Patent Publication Number: US-2016237978-A1

Title: Gear Pump for Hydroelectric Power Generation

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a gear pump unit for generating hydroelectric power. More specifically, the bidirectional gear pump unit utilizes a modified supercharger to generate electricity. 
     BACKGROUND 
     By applying the simple concept of using water to turn a turbine that in turn turns a metal shaft in an electric generator, a hydroelectric power generator harnesses energy to generate electricity. The turbine is an important component of the hydroelectric power generator. A turbine is a device that uses flowing fluids to produce electrical energy. One of the parts is a runner, which is the rotating part of the turbine that converts the energy of falling water into mechanical energy. 
     There are two main types of hydro turbines, impulse and reaction. Impulse turbines use the velocity of the water to move the runner and discharges the water at atmospheric pressure. There is no suction on the down side of the turbine, and the water flows out the bottom of the turbine housing after hitting the runner. An impulse turbine is generally suitable for high head applications. 
     Reaction turbines develop power from the combined action of pressure and moving water. The runner is placed directly in a water stream flowing over the blades. Reaction turbines are generally used for sites with lower head than compared with the impulse turbines. Reaction turbines must be encased to contain the water pressure, or they must be fully submerged in the water flow. 
     Current hydroelectric power generators use centrifugal devices like propellers and impellers in low (&lt;30 m) and medium (30-300 m) head applications. Head is pressure created by the difference in elevation between the water intake for the turbine and the water turbine. Many propeller and impeller type turbines require high pressure head to perform efficiently, but many geographic locations do not have enough elevation change to create high pressure head. 
     To create head, water can be collected or diverted. So, some systems employ a pump to move water so that it can pass through the turbine. This increases the complexity by having one set of pipes and diversion mechanisms aimed at the turbine, and a second set of such equipment for the pump. 
     SUMMARY 
     The present disclosure proposes an improved gear pump and turbine unit that is capable of moving a large volume of water in a bidirectional manner. The unit can operate efficiently in high and low head applications by leveraging attributes of both impulse and reaction turbines. And, the device is operable fully or partially submerged and can use a siphon effect to operate when not submerged at all. The device can be installed in any orientation, alleviating issues of precise alignment for power generation. 
     In one embodiment, a gear pump unit for hydroelectric power generation may comprise a gear pump ( 131 ). The gear pump ( 131 ) comprises a case ( 131 B) comprising a fluid inlet ( 132 ) and an outlet ( 135 ). A first rotor ( 133 ) is in the case ( 131 B), the first rotor comprising a first plurality of radially spaced teeth ( 133 A,  133 B,  133 C), wherein the first plurality of radially spaced teeth wrap around the first rotor helically in a clockwise direction. A second rotor ( 134 ) is in the case ( 131 B), the second rotor comprising a second plurality of radially spaced teeth ( 134 A,  134 B,  134 C), wherein the second plurality of radially spaced teeth wrap around the second rotor helically in a counter-clockwise direction, and wherein the first plurality of teeth mesh with the second plurality of teeth. A shaft ( 136 ) operatively connects to the first rotor ( 133 ) and to the second rotor ( 134 ). A generator ( 138 ) operatively connects to the shaft ( 136 ). A control module  150  operatively connects to the gear pump ( 131 ) and is configured to selectively rotate the first rotor in a first direction and to selectively rotate the second rotor in a second direction. The control mechanism is further configured to selectively reverse the rotation direction of the first rotor and to selectively reverse the rotation direction of the second rotor. 
     A method of operating a hydroelectric power gear pump unit ( 130 ) comprises the step of supplying a fluid to an inlet ( 132 ) of a gear pump ( 131 ) case ( 131 B). Fluid moves through through a chamber ( 131 A) of the case ( 131 B) by rotating a first rotor ( 133 ) in the case ( 131 B), the first rotor comprising a first plurality of radially spaced teeth ( 133 A,  133 B,  133 C). Fluid moves through the chamber ( 131 A) of the case ( 131 B) by simultaneously rotating a second rotor ( 134 ) in the case ( 131 B), the second rotor comprising a second plurality of radially spaced teeth ( 134 A,  134 B,  134 C). Fluid is expelled through an outlet ( 135 ) of the gear pump case ( 131 B). Electricity is generated by coupling the rotational energy of the first rotor and the rotational energy of the second rotor to a generator ( 138 ). Pumping is performed by reversing the rotating of the first rotor and the second rotor to move the fluid from the outlet ( 135 ) to the inlet ( 132 ). 
     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 claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate principles of the disclosure. 
         FIG. 1A  is a schematic of a high head hydroelectric power generation system. 
         FIG. 1B  is an alternative schematic of a high head hydroelectric power generation system. 
         FIG. 2  is a schematic view of a gear pump unit. 
         FIG. 3  is a schematic of a TVS type supercharger gear pump unit. 
         FIG. 4  is a schematic of a low head application 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present exemplary embodiments, 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. In this specification, upstream and downstream are relative terms that explain a relationship between parts in a fluid flow environment. Water, when flowing according to natural forces, moves from a first upstream location to a second downstream location. When mechanical means intervene, the flow direction can be altered, so the terms upstream and downstream assist with explaining the natural starting point (upstream) with respect to a location water would naturally move to (downstream). 
       FIG. 1A  shows a schematic view of hydroelectric power generation system  10 . In this example, system  10  is a high head system with a dam  100  forming a reservoir  110  of water. System  10  comprises a penstock  120  and a gear pump unit  130 . The penstock  120  may be a tube like structure that extends from upstream of the gear pump unit  130  to the gear pump unit  130 . The penstock  120  is a conduit for water. The penstock  120  may be divided into three main parts. A first leg  120 A of the penstock  120  is placed in reservoir  110 . Reservoir  110  is located in an upstream portion of a river  160 . Top, or second, part  120 B of the penstock  120  is located on the top of a dam  100 . The third leg  120 C of the penstock  120  is located on a downstream side of reservoir  110 . The leg  120 C is extended to an inlet port  132  of the gear pump unit  130  to supply water. The gear pump unit  130  is connected to the penstock  120  to pump water upstream to return water to the reservoir  110 . Further, the gear pump unit  130  may operate in a turbine mode to generate hydroelectricity using the water coming through the penstock  120  from the reservoir  110  to the river  160 . The gear pump  130  may be submerged in water as shown, or may not be submerged fully. As shown in  FIG. 1B , a platform  170  supports the gear pump unit  130  above the river  160  and a tailrace, or fourth leg  120 D, extends out of gear pump unit  130  in to river  160 . The fourth leg  120 D can be alternatively included on the submerged embodiment of  FIG. 1A . 
     The gear pump unit  130  is scalable for pumping air, water, or mixtures of air and water. The gear pump unit  130  is a positive displacement pump modeled on a Roots supercharger. Compared to an automotive supercharger, the inlet and outlet ports are adjusted for providing fluid flow with minimal or no compression. The rotor angles are also adjusted for accommodating the velocity of the water, which is based on the available head. Because the positive displacement pump can be optimized for fluid flow, it can move water, air, or a mixture or water and air. It does not need a pure water stream to operate in turbine or pump modes. 
     The gear pump unit  130  is bidirectional, meaning it can receive water from the reservoir  110  and expel it to a stream  160 . The gear pump unit  130  can also siphon from the stream  160  and pump fluid back to the reservoir  110 . The gear pump unit  130  can also operate in turbine mode to generate electricity. 
     When operating in a forward pump mode, the gear pump unit  130  draws up water from the reservoir  110  through leg  120 A of penstock  120 , and then supplies the same to the leg  120 C of penstock. More specifically, once the gear pump unit  130  is activated, it may suck water up the leg  120 A. The water travels through second leg  120 B, which may be embedded in dam  100  or fitted or retrofitted to the top of the dam  100 , as shown. The suction by gear pump unit  130  draws the water through third leg  120 C. Once sufficient fluid is drawn in to third leg  120 C, then the gear pump unit  130  can cease sucking water in to the penstock  120 . So long as first leg  120 A remains submerged in water, siphon effect will supply water from the reservoir  110  to the gear pump unit  130  through the penstock  120 . Thus, gear pump unit  130  converts from forward pumping mode to turbine mode once siphon effect is established. Should the need arise, gear pump unit  130  can operate in pump mode even after siphon effect is established, for purposes such as pumping down reservoir  110 . 
     By employing a control module  150 , the gear pump unit  130  can receive electronic commands to operate in forward, reverse, or turbine modes. Inclusion of sensors in the control module  150  enables feedback control. 
     Although the placement of penstock  120  in  FIG. 1A  is shown to be around the dam  100  and in open air, it is not be restricted as such. The penstock  120  can also be placed below the water level, fully submerged. Thus the gear pump unit  130  and penstock may be installed in the original dam  100  infrastructure, or it may be retrofitted, or it may be installed directly in a river. It may replace original installation, or supplement its capacity. 
       FIG. 2  shows the gear pump unit  130  in more detail. The gear pump unit  130  comprises a gear pump  131  and a generator  138 . The gear pump  131  comprises an inlet  132 , rotors  133  and  134 , a chamber  131 A, and an outlet  135 . The gear pump unit  130  may be submerged in the water. In addition, the gear pump unit  130  may be positioned partly out of the water. The gear pump  131  is able to avoid cavitation effects by appropriate design of the rotors in the housing. To pump out air and supply water through the gear pump unit  131 , the inlet  132  and the outlet  135  have ports that allow either water or air to travel through the gear pump  131 . The inlet  132  can comprise connectivity to portions of penstock  120 . And, the outlet  135  can comprise connectivity to a tailrace or fourth leg  120 D of penstock to submerge the expulsion point of spent water and to provide access to water during pump mode. A pool can be provided near the outlet of the fourth leg  120 D to facilitate the submersion. 
     Gear pump  131  is a positive displacement pump such as a Roots-type supercharger. Preferably, an Eaton Corporation TWIN VORTICES SERIES TVS helical rotor supercharger. As fluid enters through inlet  132 , rotors  133  and  134  within the chamber  131 A trap the fluid, air or water, between teeth of the rotors and the case  131 B. Case  131 B encases rotors  133  and  134 . As the rotors spin, fluid is expelled out outlet  135 . 
     Rotors  133 ,  134  may be identical in shape. Each rotor  133 ,  134  may have multiple teeth  133 A,  133 B,  133 C,  134 A,  134 B,  134 C. For instance, each rotor in  FIG. 2  has three teeth, though other numbers, such as two or four teeth per rotor, can be used. 
     By comparison, in conventional gear motors and pumps, there are 15-25 teeth. These conventional gears are 1-3 inches in diameter. Since the gears have a relatively small diameter and high tooth count, the amount of water volume moved is small. As a result, the power generated is be limited. In contrast, each rotor of the gear pump  131  has 3-4 teeth having a very large diameter of up to 40 inches. Due to the larger diameter, the gear pump  131  of the present invention pumps a larger volume of water per tooth. In a large hydroelectric application, gear pump unit  131  could comprise a low number of teeth with a 25-40 inch diameter gear. The teeth would have a low diametral pitch and would pump a large volume of water per tooth. The lower number of teeth and larger volume increases the displacement efficiency of the device. The sizes given are exemplary only, with size scaling for application. 
     Also by comparison, conventionally, there are approximately 15-25 teeth on a gear motor or turbine. These teeth are 1-3 inches in diameter. Since the teeth have a relatively small diameter, the amount of water volume displaced is small. As a result, the power generated is limited. In contrast, each rotor of the gear pump  131  has 3-4 teeth having a diameter of 3-6 inches. Due to the larger diameter, the gear pump  131  of the present invention pumps a larger volume of water per tooth. In a large hydroelectric application, gear pump unit  131  could comprise a low number of teeth with a 25-40 inch diameter per tooth. The teeth would have a low diametral pitch and would pump a large volume of water per tooth. The lower number of teeth and larger volume increases the energy efficiency of the hydroelectric power generation. It also increases the speed of rotation of the turbine, which reduces the cost of directly coupled generators. 
     To further reduce cost of materials, the teeth can be made hollow. To help improve efficiency the teeth can be cladded with a corrosion and wear resistant metallic powder, such as Eaton Corporation&#39;s EATONITE. Other materials, including low friction materials, improve aslo the efficiency. Thus, the rotors and or teeth can be coated with materials including IN718, IN625, Cobalt Chrome, Stainless Steel, Titanium alloys, Nickel based super alloys and coatings, ultra high strength steels, and metal matrix nano composites. Thus, the gear pump  131  can be manufactured using laser welding, laser-assisted additive manufacturing, laser surface treatment and processing, additive manufacturing (AM) techniques, and near net shape (NNS) techniques. 
     Volume displacement devices such as gear pumps  131  have much better air/water handling characteristics than traditional turbines. Unlike an Archimedes Screw, an axial turbine system, or a centrifugal system, the gear pump  131  of this disclosure has dual rotors and a helical structure to the rotor. This brings improved efficiency at low or high head applications. In addition, unlike an Archimedes Screw, the twin vortices (TVS) supercharger is housed, allowing it to leverage both impulse turbine characteristics, as by the velocity of water turning the rotors, and reaction turbine characteristics, as by the pressure build in the encasement. The gear pump  131  is also designed to pump bi-directionally, which is not possible with Archimedes screw or prior art impulse or reaction turbines. The TVS is also unaffected by orientation, location, cavitation, tail water, and tail size. 
       FIG. 2  shows the rotor  133  having three teeth,  133 A,  133 B, and  133 C. Similarly, the rotor  134  has three teeth,  134 A,  134 B, and  135 C. Other numbers of teeth are possible. For example, the rotors can have between 2 and 5 teeth each. To facilitate rotor mesh, the rotors  133  and  134  should have an identical number of teeth. Rotors  133 ,  134  can be helical. The teeth can twist over the length of the rotors so that the respective teeth wrap around their respective rotor. As an example, the teeth can twist 120 degrees over the length of the rotor, or the teeth can twist 60 degrees over the length of the rotor. The degree of twist varies based on the head of the application. The degree of twist is also a function of the number of teeth, the outside diameter of the rotor, and the center distance of the rotors. Ideally, the teeth will be optimized to have the largest possible twist for the given application. 
     In addition, each tooth has a diametral pitch, or angle that the tooth projects from its rotor. Compared to an automotive supercharger, a gear pump for a water application has lower diametral pitch. The teeth mesh as the rotors rotate. For example, teeth  133 A,  133 B,  133 C of rotor  133  are twisted clockwise while the teeth  134 A,  134 B,  134 C of rotor  134  are twisted counter-clockwise. Rotors  133 ,  134  are meshed together and geared to rotate in opposite directions. Rotors  133 ,  134  rotate in response to commands from control module  150  for turbine mode or pump mode. 
     The velocity of the water entering the gear pump  131  is a function of the pressure of the water, which is related to the head of the source. The speed at which the device will rotate is a function of the length of the rotor, twist of the teeth, and the pressure of the available fluid. For a given pressure, the smaller the length of the rotor, the faster the rotor will spin. Ideally, the design of the rotor is set up for maximum rotations per minute (RPMs) at a free flow condition. However, because ideal conditions may not be the predominant conditions, the rotor can also be designed for optimizing fluid flow during the most common conditions. When the rotor is optimized, all the pressure in the water is converted into velocity which is then turned into rotational velocity of the rotors. 
     The size of the gear pump will be related to the amount of fluid flow available. The length of rotors  133 ,  134  varies from application to application, based on the head of the water supply. The size of the gear pump  131  is also determined by the length of rotors  133 ,  134 . 
     The gear pump  131  functions as a turbine to generate electricity. This is conducted with the gear pump  131  set in a turbine mode. In this mode, the water flows from the reservoir  110  to the gear pump unit  130  via the penstock  120 . The water flow entering into the inlet  132  of gear pump  131  is trapped in a gap between adjacent teeth of rotor  133 , for example, between teeth  133 A and  133 B. The water flow is trapped in a gap between adjacent teeth of rotor  134 , for example, between teeth  134 A and  134 B. Trapped water flow turns the gear pump  131 . After turning teeth of the gear pump  131 , the used up water flow is carried out of the gear pump  131  through the outlet  135 . The outlet  135  may be triangular shaped to match the shape of the rotors  133 ,  134  for allowing easy exit. 
     When water flow turns rotors of the gear pump  131 , a shaft  136  that is connected to the rotors via transmission gears rotates. The shaft  136  in turn rotates the generator  138 , which can be by direct coupling, or indirect coupling, such as via a pulley or other torque transfer device.  FIG. 2  illustrates direct rotation of the generator, since the shaft  136  is connected to the generator  138 . The generator  138  is a device that converts mechanical energy into electrical energy, and generator  138  may comprise a series of magnets and wires (not shown) to induce a current in the wire to produce electricity. The electricity can be fed to a power grid  137 A for consumption and to a power storage device, such as a battery  137 B. 
     The movement of water in turbine mode has been described. However, air, or a mixture of air and water, can be moved through the gear pump  131  in a similar way. In addition, the fluid flow direction can be reversed, so that water pumps from the stream  160  to the reservoir  110 . 
     The gear pump  131  can be set in a reverse pump mode. In the reverse pump mode, the gear pump  131  functions as a pump to refill reservoir  110 . A variety of control electronics, such as wiring, sensors, transmit, receive, computing, computer readable storage devices, programming, and actuator devices, can be devised to implement control mechanism  150 . Programming implements modes of operation to control gear pump  131 , such as to perform the pump function during off peak time and to perform the turbine mode during peak time. As one example, electricity generated during turbine mode is supplied to grid  137 A during peak electricity use times. During off-peak times, electricity generated using turbine mode is stored in battery  137 B. The stored electricity is returned to power an electric motor  138 B affiliated via pulley hub  15  with input shaft and transmission gears of rotors  133  and  134 . As the electric motor  138 B turns, it also turns the gear pump  131  in a reverse direction. When the gear pump  131  is turned in a reverse direction, it moves water back up to the reservoir  110 . Because the gear pump  131  can move the water back up to the reservoir  110 , the necessity of having a separate pump is negated. As a result, the gear pump unit  130  is constructed with less parts than traditional hydroelectric systems and in a simplified manner. Many gating and diversion techniques are also avoided. The reverse pump mode is usable with any of  FIGS. 1A, 1B, and 4 . If the gear pump is not fully or partially submerged in water, at least a tailrace such as fourth leg  120 D is attached to the outlet  135  or  235  and is submerged in water to enable suction of water from downstream for transfer by the gear pump to upstream. 
       FIG. 3  illustrates one example of a TVS type supercharger manufactured by Eaton Corporation in connection with generator  138  and motor  138 B. With modification, the TVS type supercharger may be used as gear pump  131 . It is an axial input, radial output type having a pulley hub  15  connected to an internal shaft, transmission gears, and rotors  133  and  134 . Fluid enters inlet  132  and exits outlet  135 . Outlet  135  is defined by openings  21 ,  23  and  25  in case  131 B. Details of such a supercharger may be found in U.S. Pat. No. 7,488,164, incorporated herein by reference in its entirety. While not illustrated, a radial inlet, radial output type supercharger may also be used as gear pump  131 . In  FIG. 3 , pulleys are used to transfer rotational energy from the pulley hub  15  to generator  138 , or from motor  138 B to pulley hub  15 . 
     To use the supercharger as a gear pump in pump or turbine mode, modifications should be made to facilitate maximum efficiency. These changes are angle of the rotors  133 ,  134  and timing of inlet  132  and outlet  135 . The rotors should have a low diametral pitch to enable large volumes of water to pass through the unit. The inlet  132 , outlet  135  and rotors must accommodate the incompressible nature of water and, for example, the inlet  132  and outlet  135  port sizes are adjusted and made larger. And, it is possible to adjust the port timing of the inlet  132  and outlet  135  for pump and turbine functions. 
     When in the pump mode, the twist angle of teeth is designed in consideration of the velocity of water. Because of the tradeoffs in pressure at the inlet or outlet during turbine or pump mode, the twist angle should be adjusted for a particular hydropower generation system in view of the frequency of use of pump or turbine mode. Despite this limitation, the operating range of the gear pump  131  is greater than traditional turbines because the design of the gear pump  131  can handle variable flow rates. 
     The “seal time” of the outlet should also be adjusted. The “seal time” refers to the number of degrees that a volume of water moves through a particular phase while trapped in between adjacent teeth of the rotor (herein referred to as control volume). When moving the water, there are three phases to the operation: 1) “initial seal time” is the number of degrees of rotation during which the control volume is exposed to the inlet port; 2) “transfer seal time” is the number of degree of rotation during which the transfer volume is sealed from inlet port; and 3) “outlet seal time” is the number of degrees during which the transfer volume is exposed to the outlet port. In order to conduct the pumping function, the seal time is changed to avoid compression of the water. One method to manipulate the seal time is to reduce or increase the width of the inlet port. The exact method of changing sealing time along with the appropriate seal time is determined to suit needs of a particular hydropower generation system. 
     The computing device  139  controls the gear pump unit  131  by commanding that the control module  150  operate the gear pump  130  in one of turbine mode, suction mode, or pump mode. The implementation of the computing device  139  may differ from one hydroelectric power generation system to the other. For instance, the computing device  139  may be operated based on strict time. In other words, by setting a peak hour and off-peak hour, the gear pump unit can strictly conduct a certain operation during the designated time. 
     Alternatively, the computing device  139  can operate to change the mode based on feedback it receives. In view of this, gear pump unit  130  and computing device  139  can include a network of additional electronics such as an array of additional sensors. The sensors could include, for example, electricity sensors in grid  137 A and battery  137 B, water level sensors in the reservoir  110 , velocity sensors in penstock  120 , RPM (rotations per minute) speed sensors in the gear pump  131 , speed sensors in generator  138 , and water level sensors in stream  160 . Such sensors can electronically communicate with a computing device  139  having a processor, memory, and stored algorithms. The computing device  139  can emit control commands to the gear pump  131  to operate in passive (turbine), forward (suction), or reverse (pump) modes. The computing device  139  can be located with the gear pump  131 , or remote from the gear pump with appropriate communication devices in place. Based on feedback, such as low electricity in the battery, the gear pump  131  can operate in suction mode to fill the penstock  120 , and can then switch to turbine mode to charge the battery. Or, if a water level sensor in reservoir  110  indicates low water level, the gear pump  131  can operate in pump mode to move water from stream  160  to the reservoir  110 . 
     The gear pump unit  130  can be constructed as a component of the hydropower generation system  10  as described in  FIG. 1A . In addition, the gear pump unit  130  can supplement an existing hydropower generation plant by being a modular installation. In supplementing the existing hydropower generation plant, the gear pump  131  can simply replace the existing turbine to enhance the efficiency of the existing system. Alternatively, the gear pump unit  130  can be simultaneously used with the existing turbine and pump, as by being laid over the existing infrastructure. 
       FIG. 1B  illustrates another benefit of the modular design, which enables easy servicing and maintenance. A platform  170  is installed at or near the water level of river  160 . The gear pump unit  130  and control module  150  are stationed on the platform  170 . The gear pump  131  is serviceable and the control module  150  is easily updated. Being externally mounted to the dam  100 , it is not necessary to enter in to the dam  100  to service the penstock  120  or gear pump unit  130 . The light weight of the hollow rotors further facilitates the modular design. 
       FIG. 4  shows another embodiment of the present invention. A gear pump unit  230  may be placed in a small stream to generate electricity. The gear pump unit  230  may be a low head hydroelectric power generator. The gear pump unit  230  may receive water from a water source  200  through an inlet  232 . The water source  200  may be a canal or fast flowing river or stream. The gear pump unit  230  comprises a gear pump  231  and a generator  238 . The gear pump  231  and the generator  238  may be connected to each other through a shaft  236  or by a pulley or other mechanical coupling. The gear pump unit  230  may be constructed similar to the gear pump unit  130  as described using  FIG. 2 , with additional modifications to accommodate the difference in fluid velocity in the low head application, such as underwater placement of penstock  220 A leading to inlet  232 , and inclusion of tailrace penstock  220 D at outlet  235 . The gear pump unit  230  may alternatively include another fluid diversion mechanism than penstock, such as a tray like structure. 
     The gear pump unit  230  can be completely submerged under the water level of a flowing water source, or may be partially submerged. If fluid flow is not sufficient to turn the turbine, power can be used to pump up the water source by operating in pump mode and filling a reservoir structure. Thus, in the low head application it is particularly advantageous to implement a combined generator/motor. However, when a reservoir is not necessary, and fluid flow is sufficient, gear pump unit  230  can be used without a costly structural base making it cost effective and portable. 
     In the preceding specification, various preferred embodiments 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 embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense. 
     Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure. 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.