Vol 17, No 4 (2018)

The principle of automated construction of a fan blade model according to the profile measurements performed in a CAD-system is presented. Automatic construction of the model is based on the results of measurements obtained in the course of the control measurement procedure. The process of the blade airfoil control with the use of a portal-type Coord3 Hera NT coordinate-measuring machine and a measuring head with a Renishaw PH10T probe is described. The main points of the check method and instrumentation measures are presented. For example, the principle of the fan blade fixing is considered, the process of measuring the position of the base surfaces and points is presented, the process of measuring the profile points’ coordinates is described, the geometric parameters obtained in the course of calculation of profile deviations are presented. A measured 3D model of the fan blade is created according to the data of the control measurement procedure, taking into account complementary construction tools. The order of work for the automation of constructing a three-dimensional blade model is described. The direction of further work is specified, related to carrying out strength calculations to create a “hot” model of the measured blade, and subsequent aerodynamic calculations of the resulting blade to determine the most efficient set of geometric parameters for robust optimization.

A truss-core sandwich panel is a promising load-bearing element of lightweight high-stiffness structures. The use of this element in load-bearing structures makes it necessary to know its mechanical and strength characteristics depending on the structure and properties of a typical core cell. Currently, the available results are not sufficient to assess the strength due to the complexity of taking into account all the features of the loading of the core structure in the form of repeated pyramidal and tetrahedral unit cells most common in the production of lightweight truss cores. In the research of the strength properties of a unit cell, it is assumed that the destruction of the truss structure may occur when the yield stress in the material of the core is exceeded or if buckling takes place. The scheme of destruction of the truss structure in the cell will depend on the combination of unit cell equivalent stress values. The critical core buckling stress is usually less than the yield stress. Therefore, when co block diagrams of equivalent stress constraints are constructed, one can observe a rather complex picture of the change in the limit values depending on the azimuthal angle in the plane of the cell base. To analyze limitation diagrams, the easiest way is to introduce a parameter determined by the ratio of the critical buckling stress to the magnitude of the yield stress of the core material. In this case the limitation diagrams will not depend on the specific critical absolute values of stresses, but on their relationship; the nature of the diagrams will not depend on the density of the core. The design parameters of the core are determined on the basis of the construction of other diagrams for the given (required) values of generalized compressive stiffness, transverse shear, generalized critical compressive stresses and transverse shear of a unit cell of the sandwich structure which depend on the relative density of the truss core. The combination of these two constraint diagrams gives a more complete picture of the degree of optimality of the truss core design parameters.

The task of optimizing control methods in order to maintain key performance parameters of a gas turbine engine throughout the engine service life is considered. Variations in the performance characteristics of engine components in the process of operation are analyzed. To study the effect of deterioration on the engine parameters, a mathematical model of a turbofan engine was modified. The influence of degradation of the gas turbine engine components on its key performance parameters with traditional control methods is assessed. An engine control method using the value of thrust calculated in the on-board engine mathematical model is proposed. This method makes it possible to compensate for the negative effect of the components’ performance degradation due to their wear. The results of mathematical modeling of the operation of a turbofan engine in steady-state and transient modes are given. The results confirm the effectiveness of the proposed control method: despite the engine deterioration the original thrust value is maintained due to the available gas temperature margin in the combustion chamber

We study the problem of determining time-optimal control of in-plane rendezvous transfer of spacecraft with low transversal thrust. We use the Pontryagin maximum principle to determine the optimal control program. Motion is considered in the vehicle centric system with linearized equations. We recognize secular and periodic components of relative motion. Motion control is accomplished by the reversal of the thrust acceleration component. We study the general problem – controlling the periodic and secular components at the same time (joint optimal control program). Also we study partial problems – determining separate control programs for secular and periodic components of planar motion. Solving partial problems made it possible to determine the structure of the joint optimal control program. We found that the adjustment of secular motion components contains no more than two phases of constant acceleration. The adjustment of periodic motion components consists of a sequence of boost and deceleration phases, the number of which in a single pass does not exceed three.

The use of 3-D simulation programs and in particular NX and ANSYS simulators brought the design and fine tuning of gas turbine engine combustion chambers to the next level, as it allows improving the performance (increased combustion efficiency, reduced radial and circumferential non-uniformity of the total gas temperature), as well as determining the weak points of the structure. The article analyzes the flow of fuel jets from the finger sprayers of the afterburner of the combustion chamber of a gas turbine engine. The problem of optimizing the distribution of fuel is formulated: the fuel at the exit of the flame tube is to be evenly distributed by varying the diameters of the holes in the fuel manifolds. Restrictions are imposed on the optimization problem – the supply of fuel to the peripheral zone at the outlet of the afterburner is reduced by a factor of five. The optimization effect is verified by comparing the fuel combustion efficiency in the case of standard fuel distribution with the optimized distribution option using the NX and ANSYS 3-D simulations. As a result, we observe an increase in combustion efficiency in all afterburner modes of engine operation.

The article presents an analysis of the possibility of using propulsion systems and rocket thrusters based on various physical principles and used as part of small and very small spacecraft. The parameters of efficient propulsion systems and low-thrust rocket engines are examined from the standpoint of being used as  components of spacecraft fueled by various kinds of propellant: gaseous fuel, mono-fuel, including advanced compositions based on hydroxyl-ammonium nitrate, bipropellant fuel; xenon electric rocket systems, as well as special propulsion systems and low-thrust rocket engines operating on nitrous oxide, ammonia, gaseous hydrogen and oxygen; electric-powered systems based on pulsed plasma thrusters, ion and steady-state plasma engines. Taking into account the data analyzed, an attempt was made to categorize the propulsion systems and low-thrust rocket engines. Their use in small spacecraft, spacecraft of the “Mini”, “Micro”, “Nano” classes in various propulsion systems and low-thrust rocket engines was found to be preferable.

The paper describes a procedure of numerical simulation of operating fluid (water) discharge into the air environment through the hydraulic paths of a mixer composed of two low-flow coaxial swirl injectors. The method is based on a two-velocity model of a two-phase liquid flow and determining the interface interaction resistance coefficient versus the Reynolds number in the course of solution. The Reynolds number is calculated from the relative velocity of the liquid components forming the two-phase flow. The paper investigates variations in the mixer spray pattern versus two characteristic dimensions reckoned among the key parameters to calculate the coefficient of interface interaction resistance. Algorithms of calculating the coefficient of interface interaction resistance are proposed. The results of modeling liquid mixing and film flow breakdown within and beyond the mixer hydraulic paths for different values of the characteristic dimensions are presented. It is shown that we can achieve the conformity of the calculation results obtained by using the proposed method with the cold flow data by selecting the values of characteristic dimensions with reference to which interface interaction resistance coefficients are determined. Further works are projected.

A new method is proposed for coating the inner surface of pipes in a confined space in which a sloping position of the pipe is expected during the process. Mathematical modeling of non-pressure fluid flow in an inclined pipe was carried out. The method implies controlled outflow of the material being applied and simultaneous rotation of the pipe being worked. The thickness of the coating depends on the velocity of the material flow along the inner surface of the pipe. The dependence of the fluid velocity on the radius of the pipe being worked and the level height in the filling column is calculated. The results of calculating the analytical dependence in the Mathcad application are presented. Dependence diagrams of material flow are presented for various design parameters that make it possible to determine the operating practices in the process of applying the coating. Uniform coating is obtained due to constant velocity of the material flow along the full length of the pipe. The obtained graphs were analyzed and the direction of further research connected with the influence of rotational velocity and fluid viscosity was determined. The use of the proposed method makes it possible to increase labor productivity and improve the quality of protective coating.