Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Performance evaluation of the operation of twin-screw pumps operating in serial arrangement
Submission Author:
Emilio Paladino , SC
Co-Authors:
Emilio Paladino, Rafael Franklin Lazaro de Cerqueira, Josiane Weise, Thales Carl Lavoratti
Presenter: Emilio Paladino
doi://10.26678/ABCM.COBEM2021.COB2021-0420
Abstract
Multiphase pumping from wellheads to processing facilities has been a challenge during last decades, especially in remote areas such as deep waters. Pumping the produced fluids, from sub-sea wellheads through long distances without prior phase separation, have enormous economic and technical advantages as making feasible the subsea-to-shore direct transportation vision. Twin-screw boosting technology has shown a versatile and reliable performance for a wide range of gas fractions inlet streams, representing, nowadays, approximately 90% of the total boosting technology that has been used in the field. However, the use of positive displacement pump in fields condition is restricted to constant displacement pumps (i.e., no reduction of fluids volume), due to the variability of the gas fraction in the produced streams. Eventual operation with zero gas fraction would destroy a variable displacement pump. On the other side, when operating with high inlet gas volume fractions and high compression relations, the constant displacement condition lead to a very inefficient operation, mainly due to uneven distribution of the power delivered to the stream, along the screw, as power is mostly transferred in last cavities, producing higher wear, uneven dilatation and eventual rotor/stator interference. Beyond the energy efficiency issues, this condition significantly shortens the pump lifespan, making unfeasible their application in deep-water environment du to the high cost of maintenance. An alternative for dealing with high differential pressures and highly variable gas volume fractions (0 to 95+%) is to divide the compression in two or more pumps, which displacements are controlled through the rotation velocity, according to the gas fraction at inlet of the pumping system. This serial arrangement divides the compression of the gas along the two pumps, resulting in a more efficient operation for both pumps. In this paper we present a systematic experimental study the performance of twin-screw pumps operating in two-phase conditions in a serial arrangement. The experimental set-up used provides detailed data of the operation, as pressure and temperature in all stages of the system, gas and liquid flow rates and rotation an torque of the pumps. First, the performance of a single pump is evaluated for different rotations, differential pressure and inlet gas volume fractions. Then, the operation of the pumping system, consisting of two identical twin-screw pumps in serial arrangement is assessed. The performance is evaluated through the volumetric and energetic efficiencies which can be independently assessed for each pump, operating in serial arrangement.
Keywords
Multiphase pump, Twin-screw pump, Serial arrangement
