Effect of the Size of Mixing Tube on Air Ingression by an Infrared Suppression (IRS) Device

Infrared suppression device is a critical component of the modern ships and fighter jets, as it passively entrains cold air to attenuate the infrared radiation. In this work, we varied non-dimensional length of the mixing tube in the range of 0.5 to 5 to investigate its impact on the air entrainment and overall outlet temperature. We solved the continuity, momentum and energy equations utilizing finite volume method of Ansys Fluent R 20, incorporating relevant boundary conditions. We observed that the air ingression increases with increasing the length of the mixing tube. We also observed that the outlet temperature continuously decreases with longer mixing tube. At non-dimensional mixing length of 5, the outlet temperature decreases by 23% as compared to the inlet temperature, which is very useful for practical design of IRS devices. Finally, the flow dynamics has been explained through the pressure and temperature contours supplemented by the velocity vectors.