Analysis of the Influence of Inlet Guide Vanes on the Performance of Shaft Tubular Pumps

To study the influence of inlet guide vanes (IGVs) on the pressure pulsation of a shaft tubular pump, this paper first conducts an experiment to study IGVs. Then, numerical calculations of the shaft tubular pump with and without IGVs are performed to analyze the hydraulic performance and pressure fluctuation characteristics. Finally, the reliability and accuracy of the data are verified by a model test. Numerical simulation results show that with additional IGVs, the pressure pulsation amplitude at the impeller inlet first decreases and then increases under small-flow and design conditions but gradually increases under large-flow conditions. When the IGVs are added to the impeller inlet of the shaft tubular pump, the hydraulic loss in front of the impeller inlet increases, resulting in a significant drop in the head and efficiency of the pump device when the flow rate is less than 1.12 Qd; when the flow rate is greater than 1.12Qd, the head and efficiency of the pump device do not change significantly. IGVs can improve the condition of impeller water inflow and reduce pressure fluctuation on the blade surface.

Numerical Investigation of Transient Flow Characteristics in a Centrifugal Compressor Stage with Variable Inlet Guide Vanes at Low Mass Flow Rates

This study numerically investigates the beneficial effects of positive pre-swirl on the aerodynamic performance and internal flow field in a centrifugal compressor stage with variable inlet guide vanes (VIGVs) at low mass flow rates. Four positions of VIGV are considered, including 0°, 30°, 45°, and 60° angle. The latter three positions of VIGV induce positive pre-swirl. Numerical results show that as positive pre-swirl increases, the aerodynamic performance curve of the stage moves in the low mass flow rate direction. In the three cases of positive pre-swirl, there was an improvement of approximately 9.95% of stall/surge margin greater than in conditions with no pre-swirl. The regulation of IGV can effectively improve the unstable flow of the compressor stage at low mass flow rates. A low frequency that has a great influence on the internal flow of the compressor stage is found, and the unstable flow caused by low frequency is analyzed by the combination of streamline distribution, spectrum analysis, vector, entropy increase, and modal decomposition method. Meanwhile, the modal decomposition method and flow field reconstruction techniques are used to investigate the coherent flow structures caused by low frequency under different guide vane openings.

Effects of number of inlet guide vanes on the aerodynamic performance of a centrifugal compressor

Variable inlet guide vanes (VIGVs) are widely used for flow throttling and also extending the operating range of centrifugal compressors. Although there are several studies on the effects of adding IGVs on the performance curve of the compressors, none of them have focused on the number of vanes. In the current study, high-fidelity three-dimensional numerical simulations are carried out to analyze the effects of adding VIGVs with different number of vanes on the aerodynamic performance of a single-stage centrifugal compressor. The selected compressor prototype is a high flowrate single-stage compressor equipped with a vaned diffuser, designed and fabricated by Siemens. Computational fluid dynamic simulations are performed for three different number of guide vanes at three IGV inclination angles of 0, −30 and +45 degrees. The numerical results are validated by comparing the pressure-rise curves with the available experimental data of the compressor data sheet, where a good agreement was achieved. Results show that at the fully-open condition, the number of vanes does not have considerable effect on the performance curve of the compressor. However, as the IGV inclination angle increases, the number of inlet vanes plays a considerable role in the compressor efficiency. For example, at IGV inclination angle of +45 degree, increasing the number of vanes from 7 to 11 can increase the compressor maximum efficiency up to 5 points. Numerical results showed that increasing the number of inlet guide vanes imposes a higher pressure drop in the inlet passage of the compressor while generating a more uniform velocity distribution at the suction surface of the impeller. Due to the existence of several counteracting effects, an optimum number of inlet guide vanes can be found.

Numerical Study of the Flow in the Flow Path of a Centrifugal Natural Gas Compressor at Different Positions of the Inlet Guide Vane

The paper focuses on the problem of a possible expansion of the range of operating modes of a centrifugal natural gas compressor due to the rotation of the inlet guide vanes at different rotor speeds. The geometry of the flow path of the investigated object, obtained by three-dimensional scanning, is presented. On its basis, a numerical model is built and the influence of various factors of the formulation of the computational problem on the results of modeling the gas flow in the flow path of the compressor is analyzed. The calculations were performed using the k--ε and SST turbulence models for various parameters of the computational grid and conditions for averaging the flow parameters between the computational domains. The results obtained were compared with the nameplate and operational data. Recommendations on the formulation of the modeling problem are proposed, the results of the calculations are described, and the characteristics of the centrifugal compressor are plotted at different angles of the inlet guide vanes in a wide range of rotor speeds. The possible range of expansion of the operating modes of the investigated compressor is described, which can be provided by varying the position of the inlet guide vane

EFFECTS OF INLET GUIDE VANES ON THE PERFORMANCE AND STABILITY OF AN AERONAUTICAL CENTRIFUGAL COMPRESSOR

A research centrifugal compressor stage designed and built by Safran Helicopter Engines is tested at 3 IGV (Inlet Guide Vanes) stagger angles. The methodology for calculating the performance is detailed, including the consideration of humidity in order to minimize errors related in particular to operating atmospheric conditions. The shift of the surge line towards lower mass flow rate as the IGV stagger angle increases highly depends on the rotation speed. The surge line shift is very small at low rotation speeds whereas it significantly increases at high rotation speeds. A first-order stability analysis of the impeller and diffuser sub-components shows that the diffuser (resp. impeller) is the first unstable component at low (resp. high) rotation speeds. This situation is unaltered by increasing the IGV stagger angle. At low rotation speeds below a given mass flow rate, rotating instabilities at the impeller inlet are detected at zero IGV stagger angle. Their occurrence is conditioned by the relative flow angle at the tip of the leading edge of the impeller. As the IGV stagger angle increases, the mass flow decreases to maintain a given inlet flow angle. Therefore, the onset of the rotating instabilities is delayed towards lower mass flow rates. At high rotation speeds, the absolute flow angle at the diffuser inlet near surge decreases as the IGV stagger angle increases. As a result, the flow is highly alternate over two adjacent channels of the radial diffuser beyond the surge line at IGV stagger angle of 0°.