JPS5849682B2 - Turbine casing manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a casing for a vaneless nozzle turbine, such as a radial turbine.

A normal turbine has a nozzle blade and a rotor blade, and in order to adjust the flow rate characteristics such as the rotation speed and the relationship between the state quantity of the working fluid and the flow rate, it is necessary to adjust the throat area of the nozzle blade for the same rotor blade. A method is adopted in which the minimum area of the nozzle blade open passage is changed.

However, in a vaneless nozzle turbine having no nozzle blades, such as a radial turbine or an axial flow turbine, it is impossible to use the above-mentioned method to adjust the flow characteristics.

Therefore, in the case of a radial turbine as shown in FIGS. 1 and 2, the part corresponding to the winding end point of the volute chamber 2 that accommodates the rotor blade (impeller) 1, that is, the part corresponding to the winding end point of the volute chamber 2 and this volute chamber A plurality of types of castings of the casing 5 with different passage cross-sectional areas (volute throat area) At of the tongue portion 4 at the tip of the tongue portion 4 forming the boundary with the guide tube portion 3 that guides the working fluid are prepared. The flow rate characteristics are adjusted by selecting a volute having a throat area At.

Let Aen be the volute inlet area of the inlet of the guide tube part 3,
When the volute throat area is At, the changes in the cross-sectional areas of the flow paths in the guide tube section 3 and the volute chamber 2 are shown in Figure 3 for the large flow rate type and the small flow rate type, where θ is the tongue. The area near the tip of the part is O, and it is the rotation angle in the gas flow direction (arrow in Figure 2).L, shown by a solid line, is the flow rate characteristic of the large flow type, and M, shown by a broken line, is the flow rate characteristic of the small flow type. show.

In such a conventional method, it is necessary to prepare a plurality of types of castings for porlute casings, which is disadvantageous in terms of productivity and also makes it impossible to minutely adjust the flow rate characteristics.

The present invention enables fine adjustment of flow characteristics by casting one type of casing and changing the position of the tip of the tongue, which communicates with the volute chamber that accommodates the rotor blades. The turbine casing has a guide pipe portion formed such that its cross-sectional area gradually decreases toward the spiral chamber, and a tongue portion forming a boundary between the spiral chamber and the guide tube portion is provided. extended and formed so as to approach the vicinity of the rotor blade,
The position of the tip of the tongue is changed by scraping off the tip of the tongue, and the tip of the tongue is removed. The method of manufacturing a turbine casing is characterized in that flow characteristics can be changed by changing the cross-sectional area of the guide pipe portion.

Next, an explanation will be given based on an embodiment of the present invention shown in FIGS. 4 to 6. FIG. 4 is a sectional view of a casing 5a of a radial turbine, and the turbine casing 5a is a volute chamber 2a that accommodates a rotor blade 1a. and a guide pipe portion 3a formed such that the flow passage cross-sectional area gradually decreases as the working fluid is guided into the spiral chamber 2a toward the spiral chamber 2a. The tongue portion 4a that forms the boundary with the guide pipe portion is formed up to the vicinity of the position B3 closest to the rotor blade 1a.3 The turbine casing 5a is cast so that the tongue portion 4a approaches the vicinity of the rotor blade in this way. After that, the tongue portion 4a is shaved off from the tip according to the required flow characteristics to change the passage cross-sectional area At3 at the position B3 to the passage cross-sectional area At at the position B1.
A desired passage cross-sectional area can be obtained within the range of .

As is clear from the drawing, the size relationship of the passage cross-sectional area is A13.
<At2<At1≦Aen, and by scraping off the tongue portion 4a, the volute throat area can be expanded to the maximum At1.

5 and 6 show a method of manufacturing an axial flow turbine as another embodiment of the present invention, in which the casing 5b is connected to the rotor blade 1b.
It consists of a spiral chamber 2b for accommodating the fluid, and a guide pipe portion 3b communicating with the spiral chamber 2b to guide the working fluid.
is cast so as to extend to the vicinity of position B3 closest to the rotor blade 1b.

As in the case of the embodiment shown in FIG. 4, if the passage cross-sectional area of the most dog is At1, the minimum passage cross-sectional area is At3, and the intermediate passage cross-sectional area is At2, then when the tongue portion 4b is scraped off, the passage cross-sectional area is can be varied from a maximum of At1 to a minimum of A t s.

According to the present invention, the tongue is formed to be long and close to the vicinity of the rotor blades, and the tongue is shaved off in accordance with the desired flow characteristics, so the volute throat area can be freely adjusted and the flow characteristics It is possible to significantly change the flow rate and also finely adjust it, and there is no need to manufacture many types of casings, resulting in a nozzle returbine with good productivity and excellent flow rate adjustment ability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a radial turbine, FIG. 2 is a sectional view taken along the line ■-■ in FIG. FIG. 5 is a sectional view showing another embodiment of the present invention in the case of manufacturing a casing for an axial flow turbine;
FIG. 6 is a horizontal view showing a cylindrical section of the casing shown in FIG. 5 and the turbine rotor blade at the average blade height diameter developed in the rotational direction of the turbine rotor blade. In the drawings, 2a and 2b are spiral chambers, 3a and 3b are guide pipe portions, 4a and 4b are tongue portions, and 5a and 5b are casings.

Claims (1)

[Claims] 1. A turbine casing having a volute chamber for accommodating a rotor blade and a guide pipe portion communicating with the vortex chamber and having a cross-sectional area gradually decreasing toward the vortex chamber. A tongue forming a boundary between the spiral chamber and the guide tube portion is formed to extend so as to approach the vicinity of the rotor blade, and the position of the tip of the tongue is changed by scraping off the tip of the tongue. A method of manufacturing a turbine casing, characterized in that the cross-sectional area of the guide tube section at the tip of the tongue section is changed to change flow characteristics.