Numerical investigation on screw rotor deformation and influence on volumetric efficiency of the twin-screw multiphase pump

Rotor profile generation and geometry characteristics play a dominant role in developing twin-screw multi-phase pumps. The aim of this work is to present mathematical procedures to calculate screw rotor profile generation, design rotor cutter tools, and rotor geometry characteristics with given stocks for twin-screw multi-phase pumps. Analyses of the profile generation of a screw rotor for a multi-phase pump are carried out. The resulting rotor profile with different stocks is developed on the basis of the calculation of the forming cutter tool profile. An iso-height contour plot is presented for describing the shape and size of the overlapped cavity of the rotors. By inspecting the iso-height contour plot, analysis of all the possible leakage flow through the inter-lobe clearance is performed. According to the iso-height contour plot, the blowhole provides the major leakage path for the basic chambers through the overlapped cavity. The minimum normal height of the overlapped cavity has a linear relationship with the stock. The larger stocks lead to greater leakage and reduce pump performance. The leakage flow through the overlapped cavity will be aggravated and the performance of the twin-screw multi-phase pump will decline with the increasing lead of the screw rotor.

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The Kvaerner Multiphase Pump System for Deepwater Applications

Part B: Offshore and Arctic Operations; Pipeline Technology; Production Technology; Tribology ◽

10.1115/etce2001-17103 ◽

2001 ◽

Author(s):

Ove F. Jahnsen ◽

John Yardley ◽

Geoff High ◽

Brede Thorkilsen

Keyword(s):

Development Program ◽

Gas Content ◽

Modular System ◽

Pump System ◽

Multiphase Pump ◽

Current Test ◽

System Solution ◽

Twin Screw ◽

The Individual ◽

Pump Inlet

Abstract This paper describes Kvaerner’s prototype subsea multiphase pump system and the DEMO 2000 development program (current test completion date 2nd Q2001). Reference is also made to service proven sub-systems, components and subsea expertise incorporated into the pump module and system design. Availability and reliability consideration together with novel plans for the future is presented. The Subsea Multiphase Pump and motor are packaged into a modular system solution that is readily adaptable to template and manifold configurations and maximises the use of existing qualified components and sub-systems. A guidewireless system is adopted and Kvaerner’s design ensures self-alignment upon installation at simple flowbase interfaces, making it ideal for deepwater applications. Due to the individual 40 tonne weight, and moonpool dimensions, of both flow base and pump module, light monohull vessels can be utilised to execute installation and retrieval. The pump unit is Bornemann twin-screw design, service proven and modified for subsea use up to 2000-meter water depth, driven by an oil-filled Loher electric motor that provides efficient power with corresponding low weight. Some main pump features are flexible operation covering all gas-liquid ratios together with tolerance for slug flow and some sand. Of particular importance, compared to centrifugal pump designs, the twin-screw volumetric arrangement is able to maintain the pressure boost specification independent of gas content at the pump inlet, and without an upstream mixing tank.

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