Engine Cowl Research Articles

Detection and Analysis of Aircraft Composite Material Structures Using UAV

Pre-flight inspection and maintenance are essential prerequisites for aviation safety. This study focused on developing a real-time monitoring system designed to assess the condition of composite material structures on the exterior of aircraft. Implementing such a system can reduce operational costs, enhance flight safety, and increase aircraft availability. This study aims to detect defects in aircraft fuselages manufactured from composite materials by applying image visual recognition technology. This study integrated a drone and an infrared camera for real-time image transmission to ground stations. MATLAB image analysis software (MATLAB 2020b) was used to analyze infrared (IR) images and detect structural defects in the aircraft’s appearance. This methodology was based on the inspection of damaged engine cowlings. The developed approach compares composite material conditions with known defects before and after repair, considering mechanical performance, defect size, and strength. Simultaneously, tests were conducted on various composite material panels with unknown defects, yielding favorable results. This study underscores an integrated system offering rapid detection, real-time feedback, and analysis, effectively reducing time, and potential hazards associated with high-altitude operations. Furthermore, it addresses blind spots in aircraft inspections, contributing to effective flight safety maintenance.

Development and Investigation of a Fire-Resistant Aluminum–Glass Fiber Reinforced Plastic for a Helicopter Engine Cowl

Development and Investigation of a Fire-Resistant Aluminum–Glass Fiber Reinforced Plastic for a Helicopter Engine Cowl

Evaluation of thermal management scheme of engine cowl based on rotating heat pipe

During the flight in icing conditions, ice may accrete on the aircraft engine cowl, and once it falls off, it will seriously affect the engine performance and even the flight safety of the aircraft. The rotating heat pipe performances good heat transfer characteristics in high-speed rotating conditions, and can be coupled with the high-speed rotating main shaft of the engine to implement the reuse of the engine waste heat for anti-icing of engine cowl. A certain type of engine cowl was selected in the paper, and the anti-icing area and heat load of the three-dimensional cowl were determined using CFD method. On this basis, literature researches were carried out, and feasibility of rotating heat pipe applicated on engine cowl was verified by the qualitative analysis of the rotating heat pipe’s thermal characteristics. Furtherly, based on the anti-icing requirements of the cowl, a rotating heat pipe was designed. Through the thermal experiment, the results show that the rotating heat pipe performs good thermal start-up and stability within 200W, and can meet the anti-icing demands of the engine cowl. From the qualitative and quantitative analysis, it can be convinced that the application of rotating heat pipe on thermal management of the engine cowl is feasible.

On vibrational-based numerical simulation of a jet engine cowl shell-like structure

The present research proposes an applicable and impressive analytical model of Aircraft Engine Cowl (AEC) due to auspicate its frequency parameter. For the first time, the authors configured the structure of AEC by joining two well-known shapes of shell, including elliptical and conical. This procedure is implemented by obtaining the governing motion organization of differential equations affiliated with the Joined Elliptical-Conical Shells (JECS) in line with first-order shear deformation theory (FSDT) and General Shell Formulation (GSF). Moreover, Functionally Graded Materials (FGMs) with various spreading forms along the structure’s thickness are used to enhance the dynamic performance of AEC. It is worth mentioning that the recognized Rule of Mixture (RM) is engaged for achieving the equivalent mechanical characteristics of FGM. Finally, a well-known semi-analytical Generalized Differential Quadrature (GDQ) procedure is hired to extract the resulting system of motion equations to access the free vibration responses of AEC with diverse Boundary Conditions (BCs). It is worth mentioning that an applicable and interesting numerical model is done to inspect the remnants of geometric and material features on the oscillation demeanor of AEC structures. It will be verified that the projected procedure can be helpful for AEC’s vibration analysis and extendable for other types of studies to predict the AEC structure's static and dynamic treatment.

Anti-Icing Engine Damage Analysis Boeing 737 - 800 Ng With Fault Tree Analysis Method

An Anti-icing system is a system that aims to prevent the formation of ice when the plane is in the air. The formation of ice in aircraft is of great concern because an airplane flight will pass through the atmosphere, which will experience the formation of the ice at a certain altitude. The formation of such ice will cause a hazard to the aircraft. So that the ice protection system, namely the anti-icing system, is very concerned so that it is always in a serviceable condition. In this study, direct observation and fault tree analysis were used to determine the cause of failure of the Boeing 737-800 NG anti-ice system engine and anti-icing cowl inlet. The results of the analysis using the fault tree analysis method obtained essential events, namely: actuator fails, electrical connector disconnected, Control Selenoid Trouble, Regulator Trouble, Sense Line Connector Trouble, Engine Fault, Engine Control Trouble, Engine Duct Trouble, Panel Buttom Problem, EICAS Module Problem, No Source Electricity, Negative Electrical Source, Wiring Problem.

Anti-Icing Engine Damage Analysis Boeing 737 - 800 Ng With Fault Tree Analysis Method

An Anti-icing system is a system that aims to prevent the formation of ice when the plane is in the air. The formation of ice in aircraft is of great concern because an airplane flight will pass through the atmosphere, which will experience the formation of the ice at a certain altitude. The formation of such ice will cause a hazard to the aircraft. So that the ice protection system, namely the anti-icing system, is very concerned so that it is always in a serviceable condition. In this study, direct observation and fault tree analysis were used to determine the cause of failure of the Boeing 737-800 NG anti-ice system engine and anti-icing cowl inlet. The results of the analysis using the fault tree analysis method obtained essential events, namely: actuator fails, electrical connector disconnected, Control Selenoid Trouble, Regulator Trouble, Sense Line Connector Trouble, Engine Fault, Engine Control Trouble, Engine Duct Trouble, Panel Buttom Problem, EICAS Module Problem, No Source Electricity, Negative Electrical Source, Wiring Problem.

Effect of Low Velocity Impact at Pre-Stressed Condition on Curved Glass-Carbon Composites Laminate

A curved composite panel is used in aircraft parts such as wings and engine cowling in order to improve their impact resistance to different types of impact loads. The effect of size reduction in the tensile pre-stress behaviour of low velocity impact on different materials such as glass and glass/carbon hybrid is examined in this paper. The effects of low velocity impact behaviour of two different pre-stressed curved laminates are taken for consideration and examined under impact loading. The objective of this research is to improve the efficiency of curved laminate by changing the hybrid composition such as glass/carbon with varied stacking sequence. The present studies using hybrid composition have shown that the load carrying capacity is higher in convex laminates while the damaged surface area in convex laminates is very less.

Complex stress-strain behaviour of a cylindrical shell with a dynamically breaking internal elastic base

During the operation of a solid-propellant rocket engine, the combustion products of a powder charge create increased pressure in the combustion chamber. Besides, the combustion of gunpowder is accompanied by a large release of heat, which, despite the thermal insulation, causes the appearance of deformations in the engine cowling. This leads to the need to investigate the durability of the shell under the influence of internal pressure and temperature fields. The aim of the paper is to determine the complex dynamic deformed state and vibrations of the engine cowling under the action of force and temperature loads. The problem of a complex axisymmetric stress-strain state and vibrations of a thin cylindrical shell with a dynamically breaking internal elastic foundation, obeying Winkler's hypothesis, is approximately solved. The shell is under the action of internal pressure and temperature fields on a part of its length free from an elastic base. The resolving equation of the problem of the shell deflection is solved by the Bubnov-Galerkin method, reducing the problem to a system of linear algebraic equations. The examples are considered, in which the basic frequencies of natural vibrations of the structure are determined depending on the conditions of shell fastening. Parametric studies are carried out.

Failure Analysis of Cooling Duct of Top Engine Cowl Panel of Fighter Aircraft

Present work describes the failure analysis of cooling duct of a fighter aircraft. The analyzed chemical composition of cooling duct indicates that it is manufactured from Al-based alloy (AA 3003 or its equivalent). Microstructure of cooling duct displays the presence of two phases namely, matrix and insoluble particles. The hardness values at different locations within damaged area of cooling duct reflect nearly same and consistent. The fracture surface of the cooling duct exhibits transgranular features and cracks with little branching. The analyzed hydrogen content in cooling duct is significantly higher (∼ 12 ppm) than the specified one (< 1 ppm). However, the alloy used to fabricate cooling duct is not susceptible to typical hydrogen embrittlement. This shows hydrogen pick up during operation. The presence of cracks with branching does reflect features of hydrogen embrittlement. In addition, striations indicative of fatigue features are also observed. It thus appears that the cooling duct has failed due to pick up of large amount of hydrogen as well as vibrational fatigue.

Investigating the effects of fluid intrusion on Nomex® honeycomb sandwich structures with carbon fiber facesheets

Abstract Honeycomb sandwich construction is commonly used in aircraft structures to make parts with a superior strength to weight ratio. Nomex® honeycomb core is used extensively for flooring, skin panels, fairings, engine cowlings, and flight controls. Honeycomb sandwich structures are prone to fluid ingression due to their thin facesheets which get damaged easily by impact or erosion. The purpose of this research was to determine how the mechanical properties of honeycomb sandwich structures were affected if the structure was saturated by a fluid such as water, fuel, hydraulic fluid, or engine oil. The authors focused on the lasting effect on the sandwich structure when aircraft fluids ingress into the structure. The test panels were made of carbon fiber prepreg, and they were bonded to a 12.7 mm thick Nomex® honeycomb core material. The specimens were soaked in water, fuel, hydraulic fluid, or engine oil for 45 days. After the soak period, the specimens were removed from the fluids and left to drain for 30 days. The specimens including the control group were tested with a four-point loading test and impact test in accordance with ASTM standards.

Mechanical Properties of Polymer Composite Materials Based on Russian High-Strength Carbon Fillers and a New Generation of Polymer Matrices

Test results for the main properties of prepregs and carbon plastics based on a new generation of polymeric binders, i.e., highly flexible epoxide binder VSE-1212, and Russian woven carbon reinforcing fillers designed to fabricate PD-14 engine cowl flaps, pylon shrouds, and reverse device fittings, and also for primary and secondary constructions for modifications of promising MC-21 airplanes, etc.

Improve Heat Resistance of Composite Engine Cowlings Using Ceramic Coating Materials, Experimental Design and Testing

Improve Heat Resistance of Composite Engine Cowlings Using Ceramic Coating Materials, Experimental Design and Testing

Full-Scale Turbofan Demonstration of a Deployable Engine Air-Brake for Drag Management Applications1

This paper presents the design and full-scale ground-test demonstration of an engine air-brake (EAB) nozzle that uses a deployable swirl vane mechanism to switch the operation of a turbofan's exhaust stream from thrust generation to drag generation during the approach and/or descent phase of flight. The EAB generates a swirling outflow from the turbofan exhaust nozzle, allowing an aircraft to generate equivalent drag in the form of thrust reduction at a fixed fan rotor speed. The drag generated by the swirling exhaust flow is sustained by the strong radial pressure gradient created by the EAB swirl vanes. Such drag-on-demand is an enabler to operational benefits such as slower, steeper, and/or aeroacoustically cleaner flight on approach, addressing the aviation community's need for active and passive control of aeroacoustic noise sources and access to confined airports. Using NASA's technology readiness level (TRL) definitions, the EAB technology has been matured to a level of six, i.e., a fully functional prototype. The TRL-maturation effort involved design, fabrication, assembly, and ground-testing of the EAB's deployable mechanism on a full-scale, mixed-exhaust, medium-bypass-ratio business jet engine (Williams International FJ44-4A) operating at the upper end of typical approach throttle settings. The final prototype design satisfied a set of critical technology demonstration requirements that included (1) aerodynamic equivalent drag production equal to 15% of nominal thrust in a high-powered approach throttle setting (called dirty approach), (2) excess nozzle flow capacity and fuel burn reduction in the fully deployed configuration, (3) acceptable engine operability during dynamic deployment and stowing, (4) deployment time of 3–5 s, (5) stowing time under 0.5 s, and (6) packaging of the mechanism within a notional engine cowl. For a typical twin-jet aircraft application, a constant-speed, steep approach analysis suggests that the EAB drag could be used without additional external airframe drag to increase the conventional glideslope from 3 deg to 4.3 deg, with about 3 dB noise reduction at a fixed observer location.

Impact Behaviour of Soft Body Projectiles

Bird strike analysis is a common type of analysis done during the design and analysis of primary structures such as engine cowlings or fuselage panels. These simulations are done in order to predict whether various designs will pass the necessary certification tests. Composite materials are increasingly being used in aerospace industry and bird strike is a major threat which may lead to serious structural damage of those materials. Such phenomenon may arise from numerous impact scenarios. The focus of current study is on the finite element modeling for composite structures and simulation of high velocity impact loads from soft body projectiles with an explicit dynamics code AUTODYN. This paper investigates the methodology which can be utilized to certify an aircraft for bird strike resistance using computational technique by first demonstrating the accuracy of the method for bird impact on rigid target modeling and then applies the developed model to a more complex problem. The model developed for bird strike threat assessment incorporates parameters of bird number (bird density), bird body mass, equation of state (EOS) and bird path during impact.

Influences of weaving architectures on the impact resistance of multi-layer fabrics

Fabrics constructed from different weaving architectures such as plain, basket, twill and satin provide varying flexibility and durability when applied on surfaces of complex structures for protective applications. They also affect the manufacturing processes and mechanical properties of both fabrics and composite structures in various applications such as soft armours, helmets, aircraft engine cowlings or automobile monocoques. In this work, the influences of weaving architectures on the ballistic resistance and energy absorption of both single and multi-layer Twaron® fabrics are investigated. A mesoscale yarn model is constructed, validated experimentally, and analytical. Finite element fabric models of different fabric structures are then developed and their firmness is quantified using interlacing factors. Numerical models for plain weave are validated against experimental results from single-ply ballistic tests. The evolutions of kinetic, strain, and friction energy components, normalised with areal mass, are presented to demonstrate the better ballistic protection of the plain weave compared with other weaving architectures. Further investigations on multi-ply systems illustrate the energy absorption capacities for different types of woven fabrics and the associated ballistic resistances. The research results indicate that weaving architectures and fabric firmness are less influential on the overall ballistic protection of multi-ply systems compared to the single-ply cases.

Novel inlet–airframe integration methodology for hypersonic waverider vehicles

With the aim of integrating a ramjet or scramjet with an airframe, a novel inlet–airframe integration methodology for the hypersonic waverider vehicle is proposed. For this newly proposed design concept and for the specified flight conditions, not only the forebody of the vehicle but also its engine cowl and wings can ride on the bow shock wave, causing the bow shock wave to remain attached to the leading edge for the entire length of the vehicle. Thus, this integrated vehicle can take full advantage of the waverider׳s high lift-to-drag ratio characteristics and the ideal pre-compression surface for the engine. In this work, a novel inlet–airframe integrated axisymmetric basic flow model that accounts for both external and internal flows is first designed using the method of characteristics and the streamline tracing technique. Subsequently, the design of the inlet–airframe integrated waverider vehicle is generated from the integrated axisymmetric basic flow model using the streamline tracing technique. Then, the design methodologies of both the integrated axisymmetric basic flow model and the integrated waverider vehicle are verified by a computational numerical method. Finally, the viscous effects and performance of both the integrated axisymmetric basic flow model and the integrated waverider vehicle are analysed under the design condition using the numerical computation. The obtained results show that the proposed approach is effective in designing the integrated hypersonic waverider vehicle.

Simplified thermo-fluid model of an engine cowling in a small airplane

Purpose – The purpose of this study is to developed a simplified thermo-fluid model of an engine cowling in a small airplane. An aircraft engine system is composed of different elements operating at various temperatures and in conjunction with the composite nacelle creates a region with high intensity of heat transfer to be covered by the cooling/ventilation systems. Therefore a thermal analysis, accounting for the complex heat transfer modes, is necessary in order to verify that an adequate cooling is ensured and that temperatures of the nacelle are maintained within the operating limits throughout the whole aircraft's flight. Design/methodology/approach – Simplified numerical simulations of conductive, convective and radiative heat transfer in the engine bay of the small airplane I-23 in a tractor arrangement were performed for different air inlet and outlet configurations and for varying conditions existing in air inlets during the flight. The model is based on the control volume approach for heat and ...

Stereoscopic Particle Image Velocimetry-Based Integral Load Determination on an Aircraft Propeller

0.73 and0.78.Measurements are acquiredat several radial locations inphase-locked mode, encompassing the blade length;specificdatapostprocessingisaimedatdeterminingtheaerodynamicforces,namely,thesectionalthrustand torque at each cross section. The evaluation of the pressure field is based on the integration of the Navier–Stokes equations with the experimental velocity fields expressed in a frame moving with the propeller blade. The approach returns the evaluation of the three-dimensional pressure field, in particular over the blade surface, considerably simplifyingthe flowvisualizationandanalysisinraisingpropellerstudies.Thevelocityandpressuredataarefurther integrated by means of a contour approach to yield the propeller thrust and torque, and compared to data directly derived from a multicomponent balance and from the engine power consumption. Nomenclature AS = cross-sectional area of model support, m 2 CP, CD = pressure and drag coefficients c = chord, m cmax = maximum chord, m D, D0 = drag of the propeller and of the model support, N dE, lS = diameter and length of the engine cowling, m dp = propeller diameter, m ds =i nfinitesimal surface element, m 2

NUMERICAL SIMULATIONS OF INVISCID AIRFLOWS IN RAMJET INLETS

The performances of three different ramjet inlets and an entire ramjet are numerically studied in this paper. The fluid is assumed to be inviscid. Inlet 1 is a SCRAMJET inlet and is chosen from the literature. Inlets 2 and 3 are instead designed based on the Oswatitsch principle. Inlets 2 and 3 produce a series of oblique shocks merging at the engine cowl lip followed by a terminating normal shock just downstream of the inlet throat. In ramjet, the combustion is modeled using a non-uniform volumetric heat source distributed in the combustor area. The position of the terminating normal shock in Inlets 2 and 3 is controlled via the inlet’s back pressure. Instead, in ramjet it is bounded by the amount of heat rate added in combustor and the exhaust nozzle throat area. For the numerical simulations, the Roe (1981) and MacCormack (1969) schemes are used. To prevent the spurious numerical oscillations in high resolution computations by Roe scheme the van Albada flux limiter (1982) is used, while in MacCormack scheme artificial viscosity terms are added to damp the oscillations. To double check the accuracy of the computations, the Fluent software package has also been used. Comparisons show very good agreement.

Comparison of Water Vapor Measurements by Airborne Sun Photometer and Diode Laser Hygrometer on the NASA DC-8

Abstract In January–February 2003, the 14-channel NASA Ames airborne tracking sun photometer (AATS) and the NASA Langley/Ames diode laser hygrometer (DLH) were flown on the NASA DC-8 aircraft. The AATS measured column water vapor on the aircraft-to-sun path, while the DLH measured local water vapor in the free stream between the aircraft fuselage and an outboard engine cowling. The AATS and DLH measurements have been compared for two DC-8 vertical profiles by differentiating the AATS column measurement and/or integrating the DLH local measurement over the altitude range of each profile (7.7–10 km and 1.1–12.5 km). These comparisons extend, for the first time, tests of AATS water vapor retrievals to altitudes &amp;gt;∼6 km and column contents &amp;lt;0.1 g cm−2. To the authors’ knowledge, this is the first time suborbital spectroscopic water vapor measurements using the 940-nm band have been tested in conditions so high and dry. Values of layer water vapor (LWV) calculated from the AATS and DLH measurements are highly correlated for each profile. The composite dataset yields r 2 0.998, rms difference 7.7%, and bias (AATS minus DLH) 1.0%. For water vapor densities AATS and DLH had r 2 0.968, rms difference 27.6%, and bias (AATS minus DLH) −4.2%. These results for water vapor density compare favorably with previous comparisons of AATS water vapor to in situ results for altitudes &amp;lt;∼6 km, columns ∼0.1 to 5 g cm−2, and densities ∼0.1 to 17 g m−3.