Wet Gas Impeller Test Facility

Abstract

The development of wet gas compressors will enable increased oil and gas production rates and enhanced profitable operation by subsea well-stream boosting. A more fundamental knowledge of the impact of liquid is essential with regard to the understanding of thermodynamic and fluid dynamic compressor behavior. An open-loop impeller test facility was designed to investigate the wet gas performance, aerodynamic stability, and operation range. The facility was made adaptable for different impeller and diffuser geometries. In this paper, the wet gas test facility and experimental work concerning the impact of wet gas on a representative full-scale industrial impeller are presented. The centrifugal compressor performance was examined at high gas volume fractions and atmospheric inlet conditions. Air and water were used as experimental fluids. Dry and wet gas performance was experimentally verified and analyzed. The results were in accordance with previous test data and indicated a stringent influence of the liquid phase. Air/water tests at atmospheric conditions were capable of reproducing the general performance trend of hydrocarbon wet gas compressor tests at high pressure.

Modelling and Nonlinear Control of a Wet Gas Centrifugal Compressor

“…According to [19], liquid will accumulate in the diffuser, resulting in an annular flow pattern and a reduced diffuser cross-sectional where fluid velocity is converted to static pressure. This observation was confirmed in experiments in [5], where an annular flow pattern was observed in the compressor, indicating separation of the flow due to the strong centrifugal forces created by the rotation of the impeller. To incorporate this wet gas effect in the model, the modelling approach of [4] is followed by dividing physical effects between different system components.…”

“…An alternative expression for the plenum gas mass fraction is obtained by substituting (5) and 6into 4giving…”

“…To complete the dynamic model, we need an algebraic expression for the throttle outlet flow. The fluid leaving the plenum is assumed to instantaneously mix homogeneously and density of this homogeneous mixture is given by [5]…”

“…Wet gas compression is a relatively new research area, but experiments by [5], [6] show that the compressor performance is significantly influenced by the presence of liquid. Typically, the losses increase with increasing mass flows and liquid content, resulting in reduced pressure rise for high mass flows and thereby reduced maximum capacity compared to dry gas compression.…”

“…Therefore, in this paper, we extend the dynamic dry gas compression model of Greitzer [4] -including the corresponding compressor characteristicwith an additional state. The compressor characteristic is curve fitted to experimental data from [5]. This allows the new dynamic model to capture wet gas dynamics while maintaining a continuous transition to dry gas compression.…”