In order to carry out direct-connected tests of scramjet with flight Mach number 8 and 9

the shock tunnel named FD-14 of China Aerodynamics Research and Development Center was reconstructed to be a supersonic combustor direct-connected test bed with shock heating. Two nozzles were designed for the direct-connected test bed and their outlet Mach numbers are 3.5 and 4.5

which can simulate the combustor entrance conditions of scramjet with flight Mach number 8 and

9

respectively. Using three different chemical reaction models of pure air developed by Park

Gupta and Dunn/Kang

chemical nonequilibrium flows in Mach number 3.5 and 4.5 nozzles are studied by numerical simulation. Besides

differences between the three chemical reaction models are compared and analyzed. Calculation results indicate that

in contraction section of the two nozzles

dissociations of N

2

and O

2

are obvious

but in expansion section of the two nozzles

recombinations of N and O are more remarkable. On the outlet planes of Mach number 3.5 and 4.5 nozzles

mole fractions of NO are respectively 2.3%~2.57% and 4.8%~6.0%

mole fractions of O are respectively 0.04%~0.11% and 0.75%~1.25%

and mole fractions of N are both nearly zero. In the expansion section of two nozzles

the flows are freezing. Among three chemical reaction models

the dissociation degrees of O

2

and N

2

are maximum by using Gupta chemical reaction model

which leads to the maximum mole fractions of NO and O on nozzle outlet. However

distribution laws of each component are same in nozzles and on outlet planes of nozzles acquired from three chemical reaction models.