bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Comparison of Static and Rotordynamic Characteristics for a Grooved-Stator/Smooth-Rotor and a Smooth-Stator/Grooved-Rotor Liquid Annular Seals
Authors: Li Zhigang , Fang Zhi , Li Jun , Feng Zhenping 
Published: November 2019

Abstract
Liquid annular seals with parallelly-grooved stator or rotor are used as replacements for smooth plain seals in centrifugal pumps to reduce leakage and break up contaminants within the working fluid. Parallelly-grooved liquid annular seals have advantages of less leakage and smaller possibility of abrasion when the seal rotor-stator rubs in comparison to smooth plain seals. This paper deals with the static and rotordynamic characteristics of parallelly-grooved liquid annular seals, which are limited in the literature.
Numerical results of leakage flow rates, drag powers and rotordynamic force coefficients were presented and compared for a grooved-stator/smooth-rotor (GS-SR) liquid annular seal and a smooth-stator/grooved-rotor (SS-GR) liquid annular seal, utilizing a modified transient CFD-based perturbation approach based on the multiple-frequency elliptical-orbit rotor whirling model. Both liquid annular seals have identical seal axial length, rotor diameter, sealing clearance, groove number and geometry. The present transient CFD-based perturbation method was adequately validated based on the published experiment data of leakage flow rates and frequency-independent rotordynamic force coefficients for the GS-SR and SS-GR liquid annular seals at various pressure drops with differential inlet preswirl ratios. Simulations were performed at three pressure drops (4.14 bar, 6.21 bar, 8.27 bar), three rotational speeds (2 krpm, 4 krpm, 6 krpm) and three inlet preswirl ratios (0, 0.5, 1.0), applying a wide rotor whirling frequency range up to 200 Hz, to analyze and compare the influences of operation conditions on the static and rotordynamic characteristics for both the GS-SR and SS-GR liquid annular seals. Results show that the present two liquid annular seals possess similar sealing capability, and the SS-GR seal produces a slightly larger (∼ 2–10%) drag power loss than the GS-SR seal. For small rotor whirling motion around a centered position, both seals have the identical direct force coefficients and the equal-magnitude opposite-sign cross-coupling force coefficients in the orthogonal directions x and y.
For all operation conditions, both the GS-SR and SS-GR liquid annular seals possess negative direct stiffness K and positive direct damping C. The GS-SR seal produces purely positive Ceff throughout the whirling frequency range for all operation conditions, while Ceff for the SS-GR seal shows a significant decrease and transitions to negative value at the crossover frequency fco with increasing rotational speed and inlet preswirl. From a rotordynamic viewpoint, the GS-SR liquid annular seal is a better seal concept for pumps.
Transient Analysis of Rotating Stall Development in a Centrifugal Compressor With Vaned Diffuser
Authors: Fujisawa Nobumichi , Takahashi Masaki , Ohta Yutaka 
Published: November 2019

Abstract
The transient process of the rotating stall development in a centrifugal compressor with a vaned diffuser was investigated by experimental and numerical analyses. Previous studies show that a diffuser stall triggers a stage stall, which rotates through rotor and stator passages. The vortex evolution at the diffuser throat represents the key factor in diffuser stall development. The developed diffuser stall cell blocked the impeller exit, causing an impeller passage stall. This paper focused on two aspects regarding the transient process of the diffuser stall development. The first aspect is the process by which the vortex at the diffuser throat near the hub side, develops in the circumferential direction. Secondly, we investigated the mechanism of the diffuser stall expansion into impeller passages. The transient analysis of the diffuser stall development was conducted experimentally and numerically by closing the throttle valve abruptly. The hub side blockage was initiated near the cutoff by the strong adverse pressure gradient in the diffuser throat area. Therefore, the key factor in the diffuser stall evolution was the development of a throat blockage near the cutoff, obtained from both experimental and computational fluid dynamics results. Furthermore, the transient stall cell blocked the impeller passages and induced a hub side blockage at the throat of the impeller passages and the impeller leading edge separation. The pressure surface separation of the impeller at the trailing edge had a great impact on the development of the stall cell within impeller passages.
Rotordynamic Characteristics Prediction for Hole-Pattern Seals Using CFD
Authors: Thorat Manish R. , Hardin James R. 
Published: November 2019

Abstract
The experimental set-up for a hole-pattern seal is modeled using CFD and results compared with measured test data and bulk flow model (ISOTSEAL) predictions. The inlet swirl boundary condition for prior CFD analyses of this test case have either been assumed or based on pitot-tube measurements. In this paper, the validity of each is investigated by including radial inlet nozzles with the inlet plenum in the model geometry.
A transient mesh deformation technique with multiple frequency journal excitations is used to determine frequency dependent rotordynamic coefficients. This multi-frequency excitation method is validated against single frequency sinusoidal journal excitation. An empirical limit on the number of frequencies that can be packed in a multi-frequency excitation signal to provide a reasonable estimate of rotordynamic coefficients is provided.
Rotordynamic coefficients estimated using CFD compare well with measured rotordynamic coefficients. For the given test data, the ISOTSEAL bulk flow model does not provide good correlation for cross-coupled stiffness if the measured swirl ratio at the inlet of the seal is used in the prediction. However, improvement in correlation for cross-coupled stiffness is obtained if the swirl ratio found from CFD analysis is used in the bulk flow model, indicating that pitot-tube measurements of swirl may not be accurate.
Numerical Investigation on Sand Particles Deposition in a U-Bend Ribbed Internal Cooling Passage of Turbine Blade
Authors: Li Lin , Liu Cun-liang , Shi Xiao-Yu , Zhu Hui-ren , Li Bing-ran 
Published: November 2019

Abstract
Sand particles impinge the internal cooling passage of the turbine blade and easily deposit, which lead to the decrease of cooling efficiency of the turbine blade and the increase of turbine blade temperature. In order to explore sand particles deposition mechanism in the internal cooling passage of turbine blades, the numerical simulation was performed in a U-bend passage with rib turbulators by means of a commercial CFD code. The fluid phase was modelled employing Reynolds-averaged Navier-Stokes approach. The discrete phase was solved using Lagrangian particle tracking method and a continuous random walk model. A particle deposition model was implemented using user-defined functions. The Reynolds numbers of 30000, 23000 and 15500 are considered. Particles sizes in the range 1–20 microns are considered. Results show that the particles deposition flux decreases gradually along the flow direction. The particles significantly deposit on the rib wall and the bend wall, especially on the windward rib wall and the upstream wall of the bend, with less deposition on the leeward rib wall. This is because the rib wall hinders the movement of fluid and sand particles impact the wall due to inertia, which lead to the energy loss. The particles deposition flux on the windward rib wall increases with the increase of Reynolds number and particles diameter, while the deposition flux on the leeward rib wall decreases. With the increase of the particles diameter, the particles deposition flux increases. The deposition rate increases with the increase of Reynolds number and particles diameter.
Performance of Public Film Cooling Geometries Produced Through Additive Manufacturing
Authors: Snyder Jacob C. , Thole Karen A. 
Published: November 2019

Abstract
Film cooling is an essential cooling technology to allow modern gas turbines to operate at high temperatures. For years, researchers in this community have worked to improve the effectiveness of film cooling configurations by maximizing the coolant coverage and minimizing the heat flux from the hot gas into the part. Working towards this goal has generated many promising film cooling concepts with unique shapes and configurations. However, until recently, many of these designs were challenging to manufacture in actual turbine hardware due to limitations with legacy manufacturing methods. Now, with the advances in additive manufacturing, it is possible to create turbine parts using high temperature nickel alloys that feature detailed and unique geometry features. Armed with this new manufacturing power, this study aims to build and test the promising designs from the public literature that were previously difficult or impossible to implement.
In this study, different cooling hole designs were manufactured in test coupons using a laser powder bed fusion process. Each nickel alloy coupon featured a single row of engine scale cooling holes, fed by a micro-channel. To evaluate performance, the overall cooling effectiveness of each coupon was measured using a matched Biot test at engine relevant conditions. The results showed that certain hole shapes are better suited for additive manufacturing than others, and that the manufacturing process can cause significant deviations from the performance reported in literature.
Experimental Comparison of Two Integer Valued Iterative Learning Control Approaches at a Stator Cascade
Authors: Arnold Florian , Neuhäuser Karl , King Rudibert 
Published: November 2019

Abstract
Experimental and simulative investigations have shown that Active Flow Control is an effective method to influence flow conditions within a compressor. This can be used for different cases like mitigating flow separation or to ensure a uniform flow throughout a compressor stage. Control performance can be improved by making use of a cyclic character found in the rotor/stator interaction or found in new gas turbine setups exploiting cycling combustion. To this end, Iterative Learning Control (ILC) is applied.
To achieve a fast actuation, irrespective of the implemented control method, solenoid valves should be installed instead of proportional valves. Unfortunately, the binary character of these valves does not allow the application of a conventional control methods, e.g., real-valued ILC.
This contribution presents two options to handle the binary control domain in the context of an ILC. Both approaches are tested in a simulation study first to analyze the behavior. Then they are applied to a real test rig featuring a linear stator cascade.
Validation of Lifetime Models for Recuperator Foils Through Long-Term Laboratory and Engine Testing
Authors: Dryepondt Sebastien , Pint Bruce A. 
Published: November 2019

Abstract
For the next-generation of turbine-based combined heat & power (CHP) systems, materials development can enable lower costs and higher efficiency, particularly for alloy foils used in the recuperator. To quantify the potential benefits, lifetime models are being developed for current chromia-forming alloys such as 625, 120, 310 and 709 (also called 2025Nb) as well as new alumina-forming austenitic (AFA) steels, which are much more oxidation resistant in exhaust gas. A combination of long-term laboratory (up to 30 kh) and field exposure data (up to 100 kh) are being used to develop and validate the model for operation at 650°–800°C.
Research on the Heat Insulation Performance of Advanced Thermal Barrier Coatings Based on Dense Vertical Cracked Structure
Authors: Long Yun , Wang Yuzhang , Zhao Mengtian , Weng Yiwu 
Published: November 2019

Abstract
The Thermal barrier coatings (TBCs) applied to gas turbine can effectively protect the metallic components from overheating. It makes contribution to raising turbine entry temperatures, which can improve the cycle thermal efficiency of turbine and prolong its service life. To understand the failure mechanism of TBCs and extend its lifetime, it is vital to prepare TBCs with excellent heat insulating performance. TBCs with dense vertical cracked structure is an essential kind of advanced thermal barrier coatings and has received great attention recently. However, most studies are based on laboratory-scale, since the complex coating preparation process makes it challenging to obtain the controllable microstructure distribution of the coating. Moreover, the thin slices of TBCs are difficult to get during the reconstruction process of the coating microstructure. Therefore, in this work, an optimized numerical reconstruction method of TBCs was applied to obtaining the TBCs with dense vertical cracked structure. The influences of the microstructural TBCs with different numbers of vertical cracks as well as different length and width of vertical cracks were herein discussed, together with the analysis by the developed numerical calculation program based on the lattice Boltzmann method (LBM). The results showed that the performance of heat insulation in dense vertical cracked coatings was improved as the characteristic network structure. Meanwhile, it indicated that the optimal heat insulation performance can get when the length and width of vertical cracks were around 125μm, 15μm respectively. The results can play a guiding role in choosing and designing the turbine blades for further development of gas turbines.
Test Rig Commissioning for Advanced Rotor-Stator Seals
Authors: Trivedi Deepak , Ruggiero Eric , Wolfe Christopher , Kirk Joel , Williams John , Graham James 
Published: November 2019

Abstract
Test facilities capable of simulating relevant operational environments for validating novel concepts are indispensable for advancing the state-of-the-art in turbomachinery sealing technology. A test rig suitable for demonstrating full-scale rotor-stator sealing concepts under operational environments relevant for a variety of turbomachinery gas paths was designed and commissioned at GE’s Seals Test Facility. The test rig, called the Advanced Seals Test Rig (or ASTR), can simulate conditions that include a range of rotor speeds, fluid pressures and temperatures, from steady state operating conditions of high pressure turbines of aircraft engines to sections of steam turbines.
The present paper provides a system level description of the test rig. The main test section of the rig is housed within the centerpiece of a stamped pressure vessel. A drive train penetrates the pressure vessel and consists of an integral saddle mounted rotor. A motor connected to a high-speed gearbox through couplings on each end permits rotation of the test rotor. The test rotor is supported by two bearing pedestals. The paper describes these rig subsystems with focus on novel features for ease of operation. Key instrumentation and operating procedures that enable the rig to operate safely are also described. Key drivers of the rig design, such as test requirements, rotordynamics, mechanical design, ergonomics, safety and test productivity are outlined. Mechanical design considerations include strict requirements for thermal and pressure deformation under demanding conditions of pressure and temperature. Commissioning of the rig included phases of fabrication, installation, shakeout, calibration and benchmarking. Key learnings from the rig design and commissioning process, as well as operations, are summarized.
High Fidelity Simulation of Fluid-Structure Interaction in a 1½ Stage Axial Turbine
Authors: Zorn Joshua , Davis Roger , Clark John 
Published: November 2019

Abstract
A high fidelity, fully coupled numerical technique for the simulation of airfoil and turbomachinery aeroelasticity configurations is presented. The unsteady structural and fluid dynamics equations are discretized by a control volume technique which is second order accurate in space along with a dual time-step scheme that is second order accurate in time. The momentum conservation equation for the solid is written in terms of the Piola-Kirchoff stresses and the displacement velocity components. The stress tensor is related to the Lagrangian strain and displacement tensors using the St. Venant-Kirchoff constitutive relationship. Source terms at the surface of the solid are included to account for surface pressure and body forces. Previous fluid-structure interaction studies of Turek’s cylinder flag and the AGARD 445.6 airfoil have provided confidence needed to accurately perform fluid structure interaction simulations in turbomachinery. In this study, a 1½ stage axial transonic turbine is simulated and results are validated with experimental data. Simulation results indicate that the inclusion of airfoil vibration leads to improved agreement with experimental unsteady surface pressures compared to simulations with fixed airfoils.
Design of High Specific Speed Mixed Flow Micro-Compressor for Co-Flow Jet Actuators
Authors: Xu Kewei , Zha Gecheng 
Published: November 2019

Abstract
This paper conducts aerodynamic design of a high specific speed mixed flow micro-compressor used as an actuator for Co-flow Jet (CFJ) Active Flow Control (AFC) airfoil. The aerodynamic design poses several challenges, including: 1) Small size with very low Reynolds number; 2) High specific speed for mixed-flow compressor due to high mass flow rate and low total pressure ratio; 3) Static pressure ratio lower than 1 to match the low pressure of CFJ airfoil leading edge (LE) suction peak.
The numerical design approach is validated with a mixed flow micro-compressor with very good agreement between the predicted performance and the measured data. Front loaded rotor blade work distribution is adopted to decrease boundary layer loss at the blade surface. Free vortex work distribution is applied for the rotor span to reduce spanwise mixing loss. The rotor efficiency achieved by the numerical prediction is 91.7%. Significant loss is observed downstream of the rotor when the flow reaches the stator and the outlet guide vane (OGV). For the stator, it is found that an inlet and outlet flow path area ratio of 1.05 achieves a very high total pressure recovery of 99.29%. A very good stage isentropic efficiency of 84.3% is achieved. The final design of micro-compressor achieves a flow coefficient of 0.3 at the design point with a total pressure ratio of 1.117 and a static pressure ratio of 0.987. A structure FEM analysis indicates that the rotor blades satisfy the structure strength and modal frequency requirement.
Effects of Varying Liquid Fuel and Air Co-Flow Rates on Spray Characterisation of an Annular Co-Flow Spray Burner
Authors: Alsulami R. A. , Nates S. , Wang W. , Won S. H. , Windom Bret 
Published: November 2019

Abstract
Development of efficient and clean combustion systems requires the understanding of all the processes experienced by a complex liquid fuel in IC engines, such as atomization, vaporization, turbulent mixing, and combustion. Many of these processes are interconnected; the atomization process, which leads to various droplet sizes can enhance or diminish the vaporization rate of the liquid fuel and consequently impact the energy conversion process. Furthermore, the combustion/flame stability of liquid-fueled gas turbine can be influenced by the fuel and the air co-flow rates delivered in the engine. Increasing the fuel and/or air flow rates can enhance droplet breakup and the turbulence of the flow, and as a result sway the droplet size distribution of the spray. This work focuses on investigating the impact of varying the fuel and air flow rates on the spray atomization (e.g. droplet size distribution) of an Annular Co-Flow Spray Burner. This was explored by measuring droplet sizes and velocities of the spray at different radial and axial positions of n-heptane fuel under nonreacting conditions. In addition, the turbulence intensity and the liquid spray droplet distribution were quantified for different fuel and air flow rate conditions. The measurements were obtained by using a Phase Doppler Particle Analyzer/Laser Doppler Velocimeter (PDPA/LDV) at P = 1 atm and T = 298 K. Moreover, the Sauter Mean Diameters for different flow conditions are predicted, using an established correlations, and compared to PDPA/LDV measurements. The results provided a fair understanding of the influence of varying the fuel and air flow rates on the droplet sizes, velocity, and turbulent intensity. Furthermore, the results presented here will support future work that will focus on unraveling the role of phase change on flame stability.
Automatic Gas Turbine Matching Scheme Adaptation for Robust GPA Diagnostics
Authors: Stenfelt Mikael , Zaccaria Valentina , Kyprianidis Konstantinos G. 
Published: November 2019

Abstract
When performing gas turbine diagnostics using Gas Path Analysis (GPA), a convenient way of extracting the degradations is by feeding the measured data from a gas turbine to a well-tuned gas turbine performance code, which in turn calculates the deltas on the chosen health parameters matching the measured inputs. For this, a set of measured parameters must be matched with suitable health parameters, such as deltas on compressor and turbine efficiency and flow capacity.
In aero engines, the number of sensors are in general limited due to cost and weight constraints and only the necessary sensors for safe engine operation are available. Some important sensors may have redundancy in case of a sensor loss but it is far from certain that this applies to all sensors available.
If a sensor malfunctions by giving false or no values, the functions using the sensor will be negatively affected in some way causing them to either synthesize a fictive measurement, changing operating scheme, going into a degraded operating mode or shutting down parts or the whole process. If an onboard diagnostic algorithm fails due to sensor faults it will lead to a decrease in flight safety, thus there is a need for a robust system.
This paper presents a strategy for automatic modifications of the gas turbine diagnostic matching scheme when sensors malfunction to ensure a robust function. When a sensor fault is detected and classified as malfunctioning, the gas turbine matching scheme is modified according to predefined rules. If possible, a redundant measurement replaces the faulty measurement. If not, the matching scheme will be modified by determining if any health parameters cannot be derived by the functional set of measurements and remove the least valuable health parameter while maintaining a working matching scheme for the remaining health parameters.