Koki Kishinami, Hakaru Saito, Jun Suzuki, Ahmed Hamza H. Ali, Hisashi Umeki and Noriyuki Kitano
Combined forced and free laminar convective heat transfer on a vertical plate with a backward‐facing step has been studied numerically and experimentally, considering the effects…
Abstract
Combined forced and free laminar convective heat transfer on a vertical plate with a backward‐facing step has been studied numerically and experimentally, considering the effects of the interaction between the buoyancy and inertia forces which play a significant role in this phenomenon with the step‐geometry factor of d/L. The convective heat transfer behavior in connection with the reattachment and recirculation flows appearing in the step region has been investigated based on the numerical calculations and Mach‐Zehnder interferometer measurement under the wide range of the thermal condition. The behaviors of local Nusselt number NuL, velocity and temperature boundary layers and streamline fields in the recirculating region have been discussed for the various parameters of Grashof number GrL, Reynolds number ReL and the geometry factor d/L. The characteristic behavior of this convection heat transfer, including the vortex flow mode in the recirculating region and the unstable fluctuating mode near the reattaching point appearing at the specific condition, has been clarified numerically and experimentally by introducing the generalized coupling parameter GrL/ReL2 and geometry factor d/L.
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Ye Hong, Yimin Mo, Jun Wang, Xiangkui Kong and Qingchun Liu
This paper aims to investigate the effects of low-viscosity and ultralow-viscosity engine oils on the comprehensive friction and fuel economy of turbocharged gasoline direct…
Abstract
Purpose
This paper aims to investigate the effects of low-viscosity and ultralow-viscosity engine oils on the comprehensive friction and fuel economy of turbocharged gasoline direct injection (TGDI) through simulation analysis and experiments.
Design/methodology/approach
Numerical analysis models of friction loss for reciprocating, crankshaft and valve train are established. Based on the FAST, the friction loss of 24 specific parts of a TGDI engine was analyzed. Finally, the engine test bench was built, which was used to test the mechanical loss, external characteristics and universal characteristics.
Findings
Compared with the baseline oil, lower viscosity lubricating oil can reduce the friction loss of nine components to varying degrees. When the viscosity decreases, the friction distribution ratio of reciprocating, crankshaft and balance shaft will gradually decrease. The proportion of reciprocating when using 0W12 is reduced by 4%. Tests have shown that ultralow viscosity engine oil reduces torque loss by up to 15.74% (2,000 rpm, full throttle), but its fuel consumption rate becomes higher in low-speed and high-torque conditions.
Originality/value
This work helps to understand the effect of lubricating oil characteristics on the comprehensive friction performance of the engine.