Title:
Turbogenerator exhaust silencer
Kind Code:
A1


Abstract:
An exhaust silencing device and method for silencing a turbogenerator includes a housing, an intake manifold, at least two exhaust outlet ports and flow channels which extend in a bifurcated path from the intake manifold to the exhaust outlet ports and which provide a length to height (or diameter) ratio permitting a compact fluid flow profile.



Inventors:
Rouse, Gregory C. (Westlake Village, CA, US)
Application Number:
09/985435
Publication Date:
07/25/2002
Filing Date:
11/02/2001
Assignee:
CAPSTONE TURBINE CORPORATION (Chatsworth, CA, US)
Primary Class:
Other Classes:
181/268
International Classes:
F01D25/30; F01N1/24; F01N13/08; F02K1/40; F02K1/82; (IPC1-7): F01N7/00
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Primary Examiner:
SAN MARTIN, EDGARDO
Attorney, Agent or Firm:
RICHARD H. ZAITLEN, ESQ. (LOS ANGELES, CA, US)
Claims:

What is claimed as new and desired to be secured by Letters Patent of the United States is:



1. An exhaust silencer device, comprising: a housing; an intake wall and an exhaust wall disposed within said housing, said intake wall and said exhaust wall and forming a flow channel; an intake manifold formed within said intake wall; at least two exhaust outlet ports formed within said exhaust wall; and wherein said flow channel extends from said intake manifold, said flow channel is bifurcated to terminate at said two exhaust outlet ports.

2. The exhaust silencer device of claim 1, wherein said flow channel is formed as a substantially T-shaped configuration.

3. The exhaust silencer device of claim 1, wherein said flow channel has a length to height ratio that results in a compact fluid flow profile.

4. The exhaust silencer device of claim 1, wherein sound attenuating material is disposed within said housing.

5. The exhaust silencer device of claim 4, wherein said sound attenuating material is selected from the group consisting of fiberglass, mineral wool and ceramic wool.

6. The exhaust silencer of claim 4, wherein said sound attenuating material is a fiberous bulk material.

7. The exhaust silencer device of claim 4, wherein the sound attenuating material is in a form selected from the group consisting of woven material, blankets and blown material.

8. The exhaust silencer of claim 1, wherein said flow channel has a length to height ratio between about 1 to about 20.

9. The exhaust silencer of claim 1, wherein said bifurcation delivers a shape angle of at least 140°.

10. An exhaust silencer system, comprising: an exhaust silencer device including a housing, an intake manifold, at least two exhaust outlet ports and a flow channel formed in said housing, said flow channel extend from said intake manifold to the exhaust outlet ports in a bifurcated configuration; and a turbogenerator coupled to said intake manifold, said turbogenerator supplying exhaust to said exhaust silencer device.

11. The exhaust silencer system of claim 10, wherein said bifurcated configuration is substantially T-shaped.

12. The exhaust silencer system of claim 10, wherein the diameter of said flow channel are based on the length such that a compact fluid flow profile is formed.

13. The exhaust silencer system of claim 10, wherein said flow channel has a length to height ratio from about 1 to about 20.

14. The exhaust silencer system of claim 10, wherein sound attenuating material is disposed within said housing.

15. The exhaust silencer system of claim 14, wherein said sound attenuating material is selected from the group consisting of fiberglass, mineral wool and ceramic wool.

16. The exhaust silencer system of claim 14, wherein the sound attenuating material is in a form selected form the group consisting of woven material, blankets and blown material.

17. A method for silencing exhaust flow associated with a turbo generator, comprising: directing exhaust flow into an intake manifold; and directing said exhaust flow from said intake manifold to at least two exhaust outlet ports via a flow channel; wherein said exhaust flow is bifurcated between said intake manifold and said at least two exhaust outlet ports such that said exhaust flow includes a compact fluid flow profile.

18. The method of claim 15, wherein the bifurcated flow forms a shape angle of at least 140°.

19. The method of claim 15, wherein said flow channel has a length to height ratio of between about 1 and about 20.

20. The method of claim 15, wherein said flow channel has a length to diameter ratio of between about 1 and about 20.

Description:

CROSS REFERENECE TO RELATED APPLICATIONS

[0001] This patent application claims priority under 35 U.S.C. 119 to provisional application serial No. 60/245,700, filed Nov. 2, 2000, the contents of which are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to exhaust silencers. More particularly, the invention relates to exhaust silencers for use with turbogenerator systems.

[0004] 2. Discussion of the Background

[0005] The present inventors recognized that exhaust silencers for use with turbogenerator systems should be compact, provide a low profile, have a high noise reduction efficiency, include easy installation to a turbogenerator system, and have an aesthetic design which compliments the turbogenerator system.

SUMMARY OF THE INVENTION

[0006] The invention provides a novel exhaust silencer device, comprising:

[0007] a housing;

[0008] an intake wall and an exhaust wall disposed within said housing and forming a flow channel;

[0009] an intake manifold formed within said intake wall; and

[0010] at least two exhaust outlet ports formed within said exhaust wall;

[0011] wherein said flow channel extends from said intake manifold and is bifurcated to terminate at said two exhaust outlet ports thereby forming a substantially T-shaped configuration.

[0012] The invention also provides a novel exhaust silencer system, comprising:

[0013] an exhaust silencer device including a housing, an intake manifold, at least two exhaust outlet ports and a flow channel formed in said housing, said flow channel extend from said intake manifold to the exhaust outlet ports in a bifurcated configuration; and a turbogenerator coupled to said intake manifold, said turbogenerator supplying exhaust to said exhaust silencer device.

[0014] The invention also provides a method for silencing exhaust flow associated with a turbogenerator, comprising:

[0015] directing exhaust flow into an intake manifold; and directing said exhaust flow from said intake manifold to at least two exhaust outlet ports via a flow channel;

[0016] wherein said exhaust flow is bifurcated between said intake manifold and said at least two exhaust outlet ports such that said exhaust flow includes a compact fluid flow profile.

[0017] Additional objects and advantages of the invention will be set forth in the description which folllows, and in part will be evident from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter or by other instrumentalities and combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0019] FIG. 1A is perspective view, partially in section, of an integrated turbogenerator system;

[0020] FIG. 1B is a magnified perspective view, partially in section, of the motor/generator portion of the integrated turbogenerator of FIG. 1A;

[0021] FIG. 1C is an end view, from the motor/generator end, of the integrated turbogenerator of FIG. 1A;

[0022] FIG. 1D is a magnified perspective view, partially in section, of the combustor-turbine exhaust portion of the integrated turbogenerator of FIG. 1A;

[0023] FIG. 1E is a magnified perspective view, partially in section, of the compressor-turbine portion of the integrated turbogenerator of FIG. 1A;

[0024] FIG. 2 is a block diagram schematic of a turbogenerator system including a power controller having decoupled rotor speed, operating temperature, and DC bus voltage control loops;

[0025] FIG. 3A is a perspective view of an exhaust side of a turbogenerator exhaust silencer;

[0026] FIG. 3B is a perspective view of an intake side of the turbogenerator exhaust silencer of FIG. 3A;

[0027] FIG. 4A is a sectional view of FIG. 5 taken along line E-E illustrating a portion of flow channel without an annual forming inset;

[0028] FIG. 4B is a sectional view of FIG. 5 taken along line E-E illustrating a portion of a length of an annular shaped flow channel;

[0029] FIG. 5 is a sectional view of FIG. 3A taken along line 5-5 illustrating the flow channel;

[0030] FIG. 6 is a sectional view of a prior art turbogenerator exhaust silencer including an exhaust configuration that extends in-line with exhaust intake; and

[0031] FIG. 7 is a sectional view of a prior art turbogenerator exhaust silencer including an exhaust configuration with a geometry of substantial bends.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Referring now to the drawings, like reference numerals designate identical or corresponding parts throughout the several views.

[0033] Mechanical Structural Embodiment of a Turbogenerator

[0034] With reference to FIG. 1A, an integrated turbogenerator 1 according to the present invention generally includes motor/generator section 10 and compressor-combustor section 30. Compressor-combustor section 30 includes exterior can 32, compressor 40, combustor 50 and turbine 70. A recuperator 90 may be optionally included.

[0035] Referring now to FIG. 1B and FIG. 1C, in a currently preferred embodiment of the present invention, motor/generator section 10 may be a permanent magnet motor generator having a permanent magnet rotor or sleeve 12. Any other suitable type of motor generator may also be used. Permanent magnet rotor or sleeve 12 may contain a permanent magnet 12M. Permanent magnet rotor or sleeve 12 and the permanent magnet disposed therein are rotatably supported within permanent magnet motor/generator stator 14. Preferably, one or more compliant foil, fluid film, radial, or journal bearings 15A and 15B rotatably support permanent magnet rotor or sleeve 12 and the permanent magnet disposed therein. All bearings, thrust, radial or journal bearings, in turbogenerator 1 may be fluid film bearings or compliant foil bearings. Motor/generator housing 16 encloses stator heat exchanger 17 having a plurality of radially extending stator cooling fins 18. Stator cooling fins 18 connect to or form part of stator 14 and extend into annular space 10A between motor/generator housing 16 and stator 14. Wire windings 14W exist on permanent magnet motor/generator stator 14.

[0036] Referring now to FIG. 1D, combustor 50 may include cylindrical inner wall 52 and cylindrical outer wall 54. Cylindrical outer wall 54 may also include air inlets 55. Cylindrical walls 52 and 54 define an annular interior space 50S in combustor 50 defining an axis 51. Combustor 50 includes a generally annular wall 56 further defining one axial end of the annular interior space of combustor 50. Associated with combustor 50 may be one or more fuel injector inlets 58 to accommodate fuel injectors which receive fuel from fuel control element 50P as shown in FIG. 2, and inject fuel or a fuel air mixture to interior of 50S combustor 50. Inner cylindrical surface 53 is interior to cylindrical inner wall 52 and forms exhaust duct 59 for turbine 70.

[0037] Turbine 70 may include turbine wheel 72. An end of combustor 50 opposite annular wall 56 further defines an aperture 71 in turbine 70 exposed to turbine wheel 72. Bearing rotor 74 may include a radially extending thrust bearing portion, bearing rotor thrust disk 78, constrained by bilateral thrust bearings 78A and 78B. Bearing rotor 74 may be rotatably supported by one or more journal bearings 75 within center bearing housing 79. Bearing rotor thrust disk 78 at the compressor end of bearing rotor 76 is rotatably supported preferably by a bilateral thrust bearing 78A and 78B. Journal or radial bearing 75 and thrust bearings 78A and 78B may be fluid film or foil bearings.

[0038] Turbine wheel 72, Bearing rotor 74 and Compressor impeller 42 may be mechanically constrained by tie bolt 74B, or other suitable technique, to rotate when turbine wheel 72 rotates. Mechanical link 76 mechanically constrains compressor impeller 42 to permanent magnet rotor or sleeve 12 and the permanent magnet disposed therein causing permanent magnet rotor or sleeve 12 and the permanent magnet disposed therein to rotate when compressor impeller 42 rotates.

[0039] Referring now to FIG. 1E, compressor 40 may include compressor impeller 42 and compressor impeller housing 44. Recuperator 90 may have an annular shape defined by cylindrical recuperator inner wall 92 and cylindrical recuperator outer wall 94. Recuperator 90 contains internal passages for gas flow, one set of passages, passages 33 connecting from compressor 40 to combustor 50, and one set of passages, passages 97, connecting from turbine exhaust 80 to turbogenerator exhaust output 2.

[0040] Referring again to FIG. 1B and FIG. 1C, in operation, air flows into primary inlet 20 and divides into compressor air 22 and motor/generator cooling air 24. Motor/generator cooling air 24 flows into annular space 10A between motor/generator housing 16 and permanent magnet motor/generator stator 14 along flow path 24A. Heat is exchanged from stator cooling fins 18 to generator cooling air 24 in flow path 24A, thereby cooling stator cooling fins 18 and stator 14 and forming heated air 24B. Warm stator cooling air 24B exits stator heat exchanger 17 into stator cavity 25 where it further divides into stator return cooling air 27 and rotor cooling air 28. Rotor cooling air 28 passes around stator end 13A and travels along rotor or sleeve 12. Stator return cooling air 27 enters one or more cooling ducts 14D and is conducted through stator 14 to provide further cooling. Stator return cooling air 27 and rotor cooling air 28 rejoin in stator cavity 29 and are drawn out of the motor/generator 10 by exhaust fan 11 which is connected to rotor or sleeve 12 and rotates with rotor or sleeve 12. Exhaust air 27B is conducted away from primary air inlet 20 by duct 10D.

[0041] Referring again to FIG. 1E, compressor 40 receives compressor air 22. Compressor impeller 42 compresses compressor air 22 and forces compressed gas 22C to flow into a set of passages 33 in recuperator 90 connecting compressor 40 to combustor 50. In passages 33 in recuperator 90, heat is exchanged from walls 98 of recuperator 90 to compressed gas 22C. As shown in FIG. 1E, heated compressed gas 22H flows out of recuperator 90 to space 35 between cylindrical inner surface 82 of turbine exhaust 80 and cylindrical outer wall 54 of combustor 50. Heated compressed gas 22H may flow into combustor 54 through sidewall ports 55 or main inlet 57. Fuel (not shown) may be reacted in combustor 50, converting chemically stored energy to heat. Hot compressed gas 51 in combustor 50 flows through turbine 70 forcing turbine wheel 72 to rotate. Movement of surfaces of turbine wheel 72 away from gas molecules partially cools and decompresses gas 51D moving through turbine 70. Turbine 70 is designed so that exhaust gas 107 flowing from combustor 50 through turbine 70 enters cylindrical passage 59. Partially cooled and decompressed gas in cylindrical passage 59 flows axially in a direction away from permanent magnet motor/generator section 10, and then radially outward, and then axially in a direction toward permanent magnet motor/generator section 10 to passages 98 of recuperator 90, as indicated by gas flow arrows 108 and 109 respectively.

[0042] In an alternate embodiment of the present invention, low pressure catalytic reactor 80A may be included between fuel injector inlets 58 and recuperator 90. Low pressure catalytic reactor 80A may include internal surfaces (not shown) having catalytic material (e.g., Pd or Pt, not shown) disposed on them. Low pressure catalytic reactor 80A may have a generally annular shape defined by cylindrical inner surface 82 and cylindrical low pressure outer surface 84. Unreacted and incompletely reacted hydrocarbons in gas in low pressure catalytic reactor 80A react to convert chemically stored energy into additional heat, and to lower concentrations of partial reaction products, such as harmful emissions including nitrous oxides (NOx).

[0043] Gas 110 flows through passages 97 in recuperator 90 connecting from turbine exhaust 80 or catalytic reactor 80A to turbogenerator exhaust output 2, as indicated by gas flow arrow 112, and then exhausts from turbogenerator 1, as indicated by gas flow arrow 113. Gas flowing through passages 97 in recuperator 90 connecting from turbine exhaust 80 to outside of turbogenerator 1 exchanges heat to walls 98 of recuperator 90. Walls 98 of recuperator 90 heated by gas flowing from turbine exhaust 80 exchange heat to gas 22C flowing in recuperator 90 from compressor 40 to combustor 50.

[0044] Turbogenerator 1 may also include various electrical sensor and control lines for providing feedback to power controller 201 and for receiving and implementing control signals as shown in FIG. 2.

[0045] Alternative Mechanical Structural Embodiments of the Integrated Turbogenerator

[0046] The integrated turbogenerator disclosed above is exemplary. Several alternative structural embodiments are known.

[0047] In one alternative embodiment, air 22 may be replaced by a gaseous fuel mixture. In this embodiment, fuel injectors may not be necessary. This embodiment may include an air and fuel mixer upstream of compressor 40.

[0048] In another alternative embodiment, fuel may be conducted directly to compressor 40, for example by a fuel conduit connecting to compressor impeller housing 44. Fuel and air may be mixed by action of the compressor impeller 42. In this embodiment, fuel injectors. may not be necessary.

[0049] In another alternative embodiment, combustor 50 may be a catalytic combustor.

[0050] In another alternative embodiment, geometric relationships and structures of components may differ from those shown in FIG. 1A. Permanent magnet motor/generator section 10 and compressor/combustor section 30 may have low pressure catalytic reactor 80A outside of annular recuperator 90, and may have recuperator 90 outside of low pressure catalytic reactor 80A. Low pressure catalytic reactor 80A may be disposed at least partially in cylindrical passage 59, or in a passage of any shape confined by an inner wall of combustor 50. Combustor 50 and low pressure catalytic reactor 80A may be substantially or completely enclosed with an interior space formed by a generally annularly shaped recuperator 90, or a recuperator 90 shaped to substantially enclose both combustor 50 and low pressure catalytic reactor 80A on all but one face.

[0051] Alternative Use of the Invention Other than in Integrated Turbogenerators

[0052] An integrated turbogenerator is a turbogenerator in which the turbine, compressor, and generator are all constrained to rotate based upon rotation of the shaft to which the turbine is connected. The invention disclosed herein is preferably but not necessarily used in connection with a turbogenerator, and preferably but not necessarily used in connection with an integrated turbogenerator.

[0053] Turbogenerator System Including Controls

[0054] Referring now to FIG. 2, a preferred embodiment is shown in which a turbogenerator system 200 includes power controller 201 which has three substantially decoupled control loops for controlling (1) rotary speed, (2) temperature, and (3) DC bus voltage. A more detailed description of an appropriate power controller is disclosed in U.S. patent application Ser. No. 09/207,817, filed Dec. 12, 1998 in the names of Gilbreth, Wacknov and Wall, and assigned to the assignee of the present application which is incorporated herein in its entirety by this reference.

[0055] Referring still to FIG. 2, turbogenerator system 200 includes integrated turbogenerator 1 and power controller 201. Power controller 201 includes three decoupled or independent control loops.

[0056] A first control loop, temperature control loop 228, regulates a temperature related to the desired operating temperature of primary combustor 50 to a set point, by varying fuel flow from fuel control element 50P to primary combustor 50. Temperature controller 228C receives a temperature set point, T*, from temperature set point source 232, and receives a measured temperature from temperature sensor 226S connected to measured temperature line 226. Temperature controller 228C generates and transmits over fuel control signal line 230 to fuel pump 50P a fuel control signal for controlling the amount of fuel supplied by fuel pump 50P to primary combustor 50 to an amount intended to result in a desired operating temperature in primary combustor 50. Temperature sensor 226S may directly measure the temperature in primary combustor 50 or may measure a temperature of an element or area from which the temperature in the primary combustor 50 may be inferred.

[0057] A second control loop, speed control loop 216, controls speed of the shaft common to the turbine 70, compressor 40, and motor/generator 10, hereafter referred to as the common shaft, by varying torque applied by the motor generator to the common shaft. Torque applied by the motor generator to the common shaft depends upon power or current drawn from or pumped into windings of motor/generator 10. Bi-directional generator power converter 202 is controlled by rotor speed controller 216C to transmit power or current in or out of motor/generator 10, as indicated by bi-directional arrow 242. A sensor in turbogenerator 1 senses the rotary speed on the common shaft and transmits that rotary speed signal over measured speed line 220. Rotor speed controller 216 receives the rotary speed signal from measured speed line 220 and a rotary speed set point signal from a rotary speed set point source 218. Rotary speed controller 216C generates and transmits to generator power converter 202 a power conversion control signal on line 222 controlling generator power converter 202's transfer of power or current between AC lines 203 (i.e., from motor/generator 10) and DC bus 204. Rotary speed set point source 218 may convert to the rotary speed set point a power set point P* received from power set point source 224.

[0058] A third control loop, voltage control loop 234, controls bus voltage on DC bus 204 to a set point by transferring power or voltage between DC bus 204 and any of (1) Load/Grid 208 and/or (2) energy storage device 210, and/or (3) by transferring power or voltage from DC bus 204 to dynamic brake resistor 214. A sensor measures voltage DC bus 204 and transmits a measured voltage signal over measured voltage line 236. Bus voltage controller 234C receives the measured voltage signal from voltage line 236 and a voltage set point signal V* from voltage set point source 238. Bus voltage controller 234C generates and transmits signals to bi-directional load power converter 206 and bi-directional battery power converter 212 controlling their transmission of power or voltage between DC bus 204, load/grid 208, and energy storage device 210, respectively. In addition, bus voltage controller 234 transmits a control signal to control connection of dynamic brake resistor 214 to DC bus 204.

[0059] Power controller 201 regulates temperature to a set point by varying fuel flow, adds or removes power or current to motor/generator 10 under control of generator power converter 202 to control rotor speed to a set point as indicated by bi-directional arrow 242, and controls bus voltage to a set point by (1) applying or removing power from DC bus 204 under the control of load power converter 206 as indicated by bi-directional arrow 244, (2) applying or removing power from energy storage device 210 under the control of battery power converter 212, and (3) by removing power from DC bus 204 by modulating the connection of dynamic brake resistor 214 to DC bus 204.

[0060] Turbogenerator exhaust silencers are generally single path and are controlled by a length to passage height ratio of an exhaust path. The exhaust path extends from an intake manifold to an exhaust outlet port. A large length to diameter (L/D) ratio provides a low and compact fluid profile. A substantially C-shaped, exhaust path allows exhaust flow to move in one direction and curve back in an opposite second direction. An exhaust path with substantial bends causes undesired back pressure problems with the exhaust flow.

[0061] Referring now to FIGS. 3A, 3B, and 5, they illustrate one embodiment of an exhaust silencer system 300 of the present invention. Exhaust silencer system 300 includes housing 302, intake manifold 303, first exhaust outlet port 304 and second exhaust outlet port 306.

[0062] Housing 302 includes top wall 308, bottom wall 310, first side wall 312, second side wall 314, exhaust wall 316 and intake wall 318.

[0063] Referring to FIG. 5, a sound attenuating material 315 is coupled to exhaust wall 316 and intake wall 318. However, it should be appreciated that sound attenuating material may be positioned anywhere within or around housing 302 in an appropriate configuration. Two exemplary sound attenuating materials are fiberglass and mineral wool also ceramic wool or any other fiberous bulk material used for acoustic damping purposes. Sound attenuating material may be woven, formed as blankets or blown into the exhaust silence system 300.

[0064] Exhaust wall 316 and intake wall 318 are sized and shaped to define a bifurcated cavity which forms ducting or flow channels 320, 322. Flow channels 320, 322 are each continuous from exhaust wall 316 to intake wall 318. Flow channels 320, 322 extend from intake manifold 303, and terminate at first exhaust outlet port 304 and second exhaust outlet port 306 which are formed as elbow shaped portions. Intake manifold 303 is sized and shaped for coupling to an exhaust of a turbogenerator.

[0065] Intake wall 318 and flow channels 320, 322 form a substantially “T-shaped” configuration through which fluid flows. For example, the “T-shaped” configuration permits flow channels 320, 322 to extend from intake manifold 303 in a substantially orthogonal direction from center axis B-B (FIG. 5) of intake manifold 303 such that fluid enters intake manifold 303 and is directed outward to first exhaust outlet port 304 and second exhaust outlet port 306. Exhaust outlet ports 304, 306 are spaced apart by an “effective length” indicated by two headed arrows on line E-E.

[0066] Exhaust silencer 300 may also include turning vanes 332, 334, 336 and 338. Turning vanes 332, 338 reduce pressure losses in the elbow bends near first exhaust outlet port 304 and second exhaust outlet port 306. Turning vanes 334, 336 reduce the pressure losses at the flow splitter 324.

[0067] Exhaust silencer 300 may also include annular forming insets 452a, 452b. However, it should be appreciated that insets may be any appropriate shape that compliments the flow channels.

[0068] First exhaust outlet port 304 and second exhaust outlet port 306 may have any appropriate covering 314 through which the fluid can flow. One exemplary covering 314 is a screen material that filters the fluid flow. Covering 314 prevents debris from collecting in the silencer and small animals such as birds and rodents from nesting within.

[0069] Exhaust flow is directed through bifurcated flow channels 320, 322 which provide an “effective length”, indicated by two-headed arrows on line E-E. The effective length is the total length which is treated with acoustic material and through which exhaust flows from the intake to the outlet. The effective length may be a length from the intake to the outlet in the exhaust silencer. Effective lengths useful for this invention are between about 2 and 10 centimeters.

[0070] In a configuration of bifurcated flow channels, although the flow is divided, the “effective length” is the total length through which fluid flows. Therefore, the “effective length” indicated by two-headed arrows on line E-E provides a length of a magnitude comparable to the substantially straight exhaust silencer configuration having a flow path of length E-E. The bifurcation of the flow channel into paths 318-320, and 318-322, minimize profile problems for a given effective length.

[0071] Modifying the configuration of the effective length changes the fluid flow profile. Accordingly, particular configurations or geometries may be selected based on desired fluid flow characteristics. The substantially “T-shaped” configuration of flow channels 320, 322 results in a fluid profile of silencer system 300 that is low and compact. Additionally, the bifurcation of the exhaust flow into the flow channels 320, 322 creates a predetermined L/H ratio a minimal length extending in an outwardly direction from the intake manifold. The flow channels 320, 322 need not be exactly T-shaped. There may be same degree of angle between flow channels 320, 322 that results in a “Y-shape.” The shape of the angle between the flow channels 320, 322 is 180° in the “T-shape” and less than 180° in the “Y-shape.” Shape angles greater than 140° are preferred, and angles greater than 160° are more preferred. Flow channels angles are also selected to minimize drain water flow into the engine and direct water to gutters 340a, 340b.

[0072] The exhaust flow path is three-dimensional and has a cross sectional area. A minimum cross sectional area is necessary to minimize pressure losses in the exhaust ducting. A larger cross sectional area of the ducting reduces the average velocity in the exhaust flow path, and therefore reduces the pressure losses which are generally a function of velocity squared. Exemplary cross sections include, but are not limited to, a rectangular cross-section, a circular cross section, or an annular cross section.

[0073] Referring now to FIG. 4A, it illustrates a sectional view of one portion of a bifurcated passage including an exhaust path 400 with treatment 410. The exhaust flow is directed along the path in a direction shown by arrow F. The rectangular cross section (not shown) has the dimensions of a height H and a width W and an area represented by the H multiplied by W. The area of a circular ducting (not shown) is a function of its diameter. A portion of the effective length is indicated by two-headed arrows on line E.

[0074] Referring now to FIG. 4B, it illustrates a sectional view of one portion of a bifurcated passage including an exhaust flow path 450 with annular forming inset 452 and acoustic treatment material 454. The exhaust path flow begins with a diameter indicated by two-headed arrow D2 and continues to annular inset 452 with a diameter D1. Annular forming inset 452 may be made of an acoustic treatment material or any other appropriate material. Annular forming inset 452 forms a dual pathway 454, 456 for exhaust flow. The exhaust flow is directed along the path in a direction shown by arrow F. The cross sectional area (not shown) is based on the diameter. A portion of the effective length is indicated by two-headed arrows on line G.

[0075] Referring again to FIG. 5, the bifurcation of the exhaust flow permits a reduction in the height H for a rectangular cross section or in the diameter D for a circular cross section of the silencer to yield a lower profile. Bifurcating the exhaust results in about a half of the flow directed into each path 318-320 and 318-322. Thus, the average velocity of the fluid in each duct having a height of about ½ the height of an unbifurcated path, is comparably similar to the average velocity in the unbifurcated path.

[0076] Exhaust silencer 300 minimizes acoustic vibrations because the length, L, relative to the diameter D for circular ducts, the height H for annular ducts, and the smaller of height H and width W for rectangular ducts, is compared to the effective length. The height (H) of the exhaust channels 304, 306 (or at least the length in one dimension thereof for noncircular cross sections) are sized depending on the length (L) of exhaust channels, such that a high L/H ratio results. The L/H ratio is predetermined for the exhaust channels. For a rectangular or annular duct, L/H is used. For a circular silencer duct, L/D is used. The ratio of L/H (or L/D) may be used to determine the acoustic performance of the silencer. The ratio can range from 1 to 20 depending on the noise reduction goals for the silencer. One exemplary L/D ratio is 5. One preferred range is 7-10.

[0077] The depths of first exhaust outlet port 304 and second exhaust outlet port 306 are also selected to improve the low frequency characteristics of the exhaust silencer and optimize for spectral acoustic characteristics of the turbogenerator exhaust system. The depth of the exhaust port is the length from the aperture of, e.g., exhaust outlet port 304 to the intersection with flow channel 322 which forms a elbow shaped bend.

[0078] Referring to FIG. 6, it illustrates a prior art exhaust silencer configuration 600 in which a substantially straight exhaust path extends an “outward length” from exhaust outlet port 604 along axis C-C. Exhaust flow directed in this manner will result in undesired profile problems.

[0079] Referring to FIG. 7, it illustrates a prior art exhaust silencer configuration 700 in which substantially curved exhaust path 702 extends from exhaust outlet port 704. Exhaust flow directed in this manner will result in undesired backpressure problems.

[0080] Comparatively, bifurcating the exhaust flow path into flow paths 320 and 322 doubles the “effective length” without requiring excessive bends that elevate backpressure to an undesirable magnitude.

[0081] Referring again to FIG. 5, it illustrates the bifurcated exhaust flow directed via flow channels 320, 322, which provides improved acoustic damping efficiency. Although a substantially “T-shaped” configuration is shown, it should be appreciated that any suitable bifurcated configuration may be selected which provides a low and compact flow.

[0082] Numerous modifications and variations of the present invention are possible in light of the above teachings. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit and scope of the general inventive concept as defined by the appended claims and their equivalent.