Investigation of operating modes of circuits with expander-generator units in cogeneration boilers with gas-piston internal combustion engines

In this mode, due to a decrease in the pressure drop used in the expander, useful effect has been shown to decrease. The paper considers the operating modes of various schemes for the use of expander-generator units in cogeneration boilers with gas-piston internal combustion engines. In the scheme with the absence of gas heating before the expander at low air temperatures, crystallohydrates may fall out after the expander. In order to prevent this phenomenon, a mode with gas throttling after the expander is proposed. In this mode, due to a decrease in the pressure drop used in the expander, its useful effect will decrease. The study also shows that the scheme with gas heating in front of the expander enables the available pressure drop to be fully realised. At a certain outdoor air temperature in the summer, the use of gas heating may become unprofitable due to a decrease in the efficiency of internal combustion engines for a heated circuit. At higher outdoor temperatures, the study proposes a mode with gas heating turned off. Annual and average monthly fuel economy from the use of various schemes of expander-generator units for a cogeneration boiler house in comparison with the scheme with drosseling is calculated. It is shown that heating the gas before the expander to 100 °С allows annual fuel economy to be increased by about 1.4 times, when compared to a scheme using an expander without heating.