Study On The Effect Of The Supply Opening Conditon On The Flow Field Characteristics Of Push-pull Ventilation System

With the development of modern industry, pollutants emitted from industrialbuildings during production increase rapidly. There is a wide variety of pollutants whichhave a huge burst size and also contain toxic characteristics. If these contaminants arenot effectively controlled and trapped, it will be harmful for the health of workers, theoperating environment and the atmosphere. According to the features for thedissemination of pollutants in industrial buildings, the most effective control method islocal exhaust systems. Push-pull ventilation system，which is a kind of typical localexhaust ventilation system for industrial buildings， is widely used in the actualproduction process. This kind of ventilation system in the form of a jet of air power,control contaminants and transport them to the nearby air exhaust, with the supply air,achieving effective control of pollutants. As power source of suction flow, the air jet hasan important impact on the distribution of suction flow field. How to slow down the jetdecay and extend transmission distance to barrier more effectively contaminants iscritical to control ventilation systems. Therefore, this paper is mainly about the mainfactors affecting the development of air jet-the flow uniformity, direction, turbulenceintensity and temperature, analyzes the rule of push-pull ventilation under differentfactors. And it explores the impact of the air terminal devices and cellular devicesstructural parameters on the air supply outlet characteristics, hoping to provide somereference value to design the supply air terminal of ventilation system.Firstly, against the vacuum blower flow field under isothermal jet effect, this paperanalyzes the rule function of flow uniformity, direction and turbulence, the result shows that the inconsistent jet direction or increasing turbulence will decrease the ventilationsystems trap efficiency by7.5%-19.5%, which illustrate the consistency of air jet andsize of the turbulent have a great influence on the direction of the push-pull ventilationflow field.Secondly，Based on the error analysis of equal ratio experienment, this paperfocuses on the influence of the honeycomb structure on discharging characteristic withcomputational methods. It was found that honeycomb can improve the flow directionuniformity of the outlet obviously. Increasing the length of the honeycomb ordecreasing the opening dimension of honeycomb leads to the flow direction uniformityincreased and turbulent intensity decreased.According to analyzing the resistancecharacteristics of different honeycomb structure in variationalflow rate, the risistanceloss of unit length was found increased with the length of the honeycomb increasedand decreased with the opening dimension increased. Furthermore, recommendedparameters of the honeycomb for engineering practice are proposed.Lastly, analysising the flow field characteristics of push-pull ventilation under thenon-isothermal jet,and analysising the axis speed、axis temperatu、Offset distance ofsupply jet in different supply air temperature; furthermore,increasing the supply airvelocity, reducing the buoyancy lift and inertial force ratio, to increase the captureefficiency of the push-pull ventilation tracer particles. The study found that, when thetemperature of supply air is different to the temperature of surrounding environment, thedesign parameters of L.Hayashi classic flow ratio method was not suitable fornon-isothermal jet. Therefore, to improve the design parameters, when the supply airtemperature difference is8K, Ar is0.154, the radio of supply air to exhaust air is0.325,capture efficiency is99.8%. Compared with the original design parameters, both thesupply and exhaust air flow rate increasing to the power of5/3, a good control effect isobtained.