US1778101A - Exhaust silencer for aircraft motors and the like - Google Patents

Description

EXHAUST SILENCER FOR AIRCRAFT MOTORS AND THE LIKE Filed June 8, 1928 0/2 50/ e by Patented Oct. 14, 1930 PATENT. OFFICE OLE SOLIBERG 31E, OF OSLO, NORWAY EXHAUST SILENCE FOB AIRCRAFT MOTORS AND THE LIKE Application filed June 8,1928, Serial No. 283951, and in France November 22, 1927.

r The present invention has for its obj ect an exhaust silencer for aircraft motors and similar motors for transport means adapted to move through the air with high velocity, and 5 the object of the invention is to provide an exhaust silencer adapted to utilize the suction and cooling efiect of the air current in.

tively, in which zones the outlet openings for the exhaust gases from the silencer are located.

By giving the shell of the silencer this shape, an extremely efiicient effect is obtained, and this eflect increases with increasing velocity, whereby the loss of motor output caused by the silencer is reduced to an unimportant value. p

The eflect of the zone with reduced air pressure and turbulent air created by the above mentioned shape of the shell also has a very pronounced efi'ect on the silencer action owing to the fact that the point or points at which the sound waves are created, that is,

the zone immediately surrounding the outlet openings, is located in a medium which is a bad conductor of sound, and this efiect also increases with increasing velocity and decreasing air pressure in the said zone.

At the same time the interior construction of the silencer is so designed that the exhaust gases before arriving at the outlet openings from the silencer are caused to pass in a comparatively thin film along a substantial part of the exterior shell of the silencer so as to be subjected to an effective cooling by means of the air through which the silencer passes with great velocity.

If so desired, this cooling efiect may beincreased in a manner known per se by means of an air duct passing coaxially through the silencer.

The accompanying drawing illustrates two modifications of the invention, in which similar reference numerals refer to similar parts and wherein:

I Figure 1 is a longitudinal axial cross-section of the exhaust silencer.

Figure 2 is a longitudinal axial cross-section of a modification of the exhaust silencer.

Referring, now, to Figure 1, the exhaust gases are conducted through the exhaust tubes 1 into a collecting chamber 2, the introduction into this chamber taking place in a tangential direction, so that the gas currents are caused to pass through the collecting chamber along helical lines. A

From the collecting chamber 2 the exhaust gas is conducted through a Venturi tube 3 with reduced cross section into a distributing chamber 4.

The Venturi tube 3 is shaped in accordance with the Venturi-principle in order to produce a suction effect between the collecting" chamber 2 and the distributing chamber 4.

The distributing chamber 4 preferably taperstowards the rear and is provided with outlet openings 4' distributed over the walls thereof in the longitudinal direction.

' Through the said outlet openings 4 the exhaust gas passes'into a silencer chamber 5 between the exterior walls of the distribu ting chamber 4 and a baflie 6 forcing the sev eral gas currents from the outlet openings 4' in the wall of the distributing chamber 4 to pass towards the front end of the silencer. The double conical exterior surface of the g5 silencer chamber 5 has the effect of providing a restricted annular passage which causes another Venturi-effect to take place. At its front end the baflle 6 is provided with an inwardly projecting beaded annular rib 11, so w as to produce a smooth path for the gas currents at the turn. a

From the annular chamber at the end of the baflle wall and to the front end of the silencer, the exhaust gas passes through a narrow'channel 7 of annular cross section, the'exterior wall of which is formed by the exterior shell 8 of the silencer, which is eifectively cooled by means of the air through which the silencer is passing. Finally the 9 at or near the rear end of the shell of the silencer.

Towards the rear end thereof the silencer is given a form which deviates in such. a manner from the stream linev form that there is formed at the part of the shell surface where the outlet openings for the exhaust gases are located, zones with reduced air pressure. This will have the effect of producing very effective suction at the outlet openings, a suction radically different from the suction which may be obtained-owing to ejector action by letting the gases out through openings along the edges of which air currents pass With great velocity.

The difference from suction produced by ejector action is perhaps still more pronounced as regards the silencer action owing to the fact that whereas the sound in case of ejector outletsis developed at points where the sound waves are directly transmitted to the surrounding air, the sound waves in the present'instance are developed in a zone with a considerably reduced air pressure, which has the effect of damping the sound waves considerably before theyreach'air of normal pressure. v t On the drawing the normal stream line form for the relative velocities in question is indicated by means of dotted lines at the rear end of the silencer, and it will be noted that the exterior contour of the silencer from a point near the largest cross section thereof is curved considerably more inwards than would be the case for the normal stream line increasing the cooling action.

As many different modifications of my invention may bemade, the above disclosure is to be construed in an illustrative and not in a limiting sense.

Having now fully described my invention what I desire to toprotect by Letters Patent -is defined in the following claims:

1. In an exhaust silencer for aircraft motors and the like, in combination,'a plurality of exhaust conduits from the motor, a collecting chamber communicating the'rewithand having a stream line form, an exterior shell having the front portion thereof in stream line relation to said collecting chamberand the rear portion thereof deviating in axial direction from said stream line form to create a zone of turbulent air under reduced pressure at the rear of said shell, outlet open- 1ngs for the exhaust gases located in said zone and means for causing the exhaust gases to pass in a shallow current along a substantial part of the interior of said exterior shell before arriving at said outlet openings.

2. An exhaust silencer for aircraft motors and the like, having a plurality of exhaust conduits connected to the motor, a collecting chamber adapted to be connected to said exhaust conduits, a distributing chamber, a Venturi tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributing chamber', outlet openings in the wall of said distributing chamber and means for-conducting the gas currents first toward the front end of said shell and then along the inside thereof to outlet openings located adjacent the rear end of said shell. 1

3. An exhaust silencer for aircraft motors and the like, having a collecting chamber adapted to be connected to the exhaust conduit from the motor, a distributing chamber, a Venturi tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributing chamber, said shell having a form adapted to create zones on its exterior surface with reduced air pressure, outlet openings in the wall of said distributing chamber and means for conducting the gas currents first towards the front end of said shell and then along the inside thereof to outlet openings located in said zones of reduced air pressure. I

4. An exhaust silencer for aircraft motors and the like, comprising a collecting chamber adapted to be connected to the exhaust conduit from the motor, a distributing chamber, a Ventu'ri tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributing chamber, said shell having a form adapted to create zones on its exterior surface with reduced air pressure, outlet openings distributed along the wall of said distributing chamber, a baflie between said distributing chamber and the shell, said baflie terminating adjacent the front end of said shell so as to conduct-the gas currents first towards the front end of said shell and then along the inside thereof to outlet openings located adjacent the rear end of said shell.

'5. An-exhaust silencer for aircraft motors and the like, comprising a collecting chamber tapering towards its front end and adapted to be connected to the exhaust conduit from the motor, a distributing chamber tapering towards the rear, a Venturi tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributing chamber, said shell having a form adapted to create zones on its exterior surface with reduced air pressure,'outlet openings in the wall of said dis tributing chamber and means for conducting the-gas currents first towards the front end of said shell and then along the inside thereof to outlet openings located in said zones of reduced air pressure.

6. An exhaust silencer for aircraft motors and the like, comprising a collecting chamber adapted to be connected to the exhaust conduit from the motor, a distributing chamber, said collecting chamber and distributing chamber being both conicallv shaped and having their bases turned towards each other, a Venturi tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributin chamber, said shell having a form adapted to create zones on its exterior surface with reduced air pressure, outlet openings in the wall of said distributing chamber and means for conducting the gas currents first towards I the front end of said shell and then along the inside thereof to outlet openings located in said zones of reduced air pressure.

7. An exhaust silencer for aircraft motors and the like, comprising a collecting chamber adapted to be connected to the exhaust conduit from the motor, a distributing chamber, a Venturi tube connecting said collecting chamber and said distributing chamber, an exterior shell surrounding said distributing chamber, said shell having a form ada ted to create zones on its exterior surface witi reduced air pressure, outlet openings distributed along the wall of said distributing chamber, a baffle between said distributing chamber and the shell, said baffle having an inwardly projecting beaded rim at its front end adjacent the front end of said shell so as to conduct the gas currents first towards the front through an annular opening of reduced cross section and then along the inside surface of said shell to outlet openings located adjacent the rear end thereof.

8. In an exhaust silencer for aircraft motors and the like, in combination, a plurality of exhaust conduits from the motor, a collecting chamber of streamline form communicating therewith, an exterior shell having the rear portion thereof deviating in axial direction from said streamline form to create a zone'of turbulent air under reduced pressure over part of the rear surface of said shell, and outlet openings for the exhaust gases located at the part of said rear portion within said turbulent zone.

In testimony whereofJI affix my signature.

, OLE SOLBERG BIE.

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