Questions about centrifugal compressors
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Why does the exhaust temperature of the turbine increase when a centrifugal compressor driven by a turbine operates at low speeds? Experts in compressors, please give some advice. Thank you
At low speeds, the turbine generates less power; the thermal energy of the steam cannot be fully converted into mechanical energy, which causes the exhaust temperature of the turbine to rise
1 Like other rotating machinery, steam turbines also have efficiency curves. Since the turbine structure has been determined, it performs well in terms of energy conversion when operating in the designed high-efficiency range; however, it operates in a low-efficiency range when running at low speeds. 2 Use a set of simulated data to illustrate this: Assume that the steam inlet pressure is 3.0 MPa, the inlet temperature is 350 degrees, and the outlet pressure is 1.0 MPa; under these conditions, the exhaust steam temperature at an efficiency of 80% is 233 degrees. When the efficiency drops to 75%, the exhaust temperature rises to 238 degrees.
There are two reasons: (1) At low speeds, the turbine generates less power; the thermal energy of the steam cannot be fully converted into mechanical energy, which causes the exhaust temperature of the turbine to rise； (2) At low speeds, the blowing loss of steam is severe, resulting in an increase in the temperature of the exhaust cylinder. For gas-condensing turbines, it generally does not exceed 120 degrees ；
Low-speed operation can be achieved by reducing the temperature and pressure of the steam.