A. I. Leont'ev

Gas-Dynamic Methods of Temperature Stratification (a Review)

The known methods of gas-dynamic temperature stratification are reviewed. Attention is concentrated on an analysis of the possibilities of the gas dynamic stratification method proposed by the author. The method is based on the difference between the equilibrium temperature of a thermally insulated wall in supersonic flow and the adiabatic stagnation temperature of the gas. Certain possible practical applications of the method to various types of energy-converting apparatus are considered. The basic trends of fundamental and applied research in the field of gas-dynamic temperature stratification are formulated.

Recovery factors for a permeable surface and a gas surface film in a supersonic turbulent boundary layer

The recovery factor on a permeable surface has been experimentally determined at various rates of injection of air into a supersonic turbulent boundary layer. On the basis of an analysis of the solutions of the integral momentum and energy equations for a turbulent boundary layer an expression is obtained for the recovery factor. The recovery factor in the region of a protective gas surface film in a supersonic external flow has been experimentally determined.

Law of friction in the region of a gas screen behind a permeable section

The results are given of measurements of friction behind a permeable section in a subsonic turbulent boundary layer at blowing intensity j = 0.003–0.04. Methods are proposed for calculating the local coefficients of friction in the region of a gas screen and the Reynolds number determined from the momentum loss thickness; these are in satisfactory agreement with experiment.

Gas Flow in a Supersonic Nozzle with a Coaxially Arranged, Partially Permeable Cylindrical Insert

An experimental study of gas dynamics was carried out in a supersonic nozzle with a tube coaxially arranged inside the nozzle over its entire length. The study (which is a continuation of (1)) was performed to investigate the flow pattern both inside the tube and in the gap between the tube and the nozzle walls. The experimental facility, described in detail in (1), is shown in Fig. 1. It consists of a supersonic nozzle and a partially permeable tube installed along the axis of symmetry of the nozzle. Air was delivered simulta- neously through the nozzle and the tube. The parameters of the facility are as follows: the total air flow rate G = 0.11 kg/s, the stagnation pressure in the stilling chamber P 00 = 3.86 〈 10 5 N/m 2 , and the stagnation temperature in the stilling chamber T 00 = 293 K. The Mach number on the tube axis and in the gap was calculated by the Rayleigh formula (2). The distri- bution of the Mach number is shown in Fig. 3. The Mach number in the tube is represented by solid points, and that in the gap by hollow points. In calculating the Mach number, the error was 1.76%. As is seen in Fig. 3, the flow is subsonic in the tube and in the gap up to x = 24 mm, and at x > 24 mm the flow is supersonic in the tube and in the gap. The Mach number in the gap is higher than that in the tube up to x = 42 mm, and at x > 42 mm the flow pattern is reversed. In the case when the permeable portion of the tube begins behind the nozzle throat (Fig. 3a), the flow in the impermeable portion of the tube turns from subsonic to supersonic at a distance x = 14 mm from its beginning; i.e., the supersonic flow arises almost in the middle of the impermeable portion of the tube. A possible cause of this phenomenon may be an intense suction of gas in the permeable section of the tube, which takes in a part of the gas from the boundary layer in the imperme- able portion of the tube. This may result in a reduction of the displacement thickness of the boundary layer in the tube and thereby promote the acceleration of gas to supersonic velocities. Results of calculations of the static pressure are given in Fig. 2, and those of the gas velocity in the tube and in the gap between the tube and the nozzle are given in Fig. 3; these results were obtained by numeri- cal solution of the equations of continuity and momen- tum for the flow in the initial section of the cylindrical tube and in the annular gap. The velocity at the inlet to the tube and to the annular gap was preassigned to be uniform over the entire cross section and equal to axial velocity W 1 for the tube and to the velocity W 2 in the middle of the annular gap. The values of the inlet veloc- ity for the tube W 1 and for the gap W 2 were found in the experiment. It was assumed that a turbulent boundary layer builds up from the front edge of the tube and the annular gap.

Law of heat transfer in the region of a gas curtain

The article gives the result of an experimental investigation of heat transfer in the region of a gas curtain behind the permeable part of the surface in a subsonic turbulent boundary layer in the range of blowing intensities j=0.001−0.04.

Turbulent boundary layer on a permeable surface with intensive blowing

Results of an experimental investigation of the structure and integrated characteristics of a turbulent boundary layer on a permeable plate in a broad range of blowing intensities ¯j=0.005−0.04 are presented.

Influence of a longitudinal pressure gradient on the effectiveness of a gas mist in a subsonic turbulent boundary layer

Investigations of effective methods of heat-shielding surfaces subjected to the effect of a high-temperature gas stream remain vital at the present time. One of the most prospective methods is that of injecting cooling gas through permeable section of a surface. In estimating the efficiency of such a method it is quite important to take account of the heat-shielding properties of the “cold” boundary layer downstream of the permeable section, i.e., in the gasmist domain. The question of the effect of a longitudinal pressure gradient on the efficiency of such a mist has not received a final solution.