Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 5 Articles
Further optimal design of an axial-flow water pump calls for a thorough recognition of the characteristics of the complex turbulent\nflow field in the pump, which is however extremely difficult to be measured using the up-to-date experimental techniques. In\nthis study, a numerical simulation procedure based on computational fluid dynamics (CFD) was elaborated in order to obtain the\nfully three-dimensional unsteady turbulent flow field in an axial-flow water pump. The shear stress transport (SST) k-? model\nwas employed in the CFD calculation to study the unsteady internal flow of the axial-flow pump. Upon the numerical simulation\nresults, the characteristics of the velocity field and pressure field inside the impeller region were discussed in detail. The established\nmodel procedure in this study may provide guidance to the numerical simulations of turbomachines during the design phase or\nthe investigation of flow and pressure field characteristics and performance. The presented information can be of reference value\nin further optimal design of the axial-flow pump....
Nanoparticle-based planar laser scattering (NPLS) experiments and large eddy simulation (LES) were launched to get the fine\nstructure of the supersonic planar mixing layer with finite thickness in the present study. Different fromthe turbulent development\nof supersonic planar mixing layer with thin thickness, the development of supersonic planar mixing layer with finite thickness\nis rapidly. The large-scale structures of mixing layer that possess the characters of quick movement and slow changes transmit\nto downriver at invariable speed. The transverse results show that the mixing layer is strip of right and dim and possess 3D\ncharacteristics.Meanwhile the vortices roll up fromtwo sides to the center. Results indicate that the higher the pressure of the high\nspeed side is, the thicker the mixing layer is. The development of mixing layer is restrained when the pressure of lower speed side\nis higher.The momentum thickness goes higher with the increase of the clapboard thickness. Through increasing the temperature\nto change the compression can affect the development of the vortices. The present study can make a contribution to the mixing\nenhancement and provide initial data for the later investigations....
Some mechanical systems, such as steering, brakes, and suspension, critically affect the safety of the vehicle. These systems are\nsubject to wear through use and time, changing their status throughout the lifetime of a vehicle. It is, therefore, essential to develop\nadequate components and procedures of inspection that ensure the correct operation of these systems. Moreover, the steering\ninspection must guarantee certain requirements, such as, being able to test any vehicle steering system and being low priced. In\naddition, one of the most important requirements for any inspection procedure is to provide the measurements in a short time.\nThis fact conditions the measurement process and sensors to be employed. The current steering system that measures the steering\nangles is time consuming. The aim of this research is to introduce a steering system inspection based on forces measured by means\nof a dynamometer plate. The main features of the proposed system ensure minimum testing time, and simple operation and avoid\nmanipulation of the vehicle. In addition, precise and objective limits for acceptance and rejection have been established.Therefore,\nthe proposed procedure meets all the requirements for the periodic motor vehicle inspection (PMVI)....
The effect of film cooling parameters on the cooling effectiveness of an actual turbine blade is studied numerically. Film cooling\nparameters such as the hole shape, holes distribution, blowing ratio, stream wise angle, and span wise angle are investigated to\nselect the appropriate cooling parameters. Unstructured finite volume technique is used to solve the steady, three-dimensional, and\ncompressible Navier-Stokes equations. Using one cooling holes array indicates that the average overall film cooling effectiveness is\nenhanced by decreasing the stream wise angle for high blowing ratio on the suction side of the turbine blade. The film cooling\neffectiveness is enhanced on the pressure side for a blowing ratio of unity. In addition, the cooling effectiveness increases by\nincreasing the lateral and forward diffusion angles. The computations reveal that the efficiency of cooling is decreased at the leading\nedge due to the large surface curvature of the blade. The presence of compound shape (span wise angle) enhanced the film cooling\neffectiveness on the two sides. Multistagger cooling hole arrays are investigated and the results indicate that five-stagger cooling\narrays on the pressure side and three-stagger cooling arrays on the suction side with LFDCA-9.3-14.6 hole shape are enough to have\ngood cooling of the two sides using 2.17% bleed air of the engine....
The dimpled fin has excellent heat transfer performance and has attracted a lot of attention to apply on the fin and tube heat\nexchanger. A study presents to investigate the effects of number of tube rows on the air-side heat transfer characteristics of dimpled\nfin for velocity ranging from 1 to 3 m/s. The Q/?P andQ/((?P Ã?â?? V)) are used to evaluate the heat transfer performance of the\nheat exchanger. The results show that the dimpled arrangement can change the mainstream direction, increase the disturbance,\nand enhance the heat transfer.With the increase of the number of tube rows, the average Nusselt number decreases and Q/?P and\nQ/((?P Ã?â?? V)) increase gradually. Compared with the multipipe tube rows, the performance of two-row tube is better....
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