Multiobjective optimization of an ionizer nozzle structure based on RSM and CFD

To improve the electrostatic elimination speed and ability of corona ionizers, the distance from the hole to the center of the tungsten needle \(R\) $R$ , the height of the inner wall \(H,\) $H,$ and the distance from the tungsten needle to the inner wall \(L\) $L$ were selected as variables to optimize the structural parameters of the ionizer nozzle. The average flow rate \({V}_{a}\) $V_a$ and flow field uniformity \(\gamma\) $\gamma$ were proposed as the responses to evaluate the performance of the ionizer. Response surface methodology (RSM) and face-centered cubic (CCF) design were used to systematically study the influence of structural parameters on the performance of the ionizer. A computational fluid domain model of the ionizer was established and simulated by computational fluid dynamics (CFD). Finally, the regression equations between \({V}_{a}\) $V_a$ or \(\gamma\) $\gamma$ and structural parameters were obtained through multiple regression analysis. The result shows that the feasibility of using the flow field parameter as an index of the ionizer is confirmed. By means of analysis of variance, the sensitivities of structural parameters affecting \({V}_{a}\) $V_a$ are F( \(R\) $R$ ) > F( \(L\) $L$ ) > F( \(H\) $H$ ), and the sensitivities of structural parameters affecting \(\gamma\) $\gamma$ are F( \(L\) $L$ ) > F( \(R\) $R$ ) > F( \(H\) $H$ ). The optimal structural parameters are \(R\) $R$ =5.998 mm, \(H\) $H$ =5.520 mm, and \(L\) $L$ =1.184 mm. With the optimum nozzle geometry, the static electricity elimination performance can be improved. The decay time is less than 2.5 s and the offset voltage is not more than 6 V when the ionizer B ventilation pressure is 0.2 MPa and the distance is 30–80 cm.