Roots blower or vacuum pump with synchronous suction flow and discharge flow

Abstract

The invention discloses a Roots blower or a vacuum pump (called Roots blower for short) with synchronous suction flow and discharge flow, which can reduce airflow speed pulsation, noise, vibration, steep (NVH) and improve fan efficiency. Generally, a Roots blower or vacuum pump with a SIDF has a pair of multi-bladed rotors engaged by a timing gear, the rotors having the same number of blades, and mounted in a housing cavity having an offset suction inlet and an offset discharge outlet. Fluids sucked, captured, backfilled and discharged by two air cavities formed by adjacent blades of each rotor and inner walls along two side surfaces of the shell wall are synchronized, and a suction inlet and a discharge outlet are respectively provided with center lines parallel to each other; the center line of the suction inlet and the center line of the discharge outlet are reversely deviated from each other; wherein the offsets respectively provide simultaneous fluid suction for both sides at the suction inlet and simultaneous fluid backfill and discharge for both sides at the discharge outlet.

Description

Technical Field

[0001] The present invention relates to twin-rotor multi-lobe blowers or vacuum pumps, commonly known as rotary lobe, Roots blowers or superchargers (such as those used for internal combustion engine supercharging), and more particularly to a Roots blower (referred to herein as a SIDF Roots blower) or vacuum pump with synchronized inlet and outlet flows for reducing air flow velocity pulsations and induced vibration, noise and harshness (NVH) and improving blower efficiency. Background Art

[0002] Structurally, conventional Roots blowers or vacuum pumps consist of two identical and parallel rotors having the same multi-lobe (two, three or four) blades that mesh with each other within an airtight housing. Cavities are formed within the housing and have inlet and outlet ports (each with a centerline that is generally aligned), and the inlet and outlet ports are typically arranged on opposite sides of the housing cavity with their port centerlines located midway between the two rotor axes. The two rotors rotate in opposite directions and are kept in sync but not in contact by a set of timing gears within the housing. Gas moves outward through the air cavities formed by the blade profile and the two inner sidewalls of the housing from the suction port to the discharge port, and the gas displacement is mainly determined by the total air cavity volume per unit rotor speed, known as the CFR (cubic feet per revolution, i.e., a measure of volumetric flow rate) of the Roots blower.

[0003] The operating principle of a conventional Roots blower can be illustrated by one air cavity in the complete compression cycle of the three-lobe Roots blower shown in FIGS. 1 to Figure 5 First, let's focus on the top rotor. When air cavity A opens to the blower suction port during its outward rotation from the inlet port to the outlet port, gas first enters the cavity formed between two adjacent lobes of the top rotor and the inner wall of the surrounding housing. As it continues to rotate to the Figure 2 blade position shown, air cavity A completes capturing the gas, and then as shown in Figure 3 FIG., air cavity A is transported from the suction side of the blower to the discharge side, noting that no gas compression or air cavity volume change occurs during these two stages. Figure 3 A little later, when air cavity A opens to the outlet port ( Figure 4 fully opened), a series of compression waves (shock waves) and induced backflows rush into air cavity A due to the sudden opening to the higher outlet pressure, similar to the flow that occurs when the diaphragm in a shock tube suddenly ruptures [References 1 and 2].

[0004] Reference 1. Huang, P., "Airflow Pulsation: Shock Tube Mechanism". International Compressor Engineering Conference, Purdue University, 2012. Reference 2. Huang, P., "Undercompression: Constant Volume Process or Adiabatic Process". International Compressor Engineering Conference, Purdue University, 2012.

[0005] The shock wave sweeps across the gas in chamber A and almost instantaneously compresses it to the outlet gas pressure. Then, as Figure 5 shown, the top vane meets and meshes with the vane from the bottom rotor, displacing the compressed gas to the outlet port and returning it to the inlet suction position to start the next compression cycle.

[0006] The exact same cycle occurs for the bottom rotor. As Figure 2 shown, when chamber B opens to the blower inlet, the gas enters the cavity formed between the adjacent vane of the bottom rotor and the inner wall of the housing. However, due to the 60-degree angular misalignment of the top and bottom vanes of the three-lobe rotor (90 degrees for a two-lobe rotor and 45 degrees for a four-lobe rotor), the flow unit B on the lower side is misaligned by 60 degrees with respect to the flow unit A on the upper side. In other words, the top flow path shown as A and the bottom flow path B are like two independent displacement blowers operating in parallel. They share the same inlet and the same outlet, but the A and B chambers are misaligned by 60 degrees. The unique shock wave compression mechanism of the Roots blower and the operating mode where the upper and lower chambers are in parallel but misaligned by 60 degrees will inevitably generate two types of airflow pulsations: the gas pressure pulsation at the blower outlet caused by the pressure difference between the inlet and outlet, and the gas velocity pulsation at the blower's shared suction and discharge ports caused by the continuous up-and-down swing of the flow velocity direction due to the misalignment (non-synchronization) of the top and bottom chambers, as shown by the small white arrows in Figure 1 , Figure 2 and Figure 4 , Figure 5 . It can be seen that the amplitude of the change in the velocity direction of the traditional Roots is quite large, averaging over 90 degrees.

[0007] The new mechanisms and solutions proposed for the first type of air flow pulsation (pressure pulsation) have been described in References [3, 4]. The focus of the present invention is to address the second type of air flow pulsation - the air flow velocity pulsation at the blower suction and discharge ports, which is caused by the continuous up-and-down swinging of the air flow direction. For a three-lobe Roots blower, the pulsation frequency is equal to: blower RPM (rotational speed) x 2 (number of rotors) x 3 (number of blades per rotor). As the rotational speed and the number of blades increase, due to flow inertia (Newton's law of inertia), it becomes more difficult for the high-frequency air flow to change direction up and down (because of inertia lag), respectively resulting in imperfect filling of the rotating air cavities at the blower suction and discharge ports with air inflow and imperfect filling with air backflow, thereby enhancing the first type of air flow pulsation and leading to poor NVH and blower efficiency. Reference 3. Huang, P., Yonkers, S., "Roots Blower or Vacuum Pump with Shunt Pulsation Trap", U.S. Patent No. 9,140,260, 2015. Reference 4. Huang, P., Yonkers, S., Hokey, D., "Controlling Air Flow Pulsation Using Shunt Pulsation Trap". International Compressor Engineering Conference, Purdue University, 2014, 2014. Summary of the Invention

[0008] An object of the present invention is to provide a Roots blower or vacuum pump with synchronous inlet flow and discharge flow (SIDF), which has synchronous inlet flow and discharge flow (SIDF) for reducing air flow velocity pulsation at the source.

[0009] Another object of the present invention is to provide a Roots blower or vacuum pump with synchronous inlet flow and discharge flow (SIDF), which can achieve higher blower volumetric efficiency and adiabatic efficiency.

[0010] Another object of the present invention is to provide a Roots blower or vacuum pump with synchronous inlet flow and discharge flow (SIDF), which can achieve higher rotational speed and higher blower efficiency at high rotational speed.

[0011] To achieve the above objects, the present invention adopts the following technical solutions: A Roots blower or vacuum pump with synchronous inlet flow and discharge flow (SIDF), comprising: A housing wall having a suction port, a discharge port, and a cavity formed therein; and Two multi-lobe rotors with the same number of blades are located in the cavity, meshed with each other through a pair of timing gears to rotate synchronously in opposite directions, so that the fluid flows from the suction port to the discharge port; and The fluid is synchronously inhaled, captured, backfilled, and discharged by two air cavities formed by the adjacent blades of each rotor and the inner walls of two sides along the cavity wall, where the suction port and the discharge port each have centerlines parallel to each other, and the centerline of the suction port and the centerline of the discharge port are offset from each other; the offset provides fluid entry into the two air cavities for the two sides simultaneously at the suction port and fluid backfilling and discharge from the two air cavities for the two sides simultaneously at the discharge port. Thus, the Roots blower reduces airflow velocity pulsation and induced NVH at the source, improves the blower efficiency, and at the same time maintains a light weight and a compact size.

[0012] The rotor blades are straight in their axial directions, and each rotor has at least 2 or more blades.

[0013] The rotor blades are twisted in their axial directions, and each rotor has at least 3 or more blades.

[0014] The centerline of the suction port and the centerline of the discharge port have a total angular offset of 90 degrees for a two-blade rotor, 60 degrees for a three-blade rotor, or 45 degrees for a four-blade rotor.

[0015] Advantages of the present invention: A Roots blower or vacuum pump provided by the present invention can reduce and even eliminate airflow velocity pulsation without increasing the overall size of the blower, and can achieve higher blower volumetric efficiency and adiabatic efficiency, especially can achieve higher rotational speeds and higher blower efficiency at high rotational speeds.

[0016] A Roots blower or vacuum pump with synchronous intake and discharge flows (SIDF) provided by the present invention can substantially reduce flow velocity pulsation and induced NVH at the source, improve the blower efficiency, maintain a light weight and a compact size, and is applicable to high-speed and high-pressure ratio applications at the same time.

[0017] These and other aspects, features, and advantages of the present invention will be understood with reference to the accompanying drawings and detailed description herein, and will be realized by various elements and combinations specifically pointed out in the appended claims. It should be understood that the above summary, the following brief description of the drawings, and the detailed description of the exemplary embodiments are all illustrative of the exemplary embodiments of the present invention and not limitations of the present invention. Description of the Drawings

[0018] Figures 1 to Figure 5 (Prior art) A side cross-sectional view of a conventional Roots blower, showing a schematic diagram of an air inlet and an air outlet with aligned centerlines and each stage of its compression cycle.

[0019] Figure 1 is a schematic structural diagram of the suction state of a traditional Roots blower. Figure 2 is a schematic structural diagram of the capture state of a traditional Roots blower Figure 3 is a schematic structural diagram of the delivery state of a traditional Roots blower Figure 4 is a schematic structural diagram of the backfill and compression state of a traditional Roots blower Figure 5 is a schematic structural diagram of the exhaust state of a traditional Roots blower Figures 6 to 10 shows a side cross-sectional view of the SIDF Roots blower according to the first embodiment of the present invention, showing that the centerlines of the air inlet and the air outlet are relatively offset by 60 degrees to achieve synchronous air intake and synchronous exhaust in the upper and lower air cavities, and the various synchronous stages of its Roots compression cycle.

[0020] Figure 6 is a schematic structural diagram of the synchronous suction state of the SIDF Roots blower of the present invention Figure 7 is a schematic structural diagram showing that the A air cavity of the traditional Roots blower has just been captured alone while the SIDF Roots blower of the present invention has not been captured yet Figure 8 is a schematic structural diagram of the synchronous capture state of the A and B air cavities of the SIDF Roots blower of the present invention Figure 9 is a schematic structural diagram of the synchronous delivery state of the A and B air cavities of the SIDF Roots blower of the present invention Figure 10 is a schematic structural diagram of the synchronous backfill and compression state of the A and B air cavities of the SIDF Roots blower of the present invention Figure 11 and Figure 12 respectively show the key components and relationships on the side cross-section of the SIDF Roots blower according to the first embodiment of the present invention. Detailed Description of the Invention

[0021] It should be noted that although the illustrations and descriptions in the present invention are directed to a straight three-lobe Roots blower or vacuum pump, the principle can be applied to other types of Roots blowers with different numbers of blades, such as two-lobe, four-lobe or five-lobe, etc. In addition, as long as the two rotors have the same number of blades, the blade shape can be straight or axially twisted. The principle can also be applied to other fluid such as Roots pumps or gear pumps for liquid media, the latter using an involute blade shape to give the blade shape the gear function of rolling interface contact. In addition, a Roots expander is also a variant of the above, used for shaft power applications resulting from a drop in medium pressure.

[0022] As a brief introduction to the principle of the present invention, Figures 6 to 10Once again shows the complete compression cycle of a three-lobe Roots blower, which has an intake port and an exhaust port with a relative offset of the centerlines, such that the upper and lower sides simultaneously inhale and exhale airflows (SIDF). As the name implies, SIDF is used to compensate for the phase difference between the upper and lower sides during inhalation (the same applies to the phase difference between the exhaust backflow and the upper and lower sides of the exhaust airflow), thereby eradicating the airflow velocity pulsations caused by the up-and-down swinging of the airflows at the intake and exhaust ports. Structurally, this is achieved by angularly displacing the centerline position of the suction port of the three-vane rotor by 30 degrees (45 degrees for a two-vane rotor and 22.5 degrees for a four-vane rotor) and angularly displacing the centerline position of the exhaust port by 30 degrees in the direction opposite to the angular displacement of the suction port, that is, the total angular offset between the centerline positions of the intake and outlet ports is 60 degrees (90 degrees for a two-vane rotor and 45 degrees for a four-vane rotor).

[0023] As Figures 6 to 10 shown, the upper rotor air chamber A and the lower rotor air chamber B are in sync during the various stages of inhalation, capture, conveyance, and backfill compression (where Figure 7 shows the intake port before and after a 30-degree offset, as well as the position where air chamber A has just captured air at the old intake port alone while the intake port of the SIDF Roots blower of the present invention has not yet captured air), such that the airflows on the upper and lower sides at the intake port of the blower simultaneously inhale air, and the airflows on the upper and lower sides at the outlet port of the blower simultaneously backfill and exhale air, thereby eliminating the flow direction and pressure difference pulsations caused by the continuous up-and-down swinging of the airflow direction at high frequencies and high flow velocities, and thus improving the volumetric efficiency and adiabatic efficiency of the blower.

[0024] Reference Figure 11 and Figure 12 show typical arrangements of a preferred embodiment of a Roots blower 10 with synchronous intake and exhaust flows (SIDF) 50. Generally, the Roots blower 10 has two parallel rotors 12 and 14, which are respectively mounted on rotor shafts (not shown), where the rotor 12 shaft is driven by an external rotary drive mechanism and synchronously drives the rotor 14 through a set of timing gears (not shown) to mesh but not contact each other, so as to convey gas from the intake port 34 to the exhaust port 38, which is usually arranged on the opposite side of the blower housing wall 30. As an important novel and unique feature of the present invention, the air chambers 22 and 24 in the synchronous intake and exhaust flow (SIDF) device 50 synchronously inhale air starting from the offset intake port 34, and then move along the corresponding two sides 16 and 18 of the inner wall 30 of the housing to complete inhalation synchronously, as Figure 11 shown; similarly, the synchronous exhaust air chambers 26 and 28 synchronously complete backfill and exhaust from the corresponding two sides 16 and 18 of the inner wall 30 of the housing through the offset exhaust port 38, as Figure 12 shown.

[0025] In Figure 11In the illustrated embodiment, the operation of the Synchronous Inlet and Discharge Flow (SIDF) device 50 is as follows. When the upper and lower tips just pass the closed position of the suction port 34, since the suction port is offset by 30 degrees (for a three-blade rotor), the flow of the inhaled gas into the air chambers 22 and 24 of the two sides 16 and 18 is synchronous, and the flow direction of the inhaled gas no longer swings up and down. And since the discharge port 38 is also offset by 30 degrees (in the opposite direction to the offset direction of the suction port), the backflow and discharge flow of the air chambers 26 and 28 of the two sides 16 and 18 are also synchronous, and the air flow direction no longer swings up and down.

[0026] When the Roots blower 10 is equipped with the Synchronous Inlet and Discharge Flow (SIDF) device 50 of the present invention, it is possible to reduce the air flow velocity pulsation and induced NVH at the source, improve the blower efficiency, while maintaining a light weight and compact size, and being applicable to high rotational speed and high pressure ratio applications at the same time.

[0027] Obviously, the present invention provides a Roots blower or vacuum pump with SIDF, which can reduce or even eliminate the air flow velocity pulsation without increasing the overall size of the blower.

[0028] Although the present invention has been described in the context of its specific embodiments, those skilled in the art will understand other alternatives, modifications and variations after reading the above description. Therefore, the appended claims below are intended to cover a wide range of these alternatives, modifications and variations.

Claims

1. A Roots blower or vacuum pump with synchronous suction flow and discharge flow, characterized in that: It includes: a housing wall having a suction port, a discharge port, and forming a cavity therein; and Two multi-blade rotors having the same number of blades are located in the cavity and mesh with each other through a pair of timing gears to rotate synchronously in opposite directions so that the fluid flows through the suction port to the discharge port; and The fluid is synchronously captured by two air cavities formed by adjacent blades of each rotor and the inner walls along the two side surfaces of the cavity wall, wherein the suction port and the discharge port respectively have center lines parallel to each other, and the suction port center lines and the discharge port center lines are offset from each other; the offset provides fluid introduction into the two air cavities for the two side surfaces at the suction port and provides fluid backfilling and discharge from the two air cavities for the two side surfaces at the discharge port, respectively.

2. The Roots blower or vacuum pump with synchronous suction flow and discharge flow according to claim 1, characterized in that: The rotor blades are in a straight line shape in the axial direction thereof, and each rotor has at least 2 or more blades.

3. The Roots blower or vacuum pump with synchronous suction flow and discharge flow according to claim 1, characterized in that: The rotor blades have a twisted shape in the axial direction thereof, and each rotor has at least 3 or more blades.

4. A Roots blower or vacuum pump with synchronous suction flow and discharge flow according to claim 1, wherein the center line of the suction port and the center line of the discharge port are offset by a total angle of 90 degrees for a two-blade rotor, a total angle of 60 degrees for a three-blade rotor, or a total angle of 45 degrees for a four-blade rotor.

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