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Thermodynamic Rationale for Using Expander-Compressor Gas Turbine Power Unit

Authors: Strebkov A.S., Osipov A.V., Zhavrotskiy S.V. Published: 28.03.2021
Published in issue: #1(136)/2021  

DOI: 10.18698/0236-3941-2021-1-166-184

 
Category: Power, Metallurgic and Chemical Engineering | Chapter: Heat Engines  
Keywords: тurbo-expander, gas turbine unit, thermodynamic cycle, the degree of pressure increase, specific fuel consumption, absolute thermal efficiency

Natural gas is transported through a network of main gas pipelines under high pressure, and the process of its consumption requires a decrease in pressure of gas laid mainly in throttling devices. It is beneficial to use part of the available energy potential of natural gas for electricity production by means of expander-generator technologies. However, the task of finding ways to increase the capacity and efficiency of gas turbine power units using the energy of excess pressure of natural gas does not lose its relevance. The study poses and solves the problem of developing a new thermal cycle diagram of a combined power unit to substitute throttling pressure regulators at gas distribution stations with an expander-compressor gas turbine unit. A distinctive feature of the unit is the replacement of the gas turbine drive of the air compressor with its drive from the turbo-expander by using the energy of excess pressure of natural gas. This results in significant increase in the absolute thermal efficiency and decrease in the specific fuel and energy costs. We developed analytical dependencies relating the operating parameters of the expander-compressor gas turbine unit and its output characteristics. Thus, it was possible to find an approach to calculating the unit, the approach being based on proven methods for thermal cycle calculation. The results of the performed calculations show that, in comparison with gas turbine units, the expander-compressor gas turbine unit has a significantly lower specific consumption of equivalent fuel and a lower negative impact on the environment

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