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Summary This study aimed to develop a novel antioxidant film for food packaging based on Cyperus esculentus starch and thymol. The mechanical, physicochemical and antioxidant properties of composite films were investigated. The C. esculentus starch showed good film‐forming properties. Incorporating of thymol improved the elongation at break and ultraviolet barrier property of the films, meanwhile decreased the moisture content of the films. Scanning electron microscopy showed good compatibility between starch matrix and thymol. The formation of hydrogen bonds between starch and thymol was confirmed by Fourier transform infrared spectroscopy and X‐ray diffraction. The composite films (3% thymol) exhibited higher antioxidant with DPPH scavenging capacity values of 73.22 ± 2.05% compared with control films. This study provided a potential unconventional starch for the preparation of bioactive films.

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Nozzle guide vane platforms often employ complex cooling schemes to mitigate the ever-increasing thermal loads on endwall. This study analyzes, experimentally and numerically, and describes the effect of coolant to mainstream blowing ratio, momentum ratio and density ratio for a typical axisymmetric converging nozzle guide vane platform with an upstream doublet staggered, steep-injection, cylindrical hole purge cooling scheme. Nominal flow conditions were engine-representative and as follows: Maexit = 0.85, Reexit,Cax = 1.5×106 and an inlet large-scale freestream turbulence intensity of 16%. Two blowing ratios were investigated, each corresponding to the design condition and its upper extrema at M = 2.5 and 3.5, respectively. For each blowing ratio, the coolant to mainstream density ratio was varied between DR=1.2, representing typical experimental neglect of coolant density, and DR=1.95, representative of typical engine conditions. The results show that with a fixed coolant-to-mainstream blowing ratio, the density ratio plays a vital role in the coolant-mainstream mixing and the interaction between coolant and horseshoe vortex near the vane leading edge. A higher density ratio leads to a better coolant coverage immediately downstream of the cooling holes but exposes the in-passage endwall near the pressure side. It also causes the in-passage coolant coverage to decay at a higher rate in the flow direction. From the results gathered, both density ratio and blowing ratio should be considered for accurate testing, analysis, and prediction of purge jet cooling scheme performance.