Energy combustion probes

Figure 1. Schematic energy-level diagrams for the three most widely used spectroscopic laser combustion probes (-------), virtual states (---), real states. Thick...

The statistical nature of the turbulent flame required the analysis of many temperature and density data points from separate pulses for accurate results. Thus, an overall computer system was used to control the various components of the combustion probe apparatus, and to collect and interpret the resultant data in an accurate and timely fashion. This system produced a block of data for each laser shot that included information about the Raman signals, LV readings, and ancillary data such as an identifying shot number and corresponding dye laser pulse energy. Typical current operation permits about twenty experimental run conditions daily, with up to several hundred shots per run. 

Free radicals are short-lived, highly-reactive transient species that have one or more unpaired electrons. Free radicals are common in a wide range of reactive chemical environments, such as combustion, plasmas, atmosphere, and interstellar environment, and they play important roles in these chemistries. For example, complex atmospheric and combustion chemistries are composed of, and governed by, many elementary processes involving free radicals. Studies of these elementary processes are pivotal to assessing reaction mechanisms in atmospheric and combustion chemistry, and to probing potential energy surfaces (PESs) and chemical reactivity. 

Some molecules in this group (HONO, NC j 0, HONC ) have been extensively studied because the photofragments OH and NO can be probed by tunable lasers. These molecules are important minor constituents in the earth atmosphere and their photochemistry plays a major role in air pollution. Atmospheric pollutants N0X (NO, NO2, NO3) are formed from combustion of fuel and subsequent chemical reactions in the atmosphere. Photolysis of alkyl oxides produces NO and NO2 that can be probed by LIF the internal energy distribution provides an important clue to the mechanism of photodissociation. 

As the propint bums, the intensity of the collimated beam increases due to the difference in the density of the solid propint and its combination products. The intensity of the emitted collimated beam of 7-rays that strike the scintillation probe after passing thru the combustion chamber is a function of the density and thickness of the material thru which the 7-rays pass. Since the walls of the combustion chamber remain fixed, their attenuation is constant. The attenuation of the 7-rays by the combustion products of the sample may also be neglected since the attenuation of the 7-rays is chiefly a function of material density. Thus, the emitted beam intensity is a function only of the position of the proplnt sample because the motion of the proplnt provides a variable attenuation of the emitted energy... 

The wavelength of fhe Stokes laser depends on the species to be probed with the CARS system. For nitrogen thermometry, a rhodamine dye laser is used that produces laser energy at about 607 nm and the CARS or anti-Stokes wavelength is 473 nm. Table 13.1 lists the Stokes and anti-Stokes wavelengths for species of infer-esf in air breafhing combustion assuming a 532 nm pump laser. 

Heitor, M. V., and Moreira, A. L. N. "Thermocouples and Sample Probes for Combustion Studies." Progress in Energy and Combustion Science 19 (1993) 259-78. 

Combustion processes are driven by energy-releasing chemical reactions. Detailed knowledge of the chemical kinetics of these individual reactive steps is required input to combustion models. For more than a decade, elementary gas-phase reaction kinetics has been successfully studied with the flash photolysis/resonance fluorescence technique (1-8). Typically, following broadband photolysis of a molecular precursor, reactant decays have been measured under pseudo-first-order kinetic conditions with cw resonance lamp excitation of free radical fluorescence. Increased utilization of laser probes in kinetic studies is exemplified by the recent pulsed-laser photolysis/pulsed-laser-induced fluorescence experiments of McDonald, Lin and coworkers (9-13). 

The first five years of the new century were Haber s most productive period, both in terms of the total number of publications (almost fifty) or the variety of topics he researched. He pursued different kinds of electrochemical studies (ranging from electrolysis of solid salts to the invention of the glass electrode for determining the acidity of liquids), researched the loss of energy by various prime movers (steam engines, turbines, internal combustion engines), and probed the luminous inner core of the Bunsen flame. In 1905 he published a book on the thermodynamics of technical gas reactions, which was soon translated into English. ... 

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