Claus Wahl

Comparison of laser-induced incandescence method with scanning mobility particle sizer technique: the influence of probe sampling and laser heating on soot particle size distribution

We present a simple method for comparing particle size measurements, obtained with laser-induced incandescence (LII) and a scanning mobility particle sizer (SMPS) in a premixed laminar sooting flame. A quartz cell was installed in line with the SMPS probe to allow LII measurements within the SMPS sample line. In this configuration, the LII and SMPS measurements gave similar results in terms of mean particle size. After the probe, the soot particles appear to be made of tight compact particles. In addition, with this experimental configuration, the influence of the probe in the flame is studied for different particle size ranges by applying LII before and after the probe. Application of SMPS with and without LII in the quartz cell shows that laser heating during LII measurements has an influence on the soot particle size distribution. The method could be used to improve probe sampling of particulate matter in reactive fields as well as to validate the interpretation of relevant physical mechanisms involved in the LII process.

Flame Characteristics and Emissions in Flameless Combustion Under Gas Turbine Relevant Conditions

Nomenclature d = inner diameter of the FLOX® nozzle, mm Da = Damkohler number dl = position of fuel nozzle with respect to air nozzle exit plane, mm f = focal length, mm k = rate coefficient NOx = oxides of nitrogen (NO and NO2) OH = OH chemiluminescence (electronically excited) Tad = global adiabatic flame temperature, K Tair = air preheat temperature, K v = velocity in air nozzle, ms 1 = air equivalence ratio = equivalence ratio

Aircraft Gas Turbine Soot Emission Tests Under Technical Relevant Conditions in an Altitude Test Facility and Validation of Soot Measurement Technique

An aircraft gas turbine was tested in an altitude test facility under technical relevant flight conditions. Test points are the ICAO power settings IDLE, TAKE OFF, CLIMB and DESCENT, as well as CRUISE conditions. The used measurement techniques are Scanning Mobility Particle Sizer (SMPS) [1] and Scanning Electron Microscopy (SEM). It is shown, that the relative Soot Emission Index (compared to take off conditions) is increasing with power setting. The mean diameter of the particles is also increasing with power setting. The particles show a lognormal size distribution for most of the test points. Under TAKE OFF conditions (100% power setting) we found a bimodal size distribution. The SEM pictures show the fractal character of the soot particles with 10 to 15nm primary particles as well as the agglomerates. To validate the measurement techniques a variable soot generator [2] for nanoparticles was developed. This soot generator was used to check sample line losses. In an additional experiment we used this soot generator to test the trapping efficiency of the recommended filters for the so called ICAO Smoke Number which is the same as SAE – Smoke Number [3] or EPA – Smoke Number [4].Copyright

Impact of Alternative Jet Fuels on Engine Exhaust Composition During the 2015 ECLIF Ground-Based Measurements Campaign

The application of fuels from renewable sources (alternative fuels) in aviation is important for the reduction of anthropogenic carbon dioxide emissions, but may also attribute to reduced release of particles from jet engines. The present experiment describes ground-based measurements in the framework of the ECLIF (Emission and Climate Impact of Alternative Fuels) campaign using an Airbus A320 (V2527-A5 engines) burning six fuels of chemically different composition. Two reference Jet A-1 with slightly different chemical parameters were applied and further used in combination with a Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK) to prepare three semi synthetic jet fuels (SSJF) of different aromatic content. In addition, one commercially available fully synthetic jet fuel (FSJF) featured the lowest aromatic content of the fuel selection. Neither the release of nitrogen oxide or carbon monoxide was significantly affected by the different fuel composition. The measured particle emission indices showed a reduction up to 50% (number) and 70% (mass) for two alternative jet fuels (FSJF, SSJF2) at low power settings in comparison to the reference fuels. The reduction is less pronounced at higher operating conditions but the release of particle number and particle mass is still significantly lower for the alternative fuels than for both reference fuels. The observed correlation between emitted particle mass and fuel aromatics is not strict. Here, the H/C ratio is a better indicator for soot emission.