An Annular Plate Model in Arbitrary-Lagrangian-Eulerian Description for the DLR FlexibleBodies Library

The bending deformation of rotating annular plates and the associated vibration behaviour is important in engineering applications which range from automotive or railway brake systems to discs that form essential components in turbomachinery. In order to extend the capabilities of the DLR FlexibleBodies library for such use cases, a new Modelica class has been implemented which is based on the analytical description of an annular Kirchhoff plate. In addition the so-called Arbitray Langrangian-Eulerian (ALE) representation has been adopted so that rotating and non-rotating external loads may be applied conventiently to rotating plates. Besides these particularities the new class AnnularPlate completely corresponds to the concept of FlexibleBodies library with the two already available model classes Beam and ModalBody. This paper gives an overview on the theoretical background of the new class AnnularPlate, explains the usage and presents application examples

Mathematical Modeling of the Mojave Solar Plants

Competitiveness of solar energy is one of current main research topics. Overall efficiency of solar plants can be improved by using advanced control strategies. To design and tuning properly advanced control strategies, a mathematical model of the plant is needed. The model has to fulfill two important points: (1) It has to reproduce accurately the dynamics of the real system; and (2) since the model is used to test advanced control strategies, its computational burden has to be as low as possible. This trade-off is essential to optimize the tuning process of the controller and minimize the commissioning time. In this paper, the modeling of the large-scale commercial solar trough plants Mojave Beta and Mojave Alpha is presented. These two models were used to test advanced control strategies to operate the plants.Comisión Europea OCONTSOLAR 78905

Mathematical Modeling of the Parabolic Trough Collector Field of the TCP-100 Research Plant

The 9th EUROSIM Congress on Modelling and Simulation, EUROSIM 2016 Oulu (Finlandia)There are two main drawbacks when operating solar energy systems: a) the resulting energy costs are not yet competitive and b) solar energy is not always available when needed. In order to improve the overall solar plants efficiency, advances control techniques play an important role. In order to develop efficient and robust control techniques, the use of accurate mathematical models is crucial. In this paper, the mathematical modeling of the new TCP100 parabolic trough collector (PTC) research facility at the Plataforma Solar de Almería is presented. Some simulations are shown to demonstrate the adequate behavior of the model compared to the facility design conditions.Junta de Andalucía P11-TEP-8129Unión Europea FP7-ICT-ICT-2013.3.4-611281Ministerio de Economía y Competitividadt DPI2014-56364-C2-2-

Integrated heat air and moisture modeling and simulation

An overall objective of our work is to improve building and systems performances in terms of durability, comfort and economics. In order to predict, improve and meet a certain set of performance requirements related to the indoor climate of buildings, the associated energy demand, the heating, venting and air conditioning systems and the durability of the building and its interior, simulation tools are indispensable. In the field of heat, air and moisture transport in building and systems, much progress on the modeling and simulation tools has been established. However, the use of these tools in an integrated building simulation environment is still limited. Also a lot of modeling work has been done for energy related building systems, such as solar systems, heat pump systems and heat storage systems. Often, these models focus on the systems and not on the coupled problem of building and systems. This thesis presents the development and evaluation of an integrated heat, air and moisture simulation environment for modeling and simulating dynamic heat, air and moisture processes in buildings and systems. All models are implemented in the computational software package MatLab with the use of SimuLink and Comsol. The main advantages of this approach are: First, the simulation environment is promising in solving both time and spatial related multi-scale problems. Second, the simulation environment facilitates flexible linking of models. Third, the environment is transparent, so the implementation of models is relatively easy. It offers a way to further improve the usage and exchange of already developed models of involved parties. More than 25 different heat, air and moisture related models are included in this work. Most of the models are successfully verified (by analytical solutions or by comparison with other simulation results) and/or validated (by experimental data). The use of the simulation environment regarding design problems is demonstrated with case studies. Overall is concluded that the simulation environment is capable of solving a large range of integrated heat, air and moisture problems. Furthermore, it is promising in solving current modeling problems caused by either the difference in time constants between heating venting and air conditioning components and the building response or problems caused by the lack of building simulation tools that include 2D and 3D detail simulation capabilities. The case studies presented in this thesis show that the simulation environment can be a very useful tool for solving performance-based design problems

A reduced order model for investigating the dynamics of the Gen-IV LFR coolant pool

In the control field, the study of the system dynamics is usually carried out relying on lumped-parameter or one-dimensional modelling. Even if these approaches are well suited for control purposes since they provide fast-running simulations and are easy to linearize, they may not be sufficient to deeply assess the complexity of the systems, in particular where spatial phenomena have a significant impact on dynamics. Reduced Order Methods (ROM) can offer the proper trade-off between computational cost and solution accuracy. In this work, a reduced order model for the spatial description of the Gen-IV LFR coolant pool is developed for the purpose of being employed in a control-oriented plant simulator of the ALFRED reactor. The spatial modelling of the reactor pool is based on the POD-FV-ROM procedure, previously developed with the aim of extending the literature approach based on Finite Element to the Finite Volume approximation of the Naviera-Stokes equations, and building a reduced order model capable of handling turbulent flows modelled through the RANS equations. The mentioned approach is employed to build a ROM-based component of the ALFRED simulator for the coolant pool. The possibility of varying the input variables of the model has been also undertaken. In particular, the lead velocity at the Steam Generator outlet has been considered as a parametrized boundary condition since it can be a possible control variable. The results have turned out to be very satisfactory in terms of both accuracy and computational time. As a major outcome of the ROM model, it has been proved that its behaviour is more accurate than a 0D-based model without requiring an excessive computational cost

UNIFIED MODELLING TECHNIQUE USING VHDL-AMS AND SOFTWARE COMPONENTS

International audienceThe paper deals with the dynamic modeling of mechatronic devices, which usually need detailed modeling to be described and to take into account the physical properties of the system. VHDL-AMS 1 , which is a powerful unified modeling language for mixed system, allows to describe a large range of physical systems, for their dynamic simulation. It allows to describe models of physical components and then to connect them to obtain the model of a system.. However, this language cannot support the description of some physical phenomena, such local ones, defined by numerical methods (e.g.: finite element method, special numerical integrals). When an aspect of a model cannot be described in VHDL-AMS, the paper proposes to use software components. So, the aim of the paper is to propose a generic way to extend the computation capability of VHDL-AMS, by coupling the models described in VHDL-AMS with external ones specified as software components (where VHDL-AMS fails). The approach has been applied on several applications, among them the time simulation of an electrical plunge

A Comparison of Transient Heat-Pump Cycle Simulations with Homogeneous and Heterogeneous Flow Models

This paper compares the effects of two different refrigerant flow modeling assumptions on the transient performance of vapor-compression heat pump cycles. These simulations are developed in the next-generation modeling language Modelica, which uses an acausal, equation-oriented approach to describe physical systems. The effect of the flow assumptions and specific slip ratio correlations on both the equilibrium operating point and the transient behavior of the cycle are demonstrated through these simulations. It is shown that equivalent simulations with different slip ratio correlations each have different equilibrium mass inventories, and that some aspects of the transient system behavior exhibits minor differences between the representative simulations. The effect of the software implementation on the model performance is also discussed

The Vertical Landing Vehicles Library (VLVLib): a Modelica-based approach to high-fidelity simulation and verification of GNC systems for reusable rockets

Vertical Landing (VL) Reusable Launch Vehicles (RLVs) must rely on performing and robust Guidance, Navigation and Control (GNC) algorithms, that are normally tested and verified in closed-loop high-fidelity simulators. This paper introduces the Vertical Landing Vehicles Library (VLVLib), a new Modelica-based tool for the advanced physical modeling and simulation of VL RLV dynamics. Modelica, an acausal open-source object-oriented modeling language, is exploited to produce a multibody vehicle model where multiple effects can be easily added, modified or switched in complexity. At the same time, it offers a modular modeling methodology to quickly adapt to vehicle changes or potential new features during the development process, with benefits in terms of project speed and costs. The way Modelica features are exploited is detailed throughout the paper. At its current development status, the library is able to account for, in more detail, four main effects relevant for the GNC robustness tests: (1) propellant slosh dynamics; (2) Thrust Vector Control (TVC) dynamics;(3) landing legs deployment disturbances; (4) touchdown dynamics. They are modeled and integrated so to allow an easy generation of a vehicle model that holds a prescribed fidelity level for each sub-system, and can be compiled and exported and harmoniously integrate other simulation environments (e.g. Simulink). The potential of VLVLib is demonstrated with representative examples as applied to CALLISTO reusable rocket demonstrative mission