A Physical Interpretation of Stagnation Pressure and Enthalpy Changes in Unsteady Flow

Hodson, H. P.; Hynes, T. P.; Greitzer, E. M.; Tan, C. S.

doi:10.1115/1.4007208

Cited by 11 publications

(6 citation statements)

References 15 publications

(26 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This effect, which is indicated by blue color and reverse arrowheads (lower right to upper left), is a typical phenomenon in multistage turbomachinery as a consequence of the rotorstator interaction. It was comprehensively studied by Hodson et al [27]. In the present case, the flow vectors clearly show an alternating relative flow angle β ′ .…”

Section: Phase-locked Flow Fieldsmentioning

confidence: 54%

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 1: Flow Field Investigations with Phase-Locked Particle Image Velocimetry

Schubert,

Kožulović,

Bitter

2024

Aerospace

View full text Add to dashboard Cite

Particle image velocimetry (PIV) measurements were performed inside a low-pressure turbine cascade operating at engine-relevant high-speed and low-Re conditions to investigate the near-endwall flow. Of particular research interest was the dominant periodic disturbance of the flow field by incoming wakes, which were generated by moving cylindrical bars at a frequency of 500 Hz. Two PIV setups were utilized to resolve both (1) a large blade-to-blade plane close to the endwall as well as midspan and (2) the wake effects in an axial flow field downstream of the blade passage. The measurements were performed using a phase-locked approach in order to align and compare the results with comprehensive CFD data that are also available for this test case. The experimental results not only support a better understanding and even a quantification of the wake-induced over/under-turning inside and downstream of the passage, they also enable the tracing of the `negative-jet-effect’, which is widely known in the CFD branch of the turbomachinery community but is seldom visualized in experiments. The results also reveal that the bar wake periodically widens the blade wake by up to 165%, while the secondary flow is less affected and exhibits a phase lag with respect to the 2D-flow effects. The results presented here are an essential basis for the subsequent investigation of the near-endwall blade suction surface effects using unsteady pressure-sensitive paint in the second part of this two-part publication.

show abstract

Section: Phase-locked Flow Fieldsmentioning

confidence: 54%

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 1: Flow Field Investigations with Phase-Locked Particle Image Velocimetry

Schubert,

Kožulović,

Bitter

2024

Aerospace

View full text Add to dashboard Cite

show abstract

“…In the present case, the source of the static pressure unsteadiness has to be found in the rotor pressure field travelling with the blade itself. As a result of the blade motion, the azimuthal gradients of pressure on the relative frame covert into static pressure unsteadiness according to the formula [25]:…”

Section: Discussion: Energy Separation Effectmentioning

confidence: 99%

Influence of the Rotor-Driven Perturbation on the Stator-Exit Flow within a High-Pressure Gas Turbine Stage

Gaetani¹,

Persico²

2021

IJTPP

View full text Add to dashboard Cite

In stator–rotor interaction studies on axial turbines, the attention is commonly focused on the unsteady rotor aerodynamics resulting from the periodic perturbations induced by the stator flow structures. Conversely, less interest has been historically attracted regarding the influence of the rotor on the flow released by the stator, correlated to propagation of the blade potential field upstream of the rotor leading edge. In this paper, experiments in the research high-pressure turbine of the Laboratory of Fluid-Machines of the Politecnico di Milano, performed by applying a fast-response aerodynamic pressure probe, alongside fully-3D time-accurate CFD simulations of the flow, are combined with the aim of discussing the rotor-to-stator interaction. While rotating, the rotor induces periodic perturbations on the pressure and velocity field in the stator–rotor gap, altering the evolution of the total quantities and the flow rate discharged by each stator channel and eventually triggering energy-separation effects which result in total pressure and total temperature oscillations in the stator-exit flow. Such oscillations were found to rise up to almost ±10% of the stage total temperature drop.

show abstract

“…The computable value of the ratio T se /T is defined as (20) The computable thermal creation term is given by…”

Section: Relationship To Pressure-based Lossmentioning

confidence: 99%

“…The interaction of incident wakes with the inter-blade pressure field has been discussed extensively in the context of turbomachinery [18][19][20] leading to description of the "wake recovery" phenomenon, by which certain measures of stagnation pressure loss are reduced. Wake recovery is due to the overall deceleration of the flow through the channel causing the speed differential between the incident wake and the free-stream fluid to reduce.…”

Section: Wake Recoverymentioning

confidence: 99%

Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

Leggett

Richardson

Priebe

et al. 2020

Journal of Turbomachinery

View full text Add to dashboard Cite

Loss analysis is a valuable technique for improving the thermodynamic performance of turbomachines. Analysing loss in terms of the ‘mechanical work potential’ (Miller, R.J., ASME Turbo Expo 2013, GT2013-95488) provides an instantaneous and local account of the thermal and aerodynamic mechanisms contributing to the loss of thermodynamic performance. This study develops the practical application of mechanical work potential loss analysis, providing the mathematical formulations necessary to perform loss analysis using practical Reynolds-Averaged Navier-Stokes (RANS) or Large Eddy Simulations (LES). The analysis approach is demonstrated using RANS and LES of a linear compressor cascade, both with and without incoming wakes. Spatial segmentation is used to attribute loss contributions to specific regions of the flow, and phase-averaging is performed in order to associate the variation of different loss contributions with the periodic passage of wakes through the cascade. For this un-cooled linear cascade, viscous dissipation is the dominant source of loss. The analysis shows that the contribution of the viscous reheat effect depends on the operating pressure of the compressor stage relative to the ambient ‘dead state’ pressure – implying that the optimal blade profile for a low-pressure compressor stage may be different from the optimal profile for a high-pressure compressor stage in the same engine, even if the operating conditions for both stages are dynamically-similar.

show abstract

A Physical Interpretation of Stagnation Pressure and Enthalpy Changes in Unsteady Flow

Cited by 11 publications

References 15 publications

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 1: Flow Field Investigations with Phase-Locked Particle Image Velocimetry

Characterization of the Endwall Flow in a Low-Pressure Turbine Cascade Perturbed by Periodically Incoming Wakes, Part 1: Flow Field Investigations with Phase-Locked Particle Image Velocimetry

Influence of the Rotor-Driven Perturbation on the Stator-Exit Flow within a High-Pressure Gas Turbine Stage

Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

Contact Info

Product

Resources

About