To improve the aerodynamic characteristics of compressor blades, a novel asymmetric leading edge (ASYLE) has been introduced and shown to offer superior performance. However, the aerodynamic robustness of such specially designed leading edge (LE) remains unclear due to the considerable uncertainty problems it presents. This paper investigates the robustness of ASYLE blade under both geometric and operational uncertainties. Profile deviations within ±0. 05mm were introduced to investigate the influence of manufacturing errors. In addition, the perturbated inflow angles between ±0. 375° were considered for uncertain inflow conditions. The statistic aerodynamic performance as well as operating dispersibilities at Ma=0. 7 were obtained by the non-intrusive polynomial chaos (NIPC) method. The results show that considering uncertain profile errors, the operating range of ASYLE blade is 2. 3° wider than original leading edge (ORILE) blade and the dispersion of total pressure loss can be reduced by 53. 1% at β1=45. 8°. Regarding uncertain inflow angle variations, the total pressure loss dispersion of ASYLE blade can be reduced by 93. 8% at β1=50. 8°. The ASYLE shows better overall aerodynamic robustness than ORILE upon considering uncertainty limits. The influence propagations in the flow fields of both uncertainties were further analysed, which revealed that the variations of separation bubble structure near LE are the direct cause to the aerodynamic uncertainties. The ASYLE design effectively controls the size and variation of LE separation bubble and thus demonstrates better aerodynamic robustness.

Because the helical axial flow gas-liquid mixing pump has the great advantage of conveying gas-liquid two-phase mixed medium, it has become the main core equipment for deep-sea oil and natural gas exploitation. The gas phase aggregation and bubble movement trajectory in the impeller channel have been widely studied, but the increase of medium flow resistance caused by flow separation has not been deeply discussed. Combined with the Euler multiphase flow model and the SST k-ω turbulence model, the numerical calculation of the helical axial flow gas-liquid mixed pump is carried out. Under design flow conditions Q = 100 m3/h, head H = 30 m, speed n = 4500 r/min, specific speed ns =213. 6 r/min, and under different inlet gas content conditions, the influence of the bionic waveform leading edge blade on drag reduction characteristics of the helical axial flow gas-liquid mixed pump was investigated. By designing the blade with a leading-edge structure with different heights and pitches, the separation of the mixed medium and the suction surface is effectively suppressed, and the flow resistance of the medium in the 1/10 area of the inlet end of the blade is reduced. The results show that when the height A is 0. 25%L and the pitch λ is 12. 5%h, the maximum drag reduction rate in this region is 52. 6%, the maximum increase in efficiency of the mixed pump is 2. 2%, and the maximum increase in head is 4. 8%. This study can provide technical support for flow drag reduction in gas-liquid mixed pump.

This study investigates the performance of Cylindrical-conical-and clover-shaped film cooling holes of gas turbine blades and the effect of transverse trench on film cooling hole efficiency. The purpose of the research was to achieve the optimal film cooling geometry in order to gain the highest film cooling hole of gas turbine blade efficiency. In this study, a three-dimensional blade simulation that based on k-e realizable turbulence model. Cooling fluid was injected into the mainstream at 30◦ on leading edge stagnation row, with BR=1, 1. 5, 2. After injecting the cooling fluid into Cylindrical-conical-and clover-shaped film cooling holes geometries with and without the presence of transverse trench, it was observed that clover-shaped hole with transverse trench along, at BR=2 and film cooling efficiency of 0. 147 offers the highest film cooling efficiency. Investigation on transverse trench effect for all geometries showed that the presence of trench leads to a higher film cooling efficiency.

The present paper investigates turbulent flow of film cooling on model turbine blade leading edge using two scale-resolving attitude of turbulent flow modeling. In the first attitude the detached eddy simulation (DES) approach based on Spalart-Allmaras and in the second attitude the large eddy simulation (LES) approach will be used. Results show that the DES approach due to its hybrid nature and applying RANS models in near walls, predicts the Fluctuations of span wise direction in coolant pipe lower. As result, the coolant flow imports to the main flow with lower turbulence. Also DES approach predicts less turbulent kinetic energy lateral distribution and further turbulent heat flux in near walls. So, in DES approach the adiabatic effectiveness on turbine blade leading edge predicted lower than LES approach and experimental data. In addition, results show that mixture of coolant jet and mainstream hot gas in DES approach is estimated lower than LES approach. In total, it can be deducted that although DES approach provides acceptable results in far wall region, but in near wall region it has problems in correct prediction of turbulence Specifications. In addition, the main advantage of DES approach in comparison with LES approach is 40% reduction of computational cost that can explain using this approach.

Turbulent impinging jet array is one of the most efficient and popular techniques for cooling gas turbine blades. In the present paper, we numerically investigated how the geometrical design parameters affect the cooling performance for jet array impinged to a curved target. The influence parameters, including jet spacing (2.5≤Pj≤10), jet angle (-45°≤θ≤+45°), and off-center distance (0≤Ej≤6) on average Nusselt number (Nu), air pressure drop (Δp), and heat transfer uniformity index (UI) were identified through a parametric study at a constant total mass flow rate. Results show, increasing jet spacing improved heat transfer but lowered uniformity and required more compression power. Tilting the jets generally decreases the average Nusselt number but boosts the uniformity. Also, increasing the inclination angle reduces the pressure drop. Moving the jets off-center consistently lowered pressure drop until Ej=4 and average Nusselt number till Ej=2 without affecting uniformity much up to until Ej=3, and beyond those values, increased them. best performance based on average Nusselt number is achieved for the case of Pj=10, θ=0°, and Ej=0. Also, the uniformity index is maximized and pressure drop is minimized at Pj=5, θ=+45°, and Ej=0.

It is essential to maintain the aerodynamic performance of the air-conditioning system meanwhile reducing the noises (including aerodynamic, broadband, and discrete noises), determining the consumer's comfort level. In this work, depending on the coupling of the wavy leading-edge and the seagull airfoil, the aeroacoustics noise and aerodynamic performance of the impellers with the coupling bionic blade were investigated in detail. The results indicate the aerodynamic performance was improved by the coupling bionic optimization. Moreover, the total pressure efficiency (η) of the coupling bionic blade increases by 2. 28% in comparison to the original blade. Furthermore, A smaller static differential pressure is observed between the suction and pressure sides, and vortices and backflows from the pressure side to the suction side are hampered, causing a reduction in turbulence noise. Additionally, the broadband noise of the coupling bionic blade decreases by 3. 59 dB. Besides, the coupling bionic blade improves the directivity of the sound pressure level, especially in the middle-frequency and low-frequency region, resulting in a decrease of 7. 9 dB for the aeroacoustics noise of the coupling bionic blade. What's more, the modal analysis demonstrates the security of the designed coupling bionic blade. In generally, this work provides some inspiration to design axial flow fans with excellent aerodynamic performance and low-noise characteristics.

Numerous studies have been conducted to investigate effect of blade geometry of vertical axis wind turbine performance. Most of the evaluations have focused on the airfoil series and airfoil geometry parameters such as thickness and camber of the airfoil. Few studies have examined the effect of other blade geometry parameters on the vertical axis wind turbine performance. In the present study, the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied. Hence, modified NACA 0021 airfoil profiles were created using the geometric method (CST). Then, the flow behavior around a Darrieus vertical axis wind turbine was simulated under the influence of the reduction and set-up coefficients of the leading-edge radius at a constant wind speed of 9 m/s and a tip speed ratio of 1. 5 to 3. 5 using the computational fluid dynamics. Additionally, the effects of the examined parameter (leading-edge radius) on fluid flow and aerodynamic performance coefficients, including the coefficients of power and torque, were investigated. The results indicated that the leading-edge radius affected the near wake flow of the turbine, and the optimization of leading-edge radius parameter controls the dynamic stall and reduces the formation of a vortex. Finally, the optimization of LER revealed that at 20% reduction in the LER the performance of the turbine at tip speed ratio of 1. 5 was increased by more than 50%. This reinforces the self-starting capability of a Darrieus wind turbine.

One of the effective parameters of the behavior of rockfill materials is particle breakage. As a result of particle breakage, both the stress–strain and deformability of materials change significantly. In this article, a novel approach for the two-dimensional numerical simulation of the phenomenon in rockfill (sharp-edge particles) has been developed using combined DEM and FEM. All particles are simulated by the discrete element method (DEM) as an assembly and after each step of DEM analysis, each particle is separately modeled by FEM to determine its possible breakage. If the particle fulfilled the proposed breakage criteria, the breakage path is assumed to be a straight line and is determined by a full finite element stress–strain analysis within that particle and two new particles are generated, replacing the original particle. These procedures are carried out on all particles in each time step of the DEM analysis. Novel approach for the numeric of breakage appears to produce reassuring physically consistent results that improve earlier made unnecessary simplistic assumptions about breakage. To evaluate the effect of particle breakage on rockfill's behavior, two test series with and without breakable particles have been simulated under a biaxial test with different confining pressures. Results indicate that particle breakage reduces the internal friction but increases the deformability of rockfill. Review of the v–p variation of the simulated samples shows that the specific volume has initially been reduced with the increase of mean pressures and then followed by an increase. Also, the increase of stress level reduces the growing length of the v–p path and it means that the dilation is reduced. Generally, any increase of confining stress decreases the internal friction angle of the assembly and the sample fail at higher values of axial stresses and promotes an increase in the deformability. The comparison between the simulations and the reported experimental data shows that the numerical simulation and experimental results are qualitatively in agreement. Overall the presented results show that the proposed model is capable with more accuracy to simulate the particle breakage in rockfill.

Effect of the volute tongue of the multi-blade centrifugal fan on the performance of the machines is significance. The shape and installation angle of the volute tongue affect the circulating internal flow behavior of the volute as well as the energy loss around the volute tongue. In this study, the profile of the leading edge of the owl wing is applied to the volute tongue of a multi-blade centrifugal fan to improve the aerodynamic performance of the fan. The fan models with different volute tongue installation angles are numerically simulated under different flow conditions. The research results show that the proposed design is able to improve the aerodynamic performance of the fan at different flow rate conditions. In addition, an improved method for quantitatively evaluating the level of impeller-volute tongue interaction based on the unsteady simulation result is proposed and it is verified to be effective. Furthermore, the two parameters for evaluating the internal flow circulation which are influenced by the installation angle of the bionic volute tongue are analyzed, namely the recirculated flow coefficient and the reversed flow coefficient. Combined with the analysis of energy loss around the volute tongue, the mechanism of variation of the aerodynamic performance of the multi-blade centrifugal fan with different volute tongue installation angles is explained.