Patent Application
20080240904
The present invention pertains to rotary pumps for use in compressing or evacuating gaseous matter. More particularly, the present invention pertains to rotationally driving a rotary pump in a manner such that the rotary pump discharges gaseous matter at supersonic velocities.
It is know to utilize centrifugal pumps to compress gaseous matter. Such pumps typically comprise a rotor or impeller that rotates about an axis in manner creating centrifugal force on gaseous matter that is in contact with or contained within the rotor. The centrifugal force on the on the gaseous matter creates a pressure differential that can be used to either evacuate or compress gaseous matter.
The rotor of a centrifugal pump typically comprises a plurality of radially oriented gas passageways or spiral gas passageways, either between rotor vanes or within the rotor. On rotors having spiral gas passageways, the spirals typically swirl in a direction opposite the direction of rotor rotation as the gas passageways extend away from the axis of rotation.
High pressure ratio pumps, such as pumps able to generate pressure ratios in excess of four, typically comprise multiple rotors operating in series (multistage) or utilize piston style pumps in lieu of centrifugal rotors. The use of multiple rotors makes the cost and maintenance of multistage compressors greater than that of single-stage compressors. Piston style pumps are generally not well suited for applications requiring steady-state operation.
The present invention is directed to a single-stage centrifugal pump that is capable of producing steady-state pressure ratios in excess of two, and preferably in excess of four.
In one aspect of the invention, a method of pumping gaseous matter comprises a step of providing a pump rotor having a center axis, an intake port, an exhaust port, and a gas passageway. The gas passageway operatively connects the intake port to the exhaust port. The exhaust port is radially farther from the center axis than is the intake port. The method also includes a step of providing a stator having a chamber that is in gaseous communication with the exhaust port of the pump rotor. The method yet further comprises a step of rotationally driving the pump rotor about the center axis relative to the stator in a manner causing gaseous matter to enter the gas passageway of the pump rotor via the intake port, to gain energy, and to move radially away from the center axis and out of the exhaust port into the chamber of the stator. The gaseous matter has a supersonic velocity relative to the stator upon exiting the exhaust port.
In another aspect of the invention, a method of pumping gaseous matter comprises a step of providing a pump rotor having a center axis, an intake port, an exhaust port, and a gas passageway. The gas passageway operatively connects the intake port to the exhaust port. The exhaust port is radially farther from the center axis than is the intake port. The method also comprises a step of providing a stator having a chamber that is in gaseous communication with the exhaust port of the pump rotor. The method yet further comprises a step of rotationally driving the pump rotor about the center axis relative to the stator in a manner causing gaseous matter to enter the gas passageway of the pump rotor via the intake port, to gain energy, and to move radially away from the center axis and out of the exhaust port into the chamber of the stator. The rotational driving the pump rotor also occurs in a manner such that the exhaust port moves circumferentially about the center axis in a forward direction relative to the stator and the gaseous matter is expelled from the exhaust port having a velocity component in the forward direction relative to the exhaust port.
In yet another aspect of the invention, a method of pumping gaseous matter comprises a step of providing a pump rotor having a center axis, an intake port, an exhaust port, and a gas passageway. The gas passageway operatively connects the intake port to the exhaust port. The exhaust port is radially farther from the center axis than is the intake port. The method also comprises a step of rotationally driving the pump rotor about the center axis in a manner causing gaseous matter to enter the gas passageway of the pump rotor via the intake port, to gain energy, and to move radially away from the center axis and out of the exhaust port. The rotational driving the pump rotor also occurs in a manner such that the exhaust port moves circumferentially about the center axis in a forward direction and the gaseous matter is expelled from the exhaust port having a velocity component in the forward direction relative to the exhaust port.
While the principal advantages and features of the invention have been described above, a more complete and thorough understanding of the invention may be obtained by referring to the drawings and the detailed description of the preferred embodiment, which follow.
Reference characters in the written specification indicate corresponding items shown throughout the drawing figures.
Each gas passageway 16 preferably comprises a converging region 24 and diverging region 26 that are preferably formed by the nozzles. The diverging region 26 lies between the respective exhaust port 14 and the converging region 24. The cross-sectional area of each gas passageway 16 decreases as it extends within the converging region 24 toward the diverging region 26. Conversely, the cross-sectional area of each gas passageway 16 increases as it extends within the diverging region 24 from the end of the converging region 24 toward the respective exhaust port 14. The narrowest portion of each gas passageway 16 preferably lies between its converging region 24 and its diverging region 26 (i.e., at the throat within the nozzle 21) and preferably has an area that is at most one half of the area of the widest portion of the gas passway. However, this ratio can be adjusted by replacing the nozzles with nozzles having a larger or smaller throat areas. As most evident in
In use, the rotor 10 is rotationally driven about axis A-A in the direction R shown in
Preferably, the rotational speed at which the rotor 10 is driven is sufficiently high so as to accelerate gaseous matter within the gas passageways 16 to a speed slightly less than Mach 1.0 as the gaseous matter nears the converging regions 24 of the gas passageways 16. As such, the gaseous matter further accelerates as it passes through the converging regions 24 of the gas passageways 16 and preferably goes supersonic upon entering the diverging regions 26 of the gas passageways, thereby further accelerating within the diverging regions. Thus, gaseous matter is preferably expelled from the exhaust ports 14 of the rotor 10 at a supersonic speed relative to the rotor. As mentioned-above, the nozzles 21 are preferably removable and replaceable with similar nozzles having smaller or larger throat areas. This allows the discharge velocity of gaseous matter to be controlled to account for various intake pressures, back pressures, and properties of the gaseous matter being discharge.
It should be appreciated that gaseous matter discharge from the rotor 10 needs not necessarily have a supersonic velocity relative to the rotor for it to have a supersonic velocity relative to the stator 54. This is because the gaseous matter is discharged into the direction of rotation and therefor has a velocity relative to the stator 54 equal to the discharged velocity from the rotor 10 plus the velocity of the exhaust ports 14 relative to the stator. As such, the gas passageways 16 of the rotor 10 need not necessarily comprises converging and diverging regions 24, 26 for the discharged gaseous matter to have a supersonic velocity discharge velocity relative to the stator 54.
While the present invention has been described in reference to a specific embodiment, in light of the foregoing, it should be understood that all matter contained in the above description or shown in the accompanying drawings is intended to be interpreted as illustrative and not in a limiting sense and that various modifications and variations of the invention may be constructed without departing from the scope of the invention defined by the following claims. For example, when the rotor is used as a vacuum pump as opposed to a compressor, the exhaust ports 16 of the rotor need not discharge into any chamber of a stator and could instead discharge directly into the atmosphere. Thus, other possible variations and modifications should be appreciated.
Furthermore, it should be understood that when introducing elements of the present invention in the claims or in the above description of the preferred embodiment of the invention, the terms “comprising,” “including,” and “having” are intended to be open-ended and mean that there may be additional elements other than the listed elements. Additionally, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. Moreover, use of identifiers such as first, second, and third should not be construed in a manner imposing any relative position or time sequence between limitations. Still further, the order in which the steps of any method claim that follows are presented should not be construed in a manner limiting the order in which such steps must be performed unless such steps must inherently be performed in such order.
