Структура потока в межлопаточном канале соплового аппарата с поворотной диафрагмой

In the process of developing a numerical study method of a flat flow around a snap line with a rotary diaphragm, calculations were made at various degrees of opening the rotary diaphragm δ and pressure drops on the grille. As a result of calculations, for small degrees, the opening of the rotary diaphragm, complex patterns of the flow were obtained, in the inter-tube channel of the nozzle apparatus. The article presents some results of a numerical study of the supersonic flow in the channel of the nozzle apparatus with the degree of opening the rotary diaphragm δ = (0.15 ÷ 0.3). Modeling and calculating the flow of the working fluid is made using the Fluent software package. The construction of the calculated areas bounded by one inter-tube channel, for varying degrees of opening the diaphragm of the nozzle apparatus. Grids are built for calculated areas. Calculations were carried out for δ = (0.15 ÷ 0.3) and with different degrees of pressure drop on the grille. As a result of the calculations performed, the flow patterns in the inter-tube canal were obtained and behind it, and the distribution of the coefficients of the kinetic energy loss on the lattice front at various degrees of the discovery of the diaphragm at the inlet in the nozzle apparatus. According to the results of the work carried out, the following conclusions can be drawn: the structure of the stream in the inter-tube channel, the nozzle apparatus at small detection of the discovery, is divided into two parts: a supersonic core of the spawth of the blade and a dialing, the vortex zone at the back of the blade; The supersonic thread kernel at certain values of the relative pressure drop on the lattice (or the air flow values through the grid) is separated by shock fronts into several areas; The coefficients of energy loss, for small degrees of discovery, decrease with a decrease in the relative pressure drops (with an increase in the rate of expiration of the flow from the nozzle lattice); The greatest contribution to the magnitude of the loss of kinetic energy is introduced by a vortex zone in the inter-tube channel, and not wave phenomena in the core of the flow; Optimization of the flow part of the nozzle apparatus must be carried out in order to reduce areas with vortex flow. The results obtained in this work will be used to develop a methodology for a numerical study of the spatial flow around the nozzle lattices with rotary diaphragms.

Stationary sets of the mean curvature flow with a forcing term

We consider the flat flow solution to the mean curvature equation with forcing in ℝ n {\mathbb{R}^{n}} . Our main result states that tangential balls in ℝ n {\mathbb{R}^{n}} under a flat flow with a bounded forcing term will experience fattening, which generalizes the result in [N. Fusco, V. Julin and M. Morini, Stationary sets and asymptotic behavior of the mean curvature flow with forcing in the plane, preprint 2020, https://arxiv.org/abs/2004.07734] from the planar case to higher dimensions. Then, as in the planar case, we characterize stationary sets in ℝ n {\mathbb{R}^{n}} for a constant forcing term as finite unions of equisize balls with mutually positive distance.

Scale effect evaluation method of axisymmetric body in longitudinal flow

Учет масштабного эффекта имеет большое значение для задач проектирования судов и их движителей. Сложные формы корпусов судов и современных движителей могут быть представлены в виде комбинации простых базовых элементов, одним из которых является тело вращения. В работе представлен метод учета масштабного эффекта для частного случая тела вращения, обтекаемого в продольном направлении. Метод учета основан на численной оценке обтекания тела вращения с помощью методов идеальной жидкости и расчета пограничного слоя. Расчет пограничного слоя осуществляется путем перехода к плоскому течению. В методе моделируются эффекты ламинарно-турбулентного перехода и отрыва пограничного слоя. Моделирование масштабного эффекта осуществляется путем выбора значений ряда параметров из условия согласования расчета с модельными экспериментальными данными и последующего расчета на большие натурные числа Рейнольдса. Показаны особенности влияния параметров масштабирования на характеристики профиля. Эффективность разработанного метода подтверждена сопоставлением с натурными экспериментальными данными. Taking into account the scale effect is important for the design of ships and its propulsors. Complex shapes of ship hulls and modern propulsors may be represented as a combination of simple basic elements. The axisymmetric body is one of its. The paper presents a method of accounting for the scale effect for the special case of a axisymmetric body in longitudinal flow. The method of accounting is based on the numerical evaluation of axisymmetric body flow using the methods of ideal fluid and boundary layer calculation. The boundary layer calculation realized by moving to the flat flow. The method simulates the effects of laminar-turbulent transition and separation of the boundary layer. Modeling of the scale effect is carried out by selecting the values of a number of parameters from the condition of coordination of the calculation with the model experimental data and the subsequent calculation for large full-scale Reynolds numbers. The features of the influence of scaling parameters on the profile characteristics are shown. The effectiveness of the developed method is confirmed by comparison with the full-scale experimental data.

The influence of cavitation and the degree of overlap of the flow of cylindrical flow bodies on the flow pattern, hydrodynamic and spectral characteristics of a flat-type hydrodynamic generator

The paper presents the results of studies of flow behind cylindrical flow bodies in a flat-flow hydrodynamic generator, obtained on the hydrodynamic bench of the experimental base of the National Scientific Center NBMT RAS with the degree of flow blocking by flow bodies St/S0 = 10-80%, Re numbers (0,5-5) · 105, PVH inlet pressure = 0,1-0,8 MPa. It was found that with the same pressure drop two different types of flow can be realized behind the flow bodies: with a developed cavitation zone, within which there is an extensive low pressure area and without it, but with the formation of vortex structures with the presence of centers of cavitation bubbles in them. At a certain value of input to output pressure, which is constant for each value of the degree of overlap of the flow, powerful pressure peaks of the resonant type arise with an amplitude of 2-2,5 times the maximum value of the input pressure. The frequency of occurrence of these pressure peaks increases linearly with increasing pressure drop, and decreases by an order of magnitude with an increase in the degree of overlap of flow up to 80%. The frequency dependence of the number Re for each value of St/S0 is linear. The value of the Strouhal number St with an increase in St/S0 increases linearly with St/S0 = 0,82 and the value St = 1,2.

Investigation of Throttling Characteristics in Supersonic Polyclinic Inlet

This paper presents an experimental investigation of throttling characteristics of a multi-wedge air inlet of a wind tunnel built for flat flow field at M = 2.5. The experiments were performed in a wind tunnel at M numbers of 2.55, 3.05 and 4.05. Results of numerical simulation of the flow in the air inlet, where air flow restriction was implemented by additional heating of the flow in the channel past the air inlet, are given for comparison. Experimental throttling characteristics are in good agreement with the values obtained from computations

EXPERIMENTAL RESEARCH OF CHARACTERISTICS OF CRUSHERS WITH CYCLOIDAL MOTION OF WORKING BODIES

The use of different crushers to obtain the required size of the stone material. This work presents experimental studies of the characteristics of a crusher with a complex movement of working organs. The objectives of the study are, a sieve analysis of the obtained product (crushed stone) and the determination of the optimal speed of the working bodies (rolls) to obtain high-quality cubic shape crushed stone. In the experiment, the raw material is fed into the working space (into the crushing chamber) through the hopper and moves by a flat flow between the rollers. The edges of the rolls roll symmetrically from two sides to the flow of material, approaching in the area of the crushing zone and diverging in the region of the unloading zone. The authors determined the optimal rolls for obtaining high-quality cubiform crushed stone (over 80%). As a result, of the research, it was established that the grain composition of the fraction is within the standard of the Republic of Kazakhstan 1225-2003 t.3 – is obtained cubiform crushed stone, with an rotational speed of rolls of 100-120 rpm.

TESTING THE QUALITY OF SPRAYING FLUID BY USING VARIOUS NOZZLES IN SPECIAL DEVICES LECHLER DROPLEGUL

A variety of devices that help to prevent drops of spayed pesticides from getting into places that are difficult to reach (e. g. under the leaves of cultural plants of on the stem), is offered. Special devices Lechler DroplegUL are designed in a way that nozzles that are embedded in the end of the spraying pipe which is bended backwards, spray diagonally upwards. Data of the quality of spraying fluid by using various sprinklers in special devices Lechler DroplegUL is provided in the article. Two hydraulic flood nozzles Lechler 684.356.30X, mounted in a special holder TwinSprayCap were examined: pneumohydraulic twin flat spray air-injector nozzle Lechler DF 120-03 and hydraulic twin flat spray nozzle Lechler DF 120-02. A transverse repartition and a process of the formation of fluid drops, sprayed using different nozzles were examined. The results revealed that while spraying with a lower working pressure (e.g. 1.5 bar) with two hydraulic flood nozzles Lechler 684.356.30X that are placed in a special holder TwinSprayCap and embedded on a device Lechler DroplegUL, a majority of drops (evenly around 40 ml) get into stand trays that are in a setting place situated 70–110 cm behind the device Lechler DroplegUL, whereas at the approximate 40 cm area away from the setting place there are no drops of sprayed fluid at all. Having the working pressure increased to 3–4 bar, majority of drops (around 60 ml) get into the stend trays that are in a setting place situated 70–110 cm behind the device Lechler DroplegUL. Having the working pressure increased, an unsprayed area, which is situated around the setting place of the device Lechler DroplegUL, gets narrowed: a width of unsprayed area when spraying at the pressure of 2 bar was around 60 cm, whereas when the pressure was 3 bar and 4 bar, the area appeared to be only 20 cm. Circularly sprayed drops, depending on the working pressure, spread around in two strips of width from 1.4 to 1.8 m. An oblong flat flow of the sprayed fluid forms nearby the deflector and the maximum height of the rise of sprayed drops reaches 1.3–1.4 m.

Stabilization of combustion front in supersonic flow using streamer’s discharge

Thermodynamic analysis shows that for flights with velocities exceeding six sound velocities, it is required to burn fuel not in a subsonic but in a supersonic flow. The aim of this work is to investigate the possibility of creating a stationary combustion front in a supersonic flow by igniting the mixture with an attached microwave discharge. Discharges are created on the resonator by means of a pulsed source of quasi-optical microwave radiation. This method of initiation is one or two orders of magnitude more economical than other known methods of plasma ignition and combustion stabilization. A numerical evaluation and comparison with experiment of the propagation velocity of a subcritical streamer discharge in a stationary medium and in a supersonic drifting flow are performed. Experiments have been conducted to ignite a flat flow of propane-air mixture, as well as ignition of the propane stream fed into the airflow, which simulates the operation of the fuel injector. In all cases, the experiments confirmed a steady fuel combustion, which was controlled by the temperature measurements with a thermocouple.