# Potentials for Pressure Gain Combustion in Advanced Gas Turbine Cycles
## 4 Conclusions  
This paper presented comprehensive optimization studies for pressure gain combustion in advanced thermodynamic cycles with intercooling and recuperation. The objective of these studies was to quantify the possible potentials of such a combination, as well as to identify promising gas turbine designs for optimum thermal efficiency. To shed light on this, different pressure gain combustion models for an application in steady-state gas turbine performance simulations were identified and implemented in gas turbine models for conventional, intercooled, recuperated, and intercooled-recuperated engines. These were optimized regarding thermal efficiency for a constant power output at three different first stage turbine blade temperatures. The following conclusions can be drawn:  
* Advanced thermodynamic cycles improved thermal efficiency for all combustion types. An intercooled-recuperated engine using [PERSON]'s PGC model achieved a thermal efficiency increase of 15 PP compared to a simple gas turbine with isobaric combustion. Pure intercooling with [PERSON]'s combustor model increased the efficiency by 10 PP. However, the efficiency gain through recuperation and combined intercooling and recuperation with PGC was lower than for  
Figure 15: Intercooler and recuperator inlet temperatures and SAS mass flow and SAS compressor power for the intercooled-recuperated cycle. the same cycle with isobaric combustion. Only in the intercooled cycle did PGC achieve higher efficiency gains compared to isobaric combustion. Intercooling was therefore favorable for PGC and may create synergies. This behavior was amplified when higher turbine blade temperatures were acceptable. * In comparison to PGC, isobaric combustion attained higher thermal efficiency gains in a simple cycle when the allowable blade temperature constraint was increased. In contrast, reducing the blade temperature constraint resulted in a lower efficiency penalty for PGC than for isobaric combustion. This could affect the compromise between cycle efficiency, which favors high turbine entry temperatures, and blade creep life, which favors low temperatures. In addition, a lower blade temperature constraint reduced the specific work more significantly for PGC than it did for isobaric combustion. Comparison of the Mix models led to the conclusion that the effect of DDT length on thermal efficiency was stronger at lower blade temperature constraints. * The optimum thermodynamic design of an advanced gas turbine with pressure gain combustion can be summarized as follows: The optimization of the intercooled-recuperated cycles yielded OPR between 17 and 35. The LPC and HPC pressure ratios were equal for optimum thermal efficiency. The optimized intercooled cycles had OPR in excess of 48, which was almost twice as high as the intercooled-recuperated cycles. Furthermore, most of the compression took place in the HPC. The recuperated cycles had the lowest OPR with values below 11. The driving temperature difference of the recuperator was almost identical for all combustor models and did not differ from the intercooled-recuperated cycles. The TET for optimum thermal efficiency did scatter, and no general design guideline can be given for advanced cycles. * The required SAS mass flow depended on the advanced cycle and on the underlying combustor model. In general, compared to a cooling mass flow requirement of 20% computed for the simple cycle with isobaric combustion, intercooling maintained this value, and recuperation and combined intercooling and recuperation lowered the value by at least 2 PP and 1.5 PP, respectively. Furthermore, the SAS compressor power requirement could be reduced with recuperation by roughly 50% which is 2.5% of the output power. * The different combustor model performances resulted in very different optimum cycle designs. This stresses the importance of reliable steady-state combustor models, which require more research. Conceptualization, N.N. and D.P. ; methodology, N.N. ; formal analysis, N.N. ; data curation, N.N.