WO2015066479A1

WO2015066479A1 - Supercharger with modulated backflow event

Info

Publication number: WO2015066479A1
Application number: PCT/US2014/063439
Authority: WO
Inventors: Kartikeya Krishnoji MAHALATKAR; Matthew Gareld SWARTZLANDER; Sheetalkumar PATIL; Michael J. FROELICH; Gopal Kishanrao KULKARNI
Original assignee: Eaton Corporation
Priority date: 2013-10-31
Filing date: 2014-10-31
Publication date: 2015-05-07
Also published as: CN104595010B; CN104595010A; CN204646407U

Abstract

An axial inlet, radial outlet supercharger comprises a tubular housing comprising an inlet plane (IP) perpendicular to an outlet plane (OP). Rotor mounting recesses (1030, 1020) are in an inner surface of an inlet wall (1063) parallel to the inlet plane. A triangular outlet (104) is in the outlet plane. An inlet (101) is in the inlet plane. At least two axial flow backflow ports (1222) are in the inlet plane (IP). Alternatively, the supercharger comprises an inlet axis (IA). Each lobed rotor comprises a rotation axis parallel to the inlet axis (IA), wherein the lobes sequentially mesh along the inlet axis (IA) when the rotors rotate, wherein respective lobes are twisted along the length of their respective rotor, and wherein the lobes are timed to fluidly seal the inlet from the outlet. At least two backflow ports (122, 1222) are in the tubular housing.

Description

SUPERCHARGER WITH MODULATED BACKFLOW EVENT

TECHNICAL FIELD

[001] The present disclosure relates generally to a supercharger system. More specifically, a supercharger system achieving a high pressure ratio and low outlet temperature by backflowing cooled air from an intercooler to the supercharger.

BACKGROUND

[002] A supercharger can be implemented to supply compressed air to a

combustion engine. When the air is compressed, then more air can be supplied, enabling a vehicle to produce more power. There are different kinds of superchargers available, including Comprex, Roots type, twin-screw, and centrifugal. They differ in the way that air is compressed and moved to the intake manifold of the engine.

[003] The Roots type supercharger is a positive displacement pump that forces air around the outer circumference of rotors and blows the air into the manifold. Therefore, a Roots type supercharger is sometimes called a "blower." More specifically, the Roots type supercharger has two counter-rotating lobed rotors. The two rotors trap air in the gaps between rotors and push it against the housing as the rotors rotate towards the

outlet/discharge port into the engine's intake manifold. By moving air into the manifold at a higher rate than the engine consumes it, pressure is built.

[004] Because of its simple design, the Roots type supercharger is widely used. However, the Roots type supercharger has some disadvantages. When the chamber of trapped air is opened to the engine's intake manifold, the pressurized air in the engine's intake manifold reverse-flows according to thermodynamic and fluid mechanic principles into the supercharger. Further, there could be a leakage of air between the rotors due to gaps, or leakage due to gaps between the rotor lobes and housing, the gaps supplied for thermal expansion tolerances. Both reversion of air and air leakage contribute to the thermal inefficiencies of the Roots type supercharge. And, due to its nature to produce high discharge temperatures, it can take away from the engine performance. For example, when the temperature of discharged air is increased, it can cause detonation, excessive wear, or heat damage to an engine.

[005] In many positive displacement compression devices, such as reciprocating compressors, the pressure is increased by reducing the volume occupied by gas. For example, a piston physically compresses a large volume of gas into a smaller volume to increase pressure. However in a Roots device there is no mechanism like a piston to compress the gas. The Roots blower scoops the air from a low pressure suction side and moves this air to the high pressure outlet side. When the low pressure air scooped by the Roots supercharger comes in contact with the high pressure outlet side, then a backflow event takes place whereby the high pressure gas from the outlet backflows into the supercharger to compress the low pressure gas into higher pressure gas. Thus the compression of gas in the supercharger happens through this backflow event. This also heats up the compressed low pressure gas to a higher temperature based on thermodynamic principles. After compression of the gas, the blades of the Roots supercharger squeeze the compressed air out of the supercharger into the high pressure outlet side.

[006] Typically, Roots superchargers use hot high pressure air available at the outlet for the backflow event. However, it is possible to cool the Roots compressor by using relatively colder high pressure gas available after the intercooler. But, issues remain to determine the backflow slot sizing, placement, and geometry necessary to get an optimum backflow event that provides the lowest operating temperature for the supercharger while providing the highest operating efficiency.

SUMMARY

[007] In an effort to increase boost, which is given in terms of pressure ratio to the engine, a high pressure ratio is needed. Pressure ratio denotes the ratio of absolute air pressure before the supercharger to the absolute air pressure after the compression inured by the supercharger. At higher pressure ratio, or boost, more air mass is delivered to the engine allowing a greater amount of fuel to be burnt as well resulting in higher power output.

[008] In one example of the present teachings, an axial inlet, radial outlet supercharger comprises a tubular housing. The tubular housing comprises an inlet plane and an outlet plane. The inlet plane is perpendicular to the outlet plane. Rotor mounting recesses are in an inner surface of an inlet wall parallel to the inlet plane. A triangular outlet is in the outlet plane. An inlet is in the inlet plane. At least two axial flow backflow ports are in the inlet plane.

[009] In another example of the present teachings, an axial inlet, radial outlet supercharger comprises a tubular housing, the tubular housing comprising an inlet plane and an outlet plane. The inlet plane is perpendicular to the outlet plane. Rotor mounting recesses are in an inner surface of an inlet wall parallel to the inlet plane. An inlet axis is centered between the rotor mounting recesses. A triangular outlet is in the outlet plane. An inlet is in the inlet plane. Lobed rotors each comprise a rotation axis parallel to the inlet axis. The lobes sequentially mesh along the inlet axis when the rotors rotate. Respective lobes are twisted along the length of their respective rotor. The lobes are timed to fluidly seal the inlet from the outlet. At least two backflow ports are in the tubular housing.

[010] A method of controlling a supercharger system, comprises pumping air using a supercharger, the supercharger comprising an intake, an outlet, and backflow ports. The pumped air can be cooled in an intercooler and expelled towards a combustion engine. A computing device can receive and process sensor signals from sensors. The received sensor signals can be compared to predetermined values to determine an opening degree of valves in backflow conduits, the backflow conduits connected to divert expelled air from the intercooler to the backflow ports. And, based on the comparison, the opening degree of the valves can be adjusted.

[Oi l] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several examples of the present teachings and together with the description, serve to explain the principles of operation.

[013] FIG. 1A is a schematic view of a supercharger system with cooled air

backflow conduits.

[014] FIG. IB is a schematic of a supercharger system with cooled air backflow conduits and having an air bypass conduit.

[015] FIG. 1C is a schematic of a supercharger system with combined air backflow and air bypass conduits.

[016] FIGS. 2A-2C are examples of control systems.

[017] FIG. 3 is a graph showing pressure ratios.

[018] FIG. 4A is a simulation result showing the temperature distribution of a supercharger without backflow of cooled air.

[019] FIG. 4B is a simulation result showing the temperature distribution of a supercharger with backflow of cooled air.

[020] FIG. 5 is an example of a Roots type supercharger.

[021] FIG. 6A-6D are views of a supercharger main case.

[022] FIG. 7 is a view of an alternative supercharger main case. [023] FIG 8 is a view of air transfer between lobes.

[024] FIG 9 is an alternative view of air transfer between lobes.

[025] FIG comparison of phase diagrams for lobe timing.

DETAILED DESCRIPTION

[026] Reference will now be made in detail to the present exemplary aspects of the present teachings, examples of which are illustrated in the accompanying drawings.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Bold arrow-headed lines indicate air flow direction, unless otherwise noted.

[027] FIG. 1 shows a supercharger system 10 for controlling the outlet condition of a supercharger 100 through conditioning of the backflow air. Supercharger 100 can have an air inlet 101, a chamber 105, and an outlet 104. The supercharger system 10 is a backflow control system for controlling the backflow event to adjust the temperature at the outlet 104 of the supercharger 100. Supercharger 100 is a positive displacement air pump, and can be a Roots type, or a different type such as a screw type. When actively blowing, or pumping, air, the supercharger 100 heats air as it passes through the chamber 105. Supercharger 100 is used to compress air going to a combustion engine and to increase the power output of the engine. Compression happens as a result of high pressure outlet air back flowing into the low pressure control volume of air as the control volume is transferred to the outlet. The system 10 includes mechanisms for introducing cooled outlet air instead of hot outlet air for the backflow event.

[028] The introduction of cooled air during backflow increases the pressure ratio of the supercharger system over prior art methods. The pressure ratio describes the amount of boost the supercharger can supply to the engine, and is the ratio of the fluid pressure before the supercharger to the fluid pressure after the supercharger. A gas, such as ambient air, is the preferred fluid for compression, though, at times, an amount of other fluid, such as exhaust, can be present due to Exhaust Gas Recirculation (EGR).

[029] Currently, the pressure ratio of a Roots supercharger is limited by the maximum operating temperature, or thermal limit, of the device. The thermal limit is determined by factors such as oil degradation, thermal expansion of metal parts such as the rotor and/or housing, operational fatigue, and durability issues. By reducing the temperature of fluid circulating in the supercharger, the pressure ratio of the device can increase while staying within the thermal limit of the device. [030] Generally, to reduce the temperature of air going into the engine, an intercooler is used to cool the air from the supercharger. The reduction of air temperature will increase the density of the air, which consequently increases the engine's ability to make more horsepower and torque. By backflowing cooled air from the intercooler to the supercharger, the pressure ratio of the supercharger increases while reducing the temperature of the discharged air from the supercharger 100.

[031] In Figure 1, the air inlet 101 allows ambient air to come into the supercharger 100. The air inlet 101 is located on the tubular housing in an inlet plane IP at an inlet side of the supercharger 100. The chamber 105 can contain two rotors 102, 103. Each rotor rotates about an axis parallel to a first axis, or inlet axis IA. Each rotor can have at least two lobes, but preferably, three or four. Rotor 102 has three lobes, 102A, 102B, and 102C. Similarly, rotor 103 has three lobes, 103 A, 103B, and 103C. The lobes can be parallel or twisted. For an example of the twisted design, the rotors can be either hi-helix type or standard helix type. Hi-helix is sometimes characterized as a 120° rotor, while a standard helix is sometimes characterized as a 60° rotor. Each degree indicates the amount of rotor twist over the length. Other degrees of twist can be used based on the design, with an exemplary twist range of 60-150 degrees.

[032] For example, Figure 10 compares a first example and a second example of phase diagrams and port timings for two exemplary superchargers. On the right, the supercharger has two three-lobe rotors of the fifth generation, GEN V, style manufactured by Eaton Corporation. The lobes are twisted 60 degrees along their length. The phase diagram for example 1 indicates the rotational travel for each lobe of the rotor. A given lobe travels 210 degrees of rotation to complete the inlet phase, where air is drawn in through the inlet 1011 or 1012. The lobe then travel 50 degrees to complete the dwell phase and 40 degrees to complete the sealed phase. The backflow event is allotted 40 degrees of lobe travel, and the outlet, or exhaust, phase is allotted 200 degrees of lobe travel to blow the air out of the supercharger. By designing the backflow ports 122 and 1222 to be smaller than the allotted lobe travel, the transfer volume can experience an abrupt and lengthy backflow event. For example, the axial flow back flow slot 1222 can be designed to open in 10 to 15 degrees of rotor rotation, thereby yielding a lengthy cooled air backflow event.

[033] Example 2 of Figure 10 uses a supercharger with two four-lobe rotors. The lobes twist 160 degrees along their length. The inlet phase time is increased to 280 degrees, and the outlet phase time is increased to 220 degrees. The dwell phase is reduced to 20 degrees and the seal phase time is decreased to 10 degrees. The backflow event time is increased to 80 degrees. If the axial flow backflow port 1222 remains as above, made to open within 10 to 15 degrees of lobe rotation, the cooled air backflow event is further increased in duration. If a larger axial flow backflow port is used, such as a fully circular port, the port would not open as abruptly or remain fully open for the full backflow phase. In the case of the circular port, if it is sized to close completely via lobe blockage, it would take 30-40 degrees of lobe rotation to completely open the circular port.

[034] Table 1 summarizes exemplary timing ranges available for twisted lobe Gen V (Fifth Generation) and TVS® (Twin Vortices Series) superchargers manufactured by Eaton Corporation. For a given lobe phase, the general timing range is given and is contrasted against six other timing scenarios for exemplary superchargers.

TABLE 1

[035] For enabling abrupt opening and closing of the backflow port, it is advantageous to shape the port akin to the lobe shape. So, turning to Figure 8, the upper axial flow back flow port 1222 is shown aligned with the lobe 102 A. Because the port is "bean" shaped to substantially match the profile of the lobe, in this instance, match a segment of the outer curve of the lobe, the port does not suffer leakage of air in to the outlet volume 140E or in to the transfer volume 140S. Rather, the lobes are able to block cooled air transfer to seal against parasitic leakage of air. This is beneficial to prevent not only leakage of air back to the inlet volume 1401, but also to prevent outlet air from leaking backwards through the back flow ports. While it is permissible to leak cooled air to the outlet volume 140E, it is desired to limit squeeze of outlet air back through the back flow ports. It is possible with the "bean" shape to prevent leakage between the axial inlet backflow port 1222 and the outlet 104. It is possible with this design to limit cooled air backflow to the designated backflow volume 140B at the designated phase, as shown in Figure 9. Thus, the axial flow back flow port 1222 is a slot designed to have a profile matching a segment on an involute curve. The slot can have rounded edges for smoothed air flow profile. The "bean shaped" slot can be described as a slot having four sides, each side being an arc of a circle. Alternatively, the axial flow back flow port 1222 is a rectangular slot, an oval hole, or a circular hole sized to open fully in 10 to 40 degrees of lobe rotation and sized to be fully obstructed by the lobe when the lobe is aligned over the hole. The radial flow back flow ports 122 are likewise designed to open and close abruptly, and this is accomplished via slots having rectangular, oblong, or other shapes matching the twist of the lobes along their axial lengths.

[036] Rotors 102, 103 can be identical to each other. Or, lobes 102A, 102B, 102C of rotor 102 can be twisted clockwise while the lobes 103 A, 103B, 103C of rotor 103 can be twisted counter-clockwise. For the examples of Figures 1, 5, and 8-10, because rotors 102, 103 have twisted lobes, the supercharger 100 can have much better air handling

characteristics. Further, the supercharger 100 can produce less air pulsation and turbulence. The length of rotors 102, 103 can vary among applications. The size of the supercharger 100 can be determined by the length of rotors 102, 103. Rotors 102, 103 can be meshed together along the first axis, inlet axis IA, as the rotors rotate, and the rotors can be geared to rotate in opposite directions.

[037] The air entering into the chamber 105 of supercharger 100 can be trapped in a gap between adjacent lobes of rotor 102, for example, between lobes 102A and 102B. The air can also be trapped in a gap between adjacent lobes of rotor 103, for example, between lobes 103 A and 103B. The trapped air can be carried to an outlet 104 to be expelled out of the supercharger 100. In the examples shown, the supercharger is an axial-inlet, radial-outlet type supercharger. This means that the inlet air travels into the tubular housing along the axis of the rotors, parallel to the inlet axis IA. As the rotors rotate, the air moves radially away from the inlet axis IA and towards the outlet 104, which is in an outlet plane OP perpendicular to the outlet axis OA. The inlet axis IA and the outlet axis OA are

perpendicular. The outlet 104 can be a triangular shape to match the shape of the rotors 102, 103, or another shape that allows for an easy exit of air. Since the volume of transferred air can be greater than the displacement of engine 120, the air pressure within engine 120 can be increased. In other words, the Roots type supercharger 100 can produce boost pressure by stacking more and more air into the intake manifold.

[038] An intercooler 110 can comprise an inlet port 113, an outlet port 111, and a recirculation conduit 112. Each rotor 102, 103 can have an affiliated recirculation conduit

112 so that cooled air is fed back to the supercharger in a balanced manner. The inlet port

113 can be connected to the outlet 104 of the supercharger 100 to receive the discharged air. The intercooler 110 can be any mechanical device that acts as a heat sink. Further, the intercooler 110 can comprise a bar, a plate core, and fins (not shown in figures). Once the discharged air from the supercharger 100 enters the intercooler 110, air can move through bar and plate core to make its way to the outlet port 111, while becoming cooled through heat transfer. General details of the working mechanics of an intercooler are well known, and thus, will not be described herein. The intercooler 110 can vary dramatically in size, shape and design depending on the performance and space requirements of the supercharger system. Intercooler 110 can be air-to-air type or air-to-water type.

[039] The outlet port 111 expels the cooled air towards an inlet manifold of engine 121 and the outlet port 111 can be connected to conduits 112 by way of optional valves 114A and valve sensor and actuation devices 114. The conduits 112 can branch out either to left, right, or both sides of the outlet port 111. The other end of the conduit 112 connects to radial flow backflow ports 122 of supercharger 100 such that cooled air can be transferred between lobes of the rotors. Alternative examples enable conduit connectivity to the axial flow backflow ports 1222 alone or in combination with the radial flow back flow ports 122.

[040] Some supercharger systems utilize back flow ports to reduce noise coming from the supercharger. Instead of receiving hot outlet air back flow, it is possible to use the radial flow back flow ports 122 for receiving cooled air from conduits 112. This can reduce the noise stemming from the operation of the supercharger. Therefore, having conduits 112 can improve noise, vibration, and harshness (NVH) capabilities of the supercharger.

[041] It may be necessary to adjust the size, shape, and location of the radial flow and axial flow backflow ports 122, 1222 shown in the Figures to provide optimal cold air input to the supercharger. The cold air radial flow backflow ports 122 of Figure 5 are located on the main case 106 after the inlet 101 and before the outlet 104. That is, the radial flow backflow ports 122 are distinct from the inlet 101 and the outlet 104. The radial flow backflow ports 122 can align with the gaps between the lobes of the rotors such that as the rotors spin, the cooled air is mixed with intake air in a gap as the gap passes the radial flow backflow port 122. To ensure proper mixing, a distance between the inlet and a radial flow backflow port is greater than a distance between a gap and its adjacent backflow port. As shown in Figure 5, the radial flow backflow port can be closer to the outlet than to the inlet.

[042] The radial flow and axial flow back flow ports 122, 1222 are sized and shaped to introduce the cooled backflow air between the rotors at a location where the rotors form a "sealed volume." That is, the rotors rotate to move air from the inlet to the outlet of the supercharger, and there is a point where the gap between lobes is sealed from both the inlet and the outlet. Cooled backflow air is introduced in to this gap, or sealed volume, by the strategic placement, shape and number of radial flow and axial flow backflow ports 122, 1222.

[043] For example, two radial flow back flow ports 122 may be used, as illustrated in Figure 5, or one may be used, as illustrated in Figures 6A-9. The radial flow back flow ports 122 can be rectilinear or rounded, as illustrated, or another tunable shape, such as oval or circular. Preferably, the shape of the ports allows a sharp opening and closing of the ports, such that the backflow event occurs abruptly at a very high rate. The number of axial and radial flow back flow ports is selectable to augment the tuning of the cooled air backflow.

[044] Inlet side axial flow backflow ports 1222 encourage axial flow of the cooled, high pressure backflow air by being positioned on the inlet side and at a location that causes cooled air to be drawn from the lower pressure, lower temperature inlet side to the high pressure, high temperature outlet side of the supercharger. The trajectory of the backflow air at the inlet side axial flow backflow ports 1222 is along the inlet axis IA, and so the high pressure cooled air rushes along the rotor length, as shown by the bold arrow in Figure 9. Thus, the inlet side axial flow backflow ports 1222 complement the axial -inlet, radial-outlet design of the supercharger.

[045] The cooled air backflow can be performed with only the inlet- side axial flow backflow ports 1222, with only the outlet-side radial flow backflow ports 122, or with a combination of inlet-side axial flow backflow ports 1222 and outlet- side radial flow backflow ports 122. Thus, the number of backflow ports can vary from two, one for each rotor, to six, yielding three ports for each rotor. If the ports are made smaller, a greater number of ports per rotor can be implemented.

[046] As shown in Figures 6A-7, the radial flow backflow ports 122 can be reduced from four to two on the outlet 104 side of the main case 106. Axial flow backflow ports 1222 are added to an inlet wall 1063 on the inlet 104 side of the main case. Inside the main case 106, an inner side of the inlet wall 1063 includes rotor mounting recesses 1020 and 1030 in a plane parallel to the inlet plane IP. In another alternative, the main case comprises the axial flow backflow ports 1222 and does not include any radial flow backflow ports 122.

[047] The tubular main case 106 includes a front plate 1060. In Figure 6A, the front plate 1060 includes a machining pass-through 1061 to permit tooling access to the axial flow backflow ports 1222. The pass-through 1061 receives a plug to seal the front plate 1060 after machining. Alternatively, a recirculation conduit 112 is coupled to the pass-through 1061 to encourage axial backflow air flow with reduced reflection of air waves. To facilitate conduit coupling, the pass-through can be other shapes than the illustrated "mushroom" shape, such as circular, oval, rectangular, or square. Figure 7 eliminates the pass-through 1061 in favor of a sealed front plate 1060.

[048] A tuning distance TD between the inlet wall 1063 and front plate 1060 is selected to permit backflow air to couple to the axial flow backflow port 1222 without creating excessive standing waves or reflections of air back out of the chamber 105. The tuning distance TD is selected to limit flow losses and to control air restriction in to the axial flow backflow ports 1222. Additional control of the flow is determined by the length and diameter of the recirculation conduit 112 between the intercooler and the backflow compartment 1075. The backflow compartment 1075 can include the volume of air exposed to the radial flow backflow ports 122 and the volume of air exposed to the axial flow backflow ports 1222. The at least one divider 1062 cooperates with walls 1064, 1065 of the tubular housing and with the front plate 1060 to form backflow compartment 1075.

[049] Inlet 101 optionally includes a support 1010. Inlet 101, as above, supplies intake or bypass air to the rotors 102, 103 of the supercharger. The support 1010 provides an indicator in Figure 6C for the halves of the inlet. Inlet area 1011 is allocated for rotor 103, and inlet area 1012 is for rotor 102. The inlet 101 can be described as extending for an amount of the tubular housing. But, it is convenient to define the inlet for each rotor such that inlet area 1012 has an inlet extent θι in a circular area of the inlet wall 1063 allocated for rotor 102. Using this convenient reference, the inlet face is divided in to 360 degrees about a center point at vertex V in the rotor mounting recess 1020. The transfer or seal extent 9s occupies another portion of the inlet wall 1063. The axial flow back flow port 1222 occupies a backflow extent ΘΒ, and the remainder of the circular area is for rotor travel to accommodate the outlet phase and rotor meshing. A mirror image of the angular extents is applicable to the rotor mounting recess 1030 utilizing a vertex V2 and inlet 1012. [050] The use of the vertices V, V2 divides the inlet plane to explain the locations for the axial flow back flow ports 1222 with respect to the inlet 104. Depending upon whether the rotors comprise 3, 4, or 5 lobes, and depending upon the twist of the lobes being 60-150 degrees, the inlet area 1011 occupies an extent θι in the inlet plane. So while the timing requires a large rotation angle for the twisted lobe to pass the inlet area 1011, the angular extent of the inlet area θι can be smaller than the degree of the timing. Inlet extent Oi can be approximated by adding the rotor twist angle to the dwell phase of Table 1, for a range of 80-200 degrees.

[051] Seal extent Os can be approximated by adding the seal phase of Table 1 to the lobe spacing. Depending upon whether the lobes are spaced 72, 90, or 120 degrees apart, or another spacing, and using a seal phase of 10-70 degrees, the seal Os would be in a range from 82-190. As above, the axial flow back flow port 1222 opens or closes in 10-40 degrees of lobe rotation, and so the backflow extent ΘΒ is approximated to occupy 10-40 degrees of the inlet plane about the vertex V. The inlet area 1011 is thus separated from the axial flow back flow port 1222 by approximately 82-190 degrees. Table 2 offers additional examples for explaining the location of the axial flow back flow ports 1222.

TABLE 2

[052] Inlet 101 is sealed from the backflow volume in integrated manifold 1070 via a floor 1071. The floor can be an inserted seal or part of the housing casting. The support 1010 couples to floor 1071 of integrated manifold 1070. The floor 1071 is between the inlet wall 1063 and the front plate 1060 and forms the integrated manifold 1070 in cooperation with extensions of walls 1064 and 1065. Floor 1071 fluidly separates the inlet 101 from the axial flow back flow ports 1222 by providing physical separation between inlet 101 and integrated manifold 1070. Inlet air thus cannot mix with cooled backflow air. [053] The inlet 101 extends through the front plate 1060 and intersects an inlet plane IP along inlet wall 1063. The axial flow backflow ports 1222 are also in the inlet plane IP. The inlet plane IP is perpendicular to the inlet axis IA, which is shown coming out of the page in Figure 6C.

[054] The outlet 104 and, when used, the radial flow back flow ports 122, are in an outlet plane OP that is perpendicular to the inlet plane IP. The outlet plane is also parallel to the inlet axis IA. An outlet axis is shown coming out of the page in Figure 6B. The outlet axis is perpendicular to the inlet axis IA and is perpendicular to the outlet plane OP, as in Figure 6A. When describing the supercharger as an axial inlet, radial outlet device, it is convenient to explain that air travels in to the supercharger inlet 101 and through the axial flow backflow ports 1222 axially, or along the rotor axis, which are parallel to inlet axis IA. As the supercharger acts on the inlet air and the backflow air, the air is directed to leave the outlet 104 radially with respect to the rotor axis, meaning the air exhausts along, or generally parallel to, the outlet axis OA. This differentiates the supercharger from radial inlet, radial outlet devices, which do not have the same air flow characteristics or leakage constraints.

[055] A tuning distance TD separates the front plate 1060 from an inlet wall 1063 of the main case 106. The tuning distance TD is selected to regulate the flow of cooled backflow air to the axial flow backflow ports 1222. The alignment of the integrated manifold 1070 with the axial flow backflow ports 1222 is selected to direct the air flow in to the chamber 105 in the direction of the outlet 104. By directing the flow, the supercharger works less, compared to the radial flow backflow ports 122, to blow the air out because the air flows axially along the rotor as the rotor spins in the chamber 105.

[056] Referring to Figures 8 and 9, the cooled backflow air exits the intercooler 1 10 and is directed to the backflow compartment 1075. The lobes 102A-102D and 103A-103D are twisted along the length of their respective rotors and are hollow, as indicated by the hollows 102H and 103H. Looking to Figure 8, lobe 102B and 102C are exposed to the inlet 104 and permit an inlet volume 1401 of air to enter the main case 105. Lobe 102D is sealed against the main case 105. Lobe 102A also seals against the main case 106 and blocks its affiliated axial flow backflow port 1222 and blocks its affiliated radial flow backflow port 122. A sealed transfer volume 140S is formed between lobes 102A and 102D. An exit volume 140E of air is exposed to the outlet 104 between lobes 102 A and 102B.

[057] When the rotor 102 rotates additionally, as shown in Figure 9, lobe 102A no longer blocks axial flow backflow port 1222 and no longer blocks radial flow backflow port 122. Cooled backflow air can now enter the gap between lobes 102 A and 102D. Ideally, though not required, the transfer volume is still sealed from the inlet and from the outlet, but the sealed transfer volume 140S of air mixes with the cooled backflow air to form a backflow transfer volume 140B. As the inlet air moves from the inlet to outlet, the inlet air is heated. The cooled backflow air follows thermodynamic principles, moving from low temperature to high temperature and from high pressure to low pressure, thereby progressing from the inlet end of the rotor 102 to the outlet 104. The result is a greater amount of air blown by the supercharger between lobes 102A and 102D.

[058] The rotors 102, 103 of Figures 8 and 9 are meshed and oppositely rotating, and the timing of the rotors is such that rotor 103 is exposed to cooled backflow air input at different times than rotor 102. So, when rotor 102 blocks axial flow backflow port 1222, rotor 103 exposes the gap between lobes 103 A and 103B to cooled backflow air to create a backflow transfer volume 14 IB. Rotor 103 blocks its axial flow backflow port 1222 when rotor 102 has fully exposed its axial flow backflow port 1222. The extent of blockage or exposure is determined by the shape and size of the lobes 102A-102D, 103A-103D and by the shape, location, and size of the axial flow and radial flow backflow ports 122 and 1222.

[059] As illustrated in Figure 8, the shape and orientation of the lobes 102A-102D, 103A-103D and the shape and orientation of the axial flow and radial flow backflow ports 122 and 1222 complement one another. The complementary pairing permits the tuning of sealing and timing. Thus the sealed transfer volumes open to the backflow transfer volumes at distinct points as the lobes pass the backflow ports. As above, the use or non-use of the axial flow or radial flow backflow ports with one another permits additional tuning of the backflow characteristics and thus the compression ratio of the supercharger.

[060] Thus, for customer compression ratio demands, a system can be designed to operate a supercharger at an ideal rotor speed to achieve an ideal compression ratio, and the size, orientation, and timing of the lobes are selected to complement the use of one or both axial flow and radial flow backflow ports to further tailor the achievement of the target compression ratio. Greater control of standing waves inside the chamber 105 is achieved. Greater control over exit pulsations is achieved.

[061] As an additional point of air flow tailoring, the length and diameter of the input 104 is selected to impact the length of standing waves in the chamber 105. Thus, not only the tuning distance TD of the integrated manifold 1075 is controllable, but the input 104 length is also controllable. [062] At least one divider 1062 separates the outlet 104 from the backflow compartment 1075. The outlet 104 and divider 1062 can mate with ducting for

communicating air with an intercooling device. And the divider 1062 and backflow compartment 1075 can mate with the recirculation conduit 112.

[063] The width of the intercooler outlet port 111 can be designed to meet the need of a particular supercharger in consideration of size, type, and space, along with other performance requirements. For example, the width of outlet port 111 can be much wider than the width of the radial flow backflow port 122. As an example, the width of the outlet port 111 can be 43 mm while using the width of a single backflow conduit 112 of 8 mm. In other designs, the radial flow and or axial flow backflow port and affiliated conduit can have a greater cross-sectional area than the outlet port 111 and its affiliated conduit. The port and conduit sizes are adjusted for particular applications to ensure fluid flow from supercharger outlet, to intercooler, to backflow port. Thus, thermodynamic laws for pressure and temperature impact backflow port locations and sizes so that cooled air exiting the intercooler 110 can backflow via the conduit 112 back to the supercharger 100.

[064] As one example, the size of the radial flow and axial flow backflow ports 122, 1222 is determined by the below estimation of the port area Ap_ort:

where Pi is the inlet pressure, P₂ is the maximum pressure ratio of the outlet, Ti is inlet temperature, T₂ is outlet temperature, R is a gas coefficient, NRPM is the maximum speed in rotations per minute ("RPM") of the supercharger, V-rransferVoiume is the volume of air transferred, a is the speed of sound at the given inlet temperature Ti, γ is a ratio of specific heat at a constant pressure and constant volume.

[065] Port area Ap_ort determines what total area should be allocated for the cooled backflow air transfer. Thus, the sum of areas allocated to the axial flow backflow ports 1222 and or radial flow backflow ports 122 should total the port area Ap_ort. The ideal port area Alport is in the range of one fourth (1/4) to 4 times Ap_ort. More specifically, the ideal port area Alport is one half (1/2) to 2 times Ap_ort. More specifically, the ideal port area Aip_ort is two thirds (2/3) A_Port.

[066] Because the axial flow back flow ports 1222 encourage axial air flow towards the outlet 104, it is advantageous to allocate all, or most, of the port area Ap_ort to these backflow ports. Thus, in consideration of the timing constraints, the axial flow back flow ports 1222 should comprise as much port area Ap_ort as feasible, even in favor of omitting the radial flow back flow ports 122. But, if additional area is needed to meet the port area Ap_ort while meeting the above 10-15 degree to 30-40 degree lobe rotation for opening the axial flow back flow ports 1222, then that additional area should be allocated to the radial flow back flow ports 122. When an especially large port area is required, it can be necessary to include multiple radial flow back flow ports 122, as illustrated in Figure 5. When the inlet area is physically constrained in an installation, it can be necessary to omit the axial flow backflow ports 1222 in favor of utilizing only radial flow backflow ports 122. Thus, there can be one or more sets of backflow ports to meet design constraints. The one or more backflow ports are distributed to effectuate cooling of the backflow volume 140B while preventing leakage of air back to the inlet, minimizing squeeze from the outlet 104, and permitting abrupt opening and closing of the backflow ports.

[067] By way of example, for a supercharger having only axial flow backflow ports 1222 and no radial flow backflow ports 1222, cooled backflow air enters the sealed transfer volume 140S to form backflow transfer volume 140B. The integrated manifold 1075 seals the low pressure inlet air from the higher pressure cooled backflow air volume. The cooled backflow air enters the axial flow backflow ports 1222 parallel to the rotors and in the direction of the air discharge at outlet 104. The lobes of rotors 102 and 103 are configured as in Figures 8 and 9 to prevent a "short circuit" between the inlet volumes 1401, 1411 and backflow transfer volumes 140B, 14 IB. That is, the cooled backflow air cannot

communicate with the inlet 104 because the lobes are sealed to prevent the backflow air from reaching the inlet 104. As illustrated, it is desired to have a sealed transfer volume 140S, 141S that does not communicate with the inlet 104 or outlet 105 prior to the backflow of cooled air. While it is possible to permit some connection between the backflow transfer volume 140B and the outlet volumes 104E, 14 IE, in this example, the inlet, backflow, and outlet air volumes are independent of one another. A seal time of 15-45 degrees, a backflow angle of 20-50 degrees, and a rotor twist of 60-130 degrees is applied. [068] In addition to adjusting the width of the radial flow and axial flow backflow ports 122, 1222, it is possible to adjust the length of the backflow conduit 112 to tune the flow back in to the supercharger. The location of the radial flow and or axial flow backflow port is selected to inject cooled air in to the supercharger to cool the air mass. The ideal location to inject the air is in to a sealed volume between rotating lobes of the rotor. That is, the rotors are in a location that seals the injected air mass from the inlet and from the outlet. To tailor the cooling effect, the amount of air moved back to the supercharger lobes must be controlled. Air injected between lobes of the supercharger is tailored by selecting the length and width of the backflow ports, thus tuning the flow. Additional tailoring is achieved by controlling the volume of the flow, as by valves, discussed below.

[069] By backflowing the cooled air and mixing the same with the air input to the supercharger 100, the air will be more tightly stacked in the inlet manifold 121. The pressure ratio will be higher than stacking the air not mixed with the cooled air. In other words, by using cold high pressure air from the outlet 111 of the intercooler, the temperature inside the supercharger 100 can be reduced. Thus, a higher pressure ratio can be achieved. Therefore, without increasing the size of the supercharger 100, greater boost is provided to engine 120.

[070] In addition, since the cooled air is mixed with the air in the supercharger, the resulting air transported out of the supercharger can be even cooler, thus increasing the combustion efficiency. At the same time, a low temperature can allow supercharger 100 to go to a higher pressure ratio before reaching the thermal limit of the supercharger.

Furthermore, since the air coming into the supercharger 100 is mixed with the colder air backflowing through conduits 112, the supercharger 100 would be able to intake hotter air than the conventional supercharger. In other words, the modified supercharger system can improve the supercharger's capability to handle high temperature inlet air.

[071] For example, tolerances can be strategically reduced because the cooled backflow air prevents the supercharger from attaining a high heat from the blowing of intake air. Or, a higher intake air temperature can be accommodated with customary tolerances because the cooled air will bring the overall air temperature within normal operating ranges. Since the relationship between thermal expansion tolerances and outlet temperatures is linear, if the outlet temperature is reduced, the tolerances between the rotors can be reduced, and the tolerances between the rotors and housing can be reduced by the same percentage that the outlet temperature is reduced. [072] There can be other benefits of using the recirculation conduits 112 in the supercharger system 10. In the modified system, EGR (exhaust gas recirculation) handling capability can be improved since the air recirculated via EGR can be cooled with the backflow air.

[073] Conduits 112 can also improve efficiency of the supercharger 100. Having conduits 112 can lower the outlet 104 temperature and in turn lower the overall temperature operation range of the supercharger 100. If the overall temperature operation range is reduced, then tolerances between rotors and the case can be tightened, and thus improve operating efficiency of the supercharger 100.

[074] The placement of radial flow and axial flow backflow ports 122, 1222 can be distanced from the inlet 101 and the outlet 104, and rather close to rotors 102, 103. The size and shape of the radial flow and axial flow backflow ports 122, 1222 is designed to optimize cooled air flow from the intercooler to in between rotor lobes while minimizing the use of the ports as an air outlet. By selecting the dimensions (length, width, height) of the conduits 112, and by virtue of high pressure air moving towards areas of low pressure, the cooled air moves back towards the hot chamber 105.

[075] Figure IB is a schematic of a supercharger system 11 with cooled air backflow conduits 112 and having an air bypass conduit 115C. The system 11 allows air bypass at times when the supercharger's full capacity is not needed in the combustion engine. So, in periods where limited or no engine boost is desired, air can be bypassed away from the engine 120 and returned to the inlet 101 of the supercharger 100. Bypass conduit 115C is shown after the intercooler 110, though other locations are possible. A bypass valve 115A is controlled via bypass actuator 115. The bypass actuator 115 can comprise a sensor in addition to actuation mechanisms and control electronics to receive commands and emit signals for controlling bypass valve open or close parameters.

[076] FIG. 1C is a schematic of a supercharger system 12 with combined air backflow and bypass conduits. A multi-way valve 116A receives cooled air from intercooler outlet 111 via the combined conduit 116B. Actuator 116 can comprise a sensor in addition to actuation mechanisms and control electronics to receive commands and emit signals for controlling multi-way valve 116A open or close parameters. Multi-way valve 116A can be controlled to bypass air in bypass conduit 115C to the inlet 101 of supercharger 100. Multi- way valve 116A can also direct cooled air to radial flow backflow ports 122 via conduit 112. While a single valve is illustrated for multi-way valve 116A, alternatives use more than one valve or additional conduit branching to achieve the bypass and backflow principles.

[077] Figures IB and 1C offer control of the backflow event and enable adjustment to the temperature and flow rate at the outlet 104 of the supercharger 100. That is, the bypass valve 115A or multi-way valve 116A can be controlled to adjust an intake flow rate by adjusting air supplied to inlet 101. The backflow event can be adjusted by control of valve 114A or multi-way valve 116 A. While only radial flow backflow ports 122 are illustrated in Figures 1A-1C, as above, there can be only axial flow backflow ports 1222, multiple radial flow back flow ports 122, or a combination of axial flow and radial flow back flow ports.

[078] Figure 2A shows a control mechanism 20 for the backflow control system of Figure 1 A. The control mechanism 20 can be programmed to control the backflow event to adjust the temperature at the outlet 104 of the supercharger 100. The control mechanism 20 enables the implementation of a method for controlling the outlet condition of the supercharger 100 through conditioning of the backflow air.

[079] The control mechanism 20 can control air circulation through the system 10, allowing some portion of cooled air to backflow to the supercharger 100. At times, it may be beneficial to terminate backflow, so the control mechanism 20 can adjust the amount of cooled air from zero up to a maximum amount by controlling actuators 114 affiliated with valves 114 A. The maximum amount of backflow is calculated and controlled based on engine air flow demands and temperature requirements, and thus can vary based on operating conditions and from vehicle to vehicle and from driver to driver.

[080] The control mechanism 20 can control whether a backflow or bypass event takes place. When the supercharger actively blows air to the engine, the control mechanism 20 controls the valves 114A and 116A to provide a backflow event. But when cooling is not needed, or when the supercharger is idling, the control mechanism controls bypass valve 115A and valves 114A or valve 116A to bypass air back to the inlet side of the supercharger. If the air is cooled by the intercooler 110, then the bypassed air can cool the supercharger and the passive (not-blown) air passing through the system. Because this passive cooling is not always needed, it is possible to connect the bypass valve 115A prior to the intercooler 110 to bypass uncooled air back in to the system.

[081] Control mechanism 20 can be a part of one or more control mechanisms employed in a vehicle, such as on-board computers, computing chips, and other processing devices that control vehicle operations. Control mechanism 20 includes customary non- transient computing elements, such as transmit and receive ports, processor, memory, and programming.

[082] The control mechanism 20 can be a part of an engine control unit (ECU). The control mechanism 20 can include a controller 150, sensors 151, 152, 153, and an actuator 114 that operates valve 114 A. The actuator 114 can include sensors for collecting data on the opening degree of the valve 114 A. The number and placement of sensors can vary based on feedback control implemented, and so the system can have more or less sensors and actuators than in the illustrated example. The sensors can be of a variety of types capable of sensing conditions and of sending signals, such as temperature, pressure, speed, or air flow (velocity). The illustrated sensors can include a plurality of types, such that a sensor can measure multiple conditions, such as both temperature and air flow.

[083] The valve 114A can be opened or closed as determined by the controller 150 to be appropriate for the vehicle's operation mode. The opening degree of the valve 114A can range from fully open to fully closed.

[084] The determination of opening/closing the valve 114A can be made by measuring the temperature of the air at the outlet 104, or the temperature in the engine 120. Further, the temperature reading of the air expelling out of the outlet port 1 11 can also affect the decision to open/close or to adjust the opening degree of the valve 114A.

[085] The sensor 151 can be a mass air flow sensor (MAF), measuring the mass flow rate inside the engine 120. For instance, the sensor 151 can be a hot wire sensor. Sensor 151 can be positioned inside the engine 120. The reading from the sensor 151 ensures that optimal amount of air is being supplied to the engine 120. Sensor 151 can also measure the temperature inside the engine.

[086] The sensor 152 can be a temperature sensor, measuring the temperature of the blown air exiting the outlet 104 of the supercharger 100. The sensor 152 can also measure the flow rate of the air. The air blown out from the supercharger 100 may need to be sufficiently cooled prior to entering the intake manifold 121. If the air is not sufficiently cooled, then the most power efficient combustion process may not occur in the engine 120. Therefore, the air temperature may need to be reduced by the intercooler 1 10 to reach the optimal temperature to enable more efficient and powerful combustion inside the engine 120. By backflowing cooled air to the supercharger 100, the air at the outlet 104 is lowered significantly. And, when the temperature of air must be increased for efficient engine operation, the valve 114A can be adjusted to restrict cooled air backflow. [087] The sensor 153 may be a pressure sensor, measuring the pressure of the air building in the inlet manifold 121 of the engine 120. The purpose of the supercharger 100 is to provide a boost to the engine 120, allowing the engine 120 be more powerful. Boost is given in terms of pressure ratio, which is the ratio of absolute air pressure before the supercharger to the absolute air pressure after compression by the supercharger 100.

Therefore, it is important to have the appropriate pressure for air entering the inlet manifold 121. The pressure sensor 153 can be located on the inlet manifold 121 of the engine 120 to provide feedback to controller 150.

[088] The readings from the sensors 114, 151, 152 and 153 are transmitted to the controller 150. The controller 150 can compare each received reading from the sensors 114, 151, 152, and 153 with predetermined values. The predetermined values can be calculated optimal values that have been saved in the control system, or the predetermined values can be calculated in real time based on vehicle dynamics.

[089] For example, the reading from the sensor 151 can be equal to a predetermined value. That means that the current air amount going into the engine and air entering into the supercharger is optimal. Therefore, if the controller 150 determines that the reading from the sensor 151 is equal to the predetermined value, then no action may be taken. On the other hand, the reading from the sensor 151 may not be equal to the predetermined value. That means that the current flow rate or temperature of air, either going into the engine or exiting the supercharger, is not optimal. In this case, the controller 150 can emit a signal to either open or close valves 114A using actuators 114, among other adjustment signals. By opening or closing valves 114A, the temperature of the supercharger can be adjusted. By controlling the he backflow event, outlet pressure pulsations can be influenced depending on the desired results. Additional control mechanisms can be implemented to adjust the speed of the supercharger 100, among other operating conditions. Similar determinations and adjustments can be made for the remaining sensors.

[090] The controller 150 can adjust an amount of air in conduit 112 by controlling the opening degree of the valve 114 A. Similarly, the controller 150 can adjust other operating conditions, such as an opening degree of a throttle valve. By having the appropriate amount of air either in backflow or entering the supercharger 100, the efficiency of the supercharger system 10 can be ensured.

[091] Alternative control mechanisms 21 and 22 are shown in Figures 2B and 2C. Control mechanism 21 corresponds to system 11 of Figure IB. Similar to that outlined for Figure 2A, the controller 150 of Figure 2B can adjust the backflow event. The system 11 can also send signals to bypass actuator 115 to control the amount of air bypassed away from engine 120. This enables more control over the amount of air entering supercharger 100.

[092] Figure 2C likewise controls multi-way actuator 116 of multi-way valve 116A to tailor the amount of cooled air bypassed to the inlet 101 or provided to radial flow backflow ports 122.

[093] Engine air flow demand can be based on a variety of other vehicle operating conditions, so, in addition to comparisons to predetermined values, or alternatively thereto, calculations can take place in real time. The simplified control mechanisms of Figures 2 A, 2B, and 2C can thus be augmented to include additional sensors and feedback and can be tied to other vehicle controls, such as acceleration, yaw, rollover, slip, braking, etc. Thus, as engine air flow demands change due to these other factors, the cooled air backflow and bypass events can be adjusted to tailor air temperature at outlet 104.

[094] Experiments were conducted to test the effect of the backflow of cooled air at 14,000 RPM. The results obtained in these experiments will be now explained using Figure 3. The graph in Figure 3 shows the relationship between the temperatures at supercharger outlet 103 with the pressure ratio achievable. Figure 3 graphs experimental data conducted at a speed of 14,000 RPM. The vertical axis indicates the temperature of supercharger outlet 103 while the horizontal axis indicates pressure ratio. In doing the experiment, the thermal limit was set to 150°C. The thermal limit, or maximum operating temperature, is one of the parameters for determining the pressure ratio of a Roots type supercharger. If one increases the pressure supplied by the supercharger without increasing the temperature of the supplied air, then significantly higher pressure ratio can be reached. The inlet temperature was constant at 27° Celsius. The supercharger used in the experiment was an M45 Roots type supercharger manufactured by Eaton Corporation, like the example shown in Figure 5.

[095] The graphs show data for the pressure ratio for the M45 supercharger without cold air backflow, and the pressure ratio for the M45 supercharger with cold air backflow. The resulting graph line for the M45 supercharger without cold air backflow is inclined to about 45 degrees, more sharply than with cold air backflow.

[096] The results indicate that a higher pressure ratio for the given thermal limit occurs in the M45 supercharger with cold air backflow. Figure 3 shows that at 150° Celsius, the pressure ratio for the M45 without cold air backflow was 2.2. To achieve a pressure ratio higher than 2.2, the supercharger must be run beyond its thermal limit, which is not practical because of the thermal expansion of parts and interference with tolerances. However, by having the cold air backflow in the M45 supercharger, the pressure ratio increases to about 4.5 without exceeding the thermal limit.

[097] In addition to the experiment testing the effect of cooled backflow air on pressure ratio, the effect of backflow on temperature was simulated. Comparing Figures 4A and 4B shows the effect of the cooled air on the temperature of the air at the outlet of the supercharger. The simulation was conducted at the supercharger speed of 6000 RPM. Figure 4A shows the simulation results of the temperature distribution in the supercharger system without the cold air backflow. Air enters the supercharger 100X and is heated and expelled towards intercooler 110X. A backflow conduit 122Y allows expelled air to enter port 122X. The air is heated via the pumping action of supercharger 100X, so the expelled air is hot compared to the inlet temperature. The temperature distribution (K) within the supercharger system was simulated with given constants which include a pressure ratio of 2 and an inlet temperature of 300K. When measured, the outlet temperature was close to 435K, resulting in a temperature increase of 135K from inlet to outlet.

[098] On the other hand, the supercharger system with cooled air backflow in Figure 4B showed less temperature increase. Air entered supercharger 100 and was expelled to intercooler 110. After exiting the intercooler, cooled air travelled through conduit 112 to backflow in to supercharger 100. The outlet temperature was 388K, and thus, the net temperature increase was only 88K from inlet to outlet. Therefore, the backflow of cold air in the supercharger system reduced the temperature of the air at the outlet of the

supercharger.

[099] Figure 5 shows a model of supercharger 100 that can be used in the supercharger systems 10, 11, and 12. Supercharger 100 is an axial inlet, radial outlet type. An air flow path is shown by arrows so that air entering an air inlet on the right side of the page exits out a triangular outlet 104 in the center of the page. A portion of the outer housing is removed to show inside main case 106. Supercharger 100 can be, for example, an M45 or other Roots type supercharger manufactured by Eaton Corporation, including its TVS® brand Twin Vortices Series type. Figure 5 shows the cross section of the supercharger 100 having multiple radial flow backflow ports 122 communicating with each rotor.

Supercharger 100 has two rotors 102, 103 having three lobes. Two rotors 102, 103 are placed in the housing chamber 105. Radial flow backflow ports 122 can be placed on each side of the outlet and near each rotor 102, 103. By placing the radial flow backflow ports 122 to direct air between adjacent lobes of each rotor, the cooled air can be effectively mixed with the intake air to lower the temperature of the air being transported out of the supercharger 100.

[0100] Radial flow backflow ports 122 can be placed in the main casing 106 to interface with recirculation conduits 112. Main casing 106 can be formed as a casting defining the inlet port 101, outlet port 104, and radial flow and or axial flow backflow ports 122. Main casing 106 can comprise multiple sections integrated together, and main casing 106 can be integrated with other housing sections to form an air envelope around the rotors, rotor mounts, gear case, and other operational features of supercharger 100.

[0101] In the preceding specification, various aspects of the present teachings have been described with reference to the accompanying drawings. It will, however, be evident that various other modifications and changes may be made thereto, and additional aspects may be implemented, without departing from the broader scope of the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.

[0102] Other aspects of the present teachings will be apparent to those skilled in the art from consideration of the specification and by practice of the disclosure. For example, it is possible to have a main engine intercooler, such as intercooler 110, and additional intercoolers dedicated to each backflow conduit 112 or backflow port 122. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

WE CLAIM:

1. An axial inlet, radial outlet supercharger, comprising:

a tubular housing, the tubular housing comprising an inlet plane and an outlet plane, wherein the inlet plane is perpendicular to the outlet plane;

two rotor mounting recesses in an inner surface of an inlet wall, the inlet wall parallel to the inlet plane;

a triangular outlet in the outlet plane;

an inlet in the inlet plane; and

at least two axial flow backflow ports in the inlet plane.

2. The supercharger of claim 1 , wherein each of the at least two axial flow backflow ports is a slot having a profile matching a segment on an involute curve.

3. The supercharger of claim 1 , wherein the outlet plane further comprises at least two

radial flow backflow ports.

4. The supercharger of claim 1 or 3, wherein each of the at least two axial flow backflow ports and each of the at least two radial flow backflow ports is one of a rectangular slot, an oval hole, a circular hole, or a slot having four sides, each of the four sides being an arc of a circle.

5. The supercharger of any one of claims 1 -3, further comprising a front plate separated from the inlet wall by a tuning distance.

6. The supercharger of claim 5, further comprising a pass-through in the front plate, the pass-through aligning with each of the at least two axial flow back flow ports.

7. The supercharger of claim 5, further comprising a floor between the inlet wall and the front plate, the floor fluidly separating the inlet from the at least two axial flow back flow ports.

8. The supercharger of claim 7, further comprising a support in the inlet, the support

abutting the floor.

9. The supercharger of claim 1 or 2, wherein the axial flow back flow ports occupy a

backflow port area Ap_ort in the tubular housing determined by:

where Pi is an inlet pressure, P₂ is a maximum pressure ratio of the outlet, Ti is an inlet temperature, T₂ is an outlet temperature, R is a gas coefficient, NRPM is a maximum speed in rotations per minute of rotors in the supercharger, V-rransferVoiume is a volume of air transferred, a is a speed of sound at a given inlet temperature Ti, γ is a ratio of specific heat at a constant pressure and constant volume.

10. The supercharger of claim 9, wherein the axial flow back flow ports occupy an ideal port area Aip_ort in the range of one fourth to four times the backfiow port area Ap_ort.

1 1. The supercharger of claim 10, wherein the ideal port area Aip_ort is one half to two times the backfiow port area Ap_ort.

12. The supercharger of claim 1 1 , wherein the ideal port area Aip_ort is two thirds of the

backfiow port area Ap_ort.

13. The supercharger of claim 9, further comprising at least two radial flow backfiow ports in the outlet plane, the backfiow port area Ap_ort further comprising the area occupied by the at least two radial flow backfiow ports.

14. The supercharger of claim 9, further comprising at least two radial flow backfiow ports in the outlet plane, wherein the ideal port area Aip_ort is further occupied by the radial flow backfiow ports.

15. The supercharger of any one of claims 1 -3, wherein, considering a center point of a first of the two rotor mounting recess as a central vertex on the inlet plane, an inlet area of one half of the inlet occupies 80-200 degrees of the inlet plane and a first of the at least two axial flow backfiow ports occupies 10-40 degrees of the inlet plane.

16. The supercharger of claim 15, wherein the first of the at least two axial flow backfiow ports occupies 10-15 degrees of the inlet plane.

17. The supercharger of claim 15, wherein the first of the at least two axial flow backfiow ports occupies 30-40 degrees of the inlet plane.

18. The supercharger of claim 15, wherein the inlet area is separated by 82-190 degrees from the first of the at least two axial flow backflow ports.

19. The supercharger of claim 15, wherein the inlet area is separated by 100-170 degrees from the first of the at least two axial flow backflow ports.

20. The supercharger of any one of claims 15, wherein, considering a center point of a second of the two rotor mounting recess as a second vertex on the inlet plane, a second inlet area of the second half of the inlet occupies 80-200 degrees of the inlet plane about the second vertex, and a second of the at least two axial flow backflow ports occupies 10-40 degrees of the inlet plane about the second vertex.

21. An axial inlet, radial outlet supercharger, comprising:

an inlet axis centered between the rotor mounting recesses;

a triangular outlet in the outlet plane;

an inlet in the inlet plane;

lobed rotors, each lobed rotor comprising a rotation axis parallel to the inlet axis,

wherein the lobes sequentially mesh along the inlet axis when the rotors rotate, wherein respective lobes are twisted along the length of their respective rotor, and wherein the lobes are timed to fluidly seal the inlet from the outlet; and

at least two backflow ports in the tubular housing.

22. The supercharger of claim 21 , wherein the at least two backflow ports are axial flow back flow ports in the inlet plane.

23. The supercharger of claim 21 , wherein the at least two backflow ports are radial flow back flow ports in the outlet plane.

24. The supercharger of claim 21 , wherein the at least two backflow ports are axial flow back flow ports in the inlet plane, and wherein the supercharger further comprises at least two radial flow back flow ports in the outlet plane.

25. The supercharger of any one of claims 22-24, wherein the at least two backflow ports occupy a backflow port area Ap_ort in the tubular housing determined by:

where Pi is an inlet pressure, P₂ is a maximum pressure ratio of the outlet, Ti is an inlet temperature, T₂ is an outlet temperature, R is a gas coefficient, NRPM is a maximum speed in rotations per minute of the rotors in the supercharger, V-rransferVoiume is a volume of air transferred, a is a speed of sound at a given inlet temperature Ti, γ is a ratio of specific heat at a constant pressure and constant volume.

26. The supercharger of claim 25, wherein the at least two backflow ports occupy an ideal port area Aip_ort in the range of one fourth to four times the backflow port area Ap_ort.

27. The supercharger of claim 26, wherein the ideal port area Aip_ort is one half to two times the backflow port area Ap_ort.

28. The supercharger of claim 27, wherein the ideal port area Aip_ort is two thirds of the

backflow port area Ap_ort.

29. The supercharger of any one of claims 22 or 24, wherein each of the at least two axial flow backflow ports is a slot having a profile matching a segment on an involute curve.

30. The supercharger of any one of claims 22-24, wherein each of the at least two axial flow back flow ports and each of the at least two radial flow backflow ports is one of a rectangular slot, an oval hole, a circular hole, or a slot having four sides, each of the four sides being an arc of a circle.

31. The supercharger of claim 21 , wherein each lobed rotor rotates to move a lobe on the rotor, and the lobe rotates 210-280 degrees to complete an inlet phase, and the lobe rotates 20-50 degrees to complete a dwell phase, and the lobe rotates 20-40 degrees to complete a seal phase, and the lobe rotates 25-50 degrees to complete a backflow phase, and wherein the lobe rotates 200-220 degrees to complete an outlet phase.

32. The supercharger of claim 21 , wherein each lobed rotor rotates to move a lobe on the rotor, and the lobe rotates 210-280 degrees to complete an inlet phase, and the lobe rotates 0-50 degrees to complete a dwell phase, and the lobe rotates 15-70 degrees to complete a seal phase, and the lobe rotates 20-70 degrees to complete a backflow phase, and wherein the lobe rotates 200-220 degrees to complete an outlet phase.

33. The supercharger of claim 21, wherein each lobed rotor rotates to move a lobe on the rotor, and the lobe rotates 210-280 degrees to complete an inlet phase, and the lobe rotates 20-50 degrees to complete a dwell phase, and the lobe rotates 10-50 degrees to complete a seal phase, and the lobe rotates 20-80 degrees to complete a backflow phase, and wherein the lobe rotates 200-220 degrees to complete an outlet phase.

34. The supercharger of any one of claims 21-24 or 31-33, wherein each of the at least two backflow ports are shaped to open in 10 to 15 degrees of lobe rotation.

35. The supercharger of any one of claims 21-24 or 31-33, wherein each of the at least two backflow ports are shaped to open in 30 to 40 degrees of lobe rotation.

36. The supercharger of any one of claims 21-24 or 31-33, wherein each of the at least two backflow ports are shaped to open in 10 to 40 degrees of lobe rotation.

37. The supercharger of any one of claims 21-24, wherein the at least two backflow ports are sized to be fully blocked by respective lobes when the lobes rotate in front of respective ones of the at least two backflow ports.

38. The supercharger of any one of claims 21-24, wherein each lobe has a profile, and

wherein each of the at least two backflow ports are shaped as segments of the lobe profile.

39. The supercharger of claim 21, further comprising a front plate separated from the inlet wall by a tuning distance.

40. The supercharger of claim 39, further comprising a floor between the inlet wall and the front plate, the floor f uidly separating the inlet from the at least two backflow ports.

41. The supercharger of claim 39, further comprising a pass-through in the front plate, the pass-through aligning with each of the at least two backflow ports.

42. The supercharger of claim 41, further comprising a recirculation conduit 112 coupled to the pass-through.

43. The supercharger of any one of claims 21-24 further comprising:

an intercooler comprising an inlet and an outlet, the intercooler connected to receive blown air from the outlet of the supercharger and connected to cool and expel the received air as backflow air; and

conduits connecting the backflow ports of the supercharger to the outlet of the

intercooler to receive the backflow air, wherein the lobed rotors comprise a first rotatable rotor and a second rotatable rotor, wherein each of the first rotor and the second rotor comprise at least three lobes, wherein a respective gap is formed between each adjacent lobe,

wherein, when a gap is aligned, the backflow ports are oriented to provide cooled air from the intercooler to an adjacent gap,

wherein the adjacent gap is sealed from the inlet and from the outlet when the cooled air is provided to the adjacent gap.

44. The supercharger of claim 43:

wherein the first rotor comprises at least a first lobe and a second lobe,

wherein the second rotor comprises at least a third lobe and a fourth lobe,

wherein the at least two backflow ports comprise a first backflow port and a second backflow port,

wherein the first backflow port is sealed by the first lobe when backflow air is exposed to the second backflow port and to a gap between the third lobe and the fourth lobe, and

wherein the second backflow port is sealed by the fourth lobe when the backflow air is exposed to the first backflow port and to a second gap between the first lobe and the second lobe.

45. The supercharger of claim 43, wherein the supercharger further comprises at least two radial flow back flow ports in the outlet plane, and wherein the conduits further connect the radial flow back flow ports to the outlet of the intercooler.

46. The supercharger of claim 21, wherein the supercharger has a thermal limit of 150

degrees Celsius and an outlet pressure to inlet pressure pressure ratio of 4.4: 1.

47. The supercharger of claim 21, wherein the respective lobes are twisted along the length of their respective rotor from 60-150 degrees.

48. The supercharger of claim 21, wherein the each one of the lobed rotors comprises three lobes, four lobes, or five lobes.

49. The supercharger of any one of claims 21, 22, 24, or 48, wherein, considering a center point of a first of the two rotor mounting recess as a central vertex on the inlet plane, one half of the inlet occupies 80-200 degrees of the inlet plane, and a first of the axial flow backflow ports occupies 10-40 degrees of the inlet plane.

50. The supercharger of claim 49, wherein the first of the at least two axial flow backflow ports occupies 10-15 degrees of the inlet plane.

51. The supercharger of claim 49, wherein the inlet is separated by 82-190 degrees from the first of the at least two axial flow backflow ports.

52. The supercharger of claim 49, wherein, considering a center point of a second of the two rotor mounting recess as a second vertex on the inlet plane, the second half of the inlet occupies 80-200 degrees of the inlet plane about the second vertex, and a second of the axial flow backflow ports occupies 10-40 degrees of the inlet plane about the second vertex.