Abstract
The turbomachinery used in the sCO2 power cycle requires a high stable rotor-bearing system because they are usually designed to operate in extremely high-pressure and temperature conditions. In this paper, we present a pump-drive turbine module applying hydrostatic bearing using liquid CO2 as the lubricant for a 250 kW supercritical CO2 power cycle. This design is quite favorable because stable operation is possible due to the high stiffness and damping of the hydrostatic bearing, and the oil purity system is not necessary when using liquid CO2 as the lubricant. The pump-drive turbine module was designed to operate at 21,000 rpm with the rated power of 143 kW. The high-pressure liquid CO2 was supplied to the bearing, and the orifice restrictor was used for the flow control device. We selected the orifice diameter providing the maximum bearing stiffness and also conducted a rotordynamic performance prediction based on the designed pump-drive turbine module. The predicted Campbell diagram indicates that a wide range of operation is possible because there is no critical speed below the rated speed. In addition, an operation test was conducted for the manufactured pump-drive turbine module in the supercritical CO2 cycle test loop. During the operation, the pressurized CO2 of the 70 bar was supplied to the bearing for the lubrication and the shaft vibration was monitored. The successful operation was possible up to the rated speed and the test results showed that shaft vibration is controlled at the level of 2 μm for the entire speed range.
Highlights
Owing to stricter environmental regulations and energy depletion worldwide, the demand for power generation systems with higher efficiencies and reduced capital and operating cost has increased.With these aims, power cycle systems using supercritical CO2 have been examined as potential alternatives to conventional steam Rankine power cycle systems
The turbomachinery used in the supercritical CO2 (sCO2) power cycle is generally designed to operate in extreme conditions of high temperature, high pressure, and high speed; the bearings and the lubrication system require high reliability and stability
This study pertains to the development of a pump-drive turbine module for sCO2 cycle application with hydrostatic bearings using liquid CO2 as lubricant
Summary
Owing to stricter environmental regulations and energy depletion worldwide, the demand for power generation systems with higher efficiencies and reduced capital and operating cost has increased. The turbomachinery used in the sCO2 power cycle is generally designed to operate in extreme conditions of high temperature, high pressure, and high speed; the bearings and the lubrication system require high reliability and stability. San Andres proposed an approximate solution for the static and dynamic properties of hydrostatic bearings considering the flow inertia effect [18] He reported that approximate solutions show good agreement with the full numerical solution and that maximum direct stiffness occurs at pressure ratio of 0.6, and that maximum direct damping is present at different pressure ratios depending on the rotor speed. This study pertains to the development of a pump-drive turbine module for sCO2 cycle application with hydrostatic bearings using liquid CO2 as lubricant.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
