Turbine efficiency and thermal balance

In the program module of turbine efficiency the turbine thermal balance is calculated, including the regeneration system. For condensing turbines, the balance includes the condenser with the cooling water system; and for district heating turbines the balance of heat exchangers and the heat export system.

 

 

The module makes calculations for:

 

• steam turbines
• back pressure extraction turbines
• condensing turbines
• gas turbines
• steam and gas systems

 

 

Graphics of a back pressure turbine with bleeding

 

 

Temperature versus entropy

 

 

The program for calculating the efficiency is based on having knowledge of enthalpy and entropy at the inlet and outlet of each turbine stage. For turbines where - in some extractions - wet steam with a degree of unknown steam quality, the program - based on the available measured values - systematically defines the steam expansion curve and determines all the necessary parameters for the whole turbine flow path. The output parameters – those that are exported to the database as a result of the turbine-generator – set calculations for internal efficiency of the HP, IP and LP parts, thermal power in characteristic points of the flow system and the mechanical power at the shafts of the HP, IP and LP parts, thermal power in the steam from each turbine extraction, the electrical power generated in cogeneration and in the condensing mode, electrical and thermal power of auxiliaries used for production of power, heat and general needs, net and gross efficiency of energy generation, and heat and power cogeneration ratio.

 

 

Enthalpy versus entropy

 

 

The program module for turbine efficiency calculations presents the following additional information, which may be significant for the operating personnel in the power plant:

 

• The steam path expansion line in the turbine flow path. This enables its current operational conditions, the throttling degree in the control valves and the IP valves, along with the ventilation effect of the final stages, etc. to be evaluated.
• Efficiency variation history. This is the course of efficiency within the last 8 hours - visualised in order to show the correlation between the initiated changes of operation conditions and the efficiency.
• The efficiency deviations from its design value - which have occurred as a result of deviations of the actual operating conditions from the design conditions.
• Sensitivity of efficiency to the operating parameter changes. This is the magnitude of efficiency change caused by a change in a certain physical parameter. The operators are aware of the current impact of, for example, the incoming steam temperature and pressure, a vacuum in the condenser, condenser surface contamination, heat exchange in the regenerative heaters, or a pressure drop at IP valves (in CHP plants) on the efficiency.

 

 

The steam parameters and the parameters of streams of steam, water, condensate and drip as determined by calculations enable all the parameters needed for making reports as used in power industry statistics and in the production planning, to be calculated. The explicit presentation of the dependency of efficiency on key factors allows the operators to solely optimise operations.

 

 

download brochure "Turbine Efficiency and Thermal Balance" (0,4 MB)