 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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- Transient state flow and heat transfer performance over the flat tip of HP
turbine-
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Abstract: Abstract To study the flow and heat transfer performance over the flat tip of high pressure (HP) turbine under transient conditions more accurately, a dynamic boundary condition model from one stable operating state to another stable operating state is established. The changes of model include inlet total temperature, inlet total pressure, inlet flow angle, and tip clearance. Furthermore, the steady-state solution is performed at the typical moments of the transient state, to study the feasibility of steady state replacing transient state performance. The results show that the heat transfer performance of the blade tip under transient conditions mainly focus on the pressure side. The separation vortex formed at the edge of the pressure side significantly affects the distribution of the heat transfer coefficient. The flow and heat transfer performance obtained under steady-state conditions are close to those under transient conditions. The maximum deviation of heat transfer coefficient and total pressure recovery coefficient at each typical moment does not exceed 0.1%.
PubDate: 2023-09-12
- Integrity performance characterization of BeiDou B1C and B2a
signal-in-space error-
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Abstract: Abstract Global Navigation Satellite System (GNSS) Signal-In-Space (SIS) quality directly affects positioning integrity, which is an important metric for safety–critical applications. BeiDou Global Navigation Satellite System (BDS-3) broadcasts two new signals interoperable with GPS and Galileo, i.e., B1C and B2a. They are expected to serve civil aviation applications, following the Standards and Recommended Practices (SARPs) released by International Civil Aviation Organization (ICAO). Therefore, the SIS accuracy and integrity performance of BDS-3 B1C and B2a are evaluated in this work. The SIS Range Errors (SISREs) are achieved by comparing the broadcast satellite positions and clock offsets derived from Civil Navigation Message (CNAV) with the precise products from International GNSS Service (IGS). Specifically, given that the IGS precise products are referring to the equivalent phase center of BeiDou Regional System (BDS-2) B1I + B3I ionosphere-free combination, Differential Code Bias (DCB) from IGS is applied to realize time synchronization. This synchronization method is also meaningful to different frequencies in other constellations and supports the en-route, approaching, and landing phases. By analyzing 1-year data, an overall SIS characteristic picture of the 18 BDS-3 MEO satellites is presented here. The results show that most BDS-3 satellites are subject to an overbounding User Range Accuracy (URA) of 0.5 m to 0.85 m and a fault probability of \(1.4953\times {10}^{-5}\) to \(1.1975\times {10}^{-4}\) , with an integrity performance much better than that of BDS-2 and comparable to that of GPS. BDS-3 is now ready to serve civil aviation and other safety–critical applications.
PubDate: 2023-09-11
- Methodology for determining the takeoff mass of all-electric aircraft at
the early stages of design-
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Abstract: Abstract The paper presents the results of the development of the takeoff mass technique for all-electric aircraft (AEA) at the early stages of design. The process of determining the relative mass of aircraft batteries is described. The technique was verified by comparing the values obtained from the developed expressions with the values of existing AEA. A method for determining the mass of the AEA power plant was developed and described. General recommendations are given on the application of the obtained expressions for the design of AEA.
PubDate: 2023-09-08
- Conceptual design for returning KITSAT-1
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Abstract: Abstract The increasing number of orbiting satellites has motivated the development of active debris removal and on-orbit servicing missions. The KAIST Satellite Technology and Research Center plans to capture and de-orbit Korea’s first satellite, KITSAT-1, as one of the active debris removal missions. For the success of the project, mission planning for orbit transfer and rendezvous should be performed under consideration of the feasibility of required fuel. In this conceptual study, we designed a trajectory that could capture KITSAT-1 with a small satellite under 200 kg. The results was that the final relative RIC distance and the distance rate to KITSAT-1 are less than 0.01 km and 0.01 m/s order, and the required fuel mass was about 76 kg, which is feasible for a small capture satellite.
PubDate: 2023-09-04
- The generalization of classical porkchop plot into 3D porkchop plot
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Abstract: Abstract The porkchop plot is the porkchop-shaped, computer-generated contour plot that displays the launch date and arrival date characteristics of an interplanetary flight path for a given launch opportunity between two celestial bodies. We found that, when the gravity assistance of a planet is taken into account of an interplanetary transfer trajectory, the classical porkchop plot cannot give enough information for the interplanetary mission. In this regard, we have generalized the classical porkchop plot into the 3D porkchop plot that gives the launch, flyby, and arrival opportunity of the interplanetary mission. This paper presents an alternative opportunity for the Psyche asteroid mission with Mars’s gravity assist. Psyche is a largest M-type asteroid in the solar system and may be a good source of Platinum group metals. This paper also presents the analytical solution of the gravity assist model, which is useful for obtaining the optimal flyby radius and the optimal thrust impulse during the planetary gravity assist.
PubDate: 2023-09-01
- Numerical research on ice shape distribution characteristics of aircraft
under uncertain icing conditions-
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Abstract: Abstract Experiment and numerical simulations are important tools for studying aircraft icing and evaluating the critical icing state. However, there are uncertainties in the inflow condition, which may originate from measurement equipment, the calibration method, and the atmosphere condition. Current methods do not consider the huge uncertainties in natural icing conditions. In common industrial and research practices, the mean flow state is used to predict the icing state. Whether the inflow uncertainty is negligible' A quantitative study on the effect of uncertainties of the inflow parameters on the icing shape is carried out, with an uncertainty of the inflow parameters standard error range (± 10%). The results show that the uncertainty of ice shape varies linearly with the uncertainty of inflow parameters for the condition of rime ice. The calculations show that when LWC ≥ 1.2 g/m3 or MVD ≥ 40 μm, it is a glaze ice state. As a result, the increase rate of the uncertainty of ice shape will suddenly increase by 2–13 times and stay stable. For this case, a 10% uncertainty of incoming parameters could lead to up to 28% error in ice height. In general, uncertainties should be taken into account for glaze ice. For rime ice, the uncertainty of incoming can be averaged. In the case of an icing wind tunnel, the error of glaze ice height, resulting from inflow uncertainty, could exceed the error expected.
PubDate: 2023-09-01
- Derivation and exploration of permeability function for contact of
wedge-shaped edge of metal seal with flange-
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Abstract: Abstract Arbitrary flange connection with metal seal, which has one or more wedge-shaped edges in its construction, is estimated in the article irrespectively of construction of flange connection and its parts. Raised question is about obtaining a method for choosing the optimal wedge angle according to the criterion of minimal leak of the sealed substance through the contact of the wedge-shaped edge of the seal with the flange. The scientific problem is solved by means of derivation and exploration of the permeability function of the contact of the wedge-shaped edge of the seal with the flange a function, showing the dependence of the leak of the sealed substance in conditional flow units on the angle of the wedge-shaped edge. Results of the research make it possible to increase the tightness of flange connections, mentioned before, without increasing of tightening force, and, as a result, without increasing of the mass of flange connection, and this is especially important in modern flying vehicles.
PubDate: 2023-09-01
- Novel empirical models for estimating aerodynamic coefficients of small
UAV propellers-
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Abstract: Abstract Designers of small UAVs are often faced with a hurdle in the propeller selection stage in preliminary design due to the lack of simple yet accurate models to estimate small propellers’ performance (thrust coefficient, power coefficient, and efficiency variation with advance ratio). It might even seem impossible to have accurate propeller performance models as the performance depends on the propeller geometry, and small propellers have complex geometries that are not readily available. Nonetheless, by analyzing the performance data of over 170 propellers (diameters ranging from 2 to 18 inches) from different manufacturers, we show that: (a) the thrust and power coefficient curves can be approximated as second and third-order polynomials in advance ratio, respectively, and (b) the coefficients of these polynomials depend predominantly on the pitch ratio. Leveraging this observation, we develop novel empirical relations that determine the coefficients of the polynomial performance curves as functions of the propeller pitch ratio alone. The efficacy of the proposed performance estimation models is demonstrated by accurately predicting the performance curves of several propellers that were not used to construct the empirical relations. Further, using the developed empirical relations, we propose a method to select a suitable propeller that provides high efficiency for a given set of preliminary UAV design parameters like the required thrust and operating velocity.
PubDate: 2023-09-01
- Prediction noise of propeller on wing for distributed electric propulsion
configuration-
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Abstract: Abstract This paper presents a fast way to predict the noise level of installed propeller on wing. Installing the propeller on wing has not only increased wing lift coefficient, but also greatly changed the noise direction. However, the precise prediction of noise level is a difficult and cumbersome, since the aerodynamic interaction effects are so complicated. But with a series of simplicity, here still can get a concise formulation, which is sufficient to evaluate the noise level of early design of propeller-driven aircraft.
PubDate: 2023-09-01
- A comparison between filtering approach and spline approximation method in
smoothing flight data-
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Abstract: Abstract Onboard measurement system, the function of which is to collect, record and process measurement information, performs these tasks by obtaining information from the sensors. However, the sensors are noisy, so it is necessary to combine multiple pieces of information to give a good accuracy to the signals provided by the onboard measurement system. The extended Kalman filter, which is one of the most widely used data fusion methods, is also one of the derivatives of the standard Kalman filter used for non-linear problems. On the other hand, the spline approximation, especially the cubic and Hermitian splines provide a very good and smooth estimate. It is known that the implementation of spline method is simpler than Kalman filtering. This paper describes an empirical comparative analysis of the extended Kalman filter and spline method. The impressive result is that a simple spline approximation in many cases performs better than a sophisticated Kalman filter.
PubDate: 2023-09-01
- Investigation into the failure of aircraft stringer–skin composite
structure under bending load-
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Abstract: Abstract The progressive failure in the top-hat stiffened composite panel under four-point bending damage was analyzed. The cohesive element was applied to simulate the debonding between the fuselage skin and stringer. In addition, the quadratic stress criterion and B–K criterion were adopted to predict initiation and propagation of the debondings. The propagation process, failure mode and ultimate load of the stiffened composite panel under four-point bending were predicted and compared with the test results. Specimens with co-bonded and co-cured processes were considered in this study. In regard to the co-bonded specimens, there existed only delamination between skin and stringer. The error between the predicted and experimental results of debonding load was about 2–8.8%. In terms of the co-cured specimens, the debonding between skin and stringer and the intra-layer cracks both can be observed.
PubDate: 2023-09-01
- Determination of minimum thickness of composite panels taking into account
limits on stability and fatigue under postbuckling behavior-
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Abstract: Abstract When designing the compressed thin composite skin of a multispar flap box of a small aircraft, its buckling due to compressive forces at loads below the operational level is admissible. This work considers smooth orthotropic rectangular panels loaded with longitudinal compressive strength. To determine the optimal parameters of the panels, a method based on a postbuckling state involving an analytical solution of geometrically nonlinear problems obtained by the Bubnov–Galerkin method was used. In this paper, methods for determining the minimum thickness of orthotropic panels, for which supercritical behavior is permissible when subjected to compressive forces, are developed. They include, firstly, the approaches using various strength criteria given the static loading, secondly, methods allowing for the variation of the width of the panel when considering two levels of loading: ensuring limitations of buckling at the first level of loading and static strength conditions in the case of geometrically nonlinear behavior at the second level of loading, and thirdly, methods taking into account the requirements of fatigue cycling. Here, also two levels of loading may be considered, at which stability and strength are ensured under postbuckling behavior, according to the parameters of fatigue loading and permissible stresses with respect to fatigue strength. These methods are reduced to solving analytical ratios with respect to the thickness shown on the example of hinge-supported composite panels. Since the obtained analytical relations are associated with the initial stage of postbuckling behavior, the paper provides an expression for compressive forces, at which the number of half-waves can be increased under geometrically nonlinear behavior. Of practical significance is the possibility of determining the optimal parameters of smooth orthotropic panels under static and fatigue loading at the early stages of design.
PubDate: 2023-09-01
- Forecasting of maintenance indicators of complex technical systems during
storage-
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Abstract: Abstract Design, production, testing, and operation of reusable launch vehicles are promising areas of development and theoretical research in the field of systems for the maintenance, repair, restoration, and operation of aircraft, including reusable transport rocket and space systems, are relevant. The article is aimed at harmonizing the design solutions of technical systems related to measures for their maintenance during storage. The purpose of the article is to develop methods and algorithms that allow matching performance characteristics and design solutions. The scientific problem is solved by compiling and analyzing the state graph of maintenance models using the Kolmogorov system of differential equations. As a result, the models obtained make it possible to predict the performance of maintenance of complex technical systems during storage and explore the possibility of reducing downtime for maintenance without a significant decrease in the quality of maintenance, namely: to evaluate the optimal maintenance period, to agree on the reserve ratio and maintenance period (costs maintenance depending on the ratio of the reserve), choose the optimal strategy for scheduled maintenance, taking into account the continuous monitoring of the technical condition of the aircraft, evaluate the intensity of failure recovery during continuous and periodic monitoring, and justify the most appropriate ways to improve the quality of service, provided that downtime for maintenance is limited and predict the probability of detecting faults during maintenance.
PubDate: 2023-09-01
- Fatigue life of engineering structures with regard to aerospace welding
joint-
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Abstract: Abstract A methodology and results of fatigue life assessment of a structure containing continuous welding joint under random kinematic loading taking into account the influence of residual welding stresses have been presented. Realizations of random stress processes in the welding joint area and dependences for amplitude repeatability of reduced regular stress cycles have been constructed on the basis of numerical simulation. Characteristics of durability of the structure by two theories of accumulation of fatigue damages have been determined. Significant influence of residual welding stress levels on durability is shown.
PubDate: 2023-09-01
- Trajectory planning with minimum energy consumption for multi-target
regions autonomous cruise of stratospheric airship in wind field-
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Abstract: Abstract In the future, the stratospheric airship will be used to accomplish the continuous cruising mission in the widely distributed area. To solve the trajectory planning problem of a single airship continuously cruising multi-target regions, a global trajectory planning algorithm with the minimum energy consumption is proposed under the assumption of constant horizontal wind and cruising altitude. First, the singular perturbation method is used to plan the trajectory of the airship with minimum energy consumption in the long-distance straight cruise phase between each two target regions. This method determines the optimal yaw angle and cruising speed of the airship. Then, quadratic programming is used to solve the trajectory of the airship cruising in the target region by considering the smoothness and continuity of the airship's flight, the requirements of cruising time, and the constraints of speed and acceleration. Finally, the trajectory is optimized by considering the yaw rate constraint to strengthen the dynamic feasibility. Based on the above algorithms, we give a specific trajectory planning case in the last section.
PubDate: 2023-09-01
- Research on reliability of aero-engine nacelle based on survival analysis
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Abstract: Abstract This paper studies the reliability modeling of civil aircraft engine nacelles. Based on the fault record data of an aircraft over the years, the two-parameter Weibull model and the Cox proportional hazards model are used respectively. On MATLAB and SPSS software, reliability modeling was carried out for several important equipment of this type of aircraft. And it was tested in the fault prediction to verify the feasibility of the model and prediction method.
PubDate: 2023-09-01
- Thermal–mechanical properties of aluminum cylindrical sandwich
structures with foldcores-
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Abstract: Abstract Nowadays sandwich structures with foldcores have extensive applications in aviation and aerospace fields, which are considered better than honeycomb sandwich structures to some extent. This paper explores the thermal–mechanical properties of cylindrical sandwich structures (CSS) with four kinds of foldcores, including Axial Miura, Circumferential Miura, Diamond, and Kresling foldcores. Sequential coupled thermal stress simulation and axial compression simulation with ABAQUS are implemented to aluminum CSS with the four kinds of foldcores, which are subjected to mono-direction heat flux. Moreover, the simulation results are compared with that of CSS with honeycomb core, and compared the thermal mechanical properties of different structures and different \(N\) (the number of unit cell in one circle). It is found that with the increase of \(N\) , the thermal mechanical properties of CSS with Axial and Circumferential Miura foldcores become better. Besides, CSS with multi-layered foldcores exhibit more uniform temperature distribution, which is favored in design of satellite. In addition, the strength and the stiffness of CSS increase as \(N\) increases and are lower with mono-direction heat flux than without heat flux. Especially, CSS with two-layered Axial Miura foldcores exhibit better thermal–mechanical properties than all the other models.
PubDate: 2023-09-01
- Numerical study of fatigue damage accumulation in composite wing panels of
prospective supersonic transport aircraft-
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Abstract: Abstract In this paper, the patterns of fatigue damage accumulation for a stringer panel and a panel with lattice reinforcement made of a polymer composite material (PCM) were studied using the Wim Van Paepegem calculation method. Both panels have the same overall dimensions, are made of the same material and are designed to carry the same compressive load. Based on the results of the calculations, the zones were determined in which the greatest loss of stiffness occurs in one of the components for both types of panels. The number of cycles to complete loss of stiffness for these components for each of the zones was obtained. It was found that in the stringer panel, the greatest loss of stiffness occurs in the layers of the stringer web and in the panel with lattice reinforcement in the zone where the diagonal ribs intersect. At the same time, it was found that in a lattice panel, these fatigue damage occurs under a smaller number of applied cycles than in a stringer panel.
PubDate: 2023-09-01
- Numerical research on near stall characteristics of a transonic axial
compressor based on wavelet analysis-
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Abstract: Abstract An axial single-stage high-speed test rig is numerically studied in this paper with half-annulus URANS simulations to describe the flow characteristics at the near stall condition. Wavelet analysis is applied to demonstrate the time–frequency characteristics of the near-tip pressure signals captured by the numerical probes at different circumferential and axial positions. The detailed tip flow fields and wavelet transform results are combined to depict the generation and propagation of the spike-type stall inception. According to the wavelet spectrum, characteristic frequencies correspond to the temporal and spatial features of the rotating stall, such as the fluctuation of the shock wave, self-oscillation and propagation of tip leakage vortex et al. Consequently, the detection of typical spike stall inception can be significantly brought forward by identifying the crucial rotating disturbance and its development for the onset of stall inception. Then, the specific tip flow fields are also discussed to reveal the flow mechanism of stall inception evolution, including the leading edge spillage and the trailing edge backflow. Further investigation shows that the stall inception with smooth casing corresponds to the radial separation vortex caused by the tip leading edge spillage, which continues to develop and propagate in the circumferential direction and finally induces the stall.
PubDate: 2023-08-28
- A new coupling model of dynamics and thermodynamics to predict trajectory
of stratospheric airship during ascent-
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Abstract: Abstract Predicting the trajectory of the airship during its ascent before it is released has significance in avoiding possible accidents. To achieve this, a new coupled thermodynamics and dynamics model is developed. A rigid body model with 6 degrees of freedom is adopted. Time-varying aerodynamic forces and mass distribution parameters are also included in this model. The thermodynamic model considers the heat transfer process of radiation and convection among the film of airship, helium, internal air, and atmosphere. The simulation results show that more accurate results can be obtained using the rigid body model with six degrees of freedom compared with the three degrees of freedom model. The existence of the sunlight will also affect the movement of the airship, which will cause the temperature of the buoyant gas to increase and the airship to move faster. Some factors which will affect thermal behavior of helium are also investigated. Results show that the larger the initial helium volume is, the more serious the supercooling phenomenon of helium will happen. The greater the solar radiation absorptivity of the film is, the lower the supercooling temperature will be, but it will cause helium more hotter during floating stage. The overpressure of the airbag has no significant effect on the motion of the airship.
PubDate: 2023-06-14
DOI: 10.1007/s42401-023-00227-4
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