Inside the combustion chamber of a spark-ignition engine, NO fluorescence is excited with a narrow-band tunable KrF excimer laser. The fluorescence light is detected by an intensified CCD camera that yields images of the NO distributions. Rotational-vibrational transitions of NO are excited by the A(2)Σ+ ? X(2)Π (0, 2) band system around 248 nm. Single laser shot planar NO distributions are obtained with good signal-to-noise ratio at all crank angles and allow us to locate areas of NO formation during combustion. The pressure within the combustion chamber is measured simultaneously with the NO distributions, which allows the evaluation of correlations between indicated work and NO formation. The crank-angle-resolved sequences of two-dimensional NO distributions and averaged pressure traces are presented for different engine-operating conditions. In addition, laser-induced predissociation fluorescence of OH excited by the same laser source is measured in order to visualize the corresponding flame front propagation and to compare the time of formation of NO relative to that of OH.

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The purpose of this paper is to present the latest developments of laser diagnostic techniques for the application in technically applied turbulent combustion systems (i. e. an oil spray flame burner from "KORTINO HANNOVER AO"") as a tool for design and optimization purposes of furnaces and boilers. The advantages of those laser based nonintrusive measurement techniques over classical mechanical probes are multiple. The most important are: The nonintrusive character of laser diagnostics offers the possibility to investigate the combustion process without any disturbing effect on the occuring reactions and the actual flow field. Second the application of new pulsed powerful UV-Iasers in combination with "high-tech" intensified CeD-camera technology yield instantaneous spatial information about the occurring processes as well as temporal data. Third beside pure qualitative information about spatial distributions (OH. NO, O 2 , liquid fuel. vapor phase fuel), turbulence and temporally recurring structures also quantitative data about molecular densities can be obtained. It will be shown that locally limited gas tracer seeding at different positions into the air stream inside the mixing device and subsequent planar detection in the fuel/air mixing area lead to very important information for optimization and design purposes.

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