Engine Nacelle Research Articles

Numerical Study on the Effect of Natural Gas on Aircraft Turbofan Engine Propulsion

The world has been concerned and worried about the depletion of the liquid oil fuel, besides new environmental rules are to be followed to reduce pollution hazards and global warming. The utilization of natural gas (as a near term fuel) and hydrogen (as long-term fuel) are receiving great attention, because they have less pollution effects. Since the aviation has a great deal in environmental pollution effects due to the cruise flight in the upper troposphere (supersonic aircraft) or in the lower stratosphere (subsonic aircraft) where most of the ozone concentrate, which helps in protecting the earth form ultra violet radiation. Therefore, the use of alternate fuel has a great attention in aviation. In the present study, the thrust specific fuel consumption and specific thrust for the aircraft during aircraft flight profile are predicted, when using aviation fuel and natural gas. The P&W JT9D –7R-turbofan jet engine is taken as a base line engine propelling the Boeing 747-200 aircraft as a base line aircraft with four engine nacelles mounted on wings. The model engine fuel-air cycle representation is carried out for design point calculations based on sea level static conditions and variable specific heats along engine components. The predicted engine performance results compared very well with the reported values by the manufacture. Predictions carried out using aviation fuel and natural gas show an increase in the specific thrust by 3% and decrease in the thrust specific fuel consumption by 14% and fuel to air ratio by 11%, when using natural gas.

Analysis of the propellers-airframe interaction of the light transport aircraft

In the design of multi-engine aircraft, one of the important issues is the interaction between the propellers and airframe configuration components, especially in take-off and go-around procedure modes. Modern propeller-driven aircraft concepts in the pulling configuration are characterized by a high disk loading and an increased number of propeller blades used to increase cruising speed and reduce excessive noise. The first problem arising due to high disk loading is the direct impact of forces by operating propellers (thrust, normal force) on fixed-wing stability, especially at angles of attack different from a zero value. The second one involves a high-energy level of the propeller slipstream, having a significant indirect impact on the aircraft’s aerodynamics, stability and controllability. This impact is primarily associated with the interaction of propellers slipstream with other aircraft’s configuration elements. The complexity of taking into account the slipstream-wing interaction and other airframe components stipulated the application of experimental methods to study the problems of propellers – airframe interaction while designing propeller-driven aircraft configurations. This article presents an analysis of the experimental studies results of the operating propellers- airframe interaction for a light twin-engine transport aircraft. The aerodynamic aircraft’s configuration is executed using the conventional pattern of a high-wing and the carrier-on deck type empennage. The high-lift wing device is a fixed-vane doubleslotted flap. The wind-tunnel tests of the model in the cruising, takeoff and landing configurations were carried out in TsAGI lowspeed wind-tunnel T-102. Measurement of forces and moments, acting on the model, was performed by means of an external sixcomponent wind-tunnel balance. Measurement of forces and moments, acting on the propeller, was conducted using strain gauge weighers installed inside the engine nacelles of power plant simulators. The simultaneous combined use of external and internal balances allowed researchers to determine the direct and indirect contribution of operating propellers to the model longitudinal aerodynamic characteristics under variation of loading factor B ranging from 0 to 2.

Maximisation of installed net resulting force through multi-level optimisation of an ultra-high bypass ratio engine nacelle

Engine/wing interference in podded installations can introduce relevant changes to their isolated behaviour, especially for large turbofans with an ultra-high bypass ratio. With such coupled flow field, the interaction is best described by the integrated force acting on the whole aircraft. Rather than focusing on drag or thrust metrics separately, in this paper we maximise the net resulting force on the NASA CRM wing body with underwing-installed turbofans through a multi-level optimisation procedure of the engine nacelle. The first stage involves two-dimensional axisymmetric geometries for cowl and exhaust ducts shapes optimisation. The solutions are transformed into three-dimensional nacelles with pylon, featuring a non-axisymmetric inlet. The impact of the pylon on the exhaust flow is evaluated through a design of experiment and a successive surrogate-based optimisation. In the last step, nacelle/wing offset, intake angles, and engine orientation are assessed in the installed configuration at fixed lift. The final optimised design is compared with a baseline geometry initially defined, showing a significant improvement of the net vehicle thrust equal to 3% of the reference force. The result highlights a counteracting effect of individual force components, in a way that the installed resulting force can only be improved when considering them globally.

Study of the Aerodynamic Characteristics on the ‎Computed Flowfield During Thrust Reversers Operation

With the increasing of the bypass ratio of modern aero-engines, the problem of wing-engine interference is more prominent, especially for the layout design of engine nacelle. The reverse thrust cascade is widely used in turbofan engines with high bypass ratio. In order to meet the requirements of the integrated analysis of airframe, wing, engine nacelle and hanger, the aerodynamic characteristics of aircraft/engine integration configuration with reverse cascade is numerically studied via CFD (Computational Fluid Dynamics) method. The streamline distribution, iso-surface of total temperature, vorticity distribution and total reverse thrust efficiency on different engine nacelle layouts are compared and analyzed in details. The results show that the lift coefficient of the wing decreases by 21.2% and 45.02% respectively as the engine moves forwards horizontally by 11%L and 21.2%L. The lift coefficient of the wing decreases by 2.4% and 4.82% respectively as the engine moves subsidence by -3.5%L and 3.5%L. The influential region of the reverser airflow in the radial and circumferential direction without airframe interference is significantly larger than that in the case with aircraft/engine integration. The reverser flow is susceptible to be interfered by the adjacent fuselage and wing sections, and the development of reverse thrust flow is significantly limited. Compared to the baseline nacelle location, the reverse thrust performs badly as engine nacelle moves backward and lateral horizontally. The total reverse thrust efficiency decreases gradually as the engine nacelle moves forward horizontally.

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform description

In the context of aircraft noise reduction in varied applications where a cold or hot shear grazing flow is present (i.e., engine nacelle, combustion chamber, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints limit the efficiency of conventional liner technology. Therefore, liner design must take into account the dimensional and phenomenological characteristics of constituent materials, assembly specifications and industrial requirements involving multiphysical phenomena. To perform the single/multi-objective optimization of complex meta-surface liner candidates, a software platform coined OPAL (OPtimisation of Acoustic Liners) was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial elementary acoustic layers along a given duct. Then, the physical properties of this liner can be optimized, relatively to weighted objectives, for a given flow and frequency range: impedance target, maximum absorption coefficient or transmission loss with a total sample size and weight... The presentation will focus on the different elementary bricks and assembly of a problem (from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin simulations of the Linearized Euler Equations).

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform applications

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

Empirical estimation of engine-integration noise for high bypass ra-tio turbofan engines

To investigate the impact of installation on jet noise from modern high-bypass-ratio turbofan engines, a model-scale noise experiment with a jet propulsion system and a fuselage model in scale was conducted in the anechoic wind tunnel of ONERA, CEPRA 19. Two area ratios (an area of the secondary nozzle over an area of the primary nozzle), 5 and 7, and various airframe configurations such as wing positions relative to the tip of the engine nacelle and flap angles, were considered. Based on the analysis of experimental data, an empirical model for the prediction of engine installation noise was proposed. The model comprises two components: one is the interaction be-tween the jet and the pressure side of the wing, and the other is the interaction between the jet and the flap tip. The interaction between the jet and the pressure side of the wing contributes to the noise at the low frequencies (≤ 1.5 kHz), and the interaction between the jet and the flap tip con-tributes to the noise at the high frequencies. The proposed model showed a good agreement with the experimental data.

Modeling of Transonic Transitional Three-Dimensional Flows for Aerodynamic Applications

The paper describes a technology designed for computing three-dimensional transonic laminar–turbulent flows at various aerodynamic configurations with the use of the general-purpose computational fluid dynamics code ANSYS Fluent and an integrated special module of computing the laminar–turbulent transition position created on the basis of the autonomous software package LOTRAN 3, developed previously by the authors. Within the framework of this technology, computations with a prolate spheroid and engine nacelle are performed for different Mach numbers ( Reynolds numbers ), and angles of attack ( to ). New results are obtained on the position of the laminar–turbulent transition in boundary layers in transonic flow regimes, and the problem of the dominating transition mechanism is considered. The results obtained in the present study are demonstrated to be in good agreement with experimental data on the position of the laminar–turbulent transition available in the literature.

An acoustic liner design methodology based on a statistical source model

The attenuation of fan tones remains an important aspect of fan noise reduction for high bypass ratio turbofan engines. However, as fan design considerations have evolved, the simultaneous reduction of broadband fan noise levels has gained interest. Advanced manufacturing techniques have also opened new possibilities for the practical implementation of broadband liner concepts. To effectively address these elements, practical acoustic liner design methodologies must provide the capability to efficiently predict the acoustic benefits of novel liner configurations. This paper describes such a methodology to design and evaluate multiple candidate liner configurations using realistic, three dimensional geometries for which minimal source information is available. The development of the design methodology has been guided by a series of studies culminating in the design and flight test of a low drag, broadband inlet liner. The excellent component and system noise benefits obtained in this test demonstrate the effectiveness of the broadband liner design process. They also illustrate the value of the approach in concurrently evaluating multiple liner designs and their application to various locations within the aircraft engine nacelle. Thus, the design methodology may be utilized with increased confidence to investigate novel liner configurations in future design studies.

Flow simulation of a supersonic airplane with installed engine nacelle

Flow fields around a supersonic aircraft with installed engine nacelles are simulated to study engine installation effects on the aerodynamic performance and ground sonic boom signature of the aircraft. The engine nacelle is a dual-stream nacelle composed of a relaxed isentropic compression supersonic inlet and an annular bypass duct around the core engine. Two different bypass duct shapes are considered here; one is a full three-dimensional configuration consisting of struts and a gearbox fairing, and the other is a simplified axisymmetric duct with equivalent area distribution to the original full three-dimensional configuration. The full 3-D and axisymmetric ducts are found to produce almost identical external shock patterns as expected, which confirms our previous vane shape design results. Representative airframe-propulsion interference cases are suggested, and configurations with different engine locations are simulated and identified according to the interference cases.

Investigation of the Nacelle/Pylon Vortex System on the High-Lift Common Research Model

A 10%-scale high-lift version of the Common Research Model (CRM-HL) was tested in the NASA Langley Research Center’s 14 by 22 ft subsonic tunnel. The focus of the wind-tunnel tests was to investigate the vortices generated at the nacelle/pylon region and their effect on the aerodynamic performance. The wind-tunnel measurements included the acquisition of force and moment data, steady pressure data, as well as surface flow visualization using minitufts. For some select cases, numerical simulations were performed to aid in understanding the wind-tunnel data. Wind-tunnel tests, with and without the nacelle/pylon, indicated a lift degradation of the conventional CRM-HL at high angles of attack. The surface flow visualization with fluorescent minitufts revealed that the lift degradation is due to flow separation caused by the nacelle/pylon vortex system on the inboard wing. The consequent flow separation was successfully mitigated using a nacelle chine installed on the inboard side of the engine nacelle.

CFD simulation of engine nacelle cooling on pusher configuration aircraft

PurposeThe purpose of this paper is to simulate with in-depth reconstruction of existing geometry a process of cooling of the aircraft engine in pusher configuration, which is more problematic than usually used, tractor configuration. Moreover, a complex thermal and fluid flow analysis is necessary to verify that an adequate cooling is ensured and that temperatures in the engine nacelle are maintained within the operating limits.Design/methodology/approachMethodology used in this research is based on computational fluid dynamics tools to model adequately the internal and the external flow, to find the state of cooling system and research the results of baffles modification inside the engine cover. Additionally, two types of the cover with different sizes of inlets and outlets are tested.FindingsThe results showed the influence of baffles modifications and changes in inlets and outlet sizes on the mass flow rate and temperature distributions inside the engine nacelle. The best configuration of air inlets and outlets was determined.Practical implicationsThe method used in the research is the safest method in testing of such cases, provided the proper approach in modeling is taken. The collaboration of internal and external flow is crucial and should not be replaced with assumed flow rate through inlet and outlet area. The obtained results will help in future studies on cooling systems of engines in pusher configuration.Originality/valueThe work presents original results obtained by the authors during a complex fluid flow and heat transmission analysis and is a part of the design project of the OSA patrol aircraft.

Adaptive-surrogate-based robust optimization of transonic natural laminar flow nacelle

Natural Laminar Flow (NLF) technology is very effective for reducing the skin friction drag of aircraft engine nacelle, but the aerodynamic performance of NLF nacelle is highly sensitive to uncertain working conditions. Therefore, it’s imperative to incorporate uncertainties into the design of NLF nacelle. In this study, for a robust optimization of NLF nacelle and for improving its efficiency, an adaptive-surrogate-based robust optimization strategy is established, which is an iterative optimization process where the surrogate model is updated to obtain the real Pareto front of multi-objective optimization problem. A case study is carried out to validate its feasibility and effectiveness. The results show that the optimization increases the favorable pressure gradient region and the volume ratio of the nacelle by increasing its lip radius and reducing its maximum diameter. And the aerodynamic robustness of the NLF nacelle is mainly determined by the lip radius, maximum diameter of nacelle and location of the maximum diameter. Compared to the initial nacelle, the optimized nacelle maintains a wide range of low drag and high laminar flow ratio in the disturbance space, which extends the average laminar flow region to 21.6% and facilitates a decrease of 1.98 counts in the average drag coefficient.

Properties of Polymer Composite Materials Based on Alternative High-Strength Carbon Tow Fillers and Epoxide Polymer Matrices

Test results are presented for the main properties of unidirectional prepregs and structural carbon plastics based on polymeric epoxide matrices of Russian manufacturing and alternative high-strength carbon tow fillers designed for fabrication of domestic and secondary PD-14 engine nacelle parts, modifications of promising MC-21 aircraft, etc.

Study of an experimental prototype simulating a mechanical vibration damper with rotational friction pairs

This paper presents the results of a computational and experimental study of an experimental prototype simulating an aircraft engine vibration damper installed in an engine nacelle on the wing pylon of a mainline aircraft.

Effects of fuel pool on temperature profiles of fire in one engine nacelle

The pool influences greatly on its fire diffusion behaviours in enclosed space. The effect of the fuel pool on fire temperature in engine nacelle was investigated. We established nacelle physical m...

Study on a twin-fuselage transport airplane model in a low speed wind tunnel

This paper presents the results of experimental studies of the twin-fuselage transport airplane model at the cruising configuration in the T-102 TsAGI low-speed wind tunnel. The researched twin-fuselage transport airplane is a tri-engine transport aircraft intended for transportation of cargo weighted up to 40 tons at a distance up to 3000 km with speed 700-740 km/h. The aerodynamic configuration has the two fuselages distributed under high-wing, and a “TT” – shaped tail. The research purpose was the determination of the aerodynamic characteristics of the twin-fuselage transport airplane model without engine nacelles and assessment of the twin-fuselage layout impact on control surfaces efficiency. The effect of installing an external cryogenic fuel tank under the wing between the fuselages of the model was considered too.

Effects of fuel pool on temperature profiles of fire in one engine nacelle

Effects of fuel pool on temperature profiles of fire in one engine nacelle

Initial analysis of the aerodynamic characteristics of the rotorcraft model

The article presents an aerodynamic analysis of the aircraft models. The process of constructing the physical model began with the development of geometry. Preliminary design was made using SolidWorks program, giving the desired shape with as many details as the method allowed. It had to be made precisely, because later it was to be printed on a 3D printer. In this phase of the project a special hole was also prepared on the model side for mounting in the wind tunnel. The work presents to compare aerodynamic parameters of three models. The models were presented and printed made of thermoplastic material used with a 3D printer. Measurements depend on the determined longitudinal and vertical axial force depending on the angle of attack at the same speed for all objects. The tests were carried out in two types of tunnels: structure 1 in a closed tunnel, structure 2 and 3 in an open tunnel at the Lublin University of Technology. Models 2 and 3 are very close to each other, the only significant difference is the installation of 3 short wings in the place of engine nacelles. The analysis allows you to check whether a given modification has a positive effect on its characteristics.

Multi-physics simulation of in-flight ice shedding

In-flight ice accretion may possibly jeopardise the safety of fixed-and rotary-wing aircraft. Icing can possibly occur if supercooled water droplets in clouds impinge on the aircraft surfaces and freeze upon impact. A major issue related to ice accretion is the possibility of ice shedding from the main body and impacting other parts of the aircraft or being ingested by the engines. A multi-physics framework is presented to simulate ice accretion and shedding from wings and engine nacelles due to aerodynamic forces. The aerodynamics is computed using the open-source tool-kit SU2. Cloud droplet trajectories are computed using the arbitrary-precision Lagrangian in-house solver PoliDrop. Then, the in-house ice accretion tool-kit PoliMIce is used to determine the ice layer. A FEM structural analysis is performed on the accreted ice shape by means of the open-source code MoFEM. Internal stresses within the ice geometry due to aerodynamic forces are computed. The possibility of the occurrence of cracks in the ice layer is assessed and its propagation is determined numerically. Two-dimensional ice accretion simulations are performed to check the validity of the present approach and compare fairly well with available results.