Showing papers on "Turbofan published in 2019"

Mission Analysis and Emissions for Conventional and Hybrid-Electric Commercial Transport Aircraft

Abstract: A feasibility study of a hybrid-electric commercial transport aircraft was conducted by analyzing the simulated performance and lifecycle carbon dioxide (CO2) emissions of a conventional single-ais...

Conceptual Assessment of Hybrid Electric Aircraft with Distributed Propulsion and Boosted Turbofans

Abstract: This paper presents the results of a study into the effect of distributed hybrid-electric propulsion on aircraft performance and characteristics. To size these aircraft, a new preliminary sizing method for hybrid-electric aircraft with distributed propulsion, including aero-propulsive interaction, is combined with a modified Class-II weight estimation method where energy consumption is estimated through a mission analysis method. Comparison of the predictions from these new methods to the predictions from a traditional sizing method has shown to be within 5% agreement for a single-aisle aircraft powered by conventional turbofans in terms of wing loading, energy consumption and maximum take-off weight. A boosted turbofan aircraft as well as two aircraft with different distributed, hybrid-electric propulsion systems have been assessed for a 150-pax aircraft designed for a harmonic range of 800nmi. Each of these aircraft designs showed significant increases in propulsion system mass (up to 700%). The distributedpropulsion aircraft showed increases in energy consumption of 34% and 51%, respectively, over the conventional turbofan aircraft. However, the boosted-turbofan aircraft showed a 10% decrease in energy consumption and a 3% reduction in maximum take-off weight. Future studies have to be performed exploring the design space, including all powertrain components, thermal management components, mission parameters and propulsion system layout.

Attention and long short-term memory network for remaining useful lifetime predictions of turbofan engine degradation

Abstract: Machine Prognostics and Health Management (PHM) is often concerned with the prediction of the Remaining Useful Lifetime (RUL) of assets. Accurate real-time RUL predictions enable equipment health assessment and maintenance planning. In this work, we propose a Long Short-Term Memory (LSTM) network combined with global Attention mechanisms to learn RUL relationships directly from time-series sensor data. We use the NASA Commercial Modular Aero- Propulsion System Simulation (C-MAPPS) datasets to assess the performance of our proposed method. We compare our approach with current state-of-the-art methods on the same datasets and show that our results yield competitive results. Moreover, our method does not require previous degradation knowledge, and attention weights can be used to visualise temporal relationships between inputs and predicted outputs.

Performance analysis of an electrically assisted propulsion system for a shortrange civil aircraft

Abstract: With civil aviation growing at around 4.7% per annum, the environmental footprint of aviation is increasing. Moreover, the use of kerosene as a fuel accelerates the depletion of non-renewable fossil fuels and increases global warming. Hence, the aviation industry has to come up with new technologies to reduce its environmental impact and make aviation more sustainable. An electrically assisted propulsion system can combine the benefits of an electrical power source with a conventional turbofan engine. However, the additional electrical system increases the weight of the aircraft and complexity of the power management system. The objective of this research is to analyze the effect of an assistive electrical system on the performance of a turbofan engine for an A320 class aircraft on a short-range mission. The developed simulation model consists of an aircraft performance model combined with a propulsion model. The power management strategy is integrated within the simulation model. With the proposed propulsion system and power management strategy, the electrically assisted propulsion system would be able to reduce fuel burn, total energy consumption, and emissions for short-range missions of around 1000 km.

A Linearization Model of Turbofan Engine for Intelligent Analysis Towards Industrial Internet of Things

Abstract: Big data processing technologies, e.g., multi-sensor data fusion and cloud computing are being widely used in research, development, manufacturing, health monitoring and maintenance of aero-engines, driven by the ever-rapid development of intelligent manufacturing and Industrial Internet of Things (IIoT). This has promoted rapid development of the aircraft engine industry, increasing the aircraft engine safety, reliability and intelligence. At present, the aero-engine data computing and processing platform used in the industrial Internet of things is not complete, and the numerical calculation and control of aero-engine are inseparable from the linear model, while the existing aero-engine model linearization method is not accurate enough to quickly calculate the dynamic process parameters of the engine. Therefore, in this paper, we propose a linear model of turbofan engine for intelligent analysis in IIoT, with the aim to provide a new perspective for the analysis of engine dynamics. The construction of the proposed model includes three steps: First, a nonlinear mathematical model of a turbofan engine is established by adopting the component modeling approach. Then, numerous parameters of the turbofan engine components and their operating data are obtained by simulating various working conditions. Finally, based on the simulated data for the engine under these conditions, the model at the points during the dynamic process is linearized, such that a dynamic real-time linearized model of turbofan engine is obtained. Simulation results show that the proposed model can accurately depict the dynamic process of the turbofan engine and provide a valuable reference for designing the aero-engine control system and supporting intelligent analysis in IIoT.

Commercial Hybrid Electric Aircraft Thermal Management System Design, Simulation, and Operation Improvements

Abstract: Alternative approaches and configurations for the Thermal Management System (TMS) of a parallel hybrid electric propulsion system of a commercial single aisle aircraft have been compared to a baseline approach. A preferred configuration for the acquisition, transport and rejection of heat has been selected and a conceptual design has been completed. The Hybrid Electric Propulsion (HEP) system features a battery pack for energy storage, a low spool motor to assist the fan of a high bypass ratio geared turbofan, and an electric motor drive. The TMS services these HEP loads as well as the traditional engine heat loads including a high spool starter/generator, bearings (for shafts and fan drive system) and the accessory gearbox. The model was executed over a mission on hot day conditions (MIL-STD-210A). A proprietary, object-oriented modeling tool created at the United Technologies Research Center, REHEATS, was used to model the TMS and to optimize it for minimal fuel consumption. By separating the battery and motor drive cooling loops and by allowing battery thermal storage, ram air-cooled heat exchanger weight was reduced to one fifth of the baseline due to the higher temperature operation of the motor drive and due to colder air at the altitude where the battery heat exchanger was sized. The results predict that the TMS of a HEP aircraft increases fuel consumption due to the TMS weight, drag and power demand by approximately 49.0 lbm (~0.75%) per aircraft over a typical mission.

A Control Strategy for Turbine Electrified Energy Management

Abstract: Hybrid-electric propulsion architectures provide the infrastructure to enable additional benefits to the propulsion system that are otherwise unrealizable with the sole use of the current, state-of-the-art, gas-driven, turbine engines. The presence of electric machines (EMs) coupled to the shaft(s) of the turbine engine provide the ability to actively alter the operation of the engine to the benefit of the propulsion system and the aircraft it propels. This is the goal of the Turbine Electrified Energy Management (TEEM) concept, which at its broadest level addresses the management of energy across the electrified propulsion system. Prior work has demonstrated the use of this concept to alter steady-state operation and improve transient operability of a hybrid-electric propulsion system. The main benefits previously illustrated include the elimination of stability bleeds and expansion of the turbomachinery design space in order to enable more efficient designs. This paper focuses on the development of control strategies to implement the TEEM concept, and it explores several possible architecture variants for applying this concept. Comparison studies are conducted between a purely gas-driven turbofan (baseline engine configuration) and TEEM augmented variants of the baseline engine. The variants are distinguished by the shaft(s) that possess an EM. The configurations consider EMs on both shafts, an EM on the high pressure spool (HPS) only, and an EM on the low pressure spool (LPS) only. These configurations are referred to as the dual-spool configuration, the HPS configuration, and LPS configuration, respectively. The studies expose several options in configuring and controlling the system, including the use of a single EM coupled to a single shaft of a two-spool engine to positively impact the operability of both shafts. The studies also demonstrate the use of independently designed controllers for the electric machine(s) that allow for a decoupled control design process.

Nonvolatile particulate matter emissions of a business jet measured at ground level and estimated for cruising altitudes

Abstract: Business aviation is a relatively small but steadily growing and little investigated emission source. Regarding emissions, aircraft turbine engines rated at and below 26.7 kN thrust are certified only for visible smoke and are excluded from the nonvolatile particulate matter (nvPM) standard. Here, we report nvPM emission characteristics of a widely used small turbofan engine determined in a ground test of a Dassault Falcon 900EX business jet. These are the first reported nvPM emissions of a small in-production turbofan engine determined with a standardized measurement system used for emissions certification of large turbofan engines. The ground-level measurements together with a detailed engine performance model were used to predict emissions at cruising altitudes. The measured nvPM emission characteristics strongly depended on engine thrust. The geometric mean diameter increased from 17 nm at idle to 45 nm at take-off. The nvPM emission indices peaked at low thrust levels (7 and 40% take-off thrust in terms of nvPM number and mass, respectively). A comparison with a commercial airliner shows that a business jet may produce higher nvPM emissions from flight missions as well as from landing and take-off operations. This study will aid the development of emission inventories for small aircraft turbine engines and future emission standards.

Videoscope-based inspection of turbofan engine blades using convolutional neural networks and image processing:

Abstract: A typical aircraft engine consists of fans, compressors, turbines, and so on, and each is made of multiple layers of blades. Discovering the site of damages among the large number of blades during ...

Tonal Noise Prediction of a Modern Turbofan Engine With Large Upstream and Downstream Distortion

Abstract: Ultra-high bypass ratio (UHBR) engines are designed as compact as possible and are characterized by a short asymmetric air inlet and heterogeneous outlet guide vanes (OGVs). The flow close to the fan is therefore circumferentially nonuniform (or distorted) and the resulting noise might be impacted. This is studied here at take-off conditions by means of a simulation of the unsteady Reynolds-averaged Navier–Stokes (URANS) equations of a full-annulus fan stage. The model includes an asymmetric air inlet, a fan, heterogeneous OGVs, and homogeneous inlet guide vanes (IGVs). Direct acoustic predictions are given for both inlet and aft noises. A novel hydrodynamic/acoustic splitting method based on a modal decomposition is developed and is applied for the aft noise analysis. The noise mechanisms that are generally considered (i.e., interaction of fan-blade wakes with OGVs and fan self-noise) are shown to be impacted by the distortion. In addition, new sources caused by the interaction between the stationary distortion and the fan blades appear and contribute to the inlet noise.

Design, construction, and testing of an aero-engine starter-generator for the more-electric aircraft

Abstract: This study describes the design, construction, and testing of an aero-engine starter-generator and its associated power electronic converter. A high-speed, permanent magnet machine and a dual-channel machine-facing converter with an electrical power offtake rating of 95 kW have been developed for a small civil turbofan application. The study also describes the more-electric architecture into which the machine and converter are integrated and reviews the multi-faceted performance specification, which is a common feature of machines of this type.

System Noise Assessment of a Tube-and-Wing Aircraft with Geared Turbofan Engines

Abstract: A geared turbofan with an increased bypass ratio promises reduced engine noise generation if compared to conventional turbofan engines with lower bypass ratios. As a result, the dominance of other ...

Nonlinear Dynamic Analysis on Planetary Gears-Rotor System in Geared Turbofan Engines

Abstract: Rotor fatigue and gear noise triggered by nonlinear vibration are the key concerns in Geared Turbofan (GTF) engine which features a new configuration by introducing planetary gears into low-pressur...

Off-design performance analysis of hybridised aircraft gas turbine

Abstract: An advanced geared turbofan with year 2035 technology level assumptions was established and used for the hybridisation study in this paper. By boosting the low-speed shaft of the turbofan with electrical power through the accessory gearbox, a parallel hybrid concept was set up. Focusing on the off-design performance of the hybridised gas turbine, electrical power input to the shaft, defined as positive hybridisation in this context, generally moves the compressor operation towards surge. On the other hand, the negative hybridisation, which is to reverse the power flow direction can improve the part-load operations of the turbofan and minimise the use of compressor handling bleeds. For the pre-defined mission given in the paper, negative hybridisation of descent, approach and landing, and taxi operations with 580 kW, 240 kW and 650 kW, respectively was found sufficient to keep a minimum compressor surge margin requirement without handling bleed.Looking at the hybridisation of key operating points, boosting the cruise operation of the baseline geared turbofan is, however, detrimental to the engine efficiency as it is pushing the cruise operation further away from the energy optimal design point. Without major modifications to the engine design, the benefit of the hybridisation appears primarily at the thermomechanical design point, the hot-day take-off. With the constraint of the turbine blade metal temperature in mind, a 500kW positive hybridisation at hot-day take-off gave cruise specific fuel consumption (SFC) reduction up to 0.5%, mainly because of reduced cooling flow requirement. Through the introduction of typical electrical power system performance characteristics and engine performance exchange rates, a first principles assessment is illustrated. By applying the strategies discussed in the paper, a 3% reduction in block fuel burn can be expected, if a higher power density electrical power system can be achieved.

Current engine noise and reduction technology

Abstract: This article reviews current turbofan engine noise and engine noise reduction technology, specifically focusing on the engine technology of larger passenger jetliners which have entered into service within the last ten (10) years. Important factors in turbofan engine design from a community noise perspective and the sources of noise along with their relative importance are also presented. A review of different engine noise reduction technologies is presented, as well as an estimate of the technology’s readiness level. Finally, potential trade-offs, challenges, and future technology directions are outlined.

DLR TAU-Code uRANS Turbofan Modeling for Aircraft Aerodynamics Investigations

Abstract: In the context of an increased focus on fuel efficiency and environmental impact, turbofan engine developments continue towards larger bypass ratio engine designs, with Ultra-High Bypass Ratio (UHBR) engines becoming a likely power plant option for future commercial transport aircraft. These engines promise low specific fuel consumption at the engine level, but the resulting size of the nacelle poses challenges in terms of the installation on the airframe. Thus, their integration on an aircraft requires careful consideration of complex engine–airframe interactions impacting performance, aeroelastics and aeroacoustics on both the airframe and the engine sides. As a partner in the EU funded Clean Sky 2 project ASPIRE, the DLR Institute of Aerodynamics and Flow Technology is contributing to an investigation of numerical analysis approaches, which draws on a generic representative UHBR engine configuration specifically designed in the frame of the project. In the present paper, project results are discussed, which aimed at demonstrating the suitability and accuracy of an unsteady RANS-based engine modeling approach in the context of external aerodynamics focused CFD simulations with the DLR TAU-Code. For this high-fidelity approach with a geometrically fully modeled fan stage, an in-depth study on spatial and temporal resolution requirements was performed, and the results were compared with simpler methods using classical engine boundary conditions. The primary aim is to identify the capabilities and shortcomings of these modeling approaches, and to develop a best-practice for the uRANS simulations as well as determine the best application scenarios.

Investigation of Infrared Signature of Serpentine Nozzle for Turbofan

Abstract: Infrared stealth technology is one of the essential abilities for advanced stealth aircraft. The exhaust system is the main infrared radiation source of aircraft. The serpentine nozzle is a potenti...

Assessment of a Turbo-Electric Aircraft Configuration with Aft-Propulsion Using Boundary Layer Ingestion

Abstract: In this paper, a turbo-electric propulsion system was analyzed, and its performance was assessed. The aircraft considered here was a single-aisle, medium-range configuration targeting a capacity of 150 Pax. The propulsion concept comprised two boosted geared turbofan engines mounted under-wing. Those main engines were supported by an electrically driven aft-propulsor contributing to the thrust generation and by taking advantage of ingesting the boundary layer of the fuselage for potentially higher levels of propulsive efficiency and allowing for the improved operation of the main engines. The performance assessment as carried out in the context of this paper involved different levels: Firstly, based on the reference aircraft and the detailed description of its major components, the engine performance model for both main engines, as well as for the electrically driven aft-propulsor was set up. The methodology, as introduced, has already been applied in the context of hybrid-electric propulsion and allowed for the aforementioned aircraft sizing, as well as the subsequent gas turbine multi-point synthesis (simulation). A geared turbofan architecture with 2035 technology assumptions was considered for the main engine configuration. The present trade study focused on the design and performance analysis of the aft-propulsor and how it affected the performance of the main engines, due to the electric power generation. In order to allow for a more accurate description of the performance of this particular module, the enhanced streamline curvature method with an underlying and pre-optimized profile database was used to design a propulsor tailored to meet the requirements of the aft propulsor as derived from the cycle synthesis and overall aircraft specification; existing design expertise for novel and highly integrated propulsors could be taken advantage of herein. The resulting performance characteristics from the streamline curvature method were then fed back to the engine performance model in a closely coupled approach in order to have a more accurate description of the module behavior. This direct coupling allowed for enhanced sensitivity studies, monitoring different top-level parameters, such as the thrust/power split between the main engines and the aft propulsor. As a result, different propulsor specifications and fan designs with optimal performance characteristics were achieved, which in return affected the performance of all subsystems considered.

Advanced constraints management strategy for real-time optimization of gas turbine engine transient performance

Abstract: Motivated by the growing technology of control and data processing as well as the increasingly complex designs of the new generation of gas turbine engines, a fully automatic control strategy that is capable of dealing with different aspects of operational and safety considerations is required to be implemented on gas turbine engines. An advanced practical control mode satisfaction method for the entire operating envelope of gas turbine engines is proposed in this paper to achieve the optimal transient performance for the engine. A constraint management strategy is developed to generate different controller settings for short-range fighters as well as long-range intercontinental aircraft engines at different operating conditions by utilizing a model predictive control approach. Then, the designed controller is tuned and modified with respect to different realistic considerations including the practicality, physical limitations, system dynamics, and computational efforts. The simulation results from a verified two-spool turbofan engine model and controller show that the proposed method is capable of maneuverability and/or fuel economy optimization indices while satisfying all the predefined constraints successfully. Based on the parameters, natural frequencies, and dynamic behavior of the system, a set of optimized weighting factors for different engine parameters is also proposed to achieve the optimal and safe operation for the engine at different flight conditions. The paper demonstrates the effects of the prediction length and control horizon; adding new constraints on the computational effort and the controller performance are also discussed in detail to confirm the effectiveness and practicality of the proposed approach in developing a fully automatic optimized real-time controller for gas turbine engines.

Mutual Effect Between Swept-and-Leaned Vanes and Acoustic Liners on Fan Interaction-Noise Reduction

Abstract: The swept-and-leaned vanes and acoustic liners can both be used to reduce the turbofan noise. In this work, an analytical model was proposed under an idealized condition, in which an annular stator...

Analyzing different numerical linearization methods for the dynamic model of a turbofan engine

Abstract: State equations of aircraft engine dynamics usually required for controller design, are not available in closed form, so the dynamic models are commonly linearized numerically. Development of model-based controllers for aeroengine in the recent years necessitates the use of accurate linear models. However, there is no comprehensive study about the accuracy of the linear models obtained from nonlinear engine models. In this paper, the accuracy of different numerical linearization methods for linearizing the dynamic model of a turbofan engine is investigated. For this objective, a thermodynamic model of a two-spool turbofan engine is considered and three various numerical linearization methods are defined. The first method is based on the perturbation technique, including ordinary and central difference perturbation. The second one is a system identification method and the third one is tuning the elements of the matrices of the linear state-space model using genetic algorithm. The accuracy analysis of the presented procedures is performed for both single-input and double-input cases. In the single-input case, the fuel mass flow rate and in the double-input, in addition to the fuel, the bleed air taken from between the two compressors are considered as control variables. Finally, by defining different error criterions, the accuracy of the linearization methods is evaluated. The results show that the linear model obtained from system identification and central difference perturbation methods have higher percentage of compliances compared to the others.

Evaluation of Electrical System Requirements for Implementing Turbine Electrified Energy Management

Abstract: Turbine Electrified Energy Management (TEEM) is a concept concerned with the management of energy in an electrified propulsion system. The management of energy in the hybrid-electric architecture has potential to benefit the turbomachinery and the aircraft it powers. The concept is particularly useful for improving operability during transient operation and could be leveraged to design a better performing engine. The concept utilizes electric machines coupled to the engine shafts and an electric power distribution system that includes energy storage. A controller is used to decide when and how energy is moved around the electrified propulsion system, particularly when considering energy conversion between mechanical and electrical forms. Prior work has shown that the electric machines can be used to supply/or extract supplemental power to/from the engine shafts to improve their operability and achieve or enable propulsion efficiency and performance benefits. However, the previous studies did not consider the practical constraints of the electrical machines and energy storage devices that are required for implementing the TEEM system architecture concept. This paper presents an integrated engine and electrical system model that is used to evaluate the electrical system requirements. The model captures the physics of the conceptual, Advanced Geared Turbofan 30,000lb f (AGTF30) engine, which features advanced technologies such as a compact gas turbine and a variable area fan nozzle. For this work, the engine is augmented with electrical system components that allow for the implementation of the TEEM concept. The evaluation presented suggests the potential of the TEEM concept to provide performance benefits for a turbofan engine.

Using Machine Learning to Predict Core Sizes of High-Efficiency Turbofan Engines

Abstract: With the rise in big data and analytics, machine learning is transforming many industries. It is being increasingly employed to solve a wide range of complex problems, producing autonomous systems that support human decision-making. For the aircraft engine industry, machine learning of historical and existing engine data could provide insights that help drive for better engine design. This work explored the application of machine learning to engine preliminary design. Engine core-size prediction was chosen for the first study because of its relative simplicity in terms of number of input variables required (only three). Specifically, machine-learning predictive tools were developed for turbofan engine core-size prediction, using publicly available data of two hundred manufactured engines and engines that were studied previously in NASA aeronautics projects. The prediction results of these models show that, by bringing together big data, robust machine-learning algorithms and data science, a machine learning-based predictive model can be an effective tool for turbofan engine core-size prediction. The promising results of this first study paves the way for further exploration of the use of machine learning for aircraft engine preliminary design.