RU2576392C2 - Cylinder steam turbine with regulatory compartment - Google Patents

Abstract

FIELD: combined heat and power.

SUBSTANCE: invention relates to a power system and can be used when designing or upgrading steam turbines. Cylinder of a steam turbine with a control compartment, consisting of outer and inner shells of steam input pipes, annular steam supply chamber in the flow passage with unidirectional movement vapor stream consisting of the non-regulated pressure stages, clips, mounted in the outer casing of the cylinder. Inner cylinder body has several pressure stages, regulates compartment. Other unregulated stage are located in the outer cage of the cylinder barrel. Annular chamber steam divided by radial partitions, made of two parts with a clearance there between to steam supply section coinciding with the sections of the guide apparatus of the first stage formed by guide vanes with the lengthened towards the steam input chord and the geometry of the airfoil, which coincides with the same outline points of the blades guide vanes.

EFFECT: improved internal efficiency of the flow and the efficiency in the control compartment is achieved, with the exception of heating the cylinder body at high voltages from the internal steam pressure, ensuring the temperature of the cylinder body symmetry to the longitudinal axis, no nozzle boxes.

1 cl, 6 dwg

Description

The invention relates to a power system and can be used in the development or modernization of steam turbines.

Steam turbines of a single-case and two-body design of an active-type high-pressure cylinder with nozzle steam distribution and a flow part including a one- or two-stage control stage and unregulated stages are known. The purpose of the control stage is to lower the steam temperature and pressure before entering the unregulated stages to a level that ensures long-term reliable operation of the metal of the cylinder body and the metal of the rotor, as well as reducing the number of stages and reducing the length of the turbine. This is achieved by increasing the triggered heat transfer at the control stage, for which either its average diameter increases compared to subsequent unregulated stages, if the control stage is a single-stage pressure stage, or it is performed as a two-stage speed stage.

For examples of such a constructive solution, see, for example, E.A. Kraft "Modern steam turbines", Moscow-Leningrad, Energoizdat, 1933, fig. 122-133, 138-140, 147, 148, 150, 151, 155, 159; L.I. Tubyansky and L.D. Frenkel “LMZ high-pressure steam turbines”, Moscow-Leningrad, Gosenergoizdat, 1956, FIG. 1-6; E.I. Benenson L.S. Ioffe “Heat-generating steam turbines”, Moscow, Energy, 1976, fig. 1.1-1.4, 1.7-1.9; A.G. Kurzon, “Ship steam and gas turbines”, vol. 1, Leningrad, Sudpromgiz, 1958, fig. 2.37, 2.57, 2.61, 2.62; G.D. Barinberg, Yu.M. Brodov et al. “Steam turbines and turbine units of the Ural Turbine Plant”, Yekaterinburg, 2010, fig. 4.1, 4.2, 4.4, 4.5, 4.13, 4.19, 4.64. Numerous publications show the prevalence of the described technical solution.

The control stage includes a nozzle apparatus and a bladed impeller. Steam is supplied to the nozzle apparatus through nozzle boxes fixed to the cylinder body. Steam boxes are attached to nozzle boxes, in which control valves are placed.

In FIG. 1 shows an example of a typical design of a single-cylinder high-pressure cylinder with nozzle steam distribution. A nozzle box 2 is welded to the housing 1, in which the nozzle apparatus 3 is placed. A steam box is welded to the top of the nozzle box, in which the control valve is located. On the side opposite to the outlet section of the nozzle apparatus 3, an end seal is placed. The steam leaving the nozzle apparatus 3 enters the rotor blades 4 of the control stage, then passes through the chamber 5 of the control stage and enters the next unregulated stages 6. The FIG. Figure 2 shows the sweep of the steam channel along the average diameter and shows the internal cavity of the nozzle box 2, the nozzle apparatus 3, consisting of several nozzle segments, each of which has steam channels 7. Thermal calculation of the flow part determines the geometric dimensions of the steam channel, including its spread relative to the cross section perpendicular to the axis of rotation of the rotor (angle of installation), the height of the channel, the number of steam channels in each nozzle segment. There are design intervals between the extreme steam channels of adjacent nozzle segments, the sum of which determines the partiality of the control stage, i.e. fraction of the average diameter circumference occupied by steam channels. As a rule, in real designs of steam turbines with nozzle steam distribution, the partiality is 0.4-0.7.

Increased heat transfer, as well as the partiality of the stage, are factors that reduce the efficiency of the stage to 0.5-0.65, which is confirmed by practical calculations of turbine manufacturing plants, thermal tests of customers and theoretical studies described in scientific publications, for example, A.V. Scheglyaev “Steam turbines”, Moscow, Energoizdat, 1933, are inevitable drawbacks of the known designs of the regulating stages of turbines with nozzle steam distribution.

In addition, the known design does not fully provide a decrease in the temperature of the wall of the cylinder bodies in the chamber of the control stage: the part of the steam entering the end seal loses speed to almost zero. At the same time, a well-known phenomenon occurs - an increase in steam temperature almost to the level of fresh steam temperature, local heating of the wall of the cylinder bodies, an increase in local temperature stresses, the creation of favorable conditions for thermal cracking of the wall of the cylinder bodies, which occurred many times during the operation of T-110 / turbines 120-130, T-60 / 65-130 and others operating at a fresh steam temperature of 555 ° C-565 ° C, but is not observed in turbines operating at a fresh steam temperature of 500 ° C-535 ° C, for example T-50 / 60-8.8.

When operating in variable modes, with reduced loads, temperature asymmetry of the cylinder bodies relative to its axis occurs, leading to pinching of vertical and transverse keys, violation of the freedom of thermal movements and the appearance of increased turbine vibration.

Thus, the main disadvantages of the known design of both single-cylinder and double-cylinder cylinders are as follows:

- low efficiency of steam operation before entering unregulated stages, and in the case of a trace from the partial supply and in the first unregulated stages until a uniform distribution of steam over the entire circumference occurs;

- the real possibility of thermal fatigue cracking of the walls of the cylinder bodies;

- temperature asymmetry of the cylinder bodies relative to its longitudinal axis at low steam flow rates.

The task of the invention is to eliminate the above-described disadvantages, that is, increasing the efficiency of steam by reducing losses from the partial supply of steam, reducing the risk of thermal cracking of the walls of the cylinder bodies, eliminating the temperature asymmetry of the temperature field of the cylinder bodies.

The task is achieved by the cylinder of the steam turbine with a control compartment, consisting of the outer and inner casings, steam inlet pipes, an annular steam supply chamber for supplying steam to the flowing part with unidirectional movement of the steam stream, consisting of unregulated pressure steps, cages installed in the outer cylinder body, characterized in that in the inner cylinder housing there are several unregulated pressure stages forming the control compartment, the remaining unregulated stages are located They are worn in the casing of the outer cylinder body, and the annular chamber of steam supply is divided by radial partitions made of two parts with a guaranteed gap between them into steam supply sections, the number of which coincides with the number of turbine control valves, and coinciding with the sections of the first stage guide vane formed by the guides blades with a chord elongated towards the steam inlet and the geometry of the profile part coinciding with the similar outlines of the other vanes of the guide vane.

The invention is illustrated in FIG. 3, which shows a longitudinal section of a portion of the cylinder with a control compartment installed therein. In the outer casing 1 of the cylinder, an inner casing 2 is installed, in which unregulated pressure steps 3 of the control compartment are located. Steam is supplied to the annular chamber 4 through the nozzles of the outer 1 and inner 2 buildings. The annular chamber 4 is divided into steam supply sections 8, 9, 10, 11 (Figs. 4 and 5) by radial partitions 5, which made it possible to refuse to install nozzle boxes, reduce the heating of the cylinder bodies at high voltages from the internal vapor pressure, and increase the partiality to 0, 9.

The annular chamber 4 itself is formed by the outer shell of the inner housing 2 and the inner shell, which is at the same time a place for installing a seal 6 between the inner 2 and outer 1 casings. An end seal 7 is installed in the outer casing 1. FIG. 4 shows a cross section of the inner cylinder body along the axis of the steam inlet and shows the radial partitions 5 dividing the annular chamber 4 into steam supply sections 8, 9, 10 and 11. In FIG. 5 shows the inner cylinder body in 3D. The number of unregulated pressure steps in the control compartment is calculated so that the pressure of the housing in the housing 12 provides a level of stress in the wall of the outer housing 1 of the cylinder is much less than the limit of long-term strength of the metal of the body at an achieved temperature level. For a turbine with initial steam parameters of 12.8 MPa and t = 565 ° C, the number of steps in the control compartment is optimally no more than 4. In FIG. 3 steam flows through the housing 12, equalizing the temperature of the wall of the inner casing 2, from the seal 6, the design of which is selected so that this flow rate would be slightly greater than the steam leakage through the end seal 7. From the housing 12 the steam enters an unregulated stage, located directly behind the control compartment.

The implementation of the inner case 2 composite of the outer and inner shells makes it easier to install the radial partitions 5 in the annular chamber 4. The partition is made of two parts, one of which is welded into the upper shell, and the other into the lower shell with a technological gap between them, which creates the conditions for flowing steam from one section to another around the entire circumference of the annular chamber. This overflow restores the axial temperature symmetry of the inner casing 2 during transient turbine operation, and especially during start-up, when steam enters the flow part through some of the steam supply sections 8, 9, 10, and 11. FIG. 6 shows a sweep of the first stage guide vanes along the average diameter, which is divided into sections corresponding to the steam supply sections 8, 9, 10 and 11 (indicated in FIG. 4), a guide vane 13 having an elongated chord toward the steam inlet and the profile part geometry matching with similar outlines of the other vanes of the guide vane. The increased chord prevents the free flow of steam between sections 8, 9, 10 and 11 in partial operating modes.

The claimed invention achieves the following results.

1. Due to the increased partiality up to 0.9, the efficiency of the flow part located in the control compartment increases to 0.85, the internal efficiency of the flow part of the cylinder increases to 0.875-088. This was shown by the performed thermal calculations.

2. The heating of the cylinder bodies at high voltages from the internal vapor pressure is excluded.

3. Provided temperature symmetry of the cylinder bodies relative to the longitudinal axis.

4. Nozzle boxes are missing.

Claims (1)

A cylinder of a steam turbine with a control compartment, consisting of the outer and inner housings, steam inlet pipes, an annular steam supply chamber for supplying steam to the flowing part with unidirectional movement of the steam stream, consisting of unregulated pressure steps, cages installed in the outer cylinder body, characterized in that several unregulated pressure stages forming the control compartment are placed in the inner cylinder body, the remaining unregulated stages are located in the clips of the outer case the cylinder, and the annular steam supply chamber is divided by radial partitions, made of two parts with a guaranteed gap between them, into steam supply sections, the number of which coincides with the number of turbine control valves, coinciding with sections of the first stage guide apparatus, formed by guide vanes with elongated towards the steam inlet a chord, but having on the outlet side of the steam geometric shapes coinciding with the geometric shapes of the remaining vanes of the guide vane.

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