Centrifugal compressor anti-surge control system modelling

<span>From the middle of XX century, natural gas is an important mineral, widely used in the energy sector. Transportation of natural gas is carried out via gas pipeline networks and compression stations. One of the key features which need to be implemented for any centrifugal gas compressor is a surge protection. This article describes the method and develops software application intended for simulation and study of surge protection system of a centrifugal compressor used in modern gas compression stations. Within the article research method, modelling environment’s block diagram, proposed algorithms and results are described. For surge cases control and prediction, Anti-surge control block implemented which based on practical experience and centrifugal compressor theory. To avoid complicated energy balancing differential equations the volumetric flow calculation algorithm proposed which is used in combination with Redlich-Kwong equation of state. Developed software’s adequacy test performed through modeling of one-stage gas compression scheme at rated speed with comparison of parameters with reference commercial software and verification of the anti-surge control system.</span>

Investigation of Suction Flow Control on Centrifugal Compressor with Vaned Diffuser

In this study, the effect of suction flow control on a centrifugal compressor at operation and stall flow rates was investigated using computational fluid dynamics (CFD). The compressor geometry was reconstructed from available open source profile data and the CFD analyses have been performed on this geometry using the appropriate mesh. To validate the CFD results, the compressor performance line was acquired and compared with the experimental results obtained at the design rotational speed. Then, suction flow control was employed at various suction slot positions with different suction flow rates to improve the performance of the compressor at operation and stall flow rates. As a result of the suction flow control trials, 0.85% increase in pressure ratio and 0.8% increase in adiabatic efficiency were achieved while the compressor was running at operation flow rate. The performance improvements corresponding to the stall flow rate of the compressor were 2.5% increase in pressure ratio and 2% increase in adiabatic efficiency.

Aerodynamic instabilities modeling under asymmetric boundary in a centrifugal compressor for turbocharger

The increasing demand for compression systems with high pressure ratio and wide safety margin has set new prerequisites for designers to meet the industrial needs without increasing the manufacturing costs excessively. In this work, the turbulent stability of the vaneless diffuser of the centrifugal compressor was analyzed. Unsteady Reynolds-averaged numerical simulations of the isolated diffuser and full annular diffuser with or without circumferential asymmetric boundary conditions downstream were performed. And a continuous adjoint approach was adopted, which is rarely applied in the stability analysis of compressor flow. Then, the origin of instability under different inflow and outflow conditions was sought with a sensitivity analysis. The prediction of the growth rate reveals that the flow near the shroud dominates the global stability of the diffuser. When connected with an impeller in the upstream direction, the most unstable region is localized at the backflow regions near the outlet. The wave number, however, is altered under the impact of the jet-wake flow. When connected to a circumferential asymmetric condition, the structural sensitivity of the vaneless diffuser with a radius ratio of 1.53 indicates that the interaction between the inlet reverse flow and outlet backflow is responsible for the occurrence of stall. The most unstable regions are localized at the region 90°–135° away from the volute tongue. The present work mainly contributes to the instabilities identification with novel sensitivity methods under asymmetric boundary conditions.

Design of compressor impeller under high Reynolds number conditions

Purpose A parametric method for designing the hub, casing and blades of the miniature centrifugal compressor impeller was developed. The relationship model of the size, aerodynamic and performance parameters of the centrifugal impeller was established. Based on the selected design parameters, the miniature centrifugal-type impeller was designed, and the work efficiency was calculated. Design/methodology/approach In this study, a micro-centrifugal compressor impeller with a diameter of less than 25 mm was designed. A parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established. Findings The results of this study showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions. Originality/value A parametric design method was developed, and the functional relationship between the geometric and gas fluidity parameters was established. Under the Reynolds number conditions, the flow characteristics of the gas in the compressor were analysed; the shear-stress transport turbulence equation was solved using the finite volume method. In addition, the effects of the Reynolds number on the velocity, pressure, mass flow and efficiency of the micro-scale centrifugal compressor were evaluated. The results showed that the performance parameters of the designed micro-centrifugal impeller satisfied the design requirements. The proposed method is useful as a reference for designing and analysing compressor impellers under high Reynolds number conditions.

Experimental and Numerical Analysis of the Impeller Backside Cavity in a Centrifugal Compressor for CAES

Relying on a closed test rig of a high-power intercooling centrifugal compressor for compressed air energy storage (CAES), this study measured the static pressure and static temperature at different radii on the static wall of the impeller backside cavity (IBC) under variable rotating speeds. Simultaneously, the coupled computations of all mainstream domains with IBC or not were used for comparative analysis of the aerodynamic performances of the compressor and the internal flow field in IBC. The results show that IBC has a significant impact on coupling characteristics including pressure ratio, efficiency, torque, shaft power, and axial thrust of the centrifugal compressor. The gradients of radial static pressure and static temperature in IBC both increase with the decrease of mainstream flow or the increase of rotating speed, whose distributions are different under variable rotating speeds due to the change of the aerodynamic parameters of mainstream.