scholarly journals Flow instability effects related to purge through a gas turbine chute seal

2021 ◽  
Vol 5 ◽  
pp. 111-125
Author(s):  
Arijit Roy ◽  
Jens Fridh ◽  
James Scobie ◽  
Carl Sangan ◽  
Gary Lock
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Flow Instability ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Pressure Measurements ◽  
Flow Conditions ◽  
Seal Design ◽  
Purge Flow ◽  
Unsteady Pressure Measurements

This paper investigates flow instabilities inside the cavity formed between the stator and rotor disks of a high-speed turbine rig. The cavity rim seal is of chute seal design. The influence of flow coefficient on the sealing effectiveness at constant purge flow rate through the wheel-space is determined. The effectiveness at different radial positions over a range of purge flow conditions and flow coefficients is also studied. Unsteady pressure measurements have identified the frequency of instabilities that form within the rim seal, phenomena which have been observed in other studies. Frequencies of these disturbances, and their correlation in the circumferential direction have determined the strength and speed of rotation of the instabilities within the cavity. Large scale unsteady rotational structures have been identified, which show similarity to previous studies. These disturbances have been found to be weakly dependent on the purge flow and flow coefficients, although an increased purge reduced both the intensity and speed of rotation of the instabilities. Additionally, certain uncorrelated disturbances have been found to be inconsistent (discontinuous) with pitchwise variation.

The Effect of Vanes and Blades on Ingress in Gas Turbines

2019 ◽  
Author(s):  
Fabian P. T. Hualca ◽  
Josh T. M. Horwood ◽  
Carl M. Sangan ◽  
Gary D. Lock ◽  
James A. Scobie
Keyword(s):  
Flow Rate ◽  
Gas Turbines ◽  
Large Scale ◽  
Strong Influence ◽  
Rotor Blades ◽  
Pressure Measurements ◽  
Test Rig ◽  
Purge Flow ◽  
Unsteady Pressure Measurements ◽  
The Relationship

Abstract This paper presents experimental and computational results using a 1.5-stage test rig designed to investigate the effects of ingress through a double radial overlap rim-seal. The effect of the vanes and blades on ingress was investigated by a series of carefully-controlled experiments: firstly, the position of the vane relative to the rim seal was varied; secondly, the effect of the rotor blades was isolated using a disc with and without blades. Measurements of steady pressure in the annulus show a strong influence of the vane position. The relationship between sealing effectiveness and purge flow-rate exhibited a pronounced inflexion for intermediate levels of purge; the inflexion did not occur for experiments with a bladeless rotor. Shifting the vane closer to the rim-seal, and therefore the blade, caused a local increase in ingress in the inflexion region; again this effect was not observed for the bladeless experiments. Unsteady pressure measurements at the periphery of the wheel-space revealed the existence of large-scale pressure structures (or instabilities) which depended weakly on the vane position and sealing flow rate. These were measured with and without the blades on the rotor disc. In all cases these structures rotated close to the disc speed.

Influence of Flow Coefficient on Ingress Through Turbine Rim Seals

2021 ◽  
Author(s):  
Dimitrios Graikos ◽  
Mauro Carnevale ◽  
Carl M. Sangan ◽  
Gary D. Lock ◽  
James A. Scobie
Keyword(s):  
Large Scale ◽  
Rotor Blades ◽  
Flow Coefficient ◽  
Radial Clearance ◽  
Flow Conditions ◽  
Large Scale Structures ◽  
Wide Range ◽  
Purge Flow ◽  
Mass Flow Rates ◽  
Engine Components

Abstract Rim seals are critical in terms of limiting the temperature of highly-stressed engine components but function with a penalty to the power output and contribute to entropy gain stemming from mixing losses in the turbine. Ingress through rim seals is influenced by the presence of rotor blades and stator vanes, and the mainstream flow coefficient in the annulus that determines the corresponding swirl. This paper presents an experimental study of ingress upstream and downstream of the rotor disc in a 1.5-stage rig with double radial clearance rim seals. Two rotor discs were used, one with blades and one without, and two platforms were used downstream of the rotor, one with vanes and one without. Tests were conducted at two rotational speeds and a range of flow conditions was achieved by varying the annulus and sealing mass flow rates. Concentration effectiveness, swirl and steady pressure measurements separated, for the first time, the influence of the blades and vanes on ingress over a wide range of flow conditions. Measurements on the downstream stator platform provide added insight into the complex interaction between the egress and the mainstream. Measurements of unsteady pressure revealed the presence of large-scale structures, even in the absence of blades. The number and speed of the structures was shown to depend on the flow coefficient and the purge flow rate.

Influence of Flow Coefficient On Ingress Through Turbine Rim Seals

2021 ◽  
Author(s):  
Dimitrios Graikos ◽  
Mauro Carnevale ◽  
Carl Sangan ◽  
Gary Lock ◽  
James Scobie
Keyword(s):  
Large Scale ◽  
Rotor Blades ◽  
Flow Coefficient ◽  
Radial Clearance ◽  
Flow Conditions ◽  
Large Scale Structures ◽  
Wide Range ◽  
Purge Flow ◽  
Mass Flow Rates ◽  
Engine Components

Abstract Rim seals are critical in terms of limiting the temperature of highly-stressed engine components but function with a penalty to the power output and contribute to entropy gain stemming from mixing losses in the turbine. Ingress through rim seals is influenced by the presence of rotor blades and stator vanes, and the mainstream flow coefficient in the annulus that determines the corresponding swirl. This paper presents an experimental study of ingress upstream and downstream of the rotor disc in a 1.5-stage rig with double radial clearance rim seals. Two rotor discs were used, one with blades and one without, and two platforms were used downstream of the rotor, one with vanes and one without. Tests were conducted at two rotational speeds and a range of flow conditions was achieved by varying the annulus and sealing mass flow rates. Concentration effectiveness, swirl and steady pressure measurements separated, for the first time, the influence of the blades and vanes on ingress over a wide range of flow conditions. Measurements on the downstream stator platform provide added insight into the complex interaction between the egress and the mainstream. Measurements of unsteady pressure revealed the presence of large-scale structures, even in the absence of blades. The number and speed of the structures was shown to depend on the flow coefficient and the purge flow rate.

Experimental Study of Flow Patterns, Pressure Drop and Flow Instabilities in Parallel Rectangular Minichannels

2004 ◽  
Author(s):  
Prabhu Balasubramanian ◽  
Satish G. Kandlikar
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Instability ◽  
Flow Boiling ◽  
Pressure Fluctuations ◽  
Flow Patterns ◽  
Flow Instabilities ◽  
Stable Operation ◽  
Phase System ◽  
High Heat Flux

The use of phase change heat transfer in parallel minichannels and microchannels is one of the solutions proposed for cooling high heat flux systems. The increase in pressure drop in a two phase system is one of the problems, that need to be studied in detail before proceeding to any design phase. The pressure drop fluctuations in a network of parallel channels connected by a common head need to be addressed for stable operation of flow boiling systems. The current work focuses on studying the pressure-drop fluctuations and flow instabilities in a set of six parallel rectangular minichannels, each with 333 μm hydraulic diameter. Demonized and degassed water was used for all the experiments. Pressure fluctuations are recorded and signal analysis is performed to find the dominant frequencies and their amplitudes. These pressure fluctuations are then mapped to their corresponding flow patterns observed using a high speed camera. The results help us to relate pressure fluctuations to different flow characteristics, and their effect on flow instability.

The Effect of Vanes and Blades on Ingress in Gas Turbines

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Fabian P. Hualca ◽  
Joshua T. M. Horwood ◽  
Carl M. Sangan ◽  
Gary D. Lock ◽  
James A. Scobie
Keyword(s):  
Gas Turbines ◽  
Large Scale ◽  
Strong Influence ◽  
Rotor Blades ◽  
Pressure Measurements ◽  
Computational Results ◽  
Test Rig ◽  
Rotor Disk ◽  
Unsteady Pressure Measurements ◽  
The Relationship

Abstract This paper presents experimental and computational results using a 1.5-stage test rig designed to investigate the effects of ingress through a double radial overlap rim-seal. The effect of the vanes and blades on ingress was investigated by a series of carefully controlled experiments: first, the position of the vane relative to the rim seal was varied; second, the effect of the rotor blades was isolated using a disk with and without blades. Measurements of steady pressure in the annulus show a strong influence of the vane position. The relationship between sealing effectiveness and purge flowrate exhibited a pronounced inflection for intermediate levels of purge; the inflection did not occur for experiments with a bladeless rotor. Shifting the vane closer to the rim-seal, and therefore the blade, caused a local increase in ingress in the inflection region; again, this effect was not observed for the bladeless experiments. Unsteady pressure measurements at the periphery of the wheel-space revealed the existence of large-scale pressure structures (or instabilities) which depended weakly on the vane position and sealing flowrate. These were measured with and without the blades on the rotor disk. In all cases, these structures rotated close to the disk speed.

Suppression of Self-Excited Flow Instability in a Radial Diffuser Using Rough Surfaces

2006 ◽  
Author(s):  
Saad A. Ahemd ◽  
Hayder Salem
Keyword(s):  
Flow Rate ◽  
Smooth Surface ◽  
Flow Instability ◽  
Rough Surfaces ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Low Flow ◽  
Flow Rates ◽  
Flow Limit ◽  
Stable Operating

Flow instabilities in a compression system at low flow rates set the flow limit of the stable operating range. Experiments to investigate the feasibility of controlling the stall in the radial diffuser of a low speed centrifugal compressor were carried out. The technique was very simple and involved using rough surfaces (i.e., sand papers) attached to the diffuser shroud. The results showed that the flow instability in the diffuser (stall) was delayed to a lower flow coefficient (the mass flow rate could be reduced to 70% of its value with the smooth surface) when the rough surfaces were positioned on the diffuser shroud.

High Speed PIV Measurement of Impinging Flow on a Horizontal Axis Wind Turbine

2012 ◽  
Author(s):  
J. Stephen Hu ◽  
Jian Sheng ◽  
Michele Guala ◽  
Leonardo Chamorro
Keyword(s):  
Boundary Layer ◽  
Angular Velocity ◽  
Wind Turbine ◽  
Power Output ◽  
High Speed ◽  
Large Scale ◽  
Flow Structures ◽  
Flow Conditions ◽  
Horizontal Axis Wind Turbine ◽  
Impinging Flow

The focus of this paper is to characterize the upstream wake of a three bladed Horizontal Axis Wind Turbine (HAWT) and its interaction with the native structures within a turbulent boundary layer (TBL). The overarching question is the most prevailing length and time scales of coherent structures that would interact with a HAWT and how they would be affected. The implications include wall flow and structure interaction and flow induced noise generation in large scale turbo machineries. The experiments are performed on a turbine that has a 0.128 m rotor diameter, a hub height of 0.104 m and a tip speed ratio of 4. The HAWT model is placed in a large scale wind tunnel in a boundary layer with a thickness δ of ∼0.6 m. The boundary layer is generated by a 60 mm picket fence trip and developed over a smooth wall under thermally neutral conditions. Measurements are performed under ReD of 4 × 105 and 6 × 105. Both turbine geometries and flow conditions are scaled from operating conditions in the field. High speed Particle Image Velocimetry (PIV), turbine voltage output, and angular velocity measurements are conducted simultaneously, by which one could relate the upwind flow structures with the power output of the turbine. High speed PIV offer details in spatial and temporal characteristics of the impinging flow structures, whilst the voltage anemometer and tachometer provide instantaneous measurement of angular velocity of the turbine. PIV measurements are taken at a rate of 1500 image pairs per second with a 100 μs delay between laser pulses. Each sample area is 0.15 × 0.15 cm. Two locations up to two rotor diameters upwind are measured. Instantaneous voltage is taken at a sampling rate of 30 kHz and a sampling time of 60s to ensure sufficient temporal resolution and coverage. Ongoing analysis using conditional averaging based on extreme power output events will provide insights in assessing a HAWT performance in unsteady flow conditions.

Evaluating the Effects of Transient Purge Flow on Stator-Rotor Seal Performance

2019 ◽  
Author(s):  
Reid A. Berdanier ◽  
Eric T. DeShong ◽  
Karen A. Thole
Keyword(s):  
Measurement Techniques ◽  
Operating Conditions ◽  
Pressure Measurements ◽  
Flow Conditions ◽  
Melting Temperatures ◽  
Increased Risk ◽  
Thermally Driven ◽  
Purge Flow ◽  
Transient Events ◽  
Thermal Lag

Abstract As modern engine designs target higher efficiencies through increased turbine inlet temperatures, critical turbine components are at increased risk of damage from conditions exceeding material melting temperatures. In particular, improperly designed underplatform hardware components are susceptible to damage when hot main gas path flow is ingested into the stator-rotor cavity. While all turbines inherently experience transients during operation, a majority of turbine tests have been executed using steady operating conditions, and routine transient events are not well understood. To address this need, the present study utilizes a continuous-duration, one-stage test turbine operating with true-scale engine hardware and seal geometries at engine-representative flow conditions. The nature of the continuous-duration facility uniquely supports direct assessment of transient events through its ability to transition between steady-state operating conditions. Specifically, the effects of a transient purge flow were investigated in this study to identify general trends for transient events in a full-scale engine. Results from multiple measurement techniques in the wheelspace region show an interdependence of transient purge flow with a thermal lag of the underplatform hardware. Through experiments conducted at different coolant-to-main gas path temperature ratios, the use of pressure measurements as an indicator of fully-purged behavior was introduced, and a thermally-driven influence on rim seal performance was quantified.

Two Phase Boiling and Flow Instabilities in a Microchannel

2007 ◽  
Author(s):  
Jacqueline Barber ◽  
K. Sefiane ◽  
D. Brutin ◽  
L. Tadrist
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
High Speed ◽  
Flow Instability ◽  
High Heat ◽  
Heat Fluxes ◽  
Flow Reversal ◽  
Flow Instabilities ◽  
Moving Contact Line ◽  
Moving Contact

Boiling in microchannels is a very efficient mode of heat transfer. High heat and mass transfer coefficients are achieved. Evaporation of the liquid meniscus is the main contributor to the high heat fluxes achieved due to phase change at thin liquid films in a microchannel. The microscale hydrodynamic motion and the mechanisms at the immediate vicinity of the moving contact line are still not fully comprehended. There are several flow instabilities during boiling in microchannels. These instabilities need to be well understood and predicted due to their adverse effects on the heat transfer. It is hoped to understand particular flow instabilities, such as flow reversal, through experimental research at the contact line. A simultaneous visualisation and measurement experiment was carried out to investigate these flow instabilities in microchannels. Boiling has been induced in a microchannel (dh 570 μm), stabilising just one liquid-vapour interface, and observing its progression through various microchannel geometries. Images and video sequences have been achieved with both a high speed camera and an infra red camera. Analysis of these images allow the application of several existing models to be fitted to our flow instability observations, namely flow reversal and its possible mechanism of vapour recoil, at the moving contact line.

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