AEROTECH V: Progressive Aerospace Research

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Authors: Harijono Djojodihardjo, Abdullah Saad Mahmud
Abstract: A set of Mindlin plates bonded together is subjected to loading by impact, which is considered to represent a generic engineering structure and is analyzed through numerical simulation. The objective is to identify optimum configuration in terms of loading, structural dimensions, material properties and composite layup associated with micrometeorites impacts on spacecraft that will not penetrate into its structure. Following the algorithm developed for the problem, the work comprises an in-depth analysis of a generic flat plate structure subjected to impact and numerical simulation. The analyses are based on dynamic response with emphasis on the elastic region. The direct numerical simulation is carried out in parallel for the analysis, synthesis, parametric study and optimization. As simulation case study, the panel structure response to impact loading by a spherical rigid body at certain velocity perpendicular to the panel plate itself and numerical simulation is carried out as appropriate. Simulation results are validated through comparison with analytical work. The entire scheme carried out in this work is a novel comprehensive approach for the structural design of non-penetrated impact on metallic composites. The results show that the use of composites, in particular the bi-metallic composite, is instrumental in tailoring the plate materials to achieve non-penetrating impact.
Authors: Mohd Amirul Abdul Rahman, Azmin Shakrine Mohd Rafie, Renuganth Varatharajoo
Abstract: The effects of aspect ratio and fiber-epoxy weight ratio of coir fibre/epoxy composite wing idealized as flat plate on flutter speed were preliminary studied in this current research to investigate the aeroelastic response on natural fiber composite material. The usage of natural material such as coir fiber reinforced composite might become possible solutions in future since it offers lower weight, cost reduction, and preservation of the environment factor compared to presence structures like conventional glass or carbon fiber as the reinforcement for composites. For this work, the analysis of coir fiber on aeroelastic problem will be preliminary investigated to establish related data to be served, especially in the aerospace research areas. The research began with the existing raw untreated coir fiber, which was in the form of pressed mat and originally in random oriented fiber forms, were set in the composite preparation process by simple hand-lay-up and compression moulding method under the room temperature and also controlled pressure conditions. Specimen with different aspect ratios (5, 6 and 7) with 25% wt fiber reinforcement composite was installed in the wind tunnel for subsonic experimental aeroelastic test. The result shows that the plates with lower aspect ratio have higher flutter speed.
Authors: Qistina Mohd Jamal, D.L. Majid, M.Y. Haris, Noorfaizal Yidris, M.T.H. Sultan

This paper investigates the quasi static compression analysis behavior of a biocomposite radome using nonlinear static modeling. Bio-based fiber is proposed to be used in aircraft radome due to its low dielectric constant. In this instance, kenaf was being utilized as the natural fiber to form a hybrid combination of fiberglass/kenaf epoxy laminates. The quasi static behavior was modeled using MDNastran SOL106 Nonlinear Static. The radome was modeled as a hemispherical shell based on Beechcraft’s radome geometric configuration. The radome is designed as a four-layered laminates with randomly oriented fiberglass and kenaf. The nonlinear compression was performed in the range of 0.01 mm to 0.49 mm with a maximum reaction force of 189 N. The radome was not displaced equally or symmetrically as the translational load applied since the shape of radome is asymmetry and the surface at the top is uneven. The increment of the forces leads to elastic local flattening deformation at the apex of the radome. Its shape influences in determining the displacement and the stress to the radome.

Authors: Sohail Ahmed, M.N. Ahmed
Abstract: This paper explicitly highlights the modal analysis of thin walled multi-cell multi-tapered composite beams in cantilever configurations, using MSC Patran / Nastran finite element package. Initially, the verification of the model was done with the analytical results in order to ensure the model accuracy. All the multi-tapered beams under examination are composed of closed section and three cell configuration. There is a vivid description of all the effects of composite material and stacking sequence on the modal frequencies. It also suggests the ways to shift the natural frequencies of the multi-tapered beams. This paper verifies the effects of different geometrical configurations of beams (tapered angles, lengths and point of variation of tapered angles) on the modal frequencies. This research is also useful in aerospace industry while designing the aircraft wing, which would experience the vibrations due to wind gust and engine cycles.
Authors: Khameel Bayo Mustapha
Abstract: The use of advanced materials in automotive, aerospace and communication technologies has called for re-assessment of classical models of many structural elements. The primary objective of this study relates to the use of a higher-order continuum model for discerning the contribution of certain geometric and material properties on wave propagation behavior of a spinning appendage of an aircraft appendage. The spinning appendage is characterized by a through-thickness functional material gradation and subjected to an axial dead load. The foundation of the present model rests on the trio of the mechanics of functionally graded solid structures, the extended Hamilton’s principle and the thin beam theory. Numerical results from the wave mechanics analyses reveal the noticeable influence of axial dead load and attendant wave splitting effect caused by the gyroscopic moment of the system. The wave mechanics result paves the way for the non-destructive damage testing of the element.
Authors: Afshin Banazadeh, Farzad Banazadeh
Abstract: This paper provides an understanding of counter-flow fluidic thrust vectoring, in the presence of the secondary air vacuum, applied to the exhaust nozzle of a micro-jet engine. An analytical and numerical study is performed here on a divergent collar surface adjacent to the cylindrical exhaust duct system. The vectoring angle is controlled by manipulating the momentum flux through a vacuum gap that is located on a circle concentric to the main nozzle. Three dimensional numerical simulations are conducted by utilizing a computational fluid dynamics model with two-equation standard k-ε turbulence model to study the pressure and velocity distribution of internal flow and nozzle geometry. Moreover, an analytical validation is carried out based on the known mathematical form of the governing equations of fluid dynamics over the sinusoidal wall. It is shown that the analytical results are in good agreement with numerical simulations, which also show that the pressure coefficient over the collar surface has the same trend as given by computational simulation. Similarly, the results of the numerical method are also verified against experimental results that were approved by previous research in area of numerical model for co-flow fluidic thrust vectoring technique.
Authors: Awang Raisudin Awang Saifudin, Nurul Musfirah Mazlan
Abstract: Aircraft engines are exposed to degradation due to several factors such as environmental air pollution, fuel content and ageing or degradation of engine’s components, which are experienced within specified time. While the turbofan in operation, its components deteriorate and consequently affect its performance. This study is aimed to computationally investigate the effect of components degradation on engine performance. A high bypass turbofan engine operated at cruise is selected for this evaluation and the simulation was performed using the Gas Turbine Simulation Program (GSP). The affected components considered are turbines and compressors with deterioration rate ranging from 0% to 5%. The effect of selected deterioration rate on engine thrust and thrust specific fuel consumption (TSFC) is studied. Results obtained show an agreement with literature where reduction in engine thrust and TSFC are observed. Turbine’s fouling has been found to be more severe than erosion in terms of power and efficiency losses. However, in terms of the overall performance, the erosion effect is more severe than fouling.
Authors: Jun Ting Xiang, Jӧrg Uwe Schlüter, Fei Duan
Abstract: The knowledge about changes of flow field properties during axial compressor operationat high and relatively low speed is limited. This work provides a numerical approach to addressthese problems. Validations about the numerical scheme and the test of compressor performance at various operating speeds are conducted. The results show that computational fluid dynamics (CFD)is capable in predicting the compressor performance. Flow property changes during the compressoroperation are discussed and explanations are proposed. This work reinforces the understanding of compressor operation and provides valid results for future reference.
Authors: W. Ghopa Wan Aizon, Kenichi Funazaki, Mohd Radzi Abu Mansor
Abstract: Modern gas turbine requires sophisticated cooling technologies to avoid thermal failure due to the extreme operating environment. Film cooling is one of the most important cooling technologies used for gas turbine hot-section components, particularly for blade aerofoil surfaces and endwall. Previous research has shown that the endwall region is considerably more difficult to cool than the blade aerofoil surfaces because of the existence of complex secondary flow structures such as horse-shoe vortex, cross flow and passage vortex in the blade passage. Therefore, this study focuses on aerodynamics interaction of the cooling air through the upstream slot with the secondary flow field. Experiments carried out using 5-holes Pitot tube have revealed the secondary flow field at blade downstream of linear cascade of high pressure turbine. A baseline condition without any leakage flows was compared with the leakage ejection case. Finally, both cases were validated by simulations from commercial software, ANSYS CFX.
Authors: Cheng Tung Chong, Simone Hochgreb
Abstract: Detailed characterisation of spray atomization of an injector is important for combustor design and modelling. In this paper, the effects of air/fuel mass ratio on the spray characteristics of an internal-mix airblast atomizer were examined. Distribution of the spatial mean droplet axial velocity and size were measured simultaneously using a phase Doppler anemometry (PDA). In general, small droplets are distributed at the center of the spray with maximum velocity. The droplet size increases with increasing radial distance from the spray centreline, but the drop velocity decreases to a minimum at the spray edge. Increasing the atomizing air/fuel mass ratio reduces fuel droplet size due to increased shear.

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