بررسی انتقال حرارت گذرا در دیواره‌های شیپوره همگرا-واگرا

اﯾﻦ ﻣﻘﺎﻟﻪ ﺑﻪ ﺑﺮرﺳﯽ اﻧﺘﻘﺎل ﺣﺮارت ﮔﺬرا و ﻧﯿﺮوی ﭘﯿﺸﺮان در ﻧﺎزل ﻫﻤﮕﺮا-واﮔﺮا ﭘﺮداﺧﺘﻪ اﺳﺖ. ﻣﻌﺎدﻻت ﻣﯿﺎﻧﮕﯿﻦ ﮔﯿﺮی ﺷﺪه زﻣﺎﻧﯽ ﻧﺎوﯾﺮاﺳﺘﻮﮐﺲ ﺗﺮاﮐﻢ ﭘﺬﯾﺮ ﺑﻪ روش ﺣﺠﻢ ﻣﺤﺪود، ﺣﻞ ﺷﺪه اﺳﺖ ﺟﺮﯾﺎن ﻣﺘﻘﺎرن ﻣﺤﻮری، ﺷﺒﯿﻪ ﺳﺎزی ﺷﺪه و ﻧﺘﺎﯾﺞ آن ﺑﺎ آزﻣﺎﯾﺶﻫﺎی ﺗﺠﺮﺑﯽ ﻣﻘﺎﯾﺴﻪ ﮔﺮدﯾﺪه اﺳﺖ. در ﻫﻨﺪﺳﻪﻫﺎی ﻣﺨﺘﻠﻒ، ﭘﺎراﻣﺘﺮﻫﺎی ﺟﺮﯾﺎن و اﻧﺘﻘﺎل ﺣﺮارت ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻣﺪل آﺷﻔﺘﮕﯽ k-ω sst در ﻣﻘﺎﯾﺴﻪ ﺑﺎ ﺳﺎﯾﺮ ﻣﺪلﻫﺎ، اﻧﻄﺒﺎق ﺑﻬﺘﺮی ﺑﺎ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺶﻫﺎی ﺗﺠﺮﺑﯽ دارد. ﺑﺮای ﻃﻮل ﺛﺎﺑﺖ ﻧﺎزل، اﻓﺰاﯾﺶ زاوﯾﻪ واﮔﺮاﯾﯽ ﻧﺎزل ﺑﺎﻋﺚ اﻓﺰاﯾﺶ ﻋﺪد ﻣﺎخ ﺧﺮوﺟﯽ و ﮐﺎﻫﺶ ﻓﺸﺎر و دﻣﺎ در ﺧﺮوﺟﯽ ﮔﺮدﯾﺪ. ﻧﺎزل ﻫﺎی زﻧﮕﻮﻟﻪای ﻋﺪد ﻣﺎخ ﺧﺮوﺟﯽ ﺑﯿﺸﺘﺮ و دﻣﺎ و ﻓﺸﺎر ﺧﺮوﺟﯽ ﮐﻤﺘﺮی از ﻧﺎزل ﻫﺎی ﻣﺨﺮوﻃﯽ داﺷﺘﻨﺪ. ﮐﺎﻫﺶ زاوﯾﻪ در ﺧﺮوﺟﯽ ﻧﺎزل زﻧﮕﻮﻟﻪای، ﺑﺎﻋﺚ اﻓﺰاﯾﺶ ﻋﺪد ﻣﺎخ و ﻧﯿﺮوی ﭘﯿﺸﺮان و ﻫﻤﭽﻨﯿﻦ ﮐﺎﻫﺶ دﻣﺎ و ﻓﺸﺎر ﺧﺮوﺟﯽ ﺷﺪه اﺳﺖ. در ﻧﺎزل ﻫﺎی ﻣﺨﺘﻠﻒ، در ﻣﻘﺎﻃﻌﯽ ﮐﻪ ﺳﻄﺢ ﺛﺎﺑﺘﯽ ﻧﺴﺒﺖ ﺑﻪ ﮔﻠﻮﮔﺎه دارﻧﺪ، اﻧﺘﻘﺎل ﺣﺮارت از دﯾﻮاره و ﻣﻘﺎدﯾﺮ دﻣﺎ در ﺳﻄﺢ و ﻋﻤﻖ دﯾﻮاره ﺛﺎﺑﺖ ﻣﺎﻧﺪه اﺳﺖ. دﻣﺎی ﺧﺮوﺟﯽ ﻧﺎزل زﻧﮕﻮﻟﻪای ﺑﯿﺸﺘﺮ از ﻧﺎزل ﻣﺨﺮوﻃﯽ اﺳﺖ. ﺿﺮﯾﺐ اﻧﺘﻘﺎل ﺣﺮارت ﺟﺎﺑﺠﺎﯾﯽ در ﮔﻠﻮﮔﺎه دارای ﻣﻘﺪار ﺑﯿﺸﯿﻨﻪ ﺑﻮد. ﻧﺎزل زﻧﮕﻮﻟﻪای، ﻧﯿﺮوی ﭘﯿﺸﺮان ﺑﯿﺸﺘﺮی دارد و ﺑﺎ اﻓﺰاﯾﺶ زاوﯾﻪ ﺧﺮوﺟﯽ ﻧﺎزل ﻧﯿﺮوی ﭘﯿﺸﺮان ﮐﺎﻫﺶ ﻣﯽ ﯾﺎﺑﺪ.

Investigation of Transient Heat Transfer inside Walls of ConvergentDivergent Nozzle

This paper focused on the transient heat transfer inside a convergentdivergent nozzle which has applications in propulsion systems. Timeaveraged Navier Stokes equations in the compressible form were solved using the finite volume method. The flow was assumed to be axisymmetric and the results of simulations were compared with available experimental data. The flow and heat transfer parameters were investigated in different nozzle geometries. The results revealed that the SST k-ω turbulence model gives better predictions compared to other applied turbulence models. Also, for a constant length of the nozzle, increasing the divergence angle caused higher exit Mach numbers and lower exit pressure and temperature. Bell nozzles had more exit Mach number, and less exit temperature and pressures compared to the conical nozzles. Decreasing in the exit angle of the bell nozzle led to an increase in the Mach number and thrust and causes lower exit temperature and pressure. For various nozzle shapes, the values of the heat flux and temperatures were nearly constant at the sections which have the same area ratios. The solid surface temperature at the outlet was greater for the bell shape than that for conical shape. The maximum value of the convection heat transfer coefficient occurred at the nozzle throat. The maximum thrust was obtained by bell shape nozzle. Higher outlet angles gave lower thrusts.