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The present paper provides a brief overview of the existing methods for energy separation and an analysis of the possibility of the practical application of the Hartmann–Sprenger effect to provide quasi-isothermal pressure reduction of natural gas at the facilities within a gas transmission system. The recommendations of external authors are analyzed. A variant of a quasi-isothermal pressure regulator is proposed, which assumes the mixing of flows after energy separation. Using a numerical simulation of gas dynamics, it is demonstrated that the position of the resonators can be determined on the basis of calculations of the structure of the underexpanded jet without taking into account the resonator and, accordingly, without the need for time-consuming calculations of the dynamics of the processes. Based on the results of simulating the gas dynamics of two nozzle–resonator pairs installed in a single flow housing, it is shown that, in order to optimize the regulator length, the width of the passage between the two nearest resonators should be greater than or equal to the sum of diameters of the critical sections of the nozzles. Numerical vibroacoustic analysis demonstrated that the most dangerous part of the resonator is the frequency of its natural oscillations.

Recently, energy analysis has been added to Russian gas companies’ annual reporting system. This new practice indicates that corporate reports are improving their analyses by addressing energy issue and the financial efficiency of energy production. However, the use of summary energy indicators is limited in these annual reports. In this paper we review the history of energy analysis in Russia from the early USSR period to today. Under the guidance of energy return on investment (EROI), we compare energy efficiency indicators with financial efficiency coefficients. The results show that the value of the return on cost of sales (ROCS) is negative in certain instances, while the value of the energy return on cost of sales (EROCS) is extremely high under the example of the Russian energy company JSC “YATEC.” Money-based indicator values (ROCS and return on fix assets (ROFA)) fluctuate with internal company financial management goals, and from the outside depending on market prices. Meanwhile energy-based values (EROCS) remain stable. Added financial analysis and energy analysis in companies’ annual statements will supplement each other in practice and will present the full picture for company efficiency analysis.