JP7490945B2 - Ejector - Google Patents

Description

The present invention relates to an ejector that can reduce friction loss caused by the velocity gradient when the driving flow and the suction flow meet.

For example, some circuits that circulate refrigerant include an ejector. The ejector is configured with a nozzle section that ejects a driving fluid from an orifice at the tip, a main body section that is arranged to surround the nozzle section and has a hollow section at a position that is an extension of the nozzle section's orifice, and a suction path that is connected to open into the hollow section of the main body section. In this ejector, when the refrigerant is ejected as a driving fluid from the orifice of the nozzle section, the external refrigerant is sucked into the hollow section of the main body section through the suction path, and the sucked suction fluid and the driving fluid are mixed, then pressurized in a diffuser and ejected from a discharge port (see, for example, Patent Document 1).

JP 2008-64021 A

The driving flow ejected from the nozzle is supersonic. On the other hand, the suction flow flowing in through the suction path is once decelerated in the suction passage area formed by the outer wall of the nozzle and the inner wall of the main body from the side surface of the base end of the main body, and the asymmetry of the flow with respect to the central axis of the main body caused by the flowing in from the side surface of the base end of the main body is mitigated. As a result, the flow velocity of the suction flow is much slower than that of the driving flow, and when the suction flow joins the driving flow near the tip opening of the nozzle, the velocity gradient at the contact surface between the suction flow and the driving flow becomes large, and there is a problem in that friction loss increases due to a shear force proportional to this velocity gradient.

The present invention has been made in consideration of the above, and aims to provide an ejector that can reduce friction loss caused by the velocity gradient when the driving flow and the suction flow meet.

In order to achieve the above object, the present invention is an ejector having a cylindrical nozzle with a hollow nozzle hole formed therein and from which a driving flow is ejected from a tip opening, a suction passage section around the nozzle for introducing a suction flow from the upstream side of the nozzle, and a junction section where the driving flow and the suction flow join, the cylindrical main body section being arranged so that its central axis is the same as the central axis of the cylindrical nozzle, and the suction flow is sucked into the main body section through the suction passage section by ejecting the driving flow from the tip opening of the nozzle, and the driving flow and the suction flow join at the junction section, characterized in that the main body section is formed with an acceleration section whose inner wall diameter monotonically decreases from a predetermined distance upstream of the tip opening of the nozzle to an intermediate position of the junction section, and a throttle section that is continuous with the acceleration section and linearly decreases the inner wall diameter toward the downstream end of the junction section to accelerate the suction flow.

The present invention is also characterized in that, in the above invention, the inner wall diameter of the acceleration section smoothly and monotonically decreases, and the inner wall of the acceleration section and the inner wall of the throttle section are formed so that their tangential directions coincide.

The present invention is also characterized in that in the above invention, the aperture angle of the aperture section is 0° to 3°.

The present invention can reduce friction loss due to the velocity gradient when the driving flow and the suction flow meet.

FIG. 1 is a cross-sectional side view showing a schematic internal structure of an ejector according to an embodiment of the present invention. FIG. 2 is a diagram showing the throttle angle dependency of the suction flow rate ratio with respect to the suction flow rate when the throttle angle is 0°.

Below, a preferred embodiment of the ejector according to the present invention will be described in detail with reference to the attached drawings.

1 is a cross-sectional side view showing a schematic internal structure of an ejector 1 according to an embodiment of the present invention. The ejector 1 includes a nozzle 10 in which a nozzle hole 11 is formed and a driving flow is ejected from a tip opening 11a, and a main body 20 arranged to form a suction passage 21 for the suction flow around the nozzle 10 and provided with a confluence 22 for the driving flow and the suction flow at a portion on an extension of the tip opening 11a. The ejector 1 ejects the driving flow from the tip opening 11a to suck the suction flow into the main body 20 through the suction passage 21, and merges the driving flow and the suction flow at the confluence 22. The driving flow and the suction flow that have merged at the confluence 22 are mixed in a mixing section 23 with a constant inner wall diameter, and are pressurized and discharged in a diffuser section 24 with a gradually expanding inner wall diameter. The nozzle 10 and the main body 20 are formed in a tubular shape with respect to the central axis L.

The nozzle 10 is a tapered cylinder with a nozzle hole 11 in the center. The nozzle hole 11 is formed so that its central axis coincides with the central axis L of the nozzle 10, and reduces the pressure of the high-pressure driving flow passing through it and ejects it from the tip opening 11a. The nozzle hole 11 has a shape in which the cross-sectional area gradually decreases and then gradually increases toward the tip opening 11a, and has a throat 11b where the cross-sectional area is the smallest. A slightly wide driving flow chamber 12a is provided at the base end side of the nozzle hole 11. The driving flow is introduced into the driving flow chamber 12a from the driving flow tube 12 that protrudes to the side. The base end side of the driving flow chamber 12a is blocked by a block 12b.

The main body 20 is cylindrical with a hollow center and a circular cross section. The hollow portion of the main body 20 is provided with a suction passage 21, a junction 22, a mixing portion 23, and a diffuser 24. The suction passage 21 is a portion with an inner diameter larger than the outer diameter of the nozzle 10, and is provided at the base end of the main body 20. In other words, the tapered cylindrical area in the gap between the periphery of the nozzle 10 and the main body 20 forms the suction passage 21.

The confluence 22 is a portion that is continuous with the tip of the suction passage 21 and is formed so that the inner diameter gradually decreases monotonically toward the tip. The confluence 22 has an acceleration section 41 on the base end side and a narrowing section 42 on the tip end side. The upstream position P1 on the base end side of the acceleration section 41 may be the same as the tip opening position P of the nozzle 10, but in FIG. 1, it is an upstream position that is downstream of the suction passage 21 and shifted upstream from the tip opening position P of the nozzle 10 by a predetermined upstream distance d1 (d1≧0). The acceleration section 41 is between the upstream position P1 and the intermediate position P2 of the confluence 22, and the inner wall diameter decreases monotonically toward the downstream side to accelerate the suction flow. For example, the inner wall diameter of the acceleration section 41 decreases monotonically in a smooth curved line. The intermediate position P2 is a position shifted downstream by a predetermined downstream distance d2 from the tip opening position P of the nozzle 10.

The throttle section 42 accelerates the suction flow by linearly decreasing the inner wall diameter from the intermediate position P2 toward the downstream position P3, which is the downstream end of the confluence section 22 and the upstream end of the mixing section 23. For example, the throttle angle θ of the throttle section 42, that is, the throttle angle θ, which is the cross-sectional opening angle toward the upstream side with respect to the central axis L, is 0° to 3°. As described above, the inner wall of the acceleration section 41 is formed so that the inner wall diameter smoothly and monotonically decreases and the inner wall of the acceleration section 41 and the inner wall of the throttle section 42 are tangent to each other.

Between the acceleration section 41 and the nozzle 10, an acceleration region E is formed in which the cross-sectional area perpendicular to the flow direction of the suction flow F2 monotonically decreases in the flow direction of the suction flow F2, which flows between the inner wall of the acceleration section 41 and the outer wall of the nozzle 10. As a result, the suction flow F2 is accelerated in the acceleration region E before merging with the driving flow F1, and the velocity gradient at the time when the driving flow F1 and the suction flow F2 merge can be reduced, thereby reducing friction loss.

The throttle section 42 also accelerates the suction flow F2 to reduce friction loss at the contact surface between the driving flow F1 and the suction flow F2, and shortens the length to the mixing section 23 of the confluence section 22. By shortening the length to the mixing section 23, the contact area between the driving flow F1 and the suction flow F2 can be reduced, further reducing friction loss.

The mixing section 23 is connected to the tip of the confluence section 22 and has a uniform inner diameter that is larger than the inner diameter of the tip of the nozzle 10. The diffuser section 24 is connected to the tip of the mixing section 23 and is tapered so that the inner diameter gradually increases toward the tip, and pressurizes the fluid mixed in the mixing section 23. The pressurized fluid is then discharged to the outside.

The base end of the main body 20 is provided with a suction pipe 30 that protrudes to the side. The suction pipe 30 is connected to the suction passage 21, and a low-pressure suction flow is introduced into the suction passage 21. The base end of the suction passage 21 is blocked by a stepped wall of the nozzle body 11c that is integrally formed with the nozzle 10. The suction passage 21 temporarily slows down the suction flow introduced from the side of the main body 20, and mitigates the asymmetric flow with respect to the central axis L of the main body 20 caused by the flow entering from the side of the side of the main body 20.

Here, FIG. 2 is a diagram showing the throttle angle dependency of the suction flow rate ratio R of the throttle angle θ relative to the suction flow rate when the throttle angle θ is 0°. As shown in FIG. 2, the suction flow rate ratio is 1 or more when the throttle angle θ is between 0° and 3°, and is less than 1 when the throttle angle θ exceeds 3°. Therefore, as described above, the effect of improving the suction flow rate ratio can be obtained by setting the throttle angle θ to 0° to 3°. Furthermore, when the throttle angle θ is 1.5°, the suction flow rate ratio R is maximum value (1.05), and it is preferable to set the throttle angle θ to 1.5°.

A needle that can advance and retreat along the central axis L may be provided at the center of the nozzle 10. The needle adjusts the flow rate of the driving flow by changing the cross-sectional area through which the driving flow passes, which is determined by the gap between the outer circumferential surface of the needle and the inner circumferential surface of the nozzle hole 11.

In addition, the acceleration section 41, the throttling section 42, the mixing section 23, and the diffuser section 24 of the main body 20 may be formed as separate components that are then joined together.

When the length of the acceleration section 41 and the throttling section 42 is shortened to accelerate the suction flow, the contact area becomes smaller and the friction loss becomes smaller. However, when the length of the acceleration section 41 and the throttling section 42 is lengthened, the contact area becomes larger and the loss due to contact friction increases. Therefore, it is necessary to perform optimization according to the operating conditions of the ejector 1.

Furthermore, when the flow velocity of the suction flow reaches the sonic speed in the region where the gap between the acceleration section 41 and the nozzle 10 is narrowest, a critical flow occurs, causing blockage of the suction flow and preventing an increase in the suction flow rate. For this reason, it is necessary to determine the length of the acceleration section 41 and the nozzle 10 so that the necessary suction flow rate required by the operating conditions can be secured.

Note that the configurations illustrated in the above embodiments and variations are merely functional schematics, and do not necessarily have to be physically configured as illustrated. In other words, the form of distribution and integration of each device and component is not limited to that illustrated, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various usage conditions, etc.

REFERENCE SIGNS LIST 1 Ejector 10 Nozzle 11 Nozzle hole 11a Tip opening 11b Throat 11c Nozzle body 12 Driving flow tube 12a Driving flow chamber 12b Block 20 Main body 21 Suction passage 22 Confluence 23 Mixing section 24 Diffuser 30 Suction pipe 41 Acceleration section 42 Throttle section d1 Predetermined upstream distance d2 Predetermined downstream distance E Acceleration region F1 Driving flow F2 Suction flow L Central axis P Tip opening position P1 Upstream position P2 Intermediate position P3 Downstream position R Suction flow rate ratio θ Throttle angle

Claims (3)

a tapered cylindrical nozzle having a hollow nozzle hole formed therein and from which a driving flow is ejected from a tip opening;
a suction passage section that introduces a suction flow from the upstream side of the nozzle around the nozzle, and a confluence section that is continuous with the suction passage section and where the driving flow and the suction flow are confluent, the tubular main body section being disposed so that a central axis of the tubular nozzle is aligned;
an ejector having a nozzle tip opening, which ejects the driving flow from the nozzle tip opening to suck the suction flow into the main body through the suction passage, and merges the driving flow and the suction flow at the merging portion,
The main body portion includes:
an acceleration section that forms an acceleration region in which an inner wall diameter monotonically decreases in a curved line from a predetermined distance upstream of a tip opening of the nozzle to an intermediate position of the confluence section, and a distance between an outer wall of the nozzle and an inner wall of the acceleration section monotonically decreases from the predetermined distance upstream to the tip opening of the nozzle;
a throttle section that is continuous with the acceleration section and has an inner wall diameter that linearly decreases toward a downstream end of the confluence section to accelerate the suction flow;
The ejector is characterized in that: The ejector according to claim 1, characterized in that the inner wall of the acceleration section and the inner wall of the throttling section are formed so that their tangent directions coincide. The ejector according to claim 1 or 2, characterized in that the aperture angle of the aperture portion is 0° to 3°.

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