Conjugate Mixed Convection in a Differentially Heated Lid-Driven Square Cavity With Rotating Cylinders

Conjugate mixed convection in a lid-driven differentially heated square cavity with two heat-conducting rotating cylinders is numerically investigated. The right and the left walls of the enclosure, respectively, are maintained at a constant higher temperature (Th) and lower temperature (Tc), keeping the horizontal walls adiabatic. Both the cylinders are rotating in the counterclockwise direction. Only the left wall is moving downwards with a constant velocity. The governing nondimensional partial differential equations are resolved by means of Galerkin weighted residual finite element formulation. The average Nusselt number (Nu) is calculated along the right vertical heated wall. Flow and thermal fields are presented via streamlines and isotherms. Parametric simulations are performed for various pertinent parameters which are Grashof number (Gr), Reynolds number based on lid velocity (Re), Reynolds number based on cylinders’ peripheral velocity (Rec), and Richardson number (Ri). At first, the effects of variation of cylinders’ diameter are observed by considering six different cases for a particular peripheral velocity. It is found that the maximum Nu is obtained when the diameters of both cylinders are 0.1L. Further simulation is done for varying the Rec in the range of 5 to 50, to observe the effect of cylinders’ rotational speed. It has been found that for a particular Re, Nu increases with increasing rotational speed, but the effect is more pronounced at low Re. Finally, the combined effects of both Re and Gr on Nu have been investigated, keeping the Ri in the laminar mixed convection region. It has been demonstrated that when the Ri is increased from 0.1 to 10, the Nu enhances about 395.7%.

Study of Different Operating Parameters on Seed Holding in the Single Seed Metering Unit

Aims: The present study was conducted to determine the “Effect of Different Operating Parameters on Seed Holding in the Single Seed Metering Unit”. Study Design: An attempt was made to development seed metering unit and evaluated for its performance with battery drive i.e. seed rate, seed holding ratio, single seed holding ratio, double seed holding ratio and missing index. The shapes of cells speed of seed plate and number of cells on seed plate were chosen as parameters. A factorial completely randomised design used for analysis of variance. Results: At the end of the research, it was found that the cell’s shape, peripheral velocity and number of cells on seed plate had an effect on the seed holding ratio (SHR) at a significant level of 5% (P<0.05). The diameter and thickness of the seed metering plates were 100 and 8 mm respectively. The hopper was of the trapezoidal section with height of 12.5 cm , volume 3510 cm3 and thickness of material of 2.5 mm. For maize seed variety: Tulasi Naga If the velocity of seed plate increases then seed holding ratio decreases, seed holding ratio also decreased with increase in number of cells on seed plate. Oblong shape with extension was suitable for these seeds. For maize seed variety: Goodrej Ultra when the velocity of seed plate increased then seed holding ratio decreased, seed holding ratio also decreased with increase in number of cells on seed plate. Oblong shape was suitable for these seeds. For maize seed variety: Laxmi 2277 seed holding ratio increased with increase in velocity of seed plate, seed holding ratio also increased with increase in number of cells on seed plate. Oblong shape was suitable for these seeds. Conclusion: The highest and least value of seed holding ratio is 94% at a speed of 30 rpm in shape 2(6 and 7 cells) and 31% at a speed of 30 rpm in shape 1(7 cells), 39% at a speed of 26 rpm in shape 2(6 cells) and 12% at a speed of 30 rpm in shape 1(7 cells), 45% at a speed of 26 rpm in shape 1(6 cells) and 6%at a speed of 30 rpm in shape 2(7 cells) for laxmi, goodrej and tulasi variety of seeds respectively.

Research on ELID Grinding Performance of GCr15 Steel

The electrolytic in-process dressing (ELID) grinding technology was adopted for ultra-precision grinding experiments of GCr15 bearing steel. The experiments show that: grinding depth, electrolysis gap and wheel peripheral velocity are the main factors to affect the surface quality. With the electrolysis gap of 0.5mm, the grinding depth of 0.1μm, and the wheel peripheral velocity of 18m/s, the grinding effect can achieve optimal and the machined surface roughness can obtain Ra0.006μm.

The Research of ELID Grinding Effect and Surface Quality on Carbonized Cold-Rolled Steel

In this document, the electrolytic in-process dressing ( ELID ) grinding technique is used for ultra-precision processing experimental research on the carbonized cold-rolled steel (HRC60～80).A surface roughness of Ra6～8nm was obtained after ELID precision grinding. The results proved that adopting micro grain size (W1.5～W36) and high hardness cast iron based diamond grinding wheel, increasing the wheel peripheral velocity (18～20m/s) and reducing grinding depth can effectively improve surface quality and bring the surface roughness down. The wheel peripheral velocity, grinding depth as well as grinding fluid are the main factors during ultra-precision grinding.

Theoretical Investigation on Flow Rate at the Maximum Efficiency Point in the Design of Impeller Blade in Centrifugal Pump

This paper presents a theoretical investigation of the flow rate at the maximum efficiency point in the design of impeller blade in centrifugal pump. An energy balance was performed at the trailing edge of impeller outlet in the rotating flow passage of centrifugal pump. The evaluation shows that, when the fluid particles straight forward tangential velocity is one third of the impeller blade’s peripheral velocity and the fluid particles circular forward tangential velocity is two third of the impeller blade’s peripheral velocity at the trailing edge of the impeller outlet, the maximum hydraulic energy output, that is, the maximum efficiency point is obtained.

Flow Control of Rotating Stall in a Radial Vaneless Diffuser

The instabilities of a backflow layer on a diffuser wall and the main flow with vorticity have already been shown theoretically to cause the occurrence of rotating stall in a vaneless diffuser. These instabilities, however, have not yet been proven to exist experimentally. This study was carried out to examine the factors contributing to the occurrence of rotating stall using a jet installed in a diffuser. Rotating stall was completely suppressed by a jet that was set in the direction opposite to the vector of the impeller peripheral velocity, and amplified by the jet set in the same direction as that vector. The effects of the jets were confirmed by the experiment using the jets installed at positions other than the neighborhood of the diffuser wall. The results suggest that the instability of the main flow contributes to the onset of rotating stall. The factors contributing to the onset of rotating stall and the effect of the jet on the performance of the impeller-diffuser combination are discussed.