RU2046961C1 - Take-off chamber for steam turbine - Google Patents

Abstract

FIELD: heat power engineering. SUBSTANCE: ring converging-diverging passageway connects the flowing part of the turbine with the take-off chamber. The average ellipticity of the diverging part is equal to or greater than 1.15 but no less than 1.25, the divergence angle being equal to 2-7°. The ratio of the minimum to maximum cross-section is equal to 0.03-0.35. The outlet diameter of the diffuser has an eccentricity with respect to the inlet diameter. The ratio of the eccentricities is 0.04-0.075. The minimum inlet diameter of the diffuser is located from the side of the take-off branch pipes. EFFECT: improved design. 2 dwg

Description

 The invention relates to turbine construction and can be used in steam turbines.

A known chamber for selecting a steam turbine formed by an aperture between the housing of the latter and the clips of the diaphragms, between which a bezel-less diffuser with a ratio of exit and entry areas of 15-25 is installed [1]
The disadvantage of such a sampling chamber is the presence of a return flow area along the wall of the annular channel, which reduces the efficiency of the bezel-less diffuser due to its unstable operation and the possibility of flow separation near the wall. At the same time, there is no possibility of using the kinetic energy of the sampling stream, leaving the flow part and entering the sampling chamber, due to a sharp turn of the flow at the entrance to the annular channel.

= D₂/D₁, ширина горлового сечения на входе S₁ и выходе S₂) диффузора обеспечивается это соотношение и как изменение каждого из них влияет на окружную неравномерность параметров в проточной части, а следовательно, и на переменные аэродинамические силы, действующие на рабочие лопатки околоотборного отсека, а также влияет на потери в тракте отбора.In addition, the indicated ratio of the area of the bladeless diffuser does not allow the designer to clearly make a decision due to which of the variable parameters (opening angle γ, diffuser radial

= D ₂ / D ₁ , the width of the throat section at the inlet S ₁ and the outlet S ₂ ) of the diffuser provides this ratio, and how a change in each of them affects the circumferential unevenness of the parameters in the flow part, and therefore also on the variable aerodynamic forces acting on the working the blades of the near-sampling compartment, and also affects the losses in the sampling path.

 A steam turbine extraction chamber is also known, formed by an aperture between the housing of the latter and the clips of diaphragms installed with the formation of an annular channel, which is made with a variable profile formed by smoothly conjugated pinch inlet and outlet sections, the latter of which are located with a diverging slope along the flow [2 ] In this sampling chamber there are no return flow zones at the entrance to the annular channel due to the acceleration of the flow in the inlet (confuser) section, while the velocity profile in the channel e aligned and outlet (diffuser) portion operates more efficiently, which reduces losses in the screening tract.

 However, with the diffuser design of the slit of the sampling path, the circumferential non-uniformity of the parameters in the flowing part increases due to a decrease in hydraulic resistance along the propagation path of the unevenness caused by non-axisymmetric removal of the working medium from the sampling chamber. This unevenness of the parameters in the flow part ultimately leads to an increase in the variable aerodynamic forces acting on the rotor blade and reducing the reliability of the entire turbine unit. In this regard, the most important question is excluded from consideration as how this design of the annular channel affects the circumferential unevenness of the parameters in the flow part, and consequently the variable aerodynamic forces.

 The aim of the invention is to increase the reliability and efficiency of operation of both the turbine and the turbine plant as a whole, in a wide range of flow rates of the selected steam by optimizing the size of the diffuser annular channel at the entrance to the selection chamber and its degree of variability in the circumferential direction.

1,15 <

=

< 1,25 и углом раскрытия 2^о ≅ γ ≅ 7^о, где D_2ср средний выходной диаметр диффузора, при этом входной участок кольцевого канала имеет пережим с относительной шириной

0,03-0,35, где S ширина пережима входного участка кольцевого канала; l длина лопатки предотборной ступени, а выходной диаметр диффузора выполнен с эксцентриситетом по отношению к входному участку, относительная величина которого составляет

0,04-0,075, где

.To do this, in the steam turbine’s selection chamber, formed by an aperture between the turbine casing and the diaphragm clips and connected with the flowing part behind the working blade of the pre-selection stage by an annular channel, the latter is made decreasing in the circumferential direction and has a minimum value from the side of the sampling pipes, the diffuser section of the channel is made with an average radiality

1.15 <

=

<1.25 and an angle ^of opening 2 ≅ γ ≅ 7 ^a, where D _2Cp average diffuser outlet diameter, the inlet portion of the annular channel has a relatively wide perezhim

0.03-0.35, where S is the pinch width of the input section of the annular channel; l the length of the blades of the pre-selection stage, and the outlet diameter of the diffuser is made with eccentricity with respect to the inlet section, the relative value of which is

0.04-0.075, where

.

 In FIG. 1 shows a fragment of the flow part of the turbine with a selection chamber; in FIG. 2, section AA in FIG. 1.

=

≅ 1,25 и углом раскрытия 2^о ≅ γ ≅ 7^о, где D_2ср средний диаметр выходного сечения диффузора, равный полусумме максимального D_2max и минимального D_2min диаметра выходного сечения диффузора; D₁ входной диаметр диффузора, и имеет за входным участком 9 кольцевого канала 5 пережим 10 с относительной шириной

0,03-0,35, где S ширина пережима 10 кольцевого канала 5; l длина лопаток 11 предотборной ступени. Относительная величина эксцентриситета выходного сечения диффузора определяется как

и находится в диапазоне

0,04-0,075.The selection chamber 1 is formed by an aperture between the outer casing 2 of the turbine and the clips 3 of the diaphragms 4 mounted to form an annular channel 5 communicating the cavity of the chamber 1 with the turbine flow part 6. The annular channel 5 has a diffuser section 7, the radial size of which is made decreasing in the circumferential direction, and has a minimum value from the side of the nozzles 8 selection. The diffuser section 7 is made with an average relative diameter of 1.15 ≅

=

≅ 1,25 and the angle ^{of the} opening 2 ≅ γ ≅ 7 ^a, where D _2Cp average diameter of the outlet section of the diffuser is equal to half the sum of the maximum and minimum D _2max D _2min diameter of the outlet section of the diffuser; D _{1 the} input diameter of the diffuser, and has an input 10 with a relative width beyond the input section 9 of the annular channel 5

0.03-0.35, where S is the pinch width 10 of the annular channel 5; l the length of the blades 11 of the pre-selection stage. The relative value of the eccentricity of the outlet cross section of the diffuser is defined as

and is in the range

0.04-0.075.

 The selection camera works as follows.

0), а в противоположной от них зоне снижается, что приводит к уменьшению окружной неравномерности давления в проточной части 6, а следовательно, и переменных аэродинамических сил, действующих на лопаточный аппарат околоотборного отсека и снижающих его надежность.The working fluid from the flow part 6 enters the inlet section 9 with pinch 10 of the annular channel 5. Here, the flow is accelerated, while the velocity profile in the channel 5 is leveled. Further, in the diffuser section 7, the flow slows down, and due to the variability in the circumferential direction of the inlet diameter of the diffuser, its regenerative ability is minimal from the location of the branch pipes 8 and maximum from the opposite side. As a result, the pressure in the inlet section 9 in the area of the nozzles 8 of the selection increases (in comparison with option

0), and in the area opposite to them, it decreases, which leads to a decrease in the circumferential pressure unevenness in the flow part 6, and, consequently, of the variable aerodynamic forces acting on the blade apparatus of the near-selection compartment and reducing its reliability.

 In addition, this profile of the annular channel 5 allows you to increase the efficiency of the turbine by optimizing the geometric parameters of the diffuser section 7, and therefore, increasing the pressure in the selection chamber 1 due to a more complete pressure recovery of the annular channel 5.

Claims (1)

STEAM TURBINE SELECTION CAMERA with sampling pipes, formed by an opening between the turbine housing and the clips of the diaphragms and communicated with the groove part behind the working blade of the pre-selection stage by an annular channel having an inlet and outlet diffuser sections with a pinch between them, characterized in that the annular channel is made at the outlet with the radial size decreasing in the circumferential direction, having a minimum value from the side of the sampling pipes, and the diffuser section of the channel is made with an average relative diameter of 1.15 1.25, angle disclosure 2 7 ^o , the relative eccentricity of 0.04 - 0.075, the relative clamping 0.03 0.35, determined by the formulas

Where

average relative diameter of the diffuser section;
D _{2 with p} , D _{2 m a x} , D _{2 m i n} respectively the average, maximum and minimum diameters of the output section of the diffuser section;
D _{1 the} diameter of the input section of the diffuser section at the pinch point;

relative eccentricity;

relative pinch;
S pinch width;
l the length of the working blade of the pre-selection stage.

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