Unsteady Measurements of Periodic Effects in a Transonic Compressor With Casing Treatments

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Christoph Brandstetter ◽  
Fabian Wartzek ◽  
Jan Werner ◽  
Heinz-Peter Schiffer ◽  
Frank Heinichen
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Reference Case ◽  
Stall Inception ◽  
Operating Range ◽  
Transonic Compressor ◽  
High Pressure Compressor ◽  
Image Velocimetry ◽  
Blade Tip ◽  
Casing Treatments

Application of nonaxisymmetric casing treatments (CTs) can extend the operating range of a transonic compressor significantly. Recent CT designs have proven successful at achieving operating range extension without efficiency loss under design conditions. Two different CT designs were investigated on a high-speed one and a half stage test rig using extensive instrumentation. The stage setup is representative of the front stage of a modern high-pressure compressor. Results of particle image velocimetry (PIV) measurements taken in the blade tip region underneath the CT show a significantly modified flow structure compared to the smooth casing reference case. Blockage zone, secondary flow, and shock structures are affected by the CT, especially in highly throttled operating conditions. The stall inception process of the system with axial slots shows unexpected behavior, with modal activities that are not observed without CT. These activities are resolved using unsteady wall pressure (WP) and hot wire measurements.

Unsteady Measurements of Periodic Effects in a Transonic Compressor With Casing Treatments

2015 ◽  
Author(s):  
Christoph Brandstetter ◽  
Fabian Wartzek ◽  
Jan Werner ◽  
Heinz-Peter Schiffer ◽  
Frank Heinichen
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Reference Case ◽  
Stall Inception ◽  
Casing Treatment ◽  
Operating Range ◽  
Transonic Compressor ◽  
High Pressure Compressor ◽  
Blade Tip ◽  
Casing Treatments

Application of non-axisymmetric Casing Treatments (CTs) can extend the operating range of a transonic compressor significantly. Recent CT designs have proven successful at achieving operating range extension without efficiency loss under design conditions. Two different CT designs were investigated on a high-speed one and a half stage test rig using extensive instrumentation. The stage setup is representative of the front stage of a modern high-pressure compressor. Results of Particle Image Velocimetry (PIV) measurements taken in the blade tip region underneath the Casing Treatment show a significantly modified flow structure compared to the Smooth Casing reference case. Blockage zone, secondary flow and shock structures are affected by the CT, especially in highly throttled operating conditions. The stall inception process of the system with Axial Slots shows unexpected behavior, with modal activities that are not observed without CT. These activities are resolved using unsteady wall pressure and Hot Wire measurements.

scholarly journals Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments

1994 ◽  
Author(s):  
S. E. Gorrell ◽  
P. M. Russler
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Stall Inception ◽  
Casing Treatment ◽  
Low Aspect Ratio ◽  
Casing Treatments

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.

Modeling for the Development and Evaluation of Strategies for Controlling Flow Instabilities in Transonic Compressors

2007 ◽  
Author(s):  
John N. Chi
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
High Speed ◽  
Rotating Stall ◽  
Air Injection ◽  
Stall Inception ◽  
Operating Range ◽  
Transonic Compressor ◽  
Hot Air ◽  
Injection Model

A gas turbine engine consists of three primary components: a compressor, a combustion chamber, and a turbine. The operating range, performance, and reliability of gas turbine engines are limited by aerodynamic instabilities that occur in the compressor at low mass flow rates. Two of such compressor instabilities are rotating stall and surge. The stabilization of compression systems by means of active control has been demonstrated on several research compressors using different actuators such as inlet guide vanes, bleed valves, and air injection to manipulate the compressor flow field. This paper presents validated models of the steady and unsteady behaviors of air injection in high speed axial flow compressors that can be used for feasibility studies and control algorithm development. The steady air injection model consists of a control volume analysis coupled with wind tunnel measurements to characterize the changes in flow profiles entering the compressor and a streamline curvature analysis to model the response of the compressor blade rows to the different inlet span-wise profiles generated by the jet actuator. The steady air injection model was validated with experimentally measured span-wise profiles and compressor speed-lines, and then used to study the effect of hot air injection on the performance of a transonic compressor. The results show that injecting hot air into a transonic compressor has a potential increase in the operating range (i.e., decrease in the stalling mass flow rate) and a decrease in the total pressure rise across the transonic compressor. A modified theoretical stall inception model for high speed machines with air injection actuation is also presented. The compressible rotating stall inception model is a two-dimensional linearized stability model and pre-stall dynamics measurements from a single stage transonic compressor were used to validate the model. The compressible rotating stall inception model is an important tool that can be used for studying the effects of compressor design parameters on stability during compressor redesign, and for designing and evaluating feedback controllers.

scholarly journals The Influence of Carrier Air Preheating on Autoignition of Inline-Injected Hydrogen–Nitrogen Mixtures in Vitiated Air of High Temperature

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Christoph A. Schmalhofer ◽  
Peter Griebel ◽  
Manfred Aigner
Keyword(s):  
Hydrogen Content ◽  
Gas Turbines ◽  
High Speed ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Promoting Effect ◽  
Experimental Conditions ◽  
Lean Premixed Combustion ◽  
Image Velocimetry ◽  
Fuel Mixtures

The use of highly reactive hydrogen-rich fuels in lean premixed combustion systems strongly affects the operability of stationary gas turbines (GT) resulting in higher autoignition and flashback risks. The present study investigates the autoignition behavior and ignition kernel evolution of hydrogen–nitrogen fuel mixtures in an inline co-flow injector configuration at relevant reheat combustor operating conditions. High-speed luminosity and particle image velocimetry (PIV) measurements in an optically accessible reheat combustor are employed. Autoignition and flame stabilization limits strongly depend on temperatures of vitiated air and carrier preheating. Higher hydrogen content significantly promotes the formation and development of different types of autoignition kernels: More autoignition kernels evolve with higher hydrogen content showing the promoting effect of equivalence ratio on local ignition events. Autoignition kernels develop downstream a certain distance from the injector, indicating the influence of ignition delay on kernel development. The development of autoignition kernels is linked to the shear layer development derived from global experimental conditions.

A Comparison of Turbulence Levels From Particle Image Velocimetry and Constant Temperature Anemometry Downstream of a Low-Pressure Turbine Cascade at High-Speed Flow Conditions

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Particle Image Velocimetry ◽  
Constant Temperature ◽  
High Speed ◽  
Particle Image ◽  
Low Pressure ◽  
Operating Conditions ◽  
Stereoscopic Particle Image Velocimetry ◽  
Turbine Cascade ◽  
Low Pressure Turbine ◽  
Image Velocimetry

Abstract The development and verification of new turbulence models for Reynolds-averaged Navier–Stokes (RANS) equation-based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high-speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique are given. The presented time mean fields as well as total turbulence data demonstrate with an average deviation of ΔTu<0.4% and ΔC/Cref<0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.

PIV Measurements in Diffuser of the Radial Pump

2015 ◽  
Author(s):  
Sung Yong Jung ◽  
Young Uk Min ◽  
Kyung Lok Lee
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Internal Flows ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Acquisition Device ◽  
Field Information ◽  
Radial Pump

The performance characteristics of the radial pump commonly used as a multistage (8 or 10 stage) pump have been investigated experimentally. Due to the complex three-dimensional geometries, the hydraulic performance of multistage pumps is closely related to the internal flows in diffuser and return vanes. In order to investigate the flow characteristics in these regions by Particle Image Velocimetry (PIV) technique, a transparent pump is designed. A 532 nm continuous laser and a high-speed camera are used as a light source and an image acquisition device, respectively. The velocity field information in a diffuser of the radial pump is successfully obtained by two-dimensional PIV measurements at various operating conditions.

Experimental Investigation on the Effect of Porosity of Bend Skewed Casing Treatment on a Single Stage Transonic Axial Flow Compressor

2014 ◽  
Author(s):  
Dilipkumar B. Alone ◽  
Subramani Satish Kumar ◽  
Shobhavathy Thimmaiah ◽  
Janaki Rami Reddy Mudipalli ◽  
A. M. Pradeep ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Axial Flow ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Operating Range ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Stable Operating ◽  
Flow Compressor ◽  
Casing Treatments

A bend skewed casing treatment was designed, to study the influence of one of its geometrical parameter porosity on the stable performance of single stage transonic axial flow compressor. The compressor was designed for the stage total-to-total pressure ratio of 1.35, corrected mass flow rate of 22 kg/s at corrected design speed of 12930 RPM. Bend skewed casing treatment has an axial inlet segment till 50% of the total length and rear segment that is skewed by 45° in the direction of the rotor tip section stagger. Both the sections were oriented at a skew angle of 45° to the radial plane such that the flow exiting the slot is in counter-clockwise direction to that of the rotor direction. The casing treatment slot width was equal to the maximum thickness of the rotor blades. Three casing treatment configurations were identified for the current experimental investigation. All the treatment geometries considered for the experimental research have lower porosities than reported in the open literatures. The effect of the porosity parameter on the performance of transonic compressor stage was evaluated at two axial coverages of 20% and 40% relative to the rotor tip axial chord. Performance maps were obtained for the solid casing and casing treatment with three different porosities. Comparative studies were carried out and experimental results showed a maximum of 65% improvement in the stable operating range of the compressor for one of the treatment configurations. It was also observed that the stable operating range of the compressor increases with an increase in the casing treatment porosity. All the casing treatment configurations showed that the compressor stall occurs at lower mass flows as compared to the solid casing. Compressor stage peak efficiency shows significant degradations with increase in the porosity as compared to solid casing. Detailed blade element performances were also obtained using calibrated multi-hole aerodynamic probe. Comparative variations of flow parameters like absolute flow angle, Mach number were studied at full flow and near stall conditions for the solid casing and casing treatment configurations. Hot wire measurements show very high fluctuation in the inlet axial velocity in the presence of solid casing as compared to casing treatments. Experimental investigation revealed that the porosity of the casing treatments has strong influence on the transonic compressor stage performance.

1997 Best Paper Award—Turbomachinery Committee: A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1998 ◽  
Vol 120 (3) ◽  
pp. 393-401 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Short Length ◽  
Operating Conditions ◽  
Length Scale ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms in a low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short length-scale disturbance known as a “spike,” and the second with a longer length-scale disturbance known as a “modal oscillation.” In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented that relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: Long length-scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed that explains the type of stall inception pattern observed in a particular compressor. Measurements from a single-stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

scholarly journals Inter-plume aerodynamics for gasoline spray collapse

2017 ◽  
Vol 19 (10) ◽  
pp. 1048-1067 ◽  
Author(s):  
Panos Sphicas ◽  
Lyle M Pickett ◽  
Scott A Skeen ◽  
Jonathan H Frank
Keyword(s):  
Ambient Temperature ◽  
High Speed ◽  
Direct Injection ◽  
Engine Performance ◽  
Operating Conditions ◽  
Momentum Exchange ◽  
Flow Recirculation ◽  
Plume Region ◽  
Image Velocimetry ◽  
Air Mixing

The collapse or merging of individual plumes of direct-injection gasoline injectors is of fundamental importance to engine performance because of its impact on fuel–air mixing. However, the mechanisms of spray collapse are not fully understood and are difficult to predict. The purpose of this work is to study the aerodynamics in the inter-spray region, which can potentially lead to plume collapse. High-speed (100 kHz) particle image velocimetry is applied along a plane between plumes to observe the full temporal evolution of plume interaction and potential collapse, resolved for individual injection events. Supporting information along a line of sight is obtained using simultaneous diffused back illumination and Mie-scatter techniques. Experiments are performed under simulated engine conditions using a symmetric eight-hole injector in a high-temperature, high-pressure vessel at the “Spray G” operating conditions of the engine combustion network. Indicators of plume interaction and collapse include changes in counter-flow recirculation of ambient gas toward the injector along the axis of the injector or in the inter-plume region between plumes. The effect of ambient temperature and gas density on the inter-plume aerodynamics and the subsequent plume collapse are assessed. Increasing ambient temperature or density, with enhanced vaporization and momentum exchange, accelerates the plume interaction. Plume direction progressively shifts toward the injector axis with time, demonstrating that the plume interaction and collapse are inherently transient.

A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1997 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Stability Criteria ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms a in low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short lengthscale disturbance known as a ‘spike’, and the second with a longer lengthscale disturbance known as a ‘modal oscillation’. In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented which relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: long lengthscale disturbances are related to a two-dimensional instability of the whole compression system, while short lengthscale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed which explains the type of stall inception pattern observed in a particular compressor. Measurements from a single stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

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