1,720,989 research outputs found
Optimal Operation of Solar Tower Plants with Thermal Storage for System Design
No full textConcentrated Solar Power CSP plants are increasingly being considered for construction worldwide, in order to meet the demand for renewable power generation. The most promising technology considered today employs a central receiver, illuminated by a heliostat eld, using molten salts as working uid. A distinctive feature of these plant is the possibility of thermal energy storage, providing 15 or more hours of full power operation without solarirradiation. The state-of-the-art SAM software is often use for sizing the plant and evaluating the return on investment, assuming a straightforward and short-sighted control strategy. In this paper, a model similar to that used by SAM is developed and then used to demonstrate the potential advantages of optimal control, in a context of variable taris with higher prices during peak hours. The modelling and optimization problems are formulated with the high-level Modelica and Optimica languages, which allows to solve the problem with minimal eort. This paper is a rst step to promote the use of optimal control techniques and high-level modelling languages for the correct evaluation of the potential performance of CSP plants with thermal storage during their design phase.Kolechkina externFlight Performance and Propulsio
Dynamic modeling and validation of a precombustion CO2 capture plant for control design
Full text linkNonideal Compressible Fluid Dynamics of Dense Vapors and Supercritical Fluids
Full text linkThe gas dynamics of single-phase nonreacting fluids whose thermodynamic states are close to vapor-liquid saturation, close to the vapor-liquid critical point, or in supercritical conditions differs quantitatively and qualitatively from the textbook gas dynamics of dilute, ideal gases. Due to nonideal fluid thermodynamic properties, unconventional gas dynamic effects are possible, including nonclassical rarefaction shock waves and the nonmonotonic variation of the Mach number along steady isentropic expansions. This review provides a comprehensive theoretical framework of the fundamentals of nonideal compressible fluid dynamics (NICFD). The relation between nonideal gas dynamics and the complexity of the fluid molecules is clarified. The theoretical, numerical, and experimental tools currently employed to investigate NICFD flows and related applications are reviewed, followed by an overview of industrial processes involving NICFD, ranging from organic Rankine and supercritical CO2 cycle power systems to supercritical processes. The future challenges facing researchers in the field are briefly outlined
Discussion: “Beyond Brayton Cycle: It is Time to Change the Paradigm” (S. Can G€ulen, 2018, ASME J. Eng. Gas Turbine Power, 140(11), p. 111702)
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and Propulsio
Design, Modelling, and Control of a Waste Heat Recovery Unit for Heavy-Duty Truck Engines
Full text linkThis paper presents a feasibility study on a waste heat recovery system for heavy-duty truck engines based on organic Rankine cycle (ORC) technology. The elements of novelty of the work are: i) the proposed plant configuration, and ii) the feasibility study that encompasses the whole preliminary design workflow of the system, namely, from the thermodynamic cycle optimization and the components preliminary sizing, to dynamic modelling and the design of a PI-based control system. The conceived ORC turbogenerator employs hexamethyldisiloxane (MM) as working fluid and achieves a maximum rated mechanical power of approximately 5 kW at the design point, corresponding to a truck cruise speed and a Diesel engine power output of 85 km h-1and 100 kW respectively. Regarding the dynamic performance, the higher response time of the ORC unit compared to that of the Diesel engine makes the adoption of an advanced control system necessary. In particular, the simulation of a PI-based control system shows that it becomes impossible to prevent the thermal decomposition of the working fluid when the engine operates continuously at high power levels. This case study demonstrates the importance for automotive ORC applications of performing the investigation of dynamic performance and control design already in the early design phase
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Use of External Fluid Property Code in Modelica for Modelling of a Pre-combustion CO2 Capture Process Involving Multi-Component, Two-Phase Fluids
Full text linkDynamic modelling and validation of pre-combustion CO2 absorption based on a pilot plant at the Buggenum IGCC power station
No full textDesign methodology for flexible energy conversion systems accounting for dynamic performance
Full text linkThis article presents a methodology to help in the definition of the optimal design of power generation systems. The innovative element is the integration of requirements on dynamic performance into the system design procedure. Operational flexibility is an increasingly important specification of power systems for base- and part-load operation. Thus, it is crucial to discard, in an early phase of the design process, plant configurations which feature unacceptable dynamic performance. The test case is the preliminary design of an off-grid power plant serving an off-shore platform where one of the three gas turbines is combined with an organic Rankine cycle turbogenerator to increase the overall energy efficiency. The core of the procedure is a stationary model, capable of performing the on-design thermodynamic cycle calculation, and the design of the components of the system. The results of these simulations are used within the framework of a multi-objective optimization procedure to identify a number of equally optimal system configurations. A dynamic model of each of these systems is automatically parameterized, by inheriting its parameters values from the design model. Dynamic simulations allow then to discriminate among the initial set of solutions, thus providing the designs that also comply with dynamic requirements
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