The internal flow and temperature rise characteristics in the last stage of steam turbine low pressure cylinder under low flow rate condition is quite complex

which makes thermal power peak load regulation and cutoff transformation more challenging. By taking the low pressure cylinder of a steam turbine in a power plant as the research object

a five-stage cascade single-channel calculation model of the low pressure cylinder was established

and the working performance

flow structure and temperature rise characteristics of the low-pressure cylinder under different working conditions were numerically investigated. The research shows that

when the flow rate of the lowpressure cylinder decreases to 3.84% of the design condition

the low-pressure cylinder outputs no positive power.When the flow rate is quite low

the low pressure cylinder enters the windage condition

and the flow structures such as the hub endwall separation area

the vane separation area

the casing torus vortex

and the last stage bucket vortex appear in the last stage cascade

by concomitant of obvious windage heating effect at the tip position of rotorstator clearance area of last stage cascade under low flow rate condition. When the flow rate decreases to 2.23% of the design condition

the average surface temperatures of the last stage vane and blade increase by 219.6 K and 243.7 K

respectively. The working performance and internal flow structure significantly change under windage condition. The temperature rise in the last stage cascade deteriorates the working environment of the blades

which needs to be taken into consideration when the steam turbine works under low flow rate condition.