Showing papers on "Turbofan published in 2015"

Gas-electric propulsion system for an aircraft

Abstract: In one aspect the present subject matter is directed to a gas-electric propulsion system for an aircraft. The system may include a turbofan jet engine, an electric powered boundary layer ingestion fan that is coupled to a fuselage portion of the aircraft aft of the turbofan jet engine, and an electric generator that is electronically coupled to the turbofan jet engine and to the boundary layer ingestion fan. The electric generator converts rotational energy from the turbofan jet engine to electrical energy and provides at least a portion of the electrical energy to the boundary layer ingestion fan. In another aspect of the present subject matter, a method for propelling an aircraft via the gas-electric propulsion system is disclosed.

Numerical Simulation of Oil Jet Lubrication for High Speed Gears

Abstract: The Geared Turbofan technology is one of the most promising engine configurations to significantly reduce the specific fuel consumption. In this architecture, a power epicyclical gearbox is interposed between the fan and the low pressure spool. Thanks to the gearbox, fan and low pressure spool can turn at different speed, leading to higher engine bypass ratio. Therefore the gearbox efficiency becomes a key parameter for such technology. Further improvement of efficiency can be achieved developing a physical understanding of fluid dynamic losses within the transmission system. These losses are mainly related to viscous effects and they are directly connected to the lubrication method. In this work, the oil injection losses have been studied by means of CFD simulations. A numerical study of a single oil jet impinging on a single high speed gear has been carried out using the VOF method. The aim of this analysis is to evaluate the resistant torque due to the oil jet lubrication, correlating the torque data with the oil-gear interaction phases. URANS calculations have been performed using an adaptive meshing approach, as a way of significantly reducing the simulation costs. A global sensitivity analysis of adopted models has been carried out and a numerical setup has been defined.

Cooled cooling air system for a turbofan engine

Abstract: An exemplary gas turbine engine includes a fan bypass duct (120) defined between a fan nacelle (102) and core cowl of an engine core (104). The engine core (104) includes a cooled cooling air system (110) configured to receive cooling air from a primary flowpath bleed (132) at a diffuser within the engine core (104) and configured to provide cooled cooling air to at least one component within the engine core (104). The cooled cooling air system (110) including an air-air heat exchanger (130).

Aero Gas Turbine Flight Performance Estimation Using Engine Gas Path Measurements

Abstract: Mature gas turbine performance simulation technology has been developed in the past decades and, therefore, gas turbine performance at different ambient and operating conditions can be well predicted if good thermodynamic performance software and necessary engine performance information are available. However, the performance of gas turbine engines of the same fleet may be slightly different from engine to engine due to manufacturing and assembly tolerance and may change over time due to engine degradation. Therefore, it is necessary to monitor and track important performance parameters of gas turbine engines, particularly those that cannot be directly measured, to ensure safe operation of the engines. For that reason, a novel gas turbine performance estimation method using engine gas path measurements has been developed to predict and track engine performance parameters at different ambient, flight, degraded, and part-load operating conditions. The method is based on the influence coefficient matrix of t...

Optimal Cruise Altitude for Aircraft Thermal Management

Abstract: Mission-planning algorithms and trajectory optimization methods for aircraft that use fuel as a heat sink must ensure that fuel temperature limits are not violated at any point in a flight. The problem of determining the cruise altitude that minimizes final fuel tank temperature for jet aircraft that use recirculating fuel to remove waste thermal energy from the aircraft is considered. A heat exchanger transfers energy from the aircraft subsystems to the fuel. A portion of the fuel is burned in a turbojet engine, whereas the remaining unburned fuel is passed through a cooler that transfers some heat from the fuel to the atmosphere. A differential equation that describes the time rate of change of fuel tank temperature is derived based on the principles of conservation of mass and energy. Specific conditions are derived for the cruise altitude that minimizes final tank temperature for flight conditions associated with maximum endurance and range. Expressions are also derived that provide estimates of time ...

Experimental Analysis of the Global Performance and the Flow Through a High-Bypass Turbofan in Windmilling Conditions

Abstract: A detailed study of the air flow through the fan stage of a high-bypass, geared turbofan in windmilling conditions is proposed, to address the key performance issues of this severe case of off-design operation. Experiments are conducted in the turbofan test rig of ISAE, specifically suited to reproduce windmilling operation in an ambient ground setup. The engine is equipped with conventional measurements and radial profiles of flow quantities are measured using directional five-hole probes to characterize the flow across the fan stage and derive windmilling performance parameters. These results bring experimental evidence of the findings of the literature that both the fan rotor and stator operate under severe off-design angle-of-attack, leading to flow separation and stagnation pressure loss. The fan rotor operates in a mixed fashion: spanwise, the inner sections of the rotor blades add work to the flow while the outer sections extract work and generate a pressure loss. The overall work is negative, revealing the resistive loads on the fan, caused by the bearing friction and work exchange in the different components of the fan shaft. The parametric study shows that the fan rotational speed is proportional to the mass flow rate, but the fan rotor inlet and outlet relative flow angles, as well as the fan load profile, remain constant, for different values of mass flow rate. Estimations of engine bypass ratio have been done, yielding values higher than six times the design value. The comprehensive database that was built will allow the validation of 3D Reynolds-averaged Navier–Stokes (RANS) simulations to provide a better understanding of the internal losses in windmilling conditions.

Generic Analysis Methods for Gas Turbine Engine Performance: The development of the gas turbine simulation program GSP

Abstract: Numerical modelling and simulation have played a critical role in the research and development towards today’s powerful and efficient gas turbine engines for both aviation and power generation. The simultaneous progress in modelling methods, numerical methods, software development tools and methods, and computer platform technology has provided the gas turbine community with ever more accurate design, performance prediction and analysis tools. An important element is the development towards generic tools, in order to avoid duplication of model elements for different engine types. This thesis focuses on the development of generic gas turbine system performance simulation methods. This includes the research required to find the optimal mathematical representation of the aero-thermodynamic processes in the gas turbine components in terms of fidelity, accuracy and computing power limitations. The results have been applied in the development of the Gas turbine Simulation Program GSP. GSP is a modelling tool for simulation and analysis of gas turbine system performance. This involves 0-D (i.e. zero-dimensional or parametric) component sub-models that calculate averaged values for parameters such as pressures and temperatures at the gas path stations between the components. The component sub-models are configured (‘stacked’) corresponding to the gas turbine configuration. Component performance is determined by both aero-thermodynamic equations and user specified characteristics, such as turbomachinery performance maps. If higher fidelity is required at a specific location in the system model, 1-D component models can be added to predict the change in gas state or other parameters as a function of a spatial (usually in the direction of a streamline) parameter. Non-linear differential equations (NDEs) are used to represent the conservation laws and other relations among the components. The sets of NDEs are automatically configured depending on the specific gas turbine configuration and type of simulation. Simulation types include design point (DP), steady-state off-design (OD) and transient simulations. The research and development challenge lies in the development of generic, accurate and user friendly system modelling methods with sufficient flexibility to represent any type of gas turbine configuration. The accuracy and fidelity is enhanced by the development of modelling methods capturing secondary effects on component and system performance in 0-D or 1-D sub-models. Object oriented software design methods have been used to accomplish the flexibility objectives, also resulting in a high degree of code maintainability. This allows easy adaptation and extension of functionalities to meet new requirements that are emerging since the start of the development of GSP in its current form (1997). The object oriented architecture and how it relates to the system and component modelling and the ensuing solving of the NDEs, is described in the thesis. An important element has been the development of the gas model with chemical equilibrium and gas composition calculations throughout the cycle. Fuel composition can be specified in detail for accurate prediction of effects of alternative fuels and also detailed emission prediction methods are added. The gas model uses a unique and efficient method to iterate towards chemical equilibrium . The object oriented architecture enabled the embedding of a generic adaptive modelling (AM) functionality in the GSP numerical process and NDEs, providing best AM calculation speed and stability. With AM, model characteristics are adapted for matching specified (often measured) output parameter values for engine test analysis, diagnostics and condition monitoring purposes. The AM functionality can be directly applied to any GSP engine model. The recent trend towards the development of micro turbines (with very high surface-to-volume ratios in the gas path) requires accurate representation of thermal (heat transfer) effects on performance. For this purpose, GSP has been extended with an object oriented thermal network modelling capability. Also, a 1-D thermal model for representing the significant heat soakage effects on micro turbine recuperator transient performance has been developed. For real-time transient simulation, the Turbine Engine Real-Time Simulator (TERTS) modelling tool has been derived from GSP. In TERTS, the methods from GSP are used with fidelity reduced to some extent in order to meet the real-time execution requirements. GSP has been applied to a wide variety of gas turbine performance analysis problems. The adaptive modelling (AM) based gas path analysis functionality has been applied in several gas turbine maintenance environments. Isolation of deteriorated and faulty turbofan engine components was successfully demonstrated using both test rig data and on-wing data measured on-line during flight. For a conceptual design of a 3kW recuperated micro turbine for CHP applications, design point cycle parameters were optimized based on careful component efficiency and loss estimates. Worst and best case scenarios were analysed with GSP determining sensitivity to deviations from the estimates. The predictions have proven very accurate after a test program showing 12% (electric power) efficiency on the first prototype. For increasing the efficiency towards 20%, GSP was used to predict the impact of several design improvements on system efficiency. GSP was used to study the effects on performance and losses of scaling micro turbines in the range of 3 to 36 kW. At small scales, turbomachinery losses become relatively large due to the smaller Reynolds number (larger viscous losses) and other effects. The scale effects have been analysed and modelled for the turbine and compressor and GSP has been used to predict the effects on system efficiency. Other applications include prediction of cumulative exhaust gas emissions of the different phases of commercial aircraft flights, simulation of thermal load profiles for hot section lifing studies, alternative fuel effect studies, performance prediction of vertical take-off propulsion systems and reverse engineering studies. The object oriented design of GSP has proven its value and has provided the building blocks for an ever increasing number of component models, adaptations and extensions. The flexibility of GSP is demonstrated with the modelling of novel cycles, including a parallel twin spool micro turbine with a single shared combustor, a rotating combustor micro turbine concept, a modern heavy duty gas turbine with a second (reheat) combustor and a multi-fuel hybrid turbofan engine, also with a reheat combustor. Several new capabilities have been developed following new requirements from the user community, using the original object oriented framework and component model classes. In the future, new technologies may replace today’s simulation tools. Maybe even the concept of modelling and simulation as we know it today will entirely change. However, as long as gas turbines and related systems will be developed and operated, there will be a need to understand their behaviour. The fundamental physics behind this will not change nor will the equations describing the processes. In that sense, GSP can be seen as a phase in the development of gas turbine modelling and simulation technology. An interesting question would be, how long will GSP remain before it is left behind for new ways. A lot will depend on the ability of GSP and its developers to adapt to future needs and also future opportunities emerging from new modelling, simulation, and computer and software technologies. So far however, GSP has proven a remarkable track record and will be around for quite a while, serving many scientists and engineers interested in gas turbine system performance analysis and simulation.

First and Second Law Analysis of Intercooled Turbofan Engine

Abstract: Although the benefits of intercooling for aero-engine applications have been realized and discussed in many publications, quantitative details are still relatively limited. In order to strengthen the understanding of aero-engine intercooling, detailed performance data on optimized intercooled (IC) turbofan engines are provided. Analysis is conducted using an exergy breakdown, i.e., quantifying the losses into a common currency by applying a combined use of the first and second law of thermodynamics. Optimal IC geared turbofan engines for a long range mission are established with computational fluid dynamics (CFD) based two-pass cross flow tubular intercooler correlations. By means of a separate variable nozzle, the amount of intercooler coolant air can be optimized to different flight conditions. Exergy analysis is used to assess how irreversibility is varying over the flight mission, allowing for a more clear explanation and interpretation of the benefits. The optimal IC geared turbofan engine provides a 4.5% fuel burn benefit over a non-IC geared reference engine. The optimum is constrained by the last stage compressor blade height. To further explore the potential of intercooling the constraint limiting the axial compressor last stage blade height is relaxed by introducing an axial radial high pressure compressor (HPC). The axial–radial high pressure ratio (PR) configuration allows for an ultrahigh overall PR (OPR). With an optimal top-of-climb (TOC) OPR of 140, the configuration provides a 5.3% fuel burn benefit over the geared reference engine. The irreversibilities of the intercooler are broken down into its components to analyze the difference between the ultrahigh OPR axial–radial configuration and the purely axial configuration. An intercooler conceptual design method is used to predict pressure loss heat transfer and weight for the different OPRs. Exergy analysis combined with results from the intercooler and engine conceptual design are used to support the conclusion that the optimal PR split exponent stays relatively independent of the overall engine PR.

Tomographic Background Oriented Schlieren Applications for Turbomachinery (Invited)

Abstract: Tomographic Background Oriented Schlieren (BOS) is a fast and non-intrusive measurement technique to reconstruct three-dimensional density fields. An overview is given of the application of tomographic BOS to turbomachinery. Measurements taken from a double free jet of air, the flow behind turbine blades in a linear cascade wind tunnel, and the exhaust jet of a helicopter engine are summarized. The scope of BOS is extended in the present paper by performing non-tomographic BOS measurements on different turbofan engine exhaust jets using one camera. The three-dimensional BOS measurements are analyzed by means of a tomographic algorithm, based on the filtered back-projection. The results of the two-dimensional BOS measurements of turbofan engines show a potential for identifying differences in the condition of the engines by measuring their exhaust jet. Based on the results of the tomographic measurements and the results of the turbofan engine measurements, tomographic BOS measurements are shown to be a promising method for detecting and locating defects in jet engines by measuring their exhaust jet.

Validation and flow structure analysis in a turbofan stage at windmill

Abstract: In the present study, the flow through the fan stage of a high bypass ratio turbofan at windmill is studied numerically. First, steady mixing plane simulations are validated against detailed experi...

Optimization of Compressor Variable Geometry Settings Using Multi-Fidelity Simulation

Abstract: Variable geometry blade rows are a common instrument to avoid compressor instabilities which occur especially at low- and full-speed operation of gas turbines. The operating settings of variable stator vanes (VSVs) are typically obtained from expensive and time consuming performance rig tests and are not known during the early design phase of a gas turbine. During preliminary design of the overall engine it is common practice to use default component characteristics based on considerable engineering experience. These can deviate substantially at off-design and often do not properly account for the impact of changes in component geometry. As a solution, multi-fidelity simulation often referred to as zooming or variable complexity analysis is applied. This proceeding facilitates a transfer of single component performance characteristics obtained in mid- or high-fidelity analysis to a full gas turbine system analysis based on lower resolution level. The purpose of this study is to present a multidisciplinary numerical optimization methodology to define ideal blade row staggering of variable compressor stator vanes during the early preliminary design phase using multi-fidelity simulation. The objective of the resultant multi-dimensional constraint optimization is to find the best solution for the entire gas turbine system for a set of discrete operating points. For the assessment a generic turbofan engine model is designed by taking into account top level engine requirements from an assumed airframe and flight mission scenario. Based on the performance calculation a full 3-D axial multistage high pressure compressor (HPC) is designed. The assumed design considerations are summarized and the modelling techniques are presented. The optimization of VSV staggering mentioned above is carried out by re-staggering the variable geometry blade rows of the high-fidelity HPC and run a full 2-dimensional through-flow calculation. Results are then automatically transferred to the 0-dimensional engine model to calculate the engine overall performance. A Pareto optimized blade row staggering is found by taking into account the surge margin and the specific fuel consumption of the entire engine system as objective functions of the optimization process. Simultaneously several constraints such as DeHaller numbers and diffusion factors are considered. The optimization process chain and the tool coupling are summarized and described in detail. The resulting VSV staggering for a set of discrete operating points is shown.

Performance characteristics and optimisation of a geared intercooled reversed flow core engine

Abstract: Intercooled turbofan cycles allow higher overall pressure ratios to be reached, which gives rise to improved thermal efficiency. In addition, intercooling allows for the size, weight and exhaust jet velocity of the core to be reduced. For an optimum jet velocity ratio and fixed thrust, the fan pressure ratio and specific thrust are also reduced, which benefits propulsive efficiency. A new intercooled core concept is proposed in this paper, which promises to alleviate limitations identified in previous intercooled turbofan designs. This concept facilitates the installation of the intercooler and reduces core losses at high overall pressure ratios. This engine concept takes advantage of intercooling and the arrangement of the high pressure spool to reach and exceed overall pressure ratios of 80. In addition, given the reduction in core size, bypass ratios beyond 14 have been considered. In order to identify efficiency gains and performance characteristics which are due to the novel arrangement alone, the ge...

Tonal Noise Prediction of a Turbofan with Heterogeneous Stator and Bifurcations

Abstract: The interaction of wakes generated by a fan with the outlet guide vanes occurring at the blade-passing frequency and its harmonics is mainly responsible for aeroengine tonal noise emission in approach conditions. Conventional rotor–stator interaction models assume axisymmetric rows and quasi-annular ducts. However, the stator of new engines is characterized by nonidentical vanes (so-called heterogeneous outlet guide vane) and integrates two internal bifurcations up to the nacelle outlet. These new technologies invalidate the existing tools adopted by engine manufacturers at the design stage. For this reason, hybrid methodologies based on a three-dimensional unsteady Reynolds-averaged Navier–Stokes simulation considering the complete geometry of a modern Snecma engine model are investigated in this paper. Unsteady Reynolds-averaged Navier–Stokes simulation output data are postprocessed using different integral methods to assess the impact of the heterogeneity on angular mode distribution (compared to an id...

System Noise Assessment of Blended-Wing-Body Aircraft with Open Rotor Propulsion

Abstract: An aircraft system noise study is presented for the hybrid wing–body aircraft concept with open-rotor engines mounted on the upper surface of the airframe. The aircraft chosen for the study is of a size comparable to the Boeing 787 aircraft. It is shown that, for such a hybrid wing–body aircraft, the cumulative effective perceived noise level is about 24 dB below the current aircraft noise regulations of stage 4. Although this makes the design acoustically viable in meeting the regulatory requirements, even with the consideration of more stringent noise regulations in the next decade or so, the design will likely meet stiff competition from aircraft with turbofan engines. The noise levels of the hybrid wing–body design are held up by the inherently high noise levels of the open-rotor engines and the limitation on the shielding benefit due to the practical design constraint on the engine location. Furthermore, it is shown that the hybrid wing–body design has high levels of noise from the main landing gear,...

Investigation of Fan-Wake/Outlet-Guide-Vane Interaction Broadband Noise

Abstract: Fan-wake/outlet-guide-vane interaction broadband noise in turbofan jet engines is studied. The mechanism and some issues are first discussed using a two-dimensional gust-prediction model. An oblique gust-prediction model is then developed. Quasi-three-dimensional unsteady lift is calculated using a two-dimensional equivalence method. It is coupled with annular duct modes to obtain the sound power spectrum density. Spanwise turbulence integral length scales and their impact on power spectrum density predictions are investigated. A spanwise integration limit suitable for the complete frequency range is proposed. The model is validated using the NASA Source Diagnostic Test data. Sound power scaling with vane count B is examined. If solidity is maintained, the cascade response does not converge on the single-airfoil response, even for low vane counts. The sound power varies inversely with B at low frequency; it scales with B at very high frequency. The power spectrum density trend with the fan tip Mach number...

Fan Response to Inlet Swirl Distortions Produced by Boundary Layer Ingesting Aircraft Configurations

Abstract: Boundary layer ingesting aircraft configurations create substantial flow distortions in inlets of turbofan engines and alter propulsive efficiency and performance. The swirl distortion component of these inlet flow profiles changes the incidence angle of air entering the fan which alters the amount of flow turning and work performed by the fan. This paper presents the results of an experimental investigation of fan response to inlet swirl distortions in an operating turbofan engine. Three-dimensional flow measurements were taken in the bypass annulus behind the fan rotor of a Pratt & Whitney Canada JT15D-1 turbofan research engine rig experiencing inlet distortion from a StreamVane swirl distortion generator. The StreamVane was designed to impose a swirl distortion profile matching a computational fluid dynamics model of a conceptual blended wing body aircraft engine inlet. Results from the investigation revealed that the swirl distortion altered the fan rotor flow turning, persisted downstream of the fan rotor plane, and entered the fan exit guide vanes. When compared to non-distorted inlet flow, the average fan outlet total-to-atmospheric pressure ratio decreased approximately 1.5%, while the flow angles exiting the fan deviated by up to ±10°. Both results indicate reductions in propulsor effectiveness and support the requirement for distortion tolerant fan optimization.

Harmonic and Broadband Separation of Noise from a Small Ducted Fan

Abstract: In the study of noise from propellers and ducted fans, rigorous signal decomposition into harmonic and broadband components is essential for the development of high-delity predictive models. Current spectral methods and phase averaging techniques lack the temporal resolution to compensate for uctuations in operating condition intrinsic to real world experiments. In this paper we use a Vold-Kalman lter to extract the tonal and broadband content of noise from a small ducted fan simulating the conditions of an ultrahigh-bypass turbofan engine. The fan operated at pressure ratio of 1.15 and tip Mach number of 0.61. The investigation includes time traces, narrowband spectra, one-third octave spectra, and overall sound pressure level. The energies of the tonal and broadband components are similar at low frequency, while the broadband component dominates at high frequency. In addition, there are distinct dierences in the directivities of the two components. The trends are in general agreement with NASA large-scale fan tests at transonic conditions.

Evaluation of performance properties of two combustor turbofan engine

Abstract: In air-transport two or three shafts high bypass ratio turbofan engines and turboprop engines are the dominant kind of propulsion. Both of the types found their use in aircrafts because of their profitable performance characteristics. First of all, this is low specific fuel consumption, which is about 20% of the value of this parameter for turbojet engines [15, 18]. Turboprop engines are characterized by a lower specific fuel consumption than high bypass turbofan engines. However, a significant limitation of these engines is a lower cruise speed which follows from limitations connected with a significant decrease of propellers perRobert JAkubowski

Embedded Turbofan Deicer System

Abstract: An embedded turbofan deicer system (ETDS) may eliminate the ingested ice crystal icing problem plaguing high bypass turbofan engines operating at high altitudes near convective tropical storms: icing occurring on the surfaces of the engine's rotating engine spinner, fan blades, low pressure compressor casing and low pressure compressor and causing loss of power and on occasion engine flameouts. The invention supplies electricity to heat these engine parts using at least one reversed permanent magnet electric generator (reversed PMEG) driven by the turbofan's central drive shaft with all parts of the ETDS mounted internal to the engine in presently unused internal spaces without requiring modifications to the existing engine. All electric power produced by the rotating reversed PMEG supplied directly to rotating engine parts requiring heat for deicing. A unique method to deice metal, composite and metal/composite fan blades is included in the invention using electricity from the reversed PMEG.

Concept description and assessment of the main features of a geared intercooled reversed flow core engine

Abstract: Intercooled turbofan cycles allow higher overall pressure ratios to be reached which gives rise to improved thermal efficiency. Intercooling also allows core mass flow rate to be reduced which facilitates higher bypass ratios. A new intercooled core concept is proposed in this paper which promises to alleviate limitations identified with previous intercooled turbofan designs. Specifically, these limitations are related to core losses at high overall pressure ratios as well as difficulties with the installation of the intercooler. The main features of the geared intercooled reversed flow core engine are described. These include an intercooled core, a rear-mounted high-pressure spool fitted rearwards of the low-pressure spool as opposed to concentrically as well as a mixed exhaust. In these studies, the geared intercooled reversed flow core engine has been compared with a geared intercooled straight flow core engine with a more conventional core layout. This paper compares the mechanical design of the high-pressure spools and shows how different high-pressure compressor and high-pressure turbine blade heights can affect over-tip leakage losses. In the reversed configuration, the reduction in high-pressure spool mean diameter allows for taller high-pressure compressor and turbine blades to be adopted which reduces over-tip leakage losses. The implication of intercooler sizing and configuration, including the impact of different matrix dimensions, is assessed for the reversed configuration. It was found that a 1-pass intercooler would be more compact although a 2-pass would be less challenging to manufacture. The mixer performance of the reversed configuration was evaluated at different levels of mixing effectiveness. This paper shows that the optimum ratio of total pressure in the mixing plane for the reversed flow core configuration is about 1.02 for a mixing effectiveness of 80%. Lower mixing effectiveness would result in a higher optimum ratio of total pressure in the mixing plane and fan pressure ratio.

Nonlinear Dynamic Modeling of a Supersonic Commercial Transport Turbo-Machinery Propulsion System for Aero-Propulso-Servo-Elasticity Research

Abstract: This paper covers the development of an integrated nonlinear dynamic model for a variable cycle turbofan engine, supersonic inlet, and convergent-divergent nozzle that can be integrated with an aeroelastic vehicle model to create an overall Aero-Propulso-Servo-Elastic (APSE) modeling tool. The primary focus of this study is to provide a means to capture relevant thrust dynamics of a full supersonic propulsion system by using relatively simple quasi-one dimensional computational fluid dynamics (CFD) methods that will allow for accurate control algorithm development and capture the key aspects of the thrust to feed into an APSE model. Previously, propulsion system component models have been developed and are used for this study of the fully integrated propulsion system. An overview of the methodology is presented for the modeling of each propulsion component, with a focus on its associated coupling for the overall model. To conduct APSE studies the de- scribed dynamic propulsion system model is integrated into a high fidelity CFD model of the full vehicle capable of conducting aero-elastic studies. Dynamic thrust analysis for the quasi-one dimensional dynamic propulsion system model is presented along with an initial three dimensional flow field model of the engine integrated into a supersonic commercial transport.

Modeling of Broadband Liners Applied to the Advanced Noise Control Fan

Abstract: The broadband component of fan noise has grown in relevance with an increase in bypass ratio and incorporation of advanced fan designs. Therefore, while the attenuation of fan tones remains a major factor in engine nacelle acoustic liner design, the simultaneous reduction of broadband fan noise levels has received increased interest. As such, a previous investigation focused on improvements to an established broadband acoustic liner optimization process using the Advanced Noise Control Fan (ANCF) rig as a demonstrator. Constant-depth, double-degree of freedom and variable-depth, multi-degree of freedom liner designs were carried through design, fabrication, and testing. This paper addresses a number of areas for further research identified in the initial assessment of the ANCF study. Specifically, incident source specification and uncertainty in some aspects of the predicted liner impedances are addressed. This information is incorporated in updated predictions of the liner performance and comparisons with measurement are greatly improved. Results illustrate the value of the design process in concurrently evaluating the relative costs/benefits of various liner designs. This study also provides further confidence in the integrated use of duct acoustic propagation/radiation and liner modeling tools in the design and evaluation of novel broadband liner concepts for complex engine configurations.

Modeling of Start-Up From Engine-Off Conditions Using High Fidelity Turbofan Engine Simulations

Abstract: Engine models are widely used to simulate the engine behavior at steady state and transient operating conditions over the full flight envelope. Within the engine development process such simulations are used to support component design, evaluate engine performance, operability and test data, as well as to develop and optimize the engine controls. Recent developments have raised interest in the modeling of start-up processes of turbofan engines in order to support the definition of sufficient engine control laws. This implies that simulations are started at a condition where the engine shafts are static and temperatures and pressures are equal to ambient. During start-up the engine can only be operated transiently through the sub-sub-idle region (near zero speed) using a starter torque. The activity presented here was targeted to support the development of industrial-standard high-fidelity turbofan engine models capable of simulating start-up, shutdown or windmilling operation. Within the three previously mentioned cases starting from an engine-off condition, ground start from zero-speed is the most challenging in terms of physical and numerical modeling. For this reason, this paper concentrates on that case only. Zero mass flow and speed at the beginning of the simulation impose a set of special problems that do not exist in standard simulations: the modeling of a static engine-off condition, the modeling of static friction, and the modeling of reverse flows. The requirement to support an existing industrial model development process also made it necessary to apply the same quality of physical modeling to start-up simulations as would be the case for above-idle engine simulations. The physical effects present during engine start are discussed and modeling solutions are presented. Finally, results of a dry crank simulation are presented and discussed, illustrating that the expected effects are present and that the simulation is capable of predicting the correct trends.© 2015 ASME