bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbine Rear Frame Interface – Thermal Modelling Improvement Using CFD Based Approach
Authors: Soundiramourty Sendilkumaran , Tippireddy Vishnu Vardhan Reddy , Cubeda Simone
Published: August 2024

In the power generation world, Aero-derivative Gas Turbines plays an important role due to their inherent efficiency and Power to Weight advantage. There is a heavy competition among the manufacturers to capture the market with their best products. Baker Hughes has many products in this segment with a range of output levels.

The Gas Turbine Rear Frame (TRF) is a structural member, which supports the Gas Turbine casings at the rear end and transfers the load to the base plate or ground. It also houses the last bearing on which the power turbine rotor is supported. Also, this component experiences hot gases on the mainstream side and relatively colder air on the cooling path. It has many non axi-symmetric features which makes the design of this component very challenging.

This paper describes the approach used to improve the thermal prediction of the TRF, Rotor Aft Wheel Cavity and vent air cavity region, which is critical to understand the mechanical behavior of the component and assess the component life. Quasi-3D flow analysis is used to understand the flow structures in the cavities and simulated those flow structures in the 2D thermal models which improved the model prediction, and which is also validated with test data.
Unsteady Flow Mechanism of Impeller Stall Inception in a High-Pressure Ratio Centrifugal Compressor With Bleed Slots
Authors: Fujisawa Nobumichi , Yamamoto Yuta , Ohta Yutaka , Ogino Atsushi , Nakayama Ryo , Kitamura Eijiro
Published: August 2024

The impeller stall inception in a high-pressure ratio centrifugal compressor with bleed slots was investigated by the experiments and unsteady numerical analysis. This study reported that the flow instability of the internal flow was first initiated around the leading edge of the splitter blades and finally resulted in tip-leakage flow instability at the leading edge of the main blades. The impeller stall consisted of a stall cell and rotated about 70% of the impeller rotational speed. Furthermore, a pressure disturbance occurs at the splitter blade leading edge before the main blade leading edge. The blockage within the passage of the suction side at the leading edge of the splitter blade was first increased because the leading-edge separation on the suction surface of the splitter blade was enlarged. The blockage within the passage of the pressure side was increased after that of the suction side stopped increasing. Therefore, the blockage development of both pressure and suction passage at the leading edge of the splitter blade was the main cause of the stall inception. Then, a longitudinal vortex was formed near the bleed slots and blocked the mainstream near tip side. Subsequently, the reverse flow region in the inducer was developed and extended to the impeller inlet. Finally, the flow angle to the main blade increased, the spillage occurred at a leading edge of a main blade, and the rotating stall was generated. The cause of impeller instability was the separation of the suction surface of splitter blade and the formation of a stagnation region on the pressure surface at the splitter leading edge.
100% H2 DLE Gas Turbine Combustion Technology Platform Development
Authors: Hermeth Sebastian , Panek Lukasz , Witzel Benjamin , Grandt Christopher , Koestlin Berthold , Wanjura Stefan , Teuber Hannes , Parsania Nishant , Sadasivuni Suresh , Bulat Ghenadie , Yilmaz Ertan , Koenig Mike
Published: August 2024

Siemens Energy is developing the required technologies to operate its gas turbines up to 100% H2 by 2030 to support the target of limiting global warming to 1.5 degrees Celsius. A focused effort has been undertaken to develop a combustion system technology platform for the complete Siemens Energy gas turbine portfolio which will enable gas turbine operation across the entire range of H2/natural gas blends within emissions compliance and hardware integrity.

This paper presents an update of Siemens Energy’s 100% Hydrogen DLE Gas Turbine Combustion Technology Platform Development presented at the 2022 ASME Turbo Expo [20]. While the 2022 paper showed initial rig test results at scaled pressure, the update includes new results from rig testing at full pressure, a summary of results from SGT-400 full engine tests conducted on natural gas at the Siemens Energy factory in Lincoln (UK), and SGT-400 full engine tests with various levels of hydrogen up to 100% at a customer site in Saillat-Sur-Vienne (France) as part of the HYFLEXPOWER project. An engine safe operation envelope with respect to flashback will be presented and engine data will be compared against rig test data obtained at Clean Energy Center at relevant engine conditions. Siemens Energy actively researches and develops methods to investigate hydrogen embrittlement effects in metallic materials, particularly those applied in gas turbines. Through extensive testing of base materials and their joint connections, Siemens Energy aims to improve understanding of hydrogen’s effects on materials and optimize gas turbine components’ lifespan. The current state of development in this regard is presented here. Finally, the paper will provide an outlook on the scaling of the demonstrated hydrogen technology to Siemens Energy’s gas turbine portfolio.
Steam Whirl Detection and Correction in 135 MW Steam Turbine
Authors: Chumai Roengchai , Lertsongkram Pisut , Koondilogpiboon Nuntaphong
Published: August 2024

Steam whirl is the self-excited vibration that causes the rotor of a steam turbine to whirl at its first critical speed. It is caused by the combination of steam excitation (in blade rows and steam glands) and low damping of the journal bearings. Steam whirl usually occurs in the high-pressure rotor at high power output where the steam pressure and flow rate are high. The occurrence of the steam whirl prevents maximum power operation. The steam whirl can be rectified by bearing/seal modifications.

A case study was presented on the remote startup support service for a 135 MW steam turbine and generator after a major overhaul. The vibration amplitudes measured at high-intermediate pressure (HP/IP) rotor fluctuated due to subsynchronous vibration frequency when the unit was operated at over 103 MW. Furthermore, the amplitudes significantly increased as the load was further increased and the unit tripped at 134 MW due to the excessive vibration amplitudes at bearing 2. The unit was then restarted and the maximum output was limited to around 103 MW until the following outage where both bearings of the rotor were replaced with the tighter clearance ones and the alignment between bearing 1 and the main oil pump was done. The subsequent startup showed acceptable and stable vibration amplitudes of the HP/IP rotor during baseload operation.
Model-Driven Optimization for the Conceptual Design of Aeroengine Turbine Flow Path
Authors: Chen Yifan , Chen Jinwei , Zhang Huisheng
Published: August 2024

In the conceptual design process of aeroengines, the thermal parameters and the fundamental structure must be determined. To reduce iterative adjustments between the conceptual and detailed design, it is necessary to obtain a method that can meet the performance requirements quickly and accurately. At the same time, considering the different methods of subject-level modeling, a tool is needed to support the data interaction of the analysis model. Therefore, an optimization approach combining multidisciplinary design optimization (MDO) and model-based systems engineering (MBSE) is proposed for conceptual design. Taking turbine flow path as the research object, a MBSE-MDO framework for overall design is proposed. First, a Requirements, Functional, Logical, Physical (RFLP) modeling procedure is applied in this study to implement the entire design process from requirements to system architecture. Based on semantic modeling technology, the automatic transformation of the knowledge representation of the model is realized. Then, relying on the consistency and scalability provided by semantic modeling, MDO is performed. With fuel consumption, weight, and noise as the system-level optimization objectives, aerodynamics, heat, and structural strength are considered as disciplinary constraints. The main cycle parameters for specific scenarios and requirements are obtained. Finally, validation at the early stage of the design is performed to ensure that the design meets the defined requirements. The accuracy of the overall design results is verified based on the existing engine data. The average error of the design parameters is 1.55% and the maximum error is 3.02%. It indicates that the design method proposed in the paper meets the accuracy requirements for engine-related parameters in the overall design phase. The method proposed in this study is expected to rapidly and accurately obtain design parameters that meet the performance requirements, thereby reducing the development cycle of the turbine flow path. Based on the optimization of turbine flow path in this paper, the optimization design of other components can be further carried out to realize the overall optimization, laying a technical foundation for the overall multidisciplinary optimization design.
Numerical Implementation of Electrostatic Solver Within OpenFOAM for GT Intake Filtration
Authors: Pinelli Michele , Piovan Mattia , Suman Alessio , Zanini Nicola , Rossin Stefano , Minotti Stefano
Published: August 2024

Gas turbines require filtered air to preserve operability, availability, and efficiency. Fouling, corrosion, and erosion severely affect the performance of the axial compressor and it can be in part prevented by filtering the air intake. For this reason, several stages of filters can be used in series to catch pollutant particles gradually smaller and with a high level of capturing efficiency. Traditionally, the separation is obtained using cartridges of porous material, which provide a high level of filtration but at the same time generate a pressure drop increasing over time. Another common type of filter is the inertial one, whose operating principle is based on the inertial force acting on the solid particles to separate them from the mainstream. The capturing efficiency of the inertial filter is not comparable with the porous one and for this reason, it is used upstream as a pre-filter. In recent years, another technique has been developed to filter air flows thanks to an electrostatic field, that is induced inside the flow. The electrostatic force generated is able to attract and separate metallic particles. In the present work, numerical investigations are carried out to simulate the effect of the electrostatic force for gas turbine filtering systems. The CFD tool used is OpenFOAM, whose official release can simulate inertial and porous filtering media, while for electrostatic one is not possible due to the absence of a library able to simulate the electrostatic force that acts on the discrete phase. A new library was developed in order to calculate: the electric field, the electric potential, and the charge density of the continuous phase. Simulation results show how the calculation of these quantities allows us to predict the electrostatic force acting on particle flows in the presence of electrostatic fields.
Predicting Gas Turbine Power Output in Single Shaft Combined Cycle Power Plants: A Physics-Based and Data Analytics Approach
Authors: Nandagopal Pugalenthi , More Manjunath , Sharma Kirti , Saroj Uttam , Singh Gurdev
Published: August 2024

The measurement of gas turbine power output is essential for original equipment manufacturers (OEMs) and plant operators to evaluate the performance of their gas turbines. Accurate knowledge of the power output allows for better gas turbine control based on customer requirements. By measuring the GT power, OEMs can predict critical internal performance parameters such as turbine inlet temperature, compressor inlet flow, compressor efficiency, and turbine efficiency. Furthermore, accurate prediction of steam turbine efficiency can also be achieved using a mass and energy balance approach. In a multi-shaft combined cycle power plant, gas and steam turbine power are measured separately, enabling analysis of the heat and mass balance approach within individual turbine boundaries. However, in a single-shaft combined cycle power plant, only the total cycle power is measured, making it difficult to predict gas turbine and steam turbine power output separately. Accurate gas turbine power output prediction is critical to prevent improper gas turbine operation, such as over-firing or under-firing. Over-firing the gas turbine can damage the hot gas path life of the turbine while under-firing can result in a loss of gas turbine power.

Additionally, accurate power output prediction enables OEMs to provide precise performance guarantees, reducing the risk of paying liquidity damages. To validate the single-shaft approach for predicting gas turbine power output, data from a multi-shaft combined cycle power plant was used, and accurate gas turbine power output was predicted and compared with the power observed using multiple-shaft gas turbine power.

The first approach of the paper is solely founded on the principles of the first law of thermodynamics. The objective is to validate this first law approach using only a limited data set from a multishift combined cycle power plant, such as compressor inlet temperature, fuel flow, fuel lower heating value, combined cycle power output, and gas turbine power output.

The other methods are Hybrid modeling approach and Data driven approach. In the hybrid method a model has been obtained using mass and energy balance equation and the real gas turbine data is used to obtain the values of unknown parameters in the hybrid model. In the Data driven approach, real gas turbine’s data is used to obtain a black box model. Hybrid models are generally regarded as superior to data-driven models in terms of accuracy because they combine the use of physics-based principles and data. Data-driven approaches, on the other hand, offer a simpler way to model plants or processes as they do not rely on prior knowledge of the system and can be developed solely using process data.
Tuning of an Algebraic Model for Separated Flows by Means of Bayesian Lasso
Authors: Carlucci Andrea , Petronio Daniele , Barsi Dario , Dellacasagrande Matteo , Simoni Daniele
Published: August 2024

In this work, machine learning techniques are exploited to train a new model based on Pope’s tensorial bases, where the common definition of the turbulent viscosity is extended to define the Reynolds stress tensor as an expansion of strain-rate and rotation tensors. Specifically, a Sparse Bayesian approach has been implemented to provide new expressions for the turbulent eddy viscosities appearing in the Pope’s formulation. An experimental dataset acquired with Time-Resolved Particle Image Velocimetry has been used to tune the present model. Data provide the mean flow and the Reynolds stress distributions of different separation bubbles evolving on a flat plate with applied variable adverse pressure gradients, reproducing in some extent the diffusion that characterize the rear suction side of turbine blades. The model has been tuned with different independent conditions of flow Reynolds number and free-stream turbulence intensity. Then, two additional flow conditions have been adopted to cross-validate and test the generated model. The adoption of the Sparse Bayesian approach allows the direct identification of the leading predictors, i.e., flow features, exploiting the main characteristics of the transition scenario (here, the transition process induced by flow separation). Specifically, the correlations here tuned may contribute to improve the capability of RANS solvers in the prediction of transitional flows.
Operation of the Atmospheric Biomass-Fired Topcycle – BTC – “Fuel to Flame” Test Rig
Authors: Hannappel Jan-Peter , Güthe Felix , Alemela Reddy Panduranga , Saldarriaga David , Borg Gustaf , Jofs Martin , Bartlett Michael
Published: August 2024

After the international climate conference (COP28) agreed recently on fossil fuel phase-out, the search for alternative energy sources is further increased worldwide with a focus not only on electricity but also renewable fuels for dispatchable energy production. This decarbonisation challenges existing technology and calls for alternative fuels of synthetic or biogenic origin. Phoenix BioPower is developing a high-efficiency process, called the Biomass-fired TopCycle (BTC), to address this market using forestry and agricultural residues for electricity production. In the BTC, a biomass-fed gasifier produces a hot and pressurized syngas which is subsequently cooled by steam addition prior to clean-up. This highly diluted, steam-rich fuel is combusted in a TopCycle gas turbine resulting in high electric efficiencies. The Phoenix Advanced Combustion System (PACS), which utilizes high steam content and large recirculation zone for stability and flexibility (MILD -Moderate or Intense Low oxygen Dilution), has demonstrated high fuel-flexibility, i.e. hydrogen, syngas or methane, and high load flexibility.

To demonstrate the technology, an atmospheric “fuel to flame” test rig has been constructed and is operated to optimize combustion performance and system integration, regarding operational stability and flexibility. We present the first results using the biomass gasifier product gas as fuel for the PACS combustion system at high steam ratios and co-firing with hydrogen. Challenges lie in the stability of the system and combustor at transient conditions, for weakfuels, as well as with NOx emissions, which arise mostly from the fuel-bound nitrogen of the biomass and, therefore, syngas.
A Through-Flow Approach Associating Velocity and Pressure Gradient Equations for Transonic Axial Flow Compressors Performance Prediction
Authors: Wang Mingyi , Li Tongxi , Wang Zhiheng , Xi Guang
Published: August 2024

The through-flow theory has always been an essential tool for compressor aerodynamic analysis and design because of excellent application value in balancing cost and accuracy. While general methods can give rapid predictions of compressors operation performance, there remains some lack of effective way of how to capture the characteristic at large flow rate for high-loaded transonic compressors. This is because the traditional approach concentrating on solving velocity gradient equation by given flow rate boundary, however, when the compressor runs to the choked condition, the back pressure will drop sharply and the mass flow rate will be almost unchanged, which makes it difficult for the solution to converge to an accurate flow rate and pressure ratio. Therefore, in this paper, the prediction of the aerodynamic performance for transonic compressors by associating the mass flow rate with the pressure boundary is investigated. The operation performance region of map and flow field characteristic can be obtained by solving the velocity gradient equation and pressure gradient equation of the quasi-orthogonal line located on the S2m stream surface based on the streamline curvature approach (SLC). NASA Rotor 37 and the three-stage NASA 74-A axial compressors are analyzed and the results demonstrate this approach has higher accuracy in predicting aerodynamic performance than the previous method especially near the choked condition. At the same time, the approach can achieve rapid solution as well as good stability.
Numerical and Experimental Study of Flow-Induced Vibrations in Micro-Tube Heat Exchangers
Authors: Phan Hien M. , Newman Felix , O’Pray Connor E. , Parikh Dhairya
Published: August 2024

Thermal management presents an increasing challenge in future engineering systems, especially in applications like combined cycle precooling, waste heat recovery, and innovative propulsion systems. These systems face a growing demand for managing higher heat loads while coping with limited heat sink. Central to these thermal management systems is the heat exchanger, with micro-tube heat transfer emerging as a promising solution for future technologies. Micro-tube heat exchangers are becoming popular owing to their ability to significantly enhance the heat transfer surface area while maintaining a compact core volume.

As the demand for high-performance, lightweight heat exchangers escalates, micro-tube heat exchangers are being designed to be increasingly compact yet highly loaded. This trend poses significant challenges to their structural integrity, particularly under harsh operational conditions. Flow-induced vibrations, a critical concern in the design of tubular heat exchangers, can lead to tube failures, compromising the safe operation of engineering systems. While the flow-induced vibrations of conventional-sized heat exchangers have been extensively studied, there is a noticeable gap in the research on similar phenomena in micro-tube heat exchangers.

This paper details ongoing research at Reaction Engines Ltd to aid the design of safe and robust heat exchangers, focusing on the flow-induced vibrations in micro-tube heat exchangers and utilizing a cutting-edge laser vibrometry test facility. A predictive model, employing an unsteady flow simulation approach and eigenvalue analysis, has been formulated. A key observation is the distinctive coupled transverse-streamwise orbital motion in micro-tube heat exchangers, differing from the predominantly transverse direction of failures in conventional-sized heat exchangers.
Film Cooling Efficiency Reconstruction on Turbine Blade Surfaces Based on Point Measurement Data
Authors: Zhang Fengtao , Yu Hongqian , Liu Xing , Yang Li
Published: August 2024

High fidelity and resolution of film cooling data on turbine blades can provide accurate and visually informative insights into physical phenomena, serving as valuable references for designers. However, due to the complexity of heat transfer problems and the limitations of data acquisition devices, obtaining complete and high-resolution data on film cooling efficiency is challenging. Therefore, this study focused on the reconstruction of complete thermo-fluid image data from spatially sparse data. In this study, a multigrid iterative neural operator network (MINO) was proposed as the data completion algorithm. Besides, the prior knowledge of flat plate film cooling was introduced through transfer learning to enhance the predictive accuracy of the model. The results of the study demonstrate that the MINO model can reconstruct the film cooling efficiency distribution of the turbine blade relatively accurately and capture most of the texture details in the flow field. Compared with existing linear interpolation methods, the average predictive error of the MINO model is significantly lower, with an overall reduction of approximately 40% and 50% for the suction side and pressure side, respectively. Furthermore, the MINO transferred model still exhibited robust reconstruction capability even at low sampling densities, with less increase in errors compared to the linear interpolation model as the sampling density decreases.
Experimental Characterization of Very High Turning Single and Tandem Compressor Profiles
Authors: Babin Cedric , Leclercq Kevin , Al Rifai Anis , Princivalle Remy , Fontaneto Fabrizio
Published: August 2024

The axial compressor front stages of the forthcoming aircraft engines architectures will operate at high subsonic inlet Mach number over a large range of incidence angles, while providing unprecedented turning levels. In this study, a single vane profile and a tandem vane configuration, designed for identical inlet flow conditions and for a design turning in the excess of 45 degrees, have been experimentally assessed in a linear cascade arrangement. The present paper outlines first the aerodynamic design philosophy for the tested profiles. Then, the design of the facility and of the test section are presented in view of the challenges imposed for the performance evaluation of very high turning compressor cascades at engine-like conditions. The instrumentation is also presented, and finally, the performance comparison of each blade configuration is given and put into perspective with the measurement uncertainty. The analysis of the blade sets performance aims to highlight the advantages and drawback of each configuration. The use of both the experimental data and CFD computations help to provide an insight into the loss driving mechanisms. This paper demonstrates that single profile blades and tandem configurations can be designed to provide identical performance close to the design incidence region of the loss bucket, with the latter outperforming at high positive and negative incidences despite a smaller solidity.
Combustion System Development and Test for Stoichiometric H2/O2 Combustion in Steam Atmosphere
Authors: Hase Matthias , Meisl Jürgen , Prade Bernd
Published: August 2024

An Oxy-H2 in steam atmosphere combustion system for the use in a novel application is presented. The combustion system is intended to be used in a steam boosting system (“Clean Steam-Booster”) for steam cycle applications. The steam boosting system can provide additional heat and mass flow for peak power demands as well as for grid stabilization by increasing the steam temperature and the mass flow for short operation periods. The approach is free of the classical combustion emissions, NOx and CO, as well as from the greenhouse gas, CO2. The combustion system is intended to be operated at close to stoichiometric conditions.

The combustion system has been developed with the primary targets stable combustion, low H2 and O2 contents in the exhaust steam, and a good thermal design concept which allows meeting life for a production design. A couple of different burner and combustor variants were designed. All burners are diffusion style burners to avoid flashback issues which is a major risk for the Oxy-H2 combustion in case of premixing due to the very high flame speeds. The general design concept for the combustion system is a two-stage steam supply with one steam stage in the burner and a second through the combustor. To support design decisions, kinetic analyses were performed which are also discussed in the present paper.

A core development step of the combustion system design is the design validation in a high-pressure combustion test. To enable such tests, a labscale rig was designed, manufactured, and erected, including pressure vessel and back pressure valve for tests up to 15 bar operation pressure. Also, the supply infrastructure for steam, O2 and H2 was well as the measurement and control system had to be setup at the combustion test facility of Siemens Energy in Mülheim/Germany.

In the validation test, stable combustion operation up to 15 bar could be demonstrated. Moreover, low H2 and O2 contents in the exhaust gas were achieved. The thermal design worked as expected.

The precise mass flow measurement and control were identified as major challenge for the operation of the combustion system close to stoichiometric conditions. Small deviations from a stoichiometric mixture have a direct and significant impact on the H2 and O2 fractions in the exhaust.

As next steps another design iteration for the combustion system design, an up-scaling of the combustion system and closed loop steam cycle tests are planned.
Coupled Design of Multi-Component Distortion-Generating Devices for Aircraft Engine Ground Tests – Part I: Design Methodology and Numerical Validation
Authors: Grondin Julissa , Leborgne Michaël , Baert Lieven , Lepot Ingrid , Gouttière Alexandre , Dieu Donavan , Wunsch Dirk , Boufidi Elissavet , Madasseri Payyappalli Manas , Fontaneto Fabrizio , Spriet Tony , Talbotec Jérôme
Published: August 2024

Engine performance, operability and vibration can be drastically affected by inlet flow non-uniformity. Devices that can accurately and flexibly recreate total pressure and swirl distortion cartographies in test environments are required to assess engine-airframe incompatibilities as soon as possible during the design process. This paper presents a numerical design methodology for a two-component distortion device that a) is manufacturable with additive manufacturing for maximum flexibility, and b) is able to reproduce complex and realistic patterns featuring high levels of total pressure distortion and flow angles magnitudes.

The device consists in the combination of a honeycomb total pressure screen with airfoil-shaped edges, and a turning vanes assembly. This first part paper describes the design methodology, from the preliminary design of each isolated component to their joint optimization by means of a global surrogate-assisted optimization strategy making use of a multi-fidelity model for the coupled device. The preliminary design tools are applied and validated on two canonical configurations for each type of distortion. Then the coupled design strategy is applied on two realistic configuration patterns featuring combined total pressure and swirl distortions.

The experimental testing of the screens and a cross-comparison between design and experimental tests is discussed in the second part of this paper.
Techno-Economic Comparative Assessment of High Temperature Heat Pump Architectures for Industrial Pumped Thermal Energy Storage
Authors: Trevisan Silvia , Buchbjerg Bjarke , Höeg Arne , Guedez Rafael
Published: August 2024

The industrial sector is a key global source of wealth, but it is also recognized as a major challenge toward worldwide decarbonization. Today the industrial sector requires more than 22 % of the global energy demand as thermal energy and produces for this about 40 % of the total CO2 emissions. Solutions to efficiently decarbonize the industrial sector are deemed. This work presents a comparative techno-economic performance assessment of a high temperature heat pump integration within a molten salts based power to heat system for industrial heat flexible generation. The main system performance is reported in terms of required working conditions and temperature for the heat pump and thermal demand size as well as reduction of the attainable levelized cost of heat (LCoH) against non-flexible electric boiler based systems. The impact of different industrial load profiles, electricity prices, heat pump capital cost and heat pump real to Carnot efficiency ratio are also presented.

The results highlight that the proposed system can be cost-competitive, particularly for thermal demand around 10 MW and waste heat temperatures above 80°C. Under these conditions LCoH reduction higher than 15 %, with respect to the considered non-flexible electric boiler alternative, are attainable. These LCoH reductions are primarily driven by savings in electrical consumption as high as 30 %. This study sets the ground for further power-to-heat techno-economic investigations addressing different industrial sectors and identifies main system and components design strategies, integrations, and targets.
State-of-Charge (SoC) Management of PTES Coupled Industrial Cogeneration Systems
Authors: Albay Alp , Zhu Zhennan , Mercangöz Mehmet
Published: August 2024

We present a novel optimization-based state-of-charge (SoC) management solution for pumpedthermal energy storage (PTES) systems capable of charging and discharging with electrical power and discharging high temperature heat — for integration with industrial processes. The considered PTES system in the study uses a supercritical CO2 recuperative Brayton cycle (SCBC) utilizing molten salt and water as hot and cold storage materials respectively. A SoC balancing heat exchanger is integrated along with a utility heat exchanger to the base design to accommodate withdrawal of high temperature heat. The study builds on a detailed part-load study to extract the SoC dynamics as a function of the electrical power as well as the heat withdrawal rate. These functions are used for modelling SoC management as an optimization problem considering three case studies; a base case for only electrical operation given an electricity price profile, a flexible operation study with electrical and heat price profiles, and a continuous heat supply case where the system delivers heat to a process. The results indicate that the proposed approach can enable optimized operation while respecting SoC constraints under different scenarios and illustrate the potential for the integration of PTES systems with industrial processes for the decarbonization of heat provision.
Numerical Investigation of Reheat Hydrogen Flames in the Sequential-Combustion Stage of a Heavy-Duty Gas Turbine
Authors: Gruber Andrea , Meyer Ole H. H. , Heggset Tarjei , Wood Birute , Ciani Andrea
Published: August 2024

Recent theoretical studies and experimental evidence suggest that turbulent burning-rate augmentation, flame instabilities and NOx emissions, notoriously characterizing fuel-lean hydrogen premixed combustion, are significantly mitigated at reheat combustion conditions. This is due to the favorable effects of high reactants temperature in reducing the strength of thermo-diffusive instabilities that occur in hydrogen premixed combustion with augmented severity for increasing pressure and flame temperature. In this context, Ansaldo’s Constant Pressure Sequential Combustion (CPSC) system appears as an attractive approach to enable hydrogen firing of gas turbines that target high flame temperatures to retain high cycle efficiency. The present numerical modelling effort represents the first attempt to perform high-resolution Large-Eddy Simulation (LES), featuring detailed chemical kinetics and a fully compressible representation of the reactive flow, of hydrogen reheat combustion in a full-scale industrial combustor geometry with realistic geometrical features. Building upon earlier numerical modelling efforts that were limited to generic and geometrically simplified configurations with idealized reactants mixing conditions (GT2022-83218) [1], the ability of the turbulent combustion model to predict injection of the hydrogen fuel, mixing with the vitiated oxidizer stream and spontaneous ignition of the reactants mixture at the expected stabilization location is verified. Low and high flame-temperature conditions for 100% hydrogen-firing of the engine are simulated confirming that the numerical results are in accordance with the expected flame stabilization behavior observed in test-rig experiments. Furthermore, an analysis of the hydrogen premixed flame structure at reheat combustion conditions is provided highlighting the differences observed at various locations within the combustion chamber.
Frequency Topology Optimization of Fan Blade Considering Stress Stiffening and Spin Softening
Authors: Xu Shenli , Wang Mingzhou , Mu Lizhong , Zhou Yan
Published: August 2024

Fan blades are prone to failures due to dynamic loads and their optimal design ensures the stability of aircraft engines. Compared with the shape and parameter optimization, topology optimization design has a larger design space and frequency adjustment range. However, fan blades are limited by performance requirements such as aerodynamics and load-bearing, and are often designed as hollow structures with fixed main path of load transfer. The existing fan blade design methods impose strict requirements on the construction of frequency topology optimization design space.

This paper constructs a frequency topology optimization method of fan blades that considers both stress stiffening and spin softening. The effect of element pseudo density on stress stiffness matrix and spin softening matrix is taken into consideration. A local structural topology optimization method based on the initial path of load transfer is proposed, and a casting constraint method was used to achieve small amplitude frequency control without changing the blade basic structure through erosion and dilation. This paper also constructs the topology optimization formulations of the fundamental frequency maximization, the frequency gap maximization and frequency avoidance constraint. A simple plate example and a hollow fan blade example are used to verify the effectiveness of the optimization method.
Experimental Investigation of Stall Mechanism and Warning Method in a Two-Stage Transonic Fan Under Inlet Distortion With Axial Slot Casing Treatment
Authors: Fan Zhonggang , Du Juan , Liu Yang , Ba Dun , Zhang Min , Ji Guofeng
Published: August 2024

The stall warning method has been employed to predict the level of disturbances in active control systems. Significant advancements have been made by identifying the pre-stall disturbances. Regardless of the propagation, disturbances almost initiate simultaneously at a specific circumferential location under uniform inflow. When the compressor suffers from inlet distortion, the disturbances might disappear in the undistorted region. The differences between the distorted and undistorted regions pose challenges to developing an accurate and robust warning method. Revealing the characteristics of pre-stall disturbances under the distorted inflow is a key to realizing engineering applications. For this purpose, the stalling process and stall warning method was conducted in a two-stage transonic fan. Work on this project has concluded that the pre-stall disturbances initially arise in the region where the rotor exits the distorted region, diminish in the process of circumferential propagation, and ultimately disappear in the position where the rotor enters the distorted region. Due to the impact of circumferential secondary flow, the incidence is largest and the fluctuation of the tip leakage flow is strongest in the position where the rotor exits the distorted region. Consequently, the reduction in warning parameters can be first detected. In the pursuit of an effective stall warning system under inlet distortion, a novel warning index associated with the characteristic frequency band is proposed. This index, coupled with a variable threshold, enables stall warning at any circumferential position with only one transducer. The efficacy of this method is further validated under axial slot casing treatment boundary.
Impact of Steady-State and Mixing Plane Assumptions: An Application to an Industrial Two-Stage High-Pressure Turbine
Authors: Mazzei Lorenzo , Casini Niccolò , Da Soghe Riccardo , Michelassi Vittorio , Ciani Alessandro , Jurek Tomasz , Andrei Luca
Published: August 2024

The continuous temperature and pressure increase to target thermodynamic efficiency and power density in modern gas turbines (GT) stretches the design space and calls for high-pressure turbines (HPT) designed with very accurate design tools. Cooling, both internal and external, is necessary as the evolving fluid temperature is beyond the material’s capability. Therefore, the HPT design process is growingly assisted by computational fluid dynamics (CFD) that due to computers and numerical methods improved efficiency and accuracy respectively allows running CFD during design iterations. The design evolves from the conceptual phase, usually completed with the help of simple correlations and proprietary technology curves, not covered here, and proceeds with the preliminary and detailed phases where aero, thermal, mechanical, and geometrical details are progressively defined. It is paramount that design choices made in the preliminary phase are refined in the detailed phase without requiring excessive rework.

This paper concentrates on the CFD approach typically used in a detailed design phase, where the flow path and airfoils defined in a preliminary phase are completed with the geometrical and operational details of disk cavities and their purge, shrouds or squealer tips, seals, cooling and all the details that completely define the HPT. The paper describes the challenges of incorporating all the geometrical details and compares two approaches: steady-state with mixing plane and unsteady with a specific technique to reduce the computational effort compared to the full-wheel simulation (Time Transformation method). The differences in terms of aerodynamics and adiabatic wall temperatures are highlighted and assessed in the perspective of the computational effort associated with the different modelling approaches. The analysis reveals that unsteady effects and cavity purge flows and cavity geometry may have an important effect on the predictions of the thermal load in specific areas of the hot gas path.
Numerical Study of Flow and Combustion Dynamics in a Hydrogen-Air Rotating Detonation Combustor-Stator Integrated System
Authors: Pal Pinaki , Braun James , Wang Yiqing , Athmanathan Venkat , Paniagua Guillermo , Meyer Terrence R.
Published: August 2024

In the present work, a first-of-its-kind 3D large-eddy simulation (LES) study is conducted to numerically investigate the combustion dynamics as well as aero-thermal phenomena in a full-scale non-premixed hydrogen-air rotating detonation engine (RDE) (with a diverging-shaped lower-end wall), when integrated with nozzle guide vanes (NGV) acting as the turbine stator. The wall-modeled LES framework incorporates hydrogen-air detailed chemical kinetics and adaptive mesh refinement (AMR). A comparative analysis is carried out for two operating conditions with different fuel/air mass flow rates but global equivalence ratio of unity, and considering RDE configurations without and with stator. The LES model is validated against available experimental data for the low mass flux condition with respect to detonation wave speed/height, wave dynamics, and axial static pressure distribution. Numerical results indicate significant deflagrative combustion occurring in the fill region near the inner wall due to the formation of recirculation zones in the injection near-field driven by the backward facing step. The leading detonation wave is found to be trailed by an azimuthal reflected-shock combustion (ARSC) wave, consistent with experimental observations, which consumes unburned vitiated reactants that leak through the main detonation wave. The main detonation wave characteristics, such as detonation wave speed/height, and combustion efficiency do not change appreciably with the presence of NGV. A novel combustion diagnostic technique based on chemical explosive mode analysis (CEMA) is employed to quantify the fraction of heat release occurring in the detonative mode versus deflagrative mode for the simulated conditions. The exit flow is found to be nearly fully subsonic and supersonic for the low and high mass flux conditions, respectively. Further analysis of the exit flow profiles shows that the presence of the NGV renders the flow more axial and significantly impacts the exit Mach number and total pressure, while the total temperature shows negligible change. In addition, the low mass flux operating point, despite exhibiting more deflagrative losses within the combustor, yields overall lower pressure drop from plenum to exhaust, which is mainly attributed to lower pressure drop across the injectors. Lastly, the RDE-NGV configuration exhibits higher total pressure loss compared to RDE without stator across both the mass flux conditions. This study extends the state-of-the-art in numerical modeling of pressure gain combustion systems by demonstrating high-fidelity 3D reacting LES of a full-scale RDE-NGV systems for practical insights pertaining to RDE-turbine integration for power generation.
Acoustic Modes in an Open Box Cavity With Variable Depth Using Two Distinct Wind Tunnels
Authors: Hammer Steffen , Twaddle James , Fridh Jens , Paniagua Guillermo
Published: August 2024

Cavity resonances in ducts is a classical problem that has involved researchers from very different fields over time. More recently the aerospace community became engaged again due to resonances found within the flow path of aero-engines, for example in bleed cavities in the low pressure compressor section. These resonances can lead to problems with the structural integrity of upstream components, and thus warrant investigation.

This study expands the previous data set of an open box cavity with variable depth (D) and a rectangular opening with length (L), effectively testing L/D = [4, 2, ½] ratios. This parameter was indicated by Rossiter to be a strong predictive parameter in frequency generation.

The paper compares the results of the same cavity geometry within two wind tunnels of different dimensions and operational setups. The intention of the study is to isolate the Rossiter modes from any other geometric modes that are due to the wind tunnel’s test section geometry. This isolation allows the modification of the model of Rossiter and the cavity depth model of East in order to improve the predictive capability over a larger range of Mach numbers and for deeper cavities.

One wind tunnel has an open loop continuous flow operation where the Mach number is set by changing the outlet static pressure. The second wind tunnel has a blow-down operation where both Mach and Reynolds numbers can be set independently by pulling a downstream vacuum and setting the upstream total pressure. The experiments were performed for an operating range from low subsonic to transonic Mach numbers. The analysis focuses on modifying the constants in both the Rossiter model and the cavity depth model proposed by East along with investigating the phenomenon of mode switching for Rossiter modes.

The analyses show a good repeatability of the data set between the two wind tunnels displaying strong resonances at similar operating points. The new proposed constants for the Rossiter model when using an L/D = 2 are γ = 0.15, κ = 0.58. For the deeper cavity with L/D = 0.5 the constants proposed are γ = 0.15, κ = 0.9. The modification of the cavity depth model by East to better predict the mode above Mach 0.3 is proposed by adjusting the constant B = 2.5 and leaving A = 0.65. An independence from Reynolds number of the acoustic frequency generation is demonstrated within the operating range. A mode-switching behavior is identified with the shallowest and deepest cavity showing multiple mode transitions within the operating range and a near constant Rossiter mode 1 for L/D = 2.
Combustion Computational Fluid Dynamics Simulations of a Range of Experimental Lean Hydrogen/Natural Gas Blend Flames
Authors: Gauthier Pierre , Zghal Malika , Durocher Antoine , Vena Patrizio , Fan Luming , Francolini Benjamin , Bergthorson Jeffrey M. , Yun Sean
Published: August 2024

Hydrogen micromix combustion is a promising technology to reduce the environmental impact of both aero and land-based gas turbines by delivering carbon-free, and potentially ultra-low-NOx, combustion with a greatly reduced risk of autoignition or flashback.

A preliminary investigation of such novel injector geometries, that are capable of stabilizing premixed, partially premixed, and diffusion flames, using fuel mixtures ranging from pure methane to pure hydrogen, was performed in an Atmospheric Combustion Rig at the National Research Council Canada (NRC). High quality experimental data was collected using Particle Image Velocimetry (PIV) and both OH and acetone planar laser-induced fluorescence (PLIF). Combustion Computational Fluid Dynamics (CCFD) Methods and Tools were developed and validated against these experimental results, for multiple flame shapes, and combustion modes, resulting from fuel lean mixtures of H2/CH4 ranging from 70%/30% to 90%/10% blends, by volume.

Within the current study, Large Eddy Simulations (LES) of a single injector, as well as an array of 5 injectors were investigated. A Flamelet Generated Manifold (FGM), Kinetic Rate, tabulated chemistry approach, using 1D Freely Propagating Flamelets, is used as the combustion model. LES-FGM simulations of the entire experimental injector and test section assembly were performed. Meshing and numerical methodologies were developed, resulting in good agreement for the flame shapes and positions; as well as for the measured thermoacoustic pressure fluctuation amplitude changes, over the range of simulated operating conditions. Further work is underway in applying and assessing the validity of this LES-FGM methodology for flames, with injection systems using micromix technology, at more typical engine conditions, where higher pressures and temperatures are found.