Numerical optimisation of the diffuser in centrifugal blower

Vodilnik je sestavni del kompresorjev in njegova naloga je pretvorba kinetične energije medija v tlačno. V tem delu smo na osnovi numeričnih simulacij toka zraka optimizirali geometrijo vodilnika, ki je del centrifugalnega puhala. Izdelan je bil parametričen geometrijski model in splošna numerična mreža, ki je primerna za parametrično študijo najrazličnejših variant vodilnikov. Izbrana je numerična metoda in robnimi pogoji, ki zagotavljajo dobro konvergenco časovno neodvisnih simulacij. Za modeliranje turbulentnega toka je bil uporabljen model SST k-omega. Učinkovitost različnih vodilnikov je bila ovrednotena s koeficientom obnovitve tlaka, na osnovi katerega je izbran optimalen vodilnik. Določenih je bilo pet geometrijskih parametrov vodilnika, ki predstavljajo vhodne parametre optimizacije. Optimizacija je bila avtomatizirana s pomočjo genetskega algoritma, ki po principu naravne selekcije predlaga nove rešitve na podlagi najboljših predhodnih rešitev. Izmed več kot 400 izvedenih simulacij je bilo izbranih pet vodilnikov, katerih rezultati so bili analizirani in primerjani s serijskim vodilnikom. Optimalen vodilnik je dosegel 7,3 % večji koeficient obnovitve tlaka od serijskega. Izbrani vodilniki so bili izdelani iz aluminija, vstavljeni v puhalo in testirani. Primerjava koeficientov obnovitve tlaka pridobljenih na podlagi simulacij in izmerjenih izkoristkov puhala pokaže enak trend. S tem so bile validirane numerične simulacije kot tudi optimizacija. Z novim vodilnikom se je izkoristek puhala v delovni točki povečal za 1,3 %, pri večjih pretokih do 4 %.The diffuser is a component of compressors, and its purpose is to convert the kinetic energy of the medium into pressure energy. In this work, the diffuser of centrifugal blower was optimised based on numerical simulations of air flow. A parametric 3D model and a universal numerical mesh suitable for a parametric study of different diffuser variants were developed. An appropriate numerical method and boundary conditions were selected to ensure good convergence of steady-state simulations. An SST k-omega model was used to model the turbulent flow. The performance of different diffusers was evaluated by the pressure recovery coefficient, based on which the optimal diffuser was selected. Five design parameters were defined, which are also the input parameters of the optimisation. The optimisation was automated with a genetic algorithm which is inspired by the process of natural selection and proposes new solutions based on the best previous solutions. More than 400 simulations were performed, out of which five diffusers were selected, their results analysed, and compared with the original diffuser. The optimal diffuser achieved a 7.3 % increase in pressure recovery coefficient compared to the original one. The selected diffusers were manufactured out of aluminium, inserted into the blower, and tested. A comparison of the pressure recovery coefficients obtained from simulations and the efficiency results obtained experimentally, showed the same trend. Therefore, both the numerical simulations and the optimisation were validated. With the new diffuser, the efficiency of the blower increased by 1.3 % at the design flow rate and by up to 4 % at higher flow rates