The generation of resonant turbulence for a premixed burner

Is it possible to optimize the turbulent combustion of a low swirl burner by using resonance in turbulence? To that end an active grid is constructed that consists of two perforated disks of which one is rotating, creating a system of pulsating jets, which in the end can be used as a central blocking grid of a low swirl burner. The turbulence originating from this grid is studied by hot wire anemometry to see if there is a frequency for maximal response. Although no resonant enhancement of the turbulent kinetic energy or the dissipation rate is observed, the results for the two different sets of disks show that significant turbulent fluctuations are introduced mainly in the energy containing range and partially in the inertial sub range. These fluctuations represent up to 25% of the total turbulent energy and are not caused by pulsations of the mean flow

Combined stability and electro-magnetic transients simulation of offshore wind power connected through multi-terminal VSC-HVDC

Offshore wind energy has a high potential especially in Northern-Europe. Future wind power plants may be situated further from the shore and therefore a high-voltage direct current connection based on voltage sourced converters is most suitable for grid integration. Connection utilization can be improved by interconnecting several wind power plants leading to multiterminal schemes. This paper describes a modeling approach that facilitates the incorporation of such (offshore) dc-systems into transient stability simulations. It enables the possibility to use a different simulation approach for each side of the converters, i.e. to represent the acside by complex phasors and the dc-side by electro-magnetic transients. Coupling between the ac and dc-sides is obtained by the active power balance. To study the interaction between the multi-terminal scheme and the onshore network an illustrative test-network has been taken. A chopper-controlled braking resistor that protects the dc-circuit against overvoltages has been included and is expressed as a variable resistance. Methods to distribute the wind power among the onshore converters are explored and operation without a supervisory dispatch controller has been studied

Application of Fractal Grids in Industrial Low-Swirl combustion

Fractal-grid-generated turbulence is a successful technique to significantly increase the reaction rate in the center of a low-swirl flame. Previous results (Verbeek et al. Combust. Flame 162(1), 129–143, 2015) are promising, but the experiments are only performed using natural gas at a single equivalence ratio and flow rate. In industry, the need arises to adapt gas turbines to a wider range of fuels, such as biogas and syngas. To simulate these other fuels, natural gas is enriched with up to 30 % hydrogen (molar based). By means of planar OH-LIF, the turbulent flame speed is assessed. It is shown that the beneficial effect of fractal-grid-generated turbulence remains upon hydrogen enrichment. The fractal grids enhance the combustion in an energy efficient way, irrespective of the hydrogen fraction. Moreover, the characteristic linear relation of the normalized local consumption speed versus the normalized rms velocity holds for the investigated range, with an increasing coefficient upon hydrogen enrichment. For industry, a wide operability range is essential to operate at part load, therefore the lean stability limit is investigated, as well. It is shown that fractal grids increase the lean stability limit, i.e., the adiabatic flame temperature at which blow off occurs, by 50 K, compared to a standard grid. Increasing the bulk flow significantly increases the lean stability limit and the difference between the two investigated grid types increases upon hydrogen enrichment. Hydrogen addition results in a decrease in the lean stability limit, regardless of the grid. A positive correlation was found between the adiabatic flame temperature at blow-off and the rms velocity at the flame brush. The outcome of the presented study provides, despite a slightly increased lean stability limit, a promising prospect for the application of fractal grids in industrial low-swirl combustion

Ontwerp van een interventie om de groenteconsumptie van jongeren te verhogen

In dit rapport zullen verschillende mogelijke strategieën besproken worden die ingezet kunnen worden om de consumptie van groenten door jongeren te verhogen. De centrale vragen van dit onderzoek zijn: 1) Hoe kunnen groenten in het eetpatroon van jongeren een vaste plek van voldoende omvang krijgen? 2) Hoe kunnen groenten concurreren met minder gezonde voedingsproducten dan waar nu voor gekozen wordt? Eerst zullen de bevindingen die van belang zijn voor het opzetten van interventies besproken worden. Deze bevindingen komen voort uit literatuur, voorafgaand onderzoek en enkele recent (afgeronde) andere projecten

Wat gaan we eten? Groente! Kwantitatief onderzoek onder jongeren tussen de 12 en 18 jaar.

In 2009 a survey was conducted among a representative sample of around 500 young people between the ages of 12 and 18 in the Netherlands. The first section examined the eating patterns of the young people and their attitude towards nutrition. The second section examined their vegetable consumption and how they experience vegetables, as well as the factors which influence this. The final section consisted of a choosing experiment, in which the participants were asked to choose from among two or three vegetable products and evaluate them on the basis of a number of product characteristics

Risk-Responsive Orbitofrontal Neurons Track Acquired Salience

SummaryDecision making is impacted by uncertainty and risk (i.e., variance). Activity in the orbitofrontal cortex, an area implicated in decision making, covaries with these quantities. However, this activity could reflect the heightened salience of situations in which multiple outcomes—reward and reward omission—are expected. To resolve these accounts, rats were trained to respond to cues predicting 100%, 67%, 33%, or 0% reward. Consistent with prior reports, some orbitofrontal neurons fired differently in anticipation of uncertain (33% and 67%) versus certain (100% and 0%) reward. However, over 90% of these neurons also fired differently prior to 100% versus 0% reward (or baseline) or prior to 33% versus 67% reward. These responses are inconsistent with risk but fit well with the representation of acquired salience linked to the sum of cue-outcome and cue-no-outcome associative strengths. These results expand our understanding of how the orbitofrontal cortex might regulate learning and behavior.Video Abstrac

Wat gaan we eten? Groente! Design workshops

In two independent workshops with Food and Product designers, the social environment and the behaviour and attitude of 12-18 year olds with respect to vegetable consumption has been investigated and a start is made to develop products specifically targeted to this group