RU2287092C2 - Device for decreasing noise from axial ventilator of space object - Google Patents

Abstract

FIELD: space engineering, aviation industry, watercraft industry, mechanical industry, etc.

SUBSTANCE: onto input and/or output of axial ventilator, noise damping device is mounted, made in form of head of alternating layers of elastic material with high and low density, connected by holding element in meeting points. Layer of elastic material with high density is compressed between layers of elastic material with low density, while both materials are held inside the cover of air-impenetrable fabric for prevention of blowing out by air flow of layers of elastic materials with high and low density. To impart given shape to head for input and/or output of air, shape-forming frame is contacted.

EFFECT: at frequencies lower than 1000 Hz device operates not worse than prototype, at frequencies above 1000 Hz device allows to decrease noise from axial ventilator mounted on space object by 2-10 decibels and simultaneously to simplify mounting technical under space flight conditions while also decreasing its mass-dimensional characteristics.

Description

This invention relates to space technology, aircraft, shipbuilding, mechanical engineering, etc.

A known device for reducing noise, consisting of a rigid body, a sound absorber (low density material) [1] (p. 134, Fig. 43).

Its disadvantage is the large dimensions, the presence of a rigid case (which increases the weight characteristics).

It is also known a noise reduction device consisting of a rigid body, a sound absorber (low density material) [2] (p. 83, Fig. 41).

Its disadvantage is the large dimensions, the presence of a rigid case (which increases the weight characteristics).

Also known is a noise reduction device consisting of a rigid body, a sound absorber (low-density material), and a perforated pipe [3] (p. 227, Fig. 7.22). This device is made in the form of a nozzle at the air outlet, consisting of two cylinders of different diameters, one of which is inside the other. Between the cylinders is a sound absorber (low density material). The outer cylinder acts as a rigid body. The inner cylinder is perforated and serves to hold the sound absorber (low density material).

Its disadvantage is the presence of a rigid body (which increases the weight characteristics), the presence of a perforated pipe (which increases the weight characteristics; does not provide sufficient protection for the sound absorber (low-density material) from blowing; it helps to reflect the sound wave, which worsens the sound-absorbing characteristics of the device).

The objective of the invention is to reduce the noise level from the axial fan installed in the space object, as well as reducing the overall dimensions during transportation by ground transport and delivering it into orbit, simplifying the installation technique in space flight conditions, and also reducing the mass during normal operation.

The problem is solved in that a noise reduction device is installed at the inlet and / or outlet of the axial fan, made in the form of a nozzle of alternating layers of elastic material with high and low density, connected by a fastening element at the joints. In this case, a layer of elastic material with a high density is enclosed between layers of elastic material with a low density, both materials being placed in a cover made of an airtight fabric to prevent the layers of high and low density elastic materials from being blown out by the air stream. To give the desired shape, the nozzles of the inlet and / or outlet of the air are in contact with the forming frame.

The technical result of the invention is to reduce noise from an axial fan while simplifying installation technology in space flight conditions and reducing weight and size characteristics.

Figure 1 shows a prototype device for reducing noise from an axial fan.

Figure 2 shows the proposed device for reducing noise from the axial fan of a space object.

Figure 3 presents the measurement results in the form of 1/3-octave spectra.

In these figures:

1 - axial fan;

2 - nozzles at the air inlet;

3 - nozzles at the air outlet;

4 - a layer of elastic material with a high density;

5 - layer of elastic material with low density;

6 - a cover from airtight fabric;

7 - hard case;

8 - forming frame;

9 - a protective grid of the fan;

10 - fastener;

11 - noise spectrum during fan operation without a noise reduction device;

12 is a noise spectrum when operating a fan with a prototype noise reduction device at the air outlet;

13 - noise spectrum during operation of the fan with the proposed device to reduce noise at the inlet or outlet of air;

14 - noise spectrum during operation of the fan with the proposed device to reduce noise at the inlet and outlet of air.

In the proposed device for reducing noise from the axial fan 1 of a space object, there are nozzles at the air inlet 2 and / or air outlet 3, each of which is made, for example, in the form of a cylindrical nozzle from alternating layers of elastic material with high density 4 and elastic material with low density 5 and connected by a fastening element 10 at the joints. At the same time, a layer of elastic material with a high density 4 is enclosed between layers of elastic material with a low density 5, while both materials are placed in a cover made of an airtight fabric 6. In order to give the nozzles (s) a given shape, the air inlet 2 and / or air outlet 3 contacts ( j) with the forming frame 8. When installing the nozzle (s), a layer of material with a high density 4 is located along the axis of fan 1.

The basic principle of the noise reduction device is to attenuate the sound wave when passing through alternating layers of elastic materials of different densities: high density made, for example, of non-woven needle-punched or, for example, rubber-like material and low density, made, for example, of loose-fibrous material. In doing so, the following occurs. The sound wave from the fan 1 enters the layer of material with a low density of 5 and partially attenuates. Further, the attenuated sound wave enters the layer of material with a high density of 4, losing energy that is converted into energy of heating, and passes the layer of material with a low density of 5, attenuating even more. Moreover, part of the sound wave, reflected from the layer of material with a high density of 4, goes in the opposite direction, attenuating in the layer of material with a low density of 5.

The presence of a layer of material with a low density of 5 on the outside of the nozzle makes it possible to partially suppress the sound wave emanating from another noise source.

The presence of a cover made of an airtight fabric 6 prevents blowing out by a stream of air of layers of elastic materials with a high density of 4 and low density of 5, which contributes to the long-term operation of the device without reducing sound absorbing properties.

Experimental studies have shown that at frequencies below 1000 Hz the proposed device works no worse than the prototype, and at frequencies above 1000 Hz the device allows to reduce noise from an axial fan installed in a space object by 2-10 dB and at the same time simplify installation technology in space flight with a decrease in its overall dimensions.

Literature

[1] - L.F. Lagunov, G.L. Osipov "The fight against noise in mechanical engineering", Moscow, Mechanical Engineering, 1980.

[2] - A.S. Pogodin "Sound-attenuating devices", Moscow, Mechanical Engineering, 1973.

[3] - Handbook of marine acoustics under the general editorship of Doctor of Technical Sciences I.I. Klyukina and Ph.D. I.I. Bogolepova, Leningrad, Shipbuilding, 1978

Claims (4)

1. A device for reducing noise from the axial fan of a space object, containing nozzles of the air outlet, and the nozzle mounted on the inlet and / or outlet of the air is made of alternating layers of elastic material with high and low density, connected by a fastening element at the joints, while the layer a high density elastic material is sandwiched between layers of a low density elastic material. 2. The device according to claim 1, characterized in that alternating layers of elastic materials with high and low density are placed in a cover made of airtight fabric. 3. The device according to claim 1, characterized in that the high-density material is made of non-woven needle-punched or rubber-like material. 4. The device according to claim 1, characterized in that the low-density material is made of loose fibrous material.

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