Potential of scallop bionic damper seal to improve rotor axial force and thermal management in compact turbomachinery unit

For the radial turbomachinery, the aerodynamic loads acting on the impeller cause axial forces on the rotor system, which may lead to bearings overload failure. To reduce the axial force, a compact design with the compressor and turbine impellers coaxially opposed has been proposed, but the problem of bearing overheating still exists. In this research, a balance piston is designed for a compact Turbine-Compressor (T-C) unit, and the scallop bionic damper seal (SDS) is developed as the piston seal. The high-pressure fluid flows through the clearance between the balance piston and the SDS, creating the differential pressure to balance axial force. The throttled leakage flow facilitates the reduction of downstream bearing temperatures for improved thermal management of the T-C unit. The potential of this novel design to improve the axial force and thermal management of the T-C unit under different operating conditions is experimentally investigated. The results indicate that the balance piston can effectively improve the axial force under the start-up and speed-up, variable and design condition, and off-design condition of the T-C unit. Under inlet pressures of 4–6 MPa, the leakage flow from the SDS facilitates the lower downstream bearing temperatures. The relative cooling capacity is defined to analyze the SDS and balance piston to improve the thermal management of the T-C unit.