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     LABORATORY OF THERMOFLUIDS, COMBUSTION AND ENERGY SYSTEMS


Research at the Laboratory of Thermofluids, Combustion and Energy Systems is aimed at improving knowledge in advanced fields of strategic technologies with emphasis on principles of transport and reaction phenomena. The final goals include:

  • To improve knowledge in advanced fields of strategic technologies with emphasis on turbulent mixing and combustion processes, which have the potential to optimise the environment and the rational use of energy in industry;

  • To develop and use advanced techniques for the analysis, monitoring and control of processes at laboratory and real scales.

  • To promote the exchange of knowledge in advanced technologies for the optimisation of industrial processes and energy systems
The core goal of fundamental research is the innovation of new engineering concepts and is addressed as a driving force for new technologies. It covers interdisciplinary scientific fields, such as Thermal-fluid-dynamics, Combustion and Advanced Techniques for Flow Measurements, Control Engineering, Materials Engineering, Transport and Thermophysical Properties of Materials, Electronics and Microsystems.

Application studies are conducted which benefit from most recent advances in engineering fields to integrate them in advanced functional systems. This is to be developed in close collaboration with the IST Design Studio with the objective to create new engineering products and systems.


Laboratory of Thermofluids, Combustion and Energy Systems: 2011-2012

Theme 1: Two-phase flows and heat transfer; surface microstructuring; fuids and flows for smart structures

The research program addresses the study of transport phenomena (continuum mechanics) focusing on momentum, energy, and mass transfer at fluid flow interfaces. It follows an interdisciplinary approach focusing on physical, chemical and biological properties of surfaces. New results focused on flow phenomena occurring in microfluidic devices aiming to provide insight into the background physics towards the development of new theoretical and empirical models for micro-scale flow phenomena, as well as the design of new practical systems. It is a research program combining branches of physics, mechanics, optics and fluid dynamics with material science and chemistry.

Experiments have been designed taking into consideration the specific boundary conditions of specific applications, including HCCI engines (Panão, Moreira and Durão, 2012). Experimental techniques were developed to allow characterizing the processes occurring in the region immediately adjacent to the interface between phases (Moita, Teodori and Moreira, 2012). The experiments performed included the measurement of multiphase flow quantities, such as liquid and vapor concentrations, and chemical species concentration and temperature maps with enough spatial and temporal resolution (Moita, Moreira and Roisman, 2012), using Laser Induced Fluorescence (LIF), high-speed thermography, Particle Image Velocimetry (PIV) and Phase-Doppler Interferometry (Teodori, Moita and Moreira, 2012).

Main Publications:
  • "Intermittent multijet sprays for improving mixture preparation in HCCI engines", M. R. O. Panão, A. L. N. Moreira and D. F. G. Durão, submitted to Experiments in Fluids, September 2012.
  • "Influence of surface topography in the boiling mechanisms", A. S. Moita, E. Teodori and A. L. N. Moreira, submitted to the International Journal of Heat and Fluid Flow, June 2012.
  • "Characterization of pool boiling mechanisms over micro-patterned surfaces using PIV", E. Teodori, A. S. Moita and A. L. N. Moreira, Int. J Heat and Mass Transfer (2012).
  • "Analysis of heat transfer during drop impact onto a hot dry rigid substrate". Submitted to Phys. Rev.E (waiting for final peer review), A. S. Moita, A. L. N. Moreira and I. Roisman.


Theme 2: Flame diagnostics, propagation and control; Flame acoustics The research work was centered on the analysis of the competing effects between heat- mass- and momentum transfer on the dynamics of laboratory flames for different type of fuels (solid, gaseous mixtures). It considered the development of flame diagnostic sensors. The research work has addressed the following topics:

  • Study the ignition process of blended fuels on lean mixtures: In the context of advanced control of NOx emissions, the ignition of lean flames poses a challenge because it requires a large amount of energy, which is also largely dependent on flame sensitivity to local stretch ratios (depending on Le number) and fuel mixtures (biofuel type). All together, they inhibit initial flame kernel development conditioning flame ignition. This work under progress aims to study the spark ignition process under reactive lean mixtures.

  • ThermoAcoustic Instabilities – Flame Transfer Function of impinging flames: The challenge here was to evaluate the influence of flame deformation on flame response to upcoming oscillations (due to stretch effect). Various experimental setups were used to evaluate the burning of biomass and burning gun-powder with emphasis on situations characterized by unsteady combustion (Mericia, Trindade and Fernandes, 2012; Fernandes and Leitão, 2012).

  • Chemiluminescence: The main objective of this research task has been to evaluate the extent to which the chemiluminiscence diagnostic concept can be used to monitor the oxidation of fuel blends (CH4/C3H8/H2). Although established correlations between chemiluminiscence signals and heat release and equivalence ratio exists for pure fuels, it is not certain whether a straightforward synthesis of these individual signals remain valid for practical fuel blends. The work has involved non-separable thermal and chemical effects and possible kinetic-interaction effects.

  • Development of High speed Uv-Vis spectrophotometer: Design, assembling and testing of a High speed Uv-Vis spectrophotometer to be used in the analysis of unsteady flames and fast luminiscent processes such as flame ignition (Alekseenko, Fernandes and Shtork, 2011).

  • Development of mini sound probes - Mathematical and Experimental analysis: The device studied is a pressure probe which configuration is modeled mathematically based on the low reduced frequency model, where the viscous acoustic shear layer is taken into account in the analysis of sound propagation inside capillary tubes, before being calibrated experimentally.

Main Publications:
  • J. Mericia, T. Trindade, E.C. Fernandes, Experimental Diagnostics in Thermo-Acoustic Systems, VKI LS 2011-01, Advances in aero-acoustics and thermo-acoustics, 1 volume, ISBN-13 978-2-87516-012-6
  • Edgar C. Fernandes and Ivo D. V. Leitão, Rayleigh Criterion: Theory and Experiments, VKI LS 2011-01, Advances in aero-acoustics and thermo-acoustics, 1 volume, ISBN-13 978-2-87516-012-6.
  • Alekseenko S.V., Fernandes E.C., Shtork S.I. Instability diagnostics of vortex flow in a model burner device. Scientific Bulletin of Novosibirsk State Technical University, 2011, N3, pp. 61-68 , ISSN 1814-1196

LABORATORY OF THERMOFLUIDS, COMBUSTION AND ENERGY SYSTEMS
Brief Plan of Activities for 2013-2014

The research groups involved in this Laboratory are focused in understanding the fundamental relationship between concurrent thermodynamic transports phenomena involved in energy conversion processes. Within this framework, the group is now combining efforts in developing mathematical/physical models to downsize of energy conversion systems. Flow phenomena occurring in microfluidic devices will be analysed, with and without chemical reaction, towards the development of new theoretical and empirical models for micro-scale flow phenomena, as well as on the design on new practical systems. It is a multidisciplinary research field, combining branches of physics, mechanics, optics and fluid dynamics with chemistry.

The general objective is to develop and use different tools and new approaches to support the development of energy sustainable products towards consumers, e.g. ranging from heating/cooling suppliers to medical devices.

The main topics include:

  • Study the dynamics of interfacial transport phenomena in multiphase systems with phase change. The goal is to deal with the hierarchical complexities of pool boiling, of a velocity boundary layer flow at a flat interface and of liquid flow in micro-channels with phase change. The study must address: i) The interfacial effects and transport phenomena associated with surface tension gradients caused by temperature and concentration variations on bubble interfacial shape and dynamical behavior including nucleation, bubble motion and coalescence; ii) The effects of surface topography and chemical properties (wettability) on interfacial transport phenomena during liquid nucleation boiling; and iii) To develop/built appropriate experimental techniques and/or methods to quantify the physics of dynamic interfacial transport phenomena or processes including jet-like flows, bubble interaction and spatial scale effects.

  • The Dynamics of Flame anchored in micro burners. The research work is to deal with the competing effects between heat- mass- and momentum transfer on the dynamics of small flames anchored on mini burners burning blended fuels. The work must address the following topics: i) Study the ignition process of blended fuels on lean mixtures, to study the spark ignition process under reactive lean mixtures; ii) ThermoAcoustic Instabilities – Flame Transfer Function of micro flames, to tackle the determination of the experimental acoustic flame transfer function of small conical flames followed by the flame response modeling through the G-equation; and iii) ThermoAcoustic Instabilities – Flame Transfer Function of micro flames, to evaluate the extent to which the chemiluminiscence diagnostic concept can be used to monitor the oxidation of fuel blends (CH4/C3H8/H2). Although established correlations between chemiluminiscence signals and heat release and equivalence ratio exists for pure fuels, it is not certain whether a straightforward synthesis of these individual signals, without considering various non-separable thermal and chemical effects and possible kinetic-interaction effects.

International cooperation activities and main research Projects (on-going), including with industry, include:

  • TANGO- Marie Curie Initial Training Networks (ITN) Call: FP7-PEOPLE-2012-ITN, IST as associated partner. The research in TANGO is intended to address fundamental studies on thermoacoustic instabilities in gas turbine combustion chambers.

  • Design methods for durability and operability of low emissions combustors
    Duration in months 36 Call (part) Identifier SP1-JTI-CS-2013-01, IST and UNIVERSITAT POLITECNICA DE CATALUNYA, Clean Sky proposal JTI-CS-2013-1-SAGE-06-005. Large Eddy Simulation (LES) models will be used to characterize the turbulent behaviour of the flow in the combustor under lean working conditions.

  • Towards the Security of Supply of Biomass Feedstock – Efficiency and Safety for the Bioeconomy (EFFSAF), COST project. Proposal oc-2013-1-15217.
    The use of agricultural biomass for combustion and co-firing implies an increase in the demand for robust and reliable bulk solids handling. The EFFSAF Action will focus on key areas such as flow and self-heating to provide cohesive direction on the safe storage and efficient handling of biomass.

  • Bosch Low Nox burners. This work addresses a study of a burner system from a water-heater unit focusing on the analysis of flame stability and pollutant emission as a function of power, equivalence ratio and burner geometry, towards controlling the pollutant NOx/CO emissions.

  • Noise control of Heat Pump Systems. Identification of noise sources in Heat Pump Systems. Redesign of attenuators and ventilator turbine to reduce noise emission. The work will base on experimental and numerical approach.

The activities of the Laboratory includes the organization, every two years, of the International Symposia of Applications of Laser technics to Fluid Mechanics, which has been organized in Lisbon since 1982. The next edition will be in July 2014.

Main Background Publications to support the proposed plan:

Year Publication
2012 A S Moita, E Teodori and A L N Moreira, Enhancement of pool boiling heat transfer by surface microstructuring”, Journal of Physics: Conference Series 395 (2012), doi:10.1088/17426596/395/1/012175.
2010 A L N Moreira, A S Moita and M R O Panão. Advances and Challenges in Explaining Fuel Spray Impingement: How Much of Single Droplet Impact Research is Useful?”, Progress in Energy and Combustion Science 36 (2010) 554–580.
2011 J. Mericia, T. Trindade, E.C. Fernandes, Experimental Diagnostics in Thermo-Acoustic Systems, VKI LS 2011-01, Advances in aero-acoustics and thermo-acoustics, 1 volume, ISBN-13 978-2-87516-012-6
2011 Edgar C. Fernandes and Ivo D. V. Leitão, Rayleigh Criterion: Theory and Experiments, VKI LS 2011-01, Advances in aero-acoustics and thermo-acoustics, 1 volume, ISBN-13 978-2-87516-012-6



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