Study On The Influence Of Spherical Structure On The Comprehensive Performance Of Regenerative Cooling Channel

The combustion chamber wall surface in a liquid rocket engine suffers high-temperature gas scour,and may cause ablation under the severe working condition.Regenerative cooling is regarded as one of the effective engine wall cooling ways in view of its advantage of no performance loss.The latest study results showed that adding a spoiler structure in the cooling channel effectively improved the regenerative cooling effect of the wall,but it also brings the problem of high pressure drop.Therefore,it is necessary to optimize the spoiler structure to reduce the channel pressure drop as well as possible while ensuring the heat transfer effect.Based on the software Fluent,the heat transfer and flow characteristics of spherical convex,spherical concave,spherical embedded concave,spherical embedded convex,embedded angle,fluid working conditions have been investigated for a typical regenerative cooling channel,and the influences of different parameters on Nusselt number and friction factor of the channel were analyzed.Through study,it is found that the heat exchange effect can be effectively improved by the spherical convex structure,the spherical concave structure can bring a relatively low pressure drop to the channel,the relative friction factor increase only from 1.06 to 1.08 with the increase of the spherical concave depth.In order to optimize the spherical convex structure,a spherical concave structure is embedded in the spherical convex structure.The spherical convex structure with embedded spherical concave reduces the pressure drop of the channel under certain working conditions.The relative friction factor reaches a minimum value for 1.22～1.54 at different Reynolds numbers when the spherical concave depth is 0.1 mm.The turbulence kinetic energy in the area of the front and end and between the spherical concave gradually increases with the depth of the spherical concave increases.When the spherical concave depth is too deep,a small amount of high-temperature fluid will be retained at the bottom,then reducing the heat exchange effect.In order to optimize the spherical concave structure,a spherical convex structure is embedded in the spherical concave structure.The heat transfer effect at the center of the spherical concave obviously be improved by the spherical concave structure with embedded spherical convex.The relative Nusselt number is the maximum value for 1.46～1.68 under different Reynolds numbers when the spherical convex height is0.4 mm.In addition,when the spherical convex is embedded upstream of the spherical concave,its relative Nusselt number is maximum for 1.73,and the relative friction factor is minimum for 1.21.when embedded in the downstream of the spherical concave,the relative friction factor is 1.38.Finally,within the area of this paper,under different operating pressures,the change of the average temperature of the inner wall and the pressure drop of the channel are 3.3% and 4.6%.The increase extent of the pressure drop of the channel shows respectively decreases and increase with the inlet temperature and heat flux density increase.the average temperature of the inner wall decreases first and then increases with the increase of the inlet temperature.