CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application is being filed on 13 March 2014, as a PCT International Patent application and claims priority to U.S. Patent Application Serial No. 61/793,499 filed on 1 March 2013, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Roots-type devices are volumetric devices that output a fixed volume of fluid per rotation. In some instances, roots-type devices are used in supercharger systems as blowers to boost the pressure of fluid provided to a power source such as an internal combustion engine or a fuel cell. In other applications, the roots-type devices are used as expanders to extract energy from waste heat from a power source that would otherwise be wasted, such as an exhaust stream from a fuel cell, a working fluid that extracts heat from an internal combustion engine, or an exhaust fluid stream from an internal combustion engine. In all scenarios, there is noise associated with the passage of fluid through the roots-type devices.

SUMMARY

[0003] In one aspect, a volumetric assembly includes: a roots-type supercharger device having at least two supercharger rotors, with each of the rotors having two or more lobes, the roots-type supercharger defining a supercharger fluid inlet and a supercharger fluid outlet; a roots-type expander device having at least two expander rotors, with each of the rotors having two or more lobes, the roots-type expander defining an expander fluid inlet and an expander fluid outlet; a first duct extending from the supercharger fluid inlet, the first duct supplying fluid to the roots-type supercharger device; and a second duct extending from the expander fluid outlet, the second duct directing fluid away from the roots-type expander device, wherein the first duct is positioned adjacent to the second duct, and wherein the first duct defines a first aperture and the second duct defines a second aperture, the first and second apertures being generally aligned; and a flexible membrane positioned between the first and second ducts in the first and second apertures, the flexible membrane sealing the first duct from the second duct, and the flexible membrane flexing as fluid flows within the first and second ducts to attenuate noise associated with the fluid flows.

[0004] In another aspect, a system includes: a power source; and a volumetric assembly, the volumetric assembly including: a roots-type supercharger device having at least two supercharger rotors, with each of the rotors having two or more lobes, the roots-type supercharger defining a supercharger fluid inlet and a supercharger fluid outlet, the supercharger fluid outlet being connected to the power source to provide fluid for boosting the power source; a roots-type expander device having at least two expander rotors, with each of the rotors having two or more lobes, the roots-type supercharger defining an expander fluid inlet and an expander fluid outlet, the expander fluid inlet being coupled to a working fluid or an exhaust of the power source to provide fluid to the expander fluid inlet, and the roots-type expander device applying torque to the power source; a first duct extending from the supercharger fluid inlet, the first duct supplying fluid to the roots-type supercharger device; and a second duct extending from the expander fluid outlet, the second duct directing fluid away from the roots-type expander device, wherein the first duct is positioned adjacent to the second duct, and wherein the first duct defines a first aperture and the second duct defines a second aperture, the first and second apertures being generally aligned; and a flexible membrane positioned between the first and second ducts in the first and second apertures, the flexible membrane sealing the first duct from the second duct, and the flexible membrane flexing as fluid flows within the first and second ducts to attenuate noise associated with the fluid flows.

[0005] In yet another aspect, a method of boosting a power plant and recovering energy from waste heat of the power plant includes: providing a roots-type supercharger device to boost the power plant, the roots-type supercharger having an inlet duct;

providing a roots-type expander device to recover energy from the exhaust of the power plant, the roots-type expander device having an outlet duct; positioning the inlet duct adjacent to the outlet duct; and configuring a membrane positioned in an aperture between the inlet and outlet ducts to flex as pressure changes within the inlet and outlet ducts.

[0006] The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIGURE 1 is a schematic illustration of a system including a power plant and a volumetric device.

[0008] FIGURE 2 is a perspective view of an example volumetric supercharger device of the system of Figure 1.

[0009] FIGURE 3 is a schematic illustration of rotors of the volumetric

supercharger device of Figure 2.

[0010] FIGURE 4 is a cross-sectional view of an example volumetric expander device of the system of Figure 1.

[0011] FIGURE 5 is a schematic illustration of rotors of the volumetric expander device of Figure 4.

[0012] FIGURE 6 is a perspective view of the volumetric assembly of Figure 1.

[0013] FIGURE 7 is a schematic view of a portion of the volumetric assembly of Figure 6.

[0014] FIGURE 8 is a schematic view of an example flexible member of the volumetric assembly of Figure 7.

[0015] FIGURE 9 is a schematic illustration of another system.

[0016] FIGURE 10 is a schematic illustration of the noise cancellation operation of the system shown in Figure 1.

DETAILED DESCRIPTION

[0017] Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, Figure 1 shows an example system 100 including a power source 102, such as an internal combustion engine or a fuel cell, and a volumetric assembly 104 coupled thereto.

[0018] The power source 102 is used to power various devices, such as a vehicle. In one embodiment, a fuel cell is used as the power source.

[0019] The volumetric assembly 104 includes a volumetric supercharger device 110 and a volumetric expander device 112. Both devices 110, 112 are roots-type devices. Roots-type devices are fixed displacement devices that output a fixed volume of fluid per rotation.

[0020] Referring to Figures 2-3, in this example, the volumetric supercharger device 110 (sometimes referred to as a "supercharger" or "blower") is used to pump fluid from the atmosphere to the power source 102. The supercharger is used to boost a pressure of the fluid that is delivered to the power source 102, increasing oxygen which allows more fuel. This enhances performance of the power source 102. The same is true for a fuel cell, except the electrical output increases.

[0021] The example volumetric supercharger device 110 includes two rotors 220, 222. The rotors 220, 222 are helical in configuration and rotate relative to one another in a coordinated fashion. Fluid provided at a fluid inlet 210 of the volumetric supercharger device 110 is pumped by the volumetric supercharger device 110 and delivered via an outlet 212 to the power source 102. Torque provided by the power source 102 or other external energy sources causes the volumetric supercharger device 110 to rotate.

[0022] In this example, each of the rotors 220, 222 has four lobes 224. These lobes 224 intermesh as the rotors 220, 222 spin to pump the fluid through the volumetric supercharger device 110. More or fewer lobes can be used.

[0023] One non-limiting example of a volumetric supercharger device is described in International Patent Application No. PCT/US 12/40736 filed on June 4, 2012, the entirety of which is hereby incorporated by reference. Other configurations are possible.

[0024] Referring now to Figures 4-5, the example volumetric expander device 112 (sometimes referred to as an "expander") includes two rotors 320, 322. The rotors 320, 322 are helical in configuration and rotate relative to one another in a coordinated fashion. Fluid provided at a fluid inlet 310 of the volumetric expander device 112 causes the rotors 320, 322 to spin as the fluid moves through the volumetric expander device 112 to an outlet 312. Typically, this fluid is derived from exhaust gases of the power source 102 and includes either exhaust gases or other fluids derived from a Rankine cycle. The use and operation of a volumetric expander in a Rankine cycle is described in published PCT International Patent Application WO 2013/130774, the entirety of which is incorporated by reference herein. Torque generated by the volumetric expander device 112 is delivered to the power source 102 or other components.

[0025] In one design including a fuel cell, a compressor provides oxygen to the fuel cell stack. The higher the pressure, the greater the concentration of oxygen, so if the hydrogen fuel is increased to the fuel cell stack the amount of electricity generated increases. To recoup some of the energy used by the compressor in providing high pressure to the fuel cell stack, an expander can be used. The expander, which is attached directly to the roots compressor, controls the pressure built up in the fuel cell stack.

[0026] In this example, each of the rotors 320, 322 has two lobes 324. These lobes 324 intermesh as the rotors 320, 322 spin. More or fewer lobes can be used.

[0027] One non-limiting example of a volumetric expander device is described in International Patent Application No. PCT/US 13/28273 filed on February 28, 2013, the entirety of which is hereby incorporated by reference. Other configurations are possible.

[0028] Referring now to Figures 6-8, the volumetric assembly 104 is shown again. In this example, the fluid inlet 210 of the volumetric supercharger device 110 is connected to an inlet duct 510 that passes fluid through a passage 512 formed by the inlet duct 510 and into the volumetric supercharger device 110. In addition, the fluid outlet 312 of the volumetric expander device 112 is connected to an outlet duct 520 so that fluid from the volumetric expander device 112 passes through a passage 522 as the fluid exits the volumetric expander device 112.

[0029] As shown in Figures 7-8, the ducts 510, 512 are positioned to converge so that the ducts 510, 512 abut one another. The duct 510 includes an aperture 516 and the duct 520 includes an aperture 526 that generally align with one another as the ducts 510, 512 abut. A flexible membrane 610 is positioned within these apertures 516, 526 to close the apertures 516, 526 so that fluid passing through the passage 512 does not mix with fluid passing through the passage 522.

[0030] In this example, the volumetric assembly 104 is controlled so that the pressure waves at the flexible membrane 610 are generally 180 degrees out of phase with each other. In other words, the volumetric supercharger device 110 and the volumetric expander device 112 are controlled so that the inlet pressure for the volumetric supercharger device 110 is generally 180 degrees out of phase with the outlet pressure for the volumetric expander device 112. Referring to Figure 10, schematic graphical depictions of the frequency and amplitude of the cyclical inlet pressure 1002 of the volumetric supercharger device 110 and the cyclical outlet pressure 1004 of the outlet pressure for the volumetric expander device 1112. As can be seen, the inlet pressure 1002 is shown as being 180 degrees out of phase with the outlet pressure 1004, wherein the inlet and outlet pressure 1002, 1004 have the same amplitude and frequency. The resulting additive combination of the inlet and outlet pressure 1002, 1004 is shown at pressure line 1006 which is shown as being completely flat as the inlet and outlet pressures 1002, 1004 completely cancel each other out. It is noted that pressure line 1006, which is reflective of any remaining non-cancelled sound, may have a non-zero value where the inlet and outlet pressure 1002, 1004 do not completely cancel each other out. The addition of the oscillating inlet and outlet pressures 1002, 1004 will not cancel each other out completely if the amplitudes are different, if the frequency is different, and/or the phases are not fully out of phase with each other. Also, cancellation may not occur in certain instances where the

supercharger rotors and the expander rotors have a different number of lobes. In one example, a four lobe compressor used in conjunction with a four lobe expander running at half the speed of the compressor will result in only half of the noise being cancelled if the pressure amplitudes are the same.

[0031] In such a configuration, noise associated with the fluids flowing through the ducts 510, 520 can be attenuated. Specifically, some of the kinetic energy from the fluids flowing through one of the ducts 510, 520 is transferred to the other of the ducts 510, 520 through the flexible membrane at given periods of time to attenuate noise. [0032] In order to accomplish the attenuation, the number of lobes of the rotors for each volumetric device is equal if the speed (i.e., revolutions per minute) is equal. If one volumetric device runs more quickly than the other, then the number of lobes must be varied such that the ratio of the speed equals the ratio of the lobes.

[0033] For example, in the depicted embodiment, the volumetric supercharger device 110 has four lobes 224 per rotor 220, 222, and the volumetric expander device 112 has two lobes 324 per rotor 320, 322. In such a configuration, the volumetric expander device 112 is run at twice the speed of the volumetric supercharger device 110

[0034] The flexible member 610 is located near the volumetric assembly 104, so that temperature and pressure in each of the ducts 510, 520 will generally be the same. This will make the wavelength at the pulsation frequency very close to the same in each of the ducts 510, 520.

[0035] The flexible membrane 610 is, in this example, capable of handling 1 to 2 psi pressure inputs and is generally acoustically transparent (i.e., has a high degree of flexibility) to allow as much communication between the ducts 510, 520 as possible. The material for the flexible membrane 610 is configured to be soft (flexible) but also be tough. One possible example of such as material is Mylar. Other polymeric materials can be used.

[0036] The flexible member 610 can be configured with circumferential folds to allow for a large degree of motion. For example, the flexible member 610 includes folds 624 located at ends 622 of the flexible member 610 that are attached to the ducts 510, 520. This allow for maximum flex for the flexible member 610 when mounted to the ducts 510, 520. Other configurations are possible.

[0037] Referring now to Figure 9, an alternative example system 700 is shown. The system 700 can be used in conjunction with an internal combustion engine or a fuel cell, as described above.

[0038] The system 700 includes an inlet 702 coupled to a roots expander. The inlet 702 leads into a main pipe 706. The main pipe 706 is, in turn, connected to an outlet 704. The path formed by 702, 706, 704 allows the fluid from the expander to flow therethrough. [0039] As shown, the main pipe 706 surrounds a second set of pipes. This second set of pipes includes an inlet pipe 710 and an outlet pipe 712. The outlet pipe 712 is connected to the inlet of the roots compressor.

[0040] Positioned between the inlet and outlet pipes 710, 712 is a flexible membrane 720. This flexible membrane 720 functions in a similar manner to the flexible member 610 described above. By controlling the timing of the flow of fluids through the two passages (as described above), the flexible membrane 720 can provide noise cancelation benefits.

[0041] Alternative designs can be used. For example, in one alternative embodiment, the ducts are located a distance apart, and a "Tee" duct or tube is run therebetween. One or more flexible membrane is positioned in the Tee duct to provide the acoustical performance. A length of the Tee duct can be varied to achieve the desired acoustical performance for a given application. For example, the length of the tube may be adjusted to adjust the distance from the source to the cancellation membrane to ensure that the pressures are 180 degrees out of phase. Other examples are possible.

[0042] While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.