Numerical modeling on thermofluidic of swirling flow for flue cooling

Diesel engine will emit a lot of high temperature flue gas to heat the exhaust pipe, which will radiate a lot of infrared signals to the outside world. To reduce the heat signal radiated by the exhaust pipe, the cold air film insulation protection method is proposed in this study. However, for the long exhaust pipe, the longer traveling distance makes the hot smoke rise phenomenon obvious, which forms a strong heating effect on the exhaust pipe. Therefore, this study proposes to increase the swirl effect on the cold air film and rely on rotation to increase the adhesion between the film and the tube wall. In this study, a numerical simulation method was used to compare the thermal protection effect of cold fluid on smoke exhaust pipe under swirling and non-swirling conditions with the numerical model verified by experiments. The temperature distribution, velocity distribution, carbon dioxide distribution and heat transfer to the pipe wall are discussed when the mixed jet with hot flue gas reaches steady state under swirling and non-swirling conditions. The results show that the cyclone cold fluid has better thermal protection, and the maximum temperature rise of the pre-swirling cold fluid is 90.39% lower than that of the non-swirling cold fluid. With the increase of cold fluid flow, the pipe temperature rise first decreases and then increases, and there exists a wall temperature rise that shows the best performance when the cold fluid flow is not the maximum.