bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Wake Control Approach for Power Generation Improvement of Three Wind Turbines in a Wind Farm
Authors: Erfanian Nakhchi Toosi Mahdi , Rahmati Mohammad 
Published: October 2022

Abstract
The total power generation of a wind farm is significantly affected by the adverse wake generation of upstream wind turbines on the aerodynamic performance of the downstream wind turbines. This paper aims to provide a novel hybrid wake control strategy to improve the power generation of horizontal-axis wind turbines in a wind-farm layout. A numerical simulation based on the actuator line method with large eddy simulation (ALM-LES) is performed to investigate the airflow around three-dimensional NREL 5MW turbines in a three-by-one layout. The yaw angle (θ) and tilt angle (ϕ) of the wind turbines are in the range of (−30° &lt; θ &lt; 30°) and (0 &lt; ϕ &lt; 35°), respectively. Firstly, the combined effects of yaw-control and tilt-control methods on the velocity profile, vorticity generation and turbulent kinetic energy in the wake region of the multiscale wind farm are investigated. Afterwards, the total power generation of the wind farm is compared with previous wake control methods of wind turbines. It was observed that the proposed hybrid wake control method could improve the total power generation by 9.94% compared to the previous wind turbine wake control techniques. The hybrid control strategy can deviate the wake much better than typical single-control methods. An optimization analysis is also provided to find the most appropriate yaw angles and tilt angles of the wind turbines subject to varying wind speeds.
Effect of Outlet Boundary Condition on the Acoustic Mode Shape and Flame Dynamics of a Partially Premixed Swirl Stabilised Combustor
Authors: Sreedeep Sharan , Ramanan Vikram , Chakraborty Aritra , Chakravarthy Satyanarayanan R. 
Published: October 2022

Abstract
Industrial gas turbines commonly use lean premixed swirl stabilised combustors that are prone to thermo-acoustic instabilities. Combustor testing involves several steps ranging from atmospheric to high-pressure conditions. An open outlet boundary condition is maintained for atmospheric tests commonly, whereas high-pressure testing involves complex exit boundary conditions, which changes the reflection coefficient and can affect the nature of instability. Current work aims at studying how the change in outlet boundary affects the nature of instability due to changes in the exit reflection coefficient and acoustic mode shape inside the combustor. A laboratory-scale industrial swirl burner that uses partially premixed methane and air at atmospheric conditions is analysed for this purpose. A constant area contraction ratio of 6.5:1 is maintained at the exit of the combustor while varying the inlet Reynolds number at a constant global equivalence ratio. Flame dynamics based on conditionally phase averaged OH* chemiluminescence images and spatial Rayleigh index maps were used to compare different flowrate and exit boundary cases. The outlet contraction affects both the frequency and amplitude of the dominant thermoacoustic mode. The orifice plate at the exit reduces the outlet reflection coefficient leading to a change in acoustic mode shape inside the combustor. Overall, the instability amplitude is reduced considerably for cases with orifice plate at the exit boundary compared to open exit boundary cases. The results show the importance of defining outlet boundary condition as a parameter in combustion instability studies. Care should be taken while comparing and interpreting results from different facilities where outlet boundary condition is different.
Design of a 2 MW Molten Salt Driven Supercritical CO2 Cycle and Turbomachinery for the SOLARSCO2OL Demonstration Project
Authors: Guédez Rafael , Barberis Stefano , Maccarini Simone , López-Román Anton , Milani Alberto , Pesatori Emanuel , Oyarzábal Unai , Sánchez Alvaro 
Published: October 2022

Abstract
Supercritical CO2 (sCO2) power cycles have been identified as technology enablers for increasing the cost-competitiveness of Concentrating Solar Power (CSP) plants. Compared to steam cycles, sCO2 cycles have the advantage of allowing higher inlet turbine temperatures, while also deploying turbomachinery that can be a ten-fold more compact. Ongoing research in CSP focuses mainly in developing new receiver and storage concepts able to withstand such required higher temperatures, alongside new heat exchangers that enable coupling to a sCO2 cycle. Meanwhile, advancements in sCO2 turbomachinery have taken place in research projects aimed at investigating the technical feasibility of the cycle, including the optimized design of its individual components and new cycle configurations. Among these, only few focus in demonstrating a full-integrated system, including cycle control and dynamics, and only two worldwide have started plans for MW-scale pilots, none of them in Europe. The EU-funded SOLARSCO2OL project aims at demonstrating a first-of-a-kind 2 MW gross simple-recuperated sCO2 Brayton cycle driven by heat provided by molten salts similar to those deployed in commercial CSP plants, which are able to operate at temperatures of up to 580°C. This paper introduces the project objectives and implementation plan, to then focus primarily on the results derived from the first year in specific relation to the conceptual design of each of 2 MW scale power cycle and its key components, including also the proposed integration and operational regimes, expected thermodynamic performance at nominal point, and up-scaling considerations.
Effusion Cooling: Influence of Pressure Drop
Authors: Bonds Michael , Wahls Benjamin H. , Ekkad Srinath V. , Rudrapatna Nagaraja , Dudebout Rudy , Meyer Ryan 
Published: October 2022

Abstract
Combustor liners are exposed to significant thermal gradients with hot combustion gases on one side and compressor directed cooling air on the other side. To maintain effective life of the liners, development of effective methods to cool gas turbine combustor liners are a necessity. Effusion cooling uses uniformly spaced holes distributed throughout the surface of the combustor liner to introduce convective and film cooling to form a protective layer of coolant along the liner wall and hence reduce the impact of the combustion gases. This experimental study investigates the overall cooling effectiveness of effusion cooling under realistic crossflow coolant operating conditions. The primary factors influencing the coolant mass flow that passed through the liner into the hot main flow was hole geometry, coolant and main flow speed, and pressure drop. For this study, 4 different effusion cooling liners with increasing levels of hole density were studied. Each hole had a length to diameter ratio (L/D) of 5.8. Non-dimensionalized hole to hole spacing in the streamwise (x/D) and spanwise (y/D) direction was equal and included spacings 7.9, 11.2, 15.8, and 22.5. These configurations were tested at uniform hot side and cold side flow speeds of 7 m/s and 15 m/s with both co-flow and counter-flow coolant directions. Pressure drop through the plate was set to 2% and 4% for 7 m/s flow speed and 4% for the 15 m/s condition. Infrared Thermography (IRT) was utilized to capture hot side and cold side liner steady state temperatures. Overall, co-flow conditions resulted in higher coolant mass flow passing through the liner while counter-flow conditions increased performance. The highest hole density configuration had a 20.3% average increase in performance over the next best performing liner geometry. In addition, the highest percentage of air passed through the effusion plate liners at the lower flow rate conditions with a 4% pressure drop. Based upon the experiments done, it was clear that while multiple factors influenced the overall cooling performance of combustor liners, a higher pressure drop consistently resulted in increased performance while higher flow speed resulted in reduced overall cooling performance.
High-Fuel Loading Ignition Delay Time Characterization of Hydrogen/Natural Gas/Ammonia at Gas Turbine-Relevant Conditions Inside a High-Pressure Shock Tube
Authors: Pierro Michael , Urso Justin , Kinney Cory , Kesharwani Shubham , McGaunn Jonathan , Dennis Christopher , Vasu Subith S. 
Published: October 2022

Abstract
This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H2 mixed with natural gas (NG) as well as mixtures of H2 and NH3 at temperatures and pressures relevant to turbine operating conditions (20–30 bar, 1000–1500 K). Lower temperatures (below 1070 K) exhibit preignition characteristics due to non-homogeneity. An attempt to mitigate these occurrences at high pressures is investigated using the constrained reaction volume (CRV) stage-filling technique. Due to the need to further refine the facility CRV stage-filling uncertainty, only higher temperature data will be interpreted at this time. The test conditions in this study closely replicate the temperatures, pressures, and mixtures that would be seen in hydrogen-powered gas turbines, making it the first to explore such conditions. The experimental IDTs were compared against the current state-of-the-art chemical kinetic models for mechanism validation. The current work will advance H2-powered turbines and aims to determine the optimum molecular ratio of H2 when mixed with natural gas.
Emission Characteristics of Aviation Kerosene Combustion Under Near-Critical and Supercritical Fuel Injections
Authors: Yang Yue , Xue Xin , Hui Xin , Tan Yaxin , Wei Wei , Liu Cheng , Lin Yuzhen 
Published: October 2022

Abstract
The emission characteristics of a model centrally staged lean premixed prevaporized (LPP) combustor was investigated under near-critical and supercritical main fuel injections. The Chinese aviation kerosene, RP-3, with its critical temperature and pressure of 651 K and 2.35 MPa, was preheated from 500 to 740 K and pressurized from 2.0 to 3.5 MPa before being injected into the combustor. The combustor liner consists of ceramic matrix composites (CMC), which are installed on a water-cooling frame. Therefore, the combustor features a high dome air ratio (95% of the total air) by removing both primary and dilution holes and redirecting the liner cooling air to the dome. The overall fuel-to-air ratio was varied from 0.030 to 0.053. The emissions at the combustor outlet were measured at various operating conditions in the range of inlet air temperatures from 600 to 840 K and pressures from 2.0 to 2.8 MPa. The results showed that EINOx decreases about 40% as the injection temperature increase from 500 K to 740 K at 2.0 to 2.4 MPa injection pressure. It indicates that the transition from liquid fuel to supercritical fuel drastically reduces fuel density and surface tension. Increasing injection fuel temperature significantly improves the fuel/air mixing and avoids hot spot formation that favors NOx formation. Both EICO and EIUHC decrease slightly with increasing fuel injection temperature, suggesting a weak relation between the combustion efficiency and fuel thermodynamic state. The finding of the current study suggests that the NOx emissions are affected by the premixing quality of the main injector and may be reduced by injecting supercritical kerosene.
On the Mode Characteristics of Rotating Instability With Different Tip Clearances
Authors: Yang Zeyuan , Ming Lele , Wu Si , Wu Yadong , Tian Jie , Ouyang Hua 
Published: October 2022

Abstract
Rotating Instability (RI) is an unsteady aerodynamic phenomenon occurring at off-design conditions in axial compressors, featuring side-by-side peaks below the blade passing frequency (BPF) in pressure spectra. Especially when the mode orders of RI are close to the blade number the interaction effect could generate intense tip clearance noise, which could not be cut-off by the duct. Moreover, RI is regarded as a potential indicator for stall and surge. According to previous studies the mechanism of RI could be classified as the unsteady vortex system theory and the shear layer instability theory. This paper presents an experiment in a low-pressure single-rotor compressor, comparing the RI characteristics with two different tip clearances at different operating conditions. A total of 28 Kulite transducers were circumferentially mounted on the casing wall to measure the pressure fluctuation in the two configurations. Utilizing the compressive sensing (CS) method based on the double-uniform sampling point (DUSP) technique the mode orders of RI could be accurately determined. Through throttling the RI phenomenon was observed in different range of flow rates under both tip clearance configurations. The evolution pattern of RI is profoundly affected by the tip clearance size, i.e., the RI phenomenon only presents a two-stage “strengthen-weaken” pattern with the nominal gap, while shows a three-stage “strengthen-weaken-strengthen” pattern with the larger gap. Moreover, the mode characteristics of RI in the frequency domain are analyzed. Based on the experimental results several discussions on the mechanism of RI are proposed. These findings do not conform with the unsteady vortex system theory, but provides evidence for the shear layer instability theory.
Calibrated Rotation-Helicity-Quadratic Constitutive Relation Spalart-Allmaras (R-H-QCR SA) Model for the Prediction of Multi-Stage Compressor Characteristics
Authors: Matsui Kotaro , Tani Naoki , Perez Ethan , Kelly Ryan T. , Jemcov Aleksandar 
Published: October 2022

Abstract
Compressor performance prediction is still one of the significant interests in the turbomachinery research field. The two critical parameters for compressor design are adiabatic efficiency and stability margin. The Spalart-Allmaras (SA) turbulence model and modified SA models are widely used in that design process. However, the prediction accuracy is not always satisfactory. In most cases, the SA model predicts larger stall mass flow, and the RC-QCR SA model underestimates efficiency. This study proposes a new combination of the modified SA model (R-H-QCR model). R-H-QCR stands for Rotation-Helicity-Quadratic constitutive relation. The model increases or decreases turbulent viscosity based on flow rotation, energy backscatter, and anisotropy of turbulence flow field. The Bayesian inference framework calibrates the model parameters to predict accurately both efficiency and stability in the 3.5 stage compressor. The R-H-QCR, RC-QCR, and default SA models are evaluated in the multi-stage compressor. For the performance prediction, the R-H-QCR model predicts a better stability margin than the SA model and better efficiency than the RC-QCR model. In addition, the spanwise distribution of normalized total pressure is well captured by the R-H-QCR model, indicating that the R-H-QCR model improves flow field prediction.
Experimental and Numerical Advancement of the MGT Combustor Towards Higher Hydrogen Capabilities
Authors: Ćosić Bernhard , Wassmer Dominik , Kluß David , Jaeschke Alexander , Reichel Thoralf , Paschereit Christian Oliver 
Published: October 2022

Abstract
Blending of natural gas with hydrogen is a viable pathway for the decarbonization of industrial gas turbines for combined heat and power applications. Very high blending ratios of hydrogen are needed to achieve significant CO2 emission reductions. However, burning high hydrogen contents in the gas turbine is challenging in terms of NOx emissions and the mitigation of flashback risks as well as suppressing thermoacoustic instabilities. This paper illustrates a design modification to improve the hydrogen capabilities of the Advanced Can Combustion (ACC) system and its ultra-low emission industrial swirl burner for the MGT6000 gas turbine that was originally designed for pure natural gas combustion. A flow conditioner is installed upstream of the swirler aiming to decrease the fuel amount close to the combustor walls and thereby increase the flashback resistance of the burner. High pressure (≈14bar) full power (≈4MWth) single can combustion tests and atmospheric burner tests are used for the assessment of the hydrogen capabilities for the original and the retrofitted burner. Different levels of hydrogen blending of up to 45 vol-% at high pressure and 93 vol-% at atmospheric conditions as well as different gas turbine relevant flame temperatures are assessed in terms of emissions, flame flashback and thermoacoustic stability. Low speed thermocouple measurements at the burner walls are identified as a good precursor for hydrogen induced flame flashback at the walls. The amplitude of the thermocouple fluctuation is observed to be similar for atmospheric and elevated pressure. Moreover, it is shown that the increase in NOx emissions associated to hydrogen blending can be transferred from atmospheric conditions to elevated pressure. The experimental dataset is used for the calibration of Computational Fluid Dynamics (CFD) calculations to allow for the assessment at different operating conditions and future modifications. The CFD is focused on the prediction of flashback resistance for different blends of hydrogen and natural gas at high pressure conditions.
Multi Operating Point Aerodynamic Optimization of a Radial Compressor Impeller for an Application in High Temperature Heat Pump
Authors: Schaffrath Robert , Kriese Maximilian , Kajasa Bojan , Köhler Martino , Nicke Eberhard , Voß Christian 
Published: October 2022

Abstract
The decarbonization of production processes plays an important role on the way to environmentally friendly economy. Especially, the implementation of high temperature heat pumps (HTHP) offers a great potential to replace fossil fuel-based energy infrastructure. A major issue for the introduction of HTHP is the initial cost and regarding the payback period. However, there is still potential in increasing the coeffcient of performance (COP) of HTHP for the economic integration in existing industrial processes. One important possibility is the dedicated development and design of turbocompressors for this application and the planned heat transfer medium including the aerodynamic optimization of compressor geometry. Against this background an automated aerodynamic optimization method for radial compressor blade geometry for superheated steam is presented. The optimization refers to two different operating points of the HTHP and focuses on maximizing the isentropic efficiency of the impeller geometry as well as the pressure ratio. The algorithm is accelerated by data-driven metamodels and is implemented in a high-performance cluster environment. The boundary condition of the inherent computational fluid dynamics (CFD) calculation comes from the thermodynamic cycle calculation of the whole HTHP system. A two-stage compression with intercooling between the compressor stages are foreseen. Our approach shows an increment of both objective functions in both operating points and the satisfaction of further side conditions for the low pressure compressor (LPC). Furthermore, it results in an increment of 5 percent points of isentropic efficiency and 13 percent points of static to total pressure ratio in comparison to our initial geometry. These impeller optimizations result in a COP increment of 5 percent. The resulting geometry will be interpreted in the context of aerodynamic behavior. Based on that results additionally, a flow-cut optimization for the high pressure compressor (HPC) is given and evaluated. The results are comparable to aerodynamic optimization in different research fields like aircraft engines or stationary gas turbines and contribute to optimized multistage compressor design for HTHP.
Aerodynamic Noise Characteristics of Axial Flow Fan in Narrow Space and Noise Reduction Based on Flow Control
Authors: Sun Zonghan , Chai Pengfei , Tian Jie , Du Zhaohui , Ouyang Hua 
Published: October 2022

Abstract
The aeroacoustic characteristics of a power module in the electric vehicle charging pile is studied by experimental and numerical methods. In the free field, a single cooling fan mainly emits tonal noise, while the far-field noise of fans in parallel satisfied the superposition of incoherent sound sources. However, when two fans in parallel delivered air into the power module, the noise increased significantly, especially broadband noise. Referring to the power module, a narrow space model with cooling fan supplying air inward is constructed. The computational fluid dynamics (CFD) results show that the mass flow rate of the fan is reduced due to the obstacles downstream, which weakens the heat dissipation performance. Part of the fluid forms reflux, interacts with the fan and strengthens the corner vortex. By setting guide holes on the casing near the flow blockage to arrange flow, the flow resistance is reduced and the total mass flow rate of the fan is increased by 2.5%. The reflux and corner vortex are dispersed, and the vortices develop downstream, thus reducing the interaction with the fan. The predicted tonal sound pressure level (SPL) decreases by 3.2 dBA based on acoustic analogy method. The broadband noise caused by shedding vortex is also predicted and discussed by a semi-empirical model. In the noise reduction experiment of the real power module, combining inlet bellmouth on the fan and guide holes on the casing, the total SPL was significantly reduced by 2.9 dBA. Especially, based on bellmouth, guide holes brought an additional 1.9 dBA tonal noise reduction and 1.0 dBA total SPL reduction. The study indicates that appropriate flow control is important to improve the heat dissipation and reduce noise of the power module. These results are helpful to develop higher power charging system.
Numerical Investigation of Near-Tip Modifications for a Highly-Loaded Low-Speed Rotor Under the Influence of Double Leakage
Authors: Eckel Jannik , von Jeinsen Philipp , Gümmer Volker 
Published: October 2022

Abstract
This paper numerically investigates the flow field in the tip region of a highly-loaded axial low-speed compressor rotor. The rotor in focus is of a hybrid blade configuration, featuring a tandem profile in the mid-span region and single blade profiles near the endwalls. The simulated 1.5-stage configuration also consists of a single row IGV and a tandem stator. Due to high loading coefficients (ψ = 0.58) in combination with moderate flow coefficients (φ = 0.58), double leakage of the tip leakage vortex plays a major role at all operating conditions. As already shown in the past, double leakage is a stability influencing dominant flow phenomenon in compressor rotors and influencing that can be the key to an efficient working range enhancement on compressor stages. This work introduces a simple and powerful method of enhancing the working range for low-speed rotors under the influence of double leakage. It is shown, that modifications to the pressure side shape of rotor tip profiles can influence the interaction of the tip leakage vortex with the adjacent blade, comparable to the effects of casing treatments. These unconventional blade shapes result from the transformations from tandem blade configurations to hybrid blades near the endwalls, as Eckel et al. have shown [1]. The resulting single blade profile close to the tip features a convex profile element (an increase in local thickness, called the -“belly”), which significantly influences the local static pressure gradients. This unusual pressure-side profiling can change mass flow over the tip and, by correct positioning, may reduce the amount of double leakage and, consequently, increase the rotors efficient working range. This work presents the geometry definitions for the hybrid blade single-segments, a detailed analysis of the impact on design and off-design operating conditions together with their underlying flow phenomena, and finally proposes design guidelines for the blade-tip geometries of highly-loaded rotors under the influence of double leakage.