Vol 6, No 3 (2020)

This article deals with short description of cryogenic valves and calculation of specific load in sealing, results of experimental researches of separate dimensions of multi-layer bellows and results of comparative tests of valve sealing. Plant of valve testing in liquid hydrogen is also described.

This paper presents the results of a numerical study of synchronization of pendulums, chronometers, and mechanical clocks suspended from a common movable beam. An auxiliary problem is considered about the oscillations of a pendulum with a swinging weight, then the mutual synchronization of free vibrations of two and four pendulums (and pendulums with the supply of a moment pulse-clock) on a common movable spring-loaded beam. It is shown that in the considered simplest configuration, mutual synchronization (equality of frequencies or oscillation periods) is performed with high efficiency. The frequency of synchronized oscillations of the pendulums is close to the frequency of vibrations of the platform in a wide range of changes in its rigidity. The degree of connectivity of pendulums and synchronization of their oscillations is determined by the Strouhal number. Synchronization of clocks does not guarantee the accuracy of their movement, which is achieved only when the Strouhal number is equal to one.

increasing the efficiency of the power plant. A method of controlling the supply of cryogenic fuel to a gas turbine engine is to pump its liquid phase, followed by its separation into two parts and controlling the flow rate of each part. Heated the first part of the cryogenic fuel to a gaseous state in the heat exchanger, mixing it with the second part and feeding the resulting mixture of cryogenic fuel into the combustion chamber. The first part of the cryogenic fuel flow rate is passed through the heat exchanger Gta = Gsm · [Ср_sm · (Тfp + ΔT) – il] / [ig – il], where Gsm is the consumption of cryogenic fuel at the outlet of the mixer, Ср_sm is the isobaric heat capacity of cryogenic fuel at the outlet from the mixer, Тfp is the temperature of the phase transition of cryogenic fuel from liquid to gas at a pressure in the mixer, ΔT is the temperature of the gas mixture of cryogenic fuel at the outlet of the mixer above the temperature of the phase transition, il is the enthalpy of the first part of the liquid phase of cryogenic fuel at the input ode to the heat exchanger and the second part of the liquid phase of the cryogenic fuel, which is fed to the second entrance to the mixer, ig is the enthalpy of the gaseous phase of the cryogenic fuel at the outlet of the heat exchanger, at which it is fed to the first entrance to the mixer. Moreover, ig > Ср_sm · (Тfp + ΔT) > il and Gsm = Gta + Gl, where Gl is the flow rate of the second part of the liquid phase of the cryogenic fuel, which is fed to the second input to the mixer. When the pressure of the cryogenic fuel in the mixer is below the critical value Pkr, the temperature Тfp of the phase transition from liquid to gas of the cryogenic fuel is taken equal to the temperature Тnas on the saturation line of the cryogenic fuel at the corresponding pressure in the mixer. The excess of the temperature of the cryogenic fuel mixture over the phase transition temperature after mixing the gas and liquid phases at the mixer outlet sets ΔT = 60 ° ... 170 ° for cryogenic methane and ΔT = 150 ° ... 260 ° for cryogenic hydrogen. Due to the gasification of a part of the cryogenic fuel consumption in the heat exchanger and subsequent mixing of this part with the second liquid part of the cryogenic fuel in the mixer, the freezing of the outer surface of the heat exchanger in all operating modes of the power plant is reduced. Due to the reduction of external freezing of the channels of the heat exchanger, the heat transfer efficiency is increased in it. By reducing the dimensions of the heat exchanger, the hydraulic losses in the gas-dynamic path of the power plant are reduced, which, in turn, increases its efficiency. By lowering the temperature of the gas phase of the cryogenic fuel at the inlet to the combustion chamber, the temperature of the exhaust gases at its outlet is reduced, which, in turn, increased the reliability of the gas turbine of the power plant. The method of operation of the cryogenic fuel supply system is intended for ground-based power plants and vehicles. The work is intended for scientists and designers in the field of cryogenic fuels for internal combustion engines.