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In this paper, finite element shape optimization is used to determine the optimum air cleaner shape and rib design for low shell noise. Shape variables are used to vary the height and location of rib elements, as well as vary the shape of the air cleaner surfaces. The optimization code evaluates each design variation and selects a search direction that will reduce surface velocity. Sound power radiation is calculated for each optimized design using an acoustic code. Large reductions in shell noise were achieved by optimizing the shape of the air cleaner surface and rib design. Optimization of the rib pattern alone yielded a local optimization, as opposed to a global optimization that represented the best possible design.

Simplified closed form equations are developed to predict the sound power radiated from a simply supported rectangular flat plate in an infinite rigid baffle. A modification is added to include the effect of periodic uniform ribs in either uni-directional or a cross hatch pattern. The equations are correlated to finite element/acoustic code analysis. The accuracy of the equations is presented for typical induction system components and an expression is developed to predict the error for other panel configurations.