Mitigation of Pressure Fluctuations From an Array of Pulse Detonation Combustors

2021 ◽  
Author(s):  
Mohammad Rezay Haghdoost ◽  
Bhavraj S. Thethy ◽  
Daniel Edgington-Mitchell ◽  
Fabian Habicht ◽  
Johann Vinkeloe ◽  
...  
Keyword(s):  
High Frequency ◽  
Pressure Fluctuations ◽  
Shock Interaction ◽  
Pressure Measurements ◽  
Test Rig ◽  
Velocity Fluctuations ◽  
Firing Patterns ◽  
Pressure Transducers ◽  
Pulse Detonation ◽  
Shock Dynamics

Abstract An annular plenum is integrated downstream of six pulse detonation combustors arranged in a can-annular configuration. The primary purpose of the plenum is the mitigation of pressure and velocity fluctuations, which is crucial for operation with a downstream turbine. The flow inside the plenum is investigated by means of flush-mounted pressure transducers arranged in axial and circumferential directions. The test rig is operated in different firing patterns at frequencies up to 16.7 Hz per tube. Two firing patterns are studied to characterize the shock dynamics inside the plenum. The obtained data allow for a better understanding of shock interaction and attenuation inside the plenum as well as the quantification of pressure fluctuations at the plenum outlet. Furthermore, a comparison is made between piezoresistive and piezoelectric pressure transducers showing the capability of piezoresistive transducers for high frequency pressure measurements.

Measurements of the Pressure and Velocity Distribution in Low-Speed Turbomachinery by Means of High-Frequency Pressure Transducers

1992 ◽  
Vol 114 (1) ◽  
pp. 100-107 ◽  
Author(s):  
S. Brodersen ◽  
D. Wulff
Keyword(s):  
High Frequency ◽  
Pressure Fluctuations ◽  
Design Flow ◽  
Measuring Technique ◽  
Pressure Probe ◽  
Blade Loading ◽  
Low Speed ◽  
Pressure Transducers ◽  
Multiple Samples ◽  
Very High

The flow in a low-speed, single-state compressor with a very high blade loading has been measured using a two-probe arrangement. The measuring technique and data reduction procedure described have been especially adjusted for application in low-speed turbomachinery. Those machines show only small pressure fluctuations in the flow downstream of the rotor, for which specific requirements concerning the measuring technique have been taken into account. The probes used contain unsteady pressure transducers and simulate an unsteady multisensor pressure probe. This technique proves to be suitable for applications in low-speed turbomachinery. The measurements are based on phase-locked ensemble averages of multiple samples, where the data are acquired using a simple and convenient experimental setup. This allows the velocity and pressure distribution of the flow to be determined in rotor coordinates. The results show the flow field and the loss distribution of an aero-dynamically highly loaded rotor at design flow rate.

A New Test Rig for Time-Resolved Pressure Measurements in Rotating Cavities With Pulsed Inflow

2010 ◽  
Author(s):  
Gunar Schroeder ◽  
Wieland Uffrecht
Keyword(s):  
Gas Turbines ◽  
Pressure Fluctuations ◽  
Rotational Frequency ◽  
Internal Cooling ◽  
Pressure Measurements ◽  
Test Rig ◽  
Time Resolved ◽  
Air System ◽  
Unsteady Effects ◽  
Cooling Air

The improvement of the overall performance and efficiency of gas turbines, especially in the internal cooling air system is of general interest. This requires the reduction of pressure losses induced by vortices and secondary flow. The steady state effects are known from literature and experiments. But also pressure fluctuations and oscillations e.g. resonances have an impact on the efficiency of the internal cooling air system. These unsteady effects are only principally discussed in the literature. Experimental investigations of pressure fluctuations and oscillations in rotating cavities, which are part of the internal air system, are very rare. One reason might be given by the fact that the investigation of these unsteady effects is a technical challenge especially for higher rotational speeds. This paper presents a new rotor test rig with a telemetric measurement system which permits time-resolved pressure measurements in the cavity. The cavity dimensions are similar to those of a real industrial gas turbine. The design of the test rig and the telemetric system allows rotational frequencies up to 10000 rpm. The current experimental investigation is focused on pressure fluctuations and oscillations in rotating cavities with through flow and their dependency on the test parameters. The aim is to find out the relevant effects for operation and design optimisation of rotating cavities in gas turbines. The rig consists of a stationary air delivery and an axial air transfer interface between the stator and the rotor. The rotor contains one cavity. The interface acts as a flow chopper. The air is blown from the stator drillings to the rotating inlet holes of the rotor which provide the connection to the cavity inside the rotor. The rotating holes pass the stator holes periodically, causing pressure fluctuations in the cavity. The frequency of the fluctuations depends on the rotational frequency of the rotor and the number of inlet and stator drillings, which can be varied. The tests are carried out for a range of the parameter Reφ, calculated with the outer radius of the cavity, up to 1·106 and for different mass flow rates. The new test rig, the setup, the instrumentation and the first measurements are the topic of this paper. The non-stationary effects found in the cavity and their dependency on the parameters rotational frequency and mass flow will be discussed and compared with known theoretical approaches.

Time-Resolved Pressure Measurements at a Dual-Cavity Test Rig for Research on the Internal Air System of an Industrial Gas Turbine

2014 ◽  
Author(s):  
André Günther ◽  
Wieland Uffrecht ◽  
Volker Caspary
Keyword(s):  
Gas Turbines ◽  
Pressure Fluctuations ◽  
Pressure Measurements ◽  
Test Rig ◽  
Time Resolved ◽  
Hot Gas ◽  
Air Supply ◽  
Internal Cavities ◽  
Air System ◽  
Cooling Air

This paper reports about time-resolved examination of the pressure in a dual-cavity test rig for research on the cooling air supply of industrial gas turbines. The test rig has stationary and telemetric instrumentation. Both systems are capable of time-resolved pressure measurement. The design of the test rig is based on a simplified geometry of the internal cavities of the high pressure turbine with receiver holes and simulates the restriction imposed by internal blade cooling flow circuits. The test rig consists of a rotor-stator cavity and a rotor-rotor cavity. The Stage One and Stage Two supplies are separated inside the rotor-stator cavity. The air enters axially without pre-swirl at the outer radius of the stator and leaves the rotor-stator cavity through three rotating, axially directed connecting holes at a radius that varies among the investigated cases. Therefore, different flow paths in the cavities are studied. The research is focused on the branched cooling air supply system, but the flow path can also be analyzed separately. The rim seal flow is not examined in the research work presented here. Pressure fluctuations in the main gas path caused, for instance, by blade passing and combustor noise, are a well-known phenomenon and therefore the subject of current research, whereas experimental examinations of the pressure fluctuations in the internal air system of gas turbines are very rare. A detailed examination of the pressure in the internal air system is significant in light of the pressure difference between the main gas path and internal air system, which is the driving force for hot gas ingestion. In that sense, the difference between the average pressure on the main gas side to the average pressure in the internal air system is not enough to avoid hot gas ingestion. Therefore, this paper focuses on pressure fluctuations in the internal cavities. The measurements of the pressure fluctuations in the rotor-stator cavity are presented for different operating conditions. The influence of the rotational speed, the mass flow rate, the flow path and the sensor position in the cavity on the time-resolved pressure is examined. Furthermore, time-resolved pressure measurements from the rotor-rotor cavity are presented. Variations of the axial gap size and the radial location of the connecting holes respective to the outlets of the rotor-stator cavity are described.

Overtip Pressure Measurements in a Cold-Flow Turbine Rig

1990 ◽  
Author(s):  
R. C. Kingcombe ◽  
I. M. Smith ◽  
R. V. Steeden
Keyword(s):  
Frequency Response ◽  
High Frequency ◽  
Significant Loss ◽  
Rotor Blades ◽  
Pressure Measurements ◽  
Pressure Transducers ◽  
Cold Flow ◽  
High Frequency Response ◽  
Axial Turbines

In shroudless axial turbines the flow over the tips of the rotor blades is complex and accounts for significant loss of efficiency. In order to investigate the structure of this overtip flow, a row of high frequency response miniature pressure transducers was mounted in the casing of a cold flow turbine rig in the region swept by the rotor tips.

High-Frequency Acoustic Mode Identification of Unstable Combustors

2019 ◽  
Author(s):  
J. Kim ◽  
T. Lieuwen ◽  
B. Emerson ◽  
V. Acharya ◽  
D. Wu ◽  
...  
Keyword(s):  
High Frequency ◽  
Least Squares Method ◽  
Pressure Fluctuations ◽  
Acoustic Mode ◽  
Modal Identification ◽  
Mode Shapes ◽  
Similar Frequency ◽  
Pressure Transducers ◽  
Mode Identification ◽  
The Time Domain

Abstract High frequency thermoacoustic instabilities are becoming increasingly problematic in modern combustion systems. Understanding which acoustic mode is being excited is important for understanding potential mechanisms and control approaches — for example, influence of a helical shear layer mode on the flame has profoundly different effects on the first tangential acoustic mode, than a higher order axial mode of similar frequency. Nonetheless, the modal density increases with frequency and it becomes increasingly difficult to determine which acoustic mode is self-excited, based upon frequency calculations alone. Moreover, access issues and cost usually limit the number of pressure probes that can be distributed axially and azimuthally in the combustor. This paper presents a methodology for identifying the acoustic mode by using high temperature pressure transducers flush mounted in a combustion chamber. Modal identification is demonstrated with a siren under non-reacting conditions. The siren is mounted on the chamber to excite longitudinal and azimuthal waves. Five acoustic sensors at different axial and azimuthal locations measure the pressure fluctuations simultaneously. Given the forcing frequency and the speed of sound, the pressure distribution in the combustor is reconstructed in the time domain from the measured data by using a least squares method to determine its mode shapes. In addition, the finite element method (FEM) solver is used to provide the eigenfrequencies and corresponding mode shapes. The test results demonstrate that the mode shapes from the reconstructed data and corresponding frequencies are consistent with those predicted from the FEM, which validates the methodology in this study. In addition, the methodology is extended to practical reacting cases without the siren to determine the acoustic mode shapes of naturally occurring instabilities. In these cases, the modal features have strong stochastic features, such as what appear to be stochastic variations in overall amplitude and relative amplitudes of clockwise and counterclockwise waves.

The Effect of the Operating Point on the Pressure Fluctuations at the Blade Passage Frequency in the Volute of a Centrifugal Pump

2002 ◽  
Vol 124 (3) ◽  
pp. 784-790 ◽  
Author(s):  
Jorge L. Parrondo-Gayo ◽  
Jose´ Gonza´lez-Pe´rez ◽  
Joaquı´n Ferna´ndez-Francos
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Fast Response ◽  
Strong Increase ◽  
Flow Rates ◽  
Blade Passage ◽  
Pressure Transducers ◽  
Leading Role ◽  
Dynamic Forces ◽  
Response Pressure

An experimental investigation is presented which analyzes the unsteady pressure distribution existing in the volute of a conventional centrifugal pump with a nondimensional specific speed of 0.48, for flow-rates from 0% to 160% of the best-efficiency point. For that purpose, pressure signals were obtained at 36 different locations along the volute casing by means of fast-response pressure transducers. Particular attention was paid to the pressure fluctuations at the blade passage frequency, regarding both amplitude and phase delay relative to the motion of the blades. Also, the experimental data obtained was used to adjust the parameters of a simple acoustic model for the volute of the pump. The results clearly show the leading role played by the tongue in the impeller-volute interaction and the strong increase in the magnitude of dynamic forces and dipole-like sound generation in off-design conditions.

Aerodynamic Noise Characterization of a Full-Scale Wind Turbine through High-Frequency Surface Pressure Measurements

2015 ◽  
Vol 14 (5-6) ◽  
pp. 729-766 ◽  
Author(s):  
Franck Bertagnolio ◽  
Helge Aa. Madsen ◽  
Christian Bak ◽  
Niels Troldborg ◽  
Andreas Fischer
Keyword(s):  
Wind Turbine ◽  
Surface Pressure ◽  
High Frequency ◽  
Full Scale ◽  
Aerodynamic Noise ◽  
Pressure Measurements ◽  
Noise Characterization

Relationship Between Unsteady Flow, Pressure Fluctuations, and Noise in a Centrifugal Pump—Part B: Effects of Blade-Tongue Interactions

1995 ◽  
Vol 117 (1) ◽  
pp. 30-35 ◽  
Author(s):  
S. Chu ◽  
R. Dong ◽  
J. Katz
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Pressure Difference ◽  
Pressure Fluctuations ◽  
Primary Sources ◽  
Pressure Measurements ◽  
Local Pressure ◽  
Pressure Distributions ◽  
Flow Pressure ◽  
Tip Of The Tongue

Maps of pressure distributions computed using PDV data, combined with noise and local pressure measurements, are used for identifying primary sources of noise in a centrifugal pump. In the vicinity of the impeller pressure minima occur around the blade and near a vortex train generated as a result of non-uniform outflux from the impeller. The pressure everywhere also varies depending on the orientation of the impeller relative to the tongue. Noise peaks are generated when the pressure difference across the tongue is maximum, probably due to tongue oscillations, and when the wake impinges on the tip of the tongue.

The Effect of HFPD Thermally Sprayed WC-Co Coatings on the Fatigue Behavior and Deformation of Al 2024-T4

2000 ◽  
Author(s):  
A. Ibrahim ◽  
C.C. Berndt
Keyword(s):  
High Frequency ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Pulse Detonation ◽  
Deformation Behaviors ◽  
Life Distributions ◽  
Thermally Sprayed ◽  
Al 2024 ◽  
Frequency Pulse

Abstract The effect of high frequency pulse detonation (HFPD) and HVOF thermally sprayed WC-Co coatings on the high cycle fatigue (HCF) behavior of 2024-T4 aluminum was investigated. The fatigue life distributions of specimens in the polished and coated conditions are presented as a function of the probability of failure. The monotonic and cyclic deformation behaviors of the as-received and as-coated specimens were investigated. The conclusions show that, (i) the HFPD sprayed specimens exhibited slightly higher fatigue lives compared to the uncoated specimens, (ii) the HVOF sprayed specimens exhibited significantly higher fatigue lives compared to the uncoated specimens, and (iii) the as-coated specimen was cyclically stable.

Transonic Turbine Stage Heat Transfer Investigation in Presence of Strong Shocks

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
A. de la Loma ◽  
G. Paniagua ◽  
D. Verrastro ◽  
P. Adami
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Shock Interaction ◽  
Turbine Stage ◽  
Test Rig ◽  
Unsteady Heat Transfer ◽  
Tube Test ◽  
Stator Blade ◽  
Transonic Turbine ◽  
Layered Thin Film

This paper reports the external convective heat transfer distribution of a modern single-stage transonic turbine together with the physical interpretation of the different shock interaction mechanisms. The measurements have been performed in the compression tube test rig of the von Karman Institute using single- and double-layered thin film gauges. The three pressure ratios tested are representative of those encountered in actual aeroengines, with M2,is ranging from 1.07 to 1.25 and a Reynolds number of about 106. Three different rotor blade heights (15%, 50%, and 85%) and the stator blade at midspan have been investigated. The measurements highlight the destabilizing effect of the vane left-running shock on the rotor boundary layer. The stator unsteady heat transfer is dominated by the fluctuating right-running vane trailing edge shock at the blade passing frequency.

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