JPS6128799A - Centrifugal compressor - Google Patents

Abstract

PURPOSE:To ensure high efficiency in a wide range of the rate of flow by furnishing a main and a sub-scroll chamber in a compressor housing along the diffuser part of a centrifugal compressor, and by installing an opening/closing valve for adjustment of rate of flow at the outlet from the sub-scroll chamber. CONSTITUTION:A main scroll chamber 16 and a sub-scroll chamber 17 are provided in the compressor housing 15. Division is made by a partition wall 15A having a communication hole 18, and an opening/closing valve 19 is installed in the neighborhood of the outlet 17A from said sub-scroll chamber 17. This valve 19 is closed in the minor flow range so as to have the compressed air being fed only out of the main scroll chamber, while it is opened in the major flow range to allow both chambers to feed compressed air. This ensures that the compressed air is fed with good effectiveness in a wide range of the rate of flow.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a centrifugal compressor, and particularly to a centrifugal compressor having a structure in which air sent out by a compressor impeller is guided to a scroll part via a diffuser part. This is an attempt to expand.

[Prior art]

Conventionally, a centrifugal compressor designed for this type of operation and operating range has been known, for example, as shown in FIG. 1, and this example is disclosed in Japanese Patent Application Laid-open No. 13232/1983. In addition, this example is an example of a compressor for a turbo supercharger, and 1 is a turbine rotor 2 and a compressor impeller attached coaxially via a rotating shaft 3, 4 is a turbine housing, and 5
6 is a compressor housing, and 6 is a bearing housing to which these housings 4 and 5 are attached and is further provided with a bearing (not shown).

Therefore, the air inlet port 7 of the compressor housing 5
The air flowing into the impeller l from the impeller l is guided to the impeller l Karatif user part 8, where the velocity energy is converted into pressure energy and further passed from the scroll part 9 to the compressor outlet 1.
sent to 0.

11 is a housing wall 5 forming the diffuser part 8
A plurality of openings are formed near the impeller 1 outlet, and a dividing plate 13 rotatably held by a retainer 12 is provided on the outside of the housing wall 5A. The plurality of drilled openings 14 and the opening 11 are made to coincide with each other depending on the rotational position of the partition plate 13, so that the diffuser portion 8 can communicate with the outside world via the partition plate 13. I am doing it.

In a turbocharger having a centrifugal compressor configured in this way, when the engine is in a low speed range, the supporting plate 1
3 closes the opening +1, compressing only the air flowing in from the inlet 7, and supplying supercharging pressure to the engine from the outlet 10 via the scroll 9. When the rotational speed of the engine exceeds a predetermined value, the splitting plate 13 is rotated again to open both openings 11 and 14, thereby increasing the compressed air flow rate.

However, in such a centrifugal compressor, the flow velocity when air is introduced into the high-speed side of the diffuser section 8 where the opening 11 is provided is a high speed almost close to the speed of sound;
In response to such a high-speed swirling flow, outside air is sucked in from the inlet side of the diffuser section 8, so the fluid loss that occurs in the diffuser section 8 due to the mixing of both slow-speed flows is large, and furthermore, velocity energy is converted into pressure energy. Since the conversion pressure recovery rate is impaired, compression efficiency in a large flow rate region is significantly deteriorated, resulting in a decrease in engine torque.

〔the purpose〕

In view of these problems, the purpose of the present invention is to maintain high efficiency over a wide range from small flow areas to large flow areas, and when applied to engine turbochargers, it is possible to maintain high efficiency from the low speed area to the high flow rate area. It is an object of the present invention to provide a centrifugal compressor that can maintain appropriate supercharging up to a high speed range and improve engine torque.

〔composition〕

In order to achieve such an object, the present invention includes a main scroll chamber provided around the circumference so as to be continuous with the outlet of the diffuser section, and a main scroll chamber provided in parallel with the main scroll chamber and communicating with the main scroll chamber through a circumferential communication hole. A sub-scroll chamber is formed in the compressor housing, and an on-off valve that can adjust the flow rate is provided at the outlet of the sub-scroll chamber, and in the low flow range, the on-off valve is closed and only the main scroll chamber side is closed. The compressed air is sent out through the main scroll chamber and the on-off valve is opened as the flow rate reaches a large flow area, so that the compressed air is sent out from both the main scroll chamber and the sub-scroll chamber.

〔Example〕

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

2 and 3 show one embodiment of the invention. Here, 15 is a compressor housing, and 16 and 17 are a main scroll chamber and a sub scroll chamber formed in this compressor housing 15.

The main scroll chamber 16 and the sub-scroll chamber 17 are separated by a circumferential partition wall 15A, and the partition wall 15A is further provided with a communication hole 18 formed in the circumferential direction.

18 shown in Fig. 3 is the exit 17A of the sub scroll *17
This is an on-off valve installed nearby, which is shown in the open state in this example, and by rotating the cock-shaped valve body 19A in the direction of the arrow, the valve 19 can be throttled and further brought into the closed state.

In the centrifugal compressor configured in this way, when the engine is in a small flow rate region, that is, when the engine is in a low speed region when applied to an exhaust turbo supercharger, the on-off valve 18 is kept closed, and the sub scroll chamber is closed. is designated as a dead area. Note that in the present invention, the flow rate in the main scroll chamber 1B is set to correspond to a small flow rate type.

In such a state, compressed air can be sent out from the main scroll chamber 1θ with optimal efficiency.

The relationship between the flow rate of air delivered from the compressor and the efficiency at this time is shown by a solid line S in FIG. In addition, such a flow rate -
What influences the efficiency shown by the efficiency characteristic curve group is the loss in the scroll section, and the main one is the mixing loss resulting from the difference between the flow velocity at the diffuser outlet section 8A and the average flow velocity of the entire scroll section.

Therefore, by increasing the capacity of the scroll portion as the flow rate obtained from the impeller 1 increases, it is possible to maintain a high efficiency state in which the above-mentioned loss is kept to a minimum. In this example, as the rotation of the centrifugal compressor increases, the degree of opening of the on-off valve 18 is gradually increased from closed, and a corresponding air flow rate is obtained from both the main scroll chamber 1B and the sub-scroll chamber 17. It should be done like this,
Since the air flow rate which cannot be handled by the main scroll chamber 18 alone is led to the sub scroll chamber 7 via the communication hole 18, the air from this side can be sent out from its outlet 17A.

Thus, when the flow rate is large, by keeping the on-off valve 18 fully open, it is possible to maintain efficiency equivalent to that of a centrifugal compressor having a large flow rate scroll portion. Fourth
In the figure, a curve M indicated by a broken line is a characteristic curve for a medium-capacity type centrifugal compressor, and a curve H indicated by a dashed-dotted line is that for a large-capacity type. Therefore, according to the present invention, these curves S, M, and The characteristics shown by the envelope curve E of H can be maintained.

Note that it is desirable that the communication hole 18 be provided over the entire circumference at the same radial position as shown in FIG.
It goes without saying that even if there is some deviation in the radial position due to design considerations, or if it does not cover the entire circumference, a certain effect can still be obtained.

FIG. 5 shows another embodiment of the present invention, in which the swirling flow in the main scroll chamber 16 is prevented from being diverted to the sub-scroll chamber 17 side due to its centrifugal force. Therefore, the communication hole 18 has an inclination as shown in the figure, and the hole 18 has an opening at a position with a large radius on the main scroll chamber 181 side and a position with a small radius on the side of the sub-scroll chamber 17. . In this way, the inner circumferential edge 18A of the hole 18 on the main scroll chamber 18 side is made to protrude in the radial direction from the outer circumferential edge 18B on the sub scroll chamber 17 side by a dimension Δγ. Here, Δγ≧0° In the centrifugal compressor configured in this way, when the on-off valve is fully closed, the swirling flow on the main scroll chamber 18 side flows into the dead area formed in the sub scroll chamber 17 due to its centrifugal force. This makes it possible to further improve efficiency in a small flow rate region.

〔effect〕

As explained above, according to the present invention, the main scroll chamber provided around the outlet of the diffuser section and the sub-scroll chamber having the communication hole in the circumferential direction between the main scroll chamber and the main scroll chamber are provided in the compressor housing. An on-off valve that can adjust the flow rate is provided at the outlet of the sub-scroll chamber, and in small flow areas, the on-off valve is closed to make the sub-scroll chamber a dead area and compress only from the main scroll chamber. In the large flow area, the on-off valve is opened and compressed air is sent out from both the main scroll chamber and the sub-scroll chamber, allowing for a wide range of flow from small flow areas to large flow areas. When applied to an exhaust turbo supercharger, it can effectively supply supercharged air to the engine over a wide range of engine speeds, from low speed to high speed, and increase the engine torque. can be improved. Furthermore, in the second embodiment, the compressed air generation efficiency can be particularly improved in the small flow region.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the configuration of a conventional exhaust turbo supercharger and its centrifugal pressure rice machine, FIG. 2 is a cross-sectional view showing an example of the configuration of the centrifugal compressor of the present invention, and FIG. 3 is one of the configurations. FIG. 4 is a characteristic curve diagram showing the relationship between flow rate and efficiency in a centrifugal compressor, and FIG. 5 is a sectional view showing the configuration of another embodiment of the present invention. 1... Compressor impeller. 2...Turbine rotor. 3...Rotation axis. 4... Turbine housing, 5... Compressor housing, 5A... Wall, 6... Bearing housing, 7... Inlet, 8... Diffuser part, 8A... Outlet part, 9... ... Scroll part, 10... Outlet, 11... Opening, 12... Retainer, 13... Division plate, 14... Opening, X5... Compressor housing, 15A... Partition wall , 1θ...Main scroll chamber, 17...Sub-scroll chamber, 17A...Outlet, 18...Communication hole, 18...Opening/closing valve, 111A...Valve body. Figure 1

Claims (1)

[Claims] In a centrifugal compressor that sends compressed air from a compressor impeller through a diffuser section and a scroll chamber, a main scroll chamber provided around an outlet of the diffuser section;
A sub-scroll chamber is provided in parallel with the main scroll chamber and has a communication hole in the circumferential direction between the main scroll chamber and the main scroll chamber, and a sub-scroll chamber is provided at the outlet of the sub-scroll chamber, and the compressed air from the compressor impeller has a small flow rate. A centrifugal compressor comprising an on-off valve that can be controlled to be closed at times and opened when the compressed air has a large flow rate.