Patent Publication Number: US-6659731-B1

Title: Pressure exchanger

Description:
BACKGROUND 
     The invention relates to a pressure exchanger for transferring pressure energy from a fluid of one fluid system to a fluid of a second fluid system, comprising a liner and two end covers with an inlet and an outlet passage, respectively, for each fluid, and a cylindrical rotor which is provided in the liner and which is arranged for rotation about its longitudinal axis, and which has a number of through-going channels with an opening at each end arranged symmetrically about the longitudinal axis. The rotor&#39;s channels are arranged for connection with the end covers&#39; inlet and outlet passages in such a manner that during the rotor&#39;s rotation they alternately conduct fluid at high pressure and fluid at low pressure of the respective systems. 
     In NO 151341 and 168548 amongst others there is disclosed a pressure exchanger of the above-mentioned type for transferring pressure energy from one fluid flow to another. The pressure exchanger comprises a housing with an inlet and an outlet port for each fluid flow and a rotor which is arranged for rotation about its longitudinal axis in the housing. The rotor has at least one through-going channel, which extends from one end of the rotor to the other end, considered in the axial direction, and alternatively connects the inlet port and the outlet port for one fluid with the outlet port and the inlet port, respectively, for the second fluid and vice versa during the rotor&#39;s rotation. 
     The rotor is mounted between end covers and in a housing which is subject to full compression stress. At high pressures elastic deformations occur which have a profound effect on internal clearances and fits, a situation which can be partly compensated by means of pressure balancing of the end covers, as described in NO 180599, and by substantial overdimensioning of the rotor&#39;s housing. 
     In order to achieve a satisfactory degree of reliability in operation when using fluids with low viscosity, e.g., water, it has proved to be necessary to employ ceramics. This is a brittle material with considerably less tensile strength than metals, and at high pressure there is a great risk of fracture if the material should be subjected to impact or shock. 
     Moreover, pressure exchangers of the above-mentioned type are encumbered with practical drawbacks during maintenance, since pipe couplings have to be opened in order to gain access to internal components. In order to prevent strains in the pipe couplings leading to elastic deformations of critical components, an extra arrangement is required for assembly. 
     The object of the invention is to provide a pressure exchanger which is not encumbered with the above disadvantages. 
     The distinctive properties of this pressure exchanger according to the invention are presented in the claims. 
    
    
     The invention will now be described in more detail with reference to the drawings which schematically illustrate one example of a pressure exchanger according to the invention. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an embodiment of a pressure exchanger according to the invention. 
     FIG. 2 is a perspective view of the internal components of the pressure exchanger illustrated in FIG. 1, some of the components being shown broken away. 
     FIG. 3 is an exploded perspective view, partially broken away, of components of the pressure exchanger, where the various components have been separated from one another. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     As illustrated in FIG. 1 the pressure exchanger comprises a pressure housing  1  with a locking or top cover  8  and an inlet  7  for high pressure fluid and an outlet  5  for high pressure fluid, together with a window  6  for measuring the rotational speed. The maintenance of the pressure exchanger is substantially simplified due to the fact that the static components have been separated from the internal components which constitute the pressure exchanger&#39;s active unit. Furthermore, mounting has been simplified due to the fact that a base  2  with bolt holes  9  for attachment and an inlet  3  for low pressure fluid and an outlet  4  for low pressure fluid form a separate base construction which does not give rise to strain or deformations of the internal, active unit. 
     FIG. 2 illustrates the different components in the internal active unit of the pressure exchanger where the pressure exchange takes place, and which are installed inside the pressure housing  1  in order to protect the components against impact or shock. Since these components are placed inside a defined space which is pressurized via the flow media on the high pressure side, any substantial overdimensioning of the components is avoided. The rotor  11  is mounted in a liner  12  where the end surfaces abut directly against the end cover  13  for pressurization of fluid and the end cover  14  for depressurization of fluid. The liner  12  has at least one opening  15  for supply of lubricating fluid and measuring the rotational speed. The liner is slightly longer than the rotor and is secured between the end covers  13 ,  14  via a central bolt  10  which passes through the rotor  11  without substantially reducing the flow cross section, and which is securely screwed into the opposite end cover. In addition, the design results in the sides of the end covers which face the rotor&#39;s end surfaces being subject to a static pressure which is considerably less than the pressure on the outside, since high pressure on the rotor side is essentially restricted to the inlet and outlet ports for high pressure. This is advantageous, since the play between the rotor and the end covers decreases slightly during the pressurization due to the fact that the end covers are elastically deformed towards the rotor&#39;s end surfaces. The liner  12  is also subject to compression and the corresponding force on the end covers unites or establishes the position of all the static components, preventing a mutual rotation during operation. 
     FIG. 3 illustrates the various components which are shown in FIGS. 1 and 2, these being shown separated from one another. The internal structure is accessible via a central top cover  16  which is operated without the use of special tools. A static sealing ring  17  ensures a seal against the high working pressure on the inside. The pressure housing  1  may be opened manually by rotating the locking cover  8  which is equipped with a handle  20  so that a center bolt  21  is screwed out the top cover. This releases a multi-sectional locking ring  18  which is located in a corresponding groove in the pressure housing  1  and is secured via a stepped cut-out  19  in the locking cover  8 . The locking ring&#39;s individual segments are removed and the locking cover  8  is remounted, whereupon the top cover can be removed via the handle  20 . 
     FIG. 3 further provides a detailed illustration of the design of the end covers  13 ,  14  and the rotor  11  which permits the advantageous separation between inlet and outlet for the high pressure side and the low pressure side, respectively. A first fluid, e.g., a liquid B′, which will be depressurized in the known manner, is supplied to the rotor  11  via an inlet  7  with a direct connection to an inlet port  26  in the end cover  13 . The end cover is equipped with a sealing ring  28  to prevent mixing with corresponding liquid flow on the high pressure side. At the outlet from the rotor  11  a second fluid, e.g., a liquid B, is transferred via the outlet port of the same end cover  13  to an internal passage which flows into a coaxial, central course or channel  25  in the rotor  11 . From here the fluid flows out into a corresponding central, internal passage in the end cover  14  with an outlet  23  on the bottom. The end cover  14  is further provided with a sealing ring  22  which separates liquids with high and low pressure, respectively, while simultaneously causing the pressure exchanger to be exposed to a net force from the top. The low pressure port  31  has an inlet from the opening  24  in the bottom for liquid F which will be pressurized in the known manner. These inlet and outlet openings, at least one of which is designed with a pipe connection and sealing ring, are connected to corresponding openings in the pressure housing&#39;s base  2  by external pipe couplings  3 ,  4 . The force from the liquid pressure which acts on the pressure exchanger&#39;s top, is transferred to two lease pins  33  and  34  mounted on each side of the inlet and outlet openings  35 ,  36  for connection with the lower end cover  14 . The same end cover has a radial outlet  29  from the high pressure port  32  for the pressurized liquid F′ with direct outlet via the external pipe coupling  5 . The pressurized liquid F′ has access to the opening  15  for hydrostatic mounting of the rotor via the clearance between the pressure housing and the end cover  14  together with the liner  12 . In order to obtain an effective optical measurement of the rotational speed, the rotor  11  has a reflecting surface body  30 .