Universal Modeling And Parameter Sensitivity Analysis Of The Induced Airflow Movement In Ultra-high-speed Elevator

Due to the development of high-rise buildings,the ultra-high-speed elevator with high speed and large travel has gradually been demanded by more and more people and enterprises.However,the high-speed development of the elevator also brings more obvious aerodynamics problems,which makes the ride comfort and operational safety of the ultra-high-speed elevator more serious.Due to the consideration of saving the building area and utilizing resources rationally,the hoistway is a narrow and long cylinder structure with a length-width ratio,so the piston effect is observable,resulting in more severe aerodynamic noise,wind-induced vibration and other problems.Although theoretical analysis is more difficult in the early stage of modeling,the efficiency of solution and analysis in the later stage is much higher than that of other research methods such as numerical simulation.Starting from theoretical analysis,based on Bernoulli's equation for unsteady flow,a universal theoretical model of the car-induced unsteady airflow with n(n ? 0)pairs of ventilation holes is established.The validity of the theoretical model is verified by experiments.Then,based on the verified universal theoretical model,the influence of the parameters of the hoistway and the ventilation hole on the car-induced unsteady airflow movement are analyzed respectively.This work provides important theoretical guidance for the follow-up scholars on the study of car-induced unsteady airflow in hoistway-like environment and the technicians on the opening of ventilation holes in the hoistway.And it serves as a more systematic and scientific theoretical basis for the study of aerodynamics problem in the hoistway of the ultra-high-speed elevator.Moreover,this work has greatly improved the lack of theoretical analysis of the unsteady air flow in the elevator field.Firstly,it was assumed that the airflow in the hoistway is viscous one-dimensional unsteady incompressible flow,and the effects of chimney effect and other components on the airflow in the hoistway were neglected.Further,considering the drag loss along the flow,the local drag loss and the work done by the inertia force,the origin of the Bernoulli's equation for unsteady flow was deduced in detail.Finally,based on the Bernoulli's equation for unsteady flow,the theoretical models of the whole process of airflow movement in three structures under the influence of piston effect were established respectively: the hoistway with no ventilation holes(HNVH),the hoistway with a pair of ventilation holes(HOVH),and the hoistway with two pairs of ventilation holes(HTVH).Secondly,through the analysis of the airflow movement law under HNVH,HOVH,and HTVH,the general influence law of the ventilation holes opening on airflow movement in the hoistway was summarized,and a universal theoretical model of the hoistway with n(n ? 0)pairs of ventilation holes on airflow movement was established.According to the physiological characteristics of the people and the actual running characteristics of the elevator in the test tower,the parabolic-linear elevator running velocity was determined.By means of the existing ultra-high-speed elevator test tower of the cooperative company,a hoistway air flow test platform for 4 m/s ultra-high-speed elevator was built,and the GM8903 thermosensitive anemometer was used to measure the wind speed at the outlet of the hoistway.In order to achieve better contrast validation effect,the parameters matching the 4 m/s ultra-high-speed elevator of the cooperative company were used as the input parameters of the universal theoretical model for theoretical solution,and the dimensionless comparison between the theoretical solution data and the experimental data was carried out to verify the validity of the theoretical model.This work provides an important basis for the analysis of the influence of the hoistway parameters and the ventilation holes parameters on the airflow movement.Thirdly,based on the universal theoretical model and the four order Runge-Kutta method,the effects of 4 main parameters of elevator speed,car height,blockage ratio and hoistway height on the car-induced airflow movement and ventilation rate in HNVH,HOVH and HTVH were analyzed respectively.Furthermore,considering the generality of the influence law of parameters and the simplicity and practicability of engineering,a general ventilation prediction formula under the influence of four parameters was proposed.The accuracy of the general ventilation prediction formula was verified by comparing with the theoretical results.The general ventilation prediction formula eliminates the cumbersome numerical solution process for technicians in engineering design of ultra-high-speed elevators,and greatly facilitates engineering technicians' data prediction in project design.Finally,based on the validated universal theoretical model of car-induced unsteady airflow,the motion characteristics of car-induced airflow in each section of HOVH and HTVH were analyzed respectively.On this basis,the effects of cross-sectional area,length and location of ventilation holes on airflow movement in HOVH and HTVH were analyzed respectively.Subsequently,motion laws of piston wind and lateral wind in HNVH,HOVH and HTVH were analyzed respectively,and the influence of the opening number of ventilation holes on the airflow movement in the hoistway was summarized.Analysis of the influence rules of ventilation parameters provides an important theoretical guidance for technicians to open the ventilation holes of the hoistways in ultra-high-speed elevators.