Main requirements laid to such mufflers are as follows: - efficiency of noise suppression, - small overall dimensions, - relatively low backpressure to the exhaust.

At present exhaust mufflers enjoy a wide practical use and they contain a hollow perforated cylinder-shaped chamber with an inlet pipe for the entry of exhaust gases. The chamber is hermetically embraced with a housing installed with an annular clearance relative to the chamber, this clearance forming an expansion space; the housing has an outlet pipe for exhausting the gases into the atmosphere.

In its cross-section the outlet pipe has a shape of the said annular clearance. The performance of the chamber is formed by slots made in its cylindrical wall which are oriented in such a way as to ensure the movement of the gas flow in the said expansion space on a spiral path.

In the course of muffler operation the exhaust gases enter the cylinder-shaped chamber and, through the holes of its perforation, come into the annular clearance where they swirl, expand and leave the muffler through the outlet pipe.

Noise suppression occurs due to the partial loss of the gas acoustic energy during the gas expansion and also during the flow swirling.

The drawback of such muffler consists in its relatively low efficiency on noise suppression.

There are well known various design versions of mufflers aimed at raising the efficiency of noise suppression.

In one of such versions the outlet pipe communicates directly with the atmosphere and it accomodates a swirling grid ensuring the dissection of the exhaust gas flow into jets and its dispersion in the atmosphere and also the swirling of the flow in the direction opposite to that which took place in the said expansion space.

Such muffler is more efficient because the unbroken jet of gases at the muffler outlet which carries a high acoustic energy is dissected into a great number ofjets as a result of which the acoustic energy is more efficiently absorbed by the atmosphere. Besides the change in the direction of the flow swirling also leads to additional noise suppression.

In another version the chamber wall is perforated by means of additional holes made and oriented in such a way that gas jets, coming out from it into the clearance, collide and lose a part of their energy The said versions ensure a certain rise in the noise suppression efficiency, however it remains not high enough.

The rise in the efficincy of noise suppression can be ensured at the expense of increasing the chamber volume or by greater clearance size. However this way has not found any practical use due to a considerable increase in the muffler overall dimensions.

The rise in the noise suppression efficiency can also be ensured at the expense of increasing the backpressure to the exhaust, for example, with the aid of a diaphragm installed in the inlet pipe. In this case the speed of the acoustic wave- front movement decreases. However in this case, as is known, there occurs the worsening of gas exchange in the engine cylinder, and it lowers the engine power and economical operation.

The object of the invention is the task of creating a muffler of exhaust gases which would contain additionally such an element and this element would be installed in such a way as to raise the efficiency of noise suppression maintaining the existing overall dimensions and relatively small backpressure to the exhaust.

The set task is solved in such a way that the exhaust gases muffler contains a chamber with an inlet pipe for the entry of exhaust gases, an acoustic damper located inside the chamber and a housing embracing the chamber hermetically and installed with a clearance relative to the chamber and having an outlet pipe for releasing the gases from the said clearance to the atmosphere, in this case the chamber walls within the portion between the inlet pipe and the acoustic damper are perforated and the housing embraces the chamber over this perforated portion.

The essence of the invention is illustrated by the drawings which are as follows: Fig. 1 - shows schematically the exhaust gases muffler according to the present invention, longitudinal section; Fig. 2 - design version of the exhaust gases muffler with a different acoustic damper; Fig. 3 - design version of the exhaust gases muffler with the use of an additional housing; Fig. 4 - version of muffler design with a movable damper.

Fig. 5 - another version of muffler design.

The exhaust gases muffler contains cylindrical chamber 1 (Fig. 1) with inlet pipe 2. installed on its end wall. Pipe 2 is made in the form of a contoured nozzle ensuring the flow acceleration and the decrease of the gases flow turbulence. In one of the versions the said pipe can be made not in the form of a nozzle. within chamber 1 on its opposite end wall acoustic damper 3 is mounted which is essentially a hollow pedbrated casing 4 filled with sound-absorbing material 5.

for example. basalt fibre. .Mly other Icnown materials can be used for sound- <BR> <BR> <BR> <BR> <BR> absorbing material. The cylindrical wall of chamber 1 is perforated with slots 6 with the main matel ial hent. over its perforated position chamber 1 is hermetically embraced hv cvlindrical housing 7 installed coaxiallv to the chamber and with a clearance relative to this chamber. this clearance forming expansion space 8. Slots 6 are made and oriented in such a way as to ensure the movement of gas jets in space 8 on a spiral path. Versions of the design are possible wherein cylindrical chamber 1 has any other different perforation . however. the presented one is most preferable since the creation of the jets movillg on a spiral path makes it possible to raise the efficiency of noise suppression. On the housing 7 end wall which is most distant from inlet pipe 2. outlet pipe 9 is installed to release the gases to the atmosphere. Pipe 9 is made in the form of an annular swirling grid of a known design installed coaxially to housing 7. this grid ensuring the swirling of the flow in a direction opposite to that which took place in space 8 and also the dissection and dispersion of the gas flow in the atmosphere. Other versions of pipe 9 design are possible (usual holes, annular hole and so on), however in these case the efficiency of noise suppression will be lower.

In one ofthe versions presented in Fig. 2 acoustic damper 3 is represented by the end wall of chamber 1 this wall having a known shape of a spherical sound baffle. This chamber wall may also have the shape of a toroid, trapezoid or other known shapes ensuring the appearance of directional reflected waves.

In another version presented in Fig. 3 intermediate cylindrical perforated housing 10 is installed between chamber 1 and housing 7 and in line with them.

This housing divides space 8 into two spaces: space 8a between chamber 1 and intermediate housing 10 where the expansion of exhaust gases takes place, and space 8b between intermediate housing 10 and housing 7. Housing 10 is perforated with slots 11 lying in planes perpendicular to slots 6 made in the walls of chamber 1. This means that slots 6 and 11 are oriented in perpendicular directions relative to each other. The relative position of the said slots at other angles is also possible. Outlet pipe 9 ensures the communication of space 8b with the atmosphere.

In a version presented in Fig. 4 between damper 3 and mentioned second end wall of housing 7 a springy element is installed, say, springy bellows 16. This bellows allows various positions of damper 3 at various values of gas pressure in chamber 1 which correspond to various conditions of the engine operation. When the engine is not in operation, bellows 16 is not deformed and casing 4 of the damper overlaps the maximum area of slots 6 as shown in Fig. 4. In this case the carrying capacity of chamber 1 is minimum. Characteristics of bellows 16 are determined experimentally and by calculations depending on conditions of ensuring the exhaust gases overflow optimum speed through slots 6 which favours maximum noise suppression.

In a version presented in Fig. 5 between housing 7 and damber 1 perforated shell 17 is installed coaxially which separates space 8 into two spaces: internal space 8c between chamber 1 and shell 17 and external space 8d between shell 17 and housing 7. Internal space 8c communicates with the space of outlet pipe 9 and external space 8d communicates with the space of inlet pipe 2. The ratio between the volumes of spaces 8c and 8d is selected experimentally proceeding from the cotdition of maxumum possible decrease of noise level at the damper outlet. This ratio depends of an engine type. its displacement. power and other parameters.

In the other version the proposed muffler can he used together with other inventions. For example the chamber wall, as mentioned above. can be perforated with additional holes made and oriented so. that the gas jets leaving the chamber and entering space 8 would collide and lose a part of their energy.

Other concrete versions of the invention embodiment are also possible 'ithin the claims. which differ from those described above in geometrical shape of units and parts. in thier relative position. in the design of individual elements. etc.

The muffler operates in the following way: Through inlet pipe 2 (Fig. 1) exhaust gases come under pressure into chamber 1 then, through slots 6 in chamber 1 they enter expansion space 8 where they lose a part of thier acoustic energy and through outlet pipe 9 they pass to the atmosphere. In transit of the exhaust gases within chamber 1 sound-absorbing material 3 absorbs a part of acoustic energy of the gases. The increase of the gas flow speed stipulated by the the fact that pipe 2 is made in the form of a contoured nozzle. promotes higher efficiency of noise suppression since it stirs up the process of acoustic energy absorbtion by means of the acoustic damper.

Besides. additional absorbtion of acoustic energy is achieved due to the movement of the gas flow in space 8 on a spiral path 12 and also due to the availabilitn of a swirling grid ensuring the swirling of the flow in the direction opposite to that which took place in space 8 and also ensuing the dissection and dispersion of the gas flow in the a mosphere.

In the version presented ill Fig. 2 the effect of noise suppression is achie'cd due to the collision of directional waves 13 reflected from the spherical surface and incoming waves 14.

In the version presented in Fig. 3 the gas How. while moving in space 8a on a spiral path. comes through slots 11 to space 8b. from where it passes to the atmosphere through pipe 9. In this case. due to the orientation of slots 6 and 11 in perpendicular directions relative to each other, during the flow passage from space 8a to space 8b the suppression of acoustic wave cross component 15 takes place. This results in additional rise in the noise suppression efYiciency.

In a version presented in Figure 4. when increasing the flow and, consequently, the pressure of exhaust gases, damper 3 overcoming the force of bellows 16, is moved towards the second end wall of the chamber. As a result the area of slots 6 through which the exhaust gases oufflow from chamber 1 takes place, increases.

At maximum gas flow the damper occupies position (shown by hatching in Fig.4) whereby the exhaust gases outflow occurs through all the slots over their entire area. Thus a preset speed of gases outflow through slots 6 is ensured at each condition of engine operation, and this results in additional increase of noise supression efficiency.

In a version presented in Fig. 3 a part of exhaust gases from the space of inlet pipe 2 come to space 8d where they are expanded and lose a part of their sound energy. Then. through the pertbration of shell 17. in the forii of dissipated jets 18 carrying the sound energy they enter space 8c where they collide with counter jets 19 coming via slots 6 trom chamber 1. As a result of tllese collisions additional drop of sound energy in the exhaust gases occurs. From space 8c the exhaust gases pass to the atmosphere through outlet pipe 9.