Reversal modeling and optimal design of hyper-elastic diaphragm in space fuel tanks

Diaphragm tanks are a common type of pressurized tanks in which the diaphragm is used to separate the fuel part from the high-pressure part, compress the fuel in the tank, and reduce free space to avoid liquid fuel sloshing. The main purpose of the application of the diaphragm tanks is to ensure the continuous flow of pure fuel without the gas bubble into the spacecraft engine. In space mission, diaphragm tanks will experience a wide range of acceleration at different levels of filling. These conditions change the state of equilibrium between the volume of the gas and the fluid and move the diaphragm toward the discharge portion of the tank. As a result of this movement, the diaphragm curvature is changed and the structure collapses at rest, which is called folding. When large nonlinear folding occurs, there is potential for diaphragm damage through wear, rubbing, and excessive stress. Predicting diaphragm behavior in order to calculate a diaphragm’s susceptibility to corrosion, rupture, and surface strain is one of the major design challenges. In this study, new method is provided to analyze deformation of diaphragm tanks by using numerical techniques. Also, the investigation method is verified by using experimental methods. In this process, first a 3D numerical model is developed to investigate the inverse behavior of a hyper-elastic diaphragm by using ANSYS software and the results of the simulations are compared with the results of experimental tests in the same situation. After validation, a second case study is performed to survey the effect of reducing diaphragm thickness according to the strain energy and natural frequency behavior of the diaphragm in different fill levels. The results of this study showed that numerical simulations are capable of reconstructing diaphragm inversion properties with good accuracy. In addition, the numerical model can detect the proper thickness for the diaphragm. In the last section, algorithm and software for optimal automatic modeling of diaphragm tanks are proposed.

Paleocene metamorphism along the Pennine–Austroalpine suture constrained by U–Pb dating of titanite and rutile (Malenco, Alps)

We present in situ rutile and titanite U–Pb geochronology for three samples from the Ur breccia, which forms the boundary between the Malenco unit and the Margna nappe (Eastern Central Alps) near Pass d’Ur in southeast Switzerland. These sampled both oceanic brecciated material and a blackwall reaction zone in contact with a micaschist and serpentinized peridotite. Peak temperatures during Alpine metamorphism in these units were ~ 460 ± 30 °C. Textural observations combined with new geochronological data indicate that rutile and titanite both grew below their closure temperatures during Alpine metamorphism. We present a technique to calculate the most precise and accurate ages possible using a two-dimensional U–Pb isochron on a Wetherill concordia. Rutile from two samples gave a U–Pb isochron age of 63.0 ± 3.0 Ma. This age conflicts with previous 39Ar–40Ar data on heterogeneous amphiboles from which an age of 90–80 Ma was inferred for the high pressure part of the Alpine evolution, but is consistent with K–Ar ages and Ar–Ar ages on phengitic white mica. Titanite from three samples gave a U–Pb isochron age of 54.7 ± 4.1 Ma. This age is consistent with Rb–Sr isochron ages on mylonites along and in the footwall of the Lunghin–Mortirolo movement zone, a major boundary that separates ductile deformation in the footwall from mostly localized and brittle deformation in the hangingwall. Our ages indicate a Paleocene rather than upper Cretaceous metamorphism of the Pennine–Austroalpine boundary and permit at most ~ 15 Myr, and possibly much less, between the growth of rutile and titanite.

European Project “Supercritical Water Reactor–Fuel Qualification Test”: Results of Fuel Pin Mock-up Tests

The main target of the EURATOM FP7 project “fuel qualification test for supercritical water-cooled reactor” was to make significant progress toward the design, analysis, and licensing of a fuel assembly cooled with supercritical water (SCW) in a research reactor. Within the project, fuel pin mock-ups of a future fuel qualification test facility were designed and manufactured by Centrum Výzkumu Řež (CVR). Following that, it was decided to conduct three different types of tests considering two possible accident scenarios. Simulation of loss of external pressure was the target of Test 1. The autoclave was depressurized as fast as possible from 20 to 1 MPa by opening the close valve located behind the cooling part of the high-pressure part of the loop. Pressure inside the pin was held at a constant value of 20 MPa by pumping high-pressure water via the pin and in parallel via a separate relief valve that was connected directly to the pin using the filling pressure tube. A similar approach was chosen when the opposite case, i.e., loss of internal pressure in the pin, was simulated in Test 2A. Eventually, Test 2A was repeated with modified setup to determine the lower limit of the internal pin pressure (i.e., collapse/buckling of the pin due to external overpressure) more accurately. The presented paper summarizes the results of all three performed tests.