Abstract
The quantitative investigation of droplet laden turbulent flows at high temperature conditions is of great importance for numerous applications. In this study, an experiment was set up for investigation of evaporating urea–water sprays, which are relevant for the effective reduction of nitrogen oxide emissions of diesel engines using Selective Catalytic Reduction. A shadowgraphy setup is pushed to its limits in order to detect droplet diameters as small as 4 m and droplet velocities up to 250 m / s . In addition, the operating conditions of the gaseous flow of up to 873 K and 0 . 6 M Pa are an additional challenge. Due to the high temperature environment, image quality is prone to be compromised by Schlieren effects and astigmatism phenomena. A water-cooled window and an astigmatism correction device are installed in order to correct these problems. The results to be presented include characteristics of the turbulent gas flow as well as detailed spray characteristics at different positions downstream of the atomiser. It is demonstrated that the velocity of the gas can be approximated by the velocity of the smallest detectable droplets with sufficient accuracy. Furthermore, the statistical analysis of velocity fluctuations provides data for predicting the turbulent dispersion of the droplets.
Highlights
The characterization of sprays is of great importance for many technical applications.Prominent examples are fuel sprays in automotive and aircraft engines or spray drying in industrial processes
The rig was designed for operation at elevated temperature and pressure conditions in order to enable the investigation of pre- and post-turbo injection of urea–water solution (UWS)
The discussion of the initial results is based on the data taken at four measurement positions and at one hot gas operating condition, which are defined in Figure 1 and Table 2, respectively
Summary
The characterization of sprays is of great importance for many technical applications. Prominent examples are fuel sprays in automotive and aircraft engines or spray drying in industrial processes. The knowledge of droplet size or evaporation rates are essential for the operation of such systems [1]. In this context, spray modelling and numerical predictions are important tools for the design process. The goal of numerous experimental investigations is the tuning of model parameters of semi-empirical submodels or validating submodels and overall simulations [2]. An effective comparison of spray measurements and numerical simulations is the key for a deeper understanding of sprays
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