scholarly journals Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Jian Liu ◽  
Wei-Yang Qiao ◽  
Wen-Hua Duan
Keyword(s):  
Pressure Fluctuation ◽  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Blade Surface ◽  
Variable Geometry Turbine ◽  
Mach Numbers ◽  
Fluctuation Energy

To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages

2002 ◽  
Author(s):  
Bjo¨rn Laumert ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Three Dimensional ◽  
Relative Strength ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Pressure Perturbation ◽  
Blade Surface ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Exit Mach Number

This paper presents a study of the blade pressure perturbation levels and the resulting rotor blade force in three high-pressure transonic turbine stages, based on three-dimensional unsteady viscous computations. The aim is to identify stage characteristics that correlate with the perturbation strength and degree of force realization on the rotor blades. To address the effects of off-design operation, the computations were performed at high subsonic, design and higher vane exit Mach number operating conditions. Furthermore spanwise variations in pressure levels and blade force are addressed. In our investigation the RMS of the pressure perturbations integrated in both time and along the blade surface is utilized as a global measure of the blade pressure perturbation strength on the rotor blade surface. The relative strength of the different pressure perturbation events on the rotor blade surface is also investigated. To obtain information about the relative strength of events related to the blade passing frequency the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force are addressed.

An Investigation of the Flow Structures and Flow Control in a Variable Geometry Turbine

2011 ◽  
Author(s):  
Lei Huang ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Lifeng Hu
Keyword(s):  
Rotor Blade ◽  
Recirculation Zone ◽  
Operating Conditions ◽  
Flow Structures ◽  
Variable Geometry ◽  
Cfd Simulations ◽  
Pressure Surface ◽  
Passage Vortex ◽  
Nozzle Position ◽  
Variable Geometry Turbine

The flow structures of a variable geometry turbine at operating conditions of different nozzle open positions were investigated through CFD simulations. The flow field structures of the VGT at highly off-design operating conditions were presented. The evolution of the secondary flow vortex structures was studied. CFD results show that at open nozzle position, there is a recirculation zone on the nozzle vane pressure surface, and the rotor blade is under a considerable negative incidence, which leads to a passage vortex on the pressure surface of the blade. At closed nozzle position, the flow into the rotor has positive incidence, which leads to a recirculation zone on the suction surface. At highly off-design conditions, the passage vortex caused by the misalignment of the rotor inlet flow angle and the rotor blade angle accounts the most important losses of turbine flow. The turbine flow was controlled by adjusting the blade inlet angle distribution along the leading edge while keeping the radial-fiber rotor construction. CFD simulations show that the turbine efficiencies are improved in most operating points at both open and closed nozzle conditions.

scholarly journals The Design and Evaluation of a 14 Stage, 16:1 Pressure Ratio Compressor for an Industrial Gas Turbine

1996 ◽  
Author(s):  
Mohammad R. Saadatmand
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Suction Surface ◽  
Design Intent ◽  
Flow Through ◽  
Industrial Gas Turbine

The aerodynamic design process leading to the production configuration of a 14 stage, 16:1 pressure ratio compressor for the Taurus 70 gas turbine is described. The performance of the compressor is measured and compared to the design intent. Overall compressor performance at the design condition was found to be close to design intent. Flow profiles measured by vane mounted instrumentation are presented and discussed. The flow through the first rotor blade has been modeled at different operating conditions using the Dawes (1987) three-dimensional viscous code and the results are compared to the experimental data. The CFD prediction agreed well with the experimental data across the blade span, including the pile up of the boundary layer on the corner of the hub and the suction surface. The rotor blade was also analyzed with different grid refinement and the results were compared with the test data.

Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

2005 ◽  
Vol 128 (2) ◽  
pp. 359-369 ◽  
Author(s):  
Rafael Ballesteros-Tajadura ◽  
Sandra Velarde-Suárez ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Fluid Dynamics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Operating Conditions ◽  
Experimental Results ◽  
Time Dependent ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Good Agreement

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

Mean-Line Modelling of a Variable Geometry Turbocharger (VGT) and Prediction of the Engine-Turbocharger Coupled Performance

2017 ◽  
Author(s):  
Anand Mammen Thomas ◽  
Jensen Samuel ◽  
A. Ramesh
Keyword(s):  
Pressure Ratio ◽  
Operating Conditions ◽  
Relaxation Techniques ◽  
Variable Geometry ◽  
Test Bed ◽  
Variable Geometry Turbocharger ◽  
Initial Assumption ◽  
Blockage Factor ◽  
Pressure Boundary Condition ◽  
Variable Geometry Turbine

Mean-line modelling approach which has generally been applied to fixed geometry turbocharger turbines has been extended to predict the performance of the variable geometry turbine for different inlet blade angles. The model uses an initial assumption of turbine inlet pressure which was iteratively corrected based on outlet pressure boundary condition. The model was implemented in MATLAB and stable and convergent solutions were obtained using relaxation techniques for different operating conditions. Experiments were done on a state of the art transient diesel engine test bed using the same VGT turbine in the turbocharger at different engine torques and speeds. Using experimental data the model was calibrated for the aerodynamic blockage in the fixed nozzle and rotor blade passages. Results revealed that turbine overall pressure ratio can be predicted accurately if a blockage factor varying with nozzle blade orientation is used in the model.

Pressure and Flow Rate Fluctuations in Single- and Two-Blade Pumps

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Andreas Pesch ◽  
Steffen Melzer ◽  
Stephan Schepeler ◽  
Tobias Kalkkuhl ◽  
Romuald Skoda
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Electromagnetic Flowmeter ◽  
Flow Region ◽  
Mean Values ◽  
Wall Pressure Fluctuations ◽  
Simulation Results ◽  
Blade Pump

Abstract A comparative study on the highly unsteady flow field in single- and two-blade pumps is performed. Stationary pump characteristics, as well as pressure and flow rate fluctuations, are presented. Wall pressure fluctuations were measured in the suction and pressure pipe as well as at several locations within the volute casing by piezoresistive transducers. Flow rate fluctuations were evaluated by a recently presented measurement system based on an electromagnetic flowmeter (Melzer et al. 2020, “A System for Time-Fluctuating Flow Rate Measurements in a Single-Blade Pump Circuit,” Flow Meas. Instrum., 71, p. 101675). Measurements were accompanied by three-dimensional (3D) flow simulations with the open-source cfd software foam-extend. A thorough grid study and validation of the simulation were performed. By a complementary analysis of measurement and simulation results, distinctive differences between both pump types were observed, e.g., flow rate and pressure fluctuation magnitudes are significantly higher in the single-blade pump. In relation to the respective mean values, flow rate fluctuation magnitudes are one order lower than pressure fluctuation magnitudes for both pumps. For the two-blade pump, fluctuations attenuate toward overload irrespective of the particular pump circuit, while they rise for the single-blade pump. 3D simulation results yield detailed insight into the spatially and temporally resolved impeller–volute interaction and reveal that the single-blade impeller pushes a high-pressure flow region forward in a way as a positive displacement pump, resulting in an inherently fluctuating velocity and pressure distribution within the volute.

scholarly journals Development of Small Rotating Stall in a Single Stage Axial Compressor

1985 ◽  
Author(s):  
K. Mathioudakis ◽  
F. A. E. Breugelmans
Keyword(s):  
Experimental Study ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Propagation Speed ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Blade Surface ◽  
Hot Wire ◽  
Additional Information ◽  
Cell Pattern

In this paper we present the results of a detailed experimental study of the development of small rotating stall, as it appears in a one stage axial compressor. Stationary hot-wire probes are used to measure the variation of amplitude and propagation speed of the disturbances caused by small stall. Measurements near the rotor blade surface with rotating probes provide additional information on the nature of the phenomenon. The development of the cell pattern for different operating conditions is studied. The different character from what is known as “big stall” is demonstrated.

scholarly journals Numerical Simulation of Two-Stage Variable Geometry Turbine

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5349
Author(s):  
Dariusz Kozak ◽  
Paweł Mazuro ◽  
Andrzej Teodorczyk
Keyword(s):  
Combustion Engine ◽  
Three Dimensional ◽  
High Load ◽  
Operating Conditions ◽  
Two Stage ◽  
Variable Turbine Geometry ◽  
Low Load ◽  
Variable Geometry Turbine ◽  
Stage System ◽  
Maintenance Requirements

The modern internal combustion engine (ICE) has to meet several requirements. It has to be reliable with the reduced emission of pollutant gasses and low maintenance requirements. What is more, it has to be efficient both at low-load and high-load operating conditions. For this purpose, a variable turbine geometry (VTG) turbocharger is used to provide proper engine acceleration of exhaust gases at low-load operating conditions. Such a solution is also efficient at high-load engine operating conditions. In this paper, the result of an unsteady, three-dimensional (3D) simulation of the variable two-stage turbine system is discussed. Three different VTG positions were considered for those simulations, along with three different turbine speeds. The turbine inlet was modeled as six equally placed exhaust pipes for each cylinder to eliminate the interference of pressure waves. The flow field at the outlet of the 1st stage nozzle vane and 2nd stage rotor was investigated. The simulations showed that the variable technologies significantly improve the efficiency of the two-stage turbine system. The highest overall efficiency of the two-stage system was achieved at 60,000 rpm and 11o VTG position.

scholarly journals Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 890 ◽  
Author(s):  
Yusif A. Alghamdi ◽  
Zhengbiao Peng ◽  
Caimao Luo ◽  
Zeyad Almutairi ◽  
Behdad Moghtaderi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Single Species ◽  
Terminal Velocity ◽  
Operating Conditions ◽  
Cold Flow ◽  
Fluidization Regime ◽  
Spectrum Density

This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressure fluctuation in the air reactor and in the riser when compared to SSS experiments. The standard deviation (SD) of the pressure fluctuation was found to be influenced by the fluidization regime and initial operating conditions, while the power spectrum density (PSD) values were more sensitive to the presence of the particles with the higher terminal velocity in the binary mixture.

scholarly journals Analysis of Unsteady Pressure Fluctuation in a Semi-Open Cutting Pump

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3657
Author(s):  
Weidong Cao ◽  
Jiayu Mao ◽  
Wei Li
Keyword(s):  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Lower Plate ◽  
Pressure Distributions ◽  
Axial Forces ◽  
Blade Frequency

In order to understand the pressure fluctuation characteristics of a semi-open cutting pump, the three-dimensional unsteady flow fields were calculated. External and internal flow characteristics of four schemes with different relative angles between the rotary cutter and the impeller were studied. The pressure fluctuations in the lower plate, the upper plate, the clearance between the rotary cutter and the fixed cutter, the first section in volute and nearby parts of the tongue were all analyzed, which are all the places that pressure distributions are greatly affected by the static and dynamic interaction, and at the same time, the force on the impeller was also analyzed. The results show that the fluctuations at different positions change periodically; the main frequency is blade frequency. The amplitude of pressure fluctuation decreases from near the rotating part to far away, from near the tongue to far from the tongue. Due to the influence of both impeller and rotary cutter, the pressure fluctuation on the lower plate is the largest. The pressure fluctuation is affected by flow rate, the larger the flow rate, the greater the pressure fluctuation. The radial and axial forces of the impeller change periodically with time, and the number of wave peaks and wave valleys is the same as the number of blades.

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