scholarly journals Wall-Modelled Large Eddy Simulations of Axial Turbine Rim Sealing

2020 ◽  
Author(s):  
Donato M. Palermo ◽  
Feng Gao ◽  
Dario Amirante ◽  
John W. Chew ◽  
Anna Bru Revert ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Passive Scalar ◽  
Rotor Blades ◽  
Computational Time ◽  
Scalar Concentration ◽  
Large Eddy ◽  
Annulus Flow ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Good Agreement

Abstract This paper presents WMLES simulations of a chute type turbine rim seal. Configurations with an axisymmetric annulus flow and with nozzle guide vanes fitted (but without rotor blades) are considered. The passive scalar concentration solution and WMLES are validated against available data in the literature for uniform convection and a rotor-stator cavity flow. The WMLES approach is shown to be effective, giving significant improvements over an eddy viscosity turbulence model, in prediction of rim seal effectiveness compared to research rig measurements. WMLES requires considerably less computational time than wall-resolved LES, and has the potential for extension to engine conditions. All WMLES solutions show rotating inertial waves in the chute seal. Good agreement between WMLES and measurements for sealing effectiveness in the configuration without vanes is found. For cases with vanes fitted the WMLES simulation shows less ingestion than the measurements, and possible reasons are discussed.

Wall-Modelled Large Eddy Simulations of Axial Turbine Rim Sealing

2021 ◽  
Author(s):  
Donato Maria Palermo ◽  
Feng Gao ◽  
Dario Amirante ◽  
John W. Chew ◽  
Anna Bru Revert ◽  
...  
Keyword(s):  
Eddy Viscosity ◽  
Passive Scalar ◽  
Rotor Blades ◽  
Computational Time ◽  
Scalar Concentration ◽  
Large Eddy ◽  
Annulus Flow ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Good Agreement

Abstract This paper presents WMLES simulations of a chute type turbine rim seal. Configurations with an axisymmetric annulus flow and with nozzle guide vanes fitted (but without rotor blades) are considered. The passive scalar concentration solution and WMLES are validated against available data in the literature for uniform convection and a rotor-stator cavity flow. The WMLES approach is shown to be effective, giving significant improvements over an eddy viscosity turbulence model, in prediction of rim seal effectiveness compared to research rig measurements. WMLES requires considerably less computational time than wall-resolved LES, and has the potential for extension to engine conditions. All WMLES solutions show rotating inertial waves in the chute seal. Good agreement between WMLES and measurements for sealing effectiveness in the configuration without vanes is found. For cases with vanes fitted the WMLES simulation shows less ingestion than the measurements, and possible reasons are discussed.

Degradation of Aerodynamic Performance of an Intermediate-Pressure Steam Turbine Due to Erosion of Nozzle Guide Vanes and Rotor Blades

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Koichi Yonezawa ◽  
Tomoki Kagayama ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Steam Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Flow Angle ◽  
Guide Vanes ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Deteriorations of nozzle guide vanes (NGVs) and rotor blades of a steam turbine through a long-time operation usually decrease a thermal efficiency and a power output of the turbine. In this study, influences of blade deformations due to erosion are discussed. Experiments were carried out in order to validate numerical simulations using a commercial software ANSYS-cfx. The numerical results showed acceptable agreements with experimental results. Variation of flow characteristics in the first stage of the intermediate pressure steam turbine is examined using numerical simulations. Geometries of the NGVs and the rotor blades are measured using a 3D scanner during an overhaul. The old NGVs and the rotor blades, which were used in operation, were eroded through the operation. The erosion of the NGVs leaded to increase of the throat area of the nozzle. The numerical results showed that rotor inlet velocity through the old NGVs became smaller and the flow angle of attack to the rotor blade leading edge became smaller. Consequently, the rotor power decreased significantly. Influences of the flow angle of at the rotor inlet were examined by parametric calculations and results showed that the angle of attack was an important parameter to determine the rotor performance. In addition, the influence of the deformation of the rotor blade was examined. The results showed that the degradation of the rotor performance decreased in accordance with the decrease of blade surface area.

Effect of Annulus Flow Conditions on Turbine Rim Seal Ingestion

2019 ◽  
Author(s):  
Donato M. Palermo ◽  
Feng Gao ◽  
John W. Chew ◽  
Paul F. Beard
Keyword(s):  
Velocity Ratio ◽  
Axial Flow ◽  
Passive Scalar ◽  
External Flow ◽  
Rotor Blades ◽  
Flow Structures ◽  
Flow Conditions ◽  
Sealing Performance ◽  
Annulus Flow ◽  
The Mean

Abstract A systematic study of sealing performance for a chute style turbine rim seal using URANS methods is reported. This extends previous studies from a configuration without external flow in the main annulus to cases with a circumferentially uniform axial flow and vane generated swirling annulus flow (but without rotor blades). The study includes variation of the mean seal-to-rotor velocity ratio, main annulus-to-rotor velocity ratio, and seal clearance. The effects on the unsteady flow structures and the degree of main annulus flow ingestion into the rim seal cavity are examined. Sealing effectiveness is quantified by modeling a passive scalar, and the timescales for the convergence of this solution are considered. It has been found that intrinsic flow unsteadiness occurs in most cases, with the presence of vanes and external flow modifying, the associated flow structures and frequencies. Some sensitivities to the annulus flow conditions are identified. The circumferential pressure asymmetry generated by the vanes has a clear influence on the flow structure but does not lead to higher ingestion rates than the other conditions studied.

Prediction of Ingestion Through Turbine Rim Seals—Part I: Rotationally Induced Ingress

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
J. Michael Owen
Keyword(s):  
Flow Rate ◽  
Turbine Blades ◽  
External Pressure ◽  
Swirling Flows ◽  
Radial Gradient ◽  
Mainstream Flow ◽  
Predicted Values ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Good Agreement

The mainstream flow past the stationary nozzle guide vanes and rotating turbine blades in a gas turbine creates an unsteady nonaxisymmetric variation in pressure in the annulus, radially outward of the rim seal. The ingress and egress occur through those parts of the seal clearance where the external pressure is higher and lower, respectively, than that in the wheel-space; this nonaxisymmetric type of ingestion is referred to here as externally induced (EI) ingress. Another cause of ingress is that the rotating air inside the wheel-space creates a radial gradient of pressure so that the pressure inside the wheel-space can be less than that outside; this creates rotationally induced (RI) ingress, which—unlike EI ingress—can occur, even if the flow in the annulus is axisymmetric. Although the EI ingress is usually dominant in a turbine, there are conditions under which both EI and RI ingress are significant, these cases are referred to as combined ingress. In Part I of this two-part paper, the so-called orifice equations are derived for compressible and incompressible swirling flows, and the incompressible equations are solved analytically for the RI ingress. The resulting algebraic expressions show how the nondimensional ingress and egress vary with Θ0, which is the ratio of the flow rate of sealing air to the flow rate necessary to prevent ingress. It is shown that ε, the sealing effectiveness, depends principally on Θ0, and the predicted values of ε are in mainly in good agreement with the available experimental data.

An Impact Assessment of Erosion of Nozzle Guide Vanes and Rotor Blades on Aerodynamic Performance of a Gas Turbine by CFD

2019 ◽  
Author(s):  
Koichi Yonezawa ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
Katsuhiko Sugita ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Rotor Blade ◽  
Cfd Simulation ◽  
Rotor Blades ◽  
Total Power ◽  
Guide Vanes ◽  
Turbine Performance ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Abstract Nozzle guide vanes (NGVs) and rotor blades deteriorate due to erosion, and this may affect the aerodynamic characteristics of gas turbines. According to previous studies, the erosion of first-stage NGVs significantly affected the blade loading of the first-stage rotor. An increase in the tip gap also may significantly affect the gas turbine performance. In the present study, numerical investigations have been carried out using a real eroded nozzle and blade geometries for two purposes. One purpose was to clarify the influences underlying the deterioration of the nozzle and the rotor blade, such as the effects on the erosion of NGVs in the first stage and the effects of the tip gap on the gas turbine performance. The other was to develop a method to estimate the total gas turbine performance using a CFD simulation and a heat balance analysis. The results show that the erosion of NGV leads to an increased flow rate and affects the operating condition of the gas turbine cycle. This, in turn, can decrease the total thermal efficiency. The experimental results suggest that an increase in the tip gap width decreases rotor output almost linearly, and the numerical results showed the same tendency. The influence of the tip gap in the real gas turbine condition was also examined, revealing that an increase in the tip gap leads to an increase in the pressure loss in the nozzle downstream as well as around the rotor blade itself. Consequently, the total power output and the isentropic efficiency of the turbine decreased.

Effects of Microjets in Flow Over a Backward-Facing Step

2012 ◽  
Author(s):  
H. Kanchi ◽  
F. Mashayek
Keyword(s):  
Passive Scalar ◽  
Streamwise Velocity ◽  
Inlet Pipe ◽  
Backward Facing Step ◽  
Passive Scalars ◽  
Eddy Simulation ◽  
Pipe Section ◽  
Large Eddy ◽  
Normal Fluctuations ◽  
Good Agreement

Large eddy simulation is used to study the flow over a backward-facing step interacting with a periodic array of streamwise microjets emenating from the step at a 45° angle to the step face. Averaged streamwise velocity profiles are in good agreement with experimental data. A well defined turbulent inlet profile for the microjet is found to be important to obtain correct streamwise normal fluctuations near the step. To simulate cases as per the experimental setup a microjet inlet pipe section is necessary for the simulations. The studies with passive scalars need to be conducted to quantify scalar mixing. The monotonicity problem of simulating passive scalar can be overcome by simply clipping the unbounded values. This technique works because the volume occupied by overshoot values of passive scalar are small compared to the total volume of the backward-facing step geometry.

Study over thermal state of gas turbine engine metal-ceramic rotor blades and nozzle guide vanes under thermal shock and thermal-cyclic loading conditions

2004 ◽  
Vol 13 (2) ◽  
pp. 163-166
Author(s):  
A. V. Soudarev ◽  
A. A. Souryaninov ◽  
V. Ya. Podgorets ◽  
V. V. Grishaev ◽  
V.Yu Tikhoplav ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Thermal Shock ◽  
Gas Turbine ◽  
Thermal State ◽  
Rotor Blades ◽  
Guide Vanes ◽  
Turbine Engine ◽  
Metal Ceramic ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Prediction of Ingestion Through Turbine Rim Seals—Part 1: Rotationally-Induced Ingress

2009 ◽  
Author(s):  
J. Michael Owen
Keyword(s):  
Flow Rate ◽  
Swirling Flow ◽  
Turbine Blades ◽  
External Pressure ◽  
Radial Gradient ◽  
Mainstream Flow ◽  
Predicted Values ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Good Agreement

The mainstream flow past the stationary nozzle guide vanes and rotating turbine blades in a gas turbine creates an unsteady non-axisymmetric variation of pressure in the annulus radially outward of the rim seal. Ingress and egress occur through those parts of the seal clearance where the external pressure is higher and lower, respectively, than that in the wheel-space; this non-axisymmetric type of ingestion is referred to here as externally-induced (EI) ingress. Another cause of ingress is that the rotating air inside the wheel-space creates a radial gradient of pressure so that the pressure inside the wheel-space can be less than that outside; this creates rotationally-induced (RI) ingress, which — unlike EI ingress — can occur even if the flow in the annulus is axisymmetric. Although EI ingress is usually dominant in a turbine, there are conditions under which both EI and RI ingress are significant: these cases are referred to as combined ingress. In Part 1 of this two-part paper, the so-called orifice equations are derived for compressible and incompressible swirling flow, and the incompressible equations are solved analytically for RI ingress. The resulting algebraic expressions show how the nondimensional ingress and egress vary with Θ0, the ratio of the flow rate of sealing air to the flow rate necessary to prevent ingress. It is shown that ε, the sealing effectiveness, depends principally on Θ0, and the predicted values of ε are in mainly good agreement with available experimental data. Part 2 (ASME GT2009-59122) concentrates on the solution and validation of the orifice equations for EI and combined ingress.

scholarly journals Design of a Tandem Compressor for the Electrically-Driven Turbocharger of a Hybrid City Car

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2890
Author(s):  
Nicolò Cuturi ◽  
Enrico Sciubba
Keyword(s):  
Gasoline Engine ◽  
Rotor Blades ◽  
Battery Pack ◽  
Net Energy ◽  
Design Data ◽  
Intermediate Point ◽  
Dynamics Simulations ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
Operating Points

Within a broader national project aimed at the hybridization of a standard city car (the 998 cc Mitsubishi-derived gasoline engine of the Smart W451), our team tackled the problem of improving the supercharger performance and response. The originally conceived design innovation was that of eliminating the mechanical connection between the compressor and the turbine. In the course of the study, it turned out that it is also possible to modify both components to extract extra power from the engine and to use it to recharge the battery pack. This required a redesign of both compressor and turbine. First, the initial configuration was analyzed on the basis of the design data provided by the manufacturer. Then, a preliminary performance assessment of the turbocharged engine allowed us to identify three “typical” operating points that could be used to properly redesign the turbomachinery. It was decided to maintain the radial configuration for both turbine and compressor, but to redesign the latter by adding an inducer. For the turbine, only minor modifications to the nozzle guide vanes (NGV) and rotor blades shape were deemed necessary, while a more substantial modification was in order for the compressor. Fully 3-D computational fluid dynamics simulations of the rotating machines were performed to assess their performance at three operating points: the kick-in point of the original turbo (2000 rpm), the maximum power regime (5500 rpm), and an intermediate point (3500 rpm) close to the minimum specific fuel consumption for the original engine. The results presented in this paper demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three operating points, and that its choking characteristics have been improved, while its surge line has not been appreciably affected. The net energy recovery was also calculated and demonstrated interesting returns in terms of storable energy in the battery pack.

scholarly journals Large Eddy Simulation of Scalar Mixing in Jet in a Cross-Flow

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Asela Uyanwaththa ◽  
Weeratunge. Malalasekera ◽  
Graham Hargrave ◽  
Mark Dubal
Keyword(s):  
Experimental Data ◽  
Velocity Field ◽  
Large Eddy Simulation ◽  
Cross Flow ◽  
Passive Scalar ◽  
Scalar Mixing ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Fuel Mixing ◽  
Good Agreement

Jet in a cross-flow (JICF) is a flow arrangement found in many engineering applications, especially in gas turbine air–fuel mixing. Understanding of scalar mixing in JICF is important for low NOx burner design and operation, and numerical simulation techniques can be used to understand both spatial and temporal variation of air–fuel mixing quality in such applications. In this paper, mixing of the jet stream with the cross-flow is simulated by approximating the jet flow as a passive scalar and using the large eddy simulation (LES) technique to simulate the turbulent velocity field. A posteriori test is conducted to assess three dynamic subgrid scale models in modeling jet and cross-flow interaction with the boundary layer flow field. Simulated mean and Reynolds stress component values for velocity field and concentration fields are compared against experimental data to assess the capability of the LES technique, which showed good agreement between numerical and experimental results. Similarly, time mean and standard deviation values of passive scalar concentration also showed good agreement with experimental data. In addition, LES results are further used to discuss the scalar mixing field in the downstream mixing region.

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