Alaa Omrane

Temperature measurements of single droplets by use of laser-induced phosphorescence

A novel technique for measuring droplet temperatures has been demonstrated. Laser-induced phosphorescence from thermographic phosphors, seeded to distilled water and iso-octane, was used to measure temperatures of single falling droplets. The phosphors were excited by the fourth and third harmonics of a Nd:YAG laser. The subsequent emission was evaluated by spectral and temporal investigations of the thermographic phosphors Mg4FGeO6:Mn and La2O2S:Eu, respectively. The spectral and the temporal methods permitted temperature measurements of free-falling droplets up to 433 K. Results from both methods, which show an estimated accuracy of better than 1%, are presented.

TWO-DIMENSIONAL SURFACE TEMPERATURE MEASUREMENTS OF BURNING MATERIALS

A new technique for two-dimensional temperature measurements of burning surfaces is presented. Laser-induced phosphorescence from a thermographic phosphor material applied to a surface of investigation was measured with a fast framing camera. The phosphor was excited by the 4th harmomic from a pulsed Nd:YAG operating at 10 Hz. The phosphorescence images measured by eight consecutively gated CCD detectors enable pixel-by-pixel lifetime evaluation of the phosphorescence by interpolating an exponential decay curve to the counts of the corresponding pixel positions of the sequential CCD images. The temperature at each pixel position was evaluated using a calibration procedure of temperature against lifetime. These measurement procedures were used for surface temperature measurements of the evolution of flame spread on low-density fiber boards. The results from experiments showed the possibility of measuring surface temperature during all phases of the flame spread. The total time window used for each two-dimensional temperature measurement was 800 mus to obtain high accuracy and precision at high temperatures, 680-780 K, temperatures characteristic of burning surfaces. The best precision, better than +/-5 K, was obtained at these temperatures. In this region, evaluation by the lifetime method shows a higher sensitivity to temperature than what can be expected from methods based on spectral line intensities. The results of the experiments were in accordance with those reported from previous one-point measurements. In the low-temperature region close to room temperature, the accuracy deteriorated considerably. The results obtained from the two-dimensional imaging experiments are presented and discussed. (Less)

Demonstration of Two-Dimensional Temperature Characterization of Valves and Transparent Piston in a GDI Optical Engine

Thermographic phosphors thermometry was used to measure engine valves and transparent piston temperatures in two dimensions as well point wise of a running, optically accessible, gasoline direct injection engine. The engine, fueled with isooctane, was operated in continuous and skip-fire mode at 1200 and 2000 rpm. A calibration of the phosphorescence lifetime and spectral properties against temperature allowed temperature measurements between 25 and 600mDC. Results from the measurements show the potential of the technique for two-dimensional mapping of engine walls, valves and piston temperatures inside the cylinder.

Piston Temperature Measurement by Use of Thermographic Phosphors and Thermocouples in a Heavy-Duty Diesel Engine Run Under Partly Premixed Conditions

Piston temperature experiments were conducted in a single-cylinder heavy-duty diesel research engine both by use of optical temperature sensitive phosphor and of thermocouples mounted on the piston surface. In the former case, a thin coating of a suitable thermographic phosphor was applied to the areas on the piston surface to be investigated. The optical measurements involved the use of an optical window and of an endoscope. The possibility of using optical fibres into guide light in and out of the engine was also investigated. Results of the optical and of the thermocouple measurements were compared and were also related to more global data with the aim of exploring the use of thermographic phosphors for piston-temperature measurements in diesel engine. Thermographic phosphors thermometry was found to represent an alternative to the thermocouple method since it easily can be applied to various piston geometries.

Optical diagnostics for characterization of a full-size fighter-jet afterburner

In the present work the feasibility of using various optical/laser based techniques for characterization of the afterburner of a full-size aircraft engine have been investigated. The tests have been performed on-site at Volvo Aero Corporation and were mainly directed towards surface thermometry using thermographic phosphors and fuel visualization. All applications were studied for different engine running conditions, including various use of the afterburner (A/B). Laser-Induced Fluorescence (LIF) was employed for fuel visualization to investigate to what extent unburned fuel exits the afterburner. Laser-Induced Phosphorescence (LIP) from thermographic phosphors was used to measure two-dimensional surface temperatures on the outlet nozzle of the afterburner. In addition, the spectral characteristics of the burning jet stream were investigated. Copyright