Showing papers on "Nacelle published in 2004"

Method and apparatus for noise abatement and ice protection of an aircraft engine nacelle inlet lip

Abstract: An aircraft engine nacelle comprises: (a) an inlet lip and a skin having internal and external surfaces; (b) a noise abatement structure such as an acoustic panel located on the internal surface of the nacelle skin; and (c) an electrically powered de-icing system located on the external surface of the nacelle skin and in electrical connection to a power source. A method for de-icing and abating noise from an aircraft nacelle comprises: (a) providing a noise abatement structure such as an acoustic panel located on the internal surface of the nacelle skin; (b) providing an electrically powered de-icing system on the external surface of the nacelle skin; and (c) applying an electric current to the electrically powered de-icing system. The nacelle skin may be a perforated skin, and the de-icing system comprises a wire mesh bonded to the external surface of the perforated skin. The method and nacelle permit the use of noise abatement structures such as acoustic panels for noise reduction while advantageously avoiding detrimental high temperatures associated with conventional de-icing systems.

Wind turbine generator, active vibration damping method for the same, and wind turbine tower

Abstract: A wing turbine generator, an active vibration damping method for the generator, and a wind turbine tower, where the reduction in vibration of the wind turbine generator and the wind turbine tower can be achieved at a low cost. Acceleration of vibration of a nacelle (13) is measured by an accelerometer (17) fixed to the nacelle (13). Based on the acceleration measured, an active vibration damping section (20) calculates a wind turbine blade (12) pitch angle that causes the wind turbine blade (12) to produce thrust to cancel vibration of the nacelle (13), and outputs the result as a damping blade pitch angle command δθ*. On the other hand, a pitch angle control section (30) calculates a wind turbine blade (12) pitch angle for setting the output to a specific value and outputs the result as a blade pitch angle command θ* for output control. A subtractor (40) superposes the vibration damping blade pitch angle command δθ* on the output controlling blade pitch angle command θ* and controls the pitch angle of the wind turbine blade based on a superposed blade pitch angle command.

Wind turbine generator, active damping method thereof, and windmill tower

Abstract: A wind turbine generator, an active damping method thereof, and a windmill tower in which vibrations of the wind turbine generator itself or the windmill tower can be reduced at low cost are provided. The acceleration due to vibrations of a nacelle is detected with an accelerometer attached to the nacelle. In an active damping unit, a pitch angle of windmill blades for generating a thrust on the windmill blades so as to cancel out the vibrations of the nacelle is calculated on the basis of the acceleration, and the pitch angle is output as a blade-pitch-angle command δθ* for damping. On the other hand, in a pitch-angle control unit, a pitch angle of the windmill blades for controlling the output to be a predetermined value is calculated, and the pitch angle is output as a blade-pitch-angle command θ* for output control. The blade-pitch-angle command δθ* for damping is combined with the blade-pitch-angle command θ* for output control using a subtracter. The pitch angle of the windmill blades is controlled on the basis of the resulting blade-pitch-angle command after combining.

Aeroacoustic Scattering via the Equivalent Source Method

Abstract: A computational method for predicting the scattering of incident engine noise by an airframe in a uniform flow field has been developed. The method is based on the equations of time harmonic, linearized acoustics and employs the equivalent source method for solving an exterior Helmholtz equation boundary value problem. Details of the governing equation development and numerical solution process are presented. The solution methodology has been implemented in a computer program, called the Fast Scattering Code, which accepts user defined operating conditions and aircraft component geometries and simulates the scattered acoustic pressure and/or velocity fields at user specified locations. The code features fast numerical calculations that can be performed on personal computers or workstations for moderate excitation frequencies. Several aeroacoustics scattering cases involving model nacelle, wing, and airframe components are presented to demonstrate the program capabilities.

Method and apparatus for flight control of tiltrotor aircraft

Abstract: A method and apparatus provide for automatically controlling the flight of a tiltrotor aircraft while the aircraft is in flight that is at least partially rotor-borne. The method and apparatus provide for automatically tilting nacelles in response to a longitudinal-velocity control signal so as to produce a longitudinal thrust-vector component for controlling longitudinal velocity of the aircraft. Simultaneously, cyclic swashplate controls are automatically actuated so as to maintain the fuselage in a desired pitch attitude. The method and apparatus also provide for automatically actuating the cyclic swashplate controls for each rotor in response to a lateral-velocity control signal so as to produce a lateral thrust-vector component for controlling lateral velocity of the aircraft. Simultaneously, collective swashplate controls for each rotor are automatically actuated so as to maintain the fuselage in a desired roll attitude. The method and apparatus provide for yaw control through differential longitudinal thrust produced by tilting the nacelles.

Arrangement for bleeding the boundary layer from an aircraft engine

Abstract: An aircraft engine comprising a nacelle, a first wall and fan outlet guide vanes. The fan outlet guide vanes comprises a plurality of stator vanes extending between a second wall and a third wall. The nacelle having apertures at a region of low pressure. A means to bleed fluid from a region of high pressure at one or more of the first wall, the second wall, the third wall or the stator vanes and at least one duct to connect the means to bleed fluid from the region of high pressure to the at least one aperture in the nacelle. The static pressure at the high pressure region is greater than that in the low pressure region such that at least some of the boundary layer of the fluid flows through the at least one duct to the at least one aperture in the nacelle.

Annular acoustic panel

Abstract: An aircraft engine assembly (10) is provided that is adapted to reduce noise produced by an engine (14) included in the engine assembly. The engine assembly (10) includes a nacelle (26) having an inlet section (34) and a main section (38) that is houses the engine (14) and fan assembly (18) associated with the engine. The inlet section (34) is coupled to the main section (38) at a main bulkhead (42) junction between the inlet section (34) and the main section (38) . A one piece annular acoustic panel (46) is located within a recess in an internal wall (54) of the nacelle (26) . The annular acoustic panel (46) extends from a forward portion of the inlet section (34) to a forward portion of the main section (38) such that the bulkhead (42) is covered by the annular acoustic panel (46).

Transonic Drag Prediction on a DLR-F6 Transport Configuration Using Unstructured Grid Solvers

Abstract: A second international AIAA Drag Prediction Workshop (DPW-II) was organized and held in Orlando Florida on June 21-22, 2003. The primary purpose was to inves- tigate the code-to-code uncertainty. address the sensitivity of the drag prediction to grid size and quantify the uncertainty in predicting nacelle/pylon drag increments at a transonic cruise condition. This paper presents an in-depth analysis of the DPW-II computational results from three state-of-the-art unstructured grid Navier-Stokes flow solvers exercised on similar families of tetrahedral grids. The flow solvers are USM3D - a tetrahedral cell-centered upwind solver. FUN3D - a tetrahedral node-centered upwind solver, and NSU3D - a general element node-centered central-differenced solver. For the wingbody, the total drag predicted for a constant-lift transonic cruise condition showed a decrease in code-to-code variation with grid refinement as expected. For the same flight condition, the wing/body/nacelle/pylon total drag and the nacelle/pylon drag increment predicted showed an increase in code-to-code variation with grid refinement. Although the range in total drag for the wingbody fine grids was only 5 counts, a code-to-code comparison of surface pressures and surface restricted streamlines indicated that the three solvers were not all converging to the same flow solutions- different shock locations and separation patterns were evident. Similarly, the wing/body/nacelle/pylon solutions did not appear to be converging to the same flow solutions. Overall, grid refinement did not consistently improve the correlation with experimental data for either the wingbody or the wing/body/nacelle pylon configuration. Although the absolute values of total drag predicted by two of the solvers for the medium and fine grids did not compare well with the experiment, the incremental drag predictions were within plus or minus 3 counts of the experimental data. The correlation with experimental incremental drag was not significantly changed by specifying transition. Although the sources of code-to-code variation in force and moment predictions for the three unstructured grid codes have not yet been identified, the current study reinforces the necessity of applying multiple codes to the same application to assess uncertainty.

Laminar flow nacelle for an aircraft engine

Abstract: A laminar flow nacelle for an aircraft engine ( 10 ) has an outer member ( 26 ) defining an aerodynamic shape. The nacelle ( 24 ) has an inner member ( 28 ) defining a chamber ( 30 ) with the outer member ( 26 ) of the nacelle ( 24 ). The outer member ( 26 ) of the nacelle ( 24 ) has a porous region ( 32 ) at a first region ( 34 ) of the outer member ( 26 ) and the porous region ( 32 ) allows a flow of fluid into the chamber ( 30 ). A duct ( 36 ) connects the chamber ( 30 ) to an aperture ( 38 ) in the outer member ( 26 ) at a second region ( 40 ) of the outer member ( 26 ) downstream of the first region ( 34 ). In operation the static pressure at the first region ( 34 ) is greater than the static pressure at the second region ( 40 ) such that the boundary layer of the fluid flows through the porous region ( 32 ) at the first region ( 34 ) through the duct ( 36 ) to the aperture ( 38 ) at the second region ( 40 ). The first region ( 34 ) extends between 10% and 20% of the chord length of the nacelle ( 24 ) from the highlight ( 42 ) of the nacelle ( 24 ). The second region ( 40 ) extends between 50% and 70% of the chord length of the nacelle ( 24 ) from the highlight ( 42 ).

Toggle interlocked thrust reverser

Abstract: A fan thrust reverser (36) includes a nacelle (16) having radially outer and inner skins (38, 40). An outer door (54, 56) is disposed in the outer skin (38), and mounted to the nacelle (16) at a hinge joint (70). A toggle link (68) is pivotally joined between the outer door (54, 56) and the nacelle (16) for latching stowed the outer door in the nacelle. An actuator (62) is provided for rotating the outer door (54, 56) about the hinge joint (70) for deploying the door outwardly from the nacelle and toggling off the toggle link (68), and stowing inwardly the outer door upon reverse rotation thereof and toggling on the toggle link (68) to latch the door stowed in the nacelle.

Fan cowl door elimination

Abstract: A nacelle for housing an aircraft jet engine. The jet engine has a fan case and a portion disposed downstream of the fan case relative to a direction of airflow through the jet engine. The nacelle comprises an inlet for receiving airflow, a fan cowl panel for covering a forward portion of the fan case, and a thrust reverser having a longitudinal length sufficient to cover the downstream portion of the jet engine in addition to a rearward portion of the fan case. Opening the thrust reverser enables access to an entire area formed by the downstream portion as well as the rearward portion of the fan case.

Ejector cooling of outer case for tip turbine engine

Abstract: A tip turbine engine (10) includes a combustor (30) radially outward of a fan. In order to reduce the heat transfer from the combustor and the high-energy gas stream generated by the combustor, a cold air ejector (38) radially outward of the combustor extends from a forward end of the nacelle (12) to a point rearward of the combustor and an exhaust mixer (110). The cold air ejector includes an annular inlet (17) at the forward end of the nacelle. The cold air ejector draws air over the outer engine case (39) to provide a boundary between the nacelle and the hot outer engine case. The layer of air being pulled past the engine case ejects the heat, thereby preventing the heat from escaping into the nacelle or engine bay.

On the Rotor Effects upon Nacelle Anemometry for Wind Turbines

Abstract: The objective of this paper is to study the typical atmospheric turbulent flow around the rotor and nacelle of a HAWT, in order to (i) investigate the impact of the turbine's rotating blades on the flow field over the nacelle, i.e. the rotor-nacelle interaction; (ii) assess the appropriate anemometer location on the nacelle, and therefore (iii) establish the relationship between wind speed measured near the nacelle and free stream wind speed. The paper presents a numerical method for investigating the effects of rotating rotor blades on the nacelle anemometry of a horizontal axis wind turbine (HAWT). The flow field around the turbine and nacelle is described by the Reynolds averaged Navier-Stokes equations. The κ – ϵ model has been chosen for the closure of time-averaged turbulent flow equations. The rotor is modelled using the actuator-disk concept. The simulation results were performed using a commercial wind turbine rated at 750kW. In general, good qualitative agreements have been found, supporting the...

Wind wheel for wind power generation

Abstract: [PROBLEMS] A wind wheel for wind power generation, where those members of the wheel that are placed on a nacelle can be reduced in size and weight and maintenance of the wheel is facilitated. [MEANS FOR SOLVING PROBLEMS] A main shaft (11), a speed increasing unit (12) for increasing the rotation speed of the main shaft (11) to output the result, and a generator (13) driven by the output of the speed increasing unit(12) are arranged on a nacelle base plate (6) constituting a nacelle (3). The main shaft (11) is attached to the head of an input shaft (12a) of the speed increasing unit (12) with a double-row taper roller bearing (16) in between. The main shaft (11) is attached to a wall section (W1) of a nacelle base plate (6) with the double-row roller bearing (16) interposed between them, so that the main shaft (11) is supported at the wall section (W1) through the double-row roller bearing (16). The main shaft (11) is formed in a substantially annular shape whose outer diameter (D1) is larger than the axial length (L1).

Vibration reduction system for a wind turbine

Abstract: A wind turbine includes a tower, a nacelle supported at an upper end of a tower, a rotor having at least one blade and being arranged at the nacelle, and a vibration load reduction system disposed at either the tower or the nacelle. The vibration load reduction system includes a base, at least two columns extending from the base, and a flowable mass located within the base and the at least two columns.

Wind power generating device, control method for wind power generating device and computer program

Abstract: PROBLEM TO BE SOLVED: To provide technology enabling to detect a gust of wind beforehand and take countermeasure against a gust of wind such as angle change of a blade without requiring an observation tower. SOLUTION: In a wind power generating device provided with a tower erectly provided on the ground, a nacelle fixed on the tower, and a plurality of blades rotatably fixed on the nacelle via a hub, a Doppler anemometer capable of measuring wind speed in front of the same by sending and receiving sound wave or electromagnetic wave and a blade angle control means controlling angle change of the blade including feathering are provided on the nacelle or the hub, the blade angle control means changes angle of the blade when the Doppler anemometer detects wind speed of a predetermined value or greater. COPYRIGHT: (C)2006,JPO&NCIPI

Propagation and Decay of Shock Waves in Turbofan Engine Inlets

Abstract: Numerical experiments are carried out to investigate the tone noise radiates from a turbofan engine inlet under conditions at which the relative flow past the rotor tip is supersonic. Under these conditions, the inlet tone noise is generated by the upstream-propagating rotor-locked shock wave field. The spatial evolution of this shock system is studied numerically for flows through two basic hard-walled configurations: a slender nacelle with large throat area and a thick nacelle with reduced throat area. With the flight Mach number set to 0.25, the spatial evolution of the acoustic power through the two inlets reveals that the reduced throat area inlet provides superior attenuation. This is attributed to the greater mean flow acceleration through its throat and is qualitatively in accord with one-dimensional theory, which shows that shock dissipation is enhanced at high Mach numbers. The insertion of a uniform extension upstream of the fan is shown to yield greater attenuation for the inlet with large throat area, while the acoustic performance of the reduced throat area inlet is degraded. This occurs because the interaction of the nacelle and spinner potential fields is weakened, resulting in a lower throat Mach number. The effect of forward flight on the acoustic power radiated from the two inlets is also investigated by examining a simulated static condition. It is shown that the slender nacelle radiated significantly less power at the static condition than in flight, whereas the power levels at the two conditions are comparable for the thick nacelle. The reason for this behavior is revealed to be a drastic overspeed near the leading edge of the slender nacelle, which occurs to a lesser degree in the case of the thick inlet. This has implications for ground acoustic testing of aircraft engines, which are discussed.Copyright © 2004 by ASME

Recessed engine nacelle

Abstract: A gas turbine engine nacelle (16) includes an inner skin (38) surrounded by a radially outer skin (40). The inner skin (38) terminates at an exhaust outlet (44). The outer skin (40) terminates at a recess (46) in the inner skin (38) extending into a closed cavity (48) under the outer skin (40).

Multidisciplinary Optimization of a Supersonic Inlet Using a Cartesian CFD Method

Abstract: A Cartesian-based Euler method is coupled with a propulsion system simulator to form a multidisciplinary analysis method for inlet/nacelle geometries. This analysis method is in turn coupled with a nonlinear, non-gradient-based optimization method and applied to the design of isolated supersonic inlets/nacelle geometries. This paper describes the analysis and optimization method. Sample optimization problems are identified and the results of applying the method presented and discussed. Nomenclature A fan = fan face area A e = area of the exit plane of a propulsion system C dv = viscous drag coefficient c f = skin friction coefficient  r = inlet pressure recovery k = form factor ˙ m = mass flow rate ˙ m a = required airflow rate (from propulsion analysis) ˙ m a = predicted airflow rate (from aerodynamics analysis) ˙ m f = fuel-burn rate p e = exit plane pressure in a propulsion system p  = freestream pressure p t = total pressure p t = freestream total pressure S ref = aircraft reference area S wet = wetted surface area T = required thrust u e = exit plane velocity in a propulsion system u  = freestream velocity

Thrust reverser utilizing integrated structural bypass duct

Abstract: A thrust reverser having an engine cowl, a nacelle, a blocker door, a nacelle door and a cascade vane. The engine cowl has a hollow body that shrouds a jet engine and which includes a cowl opening. The nacelle surrounds the engine cowl and includes a nacelle opening that is positioned outwardly of the cowl opening. The blocker door is associated with the engine cowl and movable between a first position, wherein the blocker door closes the cowl opening, and a second position, wherein the blocker door is disposed in the propulsive air flow and substantially clears the cowl opening. The nacelle door is associated with the nacelle and movable between a forward position, which substantially closes the nacelle opening, and a rearward position, which substantially clears the nacelle opening. The cascade vane is disposed between the engine cowl and the nacelle and positioned between the cowl and nacelle openings.

Foreign object damage tolerant nacelle anti-icing system

Abstract: A nacelle for housing a gas turbine engine is disclosed The nacelle comprises an inlet lip defining a leading edge of the nacelle and a conduit located within the inlet lip, the conduit having a fluid circulating therein The fluid provides a heat source An energy attenuating member is located within the inlet lip between the leading edge and the conduit The energy attenuating member provides protection to the conduit from foreign object damage and is thermally conductive such that heat transfer communication between the conduit and the leading edge is provided

Cooling system for hot parts of an aircraft engine, and aircraft engine equipped with such a cooling system

Abstract: The cooling system (30) for an aircraft engine (10) comprises a channel (32) that draws off cold air in the secondary air flow (200), and a heat exchanger (34) located in the channel (32) and in which hot air circulates. The channel (32) comprises:- a supply pipe (322) and an evacuation pipe (326) fixed to the nacelle (324), - an intermediate box (324) located between the supply pipe (322) and the evacuation pipe (326), fixed to the engine (10), and in which the heat exchanger (34) is placed. Application to cooling of hot parts (22) in an aircraft engine (10).

Convertible aircraft provided with two tilt fans on either side of the fuselage, and with a non-tilting fan inserted in the fuselage

Abstract: The present invention relates to a convertible aircraft provided with first and second tilt fans disposed on either side of the fuselage a little forward of the center of gravity of the convertible aircraft. In addition, the convertible aircraft includes, in remarkable manner, a non-tilting fan that is permanently in a vertical position and that is contained inside the fuselage.

Parametric Modeling of Aircraft Families for Load Calculation Support

Abstract: In the present work, a knowledge-based parametric Multi Model Generator (MMG) for reproducing a conventional aircraft family is presented. The intent is to introduce the MMG into a dedicated Design and Engineering Engine (DEE) for performing load calculation in the preliminary design phase. For this purpose the MMG has to be capable to supply different models of the same product, i.e. structure, mass and aerodynamic models, to feed a set of analysis tools. The generated models are extracted from a Knowledge Based Engineering (KBE) product tree, which is capable to hold the knowledge of the complete aircraft product. The definition of the aircraft is fully parametric, so that consistent models for the different disciplines can be generated for a large variety of aircraft configurations by variation of a single input file. The present work is mainly focused on the description of the structural model extracted from the MMG. The aircraft is modeled as an assembly of components, which in turn are built up as an assembly of so-called High-Level Primitives. The wing trunk primitive, presented in previous works, is used for reproducing all the lifting components; the fuselage trunk is presented as a new primitive used to reproduce the fuselage and engine nacelles. A flow diagram for the complete DEE is presented to show the position of the MMG in the load calculation process.

Wind power generation device

Abstract: PROBLEM TO BE SOLVED: To provide a wind power generation device capable of improving load resistance capacity and reliability as compared with a conventional device. SOLUTION: The wind power generation device 10 is provided with a blade 11 for receiving wind, a nacelle 12 rotatably supporting the blade 11, a tower 13 rotatably supporting the nacelle 12, a generator 15 generating power by converting rotational motion of the blade 11 to the nacelle 12 to electric power, and a rotation control device 20 controlling rotation of the nacelle 12 to the tower 13. The rotation control device 20 is provided with a motor with a brake driving and rotating the nacelle 12 to the tower 13 and controlling rotation of the nacelle 12 to the tower 13. Brake force of the motor with the brake braking rotation of the nacelle 12 to the tower 13 is smaller than rotating force to rotate the nacelle 12 to the tower 13 by wind of a predetermined speed when speed of wind which the blade 1 receives is a predetermined speed or more. COPYRIGHT: (C)2006,JPO&NCIPI

The Joint Rolls-Royce/Boeing Quiet Technology Demonstrator Programme

Abstract: *† ‡ § ** †† This paper describes a successful programme undertaken by Boeing and Rolls-Royce to demonstrate nacelle based noise reduction technologies including advanced nozzle and enhanced inlet nacelle designs. The programme, completed between 2001 and 2002, demonstrated jet noise reductions in flight, of up to 4dB, for hot and cold nozzle serrations, confirming pre-test expectations based on model test work. Forward propagating fan noise reductions of up to 13dB were achieved at blade passing frequency (BPF) with a new Boeing developed acoustically enhanced inlet (Amax). Acoustic pressure transducer arrays located forward and downstream of the fan, during static engine testing, helped identify that the Amax inlet fan noise reductions were largely attributable to minimising scattering of acoustic modes and the axial extent of the new liner. Results from this programme highlight the benefit of engine and airframe manufacturers working together to reduce overall aircraft noise levels, and have demonstrated the readiness of the tested technologies for production incorporation.

Investigation of Acoustical Shielding by a Wedge-Shaped Airframe

Abstract: Experiments on a scale model of an advanced unconventional subsonic transport concept, the Blended Wing Body (BWB), have demonstrated significant shielding of inlet-radiated noise. A computational model of the shielding mechanism has been developed using a combination of boundary integral equation method (BIEM) and equivalent source method (ESM). The computation models the incident sound from a point source in a nacelle and determines the scattered sound field. In this way the sound fields with and without the airfoil can be estimated for comparison to experiment. An experimental test bed using a simplified wedge-shape airfoil and a broadband point noise source in a simulated nacelle has been developed for the purposes of verifying the analytical model and also to study the effect of engine nacelle placement on shielding. The experimental study is conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. The analytic and experimental results are compared at 6300 and 8000 Hz. These frequencies correspond to approximately 150 Hz on the full scale aircraft. Comparison between the experimental and analytic results is quite good, not only for the noise scattering by the airframe, but also for the total sound pressure in the far field. Many of the details of the sound field that the analytic model predicts are seen or indicated in the experiment, within the spatial resolution limitations of the experiment. Changing nacelle location produces comparable changes in noise shielding contours evaluated analytically and experimentally. Future work in the project will be enhancement of the analytic model to extend the analysis to higher frequencies corresponding to the blade passage frequency of the high bypass ratio ducted fan engines that are expected to power the BWB.

Measurement Methods and Devices Applied to A380 Nacelle Double Degree-Of-Freedom Acoustic Liner Development

Abstract: The work presented here has been carried out as part of the Airbus A380 nacelle development program. A Double-Degree-Of-Freedom acoustic liner has been developed by Hurel-Hispano, with the aid of suitably adapted measurement devices and methods that allowed proper control and understanding of the relationship that exist between geometric and acoustic properties of the developed liner. In addition, extensive work has been performed so as to identify the relevant parameters of the manufacturing process.

Power generating wind turbine

Abstract: Provided is a power generating wind turbine in which parts and compoments installed in or on a nacelle are made smaller and lighter and maintenance is facilitated. A main shaft 11, a gear-box speeding up rotation of the main shaft 11 and a generator 13 driven by output of the gear-box 11 are provided on a nacelle bed plate 6. The main shaft 11 is connected to an input shaft 12a end of the gear-box 12 via a double-row tapered roller bearing 16. The main shaft 11 is supported to be fitted to a wall portion W1 of the nacelle bed plate 6 with the double-row tapered roller bearing 16 being interposed therebetween. The main shaft 11 is formed in an annular shape having its outer diameter D1 made larger than its axial directional length L1.

Effects of Bifurcations on Aft-Fan Engine Nacelle Noise

Abstract: Aft-fan engine nacelle noise is a significant factor in the increasingly important issue of aircraft community noise. The ability to predict such noise within complex duct geometries is a valuable tool in studying possible noise attenuation methods. A recent example of code development for such predictions is the ducted fan noise propagation and radiation code CDUCT-LaRC. This work focuses on predicting the effects of geometry changes (i.e. bifurcations, pylons) on aft fan noise propagation. Beginning with simplified geometries, calculations show that bifurcations lead to scattering of acoustic energy into higher order modes. In addition, when circumferential mode number and the number of bifurcations are properly commensurate, bifurcations increase the relative importance of the plane wave mode near the exhaust plane of the bypass duct. This is particularly evident when the bypass duct surfaces include acoustic treatment. Calculations involving more complex geometries further illustrate that bifurcations and pylons clearly affect modal content, in both propagation and radiation calculations. Additionally, results show that consideration of acoustic radiation results may provide further insight into acoustic treatment effectiveness for situations in which modal decomposition may not be straightforward. The ability of CDUCT-LaRC to handle complex (non-axisymmetric) multi-block geometries, as well as axially and circumferentially segmented liners, allows investigation into the effects of geometric elements (bifurcations, pylons).