Experimental study of gas-dynamic bearing operability

The question of the high-speed turbo machines operability is directly related to the processes occurring in the support structures - gas sliding bearings. The most common structure of such supports is the multi-petal bearing. One of the main research directions in this area is the development of a design ensuring the reliable operation of the bearing. The durability of gas bearings depends directly on the number of start-stop cycles, which is its key difference from liquid bearings. The start-up period of the turbo machine represents the most challenging mode of operation for the petal gas dynamic bearings. A critical feature of this mode is the insufficient formation of a gas layer at low rotational speeds. The load on the working surfaces of the support is assessed as nominal, equal to the rotor's weight. If the start-up mode of the turbo machine is successfully passed, then in future, during the acceleration, it will be operational. The research of the transitional mode during the start-up requires a complex approach, including both theoretical and experimental studies. This paper is a continuation of theoretical studies for multi-petal gas dynamic bearings with overlapping petals. The key parameters ensuring the operability of such supports include the shaft ascent speed at the start-up and the value of the force acting on the support. As part of the research, an experimental installation was developed to obtain values of shaft ascent speed depending on static load force. Series of experiments included different variations of initial loads, up to the critical value. The results of the experiments provide the values of permissible static loads and a range of shaft ascent speed values. This study facilitates further parametric investigations in the mathematical modeling of processes occurring in gas dynamic bearings.