Abstract
Abstract This paper describes measurments of the local temperature field near a combusting stream of methanol droplets using coherent anti-Stokes Raman scattering (CARS). Synchronizing the CARS measurements with the droplets in the stream allows correlations between the temperature field and the droplet position. These measurements describe the thermal structure of the droplet stream flame and can help validate detailed spray combustion models. The diameter of the droplets in the stream is 120 pm, which is comparable to the droplet size in a practical spray. The droplet spacing is approximately 1.0 mm (8 droplet diameters). The CARS measurements indicate a flame surrounding the droplet stream located I mm (8 droplet diameters) from the stream centerline. The temperature profile shows a local minimum temperature a the stream centerline. Moving radially outward from the centerline, the temperature rises at the flame (about 2000 K), and then falls gradually to room temperature. The local minimum temperature ...
Highlights
Experimental studies of the combustion of a single droplet, a droplet array, or a droplet stream are valuable because these combustion processes can duplicate essential features of realistic spray flames while avoiding the complex behavior of the spatial and temporal distributions of droplet size and velocity present in full sprays
The applicability to spray flames of previous single droplet and droplet stream combustion experiments is limited by larger droplet sizes than the size found in practical sprays (e.g., ~I mm in Miyasaka and Law, 1981 ; ~ I mm in Xiong et al, 1984; :::: 2 mm in Brzostowski et al, 1979; ~ l-4 mm in Brzostowski et al, 1981 ), and by experimental methods that preclude the measurement of temperature and concentration (Sangiovanni and Kesten, 1976; Sangiovanni and Dodge, 1978; Twardus and Brzostowski, 1978; Koshland and Bowman, 1984; Quieroz and Yao, 1989)
The CARSFT code has been extensively used a nd validated with coherent anti-Stokes Raman scattering (CARS) measurements in combustion systems (e.g ., Farrow et al, 1984; Lucht er al., 1987; Boyack, 1990)
Summary
Experimental studies of the combustion of a single droplet, a droplet array, or a droplet stream are valuable because these combustion processes can duplicate essential features of realistic spray flames while avoiding the complex behavior of the spatial and temporal distributions of droplet size and velocity present in full sprays. Montgomery et al (1990) reported temperature and concentration measurements in a multiple droplet stream flame. They measured the temperature field with a thermocouple so they could not obtain lhe local temperature field near individual droplets. The coherent nature of the CARS signal ensures strong discrimination from the background, even with droplets or particles in the flow
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