Characterisation of Reacting Combustor Flow Field

The department’s combustor test rigs are specifically designed to investigate the formation of pollutant emissions. Thus extensive optical access without compromising the realistic combustor geometries and hence the characteristics of the flow field are the key features of the test rigs. This allows researchers as well as industrial partners to utilise several combined advanced laser measurement techniques to investigate the complex processes within the highly turbulent and reacting two phase flow.

• The “Single-Sector-Combustor” (SSC) was developed to investigate the burner near field of rich burn combustion systems for aero engine applications. Current measurement campaigns are focused on the soot formation. 
• The HBK1 can accommodate various experimental combustion chambers to address questions regarding RQL (rich-burn/quick-quench/lean-burn) or lean burn combustors as well as combustor exit conditions. The realistic combustor configuration and the extended high pressure and high temperature operation range allows detailed investigations under real engine conditions. One of the current test campaigns investigates the impact of synthetic fuel on the formation of pollutants.

With the support of the Engine Measurement Systems department the following laser optical measurement techniques are available for the characterisation of the reacting combustor flow field:

• Phase -Doppler-Anemometry (PDA) → Droplet size and velocity distribution
• Mie-scattering → Qualitative measurement of liquid fuel placement
• Particle-Image-Velocimetry (PIV) in reacting flow field
• Planar-Laser-Induced-Fluorescence (PLIF) of OH-radicals and fuel aromatics → OH-concentration, temperature distribution (for lean combustion) and distribution of gaseous fuel
• Laser-Induced-Incandescence (LII) → spatial distribution of soot concentration
• OH und CO2 chemiluminescence → heat release zones

In addition probe-based measurement techniques are used to analyse exhaust gas components (NOx, CO, CO2, O2, UHC) and with a SMPS (Scanning-Mobility-Particle-Sizer) measurement system, the size and number of soot particles with diameters from 10 nm to 1000 nm can be measured at the combustor exit.  

Dynamic pressure sensors can be installed in the wall elements of the combustor and are used to monitor thermo-acoustic pressure fluctuations within the combustion chamber. 

Investigation of pilot and main burner interaction of two lean burn combustors with focus on flow field, reaction zone and soot distribution (Meier et al., 2013)