LAUSR

Abstract Based on constructal theory, the optimal design of a dual-pressure turbine in OTEC system is performed under the condition of fixed total volume of the turbines. The total power output of the turbines is chosen as the optimization objective, and the volume fraction, ratio of wheel diameter and relative flow angle at rotor outlet are employed as the optimization variables. The optimal performance and optimal constructs of the dual-pressure turbine with the same and different structural parameters are obtained, respectively. Besides, the influences of five parameters on the constructal optimization results of the dual-pressure turbines are analyzed. The results show that compared with the initial design point, the total power output of the turbines after primary, twice and triple constructal optimizations are increased by 0.69%, 1.82% and 2.02%, respectively. The optimal volume fraction, ratio of wheel diameter and relative flow angle at rotor outlet of the turbines after triple constructal optimization are 0.243, 0.49 and 28°, respectively. The total power output of the turbines will increase with the increases of the inlet pressure of the low-pressure turbine, mass flow rate ratio of the working fluids, total volume of the turbines and absolute flow angle at rotor inlet, and will decrease with the increase of the reaction degree. The constructal optimization results of the high-pressure and low-pressure turbines with the same and different structural parameters are similar. The maximum total power outputs of the two cases are both 50.38 kW, and the largest difference is that the optimal volume fraction is reduced by 4.33%. The obtained results can provide theoretical guidelines for the optimal designs of the dual-pressure turbines in OTEC systems.