Improving Combined Cycle Performance with Pressure Gain Combustion in the Gas Turbine

Pressure Gain Combustion (PGC) is an interesting emerging concept to enhance the performance of gas turbines currently based on the Brayton-Joule cycle. Focusing on a F-class gas turbine for land-based power generation, the current work investigates PGC potential in both simple and combined cycle operations by means of an in-house simulation software. The PGC cycle lay-out specifically includes a booster compressor for delivering cooling air to the blades at the first stage of the gas turbine expander. The effects of different amounts of air from the same booster to the PGC system for cooling requirements are also analyzed. Considering reasonable PGC values based on literature data, the efficiency of the gas turbine simple cycle rises by 2.85-3.40 percentage points in the case of no combustor cooling, or 1.85-2.25 percentage points for the most extensive cooling at the combustor, compared to the reference case. The combined cycle efficiency increases too, despite the almost equal power generation at the bottoming steam cycle. Ultimately, a revised parametric analysis with reduced efficiency at the first stage of the gas turbine expander is carried out as well to account for the losses induced by the PGC on the fluid dynamics of the expansion. In this new scenario, the risk of nullifying the advantages related to PGC is real, because of specific combinations of lower expansion efficiency at the gas turbine expander and extensive cooling at the combustor. Thus, better turbine design and effective thermal management at the combustor are fundamental to achieve the highest efficiency.