Flow Characteristics and Air-distribution Uniformity in Passenger-coach Air-conditioning Ducts

Nonuniform air distribution in passenger-coach air-conditioning ducts commonly causes insufficient distal airflow and reduces cabin thermal comfort. In ducts with uniform cross-sections, continuous air discharge through distributed outlets induces streamwise static-pressure attenuation, resulting in a typical front-dominant, rear-deficient airflow pattern. This study combines theoretical analysis, computational fluid dynamics (CFD), and multiobjective optimization to investigate the flow characteristics and uniform air-supply strategy of a passenger-coach air-conditioning duct. The results demonstrate that static-pressure decay is the primary mechanism responsible for outlet-flow maldistribution and that global outlet-radius reduction provides only limited improvement. In contrast, a streamwise graded-radius scheme, in which the outlet radii generally increase from the upstream to the downstream region with local corrections at selected outlets, effectively compensates for pressure attenuation and enhances distal airflow. Based on CFD data, cubic polynomial correlations between the preliminarily optimized outlet radius and the distance from the fan-side reference position are established for both ducts, with coefficients of determination exceeding ۰.۹۰. Guide-vane optimization using Gaussian process regression, support vector regression, and a genetic algorithm further indicates that guide vanes mainly provide local flow regulation, whereas radius gradation governs the global redistribution of airflow. The optimized radius scheme reduces the left-duct flow nonuniformity coefficient by ۸.۲%. Because the radius fitting and guide-vane optimization are based on limited simulation samples, the resulting correlations should be regarded as preliminary design references that require further validation.

کلیدواژه ها:

Guide-vane optimization ، Multiobjective optimization ، Passenger-coach air-conditioning duct ، Outlet radius ، Streamwise uniformity