The Rapid Hot Air Cooling Method Research With Temperature And Flow Rate Variable Device For Steam Turbine

As the rapid development of power industry, thermoelectric generating set with largercapacity and higher parameters that obtain a good economical benefit has been used widelyand play more and more important roles in Power Grid. In the present power market situation,every power plant pays close attention to the issue that how to safely shorten the downtimewhen large steam turbine is in maintenance. The hot air cooling method is recognized as acooling scheme in power generation industry. But because the traditional chilling temperatureand flow of air cannot control, large investment, high energy consumption and the worsecooling effect, most power plants use accelerate cooling method unusually even abandon thismethod. So designing the new, programmable, energy saving and rapid cooling equipmentand researching the cooling scheme that has best cooling effect and high safety become themost urgent problem pressing for solution in power generation industry.The new hot air production device is designed to overcome some disadvantages that thetemperature and flow can not be controlled. This new device consumes gas instead of electricand applies a programmable controller to control the gas consumption precisely, so it canadjust successive and satisfy the flow and temperature request for turbine.According to this new hot air cooling device, it offers a sub-interval cooling method thatthe cooling system is divided into several sectors and the new hot air cooling device provideshot air with different temperature in each sector. It analyzes the rapid cooling affection whichis included the sector width, flow and the temperature gap between turbine and hot air. Then itobtains the following results:1) when the flow is fixed, the cooling time reduces as the sectorwidth decreasing;2) the cooling time increases when the temperature gap reduces;3) whenthe temperature gap and sector width is fixed, the cooling time reduces as the flow increasing.Based on the abouve analysis, it offers the optimal cooling method that the temperature gap is50℃, and the sector width is5℃. Newton’s iterative method is applied to calculate theoptimal hot air flow. At the beginning of cooling, the flow is33.1m3/minand then the flowincreases to73.4at the end of cooling. The new hot air cooling device consumes gasinstead of electric and applies programmable controller so it can control the flow andtemperature precisely. If the program is set in advance, it can accomplish the optimal cooling.Ansys software is used to calculate the turbine temperature field with traditional and newcooling method in order to research the turbine temperature change and the temperature gapof some key parts. The temperature gap between upper and lower cylinder is23℃and the temperature gap between inside and outside cylinder is11℃while the cooling time is27.2h.Comparing with the traditional cooling method, the new one enjoys the following advantages:rapid cooling speed, low temperature gap between upper and lower cylinder as well as thetemperature gap along the turbine reducing, so it is a reasonable method for rapid coolingsystem.