bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Method to Predict Non-Measured Parameters of Industrial Gas Turbines Using Kalman Filter Technique
Authors: Lee Jae Hong , Kim Tong Seop , Kang Do Won , Sohn Jeong Lak , Lee Jung Ho
Published: November 2019

Gas turbines are most widely used for power generation and operate under various conditions and loads. Gas turbine control is important to cope with various situations, and the turbine inlet temperature (TIT) is the most important parameter because it is directly related to the power output and life cycle of the turbine. Thus, precise prediction and control of the TIT are important in terms of the stable operation and life cycle management of gas turbines. This paper proposes a new method to predict non-measured parameters such as the air flow and TIT using Kalman filter techniques. The Kalman filter is widely used for estimating the instantaneous state of a system and can estimate non-measured parameters. The Kalman filter algorithm was implemented in a gas turbine analysis program using MATLAB. The reliability of the new method was verified through various case studies using virtual data and real operating data. The results were compared with those of a model-based gas turbine diagnostics program. The computing time of the Kalman filter and model-based diagnostics program were also compared to confirm the capability of the new method. The results indicate that the new method is more suitable for diagnostics and monitoring applications than the model-based analysis program. Finally, two case studies were performed to confirm the feasibility of the new method using two virtual datasets. The results confirm that the Kalman filter can predict the non-measured parameters precisely.
Experimental and Numerical Investigations on Flow Losses of a U-Bend and Return Channel System for Centrifugal Compressor
Authors: Xi Guang , Tian Yubao , Guo Yunpeng , Tang Yonghong , Wang Zhiheng
Published: November 2019

The flow losses in a U-bend and return channel system of an inter stage has an important influence on the stage performance. To study the flow characteristics in such system, a pseudo-stage which consists of pseudo guide vanes, U-bend and return channel, combined with a normal stage, was designed and its performance curves were measured at different machine Mach numbers. Simultaneously, the numerical simulations, in which different data processing methods of CFD post process were adopted, were performed and the prediction accuracy was verified by comparison with the experimental results. The results indicated that the design of pseudo guide vanes provides an approximately constant flow direction at the inlet of U-bend with the variation of inlet Reynolds number, which matches the blade metal angle of the return channel well. The further analyses on the measured and numerical results showed that the loss characteristics vary with the inlet Reynolds number. When the Reynolds number is greater than a critical Reynolds number, the loss coefficient in the U-bend and return channel keeps nearly constant. The non-uniformity of flow angle and total pressure at the outlet of return channel were also illustrated and discussed.
Effects of High Heating Loads on Unsteady Flow and Heat Transfer in a Cooling Passage With a Staggered Array of Pin Fins
Authors: Lee Chien-Shing , Shih Tom I.-P. , Bryden Kenneth M. , Dennis Richard A.
Published: November 2019

Time-accurate 3-D CFD simulations based on the SST-SAS turbulence model were performed to study the effects of heat load on the unsteady flow and heat transfer in a cooling duct with a staggered array of short pin fins. For this duct, the static pressure at its exit is maintained at 25 bars, and the cooling air that enters has a temperature of 673 K with a flow rate that produces a Reynolds number of 25,000. To examine the effects of heat load, the following isothermal wall temperatures were studied: 678 K, 873 K, 1073 K, and 1,273 K, which give rises to heat loads that range from 15 kW/m2 to 1.5 MW/m2. Results obtained show high heat loads to cause considerable changes in the temperature of the cooling flow along the duct, which causes significant changes in density and velocity as well as viscosity and thermal conductivity. These changes along the duct were found to affect the locations where unsteady flow separation take place around the pin fins, the magnitude of the vorticity shed in the wakes, and the shedding Strouhal number. These unsteady flow mechanisms in turn strongly affect the nature of the surface heat transfer. A correlation formula for the heat transfer, which accounts for the effects of heat loads, was developed.
Dynamic Behavior of the Ultra-High Efficiency Gas Turbine Engine, UHEGT, With Stator Internal Combustion
Authors: Ghoreyshi Seyed M. , Schobeiri Meinhard T.
Published: November 2019

The paper investigates the dynamic behavior of an Ultra-High Efficiency Gas Turbine Engine (UHEGT) with Stator Internal Combustion. The UHEGT-technology was introduced for the first time to the gas turbine design community at the Turbo Expo 2015. In developing the UHEGT-technology, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in the first three HP-turbine stator rows. Noticeable improvement in the engine thermal efficiency and power along with other performance advantages are brought by this technology. In the current paper, a dynamic simulation is performed on the entire gas turbine engine (UHEGT) using the nonlinear dynamic simulation code GETRAN. The simulations are in 2D (space-time) and include the majority of the engine components including rotor shaft, turbine and compressor, fuel injectors, diffuser, pipes, valves, controllers, etc. The thermo-fluid conservation laws are applied to the flow in each component which create a system of nonlinear partial differential equations that is solved numerically. Two different fuel schedules (steep rise and Gaussian) are applied to all injectors and the engine response is studied in each case. The results show that fluctuations in the fuel flow lead to fluctuations in most of the system parameters such as temperatures, power, shaft speed, etc. However, the shapes and amplitudes of the fluctuations are different and there is a time lag in the response profiles relative to the fuel schedules. It is shown that an increase in average fuel flow in the system leads to a small drop in efficiency due to the cycle change from the design point. Moreover, it is seen that the temperatures usually rise fast with increase of fuel flow, but the system tends to cool down with a slower rate as the fuel is reduced.
Superposition Characteristics of Full Coverage Film Cooling With Various Blowing Ratio and Row Number
Authors: Wang Lang , Li Xueying , Li Weihong , Ren Jing , Jiang Hongde
Published: November 2019

Effusion cooling is the next step in gas turbine blade cooling to get the higher turbine inlet temperature, but the interaction between the front jet flow and the rear jet flow still need to be studied. In this paper, the effect of row number and blowing ratio are studied experimentally by PSP and numerically by RANS. One to five rows of staggered cooling holes were investigated with blowing ratio 0.5, 1.0 and 1.5. It is found that the income boundary layer helps the rear rows penetrate deeper to the main flow at low blowing ratio M = 0.5, the cooling performance become worse for single row. The performance at high blowing ratio M = 1.5 for row 3–5 is nearly not effected by income boundary layer due to blowing off. Finally, a corrected equation based on Sellers superposition method for full coverage film cooling is realized, which could explain the “fully developed level” and improve the accuracy of prediction of full coverage film cooling.
Kinetics Study of a Staged Combustor Concept for Oxy-Fuel Combustion Gas Turbine Cycles
Authors: Qian Wenkai , Liu Haoyang , Zhu Min , Li Suhui
Published: November 2019

Oxy-fuel combustion has been identified as a promising technology for CO2 capture and NOx reduction. It has great potential to be applied in gas turbine cycles. Previous studies, however, reveal that simple oxy-fuel combustors suffer from issues like flame blowoff and CO emissions especially at part load, due to the high CO2 content in the combustion atmosphere. In this paper, a staged combustor concept is proposed to mitigate flame blowoff and CO emissions issues for load operations. The conceptual combustor consists of three zones axially: primary zone, CO burnout zone, and dilution zone. All fuel is fed to the primary zone, while O2 is distributed to the primary zone and CO burnout zone. CO2 is distributed to the primary zone and dilution zone. By adjusting the distribution of the O2 and CO2, the primary zone operates at a relatively higher flame temperature at part load, which helps improve the flame blowoff performance. A chemical reactor network model is developed to study the effects of key design/operating parameters on flame blowoff and CO emissions. Results show that the distribution ratios of O2, CO2 and residence time between different zones are the key factors that influence flame blowoff and CO emissions. To mitigate flame blowoff and CO emissions at part load, the distribution of O2 needs to be carefully chosen so that the primary zone operates under near-stoichiometric or slightly lean condition, while the distribution of CO2 to the primary zone also needs to be reduced. The residence time split has stronger influence on CO emissions than CO2 and O2 distribution.
Suppression of Combustion Instabilities in a Premixed Swirl Combustor With Acoustic Liner
Authors: Xu Liangliang , Wang Guoqing , Mo Changcai , Liu Xunchen , Li Lei , Qi Fei , Sun Xiaofeng
Published: November 2019

Acoustic liner is one of effective passive control methods of combustion instabilities. This paper presents an experimental investigation about the suppression of the combustion instabilities using acoustic liners. A premixed swirling combustor was built and a specially designed acoustic liner was set at the downstream of the flame zone. Then, experiments of rigid wall, acoustic liner without and with tunable bias flow were carried out respectively. Furthermore, considering the viscous dissipation of airflow is temperature related, the temperature of the bias flow was adjusted in order to evaluate its effects on thermoacoustic instabilities. The bias flow was heated by electric taps before entering the acoustic liner in this rig. Results shows that the unstable Helmholtz mode could be triggered, and the oscillation amplitude grows with the increase of the bias flow Mach number, while the instability of 1/4 wavelength mode may be completely suppressed. Within the scope of the experiments, the unstable Helmholtz mode triggered by the bias flow can be attenuated by raising the bias flow temperature, while no substantial changes are observed about the quarter wave mode. These results are rarely reported in previous studies. Studying the effects of acoustic liner on combustion instabilities can provide useful knowledge regarding its application in real combustion systems.
Performance Analysis of a Hybrid Solar Gas Turbine Plant Combined With Chemical Recuperation
Authors: Wang Zhitao , Qi Wanling , Li Tielei , Li Shuying
Published: November 2019

This paper studies the influence of the high-temperature solar preheating system and chemical recuperation system on the overall performance of a MW-level three-shaft gas turbine. In order to obtain accurate simulation results, this paper adopts an integrated simulation method, where the simulation models of the solar receiver and gas turbine are established on the Matlab/Simulink platform, the simulation model of the chemical recuperation system is established on the Aspen Plus platform, and the interface between Matlab and Aspen Plus is developed for mutual communication. With the component maps, the Newton-Raphson iteration method is used to solve the thermodynamic performance of the gas turbine.

Based on the above simulation models and solution method, the effects of the mean receiver wall temperature (Ts) and steam-to-methane ratios (R) on the overall performance of the gas turbine are studied in this paper. From the perspective of safe operation, the influence of Ts and R on the net output power of the gas turbine is first calculated. The results show that in the safe operating range, chemical recuperation can significantly increase the net output power of the gas turbine, while the net output power increases first and then decreases with the increase of Ts. When the output power is constant, increasing Ts or R both can effectively reduce fuel consumption, and increasing R can also improve the heat recovery efficiency and the overall thermal efficiency. However, the heat losses of the receiver increase as Ts increasing, meanwhile, the heat recovery efficiency and the overall efficiency also decrease gradually. Therefore, in actual operation, various factors should be taken into account in order to reduce fuel consumption and improve the overall thermal efficiency.
Stochastic Fatigue Life Prediction Based on a Reduced Data Set
Authors: Celli Dino , Shen M.-H. Herman , Scott-Emuakpor Onome E. , Holycross Casey M. , George Tommy J.
Published: November 2019

The aim of this paper is to provide a novel stochastic life prediction approach capable of predicting the total fatigue life of applied uniaxial stress states from a reduced data set reliably and efficiently. A previously developed strain energy-based fatigue life prediction method is integrated with the stochastic state space approach for prediction of total cycles to failure. The approach under consideration for this study is the Monte Carlo method where input is randomly generated to approximate the output of highly complex systems. The strain energy fatigue life prediction method is used to first approximate SN behavior from a set of two SN data points. This process is repeated with another unique set of SN data points to evaluate and approximate distribution of cycles to failure at a given stress amplitude. Uniform, normal, log-normal, and Weibull distributions are investigated. From the Monte Carlo Method, fatigue data is sampled from the approximated distribution and an SN curve is generated to predict HCF behavior from LCF data.
Analytical Formulation of Friction Contact Elements for Frequency-Domain Analysis of Nonlinear Vibrations of Structures With High-Energy Rubs
Authors: Petrov E. P.
Published: November 2019

In gas-turbine engines and other rotating machinery structures rubbing contact interactions can occur when the contacting components have large relative motion between components: such as in rotating bladed disc-casing rubbing contacts, rubbing in rotor bearing and labyrinth seals, etc. The analysis of vibrations of structures with rubbing contacts requires the development of a mathematical model and special friction contact elements that would allow for the prescribed relative motion of rubbing surfaces in addition to the motion due to vibrations of the contacting components.

In the proposed paper, the formulation of the friction contact elements is developed which includes the effects of the prescribed relative motion on the friction stick-slip transitions and, therefore, on the contact interaction forces. For a first time, the formulation is made for the frequency domain analysis of coupled rubbing and vibrational motion, using the multiharmonic representation of the vibration displacements. The formulation is made fully analytically to express the multiharmonic contact interaction forces and multiharmonic tangent stiffness matrix in an explicit analytical form allowing their calculation accurately and fast. The dependency of the friction and contact stiffness coefficients on the energy dissipated during high-energy rubbing contacts and, hence, on the corresponding increase of the contact interface temperature is included in the formulation.

The efficiency of the developed friction elements is demonstrated on a set of test cases including simple models and a large-scale realistic blade.
Development and Application of Minimum Creep Strain Rate Metamodeling
Authors: Vega Ricardo , Stewart Calvin
Published: November 2019

Numerous minimum-creep-strain-rate laws exist, creating a challenge in determining which is best for a given material database. The objective of this study is to validate the applicability of a “metamodel” and its ability to model the minimum creep strain rate (MCR). A metamodel is a model that can combine and regress into different base models, in this case, seven established MCR models. The metamodel can be exploited using a calibration algorithm to rapidly calibrate the base models. The metamodel contains ten terms and eight material constants (one is a constraint, and another is stress as an input variable). Using the metamodel and calibration software, the user can determine the best MCR model for a given material database. Using the software, the metamodel is calibrated in two approaches: constrained and pseudo-constrained. The constrained approach restricts the metamodel to regress directly into one of the base models, allowing for the base models to be equally calibrated and compared alongside each other. The pseudo-constrained approach freely optimizes all eight of the metamodel material constants; however, the metamodel is modified to include 5 Heaviside function constants that turn on/off sections of the metamodel to increase the statistical-dependencies of the final model. This pseudo-constrained approach has the potential to identify novel MCR models that exist at the interface between the seven base models. Alloy data for 9Cr-1Mo-V-Nb (ASTM P91) was used with a total of 89 points which extended over a total of three isotherms: 600°C, 625°C, and 650°C. The MCR model that best fit the data was the Johnson-Henderson-Kahn model.
Topology and Physical Interpretation of Turbulence Model Behavior on an Array of Film Cooling Jets
Authors: Hodges Justin , Kapat Jayanta S.
Published: November 2019

This study strives to provide a critical review and evaluation of influential constituent components in the two-equation k-ε turbulence model class, which are often employed in large full-fidelity gas turbine simulations in industry. All conjectures made, regarding the turbulence model behavior, will be compared to in-house experimental film effectiveness data from a novel film cooling array configuration. This experimental data set is comprised of high resolution adiabatic film cooling effectiveness measurements throughout two film cooling arrays comprised of diffused film holes of modern shape (streamwise inclination of α = 30°, expansion of Φ1,2,3 = 10°, AR = 3.4, and β = 0° relative to the crossflow direction). The difference between each film cooling array is only a staggered verses inline pattern for the film holes, whereby each has a uniform spacing of X/D = P/D = 8. Local coverage, laterally averaged film cooling effectiveness, and superposition analysis was quantified over a variety of testing conditions (M = 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 at DR = 0.9).

First, rendered quantifications of the anisotropic nature of the turbulence are shown throughout the near-field injection region, by leveraging the Reynolds stresses to form anisotropic-invariant maps. Next, results from k-ε models using a linear, a cubic, and a quadratic constitutive relation are compared. Furthermore, effective and conservative scaling of the production and destruction terms in the turbulent transport equations was performed, within reasonable bounds, and the resulting impact on the adiabatic film effectiveness was quantified. This scaling encompasses the Cε2 coefficient, as well as the Durbin realizibility coefficient used in the turbulent viscosity definition. Finally, various formulations of the turbulent Prandtl number were compared, with the resulting adiabatic film effectiveness observed.
Unsteady Aerodynamics on Multi-Passage LP Last Stage Induced by Flow Separation Under Low Load Flow
Authors: Zhang Jing , Xie Danmei , Wu Fan , Du Haifen , Chen Wei
Published: November 2019

With the rapid development of renewable energy generation, the requirement for operational flexibility of power plants has increased. This has led to steam turbine operating frequently at low load flow conditions.

This paper focuses on the investigation of unsteady aerodynamic excitation in the last stage of LP under low load flow, which was conducted by assuming one single passage, to provide detailed flow information for optimization design. We present a numerical investigation of unsteady pressure forces on Multi-passage LP last blade rows caused by flow separation under low load flow. The flow field of the turbine was calculated by transient 3D computational fluid dynamic (ANSYS CFX16.0).

The results indicate the vortex strength induced by high incidence angle under low load flow having the characteristic of spatial non-uniformity and time non-uniformity. We found that the unsteady pressure forces on the rotor are significantly influenced by the separation vortex and have different phase pressure fluctuation between neighboring two rotor blades. The variation in the forces indicates that the neighboring rotor blades experience a load imbalance at every time step which may results in oscillation in the last long moving blades. In particular, the tip vortex plays a crucial part in unsteady aerodynamics.
Evaluation of Arabian Super Light and Arabian Extra Light Crude Oil for Use in Dry Low NOx (DLN) Combustion Systems
Authors: Goldmeer Jeffrey , Glaser Paul , Mohammad Bassam
Published: November 2019

The Kingdom of Saudi Arabia has seen significant transformation in power generation in the past 10 years. There has been an increase in the number of F-class combined cycle power plants being developed and brought into commercial operation. There has also been a shift to the use of natural gas as primary fuel. At the same time, there has been an interest in switching the back-up fuel for new power plants from refined distillates to domestic crude oils. Both Arabian Super Light (ASL) and Arabian Extra Light (AXL) have been proposed for use in new F-class gas turbine combined cycle power plants. This paper provides details on the combustion evaluations of ASL and AXL, as well as the first field usage of ASL in a gas turbine.
Experimental and Numerical Investigation on Film Cooling Performance and Flow Structure of Film Holes
Authors: Cao Nan , Li Xue , Wu Ze-yu , Luo Xiang
Published: November 2019

Discrete hole film cooling has been commonly used as an effective cooling technique to protect gas turbine blades from hot gas. There have been numerous investigations on the cylindrical hole and shaped hole, but few experimental investigations on the cooling mechanism of the novel film holes with side holes (anti-vortex hole and sister hole) are available. This paper presents an experimental and numerical investigation to study the film cooling performance and flow structure of four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) on the flat plate. The film holes have the same main hole diameter of 4mm and the same inclination angle of 45°. The adiabatic film cooling effectiveness is obtained by the steady-state Thermochromic Liquid Crystal (TLC). The flow visualization experiment and numerical investigation are performed to investigate the flow structure and counter-rotating vortex pair (CRVP) intensity. The smoke is selected as the tracer particle in the flow visualization experiment. The mainstream Reynolds number is 2900, the blowing ratio ranges from 0.3 to 2.0, and the density ratio of coolant to mainstream is 1.065. Experimental results show that compared with the cylindrical hole, the film cooling performance of the anti-vortex hole and sister hole shows significant improvement at all blowing ratios. The sister hole can achieve the best cooling performance at blowing ratios of 0.3 to 1.5. The fan-shaped hole only performs well at high blowing ratios and it performs best at the blowing ratio of 2.0. Flow visualization experiment and numerical investigation reveal that the anti-vortex hole and sister hole can decrease the CRVP intensity of the main hole and suppress the coolant lift-off because of side holes, which increases the film coverage and cooling effectiveness. For the sister hole, the side holes are parallel to the main hole, but for the anti-vortex hole, there are lateral angles between them. The coolant interaction between the side holes and main hole of the sister hole is stronger than that of the anti-vortex hole. Therefore, the sister hole provides better film cooling performance than the anti-vortex hole.
Investigation of Combustor-Turbine-Interaction in a Rotating Cooled Transonic High-Pressure Turbine Test Rig: Part 2 — Numerical Modelling and Simulation
Authors: Gövert Simon , Ferraro Federica , Krumme Alexander , Buske Clemens , Tegeler Marc , Kocian Frank , di Mare Francesca
Published: November 2019

Reducing the uncertainties in the prediction of turbine inlet conditions is a crucial aspect to improve aero engine designs and further increase engine efficiencies. To meet constantly stricter emission regulations, lean burn combustion could play a key role for future engine designs. However, these combustion systems are characterized by significant swirl for flame stabilization and reduced cooling air mass flows. As a result, substantial spatial and transient variations of the turbine inlet conditions are encountered. To investigate the effect of the combustor on the high pressure turbine, a rotating cooled transonic high-pressure configuration has been designed and investigated experimentally at the DLR turbine test facility ‘NG-Turb’ in Göttingen, Germany. It is a rotating full annular 1.5 stage turbine configuration which is coupled to a combustor simulator. The combustor simulator is designed to create turbine inlet conditions which are hydrodynamically representative for a lean-burn aero engine. A detailed description of the test rig and its instrumentation as well as a discussion of the measurement results is presented in part I of this paper. Part II focuses on numerical modeling of the test rig to further extend the understanding of the measurement results. Integrated simulations of the configuration including combustor simulator and nozzle guide vanes are performed for leading edge and passage clocking position and the effect on the hot streak migration is discussed. The simulation and experimental results at the combustor-turbine interface are compared showing a good overall agreement. The relevant flow features are correctly predicted in the simulations, proving the suitability of the numerical model for application to integrated combustor-turbine interaction analysis.
Control Strategies of an Academic Rotor/Stator Cavity Through Sensitivity Analysis
Authors: Queguineur Matthieu , Gicquel Laurent , Staffelbach Gabriel
Published: November 2019

Strong hydrodynamic instabilities are often observed in rotating cavities of turbomachinery in the aerospace industry for specific thermal and operating conditions. This highly unsteady motion of the flow, often referred to as ‘pressure bands’ phenomenon can be detrimental and jeopardize the structural integrity of aeronautical engines by damaging turbomachinery components or turbopumps in the context of space applications. In order to avoid this fluid structure interaction, a deeper understanding of the stability of the flow of rotating cavities becomes compulsory. A few studies enabled to point out the spatial distribution and origins of such multi-frequency flow. However control solutions have not yet been set up. In this context, an academic stator/rotor cavity is studied in this paper with a sensitivity analysis to base flow modification based on linear stability analysis. This latter points out the regions of the stator boundary layer of each mode where the flow should be modified. Possible passive control strategies are then proposed from the interpretation of the results. The more relevant solution being suction and injection actuators directly introduced on the stationary disk of the cavity.
Inlet and Outlet Characteristics Boundary Conditions for Large Eddy Simulations of Turbomachinery
Authors: Odier Nicolas , Poinsot Thierry , Duchaine Florent , Gicquel Laurent , Moreau Stéphane
Published: November 2019

Inlet an outlet boundary conditions are essential elements of any CFD predictions and this is even more so for turbomachinery Large Eddy Simulations, either applied to academic or industrial configurations. For compressible solvers, non-reflecting, characteristic inlet boundary condition imposing total pressure, total temperature and flow direction is usually needed, while an outlet relaxation methodology that automatically adapts the outlet static pressure as a function of the desired mass-flow rate rate is used for turbomachinery flow predictions. Establishing such a framework is clearly desirable especially for industrial use of LES. Development and validations remain necessary in such a fully unsteady context as detailled hereafter.
Investigation of Steam Turbine Warm-Keeping by Use of Air
Authors: Toebben Dennis , Luczynski Piotr , Wirsum Manfred , Mohr Wolfgang F. D. , Helbig Klaus
Published: November 2019

The changing energy landscape leads to a rising demand of more flexible power generation. A system for steam turbines warm-keeping provides the ability to shutdown conventional power plants during periods with a high share of renewable power. Simultaneously, these power plants are ready for grid stabilization on demand without an excessive consumption of lifetime during the start-up. One technical solution to keep a steam turbine warm is the use of hot air which is passed through the turbine. In addition, the air supply prevents corrosion during standstill and also enables the pre-warming after maintenance or long outages.

This paper investigates the warm-keeping process of an intermediate pressure steam turbine (double shell configuration) through the use of dynamic numerical Finite-Elements (FE) simulations. As a representative test-case, warm-keeping calculations during a weekend shutdown (60h) are conducted to investigate the temperatures, their distribution and gradients within the rotor and the casing. For this purpose an improved numerical calculation model is developed. This detailed 3D FE model (including blades and vanes) uses heat transfer correlations conceived for warm-keeping with low air mass flows in gear mode operation. These analytical correlations take heat radiation, convection and contact heat transfer at the blade roots into account. The thermal boundary conditions at the outer walls of rotor and casing are determined by use of experimental natural cool-down data. The calculation model is finally compared and verified with this data set.

The results offer valuable information about the thermal condition of the steam turbine for a subsequent start-up procedure. The warm-keeping operation with air is able to preserve hot start conditions for any time period. Most of the heat is transferred close to the steam inlet of the turbine, which is caused by similar flow directions of air and steam. Thus, temperatures in the last stages and in the casing stay well below material limits. This allows higher temperatures at the first blade groove of the turbine, which are highly loaded during a turbine startup and thus crucial to the lifetime.
Investigation and Thermal Modeling of the Thermal Contact Resistance at a Steam Turbine Blade Root
Authors: Toebben Dennis , Goerner Alexander , Luczynski Piotr , Wirsum Manfred , Mohr Wolfgang F. D. , Helbig Klaus
Published: November 2019

Increasing load ramps and temperature gradients in steam turbines, especially during start-ups, have a high impact on the component lifetime. Calculation models are commonly used to predict the lifetime consumption during such start-up procedures. However, the changing energy landscape requires innovative solutions to increase the power plant flexibility. In order to accelerate the start-ups with a simultaneously reduced lifetime consumption, hot air can be used to keep the steam turbine warm during shut downs. The calculation of heat fluxes within the steam turbine is crucial for the accurate prediction of the thermal state and the resulting lifetime consumption. Improved models enable the determination of life cycles as exact as possible.

During warm-keeping and pre-warming operations, the steam turbine rotates slowly. Thus, low centrifugal forces lead to high thermal contact resistances (TCR) at the blade roots, which influence the temperature distribution at the lifetime limiting locations, e.g. blade grooves. The paper presents heat transfer correlations, which describe the TCR depending on the rotational speed of the rotor. For this purpose, an experimental setup is designed in order to investigate the influence of contact pressure, ambient pressure and surface properties. For the detailed investigation of the complex heat fluxes at the T-root, a 3D Finite-Elements (FE) model is developed. This model calculates the TCR and specific heat fluxes based on measurement data. On the basis of the detailed evaluation, different analytical heat transfer correlation approaches with respect to the application in an overall steam turbine model are developed. These heat transfer correlations are integrated into the FE model and validated with additional measurements.
Modelling Geared Turbofan and Open Rotor Engine Performance for Year-2050 Long-Range and Short-Range Aircraft
Authors: Sebastiampillai Joshua , Jacob Florian , Mastropierro Francesco S. , Rolt Andrew
Published: November 2019

The paper provides design and performance data for two envisaged year-2050 state-of-the-art engines: a geared high bypass turbofan for intercontinental missions and a contra-rotating pusher open rotor targeting short to medium range aircraft. It defines component performance and cycle parameters, general powerplant arrangements, sizes and weights. Reduced thrust requirements for future aircraft reflect expected improvements in engine and airframe technologies. Advanced simulation platforms have been developed, using the software PROOSIS, to model the engines and details of individual components, including custom elements for the open rotor engine.

The engines are optimised and compared with ‘baseline’ year-2000 turbofans and an anticipated year-2025 entry-into-service open rotor to quantify the relative fuel-burn benefits. A preliminary scaling with non-optimised year-2050 ‘reference’ engines, based on Top-of-Climb (TOC) thrust and bypass ratio, highlights the trade-offs between reduced specific fuel consumption (SFC) and increased weight and engine diameter. These parameters are then converted into mission fuel burn using linear and non-linear trade factors from aircraft models.

The final turbofan has an optimised design-point bypass ratio (BPR) of 16.8, and a maximum overall pressure ratio (OPR) of 75.4 for a 31.5% TOC thrust reduction and a 46% mission fuel burn reduction per passenger kilometre compared to the respective year-2000 baseline engine and aircraft combination. The final open rotor SFC is 9.5% less than the year-2025 open rotor and 39% less than the year-2000 turbofan, while the TOC thrust increases by 8% versus the 2025 open rotor, due to assumed increase in aircraft passenger capacity. Combined with airframe improvements, the final open rotor-powered aircraft has a 59% fuel-burn reduction per passenger kilometre relative to its year-2000 baseline.
Experimental Investigation of Surge Phenomena in a Transonic Centrifugal Compressor
Authors: Ito Sasuga , Furukawa Masato , Gunjishima Satoshi , Usuki Hiroki , Ota Takafumi , Yamada Kazutoyo
Published: November 2019

Surge is an unsteady flow phenomenon occurring at low flow rates in the pipeline system including compressors. The surge is a phenomenon that must be avoided because of the danger in the operation: the pipeline equipment can be damaged or the operation cannot be continued. Experimental work is required not only to understand the unsteady behavior but to also validate the CFD used for more localized analysis and development of the understanding of the flow phenomena when operating near surge. Nevertheless, there are still many unclear points not only about the flow phenomenon at the inception of the surge which is important for the prediction of the surge but also about the surge behavior itself. Especially, as for the surge occurring in transonic centrifugal compressors, there are currently few experimental research cases due to the difficulty of the unsteady measurement.

In this research, we measured the time variations in pressure and flow rate in a transonic centrifugal compressor for a vehicle turbocharger which consists of an impeller, vaneless diffuser and scroll. In the experiments, the measurement pipes were set upstream and downstream of the compressor and the velocity and the wall static pressure were measured with an I-type hot wire probe and high response pressure transducers, respectively. In addition, to investigate the process and the occurrence point of the back flow in surge, the wall static pressure was measured by means of high response pressure transducers which were mounted on the shroud upstream of the impeller and the diffuser hub at the two-circumferential positions, respectively. As the result of the experiments, the unsteady flow process during the mild and deep surges was measured and the inception of deep surge was clarified.
Analysis of the Self-Excited Dynamics of a Heavy-Duty Annular Combustion Chamber by Large-Eddy Simulation
Authors: Michelassi Vittorio , Meloni Roberto , Riccio Giovanni , Ceccherini Gianni
Published: November 2019

This paper discusses the use of LES to predict the performance of an annular combustion chamber in stable operating conditions and in presence of self-exited dynamics. The availability of high-accuracy data taken in a full-scale combustion test facility allowed an extensive validation of the prediction capability. The analysis focuses on a small size heavy duty annular gas turbine whose size allows to test and compute the entire 360° combustion chamber.

The comparison with measurements confirms that, if the correct operating conditions are implemented, LES is capable to discern between stable and unstable operating conditions, as well as predict several other engineering relevant parameters, although the model is sometime affected by a limited shift in frequency.

The post processing of LES results in presence of combustion dynamics is not a trivial task. Here the results of the simulations have been post-processed by means of a triple decomposition method to determine a mean flow, a deterministic unsteady flow at the main instability frequency and a turbulent stochastic flow. Such decomposition indicated the instability triggering mechanism together with the cross-talk mechanism between different components. This approach is currently used for design phase, while further validation is on-going to include different geometries and operating conditions with the goal of reducing both risks and number of tests.
Updating the Helicopter Gas Turbine Engine Mass Model for the Defining of the Turboshaft Engine Optimal Operating Cycle Parameters
Authors: Kalabuhov D. S. , Grigoriev V. A. , Zagrebelnyi A. O. , Diligensky D. S.
Published: November 2019

The article describes the adjusted parametrical turboshaft gas turbine engine mass model that is applied for the helicopter engine operating cycle parameters optimization during a conceptual engineering.

During the operation of the take-off mass, which indirectly characterizes the cost of materials for the entire designed aircraft system, one of the main components which determines the coordination of the helicopter and its engine parameters is a mass of the gas turbine power unit. Moreover, during the parametrical studies the designed mass of a power unit should be defined by the parameters of a gas turbine engine; however, this type of dependencies is not that well enough studied for today. Therefore the evaluation of the dependency between the engine mass and its operational parameters is performed by using either generalized statistical data for existing designs or by parametrical mass models since there is nothing more precise up to date. However as new types of gas turbine engines appear it is required to update the values of parametrical model coefficients.

This article describes the influence of different cooling system units on the engine mass and also clarifies the coefficients that specify the engine mass advance by introducing the structural-technological measures. The last one is highly dependent on the designed gas turbine engine (GTE) serial production year. It also has been proposed to represent some coefficients that are used in the model as dependencies of the main operational parameters. This has allowed to perform the parametrical study and to gain predictive solutions in correspondence to the modern engine design level.
Developing Secondary Flow and Heat Transfer in the Entrance Region of a Square Channel With 45° Crossed Rib Arrangement
Authors: Wieler M. , Woerz B. , Jeschke P. , Rabs M.
Published: November 2019

This paper presents developing secondary flow and heat transfer measurements in a ribbed cooling channel. Experiments are carried out for Reynolds number ranging from 25,000–140,000. Regionally averaged local heat transfer measurements are conducted using heated copper segments. Flow measurements are carried out using a miniature five-hole pressure probe and presented for cross sections at intervals of 1.8 hydraulic diameters dh in flow direction. Results are compared to numerical simulations using explicit algebraic Reynolds stress and turbulent heat transfer models. The paper focuses on the entrance region where secondary flow structure has not emerged yet. The findings show that the well-known secondary flow structure of the crossed rib configuration, consisting of one large single rotating secondary flow, is not established until approximately 6–7 dh in main flow direction. Instead two opposed vortices are identified which dominate the flow characteristics and provide an increase in heat transfer of up to 15–20% when compared to the periodically developed flow condition. Thus, for the first time to the author’s knowledge, the paper describes in detail the developing secondary flow in a crossed rib arrangement and links it to the heat transfer distribution observed. In summary, this paper stresses the importance of the developing flow region for the design process in convection cooled gas turbines, especially for short channels of high pressure blades and vanes, as it has a significant effect on cooling channel heat transfer performance.
Rotor-Alone Tones in the Outflow Noise of a Centrifugal Compressor
Authors: Faßbender Armin , Enneking Martin , Jeschke Peter
Published: November 2019

This paper investigates the generation of rotor-alone tones and their contribution to the outflow noise in a transonic centrifugal compressor stage with vaneless diffuser and volute by means of unsteady full-annulus CFD-simulations. The aerodynamic field, as well as the generation and propagation of sound, were simulated simultaneously using the URANS-approach of the solver TRACE and a numerical grid consisting of 170M cells. To assess the accuracy of the predicted fluctuations, the investigation compares the simulated diffuser flow field to measured flow angles and pressure fluctuations obtained from experiments conducted on a large-scale test rig. The analysis explains the different sound generation mechanisms responsible for tonal components in the acoustic spectrum at the compressor outlet, based on the Fourier decomposition of the pressure fluctuations in diffuser and volute. Further, the paper analyzes the modal structure of the simulated sound field at the volute outlet by means of a radial mode analysis and discusses the influence of changing operating conditions on the sound power emitted. The analyses reveal that supersonic flow phenomena occurring at choked operating conditions cause a significant increase in noise emissions. Furthermore, the investigation shows that the sound field at the volute outlet is dominated by few low-order modes, a fact that justifies analysis using methods based on Compressed Sensing in future experimental investigations.
Injector Design Space Exploration for an Ultra-Low NOx Hydrogen Micromix Combustion System
Authors: Agarwal Parash , Sun Xiaoxiao , Gauthier Pierre Q. , Sethi Vishal
Published: November 2019

The depletion of fossil fuel resources, as well as the increasing environmental concerns have become the driving forces towards the research and development necessary for the introduction of alternative fuel such as hydrogen into civil aviation. Hydrogen is a suitable energy source primarily because it is free of carbon and other forms of impurities and is also the most abundant element in the universe. The advantages of using Liquid Hydrogen (LH2) for civil aviation extends beyond carbon-free mission level emissions; LH2 combustion can potentially reduce NOx emission by up to 90%, providing long-term sustainability and unrivalled environmental benefits.

The paper presents a simplified parametric analysis to investigate the influence of various injector design parameters on a hydrogen micromix combustor reactive flow field. The main characteristics investigated are the flame structure (shape and position), the aerodynamic stabilization of the flame and the resulting NOx emissions. The design parameters include variations in the air-feed dimensions and the hydrogen injection diameter. A suitable numerical model was established by comparing various turbulence modelling approaches, reaction mechanisms and turbulence-chemistry interaction modelling schemes. The predictive capabilities, and limitations, of each of these modelling approaches, are assessed. The numerical challenges and limitations associated with modelling H2/air combustion at high pressure and temperature conditions are detailed. The influence of varying the injector design parameters on the mixing and hence the NOx characteristics is assessed.
Erosion in an MI SiC/SiC Ceramic Matrix Composite (CMC)
Authors: Presby M. J. , Gong C. , Kane S. , Kedir N. , Stanley A. , Faucett D. C. , Choi S. R.
Published: November 2019

Erosion phenomenon of ceramic matrix composites (CMCs), attributed to their unique architectural configurations, is markedly different from conventional monolithic ceramic counterparts. Prior to further integration of CMCs into hot-section components of aeroengines subject to erosive environments, their erosion behavior needs to be characterized, analyzed, and formulated. The erosion behavior of a 2-D woven melt-infiltrated (MI) SiC/SiC CMC was assessed in this work as a function of variables such as particle velocity and size. The erosion damage was characterized using appropriate analytical tools such as optical and scanning electron microscopy (SEM). A phenomenological erosion model was developed for SiC/SiC CMC material systems with respect to kinetic energy of impacting particles in conjunction with nominal density, matrix hardness and elastic modulus of the SiC/SiC CMCs. The model was in reasonable agreement with the experimental data.