Improvement of conventional combustion chamber structure in order to enhance GTE ecological indicators

The test results of a conventional combustion chamber with the improved structure are presented. The concentration of toxic substance emissions is reduced as compared with combustion chambers of the similar type.     

Analysis of static loading of a helicopter tubular skid landing gear

A three-dimensional design model of a helicopter tubular skid landing gear based on the application of the large beam displacement theory is presented. The design model takes into account special features of constructive, physical and geometrical deformation nonlinearity. The analysis of a real helicopter structure is given that confirms sufficient validity of calculation results obtained using the model developed by comparing with the results of the finite element analysis.     

Numerical modeling of large elastoplastic strains in terms of principal stretches. II. Physical relations,calculation algorithm

The constitutive relations and plastic flow rule are derived from the thermodynamics equations. The known procedures of determining the plastic strain rate value are described. A calculation algorithm is presented that is based on the incremental loading, linearization of the virtual power equation and the projection method. A numerical example is presented.     

Thermodynamic properties of mixed fuel combustion products

In this paper, the results of calculating the processes of two fuel mixture combustion in different proportions are presented. The values of temperature, thermal capacity, specific gas constant and isentropic expansion ratio of combustion products are given. Also shown is the distinction of thermodynamic properties from the additivity law.     

Simulation of helicopter motion in unsteady conditions

To calculate the unsteady helicopter motion, we propose a simplifying approach consisting in the fact that the numerical solution of equations of nonlinear nonstationary aerodynamics and flight dynamics are made successively in time intervals. As an example, the results of calculating the helicopter motion in descent are presented. The mathematical model and algorithm can be used for calculating the unsteady motion of different helicopters.     

Investigation of gas dynamics numerical schemes based on the solution of one-dimensional test problems

The application of the optimized dispersion relation preserving scheme (DRP-scheme) in combination with the explicit optimized two-layer Runge-Kutta scheme is presented to solve a system of one-dimensional and quasi-one-dimensional Euler equations using as an example the solution of four test problems, namely, discontinuity disintegration in a tube (Sod’s problem); transfer of the lowamplitude Gaussian pulse; acoustic wave propagation through the transonic nozzle; acoustic wave-shock interaction. Also given are the comparison of the calculation results using different schemes: DRP, CABARET, CE-SE and the standard Lax-Wendroff schemes as well as the solutions obtained with the use of software packages.     

Modes of Sliding,switching and linear vector control with a given quality of transient processes under uncertainty

The results obtained for the systems with a linear stationary object and scalar control of sliding and switching modes [1] are further developed. The methods of forming five modes of system operation with discontinuous and linear vector control at nominal and uncertain limited disturbances are suggested. The necessary quality of transient processes with regard to the speed of response and zero stationary error at all five modes and also controlled oscillation frequency and amplitude of control signals at the sliding modes are provided. The effective sequence of switching the modes mentioned during the finite and unlimited time intervals is proposed. The results are useful for qualitative tracking of programmed motion for flight vehicles, robot manipulators, and other technical and production systems.     

The Magnetic Field of Mercury

The magnetic field strength of Mercury at the planet’s surface is approximately 1% that of Earth’s surface field. This comparatively low field strength presents a number of challenges, both theoretically to understand how it is generated and observationally to distinguish the internal field from that due to the solar wind interaction. Conversely, the small field also means that Mercury offers an important opportunity to advance our understanding both of planetary magnetic field generation and magnetosphere-solar wind interactions. The observations from the Mariner 10 magnetometer in 1974 and 1975, and the MESSENGER Magnetometer and plasma instruments during the probe’s first two flybys of Mercury on 14 January and 6 October 2008, provide the basis for our current knowledge of the internal field. The external field arising from the interaction of the magnetosphere with the solar wind is more prominent near Mercury than for any other magnetized planet in the Solar System, and particular attention is therefore paid to indications in the observations of deficiencies in our understanding of the external field. The second MESSENGER flyby occurred over the opposite hemisphere from the other flybys, and these newest data constrain the tilt of the planetary moment from the planet’s spin axis to be less than 5°. Considered as a dipole field, the moment is in the range 240 to 270 nT-R _M ³ , where R _M is Mercury’s radius. Multipole solutions for the planetary field yield a smaller dipole term, 180 to 220 nT-R _M ³ , and higher-order terms that together yield an equatorial surface field from 250 to 290 nT. From the spatial distribution of the fit residuals, the equatorial data are seen to reflect a weaker northward field and a strongly radial field, neither of which can be explained by a centered-dipole matched to the field measured near the pole by Mariner 10. This disparity is a major factor controlling the higher-order terms in the multipole solutions. The residuals are not largest close to the planet, and when considered in magnetospheric coordinates the residuals indicate the presence of a cross-tail current extending to within 0.5R _M altitude on the nightside. A near-tail current with a density of 0.1 μA/m² could account for the low field intensities recorded near the equator. In addition, the MESSENGER flybys include the first plasma observations from Mercury and demonstrate that solar wind plasma is present at low altitudes, below 500 km. Although we can be confident in the dipole-only moment estimates, the data in hand remain subject to ambiguities for distinguishing internal from external contributions. The anticipated observations from orbit at Mercury, first from MESSENGER beginning in March 2011 and later from the dual-spacecraft BepiColombo mission, will be essential to elucidate the higher-order structure in the magnetic field of Mercury that will reveal the telltale signatures of the physics responsible for its generation.     

The Solar Dynamo

Observations relevant to current models of the solar dynamo are presented, with emphasis on the history of solar magnetic activity and on the location and nature of the solar tachocline. The problems encountered when direct numerical simulation is used to analyse the solar cycle are discussed, and recent progress is reviewed. Mean field dynamo theory is still the basis of most theories of the solar dynamo, so a discussion of its fundamental principles and its underlying assumptions is given. The role of magnetic helicity is discussed. Some of the most popular models based on mean field theory are reviewed briefly. Dynamo models based on severe truncations of the full MHD equations are discussed.     

Geomagnetic Observations for Main Field Studies: From Ground to Space

Direct measurements of the geomagnetic field have been made for more than 400 years, beginning with individual determinations of the angle between geographic and magnetic North. This was followed by the start of continuous time series of full vector measurements at geomagnetic observatories and the beginning of geomagnetic repeat stations surveys in the 19th century. In the second half of the 20th century, true global coverage with geomagnetic field measurements was accomplished by magnetometer payloads on low-Earth-orbiting satellites. This article describes the procedures and instruments for magnetic field measurements on ground and in space and covers geomagnetic observatories, repeat stations, automatic observatories, satellites and historic observations. Special emphasis is laid on the global network of geomagnetic observatories.