As an important type of dynamic seal in power-shift steering transmission,accurately evaluating the sensitivity of power loss of expansion ring seal under various parameters is of great significance for transmission design and performance evaluation.In order to study the influence of different factors on the power loss of expansion ring seal,a computational fluid dynamics model of expansion ring seal was established,and the flow characteristics of the expansion ring seal were studied by the laminar model.The influence of pressure,speed and temperature (dynamic viscosity) on the power loss and leakage of expansion ring seal was analyzed,and the orthogonal experimental design was used to analyze the sensitivity of the factors of power loss and leakage.The results show that the most power loss is produced in the main sealing surface.The leakage is mainly caused by the expansion ring incision and the grooves under the differential pressure.There is a parabolic relationship between the power loss and the rotational speed,and a linear increase relationship appears between the power loss and pressure,dynamic viscosity.Meanwhile,a linear decrease relationship between the leakage and the rotational speed,a linear increase relationship between the leakage and pressure,and an inverse relationship between the leakage and dynamic viscosity can be observed.The influence degree of the three factors on power loss is as follows:dynamic viscosity,rotational speed and pressure.The influence degree of leakage is as follows:dynamic viscosity,pressure and rotational speed.