The dramatic changes in the thermophysical properties of SCO 2 lead to uneven distributions of local heat transfer coefficient and local temperature difference along the channel, especially in the region near the pseudocritical point (0.99 < T b/ T pc < 1.02). In this work, the local thermal-hydraulic characteristics of SCO 2 in the modified airfoil fins channel were numerically investigated under conditions of m = 1.06 – 2.26 g/s, T in = 328.7 – 388.7 K, and q w = -50 kW/m 2 and -100 kW/m 2. The PCHE with modified airfoil fins has better comprehensive performance than PCHEs with zigzag channels and NACA 0020 airfoil fins and the optimisation of the modified airfoil fins heat exchanger is crucial to the performance improvement of the SCO 2 Brayton cycle system. The printed circuit heat exchanger (PCHE) is an ideal candidate as a regenerator and pre-cooler in the SCO 2 Brayton cycle due to its advantages of high compactness and efficiency. Schrijer, B.W.The supercritical pressure CO 2 (SCO 2) Brayton cycle is an efficient and compact power cycle that has promising potential in solar and nuclear power generation systems. Graphic abstract: Įxperiments in Fluids: experimental methods and their applications to fluid flow, 62 (10) Part of collection In contrast, the analysis of the vortex dynamics in the trailing edge area revealed that vortices shed at the shock foot, which convect downstream in an area detached from the airfoil surface, cannot be considered responsible for the creation of UTWs in view of the mismatch in frequency of the two phenomena. The analysis allowed to estimate the velocity of the UTWs, obtaining values in good agreement with the literature. Finally, it was shown that by using the 11 most energetic POD modes, an accurate reduced-order model (ROM) is obtained, which when subtracted from the instantaneous velocity fields allows the visualisation of the small-scale structures present in the flow, such as the upstream travelling waves (UTWs) and the vortex shedding in the separated area near the trailing edge. The second mode was, instead, associated with an asymmetrical behaviour of the separated area and of the shear layer and displays a main peak at 320 Hz, being double the main buffet cycle frequency. The first and the third modes have a main frequency peak at 160 Hz and are well representing the separated area and the shock oscillation. It is found that the first three most energetic modes capture around 65 % of the total fluctuating kinetic energy. Proper Orthogonal Decomposition (POD) was applied to the PIV data to extract the main modes connected with buffet. A spectral analysis showed that the shock oscillation occurs with a dominant contribution at 160 Hz (St = 0.07, in good agreement with the literature) and between 25 and 55 % of the chord of the airfoil. The general behaviour of the buffet cycle was characterised with short-exposure schlieren visualisation and phase-averaged PIV measurements. 5 ∘, using schlieren and particle image velocimetry (PIV). (TU Delft Aerodynamics)Ībstract: Transonic buffet behaviour of the supercritical airfoil OAT15A was investigated experimentally at flow conditions Ma= 0.7 and α= 3. Experimental investigation of the transonic buffet cycle on a supercritical airfoil
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