Non-swirling steady and transient flow simulations in short-form spray dryers

This paper numerically investigated the effect of chamber aspect ratio and operating conditions on flow stability within a short form spray dryer without the inclusion of droplet injection. Extensive analysis using different mesh configurations led to a new finding on the effect of expansion ratio on flow stability. A larger expansion ratio produces a more stable flow, which is due to the limitation of the jet fluctuation by the outlet geometry constriction. However, the flow might not be completely steady as fluctuations are magnified at higher inlet velocities, which can be explained by the confined jet feed-back mechanism. Fast Fourier Transform (FFT) analysis of the computed instantaneous velocity at selected spatial locations in the chamber revealed the effect of the chamber expansion ratio on periodicity of the flow structure. It is observed that changes in the expansion ratio primarily affect the amplitude of the 'noise' region in the frequency spectrum.