JPS62101898A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To improve compression efficiency by accelerating slow speed gas near a wall surface by making gas, introduced from a high pressure side through a gas blowout hole arranged at a diffuser inlet, blow out in the direction of a main gas stream. CONSTITUTION:A gas blowout hole 10 is arranged as near to an impeller outlet of the inner diameter part of a diffuser wall on the side of a wall surface 8 as possible. Gas near the wall surface is accelerated in the radial direction by introducing high pressure gas from a discharge side of a gas passage 11 into the hole 10 and by blowing out the gas from the hole 10 in the direction of gas flow within the diffuser. Accordingly the gas speed distribution becomes more uniform and efficiency and pressure rise in that stage is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a centrifugal compressor, and in particular to a diffuser for a centrifugal compressor.

[Conventional technology]

FIG. 6 shows an assembled cross-sectional view of the centrifugal compressor, in which 1 indicates an intrusion, and 2 indicates a diffuser.

3 is a guide vane of the diffuser 2, 4 is a single chamber, and 5 is a main shaft. The gas is led from the suction chamber 6 to the impeller 1, through which it flows and is imparted with velocity energy.

Gas flows through the impeller 1 and part of its velocity energy is converted into pressure increase.

The velocity energy possessed by the gas at the impeller outlet is converted into pressure increase as the gas flows through the diffuser 2 and is decelerated. Figure 6 shows the case of a multi-stage compressor, in which the gas with increased pressure passes through the guide vanes 3 of the diffuser to the next stage.
The pressure is further increased in the first stage, and the pressure increases in sequence and is discharged from the discharge chamber 7 to the outside.

FIG. 7 is a partially enlarged view of the knife user 2 and the inner roller 1, and FIG. 8 shows the velocity distribution of gas on line A--A at the diffuser inlet.

At the part of the gas flow path in contact with the wall surface, the velocity decreases due to friction loss caused by the viscosity of the gas, so as shown in Figure 8,
It shows a mountain-shaped distribution with high velocity in the center of the channel.

The gas is sucked in almost axially at the inlet of the inlet (1), but at the inlet and outlet the gas changes direction in the radial direction and is subject to the action of centrifugal force. The peak of the velocity distribution is biased toward the wall surface 9 as shown in FIG.

[Problem that the invention seeks to solve]

As shown in Figure 8, if the speed is uneven along the width of the diffuser 2, even if the speed decreases near the wall during the process of deceleration and pressure rise, the speed will still be high in the center. There are problems such as a portion remaining, a large number of vortices being generated, a decrease in efficiency, and a decrease in pressure increase value.

Therefore, in order to improve efficiency and increase the value of pressure rise per stage, it is desirable to have a velocity distribution that is as uniform as possible in the width direction within the diffuser.

Since the unevenness of the flow worsens the velocity distribution, conventional methods have been used, such as bending the blades of the di-inverter 1 three-dimensionally to create a pressure distribution in which the pressure is higher from the wall surface 8 to the wall surface 9, thereby approaching a uniform flow. Efforts are being made. However, processing three-dimensionally curved blades is not easy to manufacture and increases costs.

Further, even if an attempt is made to improve the shape of the blade, it is not always possible to actually achieve a hydrodynamically ideal shape due to constraints on strength and processing.

[Failure to solve the problem]

In FIG. 1, a gas blowout hole 10 is provided as close as possible to the inlet outlet of the inner diameter part of the diffuser wall on the wall surface 8 side, and a gas blowout hole 10 is provided in this hole through a hole 11 to connect to the discharge side (one's own discharge side or one High pressure gas is introduced from the high pressure 1 (stage !I) of stage or higher, and is blown out from hole 10 in the direction of gas flow in the diffuser (direction of vA in Figure 4), accelerating the gas near the wall surface in the radial direction. do.

The blow-off holes 10 are provided so as to be inclined as much as possible in the gas flow direction at the inlet and outlet, as shown in FIG. 3, and in the radial direction as shown in FIG. 1 in cross section.

[Effect]

Suita hole 1 directs the slow gas near the wall to the main flow direction.
The speed is increased by the gas blown out from zero, producing a speed distribution as shown in FIG. 2, which is more uniform than the conventional speed distribution shown in FIG.

〔Example〕

In Figure 1, 1 is an in-crowd, 2 is a diffuser, and 3
is the guide vane of diffuser 2, 4 is a single chamber, 5 is the main shaft,
The above members are substantially the same as the members with the same reference numerals described in the prior art section.

Reference numeral 10 denotes a gas blowing hole, which is provided in the inner diameter part of the diffuser wall on the side of the wall surface 8, as close as possible to the outlet of the exhaust gas 1.

Further, the gas blowout hole 10 is inclined as much as possible in the direction of gas flow at the inlet outlet, as shown in FIG. 3, and in the radial direction as shown in FIG. 1 in cross section.

Reference numeral 11 indicates the discharge side of the gas blowout hole 10 (discharge side on the same stage).

or one or more stages of high pressure side), leading from the gas passage 11 to the gas blowing hole 10.

The released high-pressure gas flows in the gas flow direction (fourth direction) in the diffuser 2.
The gas is ejected in the direction of vA in the figure), accelerating the gas near the wall in the radial direction.

Figure 4 shows the velocity triangle of the gas flowing inside the impeller, and V
w is the peripheral speed of the impeller outer periphery, vG is the flow velocity of the gas with respect to the impeller, vA is the absolute velocity of the gas at the impeller outlet, that is, the inflow direction and inflow velocity with respect to the stationary diffuser, and the direction of the gas blowing hole 10 (Fig. 3) to match the direction of vA in Fig. 4.

In this way, the gas blowing out from the gas blowing hole 10 accelerates the slow gas near the wall in the direction of the mainstream flow,
The second speed distribution is more uniform than the conventional speed distribution shown in Figure 8.
This produces a velocity distribution as shown in the figure.

In addition, the gas blowing carpenter 0 is as shown in FIG.

They may be arranged in two rows in the radial direction.

〔Effect of the invention〕

Gas introduced from the high-pressure side is blown out from the gas blow-off hole provided at the diffuser inlet in the flow direction of the mainstream gas, and by accelerating the low-speed gas near the wall, it forms a high mountain in the center of the width in the diffuser. In addition, the velocity distribution of the gas is biased toward the discharge side.

As shown in FIG. 2, a uniform velocity distribution can be approached, thus improving the efficiency and pressure rise of the stage.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the vicinity of the Eibera and diffuser in an embodiment of the centrifugal compressor of the present invention, and Figure 2 is B of Figure 1.
Figure 3 is the CC cross section and arrow view of Figure 1, Figure 4 is the velocity triangle of the gas flowing inside the impeller, Figure 5 is the gas velocity distribution diagram at the -B cross section, Figure 5 is the gas blowout hole 2 Another example is shown arranged in columns. Figure 6 is an assembled sectional view showing the overall configuration of the centrifugal compressor;
The figure is a sectional view showing the vicinity of the impeller and diffuser in a conventional device, and FIG. 8 is a gas velocity distribution diagram in the AA cross section of FIG. 7. 1...in4, 2...diffuser. 3... Diffuser guide vane, 4... Vehicle compartment. 5...Main shaft, 10...Gas blowout hole. 11...Gas passage. Sub-Agent Patent Attorney Shige Okamoto Two extra prisoners 1st prisoner U - Ichiriki Susai 2nd Ward Figure 5

Claims (1)

[Claims] Gas blow-off holes are provided radially on the wall surface of the diffuser inlet of the centrifugal compressor, and a gas passage is provided that communicates the gas blow-off holes with the high-pressure side, and gas from the high-pressure side is directed from the gas blow-off holes into the main stream of the diffuser. A centrifugal compressor characterized by blowing out gas to make the velocity distribution of gas uniform at the diffuser inlet.