Low-speed Dynamic Characteristics Of The Spiral Groove Gas Film Face Seals

Abstract The shutdown period is the reverse of the startup period.The startup process can be divided into two distinct periods: (1) from contact to just un-contact period; (2)from just un-contact to steady period. (1) from contact to just un-contact period is extremely short, lasting only about 55ms. During this period the film thickness increases slightly from 3.5^σ_s to 5^σ_s, where^σ_s is the average value of surface roughness, the contact force f_c decreases rapidly. Since the contact factional torque T_q is a linear function of the contact force f_c, so T_q decreases close to zero very rapidly. The existed friction force is only the internal friction of the gas film .Leakage rate Q increases as the film thickness increases, and power loss W also increases as the rotates speed up slowly. (2) from just un-contact to steady operation period. The value of contact force f_c is zero because of seal faces separation, the frictional torque T_q and power loss W increase smoothly owing to rotational acceleration. Along the further separation away from each other, the film thickness will increase gradually and eventually reach the maximum, and so does the leakage rate Q. Researched results show that when the following conditions are satisfied(16⁰≤α≤20⁰,2.5μm≤h_g≤3μm,10≤N_g≤30), the seal dynamic characteristics will be good. The operation conditions will also have influence on the dynamic behaviors.