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Rotodynamic fluid machineRelated Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Rotary Motor And Rotary Nonexpansible Chamber PumpRotodynamic fluid machine description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070212238, Rotodynamic fluid machine. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to rotodynamic fluid machines and in particular to high power multistage units having a plurality of impeller stages. These are often used, for example, as high pressure pumps, particularly in the oil industry. [0002] Multistage rotodynamic fluid machines can offer an increased output pressure over a single stage unit. However the provision of additional impeller stages necessarily increases the overall size of the unit. [0003] Also, in known machines a coupling is required between the driving shaft extending from a motor and the driven shaft connected to one or more impeller stages, and this adds to the overall length of the machine. Furthermore couplings are a source of vibrational problems in rotating shafts and can greatly complicate a machine's rotor dynamics. [0004] Traditional mechanical bearings become worn with use and require lubrication in order to ensure correct operation. The use of oil to lubricate rotating parts causes a decrease in efficiency and the oil may leak contaminating other parts. [0005] Traditional high power multistage machines require high capacity thrust bearings and balancing discs to take up the resultant axial load created by the driving force of the impeller stages acting on the fluid. Seals are also required between the shafts and the housing to isolate the motor. Such parts also require lubrication and cause further losses in efficiency. [0006] According to one aspect of the present invention there is provided a rotodynamic fluid machine comprising a motor arranged for directly driving a shaft, a pressurised motor housing having end walls through which the shaft passes via dry seals to enclose the motor, means for maintaining the pressure within the motor housing different from the pressure outside the motor housing, a first impeller directly connected to one end of the motor driven shaft, arranged to move process fluid from an inlet to an outlet in a first direction relative to the shaft axis, a second impeller directly connected to the opposite end of the shaft, arranged to move process fluid from a second inlet to a second outlet in an opposite direction to the first direction relative to the shaft axis such that suction is created at both ends of the shaft, and a process fluid conduit connecting the first outlet to the second inlet. [0007] Preferably the pressure within the motor housing is different to the pressure of the process fluid in particular of the input process fluid, before it is pressurised or pumped up to discharge pressure. The pressure in the motor housing is preferably maintained high, i.e. higher than the process fluid or other adjacent fluids so as to ensure no leakage of fluids into the motor, for example if a seal fails. [0008] Another aspect of the invention provides a pump comprising a rotodynamic fluid machine of the first aspect. [0009] Preferably each of the first and second impellers are arranged to pump fluid generally towards the motor and the machine comprises a closed loop pressurised gas circulation system in fluid communication with a rotor part of the motor. [0010] The rotodynamic fluid machine may comprise a magnetic bearing supporting the shaft in a motor housing. [0011] According to a preferred embodiment, the shaft is integral with a rotor part of the motor. [0012] Advantageously the first impeller comprises a plurality of impeller stages and the second impeller comprises a plurality of impeller stages, and the first and second impellers may each comprise a diffuser unit. [0013] The diameter of the shaft may be larger in the region of the motor and smaller in the region of the or each impeller. [0014] The motor is preferably an electric motor. [0015] A rotodynamic fluid machine according to the present invention is particularly advantageous because mounting impellers directly onto the motor shaft eliminates the need for a coupling between a motor shaft and an impeller shaft. Thus the shaft length and the total length of the machine can be reduced. Axial thrust is also decreased and so thrust bearings can be reduced in size due to the back to back arrangement of the first and second impellers. [0016] The number of radial bearings may also be reduced since bearings need not be provided on either side of a coupling (i.e. one for each of the motor and impeller shafts). Without a coupling, there is no need for advanced in-field alignment procedures and the rotor dynamics of the machine are simplified with vibration levels reduced. Furthermore the use of balancing discs is not required. [0017] The use of magnetic bearings and dry gas seals advantageously allows for a rotodynamic machine which does not require the use of lubricating oil or hydraulic fluid. Thus the parasitic power losses caused by oil shear and drag are avoided. Furthermore the problem of oil leakage is eliminated and the overall machine is simplified. Maintenance is reduced as well as the number of auxiliary systems. [0018] The motor housing is sealed to enclose the motor to maintain the different pressures and this advantageously provides a clean and dry air internal environment for the motor. In combination with the back-to-back arrangement of this inventive machine, particularly when combined with magnetic bearings, this provides the possibility of a dry, oil-free machine. [0019] The back-to-back arrangement ensures that the axial forces are controlled without using large balance pistons which have hitherto been required in known motors. [0020] In known open motors, the process fluid is in and around the electric motor and this creates problems with motor contamination and bearing lubrication. [0021] For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the single FIG. 1, which is a representation of a rotodynamic fluid machine according the present invention. [0022] The figure shows a rotodynamic fluid machine 10 with an electric motor 12 enclosed in a pressurised housing 14 with end walls 16 and 18. The arrangement can be mounted vertically or horizontally. [0023] A shaft 20 is integrated with the rotor of the motor 12 and extends from each end of the motor through the end walls 16, 18. The diameter of shaft 20 decreases towards its free ends. [0024] A first set of impellers 22 is mounted on one end of shaft 20 on one side of the motor 12 and a second set of impellers 24 is mounted on the opposite end of shaft 20 on the other side of the motor 12. The shaft 20 and the impellers 22, 24 are rotatable about a common axis 26. Continue reading about Rotodynamic fluid machine... Full patent description for Rotodynamic fluid machine Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Rotodynamic fluid machine patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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