Clocking and Potential Effects in Combustor–Turbine Stator Interactions

Investigations of combustors and turbines separately have been carried out for years by research institutes and aircraft engine companies, but there are still many questions about the interaction effect. In this paper, a prediction of a turbine stator’s potential effect on flow in a combustor and the clocking effect on temperature distribution in a nozzle guide vane are discussed. Numerical simulation results for the combustor simulator and the nozzle guide vane (NGV) of the first turbine stage are presented. The geometry and flow conditions were defined according to measurements carried out on a test section within the framework of the EU FACTOR (full aerothermal combustor–turbine interactions research) project. The numerical model was validated by a comparison of results against experimental data in the plane at a combustor outlet. Two turbulence models were employed: the Spalart–Allmaras and Explicit Algebraic Reynolds Stress models. It was shown that the NGV potential effect on flow distribution at the combustor–turbine interface located at 42.5% of the axial chord is weak. The clocking effect due to the azimuthal position of guide vanes downstream of the swirlers strongly affects the temperature and flow conditions in a stator cascade.

Mapping Complex Geological Surface Morphology During Landing Operations Using 3-D Inversion of Ultra-Deep Electromagnetic LWD Data

Ultra-deep azimuthal electromagnetic (EM) logging-while-drilling (LWD) tools are frequently used during landing operations for early detection of the reservoir top. This enables alterations to the well plan before the reservoir is penetrated. To date, this approach has relied on one-dimensional (1-D) inversions that accounts only for changes in resistivity above or below the wellbore. When geology is complex, resulting in lateral changes in resistivity, 3-D inversion of EM data is required to provide increased reservoir understanding. This paper presents a case study from offshore Brazil, targeting a turbidite deposit. A complex reservoir surface was expected, as defined by seismic data for the area. Although top structure rugosity and lateral position uncertainty had been incorporated into the prognosis, the impact of surface topography on inversion results while landing was not anticipated. During real-time operations, 1-D EM inversion was used along with correlation of shallow LWD data to map the reservoir top. It was clear the geology was more complicated than depicted by the 2-D geological model constructed from the 1-D inversion and that lateral changes in surface morphology may be occurring. Post well a 3-D inversion of the EM data revealed the 3-D geological structure. During the initial approach, the 1-D inversion indicated that relief of the reservoir top was more exaggerated than expected; the well intersected a sharp peak prior to approaching the target zone. The misfit on the 1-D inversion indicated there was potential for lateral variation in resistivity, influencing the 1-D results; lateral changes can produce artefacts that obscure the subsurface structure. This was confirmed after drilling with analysis of ultra-deep azimuthal resistivity images, indicating significant changes in resistivity to the left and right of the borehole. A 3-D EM inversion was run to depict these complex subsurface geometries. The 1-D inversion results were better understood post-drill with the 3-D inversion results, which show a high point in the reservoir top to the side of the wellbore that was drilled past, but not penetrated by, the well. This high-resistivity zone had a negative effect on the 1-D inversion results and made delineation of the reservoir top difficult. Understanding lateral variations in formation and fluid boundaries can improve well placement and reservoir understanding. This knowledge can impact landing scenarios and well placement within the reservoir. Three-dimensional inversion of ultra-deep azimuthal EM LWD data in real time will provide a clearer picture of the position of resistivity changes while drilling. This will enable decisions to be made that affect the azimuthal position of a well, as well as its vertical position during drilling, thereby facilitating optimal well placement, even in complex geological environments or for infill wells requiring precise well placement.

Development and Uncertainty Characterization of Rotating 3D Velocimetry using a Single Plenoptic Camera

Rotating 3D velocimetry (R3DV) is a single-camera PIV technique designed to track the evolution of flow over a rotor in the rotating reference frame. A high-speed (stationary) plenoptic camera capable of 3D imaging captures the motion of particles within the volume of interest through a revolving mirror from the central hub of a hydrodynamic rotor facility, a by-product being an undesired image rotation. R3DV employs a calibration method adapted for rotation such that during MART reconstruction, voxels are mapped to pixel coordinates based on the mirror’s instantaneous azimuthal position. Interpolation of calibration polynomial coefficients using a fitted Fourier series is performed to bypass the need to physically calibrate volumes corresponding to each fine azimuth angle. Reprojection error associated with calibration is calculated on average to be less than 0.6 of a pixel. Experimental uncertainty of cross-correlated 3D/3C vector fields is quantified by comparing vectors obtained from imaging quiescent flow via a rotating mirror to an idealized model based purely on rotational kinematics. The uncertainty shows no dependency on azimuth angle while amounting to approximately less than 0.21 voxels per timestep in the in-plane directions and correspondingly 1.7 voxels in the radial direction, both comparable to previously established uncertainty estimations for single-camera plenoptic PIV.

A Kinematic Study of Individual Rotating Detonation Engine Waves Using K-means Algorithm

The current research is concerned with studying the instantaneous properties of the detonation waves in a RDRE by tracking each individual wave and recording its position, velocity, and peak intensity as it travels around the annulus. This information is retrieved by a non-intrusive method consisting of using a data mining technique, the k-means algorithm, to distinguish each detonation from each other in a particular frame. An algorithm was then developed to match the detonations of a current frame to the ones of a previous frame. The code was validated against results found from the back-end imaging method developed by the Air Force Research Laboratory with excellent agreement. Results for two and three-wave mode cases show that the instantaneous detonation wave speeds oscillate around the mode locked average wave speed computed from a detonation surface. Moreover, the investigation of the relationship of the detonation’s peak light intensity with the azimuthal position revealed to also be oscillatory but more distinct.

M8R tropomyosin mutation disrupts actin binding and filament regulation: The beginning affects the middle and end

Dilated cardiomyopathy (DCM) is associated with mutations in cardiomyocyte sarcomeric proteins, including α-tropomyosin. In conjunction with troponin, tropomyosin shifts to regulate actomyosin interactions. Tropomyosin molecules overlap via tropomyosin–tropomyosin head-to-tail associations, forming a continuous strand along the thin filament. These associations are critical for propagation of tropomyosin's reconfiguration along the thin filament and key for the cooperative switching between heart muscle contraction and relaxation. Here, we tested perturbations in tropomyosin structure, biochemistry, and function caused by the DCM-linked mutation, M8R, which is located at the overlap junction. Localized and nonlocalized structural effects of the mutation were found in tropomyosin that ultimately perturb its thin filament regulatory function. Comparison of mutant and WT α-tropomyosin was carried out using in vitro motility assays, CD, actin co-sedimentation, and molecular dynamics simulations. Regulated thin filament velocity measurements showed that the presence of M8R tropomyosin decreased calcium sensitivity and thin filament cooperativity. The co-sedimentation of actin and tropomyosin showed weakening of actin-mutant tropomyosin binding. The binding of troponin T's N terminus to the actin-mutant tropomyosin complex was also weakened. CD and molecular dynamics indicate that the M8R mutation disrupts the four-helix bundle at the head-to-tail junction, leading to weaker tropomyosin–tropomyosin binding and weaker tropomyosin–actin binding. Molecular dynamics revealed that altered end-to-end bond formation has effects extending toward the central region of the tropomyosin molecule, which alter the azimuthal position of tropomyosin, likely disrupting the mutant thin filament response to calcium. These results demonstrate that mutation-induced alterations in tropomyosin–thin filament interactions underlie the altered regulatory phenotype and ultimately the pathogenesis of DCM.

Influence of Key Design Parameters on the Aerodynamic Performance of a Centrifugal Compressor Volute for Turbocharger Applications

A centrifugal compressor volute should ideally collect the pressurized flow at the diffuser outlet and convey it to the outlet piping as efficiently as possible. The total pressure loss related to the conversion of a radial flow into an axial one, however, is often not negligible, especially for applications where severe dimensional constraints are given, such as in turbochargers applications. Having a reliable tool for the performance prediction of the volute, flexibly adaptable to external constraints, is then pivotal in the design phase of new prototypes. Within this context, a fully parametric tool has been developed. Based on few geometrical inputs, it allows an automatic generation of both the CAD model of the volute and the numerical setup for the CFD calculation. The shape of the volute cross-section can be fully customized and automatically adapted to the azimuthal distributions of the area and centroid radius given in input by the user. The volute tongue can be also freely modified in terms of shape, azimuthal position and width. An extensive parametric analysis was then carried out, aimed at investigating the influence of key design parameters needed to define the shape of the volute on the internal fluid dynamics. Particular attention was paid to the tongue modelling strategy and shape, being it the critical feature for the volute flow performance. As a result, some annotated indications are given to define the first layout of a volute when approaching a new design.

Computational and Experimental Study of the Unsteady Convection of Entropy Waves Within a High Pressure Turbine Stage

This paper describes the transport and the interaction of pulsating entropy waves generated by combustor burners within a high pressure turbine stage for aeronautical application. Experiments and Computational Fluid Dynamics (CFD) simulations were carried out in the context of the European Research Project RECORD. Experimental campaigns considering burner-representative temperature fluctuations (in terms of spot shape, fluctuation frequency and total temperature variation percentage) injected upstream of an un-cooled high-pressure gas turbine stage have been performed in the high-speed closed-loop test-rig of the Fluid Machine Laboratory (LFM) of Politecnico di Milano (Italy). The pulsating entropy waves are injected at the stage inlet in streamwise direction at four different azimuthal positions featuring a 7% over-temperature with respect to the main flow with a frequency of 90 Hz. Detailed time-resolved temperature measurements (in the range of 0–200 Hz) upstream and downstream of the stage, as well as in the stator–rotor axial gap were performed. Time-accurate CFD simulations with and without entropy fluctuations imposed at the stage inlet were performed with the TRAF code, developed by the University of Florence. A numerical post-processing procedure, based on the DFT (Discrete Fourier Transform) of the conservative variables has been implemented to extract the low frequency content connected to the entropy fluctuations. Measurements highlighted a significant attenuation of the entropy wave spot throughout their transport within the stator channel and their interaction with the rotor blade rows, highly depending on their injection azimuthal position. Simulations show an overall good agreement with the experiments on the measurement traverses, especially at the stage outlet. By exploiting the combination of experiments and simulations, the aerodynamic and thermal implications of the temperature fluctuation injected upstream of the stage were properly assessed, thus allowing suggest useful information to the designer. The comparison with the experiments confirms the accuracy of the CFD method to solve the periodic, but characterized by a low frequency content event, associated with the entropy wave fluctuation.

Computational and Experimental Study of Hot Streak Transport Within the First Stage of a Gas Turbine

The paper discusses the migration, the interaction with the blades, and the attenuation of hot streaks generated by combustor burners, during their propagation within the first turbine stage of aero-engines. Experiments and computational fluid dynamics (CFD) simulations were carried out in the framework of the European Project RECORD and on its follow-up. Measurements considering burner-representative temperature perturbations injected upstream of an un-cooled high-pressure gas turbine stage were performed in the high-speed closed-loop test-rig of the Politecnico di Milano (Italy). The hot streaks were injected in a streamwise direction at the stage inlet in four different circumferential positions with respect to the stator blade. They feature a 20% over-temperature with respect to the main flow. Detailed temperature measurements as well as unsteady aerodynamic measurements upstream and downstream of the blade rows were performed. Time-accurate CFD simulations of the flow upstream and within the turbine stage were performed with the TRAF code, developed by the Università degli Studi di Firenze (Italy). Measurements show a relevant attenuation of hot streaks throughout their transport within the stator and the rotor blade rows, highly depending on the injection azimuthal position. The perturbations were observed to lose their spatial coherence, especially in the transport within the rotor, and to undergo severe spanwise migration. Simulations exhibit a good agreement with the experiments on the measurement planes and allow tracking the complex flow phenomena occurring within the blade rows. Finally, the aerodynamic and thermal implications of the inlet temperature perturbations are properly highlighted and discussed.

Aeroelastic response of a multi-megawatt upwind HAWT based on fluid-structure interaction simulation

With the increase demand for greener, sustainable and economical energy sources, wind energy has proven a potential promising sustainable source of energy. The trend development of wind turbines tends to increase rotor diameter and tower height to capture more energy. The bigger, lighter and more flexible structure is more sensitive to smaller excitations. To make sure that the dynamic behavior of the wind turbine structure will not influence the stability of the system and to further optimize the structure, a fully detailed analyses of the entire wind turbine structure is crucial. Since the fatigue and the excitation of the structure are highly depend on the aerodynamic forces, it is important to take blade-tower interaction into consideration in the design of large-scale wind turbines. In this work, an aeroelastic model that describes the interaction between the blade and the tower of a horizontal axis wind turbine (HAWT) is presented. The high-fidelity fluid-structure interaction (FSI) model is developed by coupling a computational fluid dynamics (CFD) solver with finite element (FE) solver to investigate the response of a multi-megawatt wind turbine structure. The results of the computational simulation showed that the dynamic response of the tower is highly depend on the rotor azimuthal position. Furthermore, rotation of the blades in front of the tower cause not only aerodynamic force pulls on the blade but a sudden reduction of the rotor aerodynamic torque by 2.3 % three times per revolution.

Computational and Experimental Study of Hot Streak Transport Within the First Stage of a Gas Turbine

The paper discusses the migration, the interaction with the blades, and the attenuation of hot streaks generated by combustor burners, during their propagation within the first turbine stage of aero-engines. Experiments and Computational Fluid Dynamic (CFD) simulations were carried out in the framework of the European Project RECORD and on its follow-up. Measurements considering burner-representative temperature perturbations injected upstream of an un-cooled high-pressure gas turbine stage were performed in the high-speed closed-loop test-rig of the Politecnico di Milano (Italy). The hot streaks were injected in streamwise direction at the stage inlet in four different circumferential positions with respect to the stator blade. They feature a 20% over-temperature with respect to the main flow. Detailed temperature measurements as well as unsteady aerodynamic measurements upstream and downstream of the blade rows were performed. Time-accurate CFD simulations of the flow upstream and within the turbine stage were performed with the TRAF code, developed by the University of Florence. Measurements show a relevant attenuation of hot streaks throughout their transport within the stator and the rotor blade rows, highly depending on the injection azimuthal position. The perturbations were observed to lose their spatial coherence, especially in the transport within the rotor, and to undergo severe spanwise migration. Simulations exhibit a good agreement with the experiments on the measurement planes and allow tracking the complex flow phenomena occurring within the blade rows. Finally the aerodynamic and thermal implications of the inlet temperature perturbations are properly highlighted and discussed.