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A designed compositional series of 22 devitrifiable glasses for sealing solid oxide fuel cell components was studied. Candidate oxides were selected on the basis of chemical compatibility with the fuel cell environment. The influence of each component on viscosity, thermal expansion, and crystallization were evaluated through systematic addition to a base composition. The most promising results were achieved within the system BaO–SrO–normalB2normalO3–Al2normalO3–Ta2normalO5–SiO2 . Additions of SrO and BaO maximize the thermal expansion of the bulk glass, achieving a coefficient of thermal expansion ranging from 10.8 to 13.9ppm∕K (200–500°C) . Devitrification of the glasses yielded similar thermal expansion coefficients ranging from 10.7 to 14.4ppm∕K . The addition of Al2normalO3 and Ta2normalO5 allows a critical sealing viscosity to be achieved at 900°C in a glass with just 6mol% of normalB2normalO3 . Five promising candidate sealing glasses have been identified.

The imaging and quantification of droplet sizes in sprays is a challenging task for optical scientists and engineers. Laser sheet dropsizing (LSDS) combines the two-dimensional information of two different optical processes, one that is proportional to the droplet volume and one that depends on the droplet surface, e.g., Mie scattering. Besides Mie scattering, here we use two-dimensional Raman scattering as the volume-dependent measurement technique. Two different calibration strategies are presented and discussed. Two-dimensional droplet size distributions in a spray have been validated in comparison with the results of point-resolved phase Doppler anemometry (PDA) measurements.

To enhance the efficiency of direct injection engines, the understanding of the combustible mixture formation after a liquid fuel spray is injected is crucial; hence, the need is readily apparent for experimental methods that allow determining characteristic parameters such as fuel/air ratio and gas temperature. The paper demonstrates the potential of the laser‐induced grating technique to determine simultaneously the local vapor phase fuel concentration and the temperature during the temporal evolution of a direct‐injected spray. The precision and the accuracy of the experimental approach and of the applied data treatment procedure were evaluated by using calibration measurements in a constant volume cell under known stationary conditions. The test measurements of fuel vapor concentration and gas temperature were carried out in an injection chamber using a high‐pressure swirl injector. Liquid propane as the main component of liquefied petroleum gas was directly injected into the chamber under flash‐boiling conditions. Injection and ambient pressure were varied, whereas fuel and ambient temperature remained constant. The measurements were performed inside the fuel jet at different distances from the injector outlet along the axis of propane injection. The results are indicative of small evaporative cooling of the gas in the jet. Copyright © 2013 John Wiley & Sons, Ltd.

Mixture formation in spray-guided direct injection spark ignition engines (SG-DISI) with late injection timing is mainly controlled by spray atomization and evaporation and strongly depends on fuel properties. The influence of fuel composition on the liquid spray structure was determined for a 12-hole solenoid injector with integral and light sheet Mie scattering as well as phase Doppler anemometry (PDA). Late injection timing in a high pressure atmosphere was simulated in an injection chamber (1.5 MPa, 293 and 673 K) to characterize the spray propagation and evaporation of alkanes with high and low volatility (n-hexane, n-heptane, n-decane) and a 3-component mixture of these alkanes with similar fuel properties like gasoline fuel. Under high chamber pressure and low ambient temperature, the spray propagation and the resulting droplet sizes are similar for all fuels. However, for n-decane, the droplet size distribution is shifted to smaller droplets and the spray appeared to be less dense because of fuel-dependent internal nozzle flow which results in a reduced injected fuel mass. In contrast, under high ambient temperature conditions for more volatile fuel components, the liquid spray length is reduced and droplet size as well as droplet momenta are decreased. Small amounts of high boiling fractions delay the evaporation and support the overall spray stability also for multicomponent mixtures which is indicated by increased spray length as well as larger droplet sizes and momenta. Moreover, the droplet size distributions and the small liquid Peclet numbers (Pe L ≈ 1) of the 3-component fuel indicate a demixing of light and heavy boiling components in the 3-component fuel under conditions which are typical for DISI strategies with late injection.

A spectral filtering approach for improving the sensitivity of two-color laser-induced incandescence measurements is proposed. The commonly used bandpass filters providing wavelength selection, and hence temperature sensitivity, are replaced by shortpass and longpass filters, respectively, allowing significantly higher signal intensities to be detected. This modification is of particular interest when nanoparticles with low emissivity, for instance, metal and metal oxide particles, are investigated. An example case in which the conventional optical components are compared with the new approach reveals an improvement by more than one order of magnitude.

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