Ruben Di Battista, Maria Teresa Scelzo and Maria Rosaria Vetrano
Slushes are two-phase solid-liquid single-species cryogenic fluids that exhibit an increased density and a greater heat capacity with respect to the corresponding normal boiling point liquids. These promising features are of large interest for applications that exploit slush as a thermal fluid, like super magnets refrigeration, cryogenic cooling of bio-materials or air conditioning, and for aerospace systems that use slush fluids as fuel or oxidizer. Several programs in the frame of the research on Slush Hydrogen (SLH2) as a new-generation fuel for aerospace propulsion have been started in the past. This work was carried out in the framework of a VKI research activity promoted by the Predict ESA Technology Research Programme, to investigate experimentally and numerically the behavior of slush flows in a representative upper stage feeding line. In this paper, we present a simulation based on a granular two-fluid model on an isothermal solid liquid mixture (slurry) and a Nitrogen slush (SLN2) fluid flowing in a horizontal pipe. A finite-volumes discretization using the software library OpenFOAM was benchmarked against experimental and numerical literature data, to assess the accuracy of the code in predicting pressure drops along the pipe axis and solid particle distribution across the pipe diameter. Moreover, the effects of concentration and inlet velocity are investigated. We show that the numerical model fairly reproduces the literature data in terms of important aspects as the solid volume fraction distribution and the pressure drops, especially for high flow rates.
This article presents adhesive shearing test methods, focusing especially on the ASTM D5656 method. These methods will be briefly characterized and compared. The most important concerns about the D5656 method are described. With the use of ASTM D1002 and D5656 methods, the influence of adherend surface preparation on shearing properties of the bond is evaluated. Compared to sandblasting only, sandblasting followed by the FPL process (sulfochromate etching of aluminum) increased shear strength of joints by 35 % for ASTM D1002 tests and by 48% for D5656 tests. Comparing these two methods, shear strength obtained in D5656 tests is about two times higher than in D1002 tests. The cause for this phenomena is much larger adherend thickness in the D5656 method, which provides the coupons with increased stiffness. Shear modulus, calculated with 3 different calculation methods, showed differences in obtained results, which points to necessary actualization of D5656 standard.
Publication contains a description of the preparation and the implementation of a test flight of a stratospheric balloon with a mounted camera GoPro Hero3. Description includes: used equipment, its parameters, role in the success of the mission and the difficulties and limitations that the project team encountered during the preparation and implementation of the flight. The mission was attended by a team of six engineers and scientists from the Remote Sensing Division, who were also involved in the implementation of the HESOFF project. One of the main goals of the HESOFF project was to obtain aerial images on the Krotoszyńska Plate (woj. wielkopolskie) using the Unmanned Aerial Vehicle (UAV) and to carry out remote monitoring of oak stands. The primary goal of an experimental balloon flight was to check the technical operational capability and gain experience in planning and implementing this type of project. During the balloon raising, the video material was acquired in the form of a recording, which later was analyzed. On the basis of the collected information, the conclusions regarding the possibility of implementing a long endurance flight in the stratosphere, illustrating (using a multisensor platform) research surfaces of the HESOFF project were presented. The stages of implementation of the presented mission were divided into following parts: preparation of the flight with the completion of equipment and necessary documents (flight permission), proper flight realization, understood as the release of the balloon and identification of the place where the equipment landed, as well as analysis and presentation of the results.
This paper is a review of testing methods dedicated for sandwich type composite structures with honeycomb core. First, information about the composition of sandwich materials structures, their properties, types of core materials and applications in the industry is presented. Mechanical properties were compared in the case of different types of the core material. Later, tests methods needed to describe properties of those materials and normalization organizations which create them were mentioned. The testing methods were divided into two groups: mechanical and physicochemical tests. Mechanical properties are: compressive strength (two types of test), edge compressive strength, shear strength (in two directions) and tension strength (two types of test). Physicochemical properties are: material density, water migration, water absorption and thermal conductivity. Testing methods were described according to American Society for Testing and Materials (ASTM) standards. This article is based on professional literature and the author’s experience.
The paper presents simulation method and results of calculations determining behavior of helicopter and landing site loads which are generated during phase of the helicopter take-off and landing. For helicopter with whirling rotor standing on ground or touching it, the loads of landing gear depend on the parameters of helicopter movement, occurrence of wind gusts and control of pitch angle of the rotor blades. The considered model of helicopter consists of the fuselage and main transmission treated as rigid bodies connected with elastic elements. The fuselage is supported by landing gear modeled by units of spring and damping elements. The rotor blades are modeled as elastic axes with sets of lumped masses of blade segments distributed along them. The Runge-Kutta method was used to solve the equations of motion of the helicopter model. According to the Galerkin method, it was assumed that the parameters of the elastic blade motion can be treated as a combination of its bending and torsion eigen modes. For calculations, data of a hypothetical light helicopter were applied. Simulation results were presented for the cases of landing helicopter touching ground with different vertical speed and for phase of take-off including influence of rotor speed changes, wind gust and control of blade pitch. The simulation method may help to define the limits of helicopter safe operation on the landing surfaces.
The article describes 10 known programmes of practical flight training in military aviation – specialization: Multi-Mission Tactical Jet Pilot, which is the highest level of military pilot training in all types of military and civil aviation – comparable only to the level of training and experience of the pilot-instructor of the Military Aviation School. The presented comparison was developed on the basis of literature research from the point of view of, among others, an aircraft operation engineer and a pilot-instructor.
The paper presents application of Particle Image Velocimetry for determination of an airfoil’s drag coefficient in wind tunnel tests. The purpose of the study was to investigate the feasibility of using PIV as an alternative to pressure rake measurements, especially at high angles of attack. The integral momentum concept was applied for determination of fluid drag from experimental low speed wind tunnel data. The drag coefficient was calculated from velocity and pressure rake data for intermediate angles of attack from 5° to 10°. Additionally, the experimental results were compared to panel method results. After validating the procedures at low angles of attack, the drag coefficient was calculated at close to critical angles of attack. The presented study proved that PIV technique can be considered as an attractive alternative for drag coefficient determination of an airfoil.
Carbon-epoxy composite materials, due to their high strength in relation to mass, are increasingly used in the construction of aircraft structures, however, they are susceptible to a number of damages. One of the most common is delamination, which is a serious problem in the context of safe operation of such structures. As part of the TEBUK project, the Institute of Aviation has developed a methodology for forecasting the propagation of delamination. In order to validate the proposed method, an aerial structure demonstrator, modelled on the horizontal stabilizer of the I-23 Manager aircraft, was carried out. However, in order to carry out the validation, it was necessary to "simplify" the demonstrator model. The paper presents a numerical analysis conducted in order to separate from the TEBUK demonstrator model a fragment of the structure, which was used to study the delamination area, as an equivalent of the whole demonstrator. Subcomponent selection was carried out in several stages, narrowing down the analysed area covering delamination in subsequent steps and verifying the compliance of specific parameters with the same parameters obtained in a full demonstrator model. The parameters compared were: energy release rate values on the delamination front line and strain values in the delamination area. The numerical analyses presented in the paper were performed with the use of the MSC.Marc/Mentat calculation package. As a result of the analyses, a fragment of the structure was selected, which allows to significantly reduce the time and labour consumption of the production of the studied object, as well as to facilitate experimental research.
Stratospheric balloons are very important sources for space and terrestrial observation experiments in many disciplines. Instruments developed for astrophysical measurements are usually reusable. It is also possible to observe both hemispheres including observations from the polar and equatorial regions for thirty days or even longer. On the other hand the UV atmospheric transmittance window was used for the astrophysical observations less often than visible optical bands. At the end of the 2017 there are a few scientific groups working on near-UV or UV spectrographs and cameras for balloon flights.
In this paper we are discussing the possibility of ultraviolet measurement of Enceladus, an icy Saturnian moon, surface reflectance between 200 and 400 nm from the 20-50 km altitudes. At visible and near infrared optical channels Enceladus’ reflectance is very high (near 1.0). This value is consistent with a surface composed of water ice, however at some ultraviolet wavelengths Enceladus reflectance is lower than it would be expected for this type of surface. The scientific research done in the last decade was focused on H2O, NH3, and tholin particles detection on the Enceladus’ surface as a reason of low UV reflectance phenomenon. Continuous observation of Enceladus’ UV reflectance variability from stratospheric balloons may be interesting and may give us the proof of the presence of biomarkers or/and tholin particles.