scholarly journals Experimental and Analytical Assessment of Cavity Modes in a Gas Turbine Wheelspace

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Rachel A. Berg ◽  
C. S. Tan ◽  
Zhongman Ding ◽  
Gregory Laskowski ◽  
Pepe Palafox ◽  
...  
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Flow Direction ◽  
Pressure Oscillation ◽  
Fast Response ◽  
Hot Gas ◽  
Modal Response ◽  
Cavity Modes ◽  
Oscillation Modes ◽  
Purge Flow

Fast response pressure data acquired in a high-speed 1.5-stage turbine hot gas ingestion rig (HGIR) show the existence of pressure oscillation modes in the rim-seal-wheelspace cavity of a high pressure gas turbine stage with purge flow. The experimental results and observations are complemented by computational assessments of pressure oscillation modes associated with the flow in canonical cavity configurations. The cavity modes identified include shallow cavity modes and Helmholtz resonance. The response of the cavity modes to variation in design and operating parameters are assessed. These parameters include cavity aspect ratio (AR), purge flow ratio, and flow direction defined by the ratio of primary tangential to axial velocity. Scaling the cavity modal response based on computational results and available experimental data in terms of the appropriate reduced frequencies appears to indicate the potential presence of a deep cavity mode as well. While the role of cavity modes on hot gas ingestion cannot be clarified based on the current set of data, the unsteady pressure field associated with turbine rim cavity modal response can be expected to drive ingress/egress.

scholarly journals Experimental and Analytical Assessment of Cavity Modes in a Gas Turbine Wheelspace

2017 ◽  
Author(s):  
Rachel A. Berg ◽  
C. S. Tan ◽  
Zhongman Ding ◽  
Gregory Laskowski ◽  
Pepe Palafox ◽  
...  
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Flow Direction ◽  
Pressure Oscillation ◽  
Fast Response ◽  
Hot Gas ◽  
Modal Response ◽  
Cavity Modes ◽  
Oscillation Modes ◽  
Purge Flow

Fast response pressure data acquired in a high-speed 1.5-stage turbine Hot Gas Ingestion Rig shows the existence of pressure oscillation modes in the rim-seal-wheelspace cavity of a high pressure gas turbine stage with purge flow. The experimental results and observations are complemented by computational assessments of pressure oscillation modes associated with the flow in canonical cavity configurations. The cavity modes identified include shallow cavity modes and Helmholtz resonance. The response of the cavity modes to variation in design and operating parameters are assessed. These parameters include cavity aspect ratio, purge flow ratio, and flow direction defined by the ratio of primary tangential to axial velocity. Scaling the cavity modal response based on computational results and available experimental data in terms of the appropriate reduced frequencies appears to indicate the potential presence of a deep cavity mode as well. While the role of cavity modes on hot gas ingestion cannot be clarified based on the current set of data, the unsteady pressure field associated with turbine rim cavity modal response can be expected to drive ingress/egress.

Modeling and Control of Combustion Dynamics in Industrial Gas Turbines

2004 ◽  
Author(s):  
Keith McManus ◽  
Fei Han ◽  
Wayne Dunstan ◽  
Corneliu Barbu ◽  
Minesh Shah
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Oscillation ◽  
Fast Response ◽  
Operating Conditions ◽  
Fuel System ◽  
Combustion Dynamics ◽  
Modeling And Control ◽  
Persistent Excitation ◽  
Industrial Gas Turbines

The thermoacoustic response of an industrial-scale gas turbine combustor to fuel flow perturbations is examined. Experimental measurements in a laboratory combustor along with numerical modeling results are used to identify the dynamic behavior of the combustor over a variety of operating conditions. A fast-response actuator was coupled to the fuel system to apply continuous sinusoidal perturbations to the total fuel mass flow rate. The effects of these perturbations on the combustor pressure oscillation characteristics as well as overall operability of the system are described. The results of this work suggest that persistent excitation of the fuel system may present a viable means of controlling combustion dynamics in industrial gas turbine and, in turn, enhance their performance.

Fast Response Probes Measuring Unsteady Flows in High-Speed Research Compressors

2003 ◽  
Author(s):  
C. Georgakis ◽  
I. Bennett ◽  
P. C. Ivey
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Pressure Fluctuations ◽  
Unsteady Flows ◽  
Fast Response ◽  
Temperature Drift ◽  
Flow Measurements ◽  
Simple Geometry ◽  
Single Sensor ◽  
Measurements Errors

It is well recognised that multi-sensor fast response probes are widely used on several applications concerning unsteady flow measurements. Often the size of these probes is larger than ideal. It is probably this reason that the single sensor probes are sometimes preferred in the survey of the unsteady flows in the turbomachinery applications. This in turn can be of benefit due to the limited space often found in compressors. The advent of these miniature probes has been made possible due to the availability of small sensors capable of withstanding relatively high temperatures. There is no doubt that as the technology improves, the size of the probes is likely to be reduced. This will make it possible to use these probes in lower cost, smaller scale facilities. The behavior of a fast response probe is examined in detail prior to the presentation of a set of unsteady measurements acquired near the impeller tip region. The data obtained from the calibration routine is then compared with the actual measurements. Errors that could possibly be arising due to temperature drift of the sensor are taken into account and reduced to a minimum. The fast response probe is largely sensitive to pressure fluctuations that, after correction with temperature, result in an actual pressure reading. The sensitivity of the probe has proved to be adequate for measurement of flow direction and total pressure over a broad angular range. The simple geometry and small size of the probe contributes to a reduction in the blockage effects, the enhancement of the near wall measurements, the reduction of the run-time costs, and raise the confidence in the experiment. This fast response probe was extensively used to traverse the blade passage width. Detailed measurements clearly showed that strong pulsations dominate the distorted impeller exit flow.

Modulation and Radial Migration of Turbine Hub Cavity Modes by the Rim Seal Purge Flow

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
R. Schädler ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
G. Schmid ◽  
S. Voelker
Keyword(s):  
Gas Turbines ◽  
Fast Response ◽  
Loss Mechanism ◽  
Axial Turbine ◽  
Pressure Transducers ◽  
Aerodynamic Loss ◽  
Numerical Predictions ◽  
Cavity Modes ◽  
Annulus Flow ◽  
Purge Flow

In the present paper, the results of an experimental and numerical investigation of the hub cavity modes and their migration into the main annulus flow are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with three-dimensionally shaped blades and cylindrical end walls has been tested in an axial turbine facility. Both the blade design and the rim seal purge flow path are representative to modern high-pressure gas turbines. The unsteady flow field at the hub cavity exit region has been measured with the fast-response aerodynamic probe (FRAP) for two different rim seal purge flow rates. Furthermore, fast-response wall-mounted pressure transducers have been installed inside the cavity. Unsteady full-annular computational fluid dynamics (CFD) simulations have been employed in order to complement the experimental work. The time-resolved pressure measurements inside the hub cavity reveal clear cavity modes, which show a strong dependency on the injected amount of rim seal purge flow. The numerical predictions provide information on the origin of these modes and relate them to pronounced ingestion spots around the circumference. The unsteady probe measurements at the rim seal interface show that the signature of the hub cavity induced modes migrates into the main annulus flow up to 30% blade span. Based on that, an aerodynamic loss mechanism has been found, showing that the benefit in loss reduction by decreasing the rim seal purge flow rate is weakened by the presence of turbine hub cavity modes.

Modulation and Radial Migration of Turbine Hub Cavity Modes by the Rim Seal Purge Flow

2016 ◽  
Author(s):  
R. Schädler ◽  
A. I. Kalfas ◽  
R. S. Abhari ◽  
G. Schmid ◽  
S. Voelker
Keyword(s):  
Gas Turbines ◽  
Fast Response ◽  
Loss Mechanism ◽  
Axial Turbine ◽  
Pressure Transducers ◽  
Aerodynamic Loss ◽  
Numerical Predictions ◽  
Cavity Modes ◽  
Annulus Flow ◽  
Purge Flow

In the present paper, the results of an experimental and numerical investigation of the hub cavity modes and their migration into the main annulus flow are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and cylindrical end walls has been tested in an axial turbine facility. Both, the blade design and the rim seal purge flow path are representative to modern high pressure gas turbines. The unsteady flow field at the hub cavity exit region has been measured with the fast-response aerodynamic probe (FRAP) for two different rim seal purge flow rates. Furthermore, fast-response wall mounted pressure transducers have been installed inside the cavity. Unsteady full-annular CFD simulations have been employed in order to complement the experimental work. The time-resolved pressure measurements inside the hub cavity reveal clear cavity modes which show a strong dependency on the injected amount of rim seal purge flow. The numerical predictions provide information on the origin of these modes and relate them to pronounced ingestion spots around the circumference. The unsteady probe measurements at the rim seal interface show that the signature of the hub cavity induced modes migrates into the main annulus flow up to 30% blade span. Based on that, an aerodynamic loss mechanism has been found, showing that the benefit in loss reduction by decreasing the rim seal purge flow rate is weakened by the presence of turbine hub cavity modes.

Direct Current Deadbeat Predictive Controller for BLDC Motor Using Single DC-Link Current Sensor

2020 ◽  
Vol 38 (8A) ◽  
pp. 1187-1199
Author(s):  
Qaed M. Ali ◽  
Mohammed M. Ezzalden
Keyword(s):  
Control System ◽  
High Speed ◽  
Fast Response ◽  
Bldc Motor ◽  
Current Controller ◽  
Three Phase ◽  
Predictive Controller ◽  
Two Phases ◽  
Dc Current ◽  
Three Phase Inverter

BLDC motors are characterized by electronic commutation, which is performed by using an electric three-phase inverter. The direct control system of the BLDC motor consists of double loops; including the inner-loop for current regulating and outer-loop for speed control. The operation of the current controller requires feedback of motor currents; the conventional current controller uses two current sensors on the ac side of the inverter to measure the currents of two phases, while the third current would be accordingly calculated. These two sensors should have the same characteristics, to achieve balanced current measurements. It should be noted that the sensitivity of these sensors changes with time. In the case of one sensor fails, both of them must be replaced. To overcome this problem, it is preferable to use one sensor instead of two. The proposed control system is based on a deadbeat predictive controller, which is used to regulate the DC current of the BLDC motor. Such a controller can be considered as digital controller mode, which has fast response, high precision and can be easily implemented with microprocessor. The proposed control system has been simulated using Matlab software, and the system is tested at a different operating condition such as low speed and high speed.

Effects of the positive pre-swirl purge flow on endwall aero-thermal performance of a gas turbine blade

2021 ◽  
Vol 163 ◽  
pp. 106805
Author(s):  
Zhi Tao ◽  
Fengchao Li ◽  
Boyang Yu ◽  
Peiyuan Zhu ◽  
Liming Song ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Gas Turbine Blade ◽  
Purge Flow

Experimental Investigation During Stall and Surge in a Transonic Fan Stage and Rotor-Only Configuration

2006 ◽  
Author(s):  
A. J. Gannon ◽  
G. V. Hobson ◽  
R. P. Shreeve ◽  
I. J. Villescas
Keyword(s):  
High Speed ◽  
Fast Response ◽  
Pressure Measurements ◽  
Post Processing ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
The Difference ◽  
Data Signal ◽  
Transonic Fan ◽  
Casing Pressure

High-speed pressure measurements of a transonic compressor rotor-stator stage and rotor-only configuration during stall and surge are presented. Rotational speed data showed the difference between the rotor-only case and rotor-stator stage. The rotor-only case stalled and remained stalled until the control throttle was opened. In the rotor-stator stage the compressor surged entering a cyclical stalling and then un-stalling pattern. An array of pressure probes was mounted in the case wall over the rotor for both configurations of the machine. The fast response probes were sampled at 196 608 Hz as the rotor was driven into stall. Inspection of the raw data signal allowed the size and speed of the stall cell during its growth to be investigated. Post-processing of the simultaneous signals of the casing pressure showed the development of the stall cell from the point of inception and allowed the structure of the stall cell to be viewed.

scholarly journals Wall Temperature Measurements in Gas Turbine Combustors With Thermographic Phosphors

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Patrick Nau ◽  
Zhiyao Yin ◽  
Oliver Lammel ◽  
Wolfgang Meier
Keyword(s):  
Gas Turbine ◽  
Wall Temperature ◽  
Gas Turbines ◽  
High Speed ◽  
Bluff Body ◽  
Temperature Measurements ◽  
Transient Temperature ◽  
High Time Resolution ◽  
Ceramic Surface ◽  
Precessing Vortex Core

Phosphor thermometry has been developed for wall temperature measurements in gas turbines and gas turbine model combustors. An array of phosphors has been examined in detail for spatially and temporally resolved surface temperature measurements. Two examples are provided, one at high pressure (8 bar) and high temperature and one at atmospheric pressure with high time resolution. To study the feasibility of this technique for full-scale gas turbine applications, a high momentum confined jet combustor at 8 bar was used. Successful measurements up to 1700 K on a ceramic surface are shown with good accuracy. In the same combustor, temperatures on the combustor quartz walls were measured, which can be used as boundary conditions for numerical simulations. An atmospheric swirl-stabilized flame was used to study transient temperature changes on the bluff body. For this purpose, a high-speed setup (1 kHz) was used to measure the wall temperatures at an operating condition where the flame switches between being attached (M-flame) and being lifted (V-flame) (bistable). The influence of a precessing vortex core (PVC) present during M-flame periods is identified on the bluff body tip, but not at positions further inside the nozzle.

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