Patent Application
20100297895
In some pump applications, it may be desirable to pump a relatively large volume of water at a relatively low pressure. Some examples of such applications may include marine vessel propulsion and irrigation systems. It is also desirable for the pump to operate efficiently.
However, in some cases, unavoidable inefficiencies may be introduced. For example, in a jet propulsion system for hydrofoil marine vessels, the inlet must be located below the hydrofoils. If the propulsion system is located in the hull, then water must be raised from the inlet to the pump, thereby reducing inlet pressure, adding other unrecoverable losses, and introducing undesirable pitching moments resulting from the high thrust line. Increasing efficiency in such cases entails matching a ratio of pump outlet flow velocity to marine vessel velocity. However, matching velocity ratios for efficiency currently involves large gears, large pumps, and large water flows.
The foregoing examples of related art and limitations associated therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.
The following embodiments and aspects thereof are described and illustrated in conjunction with systems and methods which are meant to be illustrative, not limiting in scope. In various embodiments, one or more of the problems described above in the Background have been reduced or eliminated, while other embodiments are directed to other improvements.
In a non-limiting, illustrative embodiment, a marine propulsion system includes a pump housing that is configured to be disposed below a waterline of a marine vessel and a centrifugal pump assembly that is disposed in the pump housing. The centrifugal pump assembly includes an inlet pump stage configured to receive inlet water and to discharge impulse water. The centrifugal pump assembly also includes an outlet pump stage that includes an impulse turbine wheel configured to rotate about an axis responsive to the impulse water and an outlet pump stage impeller integral with the impulse turbine wheel. The outlet pump stage impeller is configured to rotate about the axis.
According to a non-limiting, illustrative aspect, the inlet pump stage can include an inlet pump stage impeller that is configured to rotate about the axis. According to another non-limiting, illustrative aspect, the impulse turbine wheel and the outlet pump stage impeller can be portions of a single assembly. According to another non-limiting, illustrative aspect, the impulse turbine wheel and the output pump stage impeller can be separate components that are attached to each other. According to another non-limiting, illustrative aspect, the inlet pump stage can be configured to discharge the impulse water at a first pressure and a first volume flow rate, the impulse turbine wheel can be configured to discharge water at a second pressure that is less than the first pressure, and the outlet pump stage impeller can be configured to discharge water at the second pressure and a second volume flow rate that is proportionally greater than the first volume flow rate.
In another non-limiting, illustrative embodiment, a marine propulsion system includes a pump housing that is configured to be disposed below a waterline of a marine vessel. The pump housing defines an inlet port and an outlet nozzle. The marine propulsion system also includes a centrifugal pump assembly that is disposed in the pump housing. The centrifugal pump assembly includes an inlet pump stage that is configured to receive inlet water from the inlet port of the pump housing and to discharge impulse water. The centrifugal pump assembly also includes an outlet pump stage. The outlet pump stage includes an impulse turbine wheel that is configured to rotate about an axis responsive to the impulse water and to discharge water to the outlet nozzle. The outlet pump stage also includes an outlet pump stage impeller that is integral with the impulse turbine wheel. The outlet pump stage impeller is configured to rotate about the axis and to discharge water to the outlet nozzle.
In another non-limiting, illustrative embodiment, a centrifugal pump impeller assembly includes an impulse turbine wheel that is configured to rotate about an axis and a centrifugal pump impeller that is integral with the impulse turbine wheel. The centrifugal pump impeller is configured to rotate about the axis.
In addition to the illustrative embodiments and aspects described above, further embodiments and aspects will become apparent by reference to the drawings and by study of the following detailed description.
Illustrative embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.
By way of overview, illustrative marine propulsion systems are disclosed. In some illustrative embodiments, a marine propulsion system can efficiently convert rotary motion of a prime mover operating near a maximized or optimized efficiency with or without intermediate gearing to a centrifugal pump assembly that can match the flow and velocity of a discharged water jet to a marine vessel's speed for maximized propulsive efficiency. Applications for such an illustrative embodiment of a marine propulsion system can include a propulsion system for any type of marine vessel, such as without limitation a hydrofoil. Other applications of an illustrative embodiment of a marine propulsion system include an outboard motor for a marine vessel, such as without limitation a boat. Illustrative embodiments of a centrifugal pump impeller assembly suitably may be applied to any application whatsoever in which efficient conversion of energy from a high-pressure source is desired.
Still by way of overview and referring to
Still by way of overview, it will be appreciated that the impulse turbine wheel 12 is driven by the impulse water (as will be explained below). Because the impeller 16 of the outlet pump stage 14 is integral with the impulse turbine wheel 12, rotation of the impulse turbine wheel 12 causes rotation of the impeller 16 of the outlet pump stage 14. Illustrative details of non-limiting embodiments will be set forth below.
Referring additionally to
In some embodiments, if desired the pump housing 52 may include steerable deflector vanes 58 configured to deflect water discharged from the outlet nozzle 56 in a yaw plane. Thus, the steerable deflector vanes 58 can help provide a means for steering and/or maneuvering the marine vessel. In other embodiments the entire marine propulsion system 50 may be rotated for steering.
In some embodiments, if desired the pump housing 52 can include a closeably openable reverse thrust port 60. In some embodiments the reverse thrust port 60 may be defined in a forward portion of the pump housing 52. The reverse thrust port 60 is configured to discharge therethrough at least a portion of outlet water discharged from the outlet pump stage 14. The reverse thrust port 60 can be opened and closed with a cover 61. When the reverse thrust port 60 is opened, a portion of the outlet water discharged from the outlet pump stage 14 can be discharged in a direction substantially opposite that of the water discharged from the outlet nozzle 56 of the pump housing 52. In addition, if desired the steerable deflector vanes 58 may be closed. Closing the steerable deflector vanes 58 reduces the amount of outlet water discharged through the outlet nozzle 56, thereby increasing the amount of outlet water available for discharge through the reverse thrust port 60 for reverse thrust purposes. Thus, reverse thrust can be provided, thereby helping to slow forward motion of the marine vessel.
Referring additionally to
In some embodiments the impeller 24 is operationally coupled for rotation by a prime mover that is located distal or remote from the inlet pump stage 18. For example, the impeller 24 may be rotated by an engine (not shown) of a marine vessel. Given by way of illustration and not of limitation, the centrifugal pump 10 may be located near, in, or below a plane of a foil (not shown) of a hydrofoil (not shown). In such an application the prime mover may be an internal combustion engine or a jet engine that rotates a shaft 26 about the axis a with or without intermediate gearing. It will be appreciated that configurations of some embodiments may use an engine with a horizontal shaft. Such configurations thus entail use of a right angle gear. However, weight and cost impact of such gearing is minimal. The shaft 26 is sealed with a shaft seal 23 (
In some other embodiments, the impeller 24 may be operationally coupled for rotation by a prime mover that is located proximate the inlet pump stage 18. For example, the inlet pump stage 18 may include an electric motor that is configured to rotate the impeller 24. In such an application and given by way of non-limiting example, a stator winding (not shown) may be provided in the vicinity of the impeller 24 and may be electrically connected to an electrical source (not shown). The impeller 24 may include permanent magnets, thereby defining a rotor of a DC electric motor.
Regardless of location or type of prime mover that rotates the impeller 24, the impeller 24 includes an inlet port 28, vanes 29, and discharge ports 30. The inlet port 28 is coaxial with the axis a and the discharge ports 30 are substantially normal to the axis a. The impeller 24 rotates about the axis a at the rotational speed of the prime mover. The inlet pump stage 18 is in hydraulic communication with the inlet port 54 of the pump housing 52, and the impeller 24 is configured to receive inlet water from the inlet port 54 of the pump housing 52 via the inlet port 28 of the inlet pump stage 18. Inlet water enters through the inlet port 28, is accelerated by the vanes 29 during rotation about the axis a, and is discharged at the first pressure and a first volume flow rate as the impulse water through the discharge ports 30. Because of relative positioning of the discharge ports 30 and the impulse turbine wheel 12, the impulse water that is discharged at the first pressure through the discharge ports 30 is discharged in hydraulic communication into the impulse turbine wheel 12.
Referring additionally to
The impulse turbine wheel 12 suitably is any impulse turbine known in the art. Given by way of non-limiting example, in some embodiments, the impulse turbine wheel 12 is a Pelton turbine wheel. Spoon-shaped buckets 32 are mounted around an interior of an edge of the impulse turbine wheel 12. As the impulse water flows into the bucket 32, the direction of the impulse water velocity changes to follow the contour of the bucket 32. When the impulse water contacts the bucket 32, the impulse water exerts pressure on the bucket 32 and the impulse water is decelerated as it does a “u-turn” and flows out the other side of the bucket 32 at a lower velocity and at a second pressure that is less than the first pressure. In the process, the impulse water's momentum is transferred to the impulse turbine wheel 12. This impulse does work on the impulse turbine wheel 12, thereby causing the impulse turbine wheel 12 to rotate about the axis a. Water is discharged from the impulse turbine wheel 12 at the second pressure.
The impeller 16 of the outlet pump stage 14 is integral with the impulse turbine wheel 12. Thus, rotation of the impulse turbine wheel 12 about the axis a causes rotation of the integral impeller 16 of the outlet pump stage 14 about the axis a. The outlet pump stage 14 is configured to discharge outlet water at the second pressure that is less than the first pressure and a second volume flow rate that is proportionally greater than the first volume flow rate. Relationships between the first pressure, the first volume flow rate, the second pressure, and the second volume flow rate will be explained further below.
The impeller 16 of the outlet pump stage 14 suitably is a centrifugal pump impeller. The outlet pump stage 14 includes an inlet port 34, vanes 36, and discharge ports 38. The vanes 36 are attached to a central retaining sleeve 37. The shaft 26 is freely received within the retaining sleeve 37 without being attached to the retaining sleeve 37. However, the impeller 16 is axially constrained on the shaft 26. Thus, the shaft 26 can rotate freely without causing the unattached retaining sleeve 37 to rotate. The impeller 16 thus is not directly rotated by the shaft 26. The inlet port 34 is coaxial with the axis a and the discharge ports 38 are substantially normal to the axis a. The outlet pump stage 14 is in hydraulic communication with the inlet water. The inlet port 34 of the outlet pump stage 14 receives the inlet water through the inlet port 54 defined in the pump housing 52. Thus, in some embodiments the inlet pump stage 18 and the outlet pump stage 14 both receive the inlet water through a common inlet—that is, the inlet port 52 of the pump housing 50. The impeller 16 rotates about the axis a at the rotational speed of the impulse turbine wheel 12. Inlet water enters through the inlet port 34, is accelerated by the vanes 36 during rotation about the axis a, and is discharged through the discharge ports 38.
The impeller 16 is integral with the impulse turbine wheel 12. Thus, the impeller 16 rotates about the axis a at the speed of rotation of the impulse turbine wheel 12. In some embodiments the impeller 16 can be integral with the impulse turbine wheel 12 by being portions of a single assembly. For example, a lower disc of the impulse turbine wheel 12 can also be a top disc of the impeller 16. In some other embodiments, the impeller 16 can be integral with the impulse turbine wheel 12 by being separate components that are attached to each other. For example, the bottom disc of the impulse turbine wheel 12 and the top disc of the impeller 16 can be attached to each other as desired, such as by welding, with fasteners, or the like. That is, the impulse turbine wheel 12 can be mounted on the impeller 16. In such embodiments, it is desirable to minimize any leakage that may occur between the bottom disc of the impulse turbine wheel 12 and the top disc of the impeller 16.
Thus, in an illustrative hydrofoil marine propulsion application given by way of example and not of limitation, an inlet pump stage located in a pump housing below the foils is driven with a vertical shaft rotating at engine speed. An inlet located in the pump housing below an impeller of the inlet pump stage helps permit maximized pressure recovery. The output of the inlet pump stage drives a coaxial turbine mounted on an impeller of an outlet pump stage using impulse water via an annular inlet around the outlet of the inlet pump stage. The output of the outlet pump stage and the turbine exit through a housing and discharge port nozzle such that the volume and pressure of the discharged water jet result in an optimized velocity ratio for a jet located near the foil plane. While an illustrative hydrofoil marine propulsion application has been given by way of non-limiting example, the geometry of the centrifugal pump is configured such that the inlet and the discharge port nozzle may be embedded in a hull of a displacement vessel.
Conservation of energy principles can be applied to help tailor efficiency for a desired application. Given by way of illustration only and not of limitation, the following discussion explains conservation of energy and efficiency in the context of propulsion of a marine vessel with water discharged from the centrifugal pump 10 in which the inlet stage pump is driven by an engine of the maritime vessel. The purpose is to obtain the most efficient jet velocity ratio for propulsion.
In such a context, the following relationships exist:
P0=pressure of inlet water;
Q1=volume flow rate from the inlet pump stage (that is, the first volume flow rate);
P1=outlet pressure of the inlet pump stage and inlet pressure of the turbine (that is, the first pressure);
P2=outlet pressure of the turbine and outlet pressure of the outlet pump stage (that is, the second pressure); and
Q2=volume flow rate from the outlet pump stage (that is, the second volume flow rate).
In such a context output power less any input power losses is a function of outlet pressure of the outlet pump stage and volume flow rate of the turbine and the outlet pump stage. Also, required horsepower to propel the marine vessel (or boat) is a function of boat drag Db times boat velocity Vb. Horsepower of the jet of water discharged from the centrifugal pump is a function of jet thrust Tj times jet velocity Vj. Thus, jet thrust Tj and jet velocity Vj can be defined as functions of outlet pressure of the outlet pump stage and volume flow rate of the inlet pump stage and the outlet pump stage:
P0×(Q1+Q2)≈P2×(Q1+Q2) (1)
D
b
×V
b
=T
j
×V
j
≈P
2×(Q1+Q2) (2)
In such an application, an objective can be to adjust the jet velocity Vj by the second pressure P2 and the second volume flow rate Q2 to achieve an optimized and/or maximized propulsive efficiency. For example, referring to
Referring additionally to
Referring now to
While a number of illustrative embodiments and aspects have been illustrated and discussed above, those of skill in the art will recognize certain modifications, permutations, additions, and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions, and sub-combinations as are within their true spirit and scope.
