bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large Eddy Simulation of a Pistonless Constant Volume Combustor: A New Concept of Pressure Gain Combustion
Authors: Detomaso Nicola , Laera Davide , Pouech Paul , Duchaine Florent , Poinsot Thierry 
Published: October 2022

Abstract
Classical gas turbine thermodynamic cycle has undergone no change over the last decades. The most important efficiency improvements have been obtained reducing thermal losses and raising the overall pressure ratio and peak temperature. Pressure Gain Combustion (PGC) represents an increasingly interesting solution to break out current technological limits. Indeed cycle models show that a pressure raise across the combustion process would reduce the fuel consumption, increasing the efficiency. Providing an efficiency close to the corresponding detonative technological concepts, Constant Volume Combustion (CVC) represents a viable solution that still needs to be studied. In the current work, the CV2 (Constant-Volume Combustion Vessel) installed at the Pprime laboratory (France) is numerically investigated using the high-fidelity compressible Large Eddy Simulation (LES) solver AVBP. All the successive phases of the CVC cycle, i.e. air intake, fuel injection, spark-ignited combustion and exhaust, are considered in the LES. Intake and exhaust valves are properly represented by novel boundary conditions able to mimic the valves impact on the flow without the need to directly consider their presence and dynamics during the simulation, reducing the computational costs. The spark ignition is modeled as an energy deposition term added to the energy equation. The combustion phase is treated by the dynamic version of the Thickened Flame model (DTFLES) extended to deal with non-constant pressure combustion. Time-resolved Particle Imaging Velocimetry (PIV) and pressure measurement inside the chamber reveal that cold and reactive turbulent flow are well captured in all the phases, showing the reliability of the approach and the models used.
The Importance of Airfoil Selection in the Design of UAS Propellers
Authors: Van Treuren Kenneth , Wisniewski Charles 
Published: October 2022

Abstract
With the development of unmanned aircraft systems (UASs), interest in the design of propellers is growing. UASs are being used in the military for a variety of applications to include intelligence, surveillance, and reconnaissance (ISR) as well as resupply. Larger scale Urban Air Mobility (UAM) and eVTOL (electric vertical take-off and landing) vehicles are also receiving attention. Many of these systems use electric motors with a fixed pitch propeller. More efficient, quiet propellers are needed if these systems are to operate near populated areas. Selection of an appropriate airfoil is critical to satisfy these requirements.
This study proposes seven guidelines to evaluate airfoils: 1) sufficient thickness, 2) high lift coefficient, 3) high maximum lift to drag ratio, 4) broad peak at the maximum lift-to-drag ratio, 5) linear lift curve slope over propeller’s airfoil operating angle-of-attack (AOA) range, 6) low drag over the operating AOA range, and 7) selecting the appropriate Reynolds number for airfoil design aerodynamic data.
The Clark Y, GM15, GOE 225, GOE 358 and S1223 airfoils were analyzed using the selection guidelines. Propellers were designed for each airfoil using Blade Element Momentum Theory and tested in a low-speed wind tunnel. The aerodynamic performance of each propeller is reported as well as the noise generated in the near field. The GM15 required the lowest mechanical power to meet the on-design conditions of T = 2.5 lbf at a freestream velocity of 44 ft/s. This propeller also had the lowest measured peak Sound Pressure Level. While no airfoil satisfies all the selection guidelines perfectly, having an awareness of these guidelines will help with the selection of a suitable propeller airfoil for the mission and design point.
Flow Scaling Considerations for Internal Coolant Warming
Authors: Wiese Connor J. , Bryant Carol E. , Rutledge James L. 
Published: October 2022

Abstract
An increasingly common experimental technique allows measurement of overall effectiveness by matching the Biot number between experimental and engine conditions. The measured overall effectiveness distribution correlates to the actual turbine component temperature distribution. In addition to matching the Biot number, the theory also suggests that the coolant warming factor χ, must be matched. While it is clear from prior work what conditions must be met to match the Biot number of an experimental campaign to that of the engine conditions, it is often taken for granted that the coolant warming factor will also be matched. In this paper we develop the theoretical requirements necessary to match χ and test their validity through experiments performed on a conducting model of a leading edge using a variety of coolant gases to test the scaling theory with a wide range of coolant fluid properties.
Real Time mGT Performance Assessment Tool: Comprehensive Transient Behaviour Prediction With Computationally Effective Techniques
Authors: Gaitanis Aggelos , Contino Francesco , De Paepe Ward 
Published: October 2022

Abstract
Conventional centralized power generation is increasingly transforming into a more distributed structure due to the transition towards more renewable energy sources. The periodic power production that is created by the renewable production unit generate the need for small-scale heat and power units. One of the promising technologies which can assist a flexible and renewable power grid is micro Gas Turbines (mGTs). Such engines are generally considered to have an electrical power output less than 500kWe and are competent candidates for small-scale Combined Heat and Power (CHP). mGTs, as compensators for the demand fluctuations, are required to work on transient and part-load conditions. Therefore, the connection of such unit to a non-dispatchable energy system creates new research challenges.
A complete characterization of their dynamic behaviour through a real-time simulation tool is necessary to establish effective and suitable control systems. This model should predict all the crucial parameters of the engine, such as the surge margin and combustion stability, which assist in the effective performance diagnosis. Moreover, the energy transition requires the conversion of conventional mGTs to more sophisticated high-efficient cycles with the addition of extra components (saturation unit, aftercooler, etc). Consequently, a modular and computationally fast real-time tool offers an asset in the development of future advanced cycles based on the mGT concept.
This paper presents the complete development of a numerical in-house tool implemented in the Python open-source programming language for the behaviour prediction of the mGT. The fundamental target of our work is to achieve high fidelity of the simulated dynamic responses by adopting modern coding techniques that decrease the computational time. The model is validated with experimental results from the VUB Turbec T100 test rig and with additional data published in the literature. The component modeling methods are also compared to other techniques to confirm the practicality of the current code. Key benefits of this tool are the low complexity highly efficient component modules. This code reproduces the experimental results well during transient operation as the important cycle parameters present a deviation from the measurements within the range of 1.5%.
Experimental Investigation of Combustion Dynamics in a High-Pressure Liquid-Fueled Swirl Combustor
Authors: Chandh A. , Adhikari S. , Wu D. , McKinney R. , Emerson B. , Zhang Q. , Joshi D. , Sen B. , Davis D. 
Published: October 2022

Abstract
In this paper, we present combustor acoustics in a high-pressure liquid-fueled Rich burn - Quick quench - Lean burn (RQL) styled swirl combustor with two separate fuel circuits. The fuel circuits are the primary fuel (which has a pressure atomizer nozzle) and secondary fuel (which has an air blast type nozzle) circuits. The data were acquired during two dynamical regimes — combustion noise, where there is an absence of large amplitude oscillations during the unsteady combustion process, and intermittency, where there are intermittent bursts of high amplitude oscillations that appear in a near-random fashion amidst regions of aperiodic low amplitude fluctuations. This dynamic transition from combustion noise to combustion intermittency is investigated experimentally by systematically varying the fuel equivalence ratio and primary-secondary fuel splits. Typical measures such as the amplitude of oscillations cannot serve as a measure of change in the dynamics from combustion noise to intermittency due to the highly turbulent nature. Hence, recurrence plots and complex networks are used to understand the differences in the combustor acoustics and velocity data during the two different regimes. We observe that the combustor transitions from stable operation to intermittency when the equivalence ratio is increased for a given primary fuel flow rate and conversely, when the percentage secondary fuel flow rate is increased for a given equivalence ratio. The contribution of this work is to demonstrate methodologies to detect combustion instability boundaries when approaching them from the stable side in highly turbulent, noisy combustors.
Study on the Emissions Performance of a CMC Combustor With Weakly Coupled Stratified Swirl Flames at Engine-Relevant Conditions
Authors: Wei Wei , Xu Quanhong , Xue Xin , Yang Yue , Liu Cheng 
Published: October 2022

Abstract
Experimental and theoretical studies were conducted to investigate the overall emissions of CO, NOx, and UHC in a centrally staged lean premixed prevaporized (LPP) combustor featuring weakly coupled stratified swirl flames. The combustor consisting of a ceramic matrix composites (CMC) plate was run at aero engine-relevant conditions, with inlet temperatures and pressures up to 810 K and 2.2 MPa. The combustor adopted the concept of impinging cooling thanks to the heat-resistant property of CMC. The cooling air entering from the dome subsequently participated in combustion. The design of the test matrix was based on the typical operating conditions of practical LPP combustor. Without downstream cooling holes on the liner, the injector equivalence ratio was equal to global equivalence ratio of the entire combustor. The overall emissions data including EICO, EINOx, and EIUHC were obtained using a gas analyzing system under 15 different operating conditions. With a low fuel-air ratio (FAR), EINOx reached its lowest value when the pilot-to-total fuel split ratio (SR) was close to 0.13. With the increase in FAR, the main stage and pilot stage started to collectively dominate the emissions performance, eventually making the EINOx-versus-SR curve level off at a high FAR. Since the trend of CO emissions is normally contrary to that of combustion efficiency, EICO consistently remained at a low level in this combustor under the currently investigated conditions. EIUHC varied significantly with SR, where the pilot stage contributed more to emissions at low SfR while the main stage played a more important role with the increment of SR. Moreover, a new empirical correlation for NOx emissions in LPP staged CMC combustor was proposed.
Select Trade-Offs in Parallel Hybrid Turboprop Cycle Design
Authors: Sielemann Michael , Kavvalos Mavroudis D. , Selvan Nithish , Claesson Jim , Kyprianidis Konstantinos 
Published: October 2022

Abstract
Parallel hybrid turboprop engines propose a means to reduce fuel consumption of regional aircraft due to lower flight velocities. They feature an electric drive, typically on the free power turbine, and require a design trade-off between the gas turbine and electric power sub-system characteristics. Degrees of freedom include the nozzle expansion, the propeller power loading, the gear ratio, and the selection of shaft speeds. The latter for instance requires a trade-off between propeller and free power turbine efficiency. For a parallel hybrid, the electric machine efficiency becomes a third factor to consider. The objective of this paper is to expose some key aspects of these trade-offs in terms of efficiency and weight. The paper applies sophisticated methodology in both the gas turbine and electrical power domains. For the gas turbine, multi-point design is used. Here, an extension of established synthesis matching schemes is used, which covers the design and operation rules also for the electric components of the hybrid. For the electrical machine, fully analytical sizing is used, which also captures the impact of cooling. For all main gas turbine components and the electric machine, the geometry is estimated based on the sizing methodology, and used as input for the weight estimation. Results are presented for parallel hybrid electric 2.5-spool geared turboprop architectures fulfilling requirements of a notional 19 passenger regional aircraft. Uninstalled fuel consumption can be lower for the hybrid than the conventional baseline, and the key relations to typical cycle parameters such as overall pressure ratio and shaft speed selection are exposed. Overall, the benefit of hybridization is low however with the concept of operations inspired by hybrid turbofans. This is related to differences in contradicting cycle design requirements.
Study on the Influence of Fuel Supply and Distribution on the Performance of Concentric Staged High Temperature Rise Combustor
Authors: Sun Bolun , Song Wenyan , Li Jie 
Published: October 2022

Abstract
Based on the increasing demand for high thrust-to-weight ratio and high temperature rise of military aero-engines, a design scheme of combustor with concentric staged combustion organization is proposed. The main combustion stage of the swirler is a combination of swirling and non-swirling air intake. The verified one-dimensional calculation method is used to calculate and evaluate the performance of the combustion chamber. Based on the verification of three-dimensional numerical method and grid independence, the effects of fuel supply and distribution on combustor performance are studied. The studies show that the combustion efficiency and outlet temperature distribution could be improved when the axial position of the pilot nozzle is located at the outlet of vane channel. However, it will cause the problem that the high temperature flame is too close to the outlet of swirler. With the increase of the main nozzle angle, the combustion efficiency increases, and the overall temperature distribution factor (OTDF) decreases gradually. The fuel distribution ratio of main stage has a great impact on the field of temperature. The increase of fuel distribution ratio is contributed to improve the combustion efficiency and reduce the OTDF, while the total pressure loss coefficient increases slightly within a certain range. However, when the fuel distribution ratio exceeds 80%, the temperature near the baffle plate of dome is overheated, and the improvement effect of combustion efficiency is no longer obvious.
Sensitivity Analysis of Impeller Blade Parameters to Compressor Performance and Aerodynamic Noise
Authors: Yipeng Cao , Zequn Ma , Chen Liu 
Published: October 2022

Abstract
The effects of a series of impeller blade parameters on compressor performance and aerodynamic noise are numerical analyzed in this paper. The inversed impeller blade model of a turbocharger compressor was first constructed by the reverse engineering method. Then, the performance and aerodynamic noise of the inversed impeller blade model was validated using a numerical approach, which combines computational fluid dynamics (CFD) and computational aerodynamic acoustics (CAA). A parameterization of blade starts from the inversed impeller and then morphs it with a number of design parameters, which including tip clearance, the curvature of cut-off trailing edge, exit lean angle, inlet blade angle on shroud and inlet blade angle on hub. The influence of different structural parameters on compressor performance and noise was studied, and the sensitivity analysis of different structural parameters was carried out based on the Morris’s method. The results indicate that the tip clearance, the outlet lean angle of blade and the inlet blade angle at shroud have a significant effect on compressor aerodynamic performance, while the curvature of cut-off trailing edge and the inlet blade angle on hub have less impact. The overall sound pressure level (OASPL) of the aerodynamic noise radiated at compressor inlet shows that the inlet blade angle on shroud and the inlet blade angle on hub have a significant effect on compressor aerodynamic noise. The results of sensitivity analysis further indicate that the tip clearance and the inlet blade angle on shroud are the main parameters that affect compressor aerodynamic performance and noise.
Digital Shadow and Robust Optimization of in Service Squealer Tip Turbine Blades
Authors: Virdis Irene , Ghisu Tiziano , Shahpar Shahrokh , de la Puerta Iñaki , Li Haidong 
Published: October 2022

Abstract
The term uncertainty quantification (UQ) refers to a set of techniques which are used to measure the statistical variability of several input parameters. In recent years, UQ has become increasingly relevant due to its applications in robust design and optimization (RDO). The present work focuses on the RDO of aero engine components. 200 in-serviced high pressure turbine rotors with a squealer tip design were digitized using a GOM 3D scanning technique and analyzed using high-fidelity numerical flow simulations. All the blades considered display some geometrical deviations from the nominal shape and strong erosion along the rim of the squealer tip. A digital shadow with parametrized geometric deviation from nominal is built for each 3D scanned blade. Reynolds-Averaged-Naiver-Stokes simulations are run on each digital shadow with an in-house CFD solver, to quantify the impact of the shape deviation on the performance of the rotor, and to identify the parameters with the largest impact on its adiabatic efficiency. Following this, a robust aerodynamic optimization of the rotor has been performed using gradient based approaches. The resulting geometries and flow-fields are compared in detail, with particular attention to the robustness of the geometries with respect to the parameters defining the uncertainty in blade shape, and to the ones used to characterize the tip erosion.
Asynchronous Communication Pattern for Reducing Simulation Time in Engine Performance Models
Authors: Krouse Charles , Connolly Brian , Gordon Emilio 
Published: October 2022

Abstract
Demand is constantly increasing for high-fidelity models that execute quickly. To increase the fidelity of aircraft engine simulations, low-fidelity thermodynamic models are often interfaced with high-fidelity models used for capturing 2D and 3D effects. Unfortunately, interfaces and high-fidelity models are typically slow compared to rapid lower-fidelity thermodynamic models.
This paper presents an approach for managing the interface between a low-fidelity model and high-fidelity model that, under certain circumstances, significantly reduces simulation time. The typical solver in a thermodynamic engine simulation sequentially iterates through each component in the system until a converged solution is reached. This type of communication pattern is also known as synchronous communication. Alternatively, an asynchronous communication pattern partitions the model into independent groups of components. Each partition contains its own solver, and each partition converges independently of the others. By partitioning a high-fidelity subsystem model, which was developed in an external tool, along with its associated interface, the solver variables associated with the subsystem model can be separated from the main solver. This implementation can reduce the number of calls to the high-fidelity subsystem and reduce overall simulation time.
To demonstrate the asynchronous communication pattern, and to explore the approach’s impact on simulation time, a turbine-based combined cycle (TBCC) engine performance model was developed using the Numerical Propulsion System Simulation (NPSS) software. The NPSS model was interfaced with a high-fidelity afterburner model that was developed in an external tool. Using an asynchronous communication pattern, the engine performance model converged roughly 2.2x faster than using the conventional synchronous communication pattern for the same model. However, it was also shown that the asynchronous communication pattern is not beneficial in all scenarios, because it requires more total solver iterations. In this paper, the authors discuss the implementation and application of the asynchronous communication pattern, results, and conclusions.
Circulation Budget Analysis of the Leading-Edge Vortex in a Wells Turbine Under Steady Inflow Conditions
Authors: Geng Kaihe , Yang Ce , He Xinyu , Hu Chenxing , Zhang Hanzhi , Shi Xin 
Published: October 2022

Abstract
Due to the narrow operating range with the high efficiency of Wells turbines, the performance of Oscillating Water Column (OWC) systems is extremely limited by the stall issue. In this study, a detailed investigation on the flow physics at three typical flow rates corresponding to the design, stall inception, and deep stall conditions is performed, aiming to explore the mechanisms governing the evolution of the leading-edge vortex in terms of the circulation budget analysis. For this purpose, 3D unsteady Reynolds-averaged Navier-Stokes equations with the shear-stress-transport turbulence model are solved for a monoplane Wells turbine with high solidity under the steady-state inflow conditions. The numerical results show encouraging agreement with the available experimental data. The transient flow behaviors of stall inception and deep stall mode are captured by the Proper Orthogonal Decomposition (POD) method. Furthermore, the contributions of the spanwise convection of the vorticity gradient, vorticity tilting term, and the shear layer flux to the circulation of the leading-edge vortex are quantitatively determined within the spanwise control surface. The results indicate that, for stall inception condition, the high turbulent kinetic energy regions are attached to the leading edge of the suction surface with a disturbance of 0.33 times of the rotor frequency. The leading-edge vortex appears after the turbine stall, and its stable development time is less than 1/4 of the rotor period. Although leading-edge vortex occurs periodically after the first shedding with a significant decrease of circulation, it is almost not reattached to the blade surface, which speeds up the shedding and vorticity dissipation. The first shedding of the leading-edge vortex is related to the increase of radial vorticity gradient, but not directly related to the radial velocity. Furthermore, the spatiotemporal distribution of the circulation is similar to the spanwise convection, but there is a phase difference. In addition, the tilting term changes greatly in the evolution of the leading-edge vortex, indicating that the tangential and axial vorticity are tilted, which is verified by the spatial streamlines.