Expander is a kind of equipment that uses the principle of mechanical work output when compressed gas expands and depressurizes to lower the temperature of gas. Expander is the key equipment to provide cooling capacity for air separation plant. The efficiency of expander directly affects the operation effect of air separation plant. The following introduces several factors that cause the efficiency reduction of expander.
1.Flow loss: the wear of the runner, the accumulation of impurities in the runner, and the impact of the flow into the impeller due to the change of rotating speed will increase the flow loss.
2.Friction loss of working wheel: when the working wheel rotates at high speed, the gas around the wheel disc rotates with the impeller to form friction force. The friction heat generated from this will increase the temperature of the gas and affect the operation efficiency of the expander.
3.Internal leakage loss: when the gap between the working impeller and the diffuser is large, part of the gas does not expand through the impeller after passing through the deflector, but directly leaks out from the gap between the working wheel and the casing, converges with the gas expanded through the impeller, and the temperature rises, resulting in the reduction of the cooling capacity of the expansion mechanism.
4.Exhaust loss: the gas passing through the expander also has a certain residual velocity at the outlet, and the higher the residual velocity, the greater the energy loss. The exhaust loss is not only related to the design, but also increases the velocity of the air outlet and reduces the efficiency when the speed variation deviates from the design condition during the operation of the expander.
