A Short Story on Turbine Cooling Air Optimization
Mitsubishi Power, Ltd.
Industry: Electric Power Generation

A Short Story on Turbine Cooling Air Optimization

BACKGROUND

The operator of a power plant found the Rotor Cooling Air (RCA) temperature to be always on the high side during hot summer months due to degradation of its cooler system and this usually triggered the alarms to drop the plant performance that diminished financial returns.

THE PROBLEM
Action taken to counter high RCA temperature in summer was causing efficiency to drop in winter.

The power station engineers were worried that RCA could become so hot that the safety thresholds would be exceeded. This resulted that they could not achieve full performance in summers to avoid the risk of damage to the turbine components. One engineer recalls:

“Management was worried that compromising plant output in summers would be very unfavorable for our overall profit return, especially at a time when power demand is excessive due to air-conditioner use. During the discussions, engineers came to focus on the fans used to cool the RCA and we looked into upgrading these fans to better cooling.”

However, this solution might lead to overcooling during winter months which made it impossible to find a compromise between summer and winter months operation. Relatively inexperienced in this particular problem, the engineering team could not come up with a comprehensive solution within the requested time frame.

THE PROBLEM
The high temperature of RCA caused that the generator could not achieve full performance in the summer months to avoid the risk of the turbine damage, thereby resulting in a decrease in electricity generated.
While the engineers discussed upgrading to a fan with higher cooling performance to lower the temperature of the RCA, this approach would have caused relatively excessive cooling in winter months, and would therefore not allow them to optimize gas turbine performance.

Mitsubishi Power, as one of the core subsidiaries of Mitsubishi Heavy Industries group, offers generation technologies and solutions.

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