DK142002B - Muffler at the intake side of a compressor with several annular damping elements. - Google Patents

Description

(11) PUBLICATION 142002 (la |) DENMARK “·« F 04 D 23/66 X / p oi n § (21) Application No. 5 ^ 77 / ^ 6 (22) Filed on 6 Dec. 1976 (23) Race day 6. deC. 1976 (44) The application presented and in. 1 Qftf) the petition published on “Ufe *

Dl RECTORATE FOR -. J

PATENT AND TRADE MARKET (30) Pnontet requested from dm,

Dec 11 1975, 16088/75, CH

(71) BBC AKTIENGESELLSCHAFT BROWN BOVERI & CIE., Baden, CH.

(72) InventorJ August Haeni, Jurastrasse 11, Turgi, CH: Hansulrich Hoerler, Lerchenberg 5, Zuerich, CH: Hans Ursprung, Bahnhofstråsse 52707 Turgi, CK.

(74) Plenipotentiary in the proceedings:

The engineering firm Lehmann & Ree ._ ^ (54) Muffler by a compressor intake s idea with several annular damping elements.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a silencer at the intake side of a compressor having a plurality of annular damping elements and of these formed flow ducts which direct the suction air into partial streams into an overall funnel serving the compressor.

In an exhaust gas turbocharger, the combustion air is compressed in a compressor driven by an exhaust gas turbine and supplied to the combustion engine. Usually, a silencer attached to the compressor housing is provided to attenuate the sound waves that occur during operation. The ambient air flows over a filter located along the perimeter of the silencer into the interior of the silencer equipped with silencer elements.

The silencer's internal compartment consists of two different compartments. In the radially outer annular space, the air flows over a relatively large low-velocity cross-section radially inward, whereas in the overall composite inner space, over a small flow cross-section, it flows approximately axially at high velocity.

In such a muffler, the muffler elements each have a cylindrical and a disc-shaped portion and are coaxially arranged with each other in the interior of the muffler in such a way that the majority of the muffler surfaces are in the assembly, which, due to the high velocities prevailing here, significant pressure loss occurs. In the annular space, on the other hand, in which the pressure losses are relatively small due to the prevailing low velocities, only relatively small damping surfaces are found, so that the given opportunities for advantageous flow conditions are not fully utilized.

In another known silencer, the annular space is better utilized in the application of larger damping surfaces therein, in addition to there being some diverting elements which direct part of the air in the direction of the main flow, but here, at the inlet of the flow ducts, significant swirling losses occur as a result of the different flow directions and flow rates.

Both of the two mentioned muffler designs suffer from the additional drawbacks that different surfaces of the muffler's interior compartment to obtain sufficient muffler must be coated with muffler material, which complicates the fabrication. Such silencers, which result in large flow losses and are difficult to manufacture, become disproportionately expensive, especially with the nowadays usual high compressor rpm and the new noise regulations that set the permissible noise level.

The object of the invention is to provide an attenuator of the kind mentioned above, at which the flow losses and manufacturing costs are lower than at the known attenuators and at which the attenuation is also satisfactory at high compressor rpm.

This task is solved according to the invention in that each damping element at its inner circumference passes into a guide element such that these guide elements are curved and designed to deflect the sub-currents emerging from the flow channels in the direction towards the main flow arising from the flow channel and that the sum of the outflow areas of all flow channels is at least approximately equal to the cross-sectional area of the outflow opening of the aggregate.

The muffler according to the invention offers the following advantages: The muffler elements and the muffler surfaces are arranged in the outer annulus of the muffler where low speeds prevail, so that the pressure losses also become small; the velocity vector of the slowly flowing subcurrent flows through the flow channels is adapted to the velocity vector of the main flow, thereby avoiding vortex loss; it is possible to use similar damping elements in a modular system and thus achieve a rational and economical manufacture; the sound attenuation is so effective that no surfaces in the silencer's interior must be coated with sound attenuating material, which makes manufacturing simpler and more economical.

According to the invention, the damping elements can be similar in shape and dimensions and restrict similar flow channels. In this way it is possible to use similar damping elements in a modular system and thus to obtain a rational and inexpensive manufacture.

Since the end channels, i.e. the two flow channels, which are extremely opposite to each other in the annulus housing annulus, are limited on their one side only by damping elements, on the other hand they are limited by each annular wall of the silencer housing and therefore can absorb only half the noise energy as the inner ones flow channels constrained by damping elements on both sides, these end channels suitably have an axial width which is approximately half the axial width of the other flow channels. This results in that each end channel only carries an approx. half the air volume of each of the other ducts.

Each attenuating element may be several in the circumferential direction successive segments. This embodiment also contributes to lowering the production and to a simple assembly.

The damping members may conveniently have rounded noses formed on their outer circumference. In this way, improved inflow conditions are obtained, which contributes to the inflow of air into the flow ducts without vortexing, so as to reduce the flow losses.

According to an advantageous embodiment, the muffler has several connecting rods distributed at the perimeter of the damping elements which hold the damping members to each other and to the housing, and furthermore have as spacers between the damping elements, the lengths of which determine the width of the flow channels and are dimensioned according to a desired ratio pressure drop and attenuation. In this way, the width of the ducts can be dimensioned according to a desired ratio between pressure drop and sound attenuation.

Embodiments of the invention are described below with reference to the drawings. In the drawing: FIG. 1 is a section through a silencer fitted with disc-shaped dampers and through the compressor of an exhaust gas turbocharger; and FIG. 2 is a sectional view similar to that of FIG. 1 but through a silencer with tapered attenuator elements.

In the figures, similar parts are provided with similar reference numerals.

The FIG. 1, a silencer shown in Fig. 1 consists of a housing 2 connected to an exhaust gas turbocharger 1, and filter segments 3 arranged along the circumference of the housing, and of substantially disc-shaped damping elements 4 arranged in the silencer's inner space. the circumference of the damping elements 4 distributed connecting rods 5 and are kept at a desired distance from each other by means of spacers 6 which are arranged on the connecting rods. The damping elements 4 are arranged in an annulus in the interior of the silencer and restrict flow channels 9 which open into an overall funnel 8. The flow channels 9 conduct radially inwardly flow inwardly of the filter segments 3 radially inwards towards the overall funnel 8.

The attenuating elements 4 are formed at their internal circumference as guide elements 10. These are curved and so formed that the sub-currents from their radial flow direction deflect through the attenuation elements in the direction of the main flow arising in the assembly 8. The outflow cross-sections of the flow channels 9 formed by the guide elements 10 are dimensioned such that the total sum of these is at least approximately equal to the cross-sectional area of the outflow opening 8 of the aggregate 8. Thus, the velocity vector of the air exiting from the ducts 9 is approximately equal to the average value of the main flow velocity vector. This greatly avoids flow losses due to eddy formation in the outgoing partial flows, and the pressure drop in the silencer is reduced.

The attenuating elements 4 of the embodiment shown in FIG. 1 is similar in shape and dimensions and, with the exception of two extremes at each end of the silencer, attenuates similar channels 9. Since the end channels 11 are limited on their one side only by attenuators 4 and therefore can only absorb half as much noise energy as the internal flow channels 9, which are limited by damping elements on both sides, these end channels 11 are formed with an axial width which is only about half the width of the channels 9, so that the end channels 11 carry only approx. half the amount of air as the ducts 9. The damping elements 4 have rounded noses 12 at their outer circumference, which improve the inflow conditions. All sound attenuating surfaces are arranged in the annulus 7 where the air velocity and thus the pressure legs are low. None of the inner surfaces of the housing 2 are coated with sound attenuating material, without satisfactory sound attenuation even without this measure.

Instead of disc shaped dowel elements, tapered dampers can also be used, as shown in FIG. 2, or curved damping elements with corresponding flow channels.

The length of the spacers 6 arranged as spacers between the attenuating elements 4 determines the width of the ducts 9 and is dimensioned according to a desired ratio between pressure drop and sound attenuation. This ratio can be varied simply by using different length spacers and thus by changing the channel width.

The described silencer can be used for all types of compressors, e.g. for exhaust gas turbochargers, blast furnaces or gas turbine plants.