Turbomachine

Details Turbomachine Turbomachine

1993-08-26

1995-10-17

Kwon, John T.

Rotary kinetic fluid motors or pumps

With passage in blade, vane, shaft or rotary distributor...

415116, F01D 1100

Patent

active

054584574

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a turbomachine and, more particularly, to a turbomachine which is designed to prevent conditions giving rise to positively-sloped head-capacity characteristics, which would otherwise be observed in the head-capacity curve while the machine operates below maximum capacity, or which exhibits the positively-sloped head-capacity characteristics only over a portion of its capacity, whereby the turbomachine has a stable operation.
2. Description of the Related Art
FIGS. 3(a) and 3(c) each show an impeller part of a respective conventional turbomachine. FIG. 3(a) shows the impeller part of a turbomachine having an open impeller without a front shroud, while FIG. 3(c) shows the impeller part of the turbomachine having a closed impeller with a front shroud. FIGS. 3(b) and 3(d) are sectional views taken along lines C--C and D--D in FIGS. 3(a) and 3(c), respectively. As is illustrated in the figures, as an impeller 1 rotates inside a casing 3 about an axis 2 of rotation, a fluid is sucked into the casing 3 from a suction port (not shown) and is discharged into a discharge port (not shown).
In the conventional turbomachinery of the type described above, a large-scale separation of flow occurs due to an unstable high-loss fluid, that is, a low-momentum fluid, on the blade surface, the casing and/or the shroud. As a result, a head-capacity curve having a positive slope appears in a partial capacity range, as shown by the broken line 9 in FIG. 6. Such positively-sloped characteristics of the head-capacity curve are also known as a stall phenomenon, which may induce surge, that is, self-induced vibration of a turbomachine piping system, and which may also cause vibration and noise and damage the apparatus. Thus, the stall phenomenon is a serious problem to be solved in obtaining a stable operation of turbomachinery.
The means for solving such a problem may be roughly divided into passive means that are not supplied with energy from the outside of the turbomachine, and active means that are supplied with some energy from the outside of the turbomachine.
Known passive means include casing treatment in which grooves are provided in the inner wall of the casing, and an annular passage with straightening vanes provided inside a part of the casing at the impeller inlet part (see the teaching material for the 181st course sponsored by the Kansai Branch of the Japan Society of Mechanical Engineers, pp. 45-56). These means suffer, however, from the problem that although the effectiveness of the turbomachinery during operation in a partial capacity range is enhanced, the efficiency during the normal operation is accordingly lower.
Further, a means which bypasses fluid from the discharge side toward the inlet side during operation in the partial capacity range is widely employed. However, this means increases the actual capacity of the fluid flowing through the turbomachine, and it inevitably causes a marked reduction in the pump head of the turbomachine. In addition, since a large amount of fluid flows back through the bypass, a great deal of power is consumed disadvantageously.
On the other hand, the conventional active means may be roughly divided into the following four types: blade surface, the casing and/or the shroud; in the direction of the impeller rotation, to thereby prevent blade stalling; and unstable fluid oscillation that appears in the flow field before stalling occurs.
As one example of the means (1), Japanese Patent Application Public Disclosure No. 55-35173 (1980) discloses a method in which part of the high-pressure side fluid is introduced to the tip of the impeller and/or the area inbetween each pair of adjacent blades in the form of a high-speed jet. According to this literature, the jet may be injected in the radial direction, the direction of rotation of the impeller or the direction counter to the impeller rotation, and this literature claims that the jet is equally effective when injected in any of these three direction

REFERENCES:
patent: 3462071 (1969-08-01), Garve
patent: 3507603 (1970-04-01), Von Widdern
patent: 4732531 (1988-03-01), Minoda et al.
patent: 5154570 (1992-10-01), Yoshikawa
Takata, "The Newest Fluid Technology of Turbomachinery and the Topics", Stalling Control Technology of Compressors, Japan Machinery Society, May 16, 1991.
Kaneko et al., "The Improvements, of the Unstable Characteristics of the Low Capactiy Area of High Specific Speed Diagonal-Flow Fan by Front Annular by Wing", Feb. 1992, N. Rajaratnam, Turblent Tests, Trans Nomura Yasumasa, Morikita Shuppan, Inc.

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