JPS59101505A - Double flow radial turbine - Google Patents

Abstract

PURPOSE:To simplify a nozzle variable mechanism while halving the number of nozzle impellers, removing axial thrust force, and eliminating sealing between the impellers by providing a group of nozzle impellers pointing to the forward edge of a group of buckets at a scroll outlet surrounding the front edge of two sets of the bucket groups. CONSTITUTION:A high pressure operating fluid is fed from a scroll 10 through a nozzle 11 to impellers 12, 13, and discharged into casings 14, 15. The operating fluid passes through the common scroll 10 and nozzle 11 until it enters the impellers 12, 13, if the impellers 12, 13 are symmetrically formed, no thrust force acts on a rotary shaft 16 since the pressure of the operating fluid at the inlet of the turbine is equal to each other. Moreover, no partition wall between the impellers 12, 13 and no seal are not only required, but only one nozzle 11 is sufficient, so that a cost is reduced. With clearance at two positions, the reduction of turbine efficiency is also halved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a back-to-back double flow radial turbine.

In the conventional double flow axial turbine of this kind, the first
As shown in the figure, nozzle blade groups of nozzle 3 and nozzle 4, which are separated by a partition wall 8, are provided corresponding to the two groups of rotor blades, impeller 1 and impeller 2, respectively. This (it is not necessary to insert the partition wall 8 between the nozzles 3 and 4), which not only increases the cost, but also requires that the throat areas of both the nozzles 3 and 4 be made the same.
A thrust will act on the rotating shaft 5.

Furthermore, in the case of a variable nozzle mechanism, a total of four side clearances are generated between the respective side walls 6 and 7 of the nozzle 3 and the nozzle 4 and the partition wall 8.

The efficiency of the radial turbine is significantly reduced due to the side clearance.

The purpose of the present invention is to focus on the above points, and (1) reduce the cost by halving the number of nozzle blades, and (2) eliminate the axial thrust force.
L. By providing a back-to-back type double flow radial turbine that (3) eliminates the need for a seal between two inlets and (4) simplifies the nozzle variable mechanism,
The feature is that in a back-to-back type double flow radial turbine in which one scroll is formed to surround the leading edge of two sets of rotor blades that are fixed back-to-back to the same rotating shaft, the scroll One set of nozzle blades is provided at the outlet nozzle portion and formed to have a blade span that simultaneously points toward the leading edges of the two sets of rotor blades.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing essential parts of a double flow radial turbine according to an embodiment of the present invention.

In the figure, 10 is a scroll, and 11 is a nozzle, which is fixed to a casing 15 at the exit of the scroll 10.

Reference numerals 12 and 13 denote impellers, which are two sets of rotor blades fixed back to back on the nine rotating shafts 16. The nozzle blade group constituting the nozzle 11 is formed to have a blade span that simultaneously points toward the leading edge of the rotor blade group of the impeller 12.13.

The functions and effects of the above configuration will be described.

The high-pressure working fluid is guided from the scroll 10 through the nozzle 11 to the di-impellers 12 and 13, and then to the casings 14 and 1.
It is discharged at 5.

Until the working fluid enters impellers 12 and 13.

It passes through a common scroll 10 and nozzle 11.

If the impellers 12 and 13 are made symmetrically, the pressures of the working fluid at the inlets of the impellers 12 and 13 are equal, so no thrust force acts on the one-rotation shaft 16.

Not only is there no need for a partition wall and a seal between the impeller 12 and the impeller 13, but only one nozzle 11 is required.
This reduces costs.

FIG. 3 is a sectional view showing the main parts of a double flow radial turbine according to another embodiment of the present invention.

In the figure, 10 is a scroll, 12.13 is an impeller, 14.15 is a casing, and 16 is a rotating shaft, which are the same members as in FIG. 2.

21 is a nozzle blade, 22 and 23 are side walls, and 24 is a nozzle blade drive shaft, which is rotatably fitted into the fitting hole 15a of the casing 15.

The functions and effects of the above configuration will be described.

It is well known that by making the nozzle blades 21 variable, the inlet pressure can be kept constant even if the flow rate of one working fluid changes, so that the turbine efficiency can be kept high.

In order to make the nozzle blade 21 variable, a certain clearance is required between it and the side wall 2223.

It has been shown that the working fluid passing through this clearance does no effective work, and thus turbine efficiency decreases approximately in proportion to the clearance.

In the conventional system, there are four clearances in total, but in the case of the present invention, there are only two clearances, so even if the clearance dimensions are the same, the reduction in turbine efficiency is halved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a conventional double-flow axial turbine, FIG. 2 is a cross-sectional view showing the main parts of a double-flow axial turbine according to an embodiment of the present invention, and FIG. FIG. 2 is a cross-sectional view showing the main parts of the double-throttle sial turbine according to the embodiment. 10...Scroll, 11...Nozzle, 12.1
3... Impeller, 14.15... Casing, 1
6... Rotating shaft, 21... Nozzle blade. Figure 71

Claims (1)

[Claims] 1. In a back-to-back type double flow radial turbine in which one scroll is formed so as to surround the leading edge of two sets of rotor blades that are fixed back-to-back to the same rotating shaft, a nozzle portion at the exit of the scroll is provided. A double flow radial turbine characterized by comprising a set of nozzle blade groups formed to have a blade width that simultaneously points the leading edges of the two sets of rotor blade groups.