Design Optimization of a Retractable Holder for Compressor Discharge Brush Seal

2011 ◽  
Author(s):  
Omprakash Samudrala ◽  
Siddarth Kumar ◽  
Christopher E. Wolfe ◽  
Raymond E. Chupp
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Thermal Response ◽  
Flow Path ◽  
Design Parameters ◽  
Operating Life ◽  
Design And Optimization ◽  
Design Variables ◽  
Brush Seal ◽  
Purge Flow

In many industrial gas turbines, a portion of the compressor discharge air is extracted through a secondary flow path to aid the cooling of critical turbine components as well as to supplement purge flow for preventing hot gas ingestion in the first forward turbine bucket wheel space. GE has developed advanced brush seals for controlling the amount of cooling/purge flow passing through this secondary flow path (also called the high pressure packing (HPP) circuit) and has successfully implemented them in the field in a variety of E, F & H class gas turbines. During turbine shutdown, due to a lag in thermal response between the rotor and the stator, interference can result between brush seal bristles and the rotor surface causing significant amounts of wear. This wear can accumulate over several start up / shut down cycles resulting in an increased secondary flow through the HPP circuit and thus a loss in turbine efficiency and power output. In order to alleviate this situation, a seal holder has been designed to passively retract the HPP brush seal, from a low clearance position to a high clearance position, during turbine shut down and thus prevent seal interference/wear. This paper delves into the design and optimization of a retractable seal. An analytical model was developed to predict the seal motion during startup and shutdown of the turbine. Critical geometry and design parameters affecting seal closure and retraction behavior were identified. In addition, criteria for stability of seal motion were developed and the design was optimized to meet these requirements. Seal wear during turbine shutdown is avoided by ensuring that the seal retracts faster than the rate of thermally induced interference. The effect of design variables was minimized to ensure seal closure and retraction behavior does not vary significantly over the operating life of the seal. Model predictions were validated by subscale rig tests performed in the laboratory.

Measurements and Modeling of Ingress in a New 1.5-Stage Turbine Research Facility

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Marios Patinios ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
Gary D. Lock
Keyword(s):  
Theoretical Model ◽  
Gas Turbines ◽  
Test Facility ◽  
Radial Clearance ◽  
Operating Life ◽  
The Core ◽  
Wide Range ◽  
Purge Flow ◽  
Rotor Disk ◽  
Engine Components

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor disks as a result of the circumferential pressure asymmetry in the annulus; this ingress can significantly affect the operating life, performance, and integrity of highly stressed, vulnerable engine components. Rim seals, fitted at the periphery of the disks, are used to minimize ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the disks. This paper presents experimental results from a new 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disk. The fluid-dynamically scaled rig operates at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements. The test facility features interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing flow rates. The rig was specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries. The radial variation of CO2 gas concentration, pressure, and swirl is measured to explore, for the first time, the flow structure in both the upstream and downstream wheel-spaces. The measurements show that the concentration in the core is equal to that on the stator walls and that both distributions are virtually invariant with radius. These measurements confirm that mixing between ingress and egress is essentially complete immediately after the ingested fluid enters the wheel-space and that the fluid from the boundary layer on the stator is the source of that in the core. The swirl in the core is shown to determine the radial distribution of pressure in the wheel-space. The performance of a double radial-clearance seal is evaluated in terms of the variation of effectiveness with sealing flow rate for both the upstream and the downstream wheel-spaces and is found to be independent of rotational Reynolds number. A simple theoretical orifice model was fitted to the experimental data showing good agreement between theory and experiment for all cases. This observation is of great significance as it demonstrates that the theoretical model can accurately predict ingress even when it is driven by the complex unsteady pressure field in the annulus upstream and downstream of the rotor. The combination of the theoretical model and the new test rig with its flexibility and capability for detailed measurements provides a powerful tool for the engine rim-seal designer.

Measurements and Modelling of Ingress in a New 1.5-Stage Turbine Research Facility

2016 ◽  
Author(s):  
Marios Patinios ◽  
James A. Scobie ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
Gary D. Lock
Keyword(s):  
Theoretical Model ◽  
Gas Turbines ◽  
Test Facility ◽  
Radial Clearance ◽  
Operating Life ◽  
The Core ◽  
Wide Range ◽  
Purge Flow ◽  
Engine Components ◽  
First Time

In gas turbines, hot mainstream flow can be ingested into the wheel-space formed between stator and rotor discs as a result of the circumferential pressure asymmetry in the annulus; this ingress can significantly affect the operating life, performance and integrity of highly-stressed, vulnerable engine components. Rim seals, fitted at the periphery of the discs, are used to minimise ingress and therefore reduce the amount of purge flow required to seal the wheel-space and cool the discs. This paper presents experimental results from a new 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc. The fluid-dynamically-scaled rig operates at incompressible flow conditions, far removed from the harsh environment of the engine which is not conducive to experimental measurements. The test facility features interchangeable rim-seal components, offering significant flexibility and expediency in terms of data collection over a wide range of sealing-flow rates. The rig was specifically designed to enable an efficient method of ranking and quantifying the performance of generic and engine-specific seal geometries. The radial variation of CO2 gas concentration, pressure and swirl is measured to explore, for the first time, the flow structure in both the upstream and downstream wheel-spaces. The measurements show that the concentration in the core is equal to that on the stator walls and that both distributions are virtually invariant with radius. These measurements confirm that mixing between ingress and egress is essentially complete immediately after the ingested fluid enters the wheel-space and that the fluid from the boundary-layer on the stator is the source of that in the core. The swirl in the core is shown to determine the radial distribution of pressure in the wheel-space. The performance of a double radial-clearance seal is evaluated in terms of the variation of effectiveness with sealing flow rate for both the upstream and the downstream wheel-spaces and is found to be independent of rotational Reynolds number. A simple theoretical orifice model was fitted to the experimental data showing good agreement between theory and experiment for all cases. This observation is of great significance as it demonstrates that the theoretical model can accurately predict ingress even when it is driven by the complex unsteady pressure field in the annulus upstream and downstream of the rotor. The combination of the theoretical model and the new test rig with its flexibility and capability for detailed measurements provides a powerful tool for the engine rim-seal designer.

Volumetric Velocimetry Measurements of Purge–Mainstream Interaction in a One-Stage Turbine

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Blade Passage ◽  
One Stage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Vortex Tracking of Purge-Mainstream Interactions in a Rotating Turbine Stage

2021 ◽  
Author(s):  
Alex W. Mesny ◽  
Mark A. Glozier ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
Yan Sheng Li ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Horseshoe Vortex ◽  
Suction Surface ◽  
Vortex Filaments ◽  
Passage Vortex ◽  
Purge Flow

Abstract The use of purge flow in gas turbines allows for high turbine entry temperatures, which are essential to produce high cycle efficiency. Purge air is bled from the compressor and reintroduced in the turbine to cool vulnerable components. Wheel-spaces are formed between adjacent rotating and stationary discs, with purge air supplied at low radius before exiting into the mainstream gas-path through a rim-seal at the disc periphery. An aerodynamic penalty is incurred as the purge flow egress interacts with the mainstream. This study presents unparalleled three-dimensional velocity data from a single-stage turbine test rig, specifically designed to investigate egress-mainstream interaction using optical measurement techniques. Volumetric Velocimetry is applied to the rotating environment with phase-locked measurements used to identify and track the vortical secondary flow features through the blade passage. A baseline case without purge flow is compared to experiments with a 1.7% purge mass fraction; the latter was chosen to ensure a fully sealed wheel-space. A non-localised vortex tracking function is applied to the data to identify the position of the core centroids. The strength of the secondary-flow vortices was determined by using a circulation criterion on rotated planes aligned to the vortex filaments. The pressure-side leg of the horseshoe vortex and a second vortex associated with the egress flow were identified by the experimental campaign. In the absence of purge flow the two vortices merged, forming the passage vortex. With the addition of purge flow, the two cores remained independent to 40% of the blade axial chord, while also demonstrating an increased radial migration and intensification of the passage vortex. The egress core was shown to remain closer to the suction-surface with purge flow. Importantly, where the vortex filaments demonstrated strong radial or tangential components of velocity, the circulation level calculated from axial planes underpredicted the true circulation by up to 50%.

scholarly journals On the Optimization of a Centrifugal Maglev Blood Pump Through Design Variations

2021 ◽  
Vol 12 ◽  
Author(s):  
Peng Wu ◽  
Jiadong Huo ◽  
Weifeng Dai ◽  
Wei-Tao Wu ◽  
Chengke Yin ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Performance Metrics ◽  
Flow Path ◽  
Secondary Flows ◽  
Blood Pump ◽  
Flow Paths ◽  
Blade Thickness ◽  
Design Variables ◽  
Blood Pumps ◽  
The Impact

Centrifugal blood pumps are usually designed with secondary flow paths to avoid flow dead zones and reduce the risk of thrombosis. Due to the secondary flow path, the intensity of secondary flows and turbulence in centrifugal blood pumps is generally very high. Conventional design theory is no longer applicable to centrifugal blood pumps with a secondary flow path. Empirical relationships between design variables and performance metrics generally do not exist for this type of blood pump. To date, little scientific study has been published concerning optimization and experimental validation of centrifugal blood pumps with secondary flow paths. Moreover, current hemolysis models are inadequate in an accurate prediction of hemolysis in turbulence. The purpose of this study is to optimize the hydraulic and hemolytic performance of an inhouse centrifugal maglev blood pump with a secondary flow path through variation of major design variables, with a focus on bringing down intensity of turbulence and secondary flows. Starting from a baseline design, through changing design variables such as blade angles, blade thickness, and position of splitter blades. Turbulent intensities have been greatly reduced, the hydraulic and hemolytic performance of the pump model was considerably improved. Computational fluid dynamics (CFD) combined with hemolysis models were mainly used for the evaluation of pump performance. A hydraulic test was conducted to validate the CFD regarding the hydraulic performance. Collectively, these results shed light on the impact of major design variables on the performance of modern centrifugal blood pumps with a secondary flow path.

Volumetric Velocimetry Measurements of Purge-Mainstream Interaction in a 1-Stage Turbine

2020 ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Complex Flow ◽  
Blade Passage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flow-field. Of particular interest to the designer is the effect of purge on the secondary flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and Computational Fluid Dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically-accessible 1-stage turbine rig. The experimental campaign was conducted using Volumetric Velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using URANS computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the roll-up of a horseshoe-vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flow-rate, was shown to modify the secondary flow field by enhancing the passage vortex, both in strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Re-Ingestion of Upstream Egress in a 1.5-Stage Gas Turbine Rig

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
James A. Scobie ◽  
Fabian P. Hualca ◽  
Marios Patinios ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Co2 Concentration ◽  
Test Facility ◽  
Operating Life ◽  
Annulus Flow ◽  
Purge Flow ◽  
Rotor Disk ◽  
First Time ◽  
Measured Mass ◽  
Insight Into

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimize the purge flow required to seal the wheel-space between the discs. Ingestion (or ingress) of hot mainstream gases through rim seals is a threat to the operating life and integrity of highly stressed components, particularly in the first-stage turbine. Egress of sealing flow from the first-stage can be re-ingested in downstream stages. This paper presents experimental results using a 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disk. Re-ingestion was quantified using measurements of CO2 concentration, with seeding injected into the upstream and downstream sealing flows. Here, a theoretical mixing model has been developed from first principles and validated by the experimental measurements. For the first time, a method to quantify the mass fraction of the fluid carried over from upstream egress into downstream ingress has been presented and measured; it was shown that this fraction increased as the downstream sealing flow rate increased. The upstream purge was shown to not significantly disturb the fluid dynamics but only partially mixes with the annulus flow near the downstream seal, with the ingested fluid emanating from the boundary layer on the blade platform. From the analogy between heat and mass transfer, the measured mass-concentration flux is equivalent to an enthalpy flux, and this re-ingestion could significantly reduce the adverse effect of ingress in the downstream wheel-space. Radial traverses using a concentration probe in and around the rim seal clearances provide insight into the complex interaction between the egress, ingress and mainstream flows.

Re-Ingestion of Upstream Egress in a 1.5-Stage Gas Turbine Rig

2017 ◽  
Author(s):  
James A. Scobie ◽  
Fabian P. Hualca ◽  
Marios Patinios ◽  
Carl M. Sangan ◽  
J. Michael Owen ◽  
...  
Keyword(s):  
First Principles ◽  
Gas Turbines ◽  
Co2 Concentration ◽  
Test Facility ◽  
Operating Life ◽  
Annulus Flow ◽  
Purge Flow ◽  
First Time ◽  
Measured Mass ◽  
Insight Into

In gas turbines, rim seals are fitted at the periphery of stator and rotor discs to minimise the purge flow required to seal the wheel-space between the discs. Ingestion (or ingress) of hot mainstream gases through rim seals is a threat to the operating life and integrity of highly-stressed components, particularly in the first-stage turbine. Egress of sealing flow from the first-stage can be re-ingested in downstream stages. This paper presents experimental results using a 1.5-stage test facility designed to investigate ingress into the wheel-spaces upstream and downstream of a rotor disc. Re-ingestion was quantified using measurements of CO2 concentration, with seeding injected into the upstream and downstream sealing flows. Here a theoretical mixing model has been developed from first principles and validated by the experimental measurements. For the first time, a method to quantify the mass fraction of the fluid carried over from upstream egress into downstream ingress has been presented and measured; it was shown that this fraction increased as the downstream sealing flow rate increased. The upstream purge was shown to not significantly disturb the fluid dynamics but only partially mixes with the annulus flow near the downstream seal, with the ingested fluid emanating from the boundary layer on the blade platform. From the analogy between heat and mass transfer, the measured mass-concentration flux is equivalent to an enthalpy flux and this re-ingestion could significantly reduce the adverse effect of ingress in the downstream wheel-space. Radial traverses using a concentration probe in and around the rim seal clearances provide insight into the complex interaction between the egress, ingress and mainstream flows.

Stiffness Measurement for Pressure-Loaded Brush Seals

2011 ◽  
Author(s):  
Rahul A. Bidkar ◽  
Xiaoqing Zheng ◽  
Mehmet Demiroglu ◽  
Norman Turnquist
Keyword(s):  
Gas Turbines ◽  
Design Parameters ◽  
Test Results ◽  
Pressure Loading ◽  
Friction Forces ◽  
Test Fixture ◽  
Hysteresis Behavior ◽  
Brush Seal ◽  
Wide Range ◽  
Brush Seals

Brush seals are widely used as flexible seals for rotor-stator and stator-stator gaps in power generation turbo-machinery like steam turbines, gas turbines, generators and aircraft engines. Understanding the force interactions between a brush seal bristle pack and the rotor is important for avoiding overheating and rotor dynamic instabilities caused by excessive brush seal forces. Brush seal stiffness (i.e. brush seal force per unit circumferential length per unit incursion of the rotor) is usually measured and characterized at atmospheric pressure conditions. However, the inter-bristle forces, the blow-down forces and the friction forces between the backplate and the bristle pack change in the presence of a pressure loading, thereby changing the stiffness of the brush seal in the presence of this pressure loading. Furthermore, brush seals exhibit different hysteresis behavior under different pressure loading conditions. Understanding the increased brush seal stiffness and the increased hysteresis behavior of brush seals in the presence of a pressure loading is important for designing brush seals for higher pressure applications. In this article, we present the development of a test fixture for measuring the stiffness of brush seals subjected to a pressure loading. The fixture allows for measurement of the bristle pack forces in the presence of a pressure loading on the seal while the rotor is incrementally pushed (radially) into the bristle pack. Following the development of this test fixture, we present representative test results on three sample seals to show the trends in brush seal stiffness as the pressure loading is increased. Specifically, we study the effect of different brush seal design parameters on the stiffness of brush seals over a wide range of pressure loadings. These test data can be used for developing predictive models for brush seal stiffness under pressure loading. Furthermore, we demonstrate the utility of this fixture in studying the hysteresis exhibited by brush seals along with the importance of the backplate pressure balance feature present in several brush seal designs. The test results validate the bilinear force-displacement curves previously reported in the literature.

Optimization of a Micro Gas Turbine Using Genetic Algorithm

2011 ◽  
Author(s):  
Maryam Pourhasanzadeh ◽  
Sajjad Bigham
Keyword(s):  
Genetic Algorithm ◽  
Combustion Chamber ◽  
Objective Function ◽  
Gas Turbine ◽  
Distributed Generation ◽  
Gas Turbines ◽  
Design Parameters ◽  
Micro Gas Turbine ◽  
Design Variables ◽  
Isentropic Efficiency

Distributed generation is an attractive way of producing energy, minimizing transport losses and enhancing energy efficiency. Micro gas turbines in distributed generation systems add other advantages such as low emissions and fuel flexibility. In the present work, a 100 kW micro gas turbine is considered. The optimization procedure is done by Genetic Algorithm method which is a new method in optimizing problems. The plant is comprised of an air compressor, recuperator, combustion chamber and gas turbine. The design Parameters of the plant, were chosen as: compressor pressure ratio, compressor isentropic efficiency, gas turbine isentropic efficiency, combustion chamber inlet temperature and the temperature of the combustion gas at the gas turbine inlet. In order to find the design parameters optimally, a thermo-economic approach has been followed. An objective function, representing the total cost of the plant in terms of dollar per second, was defined as the sum of the operating cost, related to the fuel consumption, the capital investment which stands for equipment purchase and maintenance cost. Subsequently, different parts of the objective function have been expressed in terms of design variables. Finally, the optimal values of design variables were obtained by minimizing the objective function using Genetic Algorithm code that is developed in Matlab software programming.

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