Volume 25, Nº 3 (2024)

The paper presents the developed methodology and designed a device for determining the Mach number during supersonic gas outflow. An analysis of various methods for determining the Mach number was carried out, including measuring the pressure at the flow boundary, the use of shock waves, and the use of optical methods. A comparison was made of the accuracy of the readings when using the considered methods. Based on the results obtained, a technique for high-precision determination of the Mach number has been developed, including a combination of several independent measurement methods. A device has been designed that implements this measurement technique, and the results of experimental tests in a wind tunnel have been reviewed, including instrument readings, graphs and tables confirming the accuracy and reliability of the data obtained. Their accuracy and reliability are analyzed. Using the analysis, it is possible to ensure the selection of the most rational method for determining the Mach number at the initial stage of designing aircraft, such as airplanes, missiles, fighters, and UAVs. Accurate knowledge of the Mach number allows engineers to optimize the aerodynamic characteristics of the aircraft, ensure flight safety, improve engine efficiency and overall air transport performance. In addition, the Mach number is the most important criterion of similarity when modeling in aerodynamic research, which makes the developed methodology and device relevant not only for the design of aircraft, but also for a wide range of scientific and engineering research in the field of aeronautical technology. It is emphasized that the presence of a reliable method for determining the Mach number can significantly reduce the time and resources spent on testing and improving aircraft, and also contributes to the development of innovative technologies in the field of aviation and astronautics.

The creation of spacecraft propulsion systems with high energy efficiency and minimal weight and size parameters is an urgent scientific and technical task of the domestic rocket engine industry. At the same time, requirements are put forward to optimize the cost and time of design, development and manufacturing of engines, as well as environmental safety at all stages of the product life cycle. In this regard, it is proposed to use advanced laser 3D printing technologies (additive technologies) from metal powder using CAD models of engine parts in the production of space low thrust rocket engines (LTRE).

 Laser melting technology on modern 3D printers makes it possible to produce complex monolithic engine structures without the use of labor-intensive and resource-intensive operations of machining, welding, and soldering, as well as a significant reduction in the volume of plumbing, assembly, control and measuring work, and a decrease in the influence of some non-production factors.

The article discusses issues of practical application of promising technologies in the creation of LTRE. The results of fire tests are presented, which will be used to refine the previously developed calculation models of oxygen-hydrogen LTRE when creating advanced rocket engines for spacecraft.

The object of the study was an experimental sample of LTRE with a nominal thrust of 150 N using gaseous fuel components oxygen and hydrogen, developed and manufactured using additive technology. The experimental LTRE is considered as a prototype of the engine for orientation, stabilization and launching of the oxygen-hydrogen upper stage. The purpose of the work is to study the effectiveness of previously unexplored design solutions for organizing mixture formation and cooling of an oxygen-hydrogen LTRE, to determine their influence on the perfection of the working process and the thermal state of the engine chamber. Fire tests were carried out in single switching mode with a duration sufficient for the LTRE chamber to reach a stationary thermal regime, with the determination of the energy characteristics and thermal state of the structure.

The subject of this study is the trajectory characteristics of the long-range test ballistic missile (TBM).

The purpose of the study is to increase the capabilities of TBM in separating test object (TO). At the same time, as a generalized quantitative measure of this increasing the post-boost vehicle (PBV) fuel reserve consumed for separation of TO is taken.

The design-ballistic task of rationalizing the distribution of the available fuel of the TBM DS between the following main characteristic section of its flight has been set and numerically and analytically solved: final sustainer stage underperformance compensation; turns with subsequent angular stabilization, retreats and lead away; TO disconnection (separation section).

As a result, it is shown that without reducing the quality of TBM launch tasks, it is permissible to redistribute the consumed fuel of the PBV between these section relative to the distribution for a standard ballistic missile (SBM), leading to a significant increase in its reserve consumed in the section of disconnection of the TO (when flying along the ballistic vertical).

At the same time, the purpose of the study is achieved – the capabilities of the TBM in the separation of the TO are increased, which, while direct planning of launches is evaluating, can be expressed in an increase in the number and/or total mass of the TO and/or an increase in speed or time intervals in the order of sequential disconnections of the TO.

The given numerical examples (using a converted three-stage SBM as a TBM) also show a significant dependence of the amount of fuel increment of the PBV consumed at the TO disconnections of the trajectory conditions of test launches (the corresponding initial data (ID) for calculations are borrowed from the author’s previously published work): length of the route; kinematic parameters of launch at the moment of independent PBS flight beginning determined by the launch task.

During the study, methods of flight theory and design ballistics of LR missiles were used.

As a conclusion, it can be noted that the considered task and methods for its solution can be useful (of course, taking into account the necessary specialized improvements) in works of the executive ballistics level when planning and evaluating the result of TBM launches.

In this material development stages of the two-fuel combustion chamber for the HK-16-18CT engine are presented. Calculation of processes on the basis of the theory of turbulent burning is made.

One of competitive advantages of stationary gas-turbine installation is the possibility of work on two types of fuel: on diesel and on gaseous. Therefore creation of the two-fuel combustion chamber is relevant. The designing process of the two-fuel combustion chamber consists of several stages. At the first stage the nozzle is developed. It is equipped with two internal fuel channels. Then the front device is designed. in it nozzles are placed in two ranks. This device is equipped with two separate fuel collectors. It contains cavities for a fuel supply to two channels of nozzles. Such constructive decision allows to carry out switching of one type of fuel to another without stopping operation of the engine. As a prototype for distribution of air on length of a spherical pipe the combustion chamber of the NK-8-2U engine is taken.

Calculation of processes in the combustion chamber was carried out on the basis of the theory of turbulent burning. During calculation such parameters as the normal speed of burning, the pulsation speed, coefficient of turbulent exchange, scale of turbulence and intensity of turbulence are determined.

The equation of thermal balance for determination of temperature in the considered area at combustion of natural gas and diesel fuel is created. It is considered what in one case is spent warmly going for evaporation of liquid fuel, in other case it is not necessary.

For calculation of formation of nitrogen oxides Ya. B. Zeldovich's theory of thermal oxidation of nitrogen is used by oxygen. Emissions of carbon monoxide are determined by an empirical formula

From gasdynamic calculation of the HK-16-18CT engine parameters on an entrance to the combustion chamber on various operating modes at combustion of natural gas are known.

Calculation for definition of a necessary consumption of diesel fuel for power setting at preservation of temperature at the exit is executed from the combustion chamber.

 By results of calculation the schedule of emission of harmful substances from power setting on gas and diesel fuels is constructed. The comparative schedule of dependence of completeness of combustion of fuel on power setting is constructed.

Settlement emissions of harmful substances of the developed combustion chamber in the range of operation of the engine on power from 0,7Ne to 1 Ne for liquid fuel: NO_x15%O₂ does not exceed 250 mg/m³, СO15%О₂ does not exceed 300 mg/m³; for gaseous NO_x15%O₂ fuel does not exceed 120 mg/m³, СO15%О₂ does not exceed 150 mg/m³.

The paper examines issues related to the influence of laser texturing of the surface of a titanium alloy on the characteristics of the titanium-carbon fiber adhesive joint. Using an ytterbium pulsed fiber laser, textures with a linear structure (0°–0° and 90°–90°) and a mesh structure (0°–90°, ±30°, ±45°, ±60°) were created on the surface of a titanium alloy. The surface roughness values in two perpendicular directions were determined, and microsections were made, which can be used to characterize the surface morphology of the titanium alloy. To determine the adhesive strength of the joint, samples with the same surface texture were glued together. The samples were glued together according to OST 1-90281–86. Bonding was carried out within 24 hours after laser surface treatment. Before gluing, the treated surface was cleaned with isopropyl alcohol. Adhesive joint area S = 300 mm². Three-component adhesive VK-9 based on epoxy and polyamide resin was used as an adhesive. Laser surface treatment of titanium alloys increases the strength of the adhesive joint by more than 70 % relative to the untreated surface. This may indicate that the main mechanisms for increasing the strength of an adhesive joint are an increase in the contact area between the surface and the adhesive, and chemical modification that activates the surface. The processing texture has a lesser effect on the adhesive strength, provided that the specific surface energy of the laser processing is the same. When laser processing, you should pay great attention to the choice of surface texture, because certain textures can give an increase in strength by 20–30 %. If the type of load in the truss load elements is known, then it is better to use linear textures directed perpendicular to the direction of the load (for shear – texture 0°–0°; for torsion – texture 90°–90°). For mixed loads, it is better to use mesh structures ±30°, ±45°, ±60°, which resist loads in two directions.