Experimental and numerical comparisons of geometric scaling criteria for lean premixed swirl combustor

Abstract

This study experimentally and numerically investigates the applicability of the DaI and Re criteria for scaling the geometry of a lean premixed swirl combustor during a reaction and in the absence of it. We first set up an experimental system to test the loss of pressure, the flow field, and NOx emissions in a prototype combustor and two models of it scaled to 3/5 of its size. The results showed that the friction in the flow in the prototype decreased with an increase in its intensity, and the corresponding constant DaI model (M-D) exhibited a similar trend, while the constant Re model (M-R) exhibited an adverse trend to that of the prototype. The results of particle image velocimetry (PIV) of the flow field in the non-reactive state showed that regardless of the criterion used and the state of the reaction, the flow fields of the prototype and the models were similar under flows of different strengths. However, a quantitative comparison of their distributions of velocity showed that the peak velocity of the rotating jet of M-R was significantly lower than that of the prototype. PIV results of the flow field in the reactive state exhibited similar phenomena. Moreover, the NOx emissions of M-D were consistent with those of the prototype, while emissions from M-R were significantly higher. The numerical results also showed that the shape of the flame and the pattern of flow of M-R were significantly different from those of the prototype.