Title of Invention

A JET PUMP

Abstract

A jet pump comprises a suction chamber, a central nozzle partly located outside the suction chamber, with its tip located inside the suction chamber, a mixing tube communicating with the tip of the nozzle; and a diffuser, the suction chamber being composed of at least one inlet ami a transition tube adjoining the inlet, said transition tube opening out into two branched tubes communicating with the mixing tube causing a non ax symmetric entrainment of secondary fluid into the mixing tube; raid nozzle being a convergent-straight exit type, the tip of which is flush with the ends of the branched pipes.

Full Text

This invention relates to a jet pump. A jet pump (also called as the ejector, eductor or injector) is a fluid displacement pump used in the fields of water transmission, deep well pumping, oil, dredging and chemical industry, to pump liquids, gases, a changeable substance (like steam) or solid - liquid mixtures. The jet pump basically has the following parts-jet nozzle, suction chamber, mixing tube and diffuser. There are about four types of jet pump designs available, each having some advantages and disadvantages when used for a particular application. The designs differ from each other mainly in the location and geometry of the suction chamber and the nozzle. For applications of the future like deep sea mining involving vertical hydraulic pumping of large solids from deep ocean floor, jet pumps have the basic features to provide the most reliable pumping solution. However the existing designs of jet pumps will not be adequate to satisfy all the duty requirements. Such applications require jet pump designs with very high reliability to work in deep sea at 5000 metre depths where accessibility for maintenance is almost impossible. The pumps must handle solids upto 75 mm diameter without plugging, maintain the required transport velocity within the pump to prevent settling of solids, facilitate provisions for incorporation of an adjustable nozzle to suit variations in duty conditions, provide for self draining arrangements for solids in case of power failures and have minimum wear in its parts. With the foregoing facts in mind we have invented a Branched Tubular Suction, Central Nozzle jet pump which can be used effectively for deep sea mining applications. The pump can also be used for other applications like clear water pumping and for fine solids pumping with many advantages over other existing designs. The Central nozzle central suction jet pumps are the most efficient among the existing designs of jet pumps. However the concentric design of these pumps requires a suction chamber of large diameter to maintain the minimum clearance required between the suction chamber and the nozzle to facilitate smooth flow of large solids. This large diameter causes a reduction in velocity of the suction fluid, whicfy may sometimes reach values lower than the settling velocity of solids resulting in clogging. If the required velocity is to be maintained, then large flow is required which results in very low Concentration conveyance and large increase in power consumption. Other disadvantages are difficulty in providing an adjustable nozzle arrangement and presence of nozzle external wear. The Central nozzle side suction jet pumps are liable to offer plugging problems at the suction passage in case of power failures as the suction line is perpendicular to the direction of the main discharge. Plugging causes further problems during starting. In some designs nozzle external wear is also present. The possibility of the velocity of the suction fluid going below the settling velocity of large solids in the suction chamber cannot be ruled out though it may not be to the extent as likely in the case of central suction jet pumps. Multi nozzle and ring jet pumps are efficient only in regions having high area ratios. Difficulty in providing an adaptive nozzle provision and difficulties in manufacture are the other disadvantages. The branched tubular suction central nozzle jet pump has been developed keeping the duty requirements of deep sea mining and the desirable features mentioned before as the main focus of research work. The design of the suction chamber is based on a new physical concept of non axisymmetric entrainment of secondary fluid into the mixing tube unlike the existing designs where the entrainment is axisymmetric. According to this invention the jet pump comprises a suction chamber; a central nozzle located outside the pump, with its tip located inside the pump; a mixing tube communicating with the tip of the nozzle; and a diffuser; the suction chamber being composed of a circular inlet, a transition piece adjoining the inlet having an elliptical or oval section, said transition piece [opening dm into two branched tubes communicating with the mixing tube; said ftozzle being a convergent-straight exit nozzle, the tip of which is flush with the ends of branched pipes. The jet pump proposed herein will now be described with reference to the accompanying drawings which illustrate by way of example and not by way of limitation one of the possible embodiments of this invention, wherein Fig. 1 illustrates the embodiment in front elevation Fig. 2 illustrates the embodiment in side elevation. Fig. 3 illustrates the nozzle in front view. Fig. 4 illustrates the nozzle in side view. Fig. 5 and 6 illustrate front and side views of a double suction inlet and Fig. 7 and 8 illustrate front and side views of a double suction inlet and adjustable nozzle. The jet pump proposed herein basically has a central nozzle N, a suction chamber S a mixing tube M and a diffuser D. The geometry of the suction chamber has a circular inlet I, a transition piece T that changes the section from circular to an oval section, followed by two branched tubes PI and P2. The tubes are branched to facilitate insertion of the central nozzle thereby avoiding its external contact with the suction fluid having solids in it. The branched tubes converge near the tip of the jet nozzle N (disposed outside the pump with its tip V located inside the pump) where the mixing tube M is attached vertically in the direction of the flow of the jet. The oval section is formed out of a rectangular section connected at the ends by two semi circular sections to obtain an oval shape. The area of this section will be approximately the same as the circular inlet. The two branches attached to this section are made out of tubes having the same radius as that of the semicircles in the oval section. In such a kind of design the entrainment of secondary fluid is non axisymmetric, which is a new concept when compared to other designs of jet pumps. The passages of the tubes PI and P2 are designed to provide sufficient clearance to entrain solids without clogging as well as maintain necessary transport velocity which becomes important when handling large solids. Large passages (three times the size of the largest particle encountered) are required for smooth flow of solids. However the area of the passsages should be minimum to ensure that the required velocity is maintained to transport solids, especially in the case of large solids. The twin branched circular section provides the neccesary clearance for smooth flow of solids with minimum area thereby main taining the required transport velocity. All sections of components in the suction chamber are shaped to reduce acceleration and deceleration losses throughout the flow from the pump's inlet point till the point of jet action by maintaining minimum variation in sectional area at any point in the flow. The changes in the direction of the flow path of the branched tubes are less than 25° at any point in the flow. This feature facilitates self drainage of solids in case of power failures and also reduces the pressure losses due to bends. The nozzle N is a convergent - straight exit type nozzle and is machined at the ends to be in flush with the profile of the suction chamber tubes to maintain smooth flow. As mentioned earlier, as the nozzle is kept out of the suction flow passage its external wear is absent. A feature for the adjustment of nozzle size can also be added to cater to the requirement of varied heads of the jet pump and discharges if necessary. The mixing chamber is a cylindrical tube of uniform cross section. The mixing chamber leads to the diffuser which has a semicone angle of 2.5-3.5°. The mixing tube and the difiuser of the pump have been designed similar to that used in the case of any conventional jet pump. Typical pumps of this type have been designed, manufactured and tested in the laboratory. A small size pump has been developed on and tested for a maximum solids pumping capacity of 10 tonnes per hour. Another large size pump has been developed and tested for a maximum solids pumping capacity of 120 tonnes per hour The pump has been tested for solids for various concentrations. The performance of the jet pump has been comparable to the central nozzle central suction jet pump (Most efficient jet pump). No clogging problems have been encountered and the deterioration of performance due to the presence of solids has been marginal. The branched tubular suction central nozzle jet pump combines all the advantages of existing design of jet pumps and the same design can be used universally for liquids, fine solids and large solids pumping. The disadvantages faced by the existing designs are not present. The novel features of this pump and a description of the advantages are presented below. The branched tubular section of the suction chamber causes a non axi symmetric entry of suction fluid. Further, the branched tubular section of the suction chamber has lA of the area when compared to the area required for the suction chambers of central nozzle central suction jet pumps for handling large solids. This reduction in sectional area enables the velocity to be maintained to the required transport velocity at every point in the flow path. Such a branched tube suction geometry is the first of its kind in jet pump designs. Variations in sectional area in the flow path of the suction are minimum inspite of the changes in the profile along the flow path. This feature of the suction chamber is quite different from the suction chambers of other jet pumps especially the central nozzle central suction and side suction jet pumps, where the variations in sectional area are quite large in the direction of flow. Reduction in acceleration and deceleration losses is the advantage of this feature. The nozzle is present externally and not in the path of the suction media as in the case of Central nozzle central suction pumps. Further the nozzle ends are in flush with the branched suction tubes at the interface. Nozzle external wear due to impact of solids is therefore absent, and the life of nozzle enhanced. The pump facilitates self drainage of solids as the changes in direction in the flow path are less than 25°. In the case of side suction jet pumps the directional changes are of the order of 90° which may cause plugging in case of power failures. The nozzle can be converted to an adjustable nozzle to provide varied fluid power when sudden high concentration of solids are encountered during pumping (in mining operations). The performance of the pump can be compared with the performance of the most efficient pumps viz., the central nozzle central suction jet pumps in a wide range of area ratios The pump can be easily manufactured by bending pipes to the required shape and machining the nozzle. These operations can be carried out in any small workshop. Further the costs involved in manufacturing will also be lesser than the central nozzle central suction jet pump which is the lowest among the existing designs. Thus, it can be concluded that the branched tubular suction jet pump developed has got all the advantageous1 features of existing designs overcoming their disadvantages. The pump proposed herein can be made using different materials like Stainless steel, HDPE, Polyurethanes etc. The existing design can be effectively used as a "double suction jet pump" as shown in figures 5 and 6. In systems where a single pump has to draw fluid from two locations, the jet pump developed can be modified by removing the branched regions at the bottom and directly conftectihg the suction lines as a double suction jet pump. In case of dredging/mining applications where large areas are to be traversed and two dredge heads are involved such a design can be used. Such a pump will be more efficient than the pump mentioned as losses at the suction inlet during branching will be absent. Different nozzle profiles like elliptical nozzle square nozzle etc. can be used in the branched tube suction concept. Such a design may improve the capture area and cause delivery of higher concentration of solids Similar Jet Pumps with an additional provision for varying nozzle size can be made as shown in the figures 7 and 8. The design provides for the space required for incorporating such a provision. Such a feature will enable adaptive operation of the jet pump for providing varied fluid power required when sudden variations in concentration? Occur during pumping (as encountered in deep sea mining).

Documents:

1087-mas-2000 abstract granted.pdf

1087-mas-2000 claims granted.pdf

1087-mas-2000 description (complete) granted.pdf

1087-mas-2000 drawings granted.pdf

1087-mas-2000-abstract.pdf

1087-mas-2000-claims.pdf

1087-mas-2000-correspondence others.pdf

1087-mas-2000-correspondence po.pdf

1087-mas-2000-description complete.pdf

1087-mas-2000-drawings.pdf

1087-mas-2000-form 1.pdf

1087-mas-2000-form 19.pdf

1087-mas-2000-form 26.pdf