GB2333166A

GB2333166A - Hydraulic energy breaker

Info

Publication number: GB2333166A
Application number: GB9900002A
Authority: GB
Inventors: Giacomo Sciortino; Djahanchah Bamdad-Soufi
Original assignee: Delphi Automotive Systems France
Current assignee: Delphi Automotive Systems France
Priority date: 1998-01-07
Filing date: 1999-01-04
Publication date: 1999-07-14
Anticipated expiration: 2019-01-04
Also published as: GB9800181D0; GB2333166B; GB9900002D0

Abstract

A hydraulic energy breaker (10) for positioning in and substantially blocking a hydraulic conduit (24), the energy breaker comprising an insert (12) having a cylindrical wall (14) defining an inner section (16) which is closed at one end (18) and open at the other end (20); the closed end of the inner section being directed upstream and the open end directed downstream when positioned in the conduit; and a predetermined number of jet nozzles (22) formed in the cylindrical wall to allow fluid flow into the inner section and then out through the open end. The breaker is applicable to pumps, in particular pumps for vehicle steering systems.

Description

HYDRAULIC ENERGY BREAKER Technical Field The present invention relates to a hydraulic energy breaker and in particular to such an energy breaker which can be used for suppressing noise generated in a fluid flow path, such as in a hydraulic pump.

Background of the Invention In any hydraulic conduit pressure fluctuations may have their origin in the following functional properties of the conduit: 1. Change of magnitude of velocity as they occur in diffusers, spatial changes of cross-section, sudden contractions and/or expansions.

2. Change of flow direction in elbows, bends, cascades.

3. Change of flow path as in by-pass lines, manifolds, junctions, etc.

4. Temporal change of conduit such as sudden temporal enlargements or contractions as in hydraulic control devices.

5. Change of energy forms as they may occur as shaft power is converted into flow energy or flow energy into shaft energy, or by any other means of energy conversion.

The disturbances generated in the above instances are generally damped out in a straight conduit attached to the disturbance generating mechanism, if the conduit has enough length and a steady flow free of disturbances is achieved. However, along this path the disturbance may be transmitted to neighbouring machine parts and radiated as noise or damage parts of the machinery by inducing vibrations. In these cases the flow is conveyed to an appropriate suppression system.

Summarv of the Invention It is an object of the present invention to provide an improved hydraulic energy breaker.

A hydraulic energy breaker in accordance with the present invention, for positioning in and substantially blocking a hydraulic conduit, comprises an insert having a cylindrical wall defining an inner section which is closed at one end and open at the other end; the closed end of the inner section being directed upstream and the open end directed downstream when positioned in the conduit; and a predetermined number of jet nozzles formed in the cylindrical wall to allow fluid flow into the inner section and then out through the open end; the insert having a predetermined axial length and diameter, and the jet nozzles having a predetermined diameter, for energy dissipation and noise reduction in the fluid flowing in the conduit.

In applications, as for example, in hydraulic pumps, shaft energy is transferred to the fluid. Part of this mechanical shaft energy is transferred to disturbance flow energy. In order to suppress this disturbance energy, it must first be converted into kinetic energy, thus, the flow cross-section must experience a contraction. Subsequently, the fluid will flow into a larger cross-section, preferably a sudden spatial enlargement where the flow will form a jet, with intense turbulence being generated at the jet boundaries. Thus the flow will get "slowed down". As a result of this process, a certain amount of kinetic energy is transformed into thermal energy and no longer exists in the form of unwanted pressure fluctuations. The remaining portion of kinetic energy is reconverted into fluctuation-free flow energy. As mentioned above, the very process of turbulence formation is a source of pressure fluctuation.

Apart from the energy dissipation by the means described, the present invention also aims to shift the frequency of these pressure fluctuations into a range where they are not acoustically objectionable or where no structural damage is to be expected. This can be achieved by dividing the total cross-section into a number of smaller cross-sections, thereby increasing the frequencies of the fluctuations.

The present invention is realised by diverting the fluid flow, under a high internal pressure, onto the inner section of a cylindrical insert in the form of a large number of extremely thin jets.

The thin jets impinge on each other in the inner section of the insert with a high velocity. As a consequence of this controlled process, the fluid jets are "slowed down", their kinetic energy is transformed into the energy of a turbulent motion having a desired frequency spectrum and eventually dissipated into heat.

In applications dealing with reasonably high hydraulic pressures, this concept design of "energy breaker" can also be formed as an assembly of two or more "energy breaker elements" either of the same or different characteristics, as required.

The present invention has particular application in centrifugal hydraulic pumps of gear, or vane, axial-piston types, especially pumps for motor vehicle steering systems. The aim is to reduce noise in the pumped fluid.

Brief Description of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a hydraulic energy breaker in accordance with the present invention positioned in a hydraulic conduit; Figure 2 is a cross-sectional view of the hydraulic energy breaker of Figure 1; Figure 3 is a cross-sectional view of a second embodiment of hydraulic energy breaker in accordance with the present invention; Figure 4 is a cross-sectional view of a third embodiment of hydraulic energy breaker in accordance with the present invention positioned in a hydraulic conduit; Figure 5 is a cross-sectional view of a fourth embodiment of hydraulic energy breaker in accordance with the present invention positioned in a hydraulic conduit; and Figure 6 is a cross-section view of a hydraulic fluid pump incorporating the hydraulic energy breaker of Figure 1.

Description of the Preferred Embodiment Referring to Figures 1 and 2, the hydraulic energy breaker 10 in accordance with the present invention is in the form of an insert 12 which comprises a cylindrical wall 14 defining an inner section 16. The insert 12 has an end wall 18 at one end which closes the inner section 16. The other end 20 of the insert 12 is open to the inner section 16. A number of apertures or jet nozzles 22 are formed in the cylindrical wall 14 which open into the inner section 16. The cylindrical wall 14 is preferably substantially circular in cross-section.

The energy breaker 10 is positioned inside a hydraulic conduit 24 through which fluid can flow in a direction X. The insert 12 has an annular wall 26 at the open end 20 of the insert which is integral with the cylindrical wall 14. The annular wall 26 is secured to the inner surface 28 of the conduit 24 with the end wall 18 of the insert 12 directed towards the upstream end of the conduit. The energy breaker 10 substantially blocks the conduit 24, except for the jet nozzles 22. The jet nozzles 22 allow fluid in the conduit 24 to pass from the outer surface of the cylindrical wall 14 into the inner section 16 as the fluid flows in the direction X through the conduit.

Using the following calculations, where i, j, and k, are predetermined constants in the ranges indicated, the energy breaker 10 can be tuned to provide the required energy dissipation and noise reduction in the fluid flowing through the conduit 24.

1 # i # 0.1; i = Db Dc, 1 # k # 0.1; k = Dj Db 1 # j # 0.1; j = Dj H 1 # n # 1000; where Din : Hydraulic inlet diameter of the conduit 24.

DCout: Hydraulic outlet diameter of the conduit 24.

Db : Outer diameter of the energy breaker 10.

H : Axial length of the energy breaker 10.

Diameter of the jet nozzles 22. n : Number of jet nozzles 22.

The above assumes that the inlet diameter and the outlet diameter of the conduit 24 are the same.

Referring to Figure 3, the second embodiment of hydraulic energy breaker 100 is similar to the energy breaker shown in Figures 1 and 2 except that the cylindrical wall and end wall of the insert 112 are curved to form an arcuate or semi-spherical wall 114. Other features of the energy breaker 100 are substantially the same as the energy breaker 10 of Figures 1 and 2 and have been given the same reference numeral but with the prefix 100.

Referring to Figure 4, the third embodiment of hydraulic energy breaker 200 comprises a number of inserts 12 as shown in Figures 1 and 2, with the inserts positioned in series in the conduit 24. Referring to Figure 5, the fourth embodiment of hydraulic energy breaker 300 comprises the insert 12 as shown in Figures 1 and 2, with an additional, substantially identical but smaller, insert 12' positioned in the inner section 16 as shown.

Referring to Figure 6, the hydraulic energy breaker 10 of Figures 1 and 2 is shown in position in a fluid conduit 30 in a hydraulic pump 32. The conduit 30 has a fluid inlet 34 and a fluid outlet 36, and the insert 12 of the energy breaker 10 is positioned with the open end 20 adjacent the fluid outlet 36. In this arrangement, fluid flow from the inlet 34 to the outlet 36 is only possible by way of the jet nozzles 22 and the inner section 16 of the insert.

Summarising, the present invention is a cylindrical insert in a hydraulic conduit for reducing and/or frequency shifting of pressure fluctuations (whose frequencies are harmonics to the speed of revolution of a pump shaft when used in a pump) by conveying fluid flow into the inner section of the insert by way of the jet nozzles.

Claims

1. A hydraulic energy breaker for positioning in and substantially blocking a hydraulic conduit, the energy breaker comprising an insert having a cylindrical wall defining an inner section which is closed at one end and open at the other end; the closed end of the inner section being directed upstream and the open end directed downstream when positioned in the conduit; and a predetermined number of jet nozzles formed in the cylindrical wall to allow fluid flow into the inner section and then out through the open end; the insert having a predetermined axial length and diameter, and the jet nozzles having a predetermined diameter, for energy dissipation and noise reduction in the fluid flowing in the conduit.

2. A hydraulic energy breaker as claimed in Claim 1, wherein the cylindrical wall has a substantially circular cross-section.

3. A hydraulic energy breaker as claimed in Claim 1, wherein the cylindrical wall is arcuate or semi-spherical in shape.

4. A hydraulic energy breaker as claimed in any one of Claims 1 to 3 comprising a number of inserts positioned in series.

5. A hydraulic energy breaker as claimed in any one of Claims 1 to 4, wherein the insert has an annular wall at the open end of the inner section which is integral with the cylindrical wall.

6. A hydraulic energy breaker substantially as herein described with reference to, and as shown in, the accompanying drawings.

7. A hydraulic pump comprising a fluid conduit having a fluid inlet and a fluid outlet; and a hydraulic energy breaker as claimed in any one of Claims 1 to 6 positioned in the fluid conduit such that fluid flow from the fluid inlet to the fluid outlet is only by way of the jet nozzles and the inner section of the insert.

8. A hydraulic pump substantially as herein described with reference to, and as shown in, Figure 6 of the accompanying drawings.