Abstract
In this paper, the development features of a single free jet of hightemperature nitrogen interacting with a flat surface were studied. Calculation of the heat exchange process during heating by the attacking jets is very difficult to implement analytically due to complexity of the gas-dynamic processes occurring both in a single jet and in a system of jets interacting with the metal. The computational difficulties are aggravated by the fact that when interacting with the surface the jet as such disappears. The flat (fan) flow interacts with the surface: form, aerodynamic properties and thermal state of the flow strongly differ from those of the original jet. The studies were conducted on the basis of numerical simulation in the FloEFD software and computing complex for multiphysical simulation based on solution of the equations of gas dynamics and heat transfer. The solved system of equations consisted of Navier-Stokes equations, equations of energy and continuity and was supplemented by k – ε turbulence model. A three-dimensional model was developed for simulation, the necessary properties, initial and boundary conditions were specified. In the study of aerodynamics of a single high-temperature jet interacting with the surface, the main defining values were: nitrogen flow rate from the nozzle U0 , nitrogen temperature T, internal diameter of the nozzle d0 , distance from the nozzle section to the surface h, distance from the critical point (point of intersection of the jet axis with the surface) along the flow radius r. Data on the gas velocity decrease as the jet develops due to the loss of initial energy to engage the motionless surrounding gas in motion, is presented. The studies have shown that increase in the initial velocity of gas outflow brings the area of higher velocities closer to the surface both in the jet itself and in the fan jet. This factor contributes to heat transfer intensification. In addition, high speeds increase the total thickness of the fan flow and reduce the thickness of hydrodynamic boundary layer, which increases with distance from the critical point.
Highlights
Calculation of the heat exchange process during heating by the attacking jets is very difficult to implement analytically due to complexity of the gas-dynamic processes occurring both in a single jet and in a system of jets interacting with the metal
The studies were conducted on the basis of numerical simulation in the FloEFD software and computing complex for multiphysical simulation based on solution of the equations of gas dynamics and heat transfer
In the study of aerodynamics of a single high-temperature jet interacting with the surface, the main defining values were: nitrogen flow rate from the nozzle U0, nitrogen temperature T, internal diameter of the nozzle d0, distance from the nozzle section to the surface h, distance from the critical point along the flow radius r
Summary
Национальный исследовательский технологический университет «МИСиС» (119049, Россия, Москва, Ленинский пр., 4). Расчет процесса теплообмена при нагреве атакующими струями весьма трудно реализовать аналитически в силу сложности газодинамических процессов, протекающих как в одиночной струе, так и в системе струй, взаимодействующих с металлом. С поверхностью взаимодействует настильный (веерный) поток, форма, аэродинамические свойства и тепловое состояние которого резко отличаются от таковых для первоначальной струи. Рассмотренные отличия позволяют сделать по крайней мере два вывода: 1 – расчет конвективной теплоотдачи при взаимодействии струи с граничной поверхностью представляется более сложным; 2 – методика расчета конвективной теплоотдачи в этом случае должна базироваться на факторах (режим движения, толщина гидродинамического и теплового пограничных слоев и др.), характерных именно для веерного потока. Расчеты проводили для случая истечения одиночной струи нагретого азота, направленной по нормали к плоской поверхности, величина площади которой существенно превосходит начальную площадь поперечного сечения струи на срезе сопла
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