Vol 8, No 1 (2009)

The paper analyses cross separation flow about an impulsively started circular cylinder in a non-viscous non-compressible medium by the vortex method. The impact of viscosity on resistance is expressed through the circulation of vortices formed behind the cylinder. By analogy the computation of plane flow is reduced to the computation of transverse force when a body of revolution moves at an angle of attack.

The paper deals with the tasks of forming command control of hypersonic aircraft: the main aircraft and the accelerator aircraft during acceleration and climb. The motion is analysed in conditions of atmospheric density perturbations and deviations of aircraft aerodynamic characteristics. An algorithm of single-channel (by the angle of attack) direction is proposed and its ability to compensate the impact of perturbations on satisfying the final conditions of motion is investigated.

Two actual launch paths are chosen as an example to consider the main regimes of flow around rocket boosters with oversized head caps, special attention being paid to regimes of high-altitude flying. Reynolds and Mach numbers varying with altitude are calculated on the basis of parameters of these paths (time, velocity and altitude). Then, taking into account the Tsyan diagram showing the separation into the principal flow areas, flow regimes of carrier rockets are determined, in particular, the transition from the standard gas dynamics area to the slip flow area.

The paper outlines the results of approbation of the numerical model developed in [1] of the account of viscosity impact on the flow in low-thrust rocket engine nozzles in the approximation of a laminar boundary layer with sliding by comparing the results of calculations according to the model both with the experimental results and with the results of calculations using a model of a higher level (shortened Navier-Stokes equations in the approximation of a narrow channel).

The paper outlines the procedure of experimental analysis of flow separation in low-thrust rocket engine (LTRE) nozzles with a profiled supersonic part. The procedure was developed under the author’s supervision at the research centre of space power engineering of SSAU. The results obtained on the basis of the procedure are presented, which show significant peculiarities of separation parameters in LTRE nozzles. These are connected, mostly, with the change in the nature of the flow in the boundary layer from laminar to turbulent due to the shock wave that causes flow separation. Limitations of the existing design procedures for flow separation in rocket engine nozzles as applied to LTRE are revealed. It is shown experimentally that the nature of the flow in the boundary layer of the supersonic part of the nozzle of a standard 400 H thrust liquid-propellant rocket engine is laminar.

The paper presents a brief survey of diagnosis methods and means for the control of working condition of turbomachine blades. Information criteria of detecting the faulty state of turbomachine blades, in case of using a peripheral sensor only, are defined and justified. The results of computer modeling are presented.

Additional stresses after making a semicircular cut are calculated for a smooth cylindrical part with a hole in it for the case of advance surface plastic strain. It is found that, residual stresses of a smooth part being the same, additional stresses in the least section are equal to those of a solid part whose cross-section is equal to the double wall thickness.
It is established that residual stresses in strengthened parts with concentrators can be determined by the residual stresses of control specimens processed simultaneously with the parts.

The paper deals with some peculiarities of applying hydromechanical correction in electrohydraulic servo hydrodrives. A classification of correction devices on the hydromechanical element basis is given, the influence of additional correction feedback on the performance of the hydraulic drive is shown. A variant of a mathematical model of a servo drive with a combined hydromechanical correction device is presented.

The paper presents an iterative algorithm of improving control for dynamic systems based on object approximation on average at each iteration in the vicinity of the path being improved by linear-quadratic structures. The algorithm can be applied directly to simulation models of dynamic systems that have no complete analytical description, and it form a part of the method of optimizing control using such models. The efficiency of the method is illustrated by the example of helicopter emergency landing.