Simultaneous 2D single-shot imaging of oh concentrations and temperature fields in an si engine simulator

Abstract

Two-dimensional (2D) temperature measurements in engines are required for the detailed understanding of the combustion process. Because of the unsteady and turbulent nature of engine combustion, these measurements must be performed on a single-shot basis to obtain cycle-resolved results. Details of the flame front structure are also important to know for the numerical modeling of internal combustion processes. Simultaneous measurements of temperature and hydroxyl radical distributions provide such data sets. The combustion of methane in a fully transparent square piston engine was studied with a combination of 2D laser-induced fluorescence of hydroxyl radicals and 2D Rayleigh scattering. A tunable KrF excimer laser at 248 nm was used for the measurements. The wavelength of the laser was tuned to excite the P2(8) transition in the OH (3,0) band of the AX system. Spectral filtering of the resulting fluorescence to detect solely the fluorescence from the (3,2) band significantly reduces the effect of collisional quenching imposed to the fluorescence of the predissociating v' = 3 level by vibrational energy transfer (VET) to lower vibrational levels. Using a second camera, which only records the Rayleigh signals after appropriate filtering, allows the simultaneous measurement of temperature fields with a single laser. The analysis of corresponding OH and temperature images allowed the decision that the combustion conditions are in a regime where the flamelet approach for modeling is appropriate. Good agreement with model predictions has been achieved for the peak temperatures.

A Concentric Flow Conical Nozzle Burner for Highly Stabilized Partially Premixed Flames

“…It is relatively simple to apply in turbulent reacting and non-reacting flows. Laser induced fluorescence of OH radical technique has been applied in many turbulent flames and in practical systems by Kychakoff et al (1984), Allen and Hanson (1986), Becker et al (1994), Felton et al (1988) and Orth et al (1994) to study the flame front. In the present work simultaneous imaging of temperature, using Rayleigh scattering, and OH radical, using laser induced predissociation fluorescence (L1PF) (Andresen et al, 1990), has been carried out in four different flames of version I to study the structure of their reaction zone.…”

Optical diagnostics for direct injection gasoline engine research and development

“…Absorption spectroscopy of water was used for temperature measurements in Hcci engines (Ghandhi et al, 2003), Rayleigh scattering 10.5 Fuel film thickness measurement (mm) on the piston top of a direct injection engine using a refractive index matching approach (Drake et al, 2002). imaging has been used for studies on nitric oxide formation (Bräumer et al, 1995;Schulz et al, 1996), and flame propagation (Orth et al, 1994) has been used in research engines that were designed to minimize reflections. To suppress such reflections and Mie scattering from fuel droplets in direct injection engines, filtered Rayleigh techniques could in principle be used (Yalin and Miles, 1999).…”

Nonlinear diffusion filtering of images obtained by planar laser-induced fluorescence spectroscopy

“…Two-dimensional laser spectroscopic imaging has become one of the most valuable tools in the study of the physics and chemistry of turbulent reactive flows. 1 A variety of spectroscopic techniques are available for twodimensional imaging of relevant scalars in combustive flows: Raman spectroscopy, 2 Mie scattering, Rayleigh scattering, 3 and laser-induced fluorescence [3][4][5] have all been applied in a two-dimensional fashion in these environments. These techniques have in common that a suitable, high-power laser beam is shaped into a planar sheet that cuts through the measurement volume of interest.…”