WO2016200841A1

WO2016200841A1 - Engine exhaust noise reduction system

Info

Publication number: WO2016200841A1
Application number: PCT/US2016/036269
Authority: WO
Inventors: Henry K. Obermeyer
Original assignee: Obermeyer Henry K
Priority date: 2015-06-07
Filing date: 2016-06-07
Publication date: 2016-12-15

Abstract

The present invention is an active internal combustion engine exhaust noise reduction system optionally capable of harvesting acoustic energy from the exhaust stream. Salient features include at least one controllably movable reaction element, preferably designed to minimize exhaust back pressure while converting pressure and velocity variations to electrical energy.

Description

ENGINE EXHAUST NOISE REDUCTION SYSTEM

This application is an international application and claims the benefit of and priority to United States Provisional Application No. 62/172,202, filed June 7, 2015, hereby incorporated by reference

Field of the Invention

The present invention relates to active noise cancellation of the exhaust of internal combustion engines and also relates to the recovery of exhaust gas acoustic energy. Exhaust gas mufflers have been used since the advent of the internal combustion engine, however such mufflers simply convert acoustic energy into heat and also generally increase the back pressure on the engine exhaust manifold and thereby reduce engine power.

Energy harvesting devices exist that convert vibration, noise, and ambient electromagnetic energy into usable electrical power, however there appear to be no such devices designed to serve as the primary noise reduction means on the exhaust system of an internal combustion engine.

Summary of the Invention

The present invention includes pressure sensors or microphones to measure the instantaneous exhaust pressure. This measurement is used to control the velocity, position, and phase angle of a reaction surface by means of a voice coil drive circuit using insulated gate bi-polar transistors (IGBT's), for example. The voice coil is analogous to the voice coil of a loudspeaker and is likewise situated in a radial magnetic field so as to serve as a linear motor to drive a "reaction surface". The reaction surface is a sculpted surface design to substantially change the direction of flow of the exhaust gas with minimal fluid friction and with the creation of minimal backpressure. Rapid movement of the reaction surface, synchronized with the periodic exhaust gas velocity and pressure is used to remove the velocity and pressure peaks in the exhaust gas stream while filling in the gaps in exhaust gas flow and pressure. In this manner noise is removed from the exhaust gas stream while creating minimal back pressure and degradation in engine performance. Using an IGBT converter similar in function to those used for 4 quadrant motor drives allows the conversion of a portion of the absorbed acoustic energy to useful electrical power. Such electrical power may be fed into a vehicle electrical system, for example, where it can contribute to unloading the vehicle alternator and thereby contribute to net power available from the engine.

Brief Description of the Drawings

Figure 1 is a schematic of the noise reduction system and its control elements. Figure 2 is a cut away drawing of the noise reduction assembly. Figure 3 is a cut away drawing of the noise reduction assembly showing directions of gas flow. Figures 4a through 4f are drawings of the "reaction manifold". Figures 5a through 5f are drawings of the "reaction surface".

Figure 6 is a depiction of particle trajectories of exhaust gas approaching and leaving the "reaction surface" through the "reaction manifold." Figure 7 shows a cross section of one embodiment of the present invention. Figure 8 is a schematic of an embodiment of the present invention.

Detailed description of the Preferred Embodiments Referring to Figure 1, Figure 2 and Figure 3, noise reduction module 1 accepts exhaust gas 2 from internal combustion engine 3. Control module 4 senses engine timing signal 5, inlet pressure transducer 6, outlet pressure transducer 7, and baffle pressure transducer 8. Control module 4 controls IGBT converter 9 so as to absorb fluctuations in exhaust gas pressure. The IGBT converter functions in a manner similar to a 4 quadrant motor drive converter, i.e., it can send power in either direction. In this application direction of power flow and phase angle between the Voltage and current that flows between the IGBT converter and the voice coil may vary with frequency. Power flow may be toward the vehicle electrical system at low frequencies and from the vehicle electrical system at higher frequencies. It is an objective of this invention to generate rather than consume electrical power. In this manner otherwise wasted acoustic energy is converted into electrical power that would otherwise need to be provided by the engine alternator. Referring to Figure 3, exhaust gas 2 enters inlet 24 where its instantaneous pressure is measured by transducer 6. The exhaust gas then passes through acoustic wave collimator 21 which absorbs any high frequency acoustic wave components normal to the direction of gas flow and also levels out the axial lower frequency waves to create a coherent and relatively uniform wavefront. Without a uniform wavefront the sound cannot be cancelled out by application of a uniform correction by the reaction surface 14.

Referring to Figure 2 and Figure 6, voice coil 15 in conjunction with magnet 16 drives cone 23 that in turn drives reaction surface 14. Gas flow is directed to and from reaction surface 14 by reaction manifold 13. Reaction manifold 13 is comprised of partitions 25 that divide at least one inlet channel 27 from at least on outlet channel 26. The use of a plurality of narrow channels 26 and 27 prevents the propagation of lateral acoustic waves, except at very high frequencies of less importance. Noisy exhaust gas 28 with varying velocity enters the reaction manifold 13. After changing direction against rapidly moving reaction surface 14, the exhaust gas has a steady velocity and carries little acoustic energy or noise. The exhaust gas is directed through exhaust channels in the reaction manifold to exhaust plenum 22 through high frequency damper 19. The moving reaction surface absorbs energy from the exhaust stream in much the same manner as a moving turbine blade stage.

Referring to Figure 1, baffle pressurization valve 10 and baffle vent valve 11 may be used to bias the load on voice coil 15 in order to minimize electrical losses.

Referring to Figure 7, exhaust gas 2 enters through inlet pipe 53. Pipe portion 48 is an extension of inlet pipe 53. Pipe portion directs the exhaust gas 2 against reaction surface 14, causing it to reverse direction and impart a force to reaction surface 14, which is controilably movable. Periodic variations in flow and pressure acting on reaction surface 14 can be made to impart energy to reaction surface 14 and remove energy from exhaust gas 2 through control of the phase angle between the forces imparted by the flowing exhaust gas 2 and the (moving) reaction surface 14. Reaction surface 14 is connected to an energy conversion device such as a speaker coil 37 positioned with a magnet assembly 35, for example. It should be noted that alternative energy conversion devices such as piezo-electric converters, air compression pistons, hydraulic compression pistons, or the like also may be used to harvest energy fro the exhaust stream. Alternatively, a magnetic circuit may be configured to simply cause induced eddy currents in a moving conductor to convert undesirable acoustic energy into heat that may be quietly dissipated. Reaction surface 14 is preferably constructed of strong heat resistant material such as titanium of high temperature composite material. As such the mass of the reaction surface in combination with the connection means 49 to speaker coil 15 limit the maximum frequency for which acoustic to electric energy conversion is effective. Spiral baffles 46 and 47 obstruct the path of high frequency sound waves between reaction surface 14 and exhaust pipe 52. Sound waves must reflect off of perforated baffle surface 30 multiple time between reaction surface 14 and exhaust pipe 52 in conjunction with which porous packing 31 converts acoustic energy to heat. Magnet assembly 35 is cooled by vent port 45 and heat sink 15. Heat sink 15 includes radial fins 34. Other cooling means such as heat pipes, circulating fluids, or the like might also be used. Thermal insulation 56 thermally isolates magnet assembly 35 from heat in baffle chamber 44. Baffle chamber 44 may be configured to dissipate heat by the addition of cooling fins or by configuring it as a tube sheet heat exchanger, for example. It should be noted that rare earth magnet assemblies in particular must be kept cool to avoid loss of reminance, i.e., demagnetization. In conjunction with the example illustrated in Figure 7 a control system 4, pressure sensors 6, 7, and 8 as well as engine timing signals may be used to optimize performance. Further gains in performance may be attained by the addition of exhaust gas cooling means between the engine and the noise suppression system illustrated in Figure 7. In accordance with Figure 8, an example system for cooling of the exhaust gas before it reaches the noise reduction system of Figure 7. Cooling of the exhaust gas reduces the volumetric flow rate in proportion the absolute temperature of the exhaust gas. Cooling of the exhaust gas also minimizes the risk of demagnetization of the magnetic assembly, if used. Such temperature reduction may be accomplished by use of an exhaust to heat exchanger, by use of a phase change fluid, by means of liquid coolant systems, by use of Peltier junction devices, or by combinations of these. Referring again to Figure 8, internal combustion engine 3 discharges hot exhaust gas 2a into boiler 57 containing working fluid 62. Working fluid 62 condenses on Peltier effect electric generator 60. Peltier effect generator 60 is in turn cooled by working fluid 61 which in turn condenses in heat exchanger 63. Noise reduction module 58 thereby receives cooled exhaust gas 2b, with a reduced volumetric flow rate, increasing the reliability of the magnet assembly, or in some application making the use of rare earth magnets feasible. Boiler 57 may alternatively be used to run an air conditioning system, for example, that would power an ejector that would pull a vacuum off of a low temperature evaporator. Other heat driven engines might be used effectively given that a portion of their cost may be justified on the basis of their contribution to noise suppression. In accordance with a further aspect of the invention, the apparatus described may be used in conjunction with a variety of noisy gas flow apparatus including air compressors, engine inlets, and the like.

This application incorporates by reference all issued patents and published patent applications and other non-patent literature documents listed below. It also incorporates by reference general descriptions of wastewater treatment and any priority case(s) claimed by this application is hereby appended and hereby incorporated by reference. In addition, as to each term used it should be understood that unless its utilization in this application is inconsistent with a broadly supporting interpretation, common dictionary definitions should be understood as incorporated for each term and all definitions, alternative terms, and synonyms such as contained in the Random House Webster's Unabridged Dictionary, second edition are hereby incorporated by reference. Finally, all references listed below are hereby appended and hereby incorporated by reference, however, as to each of the above, to the extent that such information or statements incorporated by reference might be considered inconsistent with the patenting of this/these invention(s) such statements are expressly not to be considered as made by the applicant. US Patents

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As can be easily understood from the foregoing, the basic concepts of the present invention may be embodied in a variety of ways. The discussion included in this application is intended to serve as a basic description. The reader should be aware that the specific discussion may not explicitly describe all embodiments possible; many alternatives are implicit. It also may not fully explain the generic nature of the invention and may not explicitly show how each feature or element can actually be representative of a broader function or of a great variety of alternative or equivalent elements. Again, these are implicitly included in this disclosure. Where the invention is described in device-oriented terminology, each element of the device implicitly performs a function. Apparatus claims may not only be included for the device described, but also method or process claims may be included to address the functions the invention and each element performs. Neither the description nor the terminology is intended to limit the scope of the claims which are included in this patent application.

Claims

Claims: I claim:

1. An apparatus for converting acoustic energy in an internal combustion engine exhaust to electrical energy comprising a reaction manifold and a movable reaction surface connected to an eletromechanical transducing means.

2. An apparatus for reducing the noise of an internal combustion engine including a movable reaction surface coupled to a speaker coil in a magnetic field.

3. The apparatus of claim 2 further comprising an insulated gate bi-polar transistor converter for converting the alternating current energy from a speaker coil to direct current.

4. An apparatus for reducing the noise of an internal combustion engine including at least one magnetic circuit in conjunction with at least one movable electrically conductive element responsive to acoustic energy in the exhaust stream, wherein said electrically conductive element converts acoustic energy to electrical energy.

5. The apparatus of claim 4 wherein the at least one electrically conductive element converts acoustic energy to heat.

6. The apparatus of claim 4 wherein the exhaust gas stream is cooled by at least 50 degrees C between the internal combustion engine and the noise reduction system.

7. The apparatus of claim 5 wherein the exhaust gas stream is cooled by at least 50 degrees C between the internal combustion engine and the noise reduction system.