00 ′.

eight). The bend angle of the outlet section of the back of the profile at the middle diameter (occipital angle) g zat = 6 ... 20 °: at M 2 £ 0.8 g zat = 14 ... 20 °; at M 2 "1, g zat = 10 ... 14 °; at M W£ 1.35, g zat = 6 ... 8 °, where ... In root sections, g is taken less than the indicated values ​​by 1 ... 3 °, in peripheral sections it can reach 30 °.

In our example, for the working lattice in the middle section

,

therefore we choose g zat.l.sr = 18º; g add l corn = 15º; g ref. l. = 28º.

The turbine blade apparatus consists of fixed guides and movable rotor blades and is designed for the most complete and economical conversion of the potential energy of steam into mechanical work. The guide vanes installed in the turbine casing form channels in which the steam acquires the required speed and direction. The rotor blades located on the disks or drums of the turbine rotor, under the influence of the steam pressure resulting from the change in the direction and speed of its jet, drive the turbine shaft into rotation. Thus, the blade apparatus is the most critical part of the turbine, which determines the reliability and efficiency of its operation.

The rotor blades have a variety of designs. Fig. 17 shows a blade of a simple type, consisting of three parts: a tail or a leg 2, with which the blade is fixed in the rim of the disk.1 , working part4 , which is under the action of a moving jet of steam, and the tops 6 for fixing the tape band 5, with which the blades are tied in order to create sufficient rigidity and form a channel between them. Intermediate bodies 3 are installed between the blade legs. To prevent the occurrence of thermal stresses during heating and cooling of the turbine, separate groups blades, leaving a gap between the bands of 1-2 mm.

The back of the scapula is called the back; the edge on the steam inlet side is called the inlet edge, and the edge on the steam outlet side is called the trailing edge of the blade. The cross-section of a blade within its working part is called a blade profile. The profile distinguishes between active and reactive blades (Fig. 18). Injection? 1 called the entrance, and the angle? 2 - the outlet angle of the scapula. The active turbine blades of the previous construction (Fig. 18, a) have an almost symmetrical profile, that is, the inlet angle differs little from the outlet angle. In jet blades (Fig. 18,b ) the profile is asymmetrical, the exit angle is much less than the entry angle. To increase the efficiency of the blades, the leading edges of the profiles are rounded, and the channels formed by the profiles are made converging. Modern profiles of active and reactive blades with a streamlined leading edge are shown in Fig. 18, c andG .

The main characteristics of the blade profile are as follows:

The middle line of the profile is the locus of the centers of the circles inscribed in the profile;

Geometric angles: entrance? 1 l - the angle between the tangent to the center line at the entrance and the axis of the lattice; ? 2 l - the same when exiting;

Angles of entry and exit of steam flow:? 1 - the angle between the direction of the steam flow at the entrance to the rotor blade and the axis; ? 2 - the same when exiting;

Attack anglei - the angle between the direction of the steam flow at the entrance to the rotor blade and the tangent to the entrance edge along the middle LINE, i.e.i = ? 1L – ? 1 ;

Profile chordb - the distance between the ends of the midline;

Installation angle? Have - the angle between the chord of the profile and the osm. lattices;

Profile width B - blade size in the direction of the turbine axis;

Stept - the distance between similar points of adjacent profiles.

The leading edge of modern guide and rotor blade profiles is insensitive to the deviation of the flow angle at the inlet. This allows, when calculating the blade profile, to allow angles of attack of up to 3-5 ° in any section along the blade height. The leading edge of the blade profiles at subsonic speed is made thick and carefully rounded, which reduces vortex losses at the channel inlet and increases the vibration, corrosion and erosion resistance of the blades. This shape of the leading edge provides in variable modes a lesser effect of a change in the angle of attack on the efficiency of the blade, as well as a more complete use of the input energy of the steps.

The geometric characteristics of the active and reactive profiles of the working and guide blades are given in the standards for the blades of ship turbines (Tables 1, 2).

The blade sizes vary widely. In ship turbines, the height of the blades of the first HP stages is small (from 10 mm), and the height of the last HP stages reaches 400 mm. The width of the blades can be 14-60 mm. To reduce weight and reduce stress from centrifugal forces long shoulder blades are given width and thickness, gradually decreasing from stem to apex. On long blades, the bandage is usually not placed, and to obtain greater rigidity, the blades are fastened with cohesive wire in packages of 5-10 blades.

According to the manufacturing method, the blades can be divided into two groups:

1) made by stamping from sheet material (1-2 mm thick) or from rolled profile strips (light-rolled profiles); intermediate inserts for these blades are made separately;

2) manufactured in one piece with intermediate inserts by milling rolled, drawn, forged or cast blanks.

In fig. 17 shown are blades made of rolled profile strips with separate inserts. Mechanical processing of such blades is reduced to milling the stem and top. These blades have a constant profile and are used for low peripheral speeds. For higher peripheral speeds, semi-milled blades from thicker cold-rolled profile strips are used. In such blades, the insert is partially made at the same time with them and the back is milled.

Pa fig. 19 depicts various designs of solid milled blades made in conjunction with rectangular and rhombic hot-rolled strip steel inserts. Bandaging of the shoulder blades (Fig. 19, a) is carried out with a bandage tape. For high peripheral speeds, the blade is made as a whole with a shroud shelf (Fig. 19,b ). Closing, the shelves form a continuous ring-band. As noted above, the width and thickness of the long blades gradually decreases from the stem to the apex (Fig. 19, c). To ensure a shockless steam entry along the entire height, long blades are sometimes made with a variable profile, in which the entry angle gradually increases. Such blades are called helical.

According to the method of attachment to disks or drums, blades of two types are distinguished:

1) with a submerged fit, in which the tails are wound inside special grooves in the rim of the disk or drum;

2) with a riding position, in which the tails are worn on top of the crest of the disk and secured.

In fig. 20 shows the most common scapular tail shapes.

Tails 3-11 are used to attach the guide and rotor blades. Type 6 tails are used in modern turbines of dry cargo ships and tankers. The tail 11 is made about the same width as the rotor blade and is used to attach jet blades. Top-mounted bindings are suitable for long blades subject to significant forces.

The submerged fit vanes are also welded in the individual axial grooves. These mounts provide replacement for any of the blades and also provide the best vibration characteristics and the lightest blade and disc weight. The attachment of the blades to the disc by welding is shown in Fig. 21. The flat tail 2 of the blade 1 enters the groove of the disc rim and is welded to it from both sides. For greater strength, the blades are additionally fastened to the disk with rivets 3 and in the upper part are welded in pairs with shroud shelves 4. The attachment by welding increases the accuracy of blade installation, simplifies and reduces the cost of assembling them. Blade welding is used in gas turbines.

To install the scapular tails, one or two notches (keyhole) are usually made on the circumference of the scapular crown, closed with a lock. When attaching blades with upstream tails of the LMZ type in individual slots and by welding, locking holes and locks are not required.

Usually, the blades are collected from both sides of the locking hole, regardless of the number of locks. In fig. 22 shows some of the designs of the locks.

In fig. 22, and in the area of ​​the lock, the shoulders of the disc rim (shown in dotted lines) are cut off, holding the T-shaped tail. The blades adjacent to the locking insert are, in many designs, stitched with pins and soldered to their intermediate inserts. The locking insert is hammered between the adjacent blades. Through the hole in the cheek of the disc, a hole is drilled in the lock insert, into which the rivet is driven. The ends of the rivet are riveted. In fig. 22, b, the lock is an insert 2 that covers the side cutout in the rim of the disk and is attached with screws1 ... In fig. 22, a two-crown wheel lock is shown. Cut-out for installing locking blades1 are made in the middle of the disc rim between the scapular grooves. The locking blades are fastened with two strips 2, accelerated by a wedge 4, which is attached to the rim with a screw 3. The disadvantages of the above designs of locks include the weakening of the rim by cutouts and holes for screws. In fig. 22, d shows a lock with a wedge of the LMZ design. Locking blades 2 and 3 are made with protrusions at the bottom, extending under the tails of adjacent blades 1 and 4. After installing the lining 7, steel wedge 6 and fitting the locking insert 5, which has a cutout in the lower part, the insert is driven between the locking blades.

The lock, the design of which is shown in Fig. 22, d, is used for jet blades. There is no locking cutout in the rim. The blades with tooth-type shanks are inserted into the rotor slot in the radial direction. Then rotate 90 ° so that the teeth fit into the corresponding grooves in the rim, and move around the circumference to the installation site. After installing all the blades, a locking insert is introduced, consisting of two parts 1 and 4, accelerated by a clip 3. The wedge is held by minted projections 2.

Top-type shanks make it possible to obtain a relatively simple design of the locks. In fig. 22, e shows a lock for a back hammer shank. The locking blade 5 has a shank with a flat slot, which is put on the flange 4 of the rim 1 of the disc and is attached to it with rivets3 ... In the place where the locking blade is installed, the shoulders 2 (shown by the dashed line) are cut off.

The turbine blades under the action of the steam flow of steam from the nozzles can oscillate: 1) in the plane of rotation of the disk - tangential vibration; 2) in a plane perpendicular to the rotation of the disk - axial vibration; 3) torsional. The axial vibration of the blades is related to the vibration of the discs. Torsional vibrations of the blades are characterized by intense vibrations of their tops.

The reliability of the blade apparatus depends on the magnitude and nature of the vibrations that occur both in the blades and in the disks on which they are fixed. In addition, the blades, being elastic bodies, are capable of vibrating with their own frequencies. If the natural frequency of the oscillations of the blades is equal to or a multiple of the frequency of the external force causing these oscillations, then so-called resonant oscillations arise, which do not damp, but continue continuously until the action of the force causing the resonance ceases, or until its frequency changes. Resonant vibrations can cause destruction of rotor blades and discs. To avoid this, the bladed discs of modern large turbines, before being mounted on the shaft, are subjected to tuning, by means of which the frequency of their natural vibrations is changed.

In order to combat vibration, the blades are fastened in bags with banding tape or wire. In fig. 23 shows the attachment of the blades with a cohesive wire, which is passed through the holes in the blades and soldered to them with silver solder. Like a banding tape, a wire around a circle consists of separate segments from 20 to 400 mm long, between which thermal gaps arise. The diameter of the connected wire, depending on the width of the blade, is 4-9 mm.

To reduce the amplitude of vibrations of the packages, a damper wire 2 (bridge) is placed between them, it is soldered to two or three extreme blades of one package, and it passes freelythrough the end blades of the adjacent segment. The resulting friction of the wire against the blades during vibration of the package reduces the amplitude of the vibrations. The holes 1 simplify the installation of the bridge. The material for the manufacture of blades must have sufficient resistance at high temperatures and good machinability, be corrosion and erosion resistant. The blades, operating at a steam temperature of up to 425 ° C, are made of chromium stainless steels of grades 1X13 and 2X13 with a chromium content of 12.5-14.5%. At higher temperatures (480-500 ° C), chromium-nickel stainless steels with a nickel content of up to 14% are used. Blades operating at a steam temperature of 500-550 ° C are made of EI123 and EI405 austenitic steels with a nickel content of 12-14% and chromium of 14-16%. Cast blades are made of 2X13 steel. The material for the inserts is carbon steel of grades 15, 25 and 35, for the banding tape, cohesive wire, rivets for the blades and rivets of the locks - stainless steel 1X13.

Silver solder of PS grades is used for soldering of bandage tapes and cohesive wire. R 45 and PS R 65 with a silver content of 45 and 65%, respectively.

The HPT rotor consists of an impeller (a disk with rotor blades), a labyrinth disk, and a HPT shaft.

The working blade of the HPT - cooled, consists of a shank, a stem, a feather and a shroud shelf with combs. Air for cooling is supplied to the shank, passes through radial channels in the body of the blade airfoil, and exits through the holes in the front and rear parts of the blade airfoil into the flow path. Two blades are installed in each groove of the disc. The blades are connected to the disk with herringbone-type locks. The labyrinth disk and the HPT disk are cooled by air due to the HPC.

The low-pressure turbine consists of a rotor and a housing of the turbine supports with a high-pressure pump nozzle. The rotor of the injection pump consists of an impeller (disk with rotor blades) and a shaft of the injection pump, connected by bolts. The rotor blades of the high pressure fuel pump are uncooled and are connected to the disk with herringbone-type locks. The disk is cooled with air taken from the HPC.

In the housing of the turbine supports, the outer and inner shells are interconnected by struts passing inside the hollow blades of the nozzle apparatus of the second stage of the turbine. Oil and air pipelines also pass through the blades. In the housing of the turbine bearings, there are assemblies of the rear bearings of the low and high pressure rotor bearings.

The nozzle blades, cast in the form of sectors with three blades per sector, are cooled with air taken from the fourth stage of the HPC.

The fan turbine consists of a rotor and a stator. The fan turbine stator consists of a casing and five nozzle assemblies, assembled from individual cast sectors, with five blades per sector. The rotor of the turbine of the fan is of a disc-drum design. The discs are connected to each other and to the fan turbine shaft by bolts. Blades, both nozzle and working, uncooled; the disks of the fan turbine are cooled with air taken from the HPC. The rotor blades of all stages of the TV rotor are bandaged and connected to the discs with herringbone-type locks.

The turbine outlet consists of a rear support housing, an inner loop jet nozzle and a drain.

On the housing of the rear support of the turbine there are points of attachment of the units of the rear belt of the engine mount to the aircraft. The rear engine mount is mounted on a power ring, which is part of the outer shell of the rear support housing. The bearing unit of the fan rotor is located inside the housing.

In the racks connecting the inner and outer shells of the case, the communications of the rear support of the fan rotor are located.

The operating mode of the TO and TR zones
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Calculation of the number of TP posts
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Definition of the site program
A site program is a defined or calculated amount of work. The scope of work of the sections of the repair depot depends on the number of cars entering the depot. So the APU program corresponds to the planned program of a particular depot. , The program of the bogie section takes into account that all bogies from ...

Scapula is a working part of the turbine rotor. The step is securely fixed at the optimal angle of inclination. The elements work under colossal loads, therefore the most stringent requirements for quality, reliability and durability are imposed on them.

Application and types of blade mechanisms

Shovel mechanisms are widely used in machines for various purposes. They are most commonly used in turbines and compressors.

The turbine is a rotary engine that operates under the influence of significant centrifugal forces. The main working body of the machine is the rotor, on which the blades are fixed along the entire diameter. All elements are placed in a common body of a special shape in the form of injection and delivery pipes or nozzles. A working medium (steam, gas or water) is supplied to the blades, driving the rotor.

Thus, the kinetic energy of the moving stream is converted into mechanical energy on the shaft.

There are two main types of turbine blades:

1. Workers are on rotating shafts. The parts transfer the mechanical net power to the attached working machine (often a generator). The pressure on the rotor blades remains constant due to the fact that the guide vanes convert the entire enthalpy difference into flow energy.
2. The guides are fixed in the turbine housing. These elements partially transform the energy of the flow, due to which the rotation of the wheels receives a tangential force. In a turbine, the enthalpy difference must be reduced. This is achieved by reducing the number of steps. If too many guide vanes are installed, stall will threaten the accelerated flow of the turbine.

Turbine blade manufacturing methods

Turbine blades are made by investment casting from high quality rolled metal products. A strip, a square is used, the use of stamped blanks is allowed. The latter option is preferable in large-scale industries, since the metal utilization rate is quite high, and labor costs are minimal.

The turbine blades are subject to mandatory heat treatment... The surface is coated with protective compounds against the development of corrosion processes, as well as special compounds that increase the strength of the mechanism when operating at high temperatures. For example, nickel alloys are practically not amenable to mechanical processing, so stamping methods are not suitable for the production of blades.

Modern technologies have presented the possibility of producing turbine blades by the directional solidification method. This made it possible to obtain working elements with a structure that is almost impossible to break. The method of manufacturing a single-crystal blade, that is, from one crystal, is being introduced.

Turbine blade manufacturing steps:

1. Casting or forging. Casting allows you to get high quality blades. Forging is made by special order.
2. Mechanical restoration. As a rule, automatic turning and milling centers are used for machining, for example, the Japanese Mazak complex, or for milling machining centers, such as the Swiss-made MIKRON.
3. Only grinding is used as a finishing treatment.

Requirements for turbine blades, materials used

Turbine blades are operated in an aggressive environment. High temperature is especially critical. Parts work under tension in tension, therefore, high deforming forces arise, stretching the blades. Over time, the parts touch the turbine housing, the machine is blocked. All this determines the use of materials the highest quality for the manufacture of blades capable of withstanding significant torque loads, as well as any forces under high pressure and temperature conditions. The quality of the turbine blades is used to assess the overall efficiency of the unit. Recall that a high temperature is required to increase the efficiency of a Carnot cycle machine.

Turbine blades- a responsible mechanism. Thanks to it, the reliability of the unit is ensured. Let's highlight the main loads during the operation of the turbine:

• High peripheral velocities occur under high temperature conditions in the steam or gas stream, which stretch the blades;
• Significant static and dynamic temperature stresses are formed, not excluding vibration loads;
• The temperature in the turbine reaches 1000-1700 degrees.

All this predetermines the use of high-quality heat-resistant and stainless steels for the production of turbine blades.

For example, grades such as 18Kh11MFNB-sh, 15Kh11MF-sh, as well as various nickel-based alloys (up to 65%) KhN65KMVYUB can be used.

The following components are additionally introduced as alloying elements in the composition of such an alloy: 6% aluminum, 6-10% tungsten, tantalum, rhenium and a little ruthenium.

Scapular mechanism must have a certain heat resistance. For this, complex systems of cooling channels and outlet openings are made in the turbine, which ensure the creation of an air film on the surface of the working or guide vane. The hot gases do not touch the blade, therefore minimal heating occurs, but the gases themselves do not cool down.

All this increases the efficiency of the machine. The cooling channels are formed with ceramic rods.

For their production, aluminum oxide is used, the melting point of which reaches 2050 degrees.