Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 48522

Aerospace and Mechanical Engineering

983
83659
Numerical Analysis of Effect of Crack Location on the Crack Breathing Behavior
Abstract:
In this work, a three dimensional finite element model was developed to investigate the crack breathing behavior at different crack locations considering the effect of unbalance force. A two-disk rotor with a crack is simulated using ABAQUS. The duration of each crack status (open, closed and partially open/closed) during a full shaft rotation was examining to analysis the crack breathing behavior. Different crack breathing behavior found at different crack locations when crack in an unbalanced shaft including single status. The breathing behavior of crack along the shaft length is divided into different regions depending on the unbalance force and crack location. The simulated results in this work can be further utilised to obtain the time-varying stiffness matrix of the cracked shaft element under the influence of unbalance force.
Digital Article Identifier (DAI):
982
83538
Response Regimes and Vibration Mitigation in Equivalent Mechanical Model of Strongly Nonlinear Liquid Sloshing
Abstract:
Equivalent mechanical model of liquid sloshing in partially-filled cylindrical vessel is treated in the cases of free oscillations and of horizontal base excitation. The model is designed to cover both the linear and essentially nonlinear sloshing regimes. The latter fluid behaviour might involve hydraulic impacts interacting with the inner walls of the tank. These impulsive interactions are often modeled by high-power potential and dissipation functions. For the sake of analytical description, we use the traditional approach by modeling the impacts with velocity-dependent restitution coefficient. This modelling is similar to vibro-impact nonlinear energy sink (VI NES) which was recently explored for its vibration mitigation performances and nonlinear response regimes. Steady-state periodic regimes and chaotic strongly modulated responses (CSMR) are detected. Those dynamical regimes were described by the system's slow motion on the slow invariant manifold (SIM). There is a good agreement between the analytical results and numerical simulations. Subsequently, Finite-Element (FE) method is used to determine and verify the model parameters and to identify dominant dynamical regimes, natural modes and frequencies. The tank failure modes are identified and critical locations are identified. Mathematical relation is found between degrees-of-freedom (DOFs) motion and the mechanical stress applied in the tank critical section. This is the prior attempt to take under consideration large-amplitude nonlinear sloshing and tank structure elasticity effects for design, regulation definition and resistance analysis purposes. Both linear (tuned mass damper, TMD) and nonlinear (nonlinear energy sink, NES) passive energy absorbers contribution to the overall system mitigation is firstly examined, in terms of both stress reduction and time for vibration decay.
Digital Article Identifier (DAI):
981
83537
Vibration Mitigation in Partially Liquid-Filled Vessel Using Passive Energy Absorbers
Abstract:
The following study deals with fluid vibration of a liquid in a partially filled vessel under periodic ground excitation. This external excitation might lead to hidraulic impact applied on the vessel inner walls. In order to model these sloshing dynamic regimes, several equivalent mechanical models were suggested in the literature, such as series of pendula or mass-spring systems that are able to impact the inner tank walls. In the following study, we use the latter methodology, use parameter values documented in literature corresponding to cylindrical tanks and consider structural elasticity of the tank. The hydraulic impulses are modeled by the high-exponent potential function. Additional system parameters are found with the help of Finite-Element (FE) analysis. Model-driven stress assessment method is developed. Finally, vibration mitigation performances of both tuned mass damper (TMD) and nonlinear energy sink (NES) are examined.
Digital Article Identifier (DAI):
980
83532
Evaluation of the Elastic Mechanical Properties of a Hybrid Adhesive Material
Abstract:
Adhesive materials and adhesion have been the focal point of multiple research works related to numerous applications, particularly, aerospace and aviation industries. To enhance the properties of conventional adhesive materials, additives have been introduced into the mix in order to enhance their mechanical and physical properties by creating a hybrid adhesive material. The evaluation of the mechanical properties of such hybrid adhesive materials is thus of an essential requirement for the purpose of properly modeling their behavior accurately. This paper presents an approach/tool to simulate the behavior such hybrid adhesives in a way that will allow researchers to better understand their behavior while in service.
Digital Article Identifier (DAI):
979
83430
Performance Analysis of the Precise Point Positioning Data Online Processing Service and Using Monitoring Plate Tectonic of Thailand
Abstract:
Precise Point Positioning (PPP) technique is use to improve accuracy by using precise satellite orbit and clock correction data, but this technique is complicated methods and high costs. Currently, there are several online processing service providers which offer simplified calculation. In the first part of this research, we compare the efficiency and precision of four software. There are three popular online processing service providers: Australian Online GPS Processing Service (AUSPOS), CSRS-Precise Point Positioning and CenterPoint RTX post processing by Trimble and 1 offline software, RTKLIB, which collected data from 10 the International GNSS Service (IGS) stations for 10 days. The results indicated that AUSPOS has the least distance root mean square (DRMS) value of 0.0029 which is good enough to be calculated for monitoring the movement of tectonic plates. The second, we use AUSPOS to process the data of geodetic network of Thailand. In December 26, 2004, the earthquake occurred a 9.3 MW at the north of Sumatra that highly affected all nearby countries, including Thailand. Earthquake effects have led to errors of the coordinate system of Thailand. The Royal Thai Survey Department (RTSD) is primarily responsible for monitoring of the crustal movement of the country. The difference of the geodetic network movement is not the same network and relatively large. This result is needed for survey to continue to improve GPS coordinates system in every year. Therefore, in this research we chose the AUSPOS to calculate the magnitude and direction of movement, to improve coordinates adjustment of the geodetic network consisting of 19 pins in Thailand during October 2013 to November 2017. Finally, results are displayed on the simulation map by using the ArcMap program with the Inverse Distance Weighting (IDW) method. The pin with the maximum movement is pin no. 3239 (Tak) in the northern part of Thailand. This pin moved in the south-western direction to 11.04 cm. Meanwhile, the directional movement of the other pins in the south gradually changed from south-west to south-east, i.e., in the direction noticed before the earthquake. The magnitude of the movement is in the range of 4 - 7 cm, implying small impact of the earthquake. However, the GPS network should be continuously surveyed in order to secure accuracy of the geodetic network of Thailand.
Digital Article Identifier (DAI):
978
83402
Post Coronary Artery Stenting Reflighting: Need for Change in Policy with Changing Antiplatelet Therapy
Abstract:
Background: Coronary artery Disease (CAD) is a common cause of morbidity, mortality and reason for unfitness amongst aircrew. Coronary angioplasty and stenting are the standard of care for CAD. Antiplatelet drugs like Aspirin and Clopidogrel(Dual Antiplatelet therapy) are routinely prescribed post-stenting which are permitted for flying. However, in the recent past, Ticagrelor is being used in place of Clopidogrel as per ACC AHA and ESC guidelines. However Ticagrelor is not permitted for flying. Case Presentation: A 55-year-old pilot suffered Anterior Wall Myocardial Infarction. Angiography showed blockages in Left Anterior Descending Artery(LAD) and Right coronary artery (RCA). He underwent primary angioplasty and stenting LAD and subsequent stenting to RCA. Recovery was uneventful. One year later he was asymptomatic with normal Left ventricular function and no reversible perfusion defect on stress MPI. He had patent stents and coronaries on check angiogram. However, he was not allowed to fly since he was on Ticagrelor. He had to be switched over to Clopidogrel from Ticagrelor one year after stenting to permit him for flying. Similarly, switching had to be done in a 45-year-old pilot. Ticagrelor has been proven to be more effective than clopidogrel and as safe as Clopidogrel in preventing stent thrombosis. If Clopidogrel is being permitted, there is no need to restrict Ticagrelor. Hence "Policy" needs to be changed. Conclusions: Dual Antiplatelet therapy is the standard of care post coronary stenting which has been proved safe and effective. Policy needs to be changed to permit flying with Ticagrelor which is more effective than Clopidogrel and equally safe.
Digital Article Identifier (DAI):
977
83238
Application of Phase Shift Keying Modulation in ADS-B 1090 Extended Squitter Authentication
Abstract:
Since the presence of Next Generation Air Transportation System (NextGen), Automatic Dependent Surveillance-Broadcast (ADS-B) has raised specific concerns related to the privacy and security, due to its vulnerable, low-level of security and limited payload. In this paper, the authors introduce and analyze the combination of Pulse Amplitude Modulation (PAM) and Phase Shift Keying (PSK) Modulation in conventional ADS-B, forming Secure ADS-B (SADS-B) avionics. In order to demonstrate the potential of this combination, Hardware-in-the-loop (HIL) simulation was used. The tests' results show that, on the one hand, SADS-B can offer five times the payload as its predecessor. This embedded payload in the phase of SADS-B can be used in various applications, enhance the ability of ADS-B. On the other hand, by using the extra phase modulated bits as a digital signature to authenticate ADS-B messages, SADS-B can increase the security of ADS-B, thus ensure a more secure aviation as well. More importantly, SADS-B is compatible with the current ADS-B In and Out. Hence, no significant modifications will be needed to implement this idea. As a result, SADS-B can be considered the most promising approach to enhance the capability and security of ADS-B.
Digital Article Identifier (DAI):
976
83110
Aerodynamic Study of an Open Window Moving Bus with Passengers
Abstract:
In many countries, buses are the principal means of transport, of which a majority are naturally ventilated with open windows. The design of this ventilation has little scientific basis and to address this problem a study has been undertaken involving both experiments and numerical simulations. The flow pattern inside and around of an open window bus with passengers has been investigated in detail. A full scale three-dimensional numerical simulation has been used for a) a bus with closed windows and b) with open windows. In either simulation, the bus had 58 seated passengers. The bus dimensions used were 2500 mm wide × 2500 mm high (exterior) × 10500 mm long and its speed was set at 40 km/h. In both cases, the flow separates at the top front edge forming a vortex and reattaches close to the mid-length. This attached flow separates once more as it leaves the bus. However, the strength and shape of the vortices at the top front and wake region is different for both cases. The streamline pattern around the bus is also different for the two cases. For the bus with open windows, the dominant airflow inside the bus is from the rear to the front of the bus and air velocity at the face level of the passengers was found to be 1/10th of the free stream velocity. These findings are in good agreement with flow visualization experiments performed in a water channel at 10 m/s, and with smoke/tuft visualizations in a wind tunnel with a free-stream velocity of approximately 40 km/h on a 1:25 scaled Perspex model.
Digital Article Identifier (DAI):
975
82932
Effects of Cattaneo-Christov Heat Flux on 3D Magnetohydrodynamic Viscoelastic Fluid Flow with Variable Thermal Conductivity
Abstract:
A mathematical model has been envisaged to discuss three-dimensional Viscoelastic fluid flow with an effect of Cattaneo-Christov heat flux in attendance of magnetohydrodynamic (MHD). Variable thermal conductivity with the impact of homogeneous-heterogeneous reactions and convective boundary condition is also taken into account. Homotopy analysis method is engaged to obtain series solutions. Graphical illustrations depicting behaviour of sundry parameters on skin friction coefficient and all involved distributions are also given. It is observed that velocity components are decreasing functions of Viscoelastic fluid parameter. Furthermore, strength of homogeneous and heterogeneous reactions have opposite effects on concentration distribution. A comparison with a published paper has also been established and an excellent agreement is obtained; hence reliable results are being presented.
Digital Article Identifier (DAI):
974
82871
Design Optimization for Sound Absorption Material of Multi-Layer Structure
Abstract:
Sound absorbing material is used as automotive interior material. Sound absorption coefficient should be predicted to design it. However, it is difficult to predict sound absorbing coefficient because it is comprised of several material layers. So, its targets are achieved through many experimental tunings. It causes a lot of cost and time. In this paper, we propose the process to estimate the sound absorption coefficient with multi-layer structure. In order to estimate the coefficient, physical properties of each material are used. These properties also use predicted values by Foam-X software using the sound absorption coefficient data measured by impedance tube. Since there are many physical properties and the measurement equipment is expensive, the values predicted by software are used. Through the measurement of the sound absorption coefficient of each material, its physical properties are calculated inversely. The properties of each material are used to calculate the sound absorption coefficient of the multi-layer material. Since the absorption coefficient of multi-layer can be calculated, optimization design is possible through simulation. Then, we will compare and analyze the calculated sound absorption coefficient with the data measured by scaled reverberation chamber and impedance tubes for a prototype. If this method is used when developing automotive interior materials with multi-layer structure, the development effort can be reduced because it can be optimized by simulation. Therefore, cost and time can be saved.
Digital Article Identifier (DAI):
973
82812
Wind Tunnel Study on Efficiency Improvements of a Wing Embedded Lifting Fan Remaining Open in Cruise Flight
Abstract:
The ability to generate additional lift in hovering flight by a lifting fan is of great interest for aircrafts with vertical take-off and landing capabilities. So far, in most cases, the duct containing the fan has been closed by a fairing during cruise flight. Keeping the fan ducts open for cruise flight supersedes complex mechanics for closing the openings properly and reduces the number of parts and overall weight while enhancing robustness and reliability. The investigated aircraft concept includes/incorporates two large wing-embedded lifting fans for vertical take-off and landing. The overall aerodynamic performance of the airframe is negatively affected by the disturbed, uneven flow around the fan ducts that reduces lift and increases drag. The result of an explorative study conducted by the authors is that any rotation of the fans or installation of grids across the fan duct inlet plane have significant negative impact on the aerodynamic efficiency. A positive impact, however, has been predicted for optimized inlet and outlet geometries of the fan duct. Published in 2016 by the authors, a step at the front end of the fan duct's outlet was used as element for improving aerodynamic performance for the first time. A rounded inlet lip on the upper side of the wing appeared to be advantageous for the cruise performance. Despite these findings, it is still unknown whether an increase of the inlet lip radius will have further advantage or if the inlet lip radius can be optimized regarding inlet lip suction during hovering, without compromising cruise flight performance. A wind tunnel study was conducted in the Seitenwindversuchsanlage Göttingen at the German Aerospace Center in Göttingen to quantify the impact of the duct inlet radius and step. Different model configurations (30 mm and 60 mm inlet lip radius; no step, 9 mm, 11 mm, and 13 mm step height) were investigated at 16.5 m/s and 33 m/s flow velocity and between -4° and 10° angle of attack using force, surface pressure and stereoscopic particle image velocimetry. The diameter of the fixed rotor was 360 mm, and the local chord length was 600 mm. The results show that a variation of the inlet radius on the upper side of the wing only has marginal impact on the achievable lift-to-drag ratio. It can be concluded that the inlet radius can be optimized for maximum fan efficiency during hovering flight. The impact of the step on the lift-to-drag ratio is significant. All steps increase the aerodynamic efficiency between +2° and +10° angle of attack for both inlet lip radii. The measurement data indicate that this is caused by a combination of increased pressure on the pressure side of the wing, rearward movement of the stagnation point, increased suction on the suction side of the wing and delayed detachment on the fan duct inlet lip. The measurement results serve as a reference database for the validation of future numerical flow simulations on the optimization of the height and step inclination as functions of the angle of attack and Reynolds number.
Digital Article Identifier (DAI):
972
82658
Analysis of the Velocity Mixture through a Partially Premixed Burner: Modeling, Simulation and Validation
Abstract:
The problem of lack of knowledge of the parameters and variables involved in the mixture mechanics of a partially premixed burner results in the production and improvement of these components by means of heuristic methods. Mathematical modeling, CFD (Computational Fluid Dynamics) simulation and validation, of the primary, secondary air velocity, and of the methane-oxygen mixture through the burner was developed. The mathematical model was constructed from the general energy equation. The measurement of the velocity of primary and secondary air and the output of the mixture was carried out using the PIV (Particle Image Velocimetry) technique. The results show that the speed of the mixture through the burner is a function of the cross-sectional area, the pressure, and the density of the mixture in the various sections. The correlation of the values obtained between the mathematical model and the CFD simulation is 0.97; the experimental results and the simulation shown an average difference of 0.65 m/s in relation to the primary and secondary air velocity, and the mixing output. It is concluded that, based on the knowledge of the parameters that govern the mechanics of the mixture, it may be possible to propose a methodology to design this type of components based on scientific and engineering foundations.
Digital Article Identifier (DAI):
971
82596
Nonlinear Passive Shunt for Electroacoustic Absorbers Using Nonlinear Energy Sink
Abstract:
Acoustic absorber devices play an important role reducing the noise at the propagation and reception paths. An electroacoustic absorber consists of a loudspeaker coupled to an electric shunt circuit, where the membrane is playing the role of an absorber/reflector of sound. Although the use of linear shunt resistors at the transducer terminals, has shown to improve the performances of the dynamical absorbers, it is nearly efficient in a narrow frequency band. Therefore, and since nonlinear phenomena are promising for their ability to absorb the vibrations and sound on a larger frequency range, we propose to couple a nonlinear electric shunt circuit at the loudspeaker terminals. Then, the equivalent model can be described by a 2 degrees of freedom system, consisting of a primary linear oscillator describing the dynamics of the loudspeaker membrane, linearly coupled to a cubic nonlinear energy sink (NES). The system is analytically treated for the case of 1:1 resonance, using an invariant manifold approach at different time scales. The proposed methodology enables us to detect the equilibrium points and fold singularities at the first slow time scales, providing a predictive tool to design the nonlinear circuit shunt during the energy exchange process. The preliminary results are promising; a significant improvement of acoustic absorption performances are obtained.
Digital Article Identifier (DAI):
970
82474
Optimization of Process Parameters Affecting on Spring-Back in V-Bending Process for High Strength Low Alloy Steel HSLA 420 Using FEA (HyperForm) and Taguchi Technique
Abstract:
In this study, process parameters like punch angle, die opening, grain direction and pre-bend condition of the strip for deep draw of high strength low alloy steel HSLA 420 are investigated. The finite element method (FEM) in association with the Taguchi and the analysis of variance (ANOVA) techniques are carried out to investigate the degree of importance of process parameters in V-bending process for HSLA 420&ST12 grade material. From results, it is observed that punch angle had a major influence on the spring-back. Die opening also showed very significant role on spring back. On the other hand, it is revealed that grain direction had the least impact on spring back, however, if strip from flat sheet is taken then it is less prone to spring back as compared to the strip from sheet metal coil. HyperForm software is used for FEM simulation and experiments are designed using Taguchi method. Percentage contribution of the parameters is obtained through the ANOVA techniques.
Digital Article Identifier (DAI):
969
82393
Structural Behavior of Non-Prismatic Mono-Symmetric Beam
Abstract:
This paper attempts to understand the structural behavior of non-prismatic channel beams subjected to bending through finite element (FE) analysis. The present study aims at shedding some light on how tapered channel beams behave by studying the effect of taper ratio on structural behavior. As a weight reduction is always desired in aerospace structures beams are tapered in order to obtain highest structural efficiency. FE analysis has been performed to study the effect of taper ratio on linear deflection, lateral torsional buckling, non-linear parameters, stresses and dynamic parameters. Taper ratio tends to affect the mechanics of tapered beams innocuously and adversely. Consequently, it becomes important to understand and document the mechanics of channel tapered beams. Channel beams generally have low torsional rigidity due to the off-shear loading. The effect of loading type and location of applied load have been studied for flange taper, web taper and symmetric taper for different conditions. Among these, as the taper ratio is increased, the torsional angular deflection increases but begins to decrease when the beam is web tapered and symmetrically tapered for a mid web loaded beam. But when loaded through the shear center, an increase in the torsional angular deflection can be observed with increase in taper ratio. It should be considered which parameter is tapered to obtain the highest efficiency.
Digital Article Identifier (DAI):
968
82392
Experimental Approach for Determining Hemi-Anechoic Characteristics of Engineering Acoustical Test Chambers
Abstract:
An experimental methodology is proposed for determining hemi-anechoic characteristics of an engineering acoustic room built at the facilities of Universidad Nacional de Colombia to evaluate the free-field conditions inside the chamber. Experimental results were compared with theoretical ones in both, the source and the sound propagation inside the chamber. Acoustic source was modeled by using monopole radiation pattern from punctual sources and the image method was considered for dealing with the reflective plane of the room, that means, the floor without insulation. Finite-difference time-domain (FDTD) method was implemented to calculate the sound pressure value at every spatial point of the chamber. Comparison between theoretical and experimental data yields to minimum error, giving satisfactory results for the hemi-anechoic characterization of the chamber.
Digital Article Identifier (DAI):
967
82178
Classification of Impact Damages with Respect of Damage Tolerance Design Approach and Airworthiness Requirements
Abstract:
This paper describes airworthiness requirements with respect damage tolerance. Damage tolerance determines the amount and magnitude of damage on parts of the airplane. Airworthiness requirements determine the amount of damage that can still be in flight capable of the condition. Component damage can be defined as barely visible impact damage, visible impact damage or clear visible impact damage. Damage is also distributed it according to the velocity. It is divided into low or high velocity impact damage. The severity of damage to the part of airplane divides the airworthiness requirements into several categories according to severity. Airworthiness requirements are determined by type airplane. All types of airplane do not have the same conditions for airworthiness requirements. This knowledge is important for designing and operating an airplane.
Digital Article Identifier (DAI):
966
82166
Internal and External Overpressure Calculation for Vented Gas Explosion by Using a Combined Computational Fluid Dynamics Approach
Abstract:
Recent oil and gas accidents have reminded us the severe consequences of gas explosion on structure damage and financial loss. In order to protect the structures and personnel, engineers and researchers have been working on numerous different explosion mitigation methods. Amongst, venting is the most economical approach to mitigate gas explosion overpressure. In this paper, venting is used as the overpressure alleviation method. A theoretical method and a numerical technique are presented to predict the internal and external pressure from vented gas explosion in a large enclosure. Under idealized conditions, a number of experiments are used to calibrate the accuracy of the theoretically calculated data. A good agreement between the theoretical results and experimental data is seen. However, for realistic scenarios, the theoretical method over-estimates internal pressures and is incapable of predicting external pressures. Therefore, a CFD simulation procedure is proposed in this study to estimate both the internal and external overpressure from a large-scale vented explosion. Satisfactory agreement between CFD simulation results and experimental data is achieved.
Digital Article Identifier (DAI):
965
82099
Experiment on Free and Forced Heat Transfer and Pressure Drop of Copper Oxide-Heat Transfer Oil Nanofluid (CuO-HTO) in Horizontal and Inclined Microfin Tube
Abstract:
In this paper, the combined free and forced convection heat transfer of the CuO-HTO nanofluid flow in horizontal and inclined microfin tubes is studied experimentally. The flow regime is laminar and pipe surface temperature is constant. The effect of nanoparticle and microfin tube on the heat transfer rate is investigated as the Richardson number is between 0.1 and 0.7. The results show an increasing nanoparticle concentration between 0% and 1.5% leads to enhance the combined free and forced convection heat transfer rate. According to the results, five correlations are proposed to provide estimating the free and forced heat transfer rate as the increasing Richardson number from 0.1 to 0.7. The maximum deviation of both correlations is less than 16%. Moreover, four correlation is suggested to assess the Nusselt number based on the Rayleigh number in inclined tubes from 1800000 to 7000000. The maximum deviation of the correlation is almost 16%. The Darcy friction factor of the nanofluid flow has been investigated. Furthermore, (CuO-HTO) nanofluid flows in inclined microfin tubes.
Digital Article Identifier (DAI):
964
82093
Studying the Dynamical Response of Nano-Microelectromechanical Devices for Nanomechanical Testing of Nanostructures
Abstract:
Characterizing the fatigue and fracture properties of nanostructures is one of the most challenging tasks in nanoscience and nanotechnology due to lack of a MEMS/NEMS device for generating uniform cyclic loadings at high frequencies. Here, the dynamic response of a recently proposed MEMS/NEMS device under different inputs signals is completely investigated. This MEMS/NEMS device is designed and modeled based on the electromagnetic force induced between paired parallel wires carrying electrical currents, known as Ampere’s Force Law (AFL). Since this MEMS/NEMS device only uses two paired wires for actuation part and sensing part, it represents highly sensitive and linear response for nanostructures with any stiffness and shapes (single or arrays of nanowires, nanotubes, nanosheets or nanowalls). In addition to studying the maximum gains at different resonance frequencies of the MEMS/NEMS device, its dynamical responses are investigated for different inputs and nanostructure properties to demonstrate the capability, usability, and reliability of the device for wide range of nanostructures. This MEMS/NEMS device can be readily integrated into SEM/TEM instruments to provide real time study of the fatigue and fracture properties of nanostructures as well as their softening or hardening behaviors, and initiation and/or propagation of nanocracks in them.
Digital Article Identifier (DAI):
963
82081
Design and Burnback Analysis of Three Dimensional Modified Star Grain
Abstract:
The determination of grain geometry is an important and critical step in the design of solid propellant rocket motor. In this study, the design process involved parametric geometry modeling in CAD, MATLAB coding of performance prediction and 2D star grain ignition experiment. The 2D star grain burnback achieved by creating new surface via each web increment and calculating geometrical properties at each step. The 2D star grain is further modified to burn as a tapered 3D star grain. Zero dimensional method used to calculate the internal ballistic performance. Experimental and theoretical results were compared in order to validate the performance prediction of the solid rocket motor. The results show that the usage of 3D grain geometry will decrease the pressure inside the combustion chamber and enhance the volumetric loading ratio.
Digital Article Identifier (DAI):
962
82069
Nano Sol Based Solar Responsive Smart Window for Aircraft
Abstract:
This research work was based on developing a solar responsive aircraft window panel which can be used as a self-cleaning surface and also a surface which degrade Volatile Organic compounds (VOC) available in the aircraft cabin areas. Further, this surface has the potential of harvesting energy from Solar. The transparent inorganic nano sol solution was prepared. The obtained sol solution was characterized using X-ray diffraction, Particle size analyzer and FT-IR. The existing nano material which shows the similar characteristics was also used to compare the efficiencies with the newly prepared nano sol. Nano sol solution was coated on cleaned four aircraft window pieces separately using a spin coater machine. The existing nano material was dissolved and prepared a solution having the similar concentration as nano sol solution. Pre-cleaned four aircraft window pieces were coated with this solution and the rest cleaned four aircraft window pieces were considered as control samples. The control samples were uncoated from anything. All the window pieces were allowed to dry at room temperature. All the twelve aircraft window pieces were uniform in all the factors other than the type of coating. The surface morphologies of the samples were analyzed using SEM. The photocatalytic degradation of VOC was determined after incorporating gas of Toluene to each sample followed by the analysis done by UV-VIS spectroscopy. The self- cleaning capabilities were analyzed after adding of several types of stains on the window pieces. The self-cleaning property of each sample was analyzed using UV-VIS spectroscopy. The highest photocatalytic degradation of Volatile Organic compound and the highest photocatalytic degradation of stains were obtained for the samples which were coated by the nano sol solution. Therefore, the experimental results clearly show that there is a potential of using this nano sol in aircraft window pieces which favors the self-cleaning property as well as efficient photocatalytic degradation of VOC gases. This will ensure safer environment inside aircraft cabins.
Digital Article Identifier (DAI):
961
81819
Increase of Sensitivity in 3D Suspended Polymeric Microfluidic Platform through Leteral Misalignment
Abstract:
In the present project, a new design of the suspended polymeric microfluidic platform is introduced that is fabricated from the 3 polymeric layers. Due to high accuracy, simplicity, low price and portability of this microfluidic platform, it can be reliable alternative microsensor instead of current microfluidic platforms and sensors. Our innovation is that although the dimensions of this platform are constant, by misaligning the microchannels embedded in the suspended microfluidic platform, the sensitivity can be highly increased. The investigation is studied on four fluids, including water, seawater, milk, and blood for flow ranges from 5 to 70 µl/min to select the best design with the highest sensitivity. The best design in this study shows increase sensitivity around 40% for the different liquids just by misaligning the microchannels embedded in the suspended polymeric microfluidic platform.
Digital Article Identifier (DAI):
960
81628
Fluid Added Mass for Floating Structure under Flexural Vibration
Abstract:
Unsteady motion of a solid structure which is in contact with a fluid medium is affected by additional fluid inertia forces. These forces are commonly represented by the so-called added mass. For any rigid body motion, especially oscillation, the added mass is associated with the translation and rotation in the x, y and z directions which are independent from each other. However, this way of representing the added mass for structures under flexural vibration is no longer valid due to the spatial variation of fluid loadings across the interface between the structure and fluid. In this work, the concept of modal superposition was employed to relate the added mass effects to different modes of vibration. First, the natural vibration of the structure without the fluid (dry-mode) is solved by using Finite Element method and the natural frequencies and mode shapes are extracted out. A set of mode shapes are selected to write any arbitrary response of the structure in terms of their linear sum. Then, for each and every mode shape, the fluid flow problem is solved, provided that the mode shape prescribes the displacement at the interface and the free surface of the fluid is pressure-zero. Without loss of generality, any gravitational effect on the free-surface wave is neglected, and the fluid is assumed to be non-viscous and incompressible. The potential flow is solved by Boundary Element method for a semi-infinite fluid domain. By the virtue of the Newton’s third law, the partial fluid loadings acting on the structure can be calculated from the dynamic pressure, obtained the flow solution. Finally, the so-called modal added mass is computed from partial loadings for each mode separately. The modal added mass, written as a square matrix, can be directly included in the generalized vibration equation of the wet structure, from which the wet-mode natural frequencies and mode shapes can be computed. This approach of modal added mass is valid for any geometry, especially the ship-like structures. From the two case studies, a hemispherical shell and a sanitized container-ship hull, it was found that a single value for the added mass associated to a dry mode shape can give the shift in the natural frequency as compared to the dry-mode one. Also, it was concluded that the modal added mass becomes less significant for the higher mode shapes associated with higher natural frequencies. It is noted that the other advantage of using modal superposition is to significantly reduce the size of the system matrices from the total number of degrees of freedom to the number of selected mode shapes.
Digital Article Identifier (DAI):
959
81597
Radial Fuel Injection Computational Fluid Dynamics Model for a Compression Ignition Two-Stroke Opposed Piston Engine
Abstract:
Designing a new engine requires a large number of different cases to be considered. Especially different injector parameters and combustion chamber geometries. This is essential when developing an engine with unconventional build – compression ignition, two-stroke operating with direct side injection. Computational Fluid Dynamics modelling allows to test those different conditions and seek for the best conditions with correct combustion. This research presents the combustion results for different injector and combustion chamber cases. The shape of combustion chamber is different than for conventional engines as it requires side injection. This completely changes the optimal shape for the given condition compared to standard automotive heart shaped combustion chamber. Because the injection is not symmetrical there is a strong influence of cylinder swirl and piston motion on the injected fuel stream. The results present the fuel injection phenomena allowing to predict the right injection parameters for a maximum combustion efficiency and minimum piston heat loads. Acknowledgement: This work has been realized in the cooperation with The Construction Office of WSK "PZL-KALISZ" S.A." and is part of Grant Agreement No. POIR.01.02.00-00-0002/15 financed by the Polish National Centre for Research and Development.
Digital Article Identifier (DAI):
958
81595
Selecting a Material for an Aircraft Diesel Engine Block
Abstract:
Selecting appropriate materials is presently a complex task as material databases cover tens of thousands of different types of materials. Product designing proceeds in numerous stages and in most of them there are open questions with not only one correct solution but better and worse ones. This paper overviews the Diesel engine body construction materials mentioned in the literature and discusses a certain practical method to select materials for a cylinder head and a Diesel engine block as a prototype. The engine body, depending on its purpose, is most frequently iron or aluminum. If it is important to optimize parts to achieve low weight, aluminum alloys are usually applied, especially in the automotive and aviation industries. In the latter case, weight is even more important so new types of magnesium alloys which are even lighter than aluminum ones are developed and used. However, magnesium alloys are, for example, more flammable and not enough strong so, for safety reasons, this type of material is not used solely in engine bodies. Acknowledgement: This work has been realized in the cooperation with The Construction Office of WSK "PZL-KALISZ" S.A." and is part of Grant Agreement No. POIR.01.02.00-00-0002/15 financed by the Polish National Centre for Research and Development.
Digital Article Identifier (DAI):
957
81591
Numerical Investigation of the Electromagnetic Common Rail Injector Characteristics
Abstract:
The paper describes the modeling of a fuel injector for common rail systems. A one-dimensional model of a solenoid-valve-controlled injector with Valve Closes Orifice (VCO) spray was modelled in the AVL Hydsim. This model shows the dynamic phenomena that occur in the injector. The accuracy of the calibration, based on a regulation of the parameters of the control valve and the nozzle needle lift, was verified by comparing the numerical results of injector flow rate. Our model is capable of a precise simulation of injector operating parameters in relation to injection time and fuel pressure in a fuel rail. As a result, there were made characteristics of the injector flow rate and backflow.
Digital Article Identifier (DAI):
956
81533
Heat Transfer Phenomena Identification of a Non-Active Floor in a Stack-Ventilated Building in Summertime: Empirical Study
Abstract:
An experimental study in a Plus Energy House (PEH) prototype was conducted in August 2016. It aimed to highlight the energy charge and discharge of a concrete-slab floor submitted to the day-night-cycles heat exchanges in the southwestern part of France and to identify the heat transfer phenomena that take place in both processes: charge and discharge. The main features of this PEH, significant to this study, are the following: (i) a non-active slab covering the major part of the entire floor surface of the house, which include a concrete layer 68 mm thick as upper layer; (ii) solar window shades located on the north and south facades along with a large eave facing south, (iii) large double-glazed windows covering the majority of the south facade, (iv) a natural ventilation system (NVS) composed by ten automatized openings with different dimensions: four are located on the south facade, four on the north facade and two on the shed roof (north-oriented). To highlight the energy charge and discharge processes of the non-active slab, heat flux and temperature measurement techniques were implemented, along with airspeed measurements. Ten 'measurement-poles' (MP) were distributed all over the concrete-floor surface. Each MP represented a zone of measurement, where air and surface temperatures, and convection and radiation heat fluxes, were intended to be measured. The airspeed was measured only at two points over the slab surface, near the south facade. To identify the heat transfer phenomena that take part in the charge and discharge process, some relevant dimensionless parameters were used, along with statistical analysis; heat transfer phenomena were identified based on this analysis. Experimental data, after processing, had shown that two periods could be identified at a glance: charge (heat gain, positive values) and discharge (heat losses, negative values. During the charge period, on the floor surface, radiation heat exchanges were significantly higher compared with convection. On the other hand, convection heat exchanges were significantly higher than radiation, in the discharge period. Spatially, both, convection and radiation heat exchanges are higher near the natural ventilation openings and smaller far from them, as expected. Experimental correlations have been determined using a linear regression model, showing the relation between the Nusselt number with relevant parameters: Peclet, Rayleigh, and Richardson numbers. This has led to the determination of the convective heat transfer coefficient and its comparison with the convective heat coefficient resulting from measurements. Results have shown that forced and natural convection coexist during the discharge period; more accurate correlations with the Peclet number than with the Rayleigh number, have been found. This may suggest that forced convection is stronger than natural convection. Yet, airspeed levels encountered suggest that it is natural convection that should take place rather than forced convection. Despite this, Richardson number values encountered, indicate otherwise. During the charge period, air-velocity levels might indicate that none air motion occurs, which might lead to heat transfer by diffusion instead of convection.
Digital Article Identifier (DAI):
955
81527
Investigation of the Aerodynamic Characteristics of a Vertical Take-Off and Landing Mini Unmanned Aerial Vehicle Configuration
Abstract:
The purpose of the paper is to model and evaluate the aerodynamic coefficients and stability derivatives of a Vertical, Take-off and Landing Unmanned Aerial Vehicle configuration (VTOL UAV), which is a fixed wing UAV and a quad-copter hybrid capable of both vertical and conventional take-off and/or landing. The aerodynamic analysis of this configuration was carried out using CFD commercial package Ansys Fluent. Also, the aerodynamic coefficients for the case of the UAV without the quad-copter is carried out analytically using MATLAB programmed codes, and the resulting data is verified using Lifting Line Theory and potential method programs. The two results are then compared to understand the effect of adding the quad-copter on the aerodynamic performance of the UAV.
Digital Article Identifier (DAI):
954
81483
Numerical Analysis of Charge Exchange in an Opposed-Piston Engine
Abstract:
The paper presents a description of geometric models, computational algorithms, and results of numerical analyses of charge exchange in a two-stroke opposed-piston engine. The research engine was a newly designed internal Diesel engine. The unit is characterized by three cylinders in which three pairs of opposed-pistons operate. The engine will generate a power output equal to 100 kW at a crankshaft rotation speed of 3800-4000 rpm. The numerical investigations were carried out using ANSYS FLUENT solver. Numerical research, in contrast to experimental research, allows us to validate project assumptions and avoid costly prototype preparation for experimental tests. This makes it possible to optimize the geometrical model in countless variants with no production costs. The geometrical model includes an intake manifold, a cylinder, and an outlet manifold. The study was conducted for a series of modifications of manifolds and intake and exhaust ports to optimize the charge exchange process in the engine. The calculations specified a swirl coefficient obtained under stationary conditions for a full opening of intake and exhaust ports as well as a CA value of 280° for all cylinders. In addition, mass flow rates were identified separately in all of the intake and exhaust ports to achieve the best possible uniformity of flow in the individual cylinders. For the models under consideration, velocity, pressure and streamline contours were generated in important cross sections. The developed models are designed primarily to minimize the flow drag through the intake and exhaust ports while the mass flow rate increases. Firstly, in order to calculate the swirl ratio [-], tangential velocity v [m/s] and then angular velocity ω [rad / s] with respect to the charge as the mean of each element were calculated. The paper contains comparative analyses of all the intake and exhaust manifolds of the designed engine. Acknowledgement: This work has been realized in the cooperation with The Construction Office of WSK "PZL-KALISZ" S.A." and is part of Grant Agreement No. POIR.01.02.00-00-0002/15 financed by the Polish National Centre for Research and Development.
Digital Article Identifier (DAI):