Investigation of spatially resolved light absorption in a spark-ignition engine fueled with propane/air

Abstract

UV absorption in the combustion phase of spark-ignition engines strongly influences laser-induced-fluorescence measurements and flame-emission techniques because of the attenuation of a laser and/or signal light. This absorption was assessed with spatial, spectral, and temporal resolutions in an optically accessible research engine. Absorption was measured along a line for different crank-angle positions throughout the combustion phase of the engine by use of spectrally resolved transmittance measurements of both broadband illumination from a deuterium lamp and emission of laser-excited hot oxygen. Evaluating the spatial patterns of absorptivity revealed that no increased absorption can be attributed to the flame-front region and that homogeneous absorption cross sections for the whole burned-gas region can be assumed. The temporal change of absorption was shown to depend on the pressure effect with only negligible changes in absorption cross sections. Results obtained from the absorption measurements are applied for spatially resolved corrections of two-dimensional laser-induced-fluorescence measurements of NO concentration fields obtained under different operating conditions.

Methods to determine solubility parameters of polymers at high temperature using inverse gas chromatography

“…In 1916, Hildebrand11 pointed out that the relative solubility of a given solute in a series of solvents is determined by the internal pressures of the solvents. Later, Scatchard12 introduced the concept of cohesive energy density into Hildebrand's theory, identifying this quantity to be the internal pressure.…”

Three‐dimensional solubility parameters of poly(ε‐caprolactone)

“…In 1916, Hildebrand1 pointed out that the solubility of a given solute in a series of solvents is determined by the internal pressures of the solvents. Later, Scatchard2 introduced the concept of cohesive energy density into Hildebrand's theory, identifying this quantity with the internal pressure.…”

Attenuation effects on imaging diagnostics of hollow-cone sprays

“…However, in addition to distortion of measured spray images by attenuation of the exciting laser light, the images can suffer further from nonuniform attenuation of the signal. As reported by Hildenbrand et al 4 and Knapp et al, 3 the attenuation can be wavelength dependent. Investigations of the effect of signal loss that is due to scattering or absorption therefore need to be carried out with a suitable wavelength resolution.…”

“…1 Optical measurements in engines require a careful examination of the optical properties of all processes and equipment involved, in particular when the measurement of absolute quantities is required. It has been shown in engine experiments that laser beam 2 and signal 3,4 attenuations have a significant influence, eventually perturbing or preventing investigations of extended areas within the cylinder or leading to significant misinterpretation of signal intensities. Many of the frequently used laser techniques rely on excitation and detection in the UV spectral region where absorption by transient combustion products such as polycyclic hydrocarbons is strong even at small concentrations.…”