Study On Internal Flow And Exhaust Pulsation Of Roots Blower Based On CFD

Roots blower has been widely used in the field of ventilation and gas transmission because of its simple structure and high reliability.However,because there is no internal compression in its working process,the exhaust pulsation and additional aerodynamic noise caused by under compression reflux severely limit the application of Roots blower in a wider field.This paper presents a numerical simulation of the internal flow field of Roots blower using 3D dynamic grid technology based on CFD,with a detailed analysis of its internal leakage and exhaust pulsation characteristics.This study examined the difference in leakage characteristics of Roots blower obtained through mathematical method,steady-state simulation,and non-steady-state simulation,and explains the errors caused by dynamic inlet and exhaust pressure.Furthermore,the study analyzes the exhaust pulsation characteristics and their impact on the flow field,and suggests a parallel method to reduce the amplitude of exhaust pulsation in pipelines.The main conclusions are:(1)The reflux in the exhaust process of Roots blower will interfere with the exhaust pressure pulsation and produce several sub-pulsations.Both the reflux and inter-stage leakage will greatly disturb the internal flow field.The internal clearance leakage of Roots blower presents a certain rule with the rotation of the rotor,and the leakage under unsteady calculation is smaller than that under theoretical calculation.(2)The exhaust pressure pulsation phenomenon of the exhaust pipe of Roots blower will be attenuated with the increase of the distance of the exhaust pipe.For a specific Roots blower,at the speed of 1400r/min,the connection distance of Roots blower exhaust pipe at the parallel distance of 2.0m can attenuate the exhaust pipe exhaust pressure pulsation.The parallel connection of 1.5m has little difference with the effect of single stage,and the parallel connection of 2.5m increases the exhaust pipe exhaust pressure pulsation.According to this conclusion,for a specific speed,appropriate parallel spacing can reduce the exhaust pulsation in the pipeline,while improper parallel spacing will increase the exhaust pulsation,so that the interval of exhaust pulsation reduction will change with the speed change.