scholarly journals Investigations of unsteady pressure loading in a Francis turbine during variable-speed operation

2017 ◽  
Vol 113 ◽  
pp. 397-410 ◽  
Author(s):  
Chirag Trivedi ◽  
Einar Agnalt ◽  
Ole Gunnar Dahlhaug
Keyword(s):  
Francis Turbine ◽  
Variable Speed ◽  
Pressure Loading ◽  
Unsteady Pressure

Transient Pressure Measurements on a High Head Model Francis Turbine During Emergency Shutdown, Total Load Rejection, and Runaway

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Chirag Trivedi ◽  
Michel J. Cervantes ◽  
B. K. Gandhi ◽  
Ole G. Dahlhaug
Keyword(s):  
High Amplitude ◽  
Francis Turbine ◽  
Scale Model ◽  
Head Model ◽  
Pressure Loading ◽  
Operating Life ◽  
Total Load ◽  
Unsteady Pressure ◽  
Emergency Shutdown ◽  
Turbine Runner

The penetration of intermittent wind and solar power to the grid network above manageable limits disrupts electrical power grids. Consequently, hydraulic turbines synchronized to the grid experience total load rejection and are forced to shut down immediately. The turbine runner accelerates to runaway speeds in a few seconds, inducing high-amplitude, unsteady pressure loading on the blades. This sometimes results in a failure of the turbine components. Moreover, the unsteady pressure loading significantly affects the operating life of the turbine runner. Transient measurements were carried out on a scale model of a Francis turbine prototype (specific speed = 0.27) during an emergency shutdown with a transition into total load rejection. A detailed analysis of variables such as the head, discharge, pressure at different locations including the runner blades, shaft torque, and the guide vane angular movements are performed. The maximum amplitudes of the unsteady pressure fluctuations in the turbine were observed under a runaway condition. The amplitudes were 2.1 and 2.6 times that of the pressure loading at the best efficiency point in the vaneless space and runner, respectively. Such high-amplitude, unsteady pressure pulsations can affect the operating life of the turbine.

Experimental Investigation of a High Head Francis Turbine During Spin-No-Load Operation

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Chirag Trivedi ◽  
Michel J. Cervantes ◽  
Ole G. Dahlhaug ◽  
B. K. Gandhi
Keyword(s):  
Transmission Lines ◽  
Swirling Flow ◽  
Pressure Sensors ◽  
Hydraulic Turbine ◽  
High Amplitude ◽  
Francis Turbine ◽  
Pressure Loading ◽  
Transient Pressure ◽  
Unsteady Pressure ◽  
Absence Of Power

Water passes freely through a hydraulic turbine in the absence of power requirements or during maintenance of the transmission lines, spillways, or dam. Moreover, the turbine operates under no-load conditions prior to generator synchronization during startup and after the generator disconnection from the grid load for shutdown. High-velocity swirling flow during spin-no-load (SNL) induces unsteady pressure pulsations in the turbine, and these pulsations cause fatigue in the blades. To investigate the amplitude of unsteady pressure loading, transient pressure measurements were carried out in a model Francis turbine during SNL. A total of six pressure sensors were mounted inside the turbine, i.e., one in the vaneless space, three on the blade surfaces, and two in the draft tube, and three discharge conditions were investigated over the operating range of the turbine. Analysis of the unsteady pressure data showed that the runner blades experience high-amplitude pressure loading during SNL. The amplitudes at all sensor locations were high compared with those under the normal operating condition of the turbine, i.e., the best efficiency point (BEP), and increased as the discharge through the turbine increased.

Francis Turbine Modeling for Hydrounit on the Bases of the Doubly Fed Induction Machine

2015 ◽  
Vol 792 ◽  
pp. 203-208
Author(s):  
Rustam Kh. Diyorov ◽  
M.V. Glazyrin
Keyword(s):  
Mathematical Model ◽  
Numerical Modeling ◽  
Induction Machine ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Variable Speed ◽  
Physical Representation ◽  
Doubly Fed Induction Machine ◽  
Doubly Fed ◽  
The Mathematical Model

The mathematical model of Francis turbine, operating at variable speed hydrounit, has created. The results of numerical modeling are fully consistent with the physical representation of the behavior of the hydraulic turbine in dynamic modes.

scholarly journals Optimization of Francis Turbines for Variable Speed Operation Using Surrogate Modeling Approach

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Igor Iliev ◽  
Erik Os Tengs ◽  
Chirag Trivedi ◽  
Ole Gunnar Dahlhaug
Keyword(s):  
Design Space ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Optimization Strategy ◽  
Variable Speed ◽  
Hydraulic Design ◽  
Speed Performance ◽  
Quadratic Response ◽  
Specific Speed ◽  
The Hill

Abstract Previous studies suggested variable speed operation (VSO) of Francis turbines as a measure to improve the efficiency at off-design operating conditions. This is, however, strongly dependent on the hydraulic design and, for an existing turbine, improvements can be expected only with a proper redesign of the hydraulic surfaces. Therefore, an optimization algorithm is proposed and applied to the runner of a low specific speed Francis turbine, with an optimization strategy specifically constructed to improve the variable speed performance. In the constrained design space of the reference turbine, the geometry of the replacement runner is parametrically defined using 15 parameters. Box–Behnken method was used to populate the design space with 421 unique samples, needed to train fully quadratic response surface models of three characteristic efficiencies defined by the proposed objective function. Computational fluid dynamics (CFD) was used to calculate the responses for each sample. The parametric study showed that the anticipated variation of the shape of the hill chart, needed to improve the variable speed performance of the turbine, is limited within a narrow range. The presented method is general and can be applied to any specific speed in the Francis turbine range, for both synchronous speed and variable speed optimization tasks.

Influence of Clocking and Vane/Blade Spacing on the Unsteady Surface Pressure Loading for a Modern Stage and One-Half Transonic Turbine

2003 ◽  
Author(s):  
C. W. Haldeman ◽  
M. L. Krumanaker ◽  
M. G. Dunn
Keyword(s):  
Fundamental Frequency ◽  
Surface Pressure ◽  
Pressure Measurements ◽  
Pressure Loading ◽  
Unsteady Pressure ◽  
Spacing Effects ◽  
Unsteady Surface Pressure ◽  
Transonic Turbine ◽  
Vane Clocking ◽  
Experimental Effort

This paper describes pressure measurements obtained for a modern one and one-half stage turbine. As part of the experimental effort, the position of the HPT vane was clocked relative to the downstream LPT vane to determine the influence of vane clocking on both the steady and unsteady pressure loadings on the LPT vane and the HPT blade. In addition, the axial location of the HPT vane relative to the HPT blade was changed to investigate the combined influence of vane/blade spacing and clocking on the unsteady pressure loading. Time-averaged and time-accurate surface-pressure results are presented for several spanwise locations on the vanes and blade. Results were obtained at four different HPT vane-clocking positions and at two different vane/blade axial spacings for three (of the four) clocking positions. For time-averaged results, the effect of clocking is small on the HPT blade and vane. The influence of clocking on the transition ducts and the LPT vane is slightly greater (on the order of ±1%). Reduced HPT vane/blade spacing has a larger effect than clocking on the HPT vanes and blades (±3%) depending upon the particular surface. Examining the data at blade passing and the first fundamental frequency, the effect of spacing does not produce a dramatic influence on the relative changes that occur between clocking positions. The results demonstrate that clocking and spacing effects on the surface pressure loading are very complex and may introduce problems if the results of measurements or analysis made at one span or location in the machine are extrapolated to other sections.

scholarly journals Pressure Pulsation in a High Head Francis Turbine Operating at Variable Speed

2018 ◽  
Vol 1042 ◽  
pp. 012005
Author(s):  
D. B. Sannes ◽  
I. Iliev ◽  
E. Agnalt ◽  
O. G. Dahlhaug
Keyword(s):  
Pressure Pulsation ◽  
Francis Turbine ◽  
Variable Speed ◽  
High Head

Investigation of Turbine Shroud Distortions on the Aerodynamics of a One and One-Half Stage High-Pressure Turbine

2009 ◽  
Author(s):  
Eric A. Crosh ◽  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
D. Graham Holmes ◽  
Brian E. Mitchell
Keyword(s):  
High Pressure ◽  
Surface Pressure ◽  
Turbo Code ◽  
Traditional Approach ◽  
Single Frequency ◽  
Pressure Measurements ◽  
Pressure Loading ◽  
High Pressure Turbine ◽  
Unsteady Pressure ◽  
Blade Row

As part of a proactive effort to investigate the ability of computational fluid dynamic (CFD) tools to predict time-accurate surface-pressure histories, a combined experimental/computational investigation was performed examining the effect of rotor shroud (casing) out-of-roundness on the unsteady pressure loading for the blade row of a full-stage turbine. The casing out-of-roundness was idealized by designing a casing ring with a sinusoidal variation. This casing ring was used to replace a flat casing for an existing turbine and direct comparisons were made between the time-accurate pressure measurements and predictions obtained using the flat and “wavy” casings. For both casing configurations, predictions of the unsteady pressure loading for many locations on the blade and vane were obtained using Numeca’s FINE/Turbo code and the General Electric TACOMA code. This paper will concentrate on the results obtained for the “wavy” casing, but the results for the flat casing are presented as a baseline case. The time-accurate surface-pressure measurements were acquired for the vane and blade of a modern, 3-D, stage and 1/2 high-pressure turbine operating at the design corrected speed and stage pressure ratio. The research program utilized an un-cooled turbine stage for which all three airfoil rows are heavily instrumented at multiple spans to develop a full dataset. The vane-blade-vane count for this machine is 38-72-38. The number of waves in the distorted shroud “wavy wall” is approximately 1.5-times the number of vanes. The resulting changes in aerodynamic surface-pressure measurements were measurable at all blade span wise locations. Variations in time-average surface pressure of up to 5% of the flat casing values were observed. In addition, the frequency content of the time-resolved blade data for the “wavy” casing changed substantially from that measured using the flat casing, with changes in both amplitudes and frequencies. Imposing the casing irregularity changed the fundamental physics of the problem from a single frequency and its harmonics to a multi-frequency problem with mixed harmonics. The unsteady effects of this type of problem can be addressed using the harmonic method within Numeca’s FINE/Turbo code, which is designed to handle multiple blade passing frequencies and harmonics for one blade row. A more traditional approach is included in the paper by employing the TACOMA code in a linearized mode that produces results for a single frequency. These results show that casing irregularity can have a significant influence on the blade surface-pressure characteristics. Further, it is demonstrated that the FINE/Turbo code experienced difficulty predicting the unsteady pressure signal attributed to the “wavy” casing configuration, while at the same time capturing the unsteady signal attributed to the vane passing due to limitations in the current methodology.

Investigation of Turbine Shroud Distortions on the Aerodynamics of a One and One-Half Stage High-Pressure Turbine

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Eric A. Crosh ◽  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
D. Graham Holmes ◽  
Brian E. Mitchell
Keyword(s):  
High Pressure ◽  
Surface Pressure ◽  
Turbo Code ◽  
Single Frequency ◽  
Pressure Measurements ◽  
Pressure Loading ◽  
High Pressure Turbine ◽  
Data Set ◽  
Unsteady Pressure ◽  
Blade Row

As part of a proactive effort to investigate the ability of computational fluid dynamics tools to predict time-accurate surface-pressure histories, a combined experimental/computational investigation was performed, examining the effect of rotor shroud (casing) out-of-roundness on the unsteady pressure loading for the blade row of a full-stage turbine. The casing out-of-roundness was idealized by designing a casing ring with a sinusoidal variation. This casing ring was used to replace a flat casing for an existing turbine, and direct comparisons were made between the time-accurate pressure measurements and predictions obtained using the flat and “wavy” casings. For both casing configurations, predictions of the unsteady pressure loading for many locations on the blade and vane were obtained using Numeca’s FINE/TURBO code and General Electric’s turbine and compressor analysis (TACOMA) code. This paper will concentrate on the results obtained for the wavy casing, but the results for the flat casing are presented as a baseline case. The time-accurate surface-pressure measurements were acquired for the vane and blade of a modern, 3D, 1 and 1/2 stage high-pressure turbine operating at the design corrected speed and stage pressure ratio. The research program utilized an uncooled turbine stage for which all three airfoil rows are heavily instrumented at multiple spans to develop a full data set. The vane-blade-vane count for this machine is 38-72-38. The number of waves in the distorted shroud “wavy wall” is approximately 1.5 times the number of vanes. The resulting changes in the aerodynamic surface-pressure measurements were measurable at all blade spanwise locations. Variations in the time-averaged surface pressure of up to 5% of the flat casing values were observed. In addition, the frequency content of the time-resolved blade data for the wavy casing changed substantially from that measured using the flat casing, with changes in both amplitudes and frequencies. Imposing the casing irregularity changed the fundamental physics of the problem from a single frequency and its harmonics to a multifrequency problem with mixed harmonics. The unsteady effects of this type of problem can be addressed using the harmonic method within Numeca’s FINE/TURBO code, which is designed to handle multiple blade passing frequencies and harmonics for one blade row. A more traditional approach is included in this paper by employing the TACOMA code in a linearized mode that produces results for a single frequency. These results show that casing irregularity can have a significant influence on the blade surface-pressure characteristics. Further, it is demonstrated that the FINE/TURBO code experienced difficulty in predicting the unsteady pressure signal attributed to the wavy casing configuration, while at the same time, in capturing the unsteady signal attributed to the vane passing due to limitations in the current methodology.

scholarly journals Experimental study of a Francis turbine under variable-speed and discharge conditions

2018 ◽  
Vol 119 ◽  
pp. 447-458 ◽  
Author(s):  
Chirag Trivedi ◽  
Einar Agnalt ◽  
Ole Gunnar Dahlhaug
Keyword(s):  
Experimental Study ◽  
Francis Turbine ◽  
Variable Speed

Influence of Clocking and Vane/Blade Spacing on the Unsteady Surface Pressure Loading for a Modern Stage and One-Half Transonic Turbine

2003 ◽  
Vol 125 (4) ◽  
pp. 743-753 ◽  
Author(s):  
C. W. Haldeman ◽  
M. L. Krumanaker ◽  
M. G. Dunn
Keyword(s):  
Surface Pressure ◽  
Pressure Loading ◽  
High Pressure Turbine ◽  
Unsteady Pressure ◽  
Low Pressure Turbine ◽  
Spacing Effects ◽  
Unsteady Surface Pressure ◽  
Transonic Turbine ◽  
Vane Clocking ◽  
Experimental Effort

This paper describes pressure measurements obtained for a modern one and one-half stage turbine. As part of the experimental effort, the position of the high-pressure turbine (HPT) vane was clocked relative to the downstream low-pressure turbine (LPT) vane to determine the influence of vane clocking on both the steady and unsteady pressure loadings on the LPT vane and the HPT blade. In addition, the axial location of the HPT vane relative to the HPT blade was changed to investigate the combined influence of vane/blade spacing and clocking on the unsteady pressure loading. Time-averaged and time-accurate surface-pressure results are presented for several spanwise locations on the vanes and blade. Results were obtained at four different HPT vane-clocking positions and at two different vane/blade axial spacings for three (of the four) clocking positions. For time-averaged results, the effect of clocking is small on the HPT blade and vane. The influence of clocking on the transition ducts and the LPT vane is slightly greater (on the order of ±1%). Reduced HPT vane/blade spacing has a larger effect than clocking on the HPT vanes and blades ±3% depending upon the particular surface. Examining the data at blade passing and the first fundamental frequency, the effect of spacing does not produce a dramatic influence on the relative changes that occur between clocking positions. The results demonstrate that clocking and spacing effects on the surface pressure loading are very complex and may introduce problems if the results of measurements or analysis made at one span or location in the machine are extrapolated to other sections.

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