The transportation of high viscous oil surrounded by a water layer is one of the energy efficient technologies. In this study, the VOF, standard k−ε, and CSS models are performed to simulate the oil−water core annular flow across a Π bend, and the tendency of phase contour and phase fraction simulated appears reasonably consistent with the photo from experiments and the empirical correlation. The effects of input water fraction, the flow direction, the oil property, and the geometric parameters (include aspect ratio, diameter ratio, fillet radius, and roughness) on hydrodynamic performance and fouling characteristics are analyzed, and the results could provide a reference for designing the pipeline and optimizing operation conditions and the Π bend structures.
The oil‐water core annular flow through a U‐bend is simulated by computational fluid dynamics based on the Eulerian model. More flow parameters and the effect of annulus thickness on core annular flow are discussed. Conformity between the simulated and experimental data is observed. The development of oil‐water core annular flow in the U‐bend is analyzed, and the distributions of pressure and velocity are discussed. Results of the Eulerian model and volume‐of‐fluid (VOF) model are compared and the influence of oil properties on total pressure gradient is investigated. The suitable range of annulus thickness is identified. The results provide suitable operation conditions for designing the U‐bend pipefitting.
Control for the HEV propulsion system based on dynamic processes is proposed. Parameters of the controller are optimized in order to optimize the dynamic characteristics. For the purpose of solving the problem that the energy consumption will increase while the dynamic characteristics are optimized, fuzzy control is put forward for the HEV. The dynamic characteristic is than improved, and the output required from the engine and motor will not go beyond their ability, which allows the optimized target of the control strategy to be implemented.
Abstract. Clean gas engines, such as liquefied petroleum gas (LPG)
engines, have high thermal loads on parts under equivalent specific
combustion. This study examines the multi-field coupling enhanced heat
transfer principle and its applications to the engine compartment of a
typical LPG city bus. The field synergy enhanced heat transfer principle
(FSP) was applied in the radiator assembly area. The FSP model yielded an
optimum velocity -temperature gradient matching field that would improve
convective heat transfer in this area. To strengthen the convective heat
transfer ability of the limited cooling air in the cabin, temperature field
homogenization (TFH) in the core flow region of the engine block area was
achieved. The TFH optimization model helped minimize the temperature
gradient in the core flow region and maximize it at the heat transfer
boundary, and the optimum vector field and flow path were obtained. More
comprehensive changes to the structural design were made according to the
multi-field coupling enhanced heat transfer principles. The simulation
results showed that in the comprehensive structure, the heat transfer
efficiency of the radiator increased by 14.66 %, the average temperature
of the air passages in the engine block area decreased by 22.23 %, and the
heat dissipation coefficient of the engine body and engine cover increased
by 4.60 times and 3.49 times, respectively.
In order to improve the performance of emitter, the extenics theory is introduced, whose divergent thinking is used to resolve the conflict of anti-clogging and energy dissipation and a new structure is proposed. The wide triangular areas are designed to reduce the flow rate behind of the each orifice and be easy to precipitation of impurities. The orifices are set to gradually decrease water kinetic energy and the flow channel is designed to be dismantle. The numerical simulation technology is used to analyze the internal flow field of emitter, the flow field results show that the improved emitter has great effect of energy dissipation and anti-clogging. As the same time, the structure of emitter is optimized and L1 = 31 mm, L2 = 21 mm, L3 = 8 mm and L4 = 5 mm are the optimization size values.
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