Study of dynamic loads dependence on aircraft engine mount variant after fan blade-out event

A turbofan nonlinear dynamic model is described in the paper. It has been developed for the computation of loads in the engine frame after fan blade-out (FBO) event. The model includes reduced dynamic finite element models of rotors and casings and also nonlinear elements for simulation of “rotor-casing” contact interactions. Thorough attention has been paid to mounts modeling with possible mechanisms taken into account. The engine dynamic behavior during its rotors deceleration to the autorotation mode after the FBO event has been simulated for the following two forward mount arrangement variants: fastening to the inner part of the intermediate casing; fastening to the outer part of the intermediate casing. The effect of load reduction device (LRD) – special elements which are introduced to fan supports, destroyed under certain force and don’t transfer improper loads to the engine casing system after the FBO event, has been studied. The analysis of maximum loads on engine mounts has been performed for the two listed design variants for both cases: with and without an LRD in fan supports

Modeling and control of the starter motor and start-up phase for gas turbines

Improving the performance of industrial gas turbines has always been at the focus of attention of researchers and manufacturers. Nowadays, the operating environment of gas turbines has been transformed significantly respect to the very fast growth of renewable electricity generation where gas turbines should provide a safe, reliable, fast, and flexible transient operation to support their renewable partners. So, having a reliable tools to predict the transient behavior of the gas turbine is becoming more and more important. Regarding the response time and flexibility, improving the turbine performance during the start-up phase is an important issue that should be taken into account by the turbine manufacturers. To analyze the turbine performance during the start-up phase and to implement novel ideas so as to improve its performance, modeling, and simulation of an industrial gas turbine during cold start-up phase is investigated this article using an integrated modular approach. During this phase, a complex mechatronic system comprised of an asynchronous AC motor (electric starter), static frequency converter drive, and gas turbine exists. The start-up phase happens in this manner: first, the clutch transfers the torque generated by the electric starter to the gas turbine so that the turbine reaches a specific speed (cranking stage). Next, the turbine spends some time at this speed (purging stage), after which the turbine speed decreases, sparking stage begins, and the turbine enters the warm start-up phase. It is, however, possible that the start-up process fails at an intermediate stage. Such unsuccessful start-ups can be caused by turbine vibrations, the increase in the gradients of exhaust gases, or issues with fuel spray nozzles. If, for any reason, the turbine cannot reach the self-sustained speed and the speed falls below a certain threshold, the clutch engages once again with the turbine shaft and the start-up process is repeated. Consequently, when modeling the start-up phase, we face discontinuities in performance and a system with variable structure owing to the existence of clutch. Modeling the start-up phase, which happens to exist in many different fields including electric and mechanical application, brings about problems in numerical solutions (such as algebraic loop). Accordingly, this study attempts to benefit from the bond graph approach (as a powerful physical modeling approach) to model such a mechatronic system. The results confirm the effectiveness of the proposed approach in detailed performance prediction of the gas turbine in start-up phase

Numerical study on the coupled vibration characteristics of dual-rotors system with little rotation speed difference

In view of statically indeterminate structures of the decanter centrifuge, an iteration calculation model of nonlinear bearing stiffness is built innovatively. Based on gear meshing stiffness, material and lubricant film damping, coupled dual-rotors vibration model of screw-differential mechanism-bowl is constructed using solid elements. Applying ANSYS modal analysis, critical speeds along with vibration modes of dual-rotors and single-rotor are simulated, and the impacts of the differential mechanism and single-rotor modal on dual-rotors modal are obtained. Built on the harmonic response analysis, the results indicate that the system responses differently for the different rotors by manipulating the dynamic responses of the centrifuge under single rotor unbalance excitation. On the basis of transient structural analysis, beat vibration characteristics of dual-rotors system with little rotation speed difference are obtained, and a conclusion of the system responses separately for the unbalance mass of different rotors at a low rotating speed is acquired. The models and methods adopted in simulation are proved to be reasonable and feasible by experiment. The results have certain significance for the design and the dynamic balancing technique of the decanter centrifuge

A Review of Heat Transfer in Turbochargers

The conventional powertrain has seen a continuous wave of energy optimization, focusing heavily on boosting and engine downsizing. This trend is pushing OEMs to consider turbocharging as a premium solution for exhaust energy recovery. Turbocharger is an established, economically viable solution which recovers waste energy from the exhaust gasses, and in the process providing higher pressure and mass of air to the engine. However, a turbocharger has to be carefully matched to the engine. The process of matching a turbocharger to an engine is implemented in the early stages of design, through air system simulations. In these simulations, a turbocharger component is represented largely by performance maps and it serves as a boundary condition to the engine. The thermodynamic parameters of a turbocharger are calculated through the performance maps which are usually generated experimentally in gas test stands and used as look-up table in the engine models. Thus, the operational of the engine is dictated by the air flow thermodynamic parameters (pressure, temperature and mass flow) from the turbocharger compressor; this in turn will determine the thermodynamic parameters for the exhaust gas entering the turbocharger turbine. The importance and its sensitivity dictate that any heat transfer affecting the experiments to acquire the performance maps will cause errors in the characterization of a turbocharger. This will consequently lead to inaccurate predictions from the engine model if the heat transfer effects are not properly accounted for. The current paper provides a comprehensive review on how the industry and academics are addressing the heat transfer issue through advancing researches. The review begins by defining the main issues related with heat transfer in turbochargers and the state-of-the-art research looking into it. The paper also provides some inputs and recommendations on the research areas which should be further investigated in the years to come

가스터빈 림 씰 성능에 휠스페이스 스월이 미치는 영향 측정

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2019. 2. 송성진.가스터빈 엔진은 가장 효율적인 동력원으로서 제트 추진 및 발전을 위해 널리 사용되어왔다. 첨단 재료공학과 이차 유로 시스템, 대류 냉각, 막 냉각 등의 진보한 가스터빈 냉각 기술의 도입은 고효율, 고출력 가스터빈 엔진의 지속적인 발전의 주춧돌이 되었다. 현대의 가스터빈 엔진에서 터빈은 20-30%의 압축기 공기를 냉각, 씰링 및 누설 유동으로 소비한다. 높은 터빈 입구 온도가 다른 모든 손실을 보상한다 하더라도, 이러한 유량 손실은 전효율에 심각한 불이익을 초래한다. 따라서, 씰링 유량을 줄일 수 있는 획기적인 설계가 높은 전효율을 달성하기 위한 하나의 중요한 요인이 되었다. 스테이터와 로터 디스크 사이에 형성되는 휠스페이스로의 주유로 고온 가스 유입 문제는 이차 유로 시스템이 당면한 중요하고 본질적인 문제이다. 주유로와 휠스페이스 압력 차이에 기인하는 이 현상은, 터빈 구성품에 열 피로와 크립 같은 심각한 구조적 안정성 문제를 야기한다. 때문에, 반경 및 축 방향으로 겹쳐지는 형상의 림 씰이 스테이터와 로터 구성품의 주변에 장착되며 충분한 씰링 유량이 유입을 줄이거나 막기 위해 휠스페이스로 공급된다. 림 씰링을 위한 유량을 최소화하기 위한 효과적인 방법에 대한 다양한 연구가 수행되었으나, 유지보수와 구성품 무게와 같은 실용성 측면의 문제가 성능 향상의 발목을 잡았다. 본 논문은 림 씰링 성능을 향상시키기 위한 획기적인 방법론에 대한 실험적 연구를 다룬다. 단일 반경 간극 림 씰과 함께 특수하게 설계된 휠스페이스 선회기가 씰링 성능 향상을 평가하기 위해 사용되었으며, 휠스페이스 내 유동의 선회 성분을 증가시킴으로써 18.49%의 씰링 성능 향상을 달성하였다. 휠스페이스 내에서 씰링 효과와 선회비, 반경 방향 속도 분포를 포함한 다양한 측정이 이루어졌다. 비록 림 씰을 통한 유입은 비정상, 3차원 유동장에 기인하지만, 실험 데이터는 휠스페이스 내 유동의 유체역학적 통찰력을 제공한다. 이러한 실험적 측정은 향후 엔진 설계의 데이터베이스를 확장하는데 기여할 것으로 기대된다. 공력 성능시험과 이차 유로 시스템 연구를 위해 1단 축류 터빈 시험 장비가 새로이 설계되었다. 시험 장비의 형상과 유동 조건은 실제 엔진을 무차원 상사함으로써 엔진의 주유로 및 휠스페이스 유동을 모사할 수 있도록 설계되었다. 설계 항목은 동력원 구성, 시험부 설계, 재질 선정, 구조 해석, 공차 관리 및 밸런싱, 계측 장비 구성을 포함한다. 운전 조건은 타기관 시험 설비의 사양과 일치하는 경향을 보여주었으며, 설계된 시험 장비는 고압터빈단에 널리 이용되는 이중 반경 간극 림 씰로 검증되었다. 포괄적인 계측장비 구성은 주유로와 휠스페이스 내에서 다양한 측정을 가능케한다. 또한, 시험 장비에 적용된 설계 특성들을 통해 다양한 시험 환경을 조성할 수 있다.As the most adaptable source of power, the gas turbine engines have been widely used for jet propulsion, marine and industrial application. Introduction of advanced gas turbine cooling technologiessecondary air system, internal convective cooling, external surface film cooling with cutting edge metallurgy, formed one of the major pillars supporting the continuous development of high efficiency, high power output gas turbine engines. In modern gas turbine engines, the turbine alone may use 20 to 30% of the compressor air for cooling, sealing and leakage flows, which presents a severe penalty on the overall efficiency even the turbine inlet temperature is sufficiently high for the gains to outweigh the losses. Therefore, the novel design to minimize the sealing flow demand will be a key factor to achieve the better overall efficiency of the engines. The hot mainstream gas ingress into the wheel-space, formed between the stator and rotor disks, is one of the most important and intrinsic problems of the secondary air system faced. Principally governed by the pressure difference between mainstream annulus and wheel-space, the turbine components experience serious structural integrity problems such as thermal fatigue and unwanted creep. The rim seals, with the combinations of radial and axial overlapping geometries, are installed at the endwall platform between stator and rotor components. Inevitably, sufficient sealing flow is introduced into wheel-space to reduce or isolate the ingress. The efficient methods to minimize the sealing flow demand for rim sealing purpose have been studied, however, following practical problems in the aspect of maintenance and weight of components caught up with further improvement. This thesis presents an experimental investigation of novel methodology to improve rim sealing performance. By adding swirl flow component inside the wheel-space, 18.49% reduction in sealing flow demand was achieved. The single radial-clearance rim seal with specially designed blades, called ``wheel-space swirler'', are used to evaluate the sealing performance improvement. The extensive range of measurements including sealing effectiveness, swirl ratio and radial velocity distribution inside the wheel-space had been conducted. Although the ingress through the rim seal is a consequence of an unsteady, three-dimensional flow field, the experimental data gave insights into the fluid dynamics for wheel-space flow. These experimental measurements are expected to provide the wider database that can be used for future engine design. The design of single-stage axial turbine research facility, available on both aerodynamic performance and secondary air system studies, is described. It was designed to fulfil engine representative flows both in mainstream and wheel-space, by downscaling the full size engine. The on-design operating conditions are shown to be in the trend of other gas turbine research facilities. The research facility was validated with the double radial-clearance rim seal which has been widely used in high pressure turbine stage. Comprehensive instrumentations allow the detailed measurements both in the mainstream and wheel-space. The design features applied on the research facility enable versatile test configurations.Abstract Contents List of Tables List of Figures Nomenclature Chapter 1 Introduction 1.1 Gas Turbine Engines 1.2 Secondary Air System 1.3 Hot Gas Ingestion 1.4 Thesis Aims 1.5 Thesis Outline Chapter 2 Literature Review 2.1 Wheel-space Flow Structure 2.2 Hot Gas Ingestion 2.2.1 Experiments on Various Rim Seal Congurations 2.2.2 Analytical Models 2.3 Mainstream and Sealing Flow Interactions Chapter 3 Design of a Single-stage Axial Turbine Research Facility 3.1 Overview 3.2 Flow Path Configurations 3.3 Powertrain and Carriage System 3.4 Test Section Configuration 3.4.1 Stage Design 3.4.2 Wheel-space Geometries 3.5 Material Selections 3.6 Structural Analysis 3.7 Machining and Assembly Features 3.7.1 Tolerance and Surface Roughness Control 3.7.2 Balancing and Bearing Selection 3.8 Instrumentations 3.8.1 Mainstream Annulus and Secondary Flow Line 3.8.2 Wheel-space 3.8.3 Data Acquisition System 3.9 Sensor Calibrations and Uncertainty Analysis Chapter 4 Experimental Measurements on Double Rim Seal For Facility Validation 4.1 Test Configurations for Double Rim Seal 4.2 Sealing Effectiveness 4.3 Pressure and Velocity Measurements 4.3.1 Mainstream Pressure Asymmetries 4.3.2 Swirl Ratio Chapter 5 Study of Wheel-space Swirl Effects on Single Rim Seal Performance 5.1 Test Configurations for Single Rim Seal 5.2 Wheel-space Swirler Design 5.3 Sealing Effectiveness 5.4 Pressure and Velocity Measurements 5.4.1 Mainstream Pressure Asymmetries 5.4.2 Swirl Ratio and Wheel-space Pressure 5.4.3 Wheel-space Radial Velocity Chapter 6 Conclusion 6.1 Design of the Experimental Facility 6.2 Facility Validation 6.3 Wheel-space Swirl Effects on Sealing Performance 6.4 Proposal for Modified Orifice Model 6.5 Practical Implications 6.6 Scaling to Engine Conditions 6.7 Future Works Bibliography Appendix A Owen's Orifice Model 국문초록Maste

Development of an Ultra-High Efficiency Gas Turbine Engine (UHEGT) with Stator Internal Combustion: Design, Off-Design, and Nonlinear Dynamic Operation

An Ultra-High Efficiency Gas Turbine (UHEGT) technology is developed in this study. In UHEGT, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed in multiple stages and integrated within the High-Pressure (HP)-turbine stator rows. Fundamental issues of aero-thermodynamic design, combustion, and heat transfer are addressed in this study. The aero-thermodynamic study shows that the UHEGT-concept improves the thermal efficiency of gas turbines by 5-7% above the current most advanced gas turbine engines, such as Alstom GT24. The designed thermodynamic cycle has a 45% thermal efficiency and includes a six-stage turbine with three stages of stator internal combustion. Meanline approach is used to preliminary design the entire flow path in the turbine. Multiple configurations are designed and simulated via Computational Fluid Dynamics (CFD) to achieve the optimum combustion system for UHEGT. Flow patterns, temperature distributions, secondary losses, etc. are among the parameters studied in the results. The final configuration for the combustion system includes two rows of injectors placed before the stator rows in the first three turbine stages. The current injector configuration provides a highly uniform temperature distribution at the rotor inlet, low pressure loss, and low emissions compared to the other cases. Different approaches are numerically studied to lower the stator blade surface temperature distribution in UHEGT from which indexing (clocking) is shown to be very effective. In the final part of this study, a dynamic simulation is performed on the entire engine using the nonlinear generic code GETRAN developed by Schobeiri. The simulations are in 2D (space-time) and include the complete gas turbine engine. The system performance is studied under variable design and off-design conditions. The results show that most of the system parameters fluctuate with similar patterns to the fuel schedule. However, the amplitudes of the fluctuations are different and there is a time lag in the response profiles relative to the fuel schedules. It is shown that thermal efficiency variations are smaller compared to the other parameters which means the system performs in efficiencies close to the design point throughout the entire cycle

Contribution to the Experimental Characterization and 1-D Modelling of Turbochargers for IC Engines

At the end of the 19th Century, the invention of the Internal Combustion Engine (ICE) marked the beginning of our current lifestyle. Soon after the first ICE patent, the importance of increasing air pressure upstream the engine cylinders was revealed. At the beginning of the 20th Century turbo-machinery developments (which had started time before), met the ICE what represented the beginning of turbocharged engines. Since that time, the working principle has not fundamentally changed. Nevertheless, stringent emissions standards and oil depletion have motivated engine developments; among them, turbocharging coupled with downsized engines has emerged as the most feasible way to increase specific power while reducing fuel consumption. Turbocharging has been traditionally a complex problem due to the high rotational speeds, high temperature differences between working fluids (exhaust gases, compressed air, lubricating oil and cooling liquid) and pulsating flow conditions. To improve current computational models, a new procedure for turbochargers characterization and modelling has been presented in this Thesis. That model divides turbocharger modelling complex problem into several sub-models for each of the nonrecurring phenomenon; i.e. heat transfer phenomena, friction losses and acoustic non-linear models for compressor and turbine. A series of ad-hoc experiments have been designed to aid identifying and isolating each phenomenon from the others. Each chapter of this Thesis has been dedicated to analyse that complex problem proposing different sub-models. First of all, an exhaustive literature review of the existing turbocharger models has been performed. Then a turbocharger 1-D internal Heat Transfer Model (HTM) has been developed. Later geometrical models for compressor and turbine have been proposed to account for acoustic effects. A physically based methodology to extrapolate turbine performance maps has been developed too. That model improves turbocharged engine prediction since turbine instantaneous behaviour moves far from the narrow operative range provided in manufacturer maps. Once each separated model has been developed and validated, a series of tests considering all phenomena combined have been performed. Those tests have been designed to check model accuracy under likely operative conditions. The main contributions of this Thesis are the development of a 1-D heat transfer model to account for internal heat fluxes of automotive turbochargers; the development of a physically-based turbine extrapolation methodology; the several tests campaigns that have been necessary to study each phenomenon isolated from others and the integration of experiments and models in a comprehensive characterization procedure designed to provide 1-D predictive turbocharger models for ICE calculation.Reyes Belmonte, MÁ. (2013). Contribution to the Experimental Characterization and 1-D Modelling of Turbochargers for IC Engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34777TESI

Total pressure loss mechanism in a diesel engine turbocharger

Simulation tools are intensively used in the design stage of diesel engines due to their contributions to significant savings in cost and time for the engine development. Since most of DI diesel engines are turbocharged, it is of vital importance to hold a good understanding of turbine and compressor characteristic to predict the engine performance accurately. However, this data is often not available from turbocharger manufacturers, particularly for turbines. On available turbine maps the operating range of the turbine is constrained due to limitations of conventional turbocharger test benches. Operations with a wider range of turbocharger pressure ratios can be achieved by employing complex turbocharger test benches, which will also lead to higher costs including hardware and labour. An alternative solution is to develop numerical models for the turbocharger based on thermodynamics. In this thesis numerical models has been developed for predicting the performance of both the centrifugal compressors and turbines and they have been also validated using test cases, particularly for variable geometry turbines. Following detailed parametric studies, the turbocharger model has been validated against experimental data of a turbocharger with a variable geometry turbine. Results showed that the model was capable of predicting the characteristics maps of the turbocharger accurately, requiring a minimal amount of turbocharger geometric properties, experimental data and calibration parameters. Thus, by combing with the engine performance simulation software there is a highly potential for the numerical model developed in this work to become a useful tool for predicting engine performance and turbo matching calculations or diagnostic applications