COMPRESSOR THRUST BEARING SURGE PROTECTION

摘要

The present invention provides a method and apparatus of inhibiting a thrust bearing capacity of a compression system from being exceeded during a surge event in which a thrust bearing is biased with a biasing force to increase the thrust bearing overload margin between the capacity of thrust bearing to absorb axial forces and the greatest force produced during the surge event. This biasing force can be produced by appropriately sizing the high pressure seal on the side of the impeller opposite to the inlet of a compressor of the compression system so that the back disk force produced in the high pressure region of the high pressure seal and the low pressure region located inwardly of the high pressure region creates the desired bias force value and direction.

主权项

1. A compressor system with thrust bearing surge protection comprising:
a first compressor having a first compressor shaft and at least one impeller; a second compressor having a second compressor shaft and at least one impeller; a motor shaft directly coupled to the first compressor shaft and the second compressor shaft; an electric motor configured for driving the motor shaft and the at least one impeller of the first compressor and the at least one impeller of the second compressor through rotation of first and second compressor shafts; a thrust bearing coupled to the motor shaft between the at least one impeller of the first compressor and the at least one impeller of the second compressor, the thrust bearing having a first thrust bearing capacity to absorb axial loads acting upon the thrust bearing in a first axial direction and a second thrust bearing capacity to absorb axial loads acting upon the thrust bearing in a second axial direction opposite to the first axial direction; and wherein the thrust bearing is biased with a preloaded biasing force acting in the first or second axial direction such that in a two-phase surge event characterized by an initial phase where the sudden loss of discharge pressure causes the flow rate to fall below a minimum flow required at a given speed of the at least one impeller such that a back disk pressure greatly exceeds an eye-side pressure of the at least one impeller to produce a large axial force driving the at least one impeller towards an inlet and a subsequent phase where the back disk pressure is reduced below the eye side pressure of the at least one impeller, resulting in the eye side force rapidly overcoming the back disk force to produce an axial force driving the at least one impeller away from the inlet, and wherein the force associated with the initial phase of the two-phase surge event is partially offset by the preloaded biasing force; and wherein the first thrust bearing capacity to absorb axial loads acting upon the thrust bearing in the first axial direction relative to the preloaded biasing force is greater than the second thrust bearing capacity to absorb axial loads acting upon the thrust bearing in the second axial direction relative to the preloaded biasing force.