Transport of Entropy Waves Within a HP Turbine Stage

Volume 2A: Turbomachinery ◽

10.1115/gt2018-76459 ◽

2018 ◽

Author(s):

Paolo Gaetani ◽

Giacomo Persico

Keyword(s):

Experimental Study ◽

High Pressure ◽

Gas Turbine ◽

Main Flow ◽

Streamwise Direction ◽

Turbine Stage ◽

Time Resolved ◽

Blade Row ◽

Stator Blade ◽

The Waves

This paper presents the results of an experimental study on the transport of entropy waves, representative of those generated by gas turbine burners, within an un-cooled high-pressure gas turbine stage. The prescribed entropy waves were injected in streamwise direction featuring a 7% over-temperature with respect to the main flow at the stage inlet, with a frequency of 30 Hz. The entropy waves are injected in four different circumferential positions with respect to the stator blade. Detailed time-resolved temperature measurements as well as aerodynamic measurements upstream and downstream of the blade rows were performed. Measurements showed a relevant attenuation of the entropy waves throughout their transport within the stator blade row. The temperature distribution resulted in a severe alteration depending on the injection position. Downstream of the rotor, the waves spread over the pitch above midspan and are more concentrated at the hub. Finally, a comparison with measurements performed with conventional steady hot streaks is also reported, remarking both differences and affinities. As a relevant conclusion, it is experimentally shown that entropy waves can be proficiently simulated by considering a number of hot streaks of different amplitude.

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Comparison of 3D Unsteady Transient Conjugate Heat Transfer Analysis on a High Pressure Cooled Turbine Stage With Experimental Data

Volume 5A: Heat Transfer ◽

10.1115/gt2017-64596 ◽

2017 ◽

Author(s):

Jong-Shang Liu ◽

Mark C. Morris ◽

Malak F. Malak ◽

Randall M. Mathison ◽

Michael G. Dunn

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Heat Flux ◽

High Pressure ◽

High Temperature ◽

Gas Turbine ◽

Conjugate Heat Transfer ◽

Turbine Rotor ◽

Turbine Stage ◽

Cooling Flow

In order to have higher power to weight ratio and higher efficiency gas turbine engines, turbine inlet temperatures continue to rise. State-of-the-art turbine inlet temperatures now exceed the turbine rotor material capability. Accordingly, one of the best methods to protect turbine airfoil surfaces is to use film cooling on the airfoil external surfaces. In general, sizable amounts of expensive cooling flow delivered from the core compressor are used to cool the high temperature surfaces. That sizable cooling flow, on the order of 20% of the compressor core flow, adversely impacts the overall engine performance and hence the engine power density. With better understanding of the cooling flow and accurate prediction of the heat transfer distribution on airfoil surfaces, heat transfer designers can have a more efficient design to reduce the cooling flow needed for high temperature components and improve turbine efficiency. This in turn lowers the overall specific fuel consumption (SFC) for the engine. Accurate prediction of rotor metal temperature is also critical for calculations of cyclic thermal stress, oxidation, and component life. The utilization of three-dimensional computational fluid dynamics (3D CFD) codes for turbomachinery aerodynamic design and analysis is now a routine practice in the gas turbine industry. The accurate heat-transfer and metal-temperature prediction capability of any CFD code, however, remains challenging. This difficulty is primarily due to the complex flow environment of the high-pressure turbine, which features high speed rotating flow, coupling of internal and external unsteady flows, and film-cooled, heat transfer enhancement schemes. In this study, conjugate heat transfer (CHT) simulations are performed on a high-pressure cooled turbine stage, and the heat flux results at mid span are compared to experimental data obtained at The Ohio State University Gas Turbine Laboratory (OSUGTL). Due to the large difference in time scales between fluid and solid, the fluid domain is simulated as steady state while the solid domain is simulated as transient in CHT simulation. This paper compares the unsteady and transient results of the heat flux on a high-pressure cooled turbine rotor with measurements obtained at OSUGTL.

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Comparison of Steady and Unsteady Coupled Heat-Transfer Simulations of a High-Pressure Turbine Blade

Volume 5A: Heat Transfer ◽

10.1115/gt2015-43175 ◽

2015 ◽

Author(s):

Markus Schmidt ◽

Christoph Starke

Keyword(s):

Heat Transfer ◽

High Pressure ◽

Steady State ◽

Flow Field ◽

Film Cooling ◽

Strong Increase ◽

Pressure Side ◽

Turbine Stage ◽

High Pressure Turbine ◽

Time Resolved

This article presents results for the coupled simulation of a high-pressure turbine stage in consideration of unsteady hot gas flows. A semi-unsteady coupling process was developed to solve the conjugate heat transfer problem for turbine components of gas turbines. Time-resolved CFD simulations are coupled to a finite element solver for the steady state heat conduction inside of the blade material. A simplified turbine stage geometry is investigated in this paper to describe the influence of the unsteady flow field onto the time-averaged heat transfer. Comparisons of the time-resolved results to steady state results indicate the importance of a coupled simulation and the consideration of the time-dependent flow-field. Different film-cooling configurations for the turbine NGV are considered, resulting in different temperature and pressure deficits in the vane wake. Their contribution to non-linear effects causing the time-averaged heat load to differ from a steady result is discussed to further highlight the necessity of unsteady design methods for future turbine developments. A strong increase in the pressure side heat transfer coefficients for unsteady simulations is observed in all results. For higher film-cooling mass flows in the upstream row, the preferential migration of hot fluid towards the pressure side of a turbine blade is amplified as well, which leads to a strong increase in material temperature at the pressure side and also in the blade tip region.

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Vortex-Wake-Blade Interaction in a Shrouded Axial Turbine

Journal of Turbomachinery ◽

10.1115/1.1934263 ◽

2005 ◽

Vol 127 (4) ◽

pp. 699-707 ◽

Cited By ~ 25

Author(s):

J. Schlienger ◽

A. I. Kalfas ◽

R. S. Abhari

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Surprising Result ◽

Rotor Wake ◽

Time Resolved ◽

Axial Turbine ◽

Passage Vortex ◽

Blade Row ◽

Stator Blade ◽

Secondary Flow Field

This paper presents time-resolved flow field measurements at the exit of the first rotor blade row of a two stage shrouded axial turbine. The observed unsteady interaction mechanism between the secondary flow vortices, the rotor wake and the adjacent blading at the exit plane of the first turbine stage is of prime interest and analyzed in detail. The results indicate that the unsteady secondary flows are primarily dominated by the rotor hub passage vortex and the shed secondary flow field from the upstream stator blade row. The analysis of the results revealed a roll-up mechanism of the rotor wake layer into the rotor indigenous passage vortex close to the hub endwall. This interesting mechanism is described in a flow schematic within this paper. In a second measurement campaign the first stator blade row is clocked by half a blade pitch relative to the second stator in order to shift the relative position of both stator indigenous secondary flow fields. The comparison of the time-resolved data for both clocking cases showed a surprising result. The steady flow profiles for both cases are nearly identical. The analysis of the probe pressure signal indicates a high level of unsteadiness that is due to the periodic occurrence of the shed first stator secondary flow field.

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The Development of Turbine Exit Flow in a Swan-Necked Inter-Stage Diffuser

Volume 6: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38174 ◽

2003 ◽

Cited By ~ 15

Author(s):

R. J. Miller ◽

R. W. Moss ◽

R. W. Ainsworth ◽

N. W. Harvey

Keyword(s):

High Pressure ◽

Secondary Flow ◽

Leakage Flow ◽

Turbine Stage ◽

Tip Leakage Flow ◽

Trailing Edge ◽

Inlet Flow ◽

Time Resolved ◽

Tip Leakage ◽

Numerical Predictions

This paper describes both the migration and dissipation of flow phenomena downstream of a transonic high-pressure turbine stage. The geometry of the HP stage exit duct considered is a swan-necked diffuser similar to those likely to be used in future engine designs. The paper contains results both from an experimental programme in a turbine test facility and from numerical predictions. Experimental data was acquired using three fast-response aerodynamic probes capable of measuring Mach number, whirl angle, pitch angle, total pressure and static pressure. The probes were used to make time-resolved area traverses at two axial locations downstream of the rotor trailing edge. A 3D time-unsteady viscous Navier-Stokes solver was used for the numerical predictions. The unsteady exit flow from a turbine stage is formed from rotor-dependent phenomena (such as the rotor wake, the rotor trailing edge recompression shock, the tip-leakage flow and the hub secondary flow) and vane-rotor interaction dependant phenomena. This paper describes the time-resolved behaviour and three-dimensional migration paths of both of these phenomena as they convect downstream. It is shown that the inlet flow to a downstream vane is dominated by two corotating vortices, the first caused by the rotor tip-leakage flow and the second by the rotor hub secondary flow. At the inlet plane of the downstream vane the wake is extremely weak and the radial pressure gradient is shown to have caused the majority of the high loss wake fluid to be located between the mid-height of the passage and the casing wall. The structure of the flow indicates that between a high pressure stage and a downstream vane simple two-dimensional blade row interaction does not occur. The results presented in this paper indicate that the presence of an upstream stage is likely to significantly alter the structure of the secondary flow within a downstream vane. The paper also shows that vane-rotor interaction within the upstream stage causes a 10° circumferential variation in the inlet flow angle of the 2nd stage vane.

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Experimental Study on High Pressure Combustion of Decomposed Ammonia: How Can Ammonia Be Best Used in a Gas Turbine?

10.1115/gt2021-60057 ◽

2021 ◽

Author(s):

Mario Ditaranto ◽

Inge Saanum ◽

Jenny Larfeldt

Keyword(s):

Experimental Study ◽

High Pressure ◽

Gas Turbine ◽

Gas Turbines ◽

Favourable Effect ◽

Small Scale ◽

Nox Formation ◽

Fuel Blends ◽

Combustion Properties ◽

Fuel Mixtures

Abstract Hydrogen, a carbon-free fuel, is a challenging gas to transport and store, but that can be solved by producing ammonia, a worldwide commonly distributed chemical. Ideally, ammonia should be used directly on site as a fuel, but it has many combustion shortcomings, with a very low reactivity and a high propensity to generate NOx. Alternatively, ammonia could be decomposed back to a mixture of hydrogen and nitrogen which has better combustion properties, but at the expense of an endothermal reaction. Between these two options, a trade off could be a partial decomposition where the end use fuel is a mixture of ammonia, hydrogen, and nitrogen. We present an experimental study aiming at finding optimal NH3-H2-N2 fuel blends to be used in gas turbines and provide manufacturers with guidelines for their use in retrofit and new combustion applications. The industrial burner considered in this study is a small-scale Siemens burner used in the SGT-750 gas turbine, tested in the SINTEF high pressure combustion facility. The overall behaviour of the burner in terms of stability and emissions is characterized as a function of fuel mixtures corresponding to partial and full decomposition of ammonia. It is found that when ammonia is present in the fuel, the NOx emissions although high can be limited if the primary flame zone is operated fuel rich. Increasing pressure has shown to have a strong and favourable effect on NOx formation. When ammonia is fully decomposed to 75% H2 and 25% N2, the opposite behaviour is observed. In conclusion, either low rate or full decomposition are found to be the better options.

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Three-Dimensional Time-Resolved Flow Field in the First and Last Turbine Stage of a Heavy Duty Gas Turbine: Part I — Secondary Flow Field

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery ◽

10.1115/2000-gt-0438 ◽

2000 ◽

Cited By ~ 1

Author(s):

Martin von Hoyningen-Huene ◽

Wolfram Frank ◽

Alexander R. Jung

Keyword(s):

Flow Field ◽

Secondary Flow ◽

Gas Turbine ◽

Gas Turbines ◽

Companion Paper ◽

Heavy Duty ◽

Turbine Stage ◽

Time Resolved ◽

Heavy Duty Gas Turbine ◽

Secondary Flow Field

Unsteady stator-rotor interaction in gas turbines has been investigated both experimentally and numerically for some years now. Even though the numerical methods are still in development, today they have reached a certain degree of maturity allowing industry to focus on the results of the computations and their impact on turbine design, rather than on a further improvement of the methods themselves. The key to increase efficiency in modern gas turbines is a better understanding and subsequent optimization of the loss-generation mechanisms. A major part of these are the secondary losses. To this end, this paper presents the time-resolved secondary flow field for the two test cases computed, viz the first and the last turbine stage of a modern heavy duty gas turbine. A companion paper referring to the same computations focuses on the unsteady pressure fluctuations on vanes and blades. The investigations have been performed with the flow solver ITSM3D which allows for efficient calculations that simulate the real blade count ratio. This is a prerequisite to simulate the unsteady phenomena in frequency and amplitude properly.

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Fourier Decomposed Turbulence Measurements Downstream of a High-Pressure Turbine Stage

Volume 2: Fora ◽

10.1115/fedsm2008-55146 ◽

2008 ◽

Cited By ~ 1

Author(s):

Lars-Uno Axelsson ◽

William K. George ◽

T. Gunnar Johansson

Keyword(s):

High Pressure ◽

Periodic Component ◽

Turbine Stage ◽

High Pressure Turbine ◽

Time Resolved ◽

Velocity Fluctuations ◽

Axial Turbine ◽

Blade Passage ◽

Turbulence Measurements ◽

Time Resolved Measurements

This forum paper discusses phase-resolved turbulence measurements of the flow downstream of an axial turbine, and especially how phase-resolved measurements compare to time-resolved measurements. The time-resolved spectra produced higher velocity fluctuations than the corresponding phase-resolved spectra even when the periodic component was filtered out from the time-resolved measurements. The phase-resolved spectrum effectively removes all the peaks in the spectrum except for the ones associated with the blade-passage frequency.

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Numerical Investigations on the Aerodynamic Performance of Turbine Stage and Rotordynamic Characteristics of Stator Seal With Consideration of Supplementary Steam

Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines ◽

10.1115/gt2015-42549 ◽

2015 ◽

Cited By ~ 1

Author(s):

Zhigang Li ◽

Jun Li ◽

Shizhu Wang ◽

Dawei Ji ◽

Gaohui Xiao ◽

...

Keyword(s):

High Pressure ◽

Flow Field ◽

Labyrinth Seal ◽

Aerodynamic Performance ◽

High Pressure Cylinder ◽

Turbine Stage ◽

Boundary Flow ◽

Rotordynamic Coefficients ◽

Pressure Cylinder ◽

Stator Blade

The supplementary steam structure is used in the high pressure cylinder to increase the power output of steam turbine through increase the mass flow rate. In this work, the supplementary steam structure installed between the fifth and sixth stage of the high pressure cylinder of steam turbine is taken as the research object. The flow field and aerodynamic performance of the fifth and sixth stage was numerically investigated at different supplement steam rates using the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and k–ε turbulent model solutions. The inlet/outlet boundary flow conditions of the stator labyrinth seal of the sixth stage was determined based on the steady computations at three different supplementary steam rates. The unsteady flow field and rotordynamic coefficients of the stator labyrinth seal were calculated using the multi-frequency elliptical whirling orbit model and dynamic grid technique based on the unsteady RANS solutions. The numerical results show that the supplementary steam jet impacts on the hub regions of the stator blade of the sixth stage and results in the vortex flow. This flow behavior leads to the non-uniform inlet aerodynamic parameters at the entrance of the stator blade of the sixth stage. The aerodynamic performance decreases with the increase of the supplementary steam rates. The supplementary steam jet changes the inlet preswirl and boundary flow condition of the stator labyrinth seal of the sixth stage. The fluid excitation rotordynamic coefficients of the stator labyrinth seal would change due to the variation of the boundary flow condition. The detailed flow pattern of the turbine stage and variation of the rotordynamic coefficients of the stator labyrinth seal at different supplementary steam rates were also illustrated and discussed.

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