Multi-objective optimization and system evaluation of recuperated helicopter turboshaft engines

Targeting higher efficiency and lower emissions, the employment of recuperators in helicopters is well recognized as an attractive technical strategy to enhance the operational capabilities. Primary surface recuperator (PSR) is proposed for such applications, as its favorable characteristics of good heat transfer performance and compact structure enable a light weight recuperator design in the aeroengine industry. Aimed at designing a PSR potentially applicable to rotorcraft powerplants, initially, promising heat transfer surface geometries are evaluated based on their aerothermal performance. Subsequently, through the execution of multi-objective genetic algorithm optimization, interdependencies between recuperator weight and thermal effectiveness are quantified under specific constraints, with respect to the selected heat transfer surface geometries. Eventually, acquired results of optimal designs are further analyzed within a multidisciplinary simulation framework for performance assessment of complete helicopter operations under given flight conditions. It is found from helicopter mission analysis that the optimum trade-off between fuel saving benefits and associated recuperator weight penalty is attained for the employed effectiveness of 76.1% with recuperator weight of 27.48 kg. The proposed methodology could be adopted as a cost-effective and computationally-efficient tool for the multidisciplinary design and optimization of rotorcraft powerplant systems incorporating high performance recuperators.