Infrared high-speed thermography of combustion chamber wall impinged by diesel spray flame

As a demonstration of a new method to examine the extremely unsteady and spatially varying wall heat transfer phenomena on diesel engine combustion chamber wall, high-speed imaging of infrared thermal radiation from the wall surface impinged by a diesel spray flame was attempted using a high-speed infrared camera. A 35 mm-diameter chromium-coated quartz window surface was impinged by a diesel spray flame with an impinging distance of 27 mm from the nozzle orifice in a constant volume combustion chamber. The infrared thermal radiation from the back surface of the 0.6 µm thick chromium layer was successfully visualized at 10 kHz frame rate and 128 × 128 pixel resolution through the quartz window. The infrared radiation exhibited coherent and streaky structure with radial stripes extending and waving from the stagnation point. The width of the radial stripes, spatial amplitude and the period of the waving movement were comparable to the ones for turbulent heat transfer on the engine cylinder wall previously measured with a heat flux sensor, suggesting that they are resulting from the turbulent structure in the wall-impinging diesel flame. The radiation intensity was calibrated to temperature and converted to heat flux via 3-D numerical analysis of transient thermal conduction in the quartz window. The peak-to-peak variation amplitudes of temperature and heat flux among the radial stripes during the diesel spray flame impingement were about 20 K and 2.3 MW/m2, corresponding to 13% of 150 K maximum temperature swing amplitude and 18 MW/m2 maximum heat flux, respectively.

Improvement in the Flux Uniformity of the Solar Dish Concentrator System through a Concave Quartz Window

A nonuniform and high-strength heat flux load would reduce the working efficiency, safety, and in-service life of a cavity receiver. Four types of concave quartz windows, including conical, spherical, sinusoidal, and hyperbolic tangent, were proposed to be used in the cylindrical cavity receiver of a solar dish concentrator system, which can improve the flux uniformity and reduce the peak concentration ratio of the receiver. For each concave quartz window, 36 structural schemes were offered. Based on the Monte Carlo ray-tracing method, the results showed that the nonuniformity coefficient of the receiver was 0.68 and the peak concentration ratio was 1320.21 by using a plane quartz window. At the same time, when the receiver is in the best optical performance, it is the receiver with sinusoidal, conical, spherical, and hyperbolic tangent quartz windows, respectively. The optical efficiency of the receiver with the above four types of quartz windows was basically the same as that of the receiver with the plane quartz window, but their nonuniformity coefficients were reduced to 0.31, 0.35, 0.36, and 0.39, respectively, and the peak concentration ratio was reduced to 806.82, 841.31, 853.23, and 875.89, respectively. Obviously, the concave quartz window was better than the plane quartz window in improving the flux uniformity. Finally, a further study on the sinusoidal quartz window scheme of all of the above optimal parameter schemes showed that when the installation position of the receiver relative to the dish concentrator was changed, the flux uniformity of the receiver could continue to improve. When the surface absorptivity of the receiver was reduced, the optical efficiency would be reduced. For the parabolic dish concentrator with different focal distance, the concave quartz window can also improve the uniformity of the flux distribution of the cylindrical cavity receiver.

Inactivation ofStaphylococcus aureusandEscherichia coliO157:H7 on fresh kashar cheese with pulsed ultraviolet light

Pulsed ultraviolet light is a potential postprocessing decontamination method which is able to reduce pathogens on solid food surfaces. Cheese surfaces may become easily contaminated with pathogens due to improper handling or contact with unhygienic surfaces during or after processing. In this study, the effects of pulsed ultraviolet light on Staphylococcus aureus and Escherichia coli O157:H7 on fresh kashar cheese were investigated. Pulsed ultraviolet light was applied to kashar cheese for different times (5, 15, 30, 45, 60 s) at 5, 8, and 13 cm from the quartz window in a pulsed ultraviolet light system. Based on the inactivation level, time, and visual evaluation, the most favorable treatment was determined as the 45 s–13 cm treatment (∼44 J/cm2). This treatment yielded about 1.62 and 3.02 log10reductions (cfu/cm2) for S. aureus and E. coli O157:H7, respectively, while did not alter (p>0.05) the pH, lipid oxidation, and moisture content of kashar cheese, except the color parameters. When 0.5 cm thick kashar cheese was treated with pulsed ultraviolet light at a distance of 5 cm from the quartz window, the highest energy transmittance was found to be about 9.16%. These findings demonstrate that pulsed ultraviolet light has the potential for postprocessing decontamination of semi-hard cheese surfaces.

The LUCID-2 detector

The LUCID-2 detector is the main online and ofline luminosity monitor of the ATLAS experiment. It is a compact Cherenkov detector made of photomultipliers with a 10 mm diameter quartz window acting as the Cherenkov medium. In order to provide a reliable luminosity measurement during years of data-taking, the LUCID-2 detector can use 104 different luminosity algorithms for each of the LHC colliding bunches. The detector stability is kept at a percent level thanks to an innovative monitoring system based on radioactive Bi-207 sources deposited on the photomultipliers quartz window. Combining the LUCID-2 measurement with those of other four ATLAS subdetectors, the luminosity has been estimated with a total uncertainty of 2.1% in 2015 and 2.2% in 2016.

The LUCID-2 Luminometer

The LUCID-2 detector is the main online and offline luminosity monitor of the ATLAS experiment. It provides 104 different luminosity measurements from different algorithms for each of the thousands of LHC bunches. The new detector is using the quartz windows of 10 mm diameter photomultipliers and optical quartz fibers as the Cherenkov medium. A main challenge for a luminometer is to keep the efficiency constant during years of data-taking. LUCID-2 is using an innovative calibration system based on radioactive Bi-207 sources deposited on the quartz window of the readout photomultipliers.

Dynamic Modeling of a Solar Reactor for Zinc Oxide Thermal Dissociation and Experimental Validation Using IR Thermography

A dynamic numerical model of a solar cavity-type reactor for the thermal dissociation of ZnO is formulated based on a detailed radiative heat transfer analysis combining the Monte Carlo ray-tracing technique and the radiosity enclosure theory. The quartz window is treated as a semitransparent glass layer with spectrally and directionally dependent optical properties. Model validation is accomplished by comparison with experimental results obtained with a 10-kW solar reactor prototype in terms of cavity temperatures, reaction extents, and quartz window temperature distribution measured by IR thermography. The solar-to-fuel energy conversion efficiencies obtained experimentally are reported, and the various energy flows are quantified.