RU2194171C2 - Muffler - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: invention relates to noise silences of power generating plants, for instance, internal combustion engines. Gas flow with distributed sound waves passes through intake branch pipe into space of housing and is distributed in slot channels between longitudinal partitions passing along alternating necks of channels provided with internal construction sections and widening sections and is discharged outside or into adjacent space through discharge branch pipe. Owing to different cross section of slot channel sections, part of sound waves is reflected, thus partially damping the noise. Making of internal construction sections of length l_in-l ≤l_w-m²h where 1p is length of widening section, m is damping coefficient and h is minimum size of cross section of internal construction sections provides reduction of aerodynamic resistance by value equal to losses of pressure for overcoming sudden construction and widening of slot channels. EFFECT: provision of wide band noise damping. 2 dwg

Description

 The invention relates to the field of engineering, in particular power engineering, and in particular to silencers of predominantly power plants, such as internal combustion engines, and is an improvement of the known device described in the copyright certificate 1590611 [1].

 Known silencer [1] contains a housing with inlet and outlet pipes, divided by longitudinal partitions into slotted channels. The channels are formed by successively alternating sections of narrowing and expansion. The length of the narrowing section between the expansion areas is (0.8-1.2) of the geometric mean lengths of the preceding and following the channel extension sections. The longitudinal partitions are made of strips of stepped form. The areas of narrowing and expansion of adjacent slotted channels are placed alternating along the length of the housing.

 In the known silencer, the gas stream repeatedly passes through sudden narrowing and widening of the cross section of the slotted channels. With a sudden expansion, the flow breaks away from the channel wall and then moves at a certain distance, expanding, in the form of a free jet of a plane, due to the geometry of the shape gap. With a sudden narrowing, the stream contracts, occupying an area less than the cross-sectional area of the channel, then the jet begins to expand. In both cases, vortex formation during expansion of the jet causes significant pressure losses. Significant aerodynamic drag is a disadvantage of the known silencer, since it makes it difficult to use in conditions of limiting pressure loss.

 The technical result of the invention is to reduce aerodynamic drag.

The technical result is achieved in that in a noise suppressor comprising a housing with inlet and outlet nozzles, separated by longitudinal partitions made of step-shaped strips, into slotted channels formed by successively alternating narrowing and expansion sections, for which the length of the narrowing section between the expansion sections is ( 0.8-1.2) of the geometric mean lengths of the expansion sections preceding and following the slit channel, alternating between the narrowing and expansion sections of adjacent slotted channels fishing along the length of the housing, coaxially extended portions narrowing inwardly to form expansion portions nesmykayuschihsya internal restriction sites, the distance between which:
l _nn ≤ l _p -m ² h
where l _vn is the distance between the inner sections of the narrowing, m;
l _p is the length of the expansion section, into which the narrowing sections are extended, m;
m is the attenuation coefficient of velocity in a flat stream; m = 2.5;
h - the smallest of the dimensions of the cross section of the inner sections of the narrowing, m

The distance l _vn corresponds to the length of the initial section of the plane free jet and determines the constancy of the cross section of the jets passing through the narrowing and expansion of the slotted channels. We experimentally found that the placement of the internal sections of the narrowing at the required distance, preventing vortex formation, provides a reduction in pressure loss (by 25% for the speeds most common in power plant systems) without impairing the acoustic performance of the silencer. The possibility of reducing l _{int is} provided in order not to limit the choice of manufacturing technology of the device.

 Figure 1 shows a silencer, longitudinal section; figure 2 is a section a - a in figure 1.

The noise suppressor comprises a housing 1 with inlet 2 and exhaust 3 nozzles, separated by longitudinal partitions 4 into slotted channels 5, which are composed of successively alternating sections of narrowing 6 and expansion 7. The narrowing sections 6 are coaxially extended inside the expansion sections 7 with the formation of non-contacting internal sections constrictions 8. The distance l _int between sections 8 does not exceed a value determined by subtracting from the length l _p of the expansion section 7, into which the sections of narrowing 6 are extended, the product of the square of the coefficient m hiccups of velocity in a flat stream and the smallest of the dimensions h of the cross section of the inner sections of the narrowing 8.

 Silencer works as follows.

 The gas stream in which sound waves propagate through the inlet pipe 2 enters the cavity of the housing 1, is distributed in the slotted channels 5 between the longitudinal partitions 4, passes through the narrowing sections 6, which have internal narrowing sections 8, and the expansion sections 7, alternating in the channels 5 then, through the exhaust pipe 3 is discharged into the environment or an adjacent volume. Due to the difference in the cross section of the sections of the slotted channels 5, part of the sound waves is reflected back to the source, which leads to a partial attenuation of the noise. Muffler operation is characterized by broadband attenuation. The presence of narrowing sections 8 in the internal volume of the expansion sections 7 does not impair the acoustic performance of the silencer.

The implementation of the internal sections of the narrowing 8, which have a length that ensures constant flow cross-section during the passage of the slotted channels 5, makes it possible to reduce, compared with the prototype, the aerodynamic drag of the silencer by:
ΔP = [(1-T / S) ² k + 0.5 (1-T / S) n] P,
where ΔP is the pressure loss to overcome sudden contractions and extensions, Pa;
T is the cross-sectional area of the narrowing of the slotted channels, m ² ;
S is the cross-sectional area of the expansion areas of the slotted channels, m;
k is the number of excluded sudden contractions;
n is the number of excluded sudden extensions;
P - dynamic pressure, Pa.

Claims (1)

A silencer comprising a housing with inlet and outlet nozzles, separated by longitudinal partitions made of strips of step shape, into slotted channels formed by successively alternating sections of narrowing and expansion, for which the length of the narrowing section between the expansion sections is (0.8-1.2 ) from the geometric mean lengths of the preceding and subsequent expansion slots along the slotted channel, alternating between narrowing and widening adjacent slotted channels along the length of the casing, characterized in that ASTK narrowing axially extended inward extension portions to form an internal narrowing nesmykayuschihsya portions spaced
l _corolla ≤l _p -m ² h,
where l _vn is the distance between the inner sections of the narrowing, m;
l _p is the length of the expansion section, into which the narrowing sections are extended, m;
m is the attenuation coefficient of velocity in a flat stream; m = 2.5;
h - the smallest of the dimensions of the cross section of the inner sections of the narrowing, m

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