The results presented in this paper were computed using three Newton subiterations per time-step and 2700 time-steps per cycle. Here, a cycle is defined as the time required for a rotor to travel a distance equal to the pitch length at midspan. To ensure time-periodicity, each simulation was run in excess of 80 cycles.
The variation of total enthalpy for the three in situ reheat cases and for the no combustion case is shown in Fig. 2. The abscissa indicates the axial location. S1 denotes stator 1, R1 denotes rotor 1, etc. The total enthalpy is calculated at inlet and outlet of each row. Depending on the row type, that is, stator or rotor, the total enthalpy is calculated using either the absolute or the relative velocity. The switch between using absolute or relative velocities generates discontinuities between rows. As shown in Fig. 2, for all fuel injection cases the total enthalpy increases compared to the no combustion case. The largest enthalpy increase is located on the first rotor, where most of the combustion takes place. The combustion and heat release continue throughout the second stator and rotor, as indicated by the total enthalpy variation shown in Fig. 2.
Figure 2. Variation of averaged total en – Figure 3. Variation of stagnation temper-
thalpy (absolute or relative) ature along first row of rotors for the case
without combustion and case 1 of in situ reheat
The stagnation temperature variation along the first row of rotors is strongly inflienced by the in situ reheat, as shown in Fig. 3. Figure 3 shows the averaged, minimum and maximum stagnation temperature for the ft>w without combustion and for case 1 of fbw with combustion. On the pressure side, the averaged temperature of case 1 is approximately 180 K larger than the no combustion case temperature. At the leading edge, however, the averaged temperature of case 1 is approximately 70 K lower than in the no combustion case. On the suction side, the averaged temperature of case 1 is slightly higher than
in the no combustion case. On most of the suction side, the averaged temperature of case 1 is approximately 15 to 20 K larger than the no combustion case temperature.
The averaged temperature indicates that combustion takes place on the pressure side of the rotor airfoil. The existence of small regions where the averaged temperature of the case with combustion is lower than the average temperature of the case without combustion indicates that combustion is not completed. Consequently, the low enthalpy of the fuel injected reduces locally the airfoil temperature. The maximum temperature of the case with combustion is larger than the maximum temperature of the no combustion case over the entire airfoil. On the pressure side, the minimum temperature of the case with combustion is larger than the minimum temperature of the case without combustion. On most of the suction side, however, the minimum temperature of the case with combustion is smaller than the minimum temperature of the case without combustion, indicating that the unburned, cold fuel injected is affecting this region.