Use of high pressures for solving problems of hypersonic aerodynamics

Abstract

On the occasion of the 100th anniversary of M. A. Lavrent'ev, it seems pertinent to summarize the longterm work on the physical foundations, design, and manufacturing of sources of high-pressure gases for hypersonic wind tunnels in the pages of a journal founded with the immediate participation from M. A. Lavrent'ev. This direction of experimental aerodynamics received invaluable support of M. A. Lavrent'ev in early 1970s, without which the scientific ideas would not, probably, be put into practice.The idea of using high (up to 20,000 atm) pressures of a gas in the plenum chamber in an aerodynamic experiment was first put forward in the late 1960s by M. A. Plotnikov [1] who worked at that time in Research Institute-1 in the group of Prof. E. I. Shchetinkov, one of the founders and proponents for using supersonic combustion in air-breathing engines of hypersonic flying vehicles (HFV) for Mach numbers from 8 to 20 [2]. At the same time, the papers of Soviet and American scientists posed the question of the necessity of developing of a reentry HFV with an aircraft-type take-off and landing, capable of taking payloads to the orbit of an Earth's satellite and back. It is expected that, with the use of these vehicles, the cost of putting payloads to orbit, which is the key economic factor of using spacecraft systems in practical activity outside of the military field, will decrease by 5 to 8 times. One of the main obstacles for the use of such systems is the absence of knowledge on the complex of fundamental phenomena that accompany and ensure the HFV flight. The existing hypersonic aerodynamic facilities do not allow one to create conditions necessary for testing the corresponding HFV models [4]. This is especially true for reproduction of Reynolds numbers and ensuring test-gas purity and run time.At the end of the 1960s, M. A. Plotnikov and his colleagues developed tables of thermodynamic functions of nitrogen [1] from which it followed that the transition to the pressure region up to 10,000-20,000 atm leads to an additional contribution to the gas enthalpy equivalent to a temperature increase by approximately 1000 K per each 10,000 atm. On the one hand, this offered a possibility of increasing the Lavrent'ev Institute

Heat-engineering units for the generation of dense high-temperature gas

“…The operating principle of the compensator is based on the similarity of motion of two pistons under the effect of the same pressures acting on similar surfaces, provided that the mass ratio of the pistons is inversely proportional to the lengths of barrels. With the mass ratio of the pistons of 1:10, the additional energy of the receiver spent for the compensator work does not exceed 10% of useful work [12]. An exact fitting of the piston mass during the experiments performed in this stand made it possible to reduce the shift of the center of gravity of facility stage to 0.25 mm, which is one-fourth of its longitudinal elastic deformation under the effect of working pressures [12].…”

“…In one line of research, investigations were developing of devices which required record pressures (up to 20 000 atm) [12] and relatively low temperatures (up to 2000 K). Special attention was given to increasing the impulse duration and ensuring the validity of preassigned law of variation of flow parameters in the working mode; later on, this made possible the use of such facilities in experimental aerodynamics.…”

“…The transfer of this reaction force to the foundation would cause strong vibrations and destruction of the building. The almost complete suppression of the impulse developed by the reaction force was attained in [12] using a special compensator. This compensator is a continuation of the barrel in the tail part of the compression stage, which is of the same cross section but shorter.…”

“…An example of realization of the former approach is the A-1 facility [12]. The low compressibility of gas at pressures above 2000 atm made it possible to divide the process between two stages, of which one is a system of adiabatic compression with a free "heavy" piston [89], and the other one is a pressure booster capable of approximately twofold after-compression of gas with its subsequent displacement from the stilling chamber [12].…”

“…The low compressibility of gas at pressures above 2000 atm made it possible to divide the process between two stages, of which one is a system of adiabatic compression with a free "heavy" piston [89], and the other one is a pressure booster capable of approximately twofold after-compression of gas with its subsequent displacement from the stilling chamber [12]. The realization of pressures of 10 000 atm in the acting facility, in spite of its small size (the stilling chamber volume of 40 cm 3 ), made this facility record-breaking as regards the density of hypersonic flow and the reproducible values of the Reynolds number [12]. The presence of displacing booster at different pressures in the stilling chamber and different cross-sectional diameters makes possible the duration of the operating mode of the facility of 20 to 250 ms [14].…”