Rethinking the combustor | Turbine technology
Pressure gain combustion: an efficiency step-change for gas turbines
Finno Exergy’s innovative pressure gain combustion (PGC) concept aims to increase gas turbine efficiency by employing pulsed deflagration. It combines a technology well established in piston engines – pressure rise combustion – with the high power densities and continuous shaft outputs of gas turbines. Finno Exergy sees significant potential for retrofitting PGC to the existing turbine fleet, in particular Frame 3 and 5 machines
Fabio Ciccateri CTO, Finno Exergy Oy
Gas turbines will continue to play an important role in global energy systems for decades. They provide dispatchable electricity, mechanical drive for industrial processes and flexibility for power systems incorporating increasing shares of variable renewable generation. They are also widely used in pipeline compressor stations, liquefied natural gas plants, combined heat and power installations and energy-intensive industrial sites. At the same time, the gas turbine market is entering a period of renewed demand. Rapid growth in electricity consumption, electrification and the construction of large data centres — particularly those supporting artificial intelligence applications in the United States — are driving investment in new dispatchable generating capacity.
This growth is putting pressure on a supply chain that cannot be expanded overnight. Order backlogs are increasing, manufacturing slots are filling years in advance and the prices of new gas turbines have risen. For asset owners, replacing an ageing industrial gas turbine may now involve not only substantial capital expenditure and plant modifications, but also a long and uncertain delivery schedule.
Meanwhile, many existing industrial gas turbines remain robust and maintainable assets with considerable operational value. The industry therefore needs solutions that can extend their useful life while reducing fuel consumption and carbon dioxide emissions.
Finno Exergy, a Finnish deep-technology company founded in 2013, is developing a new approach to gas turbine combustion that could deliver such an improvement. Its patented pressure gain combustion, or PGC, technology is designed to increase, rather than reduce, the pressure of the working fluid during combustion. By changing this fundamental part of the gas turbine cycle, the technology has the potential to reduce fuel consumption by more than 10% in suitable industrial gas turbine applications. Combined with a comprehensive life-extension programme, the Finno Exergy retrofit concept could offer asset owners an alternative to purchasing a new gas turbine. The objective is to refurbish the existing machine, extend its operating life and deliver a step change in efficiency at a fraction of the capital cost and implementation time associated with complete replacement.
Lab-scale test combustor. Image: Finno Exergy
In selected applications, this combination could allow an older industrial gas turbine to approach the efficiency range of newer machines while retaining much of the existing package and site infrastructure. Following several years of prototype development, testing and simulation work, Finno Exergy is now preparing for the design and demonstration of a full-scale industrial system.
Rethinking the G combustor The conventional gas turbine has been continuously improved over many decades. Compressor pressure ratios have increased, turbine inlet temperatures have risen and major advances have been made in aerodynamics, materials, coatings, cooling systems and emissions control.
Nevertheless, its basic thermodynamic cycle has remained largely unchanged.
In a conventional gas turbine, the compressor raises the pressure of the incoming air. Fuel is then added and burned in the combustor. The hot combustion gases expand through the turbine, producing the work required to drive the compressor and deliver useful shaft power.
While combustion increases the temperature and energy content of the gas, it does not increase its total pressure. Instead, the combustor normally introduces a pressure loss, reducing the expansion ratio available to the turbine. Pressure gain combustion changes this relationship. Instead of burning fuel in a continuous, approximately-constant-pressure process, a pressure gain system uses a pulsating combustion process to generate a pressure increase. If the pressure of the combustion products at the combustor outlet is higher than that of the air entering the combustor, the turbine can extract more work from the same amount of fuel.
This additional thermodynamic potential can be used to increase power output for a similar fuel input or to reduce fuel consumption while maintaining the same output. For many existing industrial applications, fuel consumption reduction is likely to be the most commercially attractive option. Lower fuel consumption translates directly into lower operating costs and carbon dioxide emissions. In gas transmission and LNG production, the benefit can be even greater
www.modernpowersystems.com | July/August 2026 | 33
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