bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two Degree-of-Freedom µ Synthesis Control With Kalman Filter for Flight Environment Simulation Volume With Sensors Uncertainty
Authors: Zhu Meiyin , Wang Xi , Yang Shubo , Chen Huairong , Miao Keqiang , Gu Nannan 
Published: November 2019

Abstract
Flight Environment Simulation Volume (FESV) is the most important subsystem of Altitude Ground Test Facilities (AGTF). Its control precision of temperature and pressure determines the level of test ability of AGTF. However, in practice, the sensor hysteresis and noise may greatly affect the control precision of FESV. To improve the control performance of FESV in practice, a new control structure of two degree-of-freedom (DOF) μ synthesis control with the extended Kalman filter (EKF) considering actuators and sensors uncertainty is proposed, which constitutes a core support part of the paper. For the problem of sensors de-noising, an EKF is devised to provide a credible feedback signal to the two DOF μ controller. Aiming at the problem of reference command’s rapid change, one freedom feed forward is adopted, while another freedom output feedback is used to ensure good servo tracking as well as disturbance and noise rejection; furthermore to overcome the overshoot problem and acquire dynamic tuning, an integral is introduced in inner loop; additionally, two performance weighting functions are designed to achieve robustness and control energy limit considering the uncertainties in system.
In order to verify the effectiveness of the designed two DOF μ synthesis controller with EKF, we suppose a typical engine test condition with Zoom-Climb and Mach Dash and consider time delay and Gaussian noise in the sensors. The simulation results show that the designed two DOF μ synthesis controller with EKF has good servo tracking and noise rejection performance and the relative steady-state and transient errors of temperature and pressure are both less than 0.1% and 0.2% respectively. Additionally, we validate the robust performance of the designed two DOF μ controller with EKF by using the upper bound value of the uncertainty parameters. Furthermore, to verify the advantage of the designed two DOF μ controller with EKF, we compare its control results with those of without EKF and μ controller without considering sensor time delay. The comparison results show that the designed two DOF μ controller with EKF provides better performance. Finally, to verify the advantage of μ synthesis controller, we designed a PID controller and compare the simulation result with μ controller, the comparison result show that the designed μ controller is better than PID controller.
The Effect of Inlet Swirl on Brush Seal Bristle Deflections and Stability
Authors: Liu Yuxin , Chew John W. , Pekris Michael J. , Kong Xiaozhi 
Published: November 2019

Abstract
This paper considers 3D CFD and structural modelling of brush seals, and investigates the effects of inlet swirl on the bristle pack. The model couples aerodynamic forces generated by CFD to a structural model that includes interaction between bristles. At a critical value of inlet swirl, aerodynamic forces cause circumferential slip of the upstream bristle row. In practice this may lead to instability of the bristle pack and is consistent with anecdotal reports of seal behavior. The critical swirl velocity was reduced when the downstream pressure level was raised, keeping the same upstream total to downstream static pressure difference. This is caused by the increased dynamic head associated with the inlet swirl. Inclusion of a front plate in the seal design does not offer the intended protection to the bristle pack in highly swirling environments. This is associated with highly swirling flow impinging on the bristle tips. Fitting of roughness elements on the upstream face of the front plate could improve stability by reducing swirl of the flow impacting on the bristles. Increasing the bristle diameter and bristle stiffness does not necessarily prevent slip at higher inlet swirl velocities, but reduces the magnitude of slip of the upstream bristles.
Impact of Engine Degradation on Optimum Aircraft Trajectories: Short Range
Authors: Navaratne R. , Sethi V. , Lawson C. 
Published: November 2019

Abstract
This work aims to provide a methodology to enhance the conventional approach of the aircraft trajectory optimisation problem by including engine degradation and real aircraft flight paths within the optimisation framework; thereby the impact of engine degradation on optimum aircraft trajectories were assessed by quantifying the difference in fuel burn and emissions, when flying a trajectory which has been specifically optimised for an aircraft with degraded engines and flying a trajectory which has been optimised for clean engines. For the purpose of this study models of a clean and two degraded engines have been developed based on Exhaust Gas Temperature (EGT) margin deterioration. Aircraft performance model have been developed for short range aircraft with the capability of simulating vertical and horizontal flight profiles provides by the airlines. An emission prediction model was developed to assess NOx emissions of the mission. In addition, a multidisciplinary aircraft trajectory optimisation framework was developed to analyse short range flight trajectories under three cases. Case_1: Aircraft with clean engines, Case_2 and Case_3 were Aircraft with two levels of degraded engines. Two different multi objective optimisation studies were performed; (1) Fuel burn vs Flight time, and (2) Fuel burn vs NOx emission, Finally optimised trajectories generated with degraded engines were compared with the optimised trajectories generated with clean engines. The results have shown impact of engine degradation on optimum aircraft trajectories are significant and in order to reduce fuel burn and emissions aircraft need to fly on an optimised trajectory customised for the degraded engine performance.
Thermal End-Wall Contouring
Authors: Mimic Dajan , Oettinger Marcel , Jätz Christoph , Herbst Florian , Seume Joerg R. 
Published: November 2019

Abstract
In this paper, we propose the concept of thermal end-wall contouring (TEWC) as a novel approach to reducing secondary-flow and boundary-layer losses in turbomachines and ducts by means of thermally manipulating the boundary layer. We introduce, for the first time, the general concept of TEWC and provide a proof of concept using the example of a bent duct. The results demonstrate that a considerable impact on the flow field is achieved not only by mean heat flux across the end-wall of the duct, but also by the spatial distribution of the heat fluxes.
Influence of Fuel Injection Location in a Small Radial Swirler Low NOx Combustor for Micro Gas Turbine Applications
Authors: Andrews Gordon E. , Kim Su 
Published: November 2019

Abstract
The influence of fuel injection location in a low NOx (1) micro-gas turbine [MGT] in the ∼50kWe (kW electric) size range was investigated, for NG and propane, to extend the power turn down using a pilot fuel injector. The low NOx main combustor (1) was a radial swirler with vane passage fuel injection and had ultra-low NOx emissions of 3ppm at 15% O2 at 1800K with natural gas, NG at a combustion intensity of 11.2 MW/m2bara (MW thermal). This was a 40mm diameter outlet eight bladed radial swirler in a 76mm diameter combustor, investigated at 740K air temperature at atmospheric pressure. However, power turn down was poor and the present work was undertaken to determine the optimum position of pilot fuel injection that would enable leaner mixtures to be burned at low powers. Central injection of pilot fuel was investigated using 8 radial outward holes. This was compared with pilot fuel injected at the 76mm wall just downstream of the 40mm swirler outlet. It was show that the central injection pilot was poor with a worse weak extinction than for radial passage fuel injection. The 76mm outlet wall injection was much more successful as a pilot fuel location and had a weak extinction of 0.18Ø compared with 0.34Ø for vane passage fuel injection. NOx emissions were higher for wall fuel injection, but were still relatively low at 16ppm at 15% oxygen for natural gas. This indicates that wall fuel injection could be combined with vane passage fuel injection to improve the micro-gas turbine low NOx performance across the power range.
Validation of Chemistry Acceleration Techniques With an Industrial Gas Turbine
Authors: Mallouppas George , Goldin Graham , Zhang Yongzhe , Thakre Piyush , Rogerson Jim 
Published: November 2019

Abstract
Two different numerical techniques for chemistry acceleration are examined with Large Eddy Simulation of a commercial swirl industrial gas turbine combustor operating at 3 bar. This work presents the results for SGT-100 Dry Low Emission (DLE) gas turbine provided by Siemens Industrial Turbomachinery Ltd. The related experimental study was performed at the German Aerospace Centre, DLR, Stuttgart, Germany.
LES with detailed chemistry calculations is an attractive tool to study turbulent premixed flames in industrial gas turbine combustors, because it can help understand turbulence-chemistry interactions, detailed flame characteristics and pollutant formation. Detailed chemistry can capture kinetically dominated processes such as ignition, extinction and pollutant formation. However, computational resources required for such calculations are often prohibitive due to the computational costs of transporting and integration of a large number of species with a wide range of chemical time-scales. Chemistry acceleration techniques can substantially reduce run-time with ideally a small loss in accuracy. Therefore, the purpose of this work is to quantify the relative increase in performance and potential loss in accuracy with two chemistry acceleration techniques namely Clustering, Dynamic Mechanism Reduction (DMR) and their combination.
The results show that the different chemistry acceleration techniques do not compromise the time averaged flow statistics. However, there are some differences in NO and CO emissions. Chemistry acceleration techniques yield up to ∼3 times speed-up of the simulation.
Methane-Hydrogen Blends in Micro Gas Turbines: Comparison of Different Combustor Concepts
Authors: Tuccillo Raffaele , Cameretti Maria Cristina , De Robbio Roberta , Reale Fabrizio , Chiariello Fabio 
Published: November 2019

Abstract
The paper deals with the analysis of the response of two different types of combustors equipping micro gas turbines, when supplied with methane–hydrogen mixtures. Besides the expected reduction in carbon dioxide production, several problems have to be considered concerning the possible increase in nitric oxide formation and flashback phenomena as well.
The two combustors approach the lean-premixed or RQL concept and the study is carried out with a number of CFD simulations based on detailed kinetic schemes and accurate turbulence models. Some preliminary experimental validations support the numerical modelling of the lean-premixed combustor, so encouraging the authors to proceed with the analysis of increasing hydrogen / methane ratios. The RQL type combustor offers, in addition, the possibility of an effective split of the injection into two different streams, with evident benefits in terms of nitric oxides reduction.
A Novel Stall Warning Indicator: Part I — Applications and Limitations
Authors: Rückert Roland , Eck Mario , Peitsch Dieter , Lehmann Marc 
Published: November 2019

Abstract
The present work is the first of two papers investigating the operation principle of stall warning quantities. It discusses the use and implementation of novel stall warning techniques based on experimental tests. Each of the addressed techniques is based upon integral statistical analysis of time-resolved wall pressures in close proximity to the leading edge of a compressor rotor. The experiments were conducted on a low speed axial compressor test rig at the Chair of Aeroengines at the Technische Universität Berlin. The compressor suffers from a specific type of pre-stall instability. The signature within the frequency spectrum of this semi-stable operating point is in itself unique and was observed by many within the scientific community on numerous occasions and various axial compressor types, both low and high speed. Strong evidence has been elaborated which indicate that each of those so called stall warning indicator’s functionality is based upon the existence of this prestall phenomena. The first of two indicators is time-dependent as it evaluates the as-is state against surrounding operating points during transient manoeuvres. Furthermore, the impact of varying geometrical boundary conditions, which are known to regularly arise in flight operations, were taken into account. The functionality of the indicator is assured if the instrumentation is adjusted accordingly. The second indicator is mainly a location-dependent quantity as it evaluates the pressure signature along the axial direction within the rotor passage at various aerodynamic loadings. The latter also gave rise to some fundamental and preliminary understanding of the physics behind so called prestall disturbances.
Multi-Wave Vibration Caused by Flutter Instability and Nonlinear Tip Shroud Friction
Authors: Gross Johann , Krack Malte 
Published: November 2019

Abstract
Measurements revealed the contribution of multiple traveling waves to the flutter vibrations of bladed disks. Saturated flutter vibration, whether in this multi-wave or in its better-understood single-wave form, is a nonlinear phenomenon. However, it is still not understood of what physical origin the relevant nonlinearities are, and under what conditions single-wave or multi-wave flutter vibration occurs. Recent theoretical work suggests that multi-wave flutter vibration can be explained by strongly nonlinear frictional inter-blade coupling. The verity of this hypothesis is strictly limited by the simplicity of the considered model, namely a cyclic chain of seven oscillators with frictional coupling and rather unrealistic aeroelastic behavior.
In the present work, it is demonstrated that nonlinear dynamical contact interactions at tip shrouds are a likely cause for the observed multi-wave flutter vibration. To this end, a more realistic structural turbine blade row model with a more realistic aeroelastic behavior is considered. Some insight into its intriguing dynamics, dependence of limit states on initial conditions and eigenvalue placement is provided. For instance, it is shown that there is an intimate relation between internal combination resonance conditions of certain traveling wave modes and the spectral content of single- and multi-wave flutter oscillations.
Dynamic Analysis and Optimization on Assembly Parameters of Rod Fastening Rotor System With Manufacturing Tolerances
Authors: Zhao Bingxi , Yuan Qi , Li Pu 
Published: November 2019

Abstract
Rod fastening rotor (RFR), as a typical rotor structure of gas turbine which is different from the integral rotor, is comprised of a set of discs clamped together by a central tie rod or several tie rods on the pitch circle diameters. In process of machining, tolerances of the disc are inevitable, of which the parallelism error and mass imbalance are focused on in this paper. Firstly, the complex bending of RFR by accumulation of parallelism errors of discs is derived through the coordinate transmission. Then the static analysis of RFR is performed to obtain the additional pressure by the effect of unbalanced forces, which is related to the assembly angles and rotating speed, on contact surfaces using a linear hypothesis, based on which the distribution of contact pressure considering the original pre-tightening force is obtained. Then the Bifractal-Regular theory is adopted to acquire the micro-topography of the contact interface and derive the contact stiffness related to normal contact pressure, fractal upper length limit and regular shape of the contact interfaces. After that, the zero thickness element is introduced to obtain the equivalent stiffness matrices of the contact surface. In addition, the circumferential uniformly distributed rods are modeled as a spring element which provides additional bending stiffness for the RFR. Based on the analysis above, the dynamic model of the RFR-bearing system containing 10 discs is established using the Timoshenko beam element where the continuous part of the shaft is modeled by Timoshenko beam element considering shear effect. Finally, the multi-optimization is carried out on the vibration response by the coupled effects of both initial bending and mass imbalance of the RFR-bearing system through which the optimal assembly angles are obtained. The results show a good performance in decreasing vibration as well as bending of the RFR system.
Computational Fluid Dynamics Simulation of Syngas Nozzle of Gas Turbine for Syngas
Authors: Zhang Bo , Qin Ye , Shi Shaoping , Yan Shu , Mu Yanfei , Liu Xin , Chen Xinming , Guo Yutong , Zeng Chongji 
Published: November 2019

Abstract
Integrated Gasification Combined Cycle (IGCC) is a technology that integrates the coal gasification and combined cycle to produce electricity efficiently. Due to the fact that the heating value of syngas from coal gasification process is typically lower than that of the natural gas, the conventional gas turbine will have to be adapted for syngas. The nozzle adjustment is the key to the successful transformation since the ignition properties are different between syngas and natural gas which have totally different compositions. The nozzles suitable for natural gas have been prone to partially melting around the flame stabilization holes on sidewalls of the nozzle in real operation. Thus a computational fluid dynamics (CFD) model was constructed for the syngas nozzles as well as combustion chamber of the gas turbine for low heating value syngas to study the thermostability of the nozzle. The detailed structure of the syngas nozzle, the combustion characteristics of syngas, as well as the actual operation condition of the gas turbine were all employed in the CFD model to improve the simulation accuracy. The reason of partially melting of the nozzles suitable for natural gas can be attributed to that the syngas leaked from the flame stabilization holes into the mainstream air can quickly mix with air, adhere to the sidewalls of the nozzles and then ignite around the holes which result in temperatures high enough to melt the material of the nozzle around the holes through CFD simulation. Finally, a new structure of the syngas nozzle was proposed and validated by CFD simulations. The simulation result shows that the flames caused by the syngas leaked from the flame stabilization holes are no longer adhering to the nozzle sidewalls and local high temperature can be lowered by about 30% which will not be able to melt the nozzle material.
A Method to Evaluate the Sensitivity of Aerodynamic Damping to Mode Shape Perturbations
Authors: Li Jing , Chakrabarti Suryarghya , Ren Wei-Min 
Published: November 2019

Abstract
Turbomachinery blade mode shapes are routinely predicted by finite element method (FEM) programs and are then used in unsteady computational fluid dynamic (CFD) analyses to predict the aerodynamic damping. This flutter stability assessment process is critical for the last-stage blades (LSBs) of modern heavy-duty gas turbines (HDGTs) which can be particularly susceptible to flutter. Evidences suggest that actual mode shapes may deviate from the FEM predictions due to changes in the FEM boundary or loading conditions, effects of the nonlinear friction contacts, and blade-to-blade variations (mistuning), among others. This uncertainty in the mode shape is accompanied by a general lack of knowledge on the sensitivity of the aerodynamic damping to a small change in mode shape. This paper presents a method to perturb a mode shape and estimate the corresponding change in aerodynamic damping in a framework enabled by linear theories and a rigid-body, quasi-3D treatment of mode shapes. This method is of low computational cost and is suitable for use in the preliminary design cycle. The numerical validation and applications of the method are demonstrated on two LSB blades. Results suggest that the mode shape sensitivity can be substantial and may even exceed the change in aerodynamic damping of a frictionally damped system when subjected to various levels of excitation.
Validation of a New Turbulent Flame Speed Facility for the Study of Gas Turbine Fuel Blends at Elevated Pressure
Authors: Morones Anibal , Turner Mattias A. , León Victor , Ruehle Kyle , Petersen Eric L. 
Published: November 2019

Abstract
Turbulent combustion is a very active and challenging research topic of direct interest to the design and operation of gas turbine engines. A spherically expanding flame immersed in a turbulent field is one way to gain fundamental insight on the effect of turbulence on combustion. This kind of experiment is often conducted inside a fan-stirred flame bomb, preferably at conditions of high pressure, high temperature, and intense turbulence. A new fan-stirred flame bomb was designed and built to provide a device for conducting fundamental turbulent flame measurements at conditions of interest to gas turbine engines. A literature review on existing systems was used as guidance in the design of the turbulence-generation elements in the present rig. A few options of impellers were explored. The flow field produced by the chosen impeller was measured with Laser Doppler Velocimetry (LDV). A detailed exposition of the vessel engineering and construction are presented, including current activities that will extend the use of the facility for heated experiments up to at least 400 K. Before turbulent experiments were attempted, a validation of the rig accuracy and pressure worthiness was made. Finally, a demonstration of the new apparatus was made by testing a lean mixture of syngas. The experiment matrix using hydrogen and H2/CO mixtures included three levels of pressure (1, 5, and, 10 bar) and three levels of turbulence fluctuation rms (1.4, 2.8, and 5.5 m/s). Data based on the high-speed schlieren diagnostic are presented.