Design and construction of an open loop subsonic high temperature wind tunnel for investigation of SCR dosing systems

The requirement of high-fidelity experimental data of microscopic properties as well as the whole spray development is fundamental since they are determinant in the understanding of atomization and evaporation process in a variety of multiphase flows. The Selective Catalytic Reduction (SCR) system is one of the industrial applications where understanding the whole spray atomization and development process is essential in developing new systems to cope with stringent emission regulations. A new subsonic heated open-loop wind tunnel has been designed and manufactured specifically with a 0.25 × 0.25 m cross-section and 1.59 m long optically accessible quartz glass side panels. The purpose of the wind tunnel was to investigate Selective Catalytic Reduction (SCR) sprays using Phase Doppler Anemometry (PDA). The wind tunnel is capable of reaching a flowrate equating to 50 m/s in the test section when operating at standard room conditions (25°C and 101,325 kPa). A 145 kW heater is mounted downstream the blower to achieve air temperatures of up to 400°C with maximum air mass flow of 1200 kg/h. The diffuser, flow conditioning and contraction cone sections of the wind tunnel have been designed to minimize velocity and temperature gradients within the test section while minimizing flow disturbances. A diffuser with a cone angle of 5° and an area ratio of 3.95 and a contraction cone with a contraction ratio of 4.05 was selected. The test section has been designed to give complete visible access through top and both sides, while the bottom is made of stainless steel. The two sides are made of quartz glass to provide the best signal transmission quality for usage with any optical equipment e.g. PDA. The top of the test section has sections made of Robax glass with detachable windows for easy mounting and dismounting of any equipment subject to be tested in the flow section. The streamwise turbulence intensity in the test section was found to be less than 2% in the core with similar values for the cross-stream turbulence intensities. The complete design and construction of each section of the wind tunnel has been presented and discussed in this paper.