EP1857682B1 - Rotary piston machine with silencer - Google Patents

Description

Technical area

The invention relates to a dry-running rotary piston machine with Reaktionsschälldämpfer for gases or gas-vapor mixtures, which at least two mounted in a housing via shafts and bearing assemblies rotary pistons, which mesh with each other in opposite directions to define a delivery chamber, said waves operationally via toothed timing wheels coupled together. Under dry running is to be understood that the rotary piston itself not through. Lubricating lubricants such as lubricating oil or the like.

State of the art

Dry-running rotary piston engines, in particular rotary screw compressors and Rotary blowers of the type Roots, but also rotary piston expansion machines, work today with relatively high differential pressures (up to 7 bar) and speeds (up to about 20,000 1 / min). A problem which generally exists in these rotary piston machines is that a part of the already compressed medium from the pressure-side pipe strikes back into the delivery chamber when the delivery chamber is opened, thus leading to strong pulsations or oscillations both in the compressor and in the downstream delivery-side delivery line. These pulsations are responsible for the high noise level of such machines, especially in the low frequency range. Rotary engines of this type are for Example from the DE 32 38 015 known. In screw compressors having an internal compression due to the highly twisted piston, in addition to the phenomenon described above, depending on the backpressure when opening the delivery chamber to the pressure side, a sudden outflow of the previously over-compressed fluid may occur.

Due to the high speeds that are common today, the frequency spectrum of the emitted sound also has high noise levels even at frequencies in the kilohertz range. This frequency range is perceived by the human ear usually as disturbing. In order to reduce these noise levels to the required or legally prescribed values, silencers are used, two types being basically to be distinguished. These are on the one hand absorption silencers, which work with different absorption materials such as steel or mineral wool, and on the other hand the so-called resonance or reaction silencers, which work without such materials only by the special shape and dimensions of the silencer.

Absorption mufflers damp particularly high frequencies very well, but have several disadvantages. On the one hand, they dampen the lower frequency range only poorly or not at all, due to the very small thickness of the absorptive material compared to the sound wave length. Because of their close-meshed structure, absorption mufflers also become dirty, especially in the case of exhaust gases loaded by liquids or solids, which increasingly prevents the correct functioning of the muffler. In addition, fibers or other components can be discharged from the absorbent material, which can lead to serious problems in the downstream system and is therefore undesirable.

Reflection mufflers generally consist of an inner tube and an outer tube (the chamber), which are connected together to allow the passage of gas. They work on the principle that by the smaller Inner tube with the gas flow into the chamber entering sound is reflected due to the abrupt change in cross section.

The cut-off frequency and the strength of the insulation depends to a great extent on the geometry of the silencer. To obtain the highest possible insulation, the ratio of the diameter of the chamber to the diameter of the inner tube (D / d) must be as large as possible. On the other hand, since the limit frequency f _gr , above which the Schalldämmwirkung drops sharply, inversely proportional to the diameter of the chamber (f _gr ~ 1 / D), the outer diameter of the chamber must not be too large to allow the insulation of high frequencies.

For space reasons, one would not like to make the diameter of the chamber too large, so that one could try to keep the ratio of the diameters large and to limit the outer diameter by reducing the diameter of the inner tube. As a result, however, the flow resistance is increased, which of course is undesirable, as a result, a higher power consumption of the upstream rotary engine is effected.

A way out is the parallel arrangement of several inner tubes and the simultaneous subdivision of the outer tube (the so-called Mehrflutigkeit). An example is in the EP 1 117 965 shown. The inner diameter of the individual tubes is chosen so that the same flow resistance results as with a single, large inner tube. With 4 inner tubes, for example, d _small = d _large / 2. The diameter of the chamber D, however, is halved, so that the limit frequency of the insulation can be approximately doubled.

In order to improve the insulation in other ways, so-called Helmholtz inner tubes are used, in which holes are provided at a certain axial position in the inner tube shell. These can be evenly distributed over the entire shell, such as in the US 2,241,010 described, or may be present only at certain points by means of perforated plates, see, for example EP 0 798 694 ,

Furthermore, the outer tube is often divided into axially arranged chambers of different lengths (and thus different resonance frequencies), wherein each of the chambers are connected via the holes in the inner tube shell with the sound-conducting inner tube. An example is in the document DE 296 12 322 shown.

From the documents DE 1166970 and DE 19855708 Two further solutions in the form of resonance mufflers are known.

However, none of the above solutions can be used satisfactorily with the rotary piston machines mentioned above, which, as mentioned, generate very high noise levels. In particular, such silencer would either be very large and thus take up space and expensive or bring too large a pressure drop, which has a negative effect on the power consumption, efficiency and cost of the rotary piston engine.

Presentation of the invention

It is thus an object of the present invention to develop a dry-running rotary piston engine with reaction shell damper, which has a large insulation effect with the lowest possible additional power consumption due to the muffler. This object is achieved by a dry-running rotary piston engine with reaction muffler with the features defined in claim 1.

Further advantageous embodiments will be apparent from the dependent claims.

Furthermore, it is desirable that the insulation be effective not only in terms of the amplitude of the sound at certain frequencies but over the entire frequency range.

With regard to the insulating effect, the invention is concerned with the connection openings in the shell of a Helmholtz inner tube. It has been found that more holes (or better a larger area of the holes) better Insulation properties bring with it. This can be done by enlarging the individual holes themselves. Extrapolating to the limiting case, the holes become slits, which are formed predominantly transversely to the axial extent, that is to say in the circumferential direction on the jacket of the inner tube. Only a few webs remain for the mechanical connection of the inner tube available. Measurements have shown that by using the slots instead of holes, the insulation effect is surprisingly greatly improved.

Thus, the present invention provides a dry-running rotary muffler with reaction muffler comprising at least two rotatably mounted in a housing via shafts and bearing assemblies rotors which mesh with each other in opposite directions to define a delivery space, the waves are operatively coupled via control wheels, and wherein the Muffler has a silencing chamber, an inlet opening and an outlet opening,. The rotary engine with reaction muffler is characterized in that the sound-damping chamber is divided by one or more parallel to the axial direction partitions (55,63a, 65) into two or more chamber parts (51b-e, 61b, d), which together define a multi-flow chamber wherein an inner tube (52b-e, 62b, d) is provided through each chamber member, which gas passes through the sound attenuation chamber, and on the inner tubes a plurality of slots are provided substantially in the circumferential direction, wherein the majority of the gas flows through the inner tube.

In comparison to the prior art, this results in a significantly improved insulation of the sound pressure generated by the rotary piston engine.

On the other hand, a larger area fraction of the holes can be achieved by several positions at which the holes are concentrated. Mathematically calculable / modelable are cases in which there are two instead of one position in the inner tube at which the holes are arranged. Applicant's experimental measurements have shown that placing the holes at the front and in the middle of the inner tube (possibly repeated for each chamber section) gives the best soundproofing.

Preferably, the slots are separated in the circumferential direction by webs. In this way, almost the entire circumference can be used for the slot surface, wherein the webs simultaneously ensure the stability of the tube.

The ratio of web area to slot area is preferably less than 30%, particularly preferably less than 25%, and in particular less than 20%. These values are significantly better than the corresponding values for perforated plates and provide improved leakage of sound pressure through the slots without jeopardizing tube stability.

In a preferred embodiment, the slots are provided in the flow direction on the front third and / or the middle third and / or the rear third of the inner tube. Measurements have shown that thereby the conditions of use (frequency spectrum and amplitude of the sound from the rotary piston engine, pipe diameter, type of gas application) adapted optimum insulation effect can be achieved.

The muffler is preferably divided by at least one partition wall such that they define / define a plurality of sound damping chambers in the flow direction, wherein an inner pipe leads through at least one sound damping chamber. These Schalldämpfkammern can be used for insulation around different resonance frequencies around or serve as distribution or collection chambers. It should be noted that the partition wall or walls divide the muffler in the flow direction into chambers, so that arise at a deflected flow so-called folded arrangements, wherein the flow direction in a chamber in opposite directions or perpendicular to the flow direction in an adjacent, through the Partition wall is divided chamber.

Preferably, one or more sound-damping chambers is or are divided by one or more partitions parallel to the axial direction into two or more chamber parts, which together form a multi-flow chamber or chambers define, wherein an inner tube is provided by each chamber part. Here, the respective inner tubes are usually parallel to each other. Thus, the cut-off frequency of the soundproofing effect is multiplied in an efficient manner without increasing the flow resistance of the silencer and thus the energy consumption of the rotary piston engine.

Preferably, in the rotary piston engine according to the invention with reaction muffler, the axes of the inlet opening and the outlet opening of the muffler form an angle of substantially 90 ° to one another. This arrangement is particularly favorable for such rotary engines, which are made due to their relatively small size on the silencer and use this as a basis.

Brief description of the drawings

• FIG. 1 schematically represents a rotary piston engine with a connected single-flow single-flow reaction muffler;
• FIG. 2 schematically represents a rotary piston engine with a connected single-flow multi-chamber reaction muffler;
• FIG. 3 schematically represents a rotary piston engine with a connected single-flow, folded multi-chamber reaction muffler;
• FIG. 4a shows schematically a rotary piston engine with a multi-flow straight multi-chamber reaction muffler according to the invention;
• FIG. 4b is a section through the muffler along the line AA in Fig. 4a ;
• FIG. 5a is a schematic representation of a rotary engine with a mehrflutigen, folded Multi-chamber reaction muffler according to the invention; and
• FIG. 5b is a section through the arrangement of Fig. 5a along the line AA.

Ways to carry out the invention

In Fig.1 a first embodiment is shown. The outlet of a rotary engine 10 is connected via flanges 11 and a pipe 12 to the inlet of a reflection muffler 20. The muffler 20 into which the sounding gas ejected from the rotary piston engine flows consists of a muffler chamber 21 and an inner tube 22 through which the same cross section as the pipe 12 and the outlet of the rotary machine 10 pass, as small as possible To generate pressure drop. On the inner tube 22, slots 24 are provided in the flow direction (indicated by arrows) in the front and middle third, the size of which may be different. The slots 24 are separated in the circumferential direction by webs 25, so that in Fig. 1 Apart from the visible further slots 24 are present on the side facing away from the viewer. Through the slots, a large part of the sound pressure, which carries the incoming gas to expand into the muffler chamber 21, without significant amounts of gas from the inner tube 22 itself exit into the muffler chamber 21. This results in a surprisingly good, broadband sound insulation effect that can not be achieved with conventional perforated sheets.

FIG. 2 FIG. 4 illustrates an embodiment in which a muffler 30, as previously described in FIG Fig. 1 is connected to a rotary piston machine 10, divided by two partition walls 33 in a distribution chamber 31 a, a sound-damping chamber 31 b and a collecting chamber 31 c is. Through the sound-damping chamber 31b performs an inner tube 32, which has slots 34 on its jacket in the flow direction in the front, middle and rear third, through which the sound pressure in the muffler chamber 31b can escape. Here, the manifold chamber 31a and 31c cause deceleration and subsequent acceleration of the gas entering the muffler 30 respectively before and after being damped in the muffler chamber 31b. The chamber 31a and 31c thus also work as muffler chambers, but according to the conventional reflection principle.

An arrangement in which the rotary piston engine 10 uses the muffler 40 as a base is shown in FIG Fig. 3 illustrated. The axes of inlet 48 and outlet 49 form an angle of 90 °. The muffler 40 is divided by two partition walls 43 into an inlet chamber 41 a, a deflection chamber 41 b and an end chamber 41 c. The gas ejected from the machine 10 is first guided into the inlet chamber 41a, from where it passes through a passage tube 45 into the deflection chamber 41b. From there it flows through a closed tube 42a again through the inlet chambers 41a and into the end chamber 41c, in which there is provided with circumferential slots 44 (without webs) in the front and middle third inner tube 42b. The "deflection" of the gas flow is also called a "folded" silencer arrangement.

An embodiment of the invention in which the Mehrflutigkeit is used is in FIG. 4a shown. Again, a muffler 50 serves as a base for the rotary engine 10, so that the axes of inlet and outlet of the muffler 50 form a 90 ° angle. Two partition walls 53 divide the muffler 50 into an inlet chamber (manifold chamber) 51a, an outlet chamber (plenum) 51f, and a muffler chamber therebetween. As in Fig. 4b shown, the latter is divided by two in the flow direction in the muffler chamber perpendicular to each other partitions 55 into four substantially mutually parallel chamber parts 51b, c, d, e, wherein each of the chamber parts an associated inner tube 52b, c, d, e leads. The muffler chamber is thus divided into multiple floods. Slots 54 are provided on each inner tube 52b, c, d, e respectively in the front and rear third, which allow a sound pressure outlet in the chamber parts 51b, c, d, e. The sum of the cross sections of the inner tubes corresponds to the cross section of a corresponding single-flow inner tube or the diameter of the inlet nozzle of the muffler, so that no increase in the flow resistance occurs. At the same time, a high ratio of chamber part diameter (outer diameter) to the inner pipe diameter can be maintained.

In Fig. 5a Finally, another embodiment of the invention is shown. Here, a muffler 60 is disposed above the rotary piston machine 10. A plurality of partition walls 63a, b, c, d divide the muffler 60 in the flow direction into chambers 61a, b, c, d, e, with the partition wall 63a arranged horizontally and the remaining partition walls vertically. Further, the chamber 61b is divided by a vertical partition 65 into two chambers 61b 'and 61b''double-flow. The chamber 61d is traversed by an inner tube 62d of square cross section, while the chambers 61b 'and 61b "are traversed by square inner tubes 62b' and 62b" respectively, the sum of their cross sections being equal to the cross section of the inner tube 62d. All the inner tubes 62b ', 62b "and 62d have circumferential slots 64 in the direction of flow in the front and middle third portions the axes of the muffler inlet 68 and outlet 69 arranged parallel and offset from one another.

Claims (8)

1. Dry-running rotary piston machine (10) with reaction sound absorber (50, 60), comprising at least two rotary pistons mounted in a housing via shafts and bearing arrangements which mesh with one another in opposite directions to define a conveying chamber, wherein the shafts are operationally coupled to one another via control wheels, wherein the sound absorber has a sound-absorbing chamber (51,61), an inlet opening (58, 68) and an outlet opening (59, 69), characterised in that the sound-absorbing chamber is divided into two or more chamber parts (51b-e, 61b, d) by one or more separating walls (55, 63a, 65) parallel to the axial direction and which together define a split-flow chamber, wherein an inner pipe (52b-e, 62b, d), which passes gas through the sound-absorbing chamber, is provided through each chamber part, and several slots (54, 64) are provided on the inner pipes orientated essentially peripherally, wherein the greater part of the gas flows through the inner pipe.
2. Rotary piston machine (10) with reaction sound absorber according to claim 1, characterised in that the slots are separated peripherally by bars (25).
3. Rotary piston machine (10) with reaction sound absorber according to claim 2, characterised in that the ratio of bar surface to slot surface is less than 30%.
4. Rotary piston machine (10) with reaction sound absorber according to claim 2, characterised in that the ratio of bar surface to slot surface is less than 25%.
5. Rotary piston machine (10) with reaction sound absorber according to claim 2, characterised in that the ratio of bar surface to slot surface is less than 20%.
6. Rotary piston machine (10) with reaction sound absorber according to one of the preceding claims, characterised in that the slots (24, 34, 44, 54, 64) are provided in flow direction on the front third and/or the central third and/or the rear third of the inner pipe (22, 32, 42, 52, 62).
7. Rotary piston machine (10) with reaction sound absorber according to one of the preceding claims, characterised in that the sound absorber (30, 40, 50, 60) is divided by at least one dividing wall (33, 43, 53, 63) such that in flow direction the latter defines/define several sound-absorbing chambers (31a-c; 41a-c; 51 a, c; 61a-e), wherein an inner pipe (32; 42a, b; 52b-d; 62b, d) runs through at least one sound-absorbing chamber.
8. Rotary piston machine (10) with reaction sound absorber according to one of the preceding claims, characterised in that the axes of the inlet opening (48, 58) and the outlet opening (49, 59) of the sound absorber (40, 50) form an angle of essentially 90° to one another.

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