Study of the effect of operating conditions on the efficiency of the absorption-refrigerating system in gas turbine and combined-cycle plants

The study is aimed at analysing the operation of the absorption refrigerating system in gas-turbine and combined-cycle plants for cooling the air entering a gas turbine compressor during summer power limitations. In order to develop models of a combined-cycle power unit with and without the introduction of an absorption system into the circuit, mathematical modelling methods were applied using the Microsoft Visual Studio software package. An absorption refrigerating system was determined to be effective at ambient temperatures above + 15°C. At the same time, no costly modernisation of the gas turbine unit flow path is required. The dependences of the power on the temperature of the air entering the complex air-cleaning device were derived for the investigated models. It was shown that, when absorption refrigerating systems are used, the combined-cycle power unit can operate without deviations from the certified power of 110 MW under the conditions of summer technological limitations in electricity generation. The operation of the gas turbine at rated load minimises the alternation of temperature difference in the flow path, though contributing to an increase in the service life of the equipment and its operational reliability. For a combined-cycle power unit with a design capacity of 110 MW, the operation of absorption refrigerating systems as part of a combined-cycle unit demonstrated an increase in power of up to 9.5 MW at an ambient temperature of 30°C. A decrease in the dependence of the gas turbine power on the ambient temperature was revealed to have a positive effect on the manoeuvring characteristics in the range from 40 to 100% of its rated load. Absorption refrigerating systems introduced into the combined cycle can be used to minimise the effect of summer power limitations both on the combined-cycle power unit and on the power system as a whole. The installation of absorption refrigerating systems is possible without significant changes in the design of the main and auxiliary equipment. In future, it will be possible to apply the air-cooling circuit of the proposed absorption refrigerating systems as a circuit for the anti-icing system of a gas-turbine plant.

combined cycle plant, gas turbine unit, equipment operating modes, absorption-refrigerating machine, energy efficiency, operating conditions, maneuverability