Thermal Power Plant Boiler Misoperation -Case Study Using CFD

Abstract The actual operation condition of a thermal power plant, where the water seal in the bottom of the boiler presented an air leakage, was simulated using the commercial CFD code CFX. The results were compared with the ones for the hypothetic situation where the leakage does not exist and the total amount of air required for the combustion would be furnished by the secondary air feeds. The misoperation condition affects the performance and the flow dynamics of the boiler and also the NO x formation. * Corresponding author: [email protected] European Combustion Meeting 2009. Introduction A substantial portion of the electric energy generated worldwide comes from fossil fuel sources. In addition to economic considerations, the current concerning with greenhouse effects enhances the importance of the efforts done for a proper and efficient thermal power plant operation. Coal combustion comprises phenomena such as turbulence, radiative and convective heat transfer, particle transport and chemical reactions. The study of these coupled phenomena is a challenging issue. The state of the art in computational fluid dynamics and the availability of commercial codes encourage numeric studies of the combustion processes, as The purpose of the study is the analysis of an actual operation condition where the water seal in the bottom of the boiler presented an air leakage. The amount of air leak was evaluated by the plant staff and also computed by stoichiometric balance. The results were compared with the ones for the hypothetic situation where the leakage does not exist and the total amount of air would be furnished by the secondary air feeds

Dynamic and static task allocation for hard real-time video stream decoding on NoCs

Hard real-time (HRT) video systems require admission control decisions that rely on two factors. Firstly, schedulability analysis of the data-dependent, communicating tasks within the application need to be carried out in order to guarantee timing and predictability. Secondly, the allocation of the tasks to multi-core processing elements would generate different results in the schedulability analysis. Due to the conservative nature of the state-of-the-art schedulability analysis of tasks and message lows, and the unpredictability in the application, the system resources are often under-utilised. In this paper we propose two blocking-aware dynamic task allocation techniques that exploit application and platform characteristics, in order to increase the number of simultaneous, fully schedulable, video streams handled by the system. A novel, worst-case response time aware, search-based, static hard real-time task mapper is introduced to act as an upper-baseline to the proposed techniques. Further evaluations are carried out against existing heuristic-based dynamic mappers. Improvements to the admission rates and the system utilisation under a range of different workloads and platform sizes are explored

An extensible framework for multicore response time analysis

In this paper, we introduce a multicore response time analysis (MRTA) framework, which decouples response time analysis from a reliance on context independent WCET values. Instead, the analysis formulates response times directly from the demands placed on different hardware resources. The MRTA framework is extensible to different multicore architectures, with a variety of arbitration policies for the common interconnects, and different types and arrangements of local memory. We instantiate the framework for single level local data and instruction memories (cache or scratchpads), for a variety of memory bus arbitration policies, including: Round-Robin, FIFO, Fixed-Priority, Processor-Priority, and TDMA, and account for DRAM refreshes. The MRTA framework provides a general approach to timing verification for multicore systems that is parametric in the hardware configuration and so can be used at the architectural design stage to compare the guaranteed levels of real-time performance that can be obtained with different hardware configurations. We use the framework in this way to evaluate the performance of multicore systems with a variety of different architectural components and policies. These results are then used to compose a predictable architecture, which is compared against a reference architecture designed for good average-case behaviour. This comparison shows that the predictable architecture has substantially better guaranteed real-time performance, with the precision of the analysis verified using cycle-accurate simulation

Recuperação de campos nativos suprimidos por agricultura no bioma Pampa: manejo versus regeneração natural.

Os valores médios de riqueza nas áreas de regeneração natural foram inferiores aos das áreas manejadas, e em termos de composição, áreas manejadas tiveram maior similaridade às áreas de referência, indicando que o manejo propiciou aumento na riqueza e composição de espécies em relação às áreas de exclusão, e melhor trajetória dere cuperação

Recuperação de campos nativos suprimidos no Bioma Pampa: um estudo de caso em escala de paisagem em Rosário do Sul (RS).

Uma parceria entre Exército Brasileiro, Ibama, Embrapa Pecuária Sul, Unipampa e UFRGS conduziu um Projeto de Recuperação de Área Degradada (Prad) no Campo de Instrução Barão de São Borja, em Rosário do Sul/RS, visando recuperar campos nativos com histórico de uso com lavouras de arroz e soja. A hipótese central trabalhada no Prad é de que o pastejo pode ser um instrumento para restaurar as formações campestres, impedindo que a vegetação evolua para uma fisionomia arbustiva e acelerando a regeneração natural. O gado bovino foi usado como ?roçadeira biológica? e dispersor de sementes, prática complementada por roçadas mecânicas, nivelamento do solo e isolamento temporário da área em recuperação. O monitoramento da estrutura e da riqueza da vegetação norteou o ajuste de carga animal e os períodos de diferimento. Passados cinco anos, a área apresenta fisionomia campestre desejada, tendo sido observado aumento na riqueza de espécies nativas, e composição botânica com maior similaridade à da área de referência, com aumento na cobertura de espécies das famílias Poaceae e Fabaceae. Houve diminuição do solo exposto, com o aumento da cobertura vegetal, e registrado o aumento da cobertura de Eragrostis plana (capim-annoni), gramínea exótica invasora