Research Article
Hennecke C,Von der Haar H*,
Abstract
The inspection of aircraft engines is a complex and time-consuming process, usually requiring the disassembly of the engine or extensive baroscopic examinations. Thus, a method is to be developed in order to evaluate the state of the jet engine prior disassembling by analysing the state and structure of the exhaust jet. This could be done for instance with an analysis of the density, temperature, velocity or concentration distribution in a cross section through the exhaust jet. Assumptions are that failures inside the engine influence the exhaust jet in a measurable way and by means of numerical simulations it is possible to evaluate the flow and combustion process beginning in the engines’ interior through the exhaust gas jet. A generic study on a pilot scale annular combustion chamber is the basis to show the feasibility of this approach. The combustion chamber consists of eight premixed swirl burners. One of the burners has the option to be operated independently from the others on defined varied operation points. This simulates a failure state of a burner which allows an investigation of the correlation between defined failure states and resulting pattern in the exhaust jet. Detailed techniques are applied to evaluate the approach and the detection limits. Firstly, extensive numerical simulations of possible failure states were conducted to compare with measurements. Secondly, the particle image velocimetry (PIV) technique was used to measure the velocity field in the measurement plane downstream of the combustion chamber. Local reductions of the thermal power lower the acceleration of the exhaust gas and influence the velocity field. Thirdly, species concentrations were measured with a movable probe, evaluated by Fourier-transform infrared (FTIR) spectroscopy. Species concentration information can indicate combustor failures like locally mistuned air-fuel-ratio, serious defects on the swirl vanes, or oil leakages.