Study On The Vertical Convective Urban Vortex Engine

With the increasing severity of urban air pollution and the accelerating pace of urbanization,more and more attention has been paid to the prevention and control of urban air pollution.In order to alleviate the"urban heat island effect",this paper presents a vertical convective urban vortex engine system.We establish a reduced scale model and the numerical simulation to find out the system's ability in strengthening the vertical convection in urban and speeding up the atmospheric circulation of the city and weakening urban heat island effect.The following conclusions are obtained:?1?Experiments are carried out on the vertical convective vortex engine system test bench constructed according to the geometric similarity.The results shows that heating the bottom and using the buoyancy of hot air flow as the main power of the vortex engine can form a tornado vortex.A numerical model was established and comparing simulation results and experimental measurement data show that:the simulation results can correctly reflect the experimental flow field conditions,and most errors can be maintained within10%,mainly due to the thermal insulation between the bottom heating source and the surrounding wall surface cannot reach the ideal state and the flow field of the experimental bench is affected by the outside air flow.The results show that the simulation results can accurately reflect the changes of various parameters in the experimental flow field.?2?Using numerical simulations,an orthogonal numerical test was established for the size of the vortex stable room and the vortex stable room entrance width.The effect of these two parameters on the vortex structure was investigated.The results show that the entrance width has the greatest effect on the vortex.Using numerical simulations for comparative experiments,it is known that as the entrance width of the vortex stable room increases,the pressure in the vortex center decreases,and the inlet mass flow increases,the vortex strength of the exit increases first and then decreases,it reaches the maximum at the entrance width of 50 mm,and the optimal result for the entrance to the stable room is obtained.The experiment is used to verify that the results show that when the entrance of the stale room is 50 mm and 10 mm,the vortex structure is stable and can maintain a height of 40cm.It is the highest vortex group in all experimental models.Therefore,it is considered that when the stability chamber inlet width is 50mm,that is the ratio is 1/6,the structure of the vertical convection vortex engine is optimal.?3?The similarity theory validates the similarity between the experimental flow field and the real flow field.Based on the measurement results,it is calculated that the difference between the heat source temperature and the ambient temperature required to maintain stable vortex is5.1×10^-4?,which proves that the vortex engine is able to pump air spontaneously without the need of external heat source after the vortex is generated.According to the optimization results,the structure of the urban vertical convection vortex engine system is designed.The results show that the average velocity is 1.0 m/s and the mass flow reaches 1058t/h in the entrance of vortex generator,the transport height of air is700m.It is considered feasible to establish a vertical convective vortex engine system in the city center.