Littérature scientifique sur le sujet « Finite Element Anaylsis »

Purpose The Cauer ladder network (CLN) model order reduction (MOR) method is applied to an industrial inductor. This paper aims to to anaylse the influence of different meshes on the CLN method and their parameters. Design/methodology/approach The industrial inductor is simulated with the CLN method for different meshes. Meshes considering skin effect are compared with equidistant meshes. The inductor is also simulated with the eddy current finite element method (ECFEM) for frequencies 1 kHz to 1 MHz. The solution of the CLN method is compared with the ECFEM solutions for the current density in the conductor and the total impedance. Findings The increase of resistance resulting from the skin effect can be modelled with the CLN method, using a uniform mesh with elements much larger than the skin depth. Meshes taking account of the skin depth are only needed if the electromagnetic fields have to be reconstructed. Additionally, the convergence of the impedance is used to define a stopping criterion without the need for a benchmark solution. Originality/value The work shows that the CLN method can generate a network, which is capable of mimicking the increase of resistance usually accompanied by the skin effect without using a mesh that takes the skin depth into account. In addition, the proposed stopping criterion makes it possible to use the CLN method as an a priori MOR technique.

Over the years, gas turbine industry is continuously exploring different methods to increase the turbine inlet temperature for improving the specific power output and thermal efficiency of gas turbine engines, which leads to thermal loads for the engine components, which are usually managed thanks to the introduction of complex internal cooling systems. For this reason, it is necessary to develop tools able to accurately and quickly estimate thermal loads on turbine components. Typical experimental methods for assessing the heat transfer characteristics of such systems commonly rely upon scaled-up models investigated at nearly ambient conditions, since the size and operating environment of real engine parts make it extremely difficult to perform direct measurements. By doing so, however, many geometric and flow features of the real cooling system get lost, since the studied geometry is ideal and measurement constraints often require a simplification of the system itself. So there is a need for the development of a non-invasive, non-destructive, transient inverse technique which allows testing of real turbine blades temperature measurements. A much more reliable evaluation of cooling performance would thus be obtained by studying the real hardware, which requires the development of a suitable technique. As an additional advantage, a similar method could also be employed for in-line inspection of manufactured parts, as to clearly identify faults and defects before the actual installation. The aim of this work is to present the development and application of a measurement technique that allows to record internal heat transfer features of real components. In order to apply this method, based on similar approaches proposed in previous literature works, the component is initially heated up to a steady temperature, then a thermal transient is induced by injecting cool air in the internal cooling system. During this process, the external temperature evolution is recorded by means of an IR camera. Experimental data are then exploited to run a numerical procedure, based on a series of transient finite-element analyses of the component. Then two different approaches can be followed, which will be refereed as fluid model method and regression method respectively. In fluid model method at the end of transient, finite element output external surface temperature is compared to the one which is obtained with experiment and the convective internal heat transfer coefficient is iterated continually with a root finding algorithm until the convergence between them is achieved. The coolant temperature will be updated during the transient with the help of a fluid model. This approach works very well for simplified geometries, in which convective internal heat transfer coefficient converges specific value but as we move to more complex geometries it may diverge. The reason is the inability of the fluid model to find accurate coolant temperature at certain regions, so a second approach is introduced for more complex geometries, the regression which is a modification version of the first approach. In the regression method, the test duration is divided into an appropriate number of steps and for each of them, the heat flux on internal surfaces is iteratively updated to target the measured external temperature distribution at the end of step. Heat flux and internal temperature data for all the time steps are eventually employed in order to evaluate the convective heat transfer coefficient via linear regression. This technique has been successfully tested on a cooled high-pressure vane of a Baker Hughes heavy-duty gas turbine, which was realised thanks to the development of a dedicated test rig at the University of Florence, Italy. The obtained results provide sufficiently detailed heat transfer distributions in addition to allowing to appreciate the effect of different coolant mass flow rates. The methodology is also capable of identifying defects, which is demonstrated by inducing controlled faults in the component.

Abstract The Federal Railroad Administration (FRA) sponsors research on safety topics to address and to improve safety regulations and standards. This paper focuses on the latest research and testing conducted to evaluate passenger locomotive fuel tank integrity. Fuel tank integrity regulations, in the form of a series of static load conditions, currently exist to set a minimum level of protection against an impact to the fuel tank that might puncture the tank and cause the release of diesel fuel. The current research program involves a series of dynamic impact tests and quasi-static tests that measures the forces required to deform a fuel tank and investigate the types of loading conditions experienced by fuel tanks. The objective of the testing program is to establish the baseline puncture resistance of current locomotive fuel tanks under dynamic impact conditions and to develop performance requirements for an appropriate level of puncture resistance in alternative fuel tank designs, such as Diesel Multiple Unit (DMU) fuel tanks. The tests are divided into two loading scenarios identified from accidents: blunt impact and raking impact. The blunt impact scenario in the form of a full-scale dynamic impact test, have been completed on both conventional passenger locomotive fuel tanks and a DMU fuel tank. DMU fuel tank quasi-static tests, conducted in December 2018 and November 2019, are designed to simulate a raking impact scenario of a fuel tank. The Transportation Technology Center Inc. (TTCI), with support from the Volpe Center designed a test setup using a fuel tank mounted to a boxcar placed within the “squeeze frame”. An indenter, shaped like a broken rail, is fixed to the ground and the fuel tank is slowly pushed into the indenter using a series of hydraulic rams. Load cells and string potentiometers are used to measure the force/displacement. Cameras capture the deformation profile of the fuel tank. The Volpe Center develops and performs finite element analysis to evaluate the loading scenario prior to testing. The results of pre-test analyses for the raking impact tests are presented to highlight the critical position on the fuel tank to be impacted. The analysis gives an estimate of the force required to puncture the fuel tank as well as the resultant tear of the fuel tank. Additionally, finite element analysis may be used to evaluate the effect of the fuel on the fuel tank integrity. These results highlight the detailed differences of quasi-static versus dynamic loading of fuel tanks, which supports defining tradeoffs between specifying static load requirements versus scenario-defined performance based standards.