bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axial Compressor Fouling and its Effect on Gas Turbine Fuel Consumption and Emissions
Authors: Allen Cody W. , Balaji Purushotham , de Oliveira Maurício 
Published: January 2021

Abstract
The literature contains many studies relating gas turbine axial compressor degradation with impurities entering the inlet flow path. The collision and adhering of these impurities onto compressor blades can produce both recoverable and non-recoverable degradation in the compressor, leading to lost overall efficiency. More recently, the topic of how to optimally schedule when compressor washes should occur has been investigated. In many of the scheduling optimization studies, the cost associated with the change in fuel flow for a given fouled state is characterized indirectly as part of an overall fuel calculation for a given fouled state.
In this paper, we aim to quantitatively answer the question of what this small quantity of fuel due to compressor fouling actually is. Additionally, we show how this can be included in solving for optimal schedules of compressor washes and estimate the CO2 emissions attributable to compressor fouling. We begin with a look at the literature on compressor fouling to identify common methods and assumptions of how fouling can manifest or be imposed. We then derive a first principles, steady state equation to relate compressor performance parameters with fuel flow. We validate this equation at nominal conditions with data obtained from Solar Turbine’s test cells. Additionally, we develop a generic industrial gas turbine model using the Numerical Propulsion System Simulation software and apply the fouling constraints found from the literature review to run a fouling simulation. The results further validate our equation and provide insight into the quantity of fuel resulting from compressor fouling. We end the paper with a look at how the derived model can be used in the problem of optimizing compressor wash schedules as well as give an estimate on increases in CO2 emissions due to compressor fouling.
Numerical Analysis of Flutter in Variable Geometry Compressors
Authors: Suzuki Kentaro , Zhao Fanzhou , Vahdati Mehdi 
Published: January 2021

Abstract
Aeroelastic behaviour of a transonic rotor in a newly designed 1.5 stage compressor with variable geometry is studied numerically in this paper. The stage is intended to be the front part of a one-shafted large frame industrial gas turbine (IGT) compressor. The compressor was designed using open-source software MULTALL and numerical computations were performed using the three-dimensional aeroelasticity code AU3d, which has been tested and validated for many aeroelastic test cases over the past 25 years. Flutter analysis for the 1F mode was performed at various design and off-design operating conditions which are typically experienced in IGT (varied inlet temperature and inlet guide vane angle). Although in all the cases the rotor remained stable, clear trends in aerodynamic damping were observed, which can be explained by shock position. In the last phase, the effects of increased tip gap size on the flutter stability were studied. The increase in tip clearance did not result in flutter; unsteady computations without blade motion showed a tip rotating instability with 11 cells travelling at 84% of the shaft speed in the stationary frame. Due to the frequency proximity between the rotating instability and blade natural vibration mode, large amplitude displacement driven by lock-in was observed in the fluid-structure coupled simulation. It was concluded that this type of aeroelastic instability which can be mistaken for flutter is the main threat for this IGT compressor.
Physical Quantity Synergy in the Internal Flow Field and Application in Radial-Inflow Turbines
Authors: Shao Ziyi , Zhang Xuehui , Wang Xing , Zhu Yangli , Li Wen , Chen Haisheng 
Published: January 2021

Abstract
The internal flow field and loss distributions are quite complicated in the radial-inflow turbine. It is necessary to reinforce physical understandings of the relationship between the flow and loss. Inspired by the synergy principle in the convective heat transfer, the synergy applicable for the radial turbine is innovatively derived from the Navier-Stokes equations. According to the mathematical expression, the smaller the synergy angle is, the higher flow resistance and loss should be. The paper attempts to assess the validation of the synergy principle in the radial turbine based on numerical simulations firstly, then the relationship between the synergy angle and loss is analyzed in detail. It is found that the regions where high total pressure loss coefficient and high dimensionless entropy generation locate correspond to the relatively small synergy angle, which agrees well with the mathematical analysis. The relatively low streamwise synergy angle corresponds to the high-loss regions near the suction side and wake on the blade-to-blade stream surface. The relatively low spanwise and circumferential synergy angle correspond to the high-loss regions near the tip clearance and wake on the span-theta stream surface. Under off-designed conditions, the synergy principle also shows great performance as an apparent negative correlation of total pressure loss coefficient versus circumferential synergy angle could be perceived.
Multi-Variable Adaptive Control Method for Turbofan Engine With Dynamic and Input Uncertainties
Authors: Liu Jiashuai , Wang Xi , Zhu Meiyin , Miao Keqiang 
Published: January 2021

Abstract
The dynamic characteristics of the turbofan engine vary greatly in the full flight envelope, which makes the problem of dynamic uncertainty and input uncertainty very prominent. This brings different degrees of performance impact to the engine control system and even makes it lose stability. This paper proposes an adaptive variable parameter control method for dealing with multivariable dynamic uncertainty and input uncertainty. In this paper, the dynamic uncertainty and input uncertainty are mathematically converted into standard matched uncertainty, which can be handled more conveniently. Firstly, in the state space model, for the case where the number of state variables is less than or equal to the number of input variables and the input matrix satisfies the full-rank condition of the row, the existence of the right pseudo-inverse matrix of the input matrix can be guaranteed. So the dynamic uncertainty can be separated from the system matrix, and the input uncertainty can be separated from the input matrix. Thus these uncertainties are equivalently transformed into parametric matched uncertainty. Then the matched uncertainty model with two vectors of bounded basis functions is established. Secondly, the Lyapunov quadratic function is constructed by the closed-loop tracking error vector and the adaptively adjustable control parameter estimation errors, and the Lyapunov stability constraint is considered. Then, under the premise of considering the dynamic characteristics of the actuator, an adaptive control algorithm for multivariable matched uncertainty model of turbofan engine is derived. Finally, ground and high altitude simulations are carried out on the dual-loop control system based on the nonlinear dynamic model of the turbofan engine. The results show that the control system has robust stability and anti-interference performance for dynamic uncertainty and input uncertainty of turbofan engine in the full flight envelope. The fan speed control loop basically achieves no static error tracking. The dynamic error of the core speed control loop is less than 0.6% and the steady state error is less than 0.05%. By introducing stronger parameter change rate information to the controller, its performance can be further improved, and the transient state control is more stable.
Effects of Film Hole Shape and Turbulence Intensity on the Thermal Field Downstream of Single Row Film Holes
Authors: Zhang Zheng , Zhu Hui-ren , Xu Wei-jiang , Liu Cun-liang , Wu Zhuang 
Published: January 2021

Abstract
A nylon mesh coated with broadband thermochromic liquid crystal was set in different planes perpendicular to the mainstream direction at various locations downstream of the film hole. By the temperature visualization technique, the colorful non-dimensional temperature images on the nylon mesh of cylindrical hole, water-drop hole and dustpan shaped hole at different blowing ratios and turbulence at angle of 30° and 60° were visualized. The visualization experiment visually studied the effects of hole shape, hole inclination angle, blowing ratio and mainstream turbulence on the distribution of the film. The results show that stream-wise diffusion of water-drop hole reduces kidney vortex intensity, making higher attachment of the film of water-drop than that of cylindrical hole, consequently the lateral coverage range of water-drop hole film is wider than that of cylindrical hole film. The lateral diffusion of dustpan shaped hole further reduces the kidney vortex intensity. This obviously increases the film coverage and strengthens the adhesion of film of dustpan shaped hole. Increasing the inclination angle of the hole and the blowing ratio will increase the normal velocity of the jet and increase the thickness of the film. however, increasing inclination angle and blowing ratio will enhance kidney vortex intensity and decrease the film cooling effectiveness. The high turbulent intensity of mainstream will enhance the lateral diffusion of the film and enhance the mixing of the secondary flow and mainstream, so the continuity and uniformity of film are better. However, the intense mix of secondary flow and mainstream results in the non-dimensional temperature of the film drops sharply and the film coverage reduced accordingly.
Wetness Measurement and Droplet Transport Analysis in Actual Steam Test on a Scaled Low Pressure Turbine
Authors: Sasao Yasuhiro , Segawa Kiyoshi , Kudo Takeshi , Takata Ryo , Osako Masaki , Yamamoto Satoru 
Published: January 2021

Abstract
Understanding the phenomenon and quantitative prediction of wet loss, quantitative prediction of erosion are still challenges in ST development. The aim of the actual steam test reported in this paper was to verify the performance of a newly developed ST. Still a comprehensive understanding of the wetness phenomenon is also a significant issue. Therefore, in connection with the actual steam test, efforts were made to develop a method for analyzing the three-dimensional causes of wetness loss and erosion. As the first report on the wet phenomenon analysis performed in this actual steam test, this paper reports wet measurement results and analysis results. In the actual steam testing of a 0.33 scaled steam turbine, wetness measurements were carried out at the third stage (L-1) and the final stage (L-0), and its characteristic wetness distribution was analyzed using our original CFD-code MHPS-NT.
This 0.33 scaled steam turbine consists of the final three stages (LP-end) and the inlet steam conditioning stage (total of four stages), and wetness distributions in the blade height-wise were measured using two different wetness probes under several operating conditions. Wetness distribution did not change linearly with changes in ST inlet temperature, but dynamic changes in peak position and shape were observed. From the ST inlet to the exhaust chamber, the generation of fine droplets, the capturing of droplets by the wall surfaces, and the behavior of water films and coarse droplets were comprehensively analyzed using a three-dimensional (3-D) unsteady Eulerian-Lagrangian coupling solver that takes into account non-equilibrium condensation. This CFD code (MHPS-NT) is an improved version of Original-NT developed by Tohoku University. By considering the relative position and structure of the wet probe and blade cascade in CFD, it was found that the wetness is formed remarkable circumferential distribution by the moisture separation of the upstream blade rows and end-walls. The circumferential distribution of wetness can be a factor that makes it difficult to grasp the liquid phase distribution inside the steam turbine as an error factor independent of the accuracy of the optical measurement device. Due to the effects of water droplet capturing, the LP-end outlet wetness at the design point may be underestimated by 21% relative. It is also reported that because the wetness has a distribution in the meridian direction, wetness measurements by the wet probe may contain measurement errors independent of the measurement accuracy.
Numerical Investigations on Full Blended Blade and Endwall Technique
Authors: Meng Tongtong , Ji Lucheng , Li Xin , Li Jiabin , Ling Zhou 
Published: January 2021

Abstract
In present state of art, compressor blades can work efficiently between the span of 20%–80%, while nearly 30% of the total loss comes from endwall region. Previous studies have shown that Blended Blade and End Wall (BBEW) which is a control technique can reduce the corner separation effectively. To further reduce the loss, enhance diffusion capability and restrain the secondary flow in the endwall region, in addition of a kind of non-axisymmetric endwall, Full-BBEW technique is put forward. Firstly, the geometric method of the Full-BBEW technique is presented on a NACA65 cascade with the unchanged axial passage area. Moreover, under the category of Full-BBEW technique, according to the different geometry characteristic, BBEW (blended blade and endwall) model, IOEW (inclining-only hub) model and Full-BBEW model are presented. Then in order to find the most effective design, numerical investigation and optimization based on the Kriging surrogate model are employed on the models. Compared with the prototype, the total pressure loss coefficient decreases by 7%–9% in optimized Full-BBEW cases and the aerodynamic blockage coefficient decreases about 23%–36%. Through analysis, the blended blade geometry creates a radial pressure gradient at the end section and push the low-energy fluid up to the mainstream. As the result, the loss decreases significantly between 5%–25% span range. Meanwhile, the intersection of boundary layer weakens because of the expanded dihedral angle. On the other hand, the inclining-only hub geometry reduces the circumferential pressure gradient and restrains the crossflow in corner. Overall, though the loss in mainstream increases slightly, Full-BBEW technique can reduce the boundary layer intersection and the crossing flow in corner so that the diffusion capability further increases and the aerodynamic performance in the endwall region improves effectively.
Effects of Upstream Step Geometry on Axisymmetric Converging Vane Endwall Heat Transfer and Film Cooling at Transonic Conditions
Authors: Bai Bo , Li Zhigang , Li Jun , Mao Shuo , Ng Wing , Xu Hongzhou , Fox Michael 
Published: January 2021

Abstract
In real gas turbine engines, a gap/step interface commonly exits between upstream of the inlet guide vane endwall and combustor, called upstream endwall misalignment, due to the errors of assembly and the thermal expansion. This endwall misalignment, commonly being presented as the gap/step geometry with different heights, has a significant effect on the endwall heat transfer and film cooling coverage distributions.
This paper presents a detailed experimental and numerical study on the effects of upstream endwall misalignment (step geometry) on the vane endwall heat transfer and film cooling in a transonic linear turbine vane passage. The experiment measurements were performed in a blowdown wind tunnel at simulated realistic gas turbine operating conditions (high inlet freestream turbulence level of 16%, exit Mach number of 0.85 and exit Reynolds number of 1.7 × 106. Three types of upstream step geometry were tested at design blowing ratio (BR = 2.5) for the same vane profile: I) baseline geometry with zero-step height of ΔH = 0 mm; II) forward-facing step geometry with negative step height of ΔH = −5 mm; III) backward-facing step geometry with positive step height of ΔH = 5 mm. The endwall thermal load and film cooling coverage distributions were measured using transient infrared thermography, being presented as endwall Nusselt number Nu and adiabatic film cooling effectiveness η, respectively.
Detailed comparisons of experiment measurements with numerical predictions were also presented and discussed for three types of upstream step configurations with ΔH = −5, 0, 5 mm, respectively. The numerical simulations were performed by solving the steady-state Reynolds Averaged Navier Stokes (RANS) with Realizable k-ε turbulence model, based on the commercial CFD solver ANSYS Fluent v.15. The effects of upstream step geometry were numerically studied, at the same design blowing ratio BR = 2.5, by solving the endwall Nusselt number, film cooling effectiveness and secondary flow field for various upstream step heights: three forward-facing step heights (from −8 mm to −3 mm), a baseline step height (0 mm), and four backward-facing step heights (from 3 mm to 10 mm).
The results show the upstream forward-facing step geometry is beneficial for the endwall thermal load and film cooling, though the improvement is weak for all step heights (less than 10% decrease in endwall heat transfer and less than 10% increase in endwall film cooling). However, the upstream backward-facing step geometry is pernicious for the endwall heat transfer and film cooling, and the influence increases with the increasing upstream backward-facing step height. The backward-facing step geometry obviously alters near endwall flow field, leading to an enhancement (up to 20%) in endwall heat transfer and significant reduction (up to 60%) in endwall film cooling effectiveness.
User Assistance for the Application of Multidisciplinary Design Tools
Authors: Schaber Reinhold , Kaiser Sascha , Luisoni Gionata 
Published: January 2021

Abstract
Multidisciplinary design tools are the backbone of conceptual design studies to evaluate and assess future propulsion systems. In the last decade, the IT capabilities dramatically increased. At the same time, “zooming” capabilities and more complex evaluation methods found their way into predesign tools. As a consequence, the bottleneck when performing a design study is neither the computational power nor sufficient computer memory anymore, but rather the abilities of the users to apply the dedicated tools adequately.
Therefore, it is crucial to limit the administrative tasks dealing with input and output as much as possible. Those administrative tasks can comprise the preparation of input data and — even more importantly — the check of the model setup and the inspection of the results regarding physical soundness.
The paper describes by means of examples how to cope with the challenges described above. The following topics will be addressed: standardization in the field of model configuration (engine model library), automated multidimensional check of multidisciplinary propulsion system models, use of high fidelity methods for pre-design, state-of-the-art error detection, semi-automated parametric studies including the automated set-up of a parametric study, automated convergence improvement, automated result handling, and error detection provided by the codes themselves or by other means of external user guidance.
Large-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison With Experiments
Authors: Töpperwien Karl , Collin-Bastiani Félix , Riber Eleonore , Cuenot Bénédicte , Vignat Guillaume , Prieur Kevin , Durox Daniel , Candel Sébastien , Vicquelin Ronan 
Published: January 2021

Abstract
During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler-Lagrange description of the liquid spray, an energy deposition model to mimic ignition and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this lift-off takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.
Efficient Steady and Unsteady Flow Modeling for Arbitrarily Mis-Staggered Bladerow Under Influence of Inlet Distortion
Authors: Phan Hien M. , He Li 
Published: January 2021

Abstract
Accurate and efficient predictions of the steady and unsteady flow responses due to the blade-to-blade variation as well as due to the non-axisymmetric inlet distortion have been continually pursued. Computation of two problems concurrently has been rarely done in the past partly because of the need to perform whole annulus bladerow simulations, despite the advances in the current state-of-the-art methods with the phaseshift single passage simulations. The current work attempts to deal with this challenge by developing a new computational approach based on the principle of the multiscale method in the framework of a commercial solver (CFX). The methodology formulation relies on summation of the constituent source terms, each of which corresponds to a particular flow perturbation. The source term element corresponding to the blade-to-blade variation effect is linearly superimposed as in the classical Influence Coefficient Method. Only the relative positions between the reference blade and its neighbor matter in this method, thus enables an arbitrarily mis-staggered bladerow to be computed efficiently. In addition, the source term arisen due to the inlet distortion is calculated based on spatial Fourier transform. A key enabler is that the source term can be pre-computed using a small set of identical blade passages. The source term is then propagated to different spatial and temporal locations depending on the combination of the mis-staggering pattern and the inlet distortion. The multiscale treatment makes it possible to predict a high-resolution flow field effects on the base coarse mesh as if the fine mesh is solved, while achieving a computational gain. The source term summation method proposed in the current work has been validated using a uniformly staggered bladerow, and an arbitrarily mis-staggered bladerow in a clean inflow condition as well as that subject to an inlet distortion.