# Potentials for Pressure Gain Combustion in Advanced Gas Turbine Cycles
## 3 Results and Discussion
### Intercooled-Recuperated Gas Turbine  
For the intercooled-recuperated cycles, pressure ratios and TET are plotted in Figure 14 for a blade temperature constraint of 1100 K. Overall pressure ratios were between those of the intercooled cycles and the recuperated cycles. The HPC and LPC pressure ratios for optimum thermal efficiency highly depended on the selected combustor model. [PERSON]'s model favored a low pressure ratio, whereas the Mix ref model and [PERSON]'s model favored high pressure ratios. This was due to the different underlying mathematical formulations of the combustor models. In contrast to intercooling, LPC and HPC pressure ratios were very close. The pressure ratios of the combustor as a result of the available temperature ratios were smaller with combined intercooling and recuperation compared to pure intercooling because of recuperation. However, they were also higher compared to pure recuperation because of intercooling. Compared to the simple cycle with isobaric combustion, pressure ratios of the compressors were in the same range for all combustors models, but the ideal isochoric model and [PERSON]'s model.  
The intercooled-recuperated cycles had the highest TET. They were even above the simple cycle TET with isobaric combustion. Blade temperature margins were still met, since cooling air temperatures were low due to intercooling. The coupling of TET with OPR is again visible in the data of Figure 14.  
Figure 14: Pressure ratios and TET for the intercooled-recuperated cycle.  
Figure 13: Recuperator inlet temperatures and SAS mass flow and SAS compressor power for the recuperated cycle.  
Figure 15 depicts SAS specifications and intercooler and recuperator inlet temperatures. The SAS mass flow increased slightly when isobaric combustion was coupled with combined intercooling and recuperation. However, using PGC, reduced the SAS mass flow below 21%. Again, the ideal isochoric representation and the model of [PERSON] required SAS mass flows of 16% of the engine mass flow. In addition, the SAS power requirement was again reduced compared to the intercooled cycle, and only \(\approx\)2.5% of the output power was required. The reduced pressure ratio of the combustion and low cooling air temperatures enabled this trend for intercooled-recuperated cycles. Figure 15 also presents inlet temperatures of the heat exchangers. The driving temperature differences between the recuperator hot and cold side were similar for all computed combustor models and in the same range compared to purely recuperated cycles. The intercooled inlet temperatures were almost identical to the recuperator cold side inlet temperatures because LPC and HPC pressure ratios were almost equal. However, compared to pure intercooling, they were sightly increased by \(\approx\)30 K. More specific heat was removed from the cycle.  
In summary, the cycle designs for optimum thermal efficiency were very different. The underlying combustor model and selected advanced cycle had a huge impact on engine mass flow (equivalent to specific work in Figure 6), pressure ratios, TET, and SAS specifications. Only specific heat of the heat exchangers was rather insensitive to the combustor model. Still, the general guidelines for optimum cycle design were identified and the potentials in thermal efficiency quantified.