Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 52 7 2019 04 22 Experimental Study of the Supersonic Exhaust Diffuser Spray Cooling System Experimental Study of the Supersonic Exhaust Diffuser Spray Cooling System 1793 1808 3371 10.22060/mej.2019.15138.6038 FA Nematollah Fouladi Space Transportation Research Institute, Iranian Space Research Center, Tehran, Iran 0000-0003-2737-0741 Seyed Ahmadreza Mirbabaei Department of Aerospace Engineering, Sharif University of Technology Mehdi Khosroanjom Space Transportation Research Institute, Iranian Space Research Center, Tehran, Iran Journal Article 2018 10 15 A supersonic exhaust diffuser provides the required test cell vacuum conditions by self pumping of nozzle exhaust gases to the atmosphere in the high-altitude simulator. However, the plume temperature is often much higher than the allowable temperature of the diffuser structure. In the present study, a spray cooling system design method is presented for a supersonic exhaust diffuser. The method is evaluated by performing several experimental tests. First, in order to identify the critical temperature region, the test of the motor with a chamber pressure of 60 bar and a chamber temperature of 3100 °C is performed with a non-cooled metal diffuser. The results indicate that the temperature of the diffuser body in the inlet and ramp regions reaches a temperature above 1500 °C, which leads to the melting and perforation of the diffuser in these regions. Two other tests are performed with average motor chamber pressures of 33 bar and 55 bar along with the spray cooling of the diffuser body. The results show that the designed cooling system keeps the maximum temperatures of the external surface of the diffuser at the values smaller than 200 and 400 °C in these tests. The achieved critical temperatures are well-matched with the respected ones in the design procedure. A supersonic exhaust diffuser provides the required test cell vacuum conditions by self pumping of nozzle exhaust gases to the atmosphere in the high-altitude simulator. However, the plume temperature is often much higher than the allowable temperature of the diffuser structure. In the present study, a spray cooling system design method is presented for a supersonic exhaust diffuser. The method is evaluated by performing several experimental tests. First, in order to identify the critical temperature region, the test of the motor with a chamber pressure of 60 bar and a chamber temperature of 3100 °C is performed with a non-cooled metal diffuser. The results indicate that the temperature of the diffuser body in the inlet and ramp regions reaches a temperature above 1500 °C, which leads to the melting and perforation of the diffuser in these regions. Two other tests are performed with average motor chamber pressures of 33 bar and 55 bar along with the spray cooling of the diffuser body. The results show that the designed cooling system keeps the maximum temperatures of the external surface of the diffuser at the values smaller than 200 and 400 °C in these tests. The achieved critical temperatures are well-matched with the respected ones in the design procedure. https://mej.aut.ac.ir/article_3371_285da2198b2b496c9d447cc4ac6b0734.pdf