dependence of the rate of oxidation of unit mass of char on 1/@ and the relatively small influence of temperature on these rates. Particles of char from sewage sludge are so reactive that it is essential to make allowance for a difference in temperature between the particle and the bed. Thus, experimental determinations on particles with dp ~ 6.5 mm, suggested a difference in temperature of ~150 K, in line with cal- culations using a steady-state heat balance.

05•02250 Tracer-LIF diagnostics: quantitative measurement of fuel concentration, temperature and fuel/air ratio in practical combustion systems Schulz, C. and Sick, V. Progress in Energy and Combustion Science, 2005, 31,(1), 75 121. The safe, clean, and reliable operation of combustion devices depends to a large degree on the exact control of the fuel/air mixing process prior to ignition. Therefore, quantitative measurement techniques that characterize the state of the fresh gas mixture are crucial in modern combustion science and engineering. This paper presents the funda- mental concepts for how to devise and apply quantitative measurement techniques for studies of fuel concentration, temperature, and fuel/air ratio in practical combustion systems, with some emphasis on internal combustion engines. The paper does not attempt to provide a full literature review of quantitative imaging diagnostics for practical combustion devices; rather it focuses on explaining the concepts and illustrating these with selected examples. These examples focus on application to primarily gaseous situations. The photophysics of organic molecules is presented in an overview followed by discussions on specific details of the temperature-, pressure-, and mixture- dependence of the laser-induced fluorescence strength of aliphatic ketones, like acetone and 3-pentanone, and toluene. Models that describe the fluorescence are discussed and evaluated with respect to their functionality. Examples for quantitative applications are categor- ized in order of increased complexity. These examples include simple mixing experiments under isothermal and isobaric conditions, fuel/air mixing in engines, temperature measurements, and mixing studies where fuel and oxygen concentrations vary. A brief summary is given on measurements of fuel concentrations in multiphase systems, such as laser-induced exciplex spectroscopy. Potentially adverse effects that added tracers might have on mixture formation, combustion, and the faithful representation of the base fuel distribution are discussed. Finally, a brief section describes alternative techniques to tracer-based measurements that allow studies of fuel/air mixing processes in practical devices. The paper concludes with a section that addresses key issues that remain as challenges for continued research towards the improvement of quantitative, tracer-based ElF measurements.

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Power generation and propulsion, electrical vehicles

05•02251 A continuous efficiency optimization controller for induction motor drives Vaez-Zadeh, S. and Hendi, F. Energy Conversion and Management, 2005, 46, (5), 701 713. In this paper, an on-line efficiency optimization controller is proposed for induction motor drives after a detailed analysis of motor losses. The controller searches for a minimum motor drive input power by continuous variation of a control variable, resulting in a smooth system performance, which is not possible by the conventional stepwise change of the control variable. The search period is short. Thus, the controller can be applied effectively to applications with frequent changes of speed and load. Also, under the proposed controller, more energy saving is achieved. Extensive simulation is performed for the induction motor under the proposed and conventional efficiency optimization controllers. The results prove the superiority of the proposed controller.

05•02252 A KIVA code with Reynolds-stress model for engine flow simulation Yang, S. L. et al. Energy, 2005, 30, (2 4), 427 445. To properly simulate the highly anisotropic turbulent engine flows, higher order turbulence model should be used to correctly reproduce flow physics inside the engine. The popular KIVA computer code has been modified to include the Reynolds-stress turbulence model

10 Engines (power generation and propulsion, electrical vehicles)

(RSTM) for this purpose. The objective of this paper is to present this recent research on the use of RSTM and the KIVA code for engine flow simulation, which include gas turbine combustors and IC engines.

05•02253 A sensorless variable structure control of induction motor drives Barambones, O. and Garrido, A. J. Electric Power Systems Research, 2004, 72, (1), 21 32. In this paper, an indirect field-oriented induction motor drive with a sliding-mode controller is presented. The design includes rotor speed estimation from measured stator terminal voltages and currents. The estimated speed is used as feedback in an indirect vector control system achieving the speed control without the use of shaft mounted transducers. Stability analysis based on Lyapunov theory is also presented, to guarantee the closed loop stability. The high performance of the proposed control scheme under load disturbances and parameter uncertainties is also demonstrated via simulation examples.

05•02254 A very fast direct torque control for interior permanent magnet synchronous motors start up Ghassemi, H. and Vaez-Zadeh, S. Energy Conversion and Management, 2005, 46, (5), 715 726. Selection of the stator flux command in direct torque control (DTC) of permanent magnet synchronous motors is very important as it affects machine performance. For steady state operation, it can help to decrease the stator current or machine losses. However, in order to get a fast torque response during motor start up, one needs to change both the stator flux angle and magnitude. In this paper, a method is presented to find the optimal voltage vectors to change both the flux angle and its magnitude that results in high speed dynamics for the torque response. The closed form formula given for the optimal voltage vector is derived based on maximizing the torque change in each sampling time. The simulation results show that the presented method is superior to the conventional DTC. In other words, it is shown that the voltage vectors derived from the switching table for conventional DTC are not the optimal voltage vectors for the situation in which there is a step change in the torque command.

05•02255 An analysis of the effects of heat exchange and heat refluxing in the generation of electricity with a gas turbine Beaver, S. et al. Energy, 2005, 30, (2 4), 103 110. Six incremental but accumulative thermal schemes to improve the operation of a natural-gas-fired turbine in conjunction with a single steam turbine were analysed in detail. Each of these was found to improve the efficiency and increase the electrical output, and to be justified economically on the basis of fixed and operating costs. The best overall scheme from a combined economic and thermodynamic point of view consisted of steam inputs to the turbine at three different pressure levels and the use of 13 separate heat exchanger sections (four pre-heaters, three evaporators, and six super-heaters). The overall efficiency based on the lower heating value of the natural gas was increased from 37.9% to 57.4% and the electrical output from 220 to 340 MW as compared to the bare gas turbine exhausting to the atmosphere. Further incremental improvements were found to be possible technically but not advisable economically because of the diminishing return per unit of expenditure.

05•02256 Analysis and optimization of a solid oxide fuel cell and intercooled gas turbine (SOFC-ICGT) hybrid cycle Yi, Y. et al. Journal of Power Sources, 2004, 131, (1 2), 77 85. The power generation community faces a major challenge: to protect the environment while producing a plentiful supply of clean low-cost energy. '21st Century Energy Plants' (Vision 21 Plants) have been proposed and conceptualized to meet the energy and environmental challenges. The solid oxide fuel cell and intercooled gas turbine (SOFC ICGT) hybrid cycle introduced in this work is one example of a Vision 21 Plant. The system includes an internal-reforming tubular- SOFC, an intercooled gas turbine, a humidifier, and other auxiliary components. A recently developed thermodynamic analysis computer code entitled advanced power systems analyses tools (APSAT) was applied to analyse the system performance of the SOFC ICGT cycle. Sensitivity analyses of several major system parameters were studied to identify the key development needs and design and operating improvements for this hybrid cycle. A novel optimization strategy including a design of experiments (DOEx) approach is proposed and applied to the hybrid system. Using this optimization strategy, a system electrical efficiency higher than 75% (net ac/lower heating value (LHV)) could be achieved when the system was designed to operate under a high operating pressure (50 bars) and with a low percent excess air (EA) (55%) in the SOFC.

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