An integrated system of operation mode synchronization for the helicopter powerplant engines

We consider the problem of synthesizing the control system of the helicopter power plant that consists of two turboshaft engines with free turbines, which through an overall mechanical transmission rotate the helicopter uniaxial rotors. We discuss the problem of coordinating the dynamic characteristics of the individual control loops, when the modes of operation are changed with the aim of balancing the load of each of the two engines.     

On the Non-coplanar Transfer of Type II between Two Circular Orbits

The paper regards two-impulse transfer from a low parking orbit into a circular orbit with the altitude less than 36 000 km, while the inclination correction is carried out with each maneuver. An approximate formula is proposed capable of evaluating analytically the optimal value of the first correction of inclination; the corresponding accuracy data are given. Examples are provided to show the operational efficiency of an optimal non-coplanar transfer of the type II with injections of satellites into various target orbits from Russian launch sites with due account of the available launch azimuths.     

Collapse of a spheroidal cavitation bubble near a solid wall

Dynamics of a gas bubble in a liquid near a solid wall is studied. The influence of the initial spheroidal disturbances of the bubble shape and the distance to the wall on the dynamics of the bubble–liquid system is analyzed. The pressure in the bubble is initially greater than that of the surrounding liquid. An algorithm based on the Euler scheme and the boundary element method is applied in the calculations.     

Influence of an oil supply process on the characteristics of plain journal bearings

In this paper, we present some experimental data on characteristics of plain journal bearings at different variants of oil supply inlet pipe arrangement and relative values of the shaft rotation speed and inlet pipe pressure. Also established is the significant growth of oil consumption when the inclination angle of the inlet throttling element axis is increased.     

Problems in formation and control of a required microacceleration level at spacecraft design,tests, and operation

In this paper, we consider the main aspects of a problem in formation and control of a required microacceleration level as the most important characteristic of the space laboratory intended for realizing the gravitational and sensitive technological processes. The estimation model and methodology to control and estimate the microaccelerations are presented that are necessary for the well-founded choice of the spacecraft parameters and carrying out their flight and space tests, when the new special-purpose space laboratories are designed and constructed.     

Experimental Study of Corner Stall in a Linear Compressor Cascade

In order to gain a better knowledge of the mechanisms and to calibrate computational fluid dynamics (CFD) tools including both Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES),a detailed and accurate experimental study of corner stall in a linear compressor cascade has been carried out.Data are taken at a Reynolds number of 382 000 based on blade chord and inlet velocity.At first,inlet flow boundary layer is surveyed using hot-wire anemometry.Then in order to investigate the effects of incidence,measurements are acquired at five incidences,including static pressures on both blade and endwall surfaces measured by pressure taps and the total pressure losses of outlet flow measured by a five-hole pressure probe.The maximum losses as well as the extent of losses of the corner stall are presented as a function of the investigated incidences.     

Influence of the gas-distributing grid structural features on the flow parameters in the liquid-propellent rocket engine with producer gas afterburning

The analysis of structural features of the gas-distributing grid was carried out by modern facilities of computational gas dynamics to equalize flow parameters upstream of a mixing head in LPRE with producer gas afterburning. For the given simulation conditions we defined the optimal geometrical dimensions of the facets on the gas-distributing grid openings, providing the maximal discharge coefficient and the minimal pressure differential. We also examined the grid design variants with the various distribution of facets of different geometry, which allows the outflow parameters to be varied according to the grid area. It is obtained, that a flat grid with various openings geometry in the sectors makes it possible to provide the best equalization of the pressure and velocity fields upstream of the mixing head and the minimal pressure losses.     

Nonlinear dynamics of antennas in space communication facilities

A mathematical model of complex vibrations for the cantilever Bernoulli-Euler beam in the XOZ plane constructed by the finite difference and finite element methods and the fourth-order Runge-Kutta method is presented. We determined the critical value of the damping coefficient ɛ = 0.28, at which the system changes from the dissipative state to conservative one, using the Morlet wavelet. The results of analyzing the frequency characteristics of the system are presented.     

Simulation of a flexible spacecraft motion to evaluate microaccelerations

A method for simulating a flexible spacecraft motion using Lagrange’s quasivelocity formulation is considered. An algorithm of quasivelocity formation by Walsh’s means is proposed. This method can be used to evaluate a quasistatic microacceleration field component in the spacecraft internal environment.