Rethinking the combustor | Turbine technology


manufacturers and control-system specialists. A life extension partner will be particularly important, as the intended commercial offering combines the pressure gain combustion retrofit with inspection, refurbishment and life extension services appropriate to the selected machine. Finno Exergy is currently engaging with industrial partners and asset owners to establish such a consortium. Pipeline compressor stations, LNG facilities and industrial cogeneration plants are among the applications being considered.


The PGC combustor tested is composed of two chambers in series connected by a restricted-flow section. In addition, to facilitate manufacturing, the test combustor is composed of two twin elements in parallel.


The combustion process consists of four phases: ● Intake. Air and fuel are introduced in the first chamber via intake valves ● Combustion: A controlled ignition source positioned in the top chamber starts the


combustion process. The flame front propagates to the entire combustor. Once the bottom chamber is reached, combustion is completed in a lean environment.


● Exhaust: This phase continues until scavenging valves are opened. ● Scavenging: Air flows in via scavenging valves placed in the top chamber and


scavenges combustion products of the previous cycle. Images: Fenno Exergy


fuel price, baseline efficiency, load profile and retrofit cost. The result also demonstrates why combining pressure gain combustion with life extension may be more valuable than either intervention alone. A conventional life extension programme


restores the condition and availability of an ageing asset, but does not normally transform its cycle efficiency. A combustion retrofit improves performance, but the investment becomes more compelling when the remaining life of the complete machine has also been secured. Together, the two elements could create a


refurbished asset with an extended operating horizon and an efficiency level much closer to that of newer machines. The project should require substantially less capital, site modification and implementation time than complete replacement. The study also identified areas requiring further validation, including sealing, combustor durability, thermal management, emissions, controls, turbine response, rotordynamics and transient engine behaviour.


Fuel flexibility and hydrogen Efficiency improvement is only one part of the technology’s potential value. Industrial gas turbine operators are also considering how their assets can adapt to a future energy system incorporating lower-carbon fuels. A combustion technology intended for long-term deployment must therefore retain fuel flexibility.


Finno Exergy’s system is being developed for operation on natural gas and blends of natural gas and hydrogen. The fast, controlled combustion process and flexible fuel delivery architecture could also support other gaseous fuels as they become


available. A combustion system designed from the beginning around flexible injection and active cycle control may offer advantages compared with conventional systems that must be progressively modified to accommodate increasing hydrogen content. In the near term, however, the largest environmental benefit may come from using less natural gas. A substantial efficiency improvement can reduce emissions immediately, without waiting for new hydrogen infrastructure.


In the longer term, efficiency and fuel flexibility can work together. A more efficient turbine requires less fuel regardless of whether that fuel is natural gas, hydrogen or another renewable gaseous fuel.


Building the industrial demo The next step for Finno Exergy is to move from small-scale validation and simulation to full-scale industrial hardware. The programme will include the design and manufacture of a full-scale combustor, followed by testing under representative pressure, temperature and mass- flow conditions. High pressure rig testing will be essential to validate combustion performance, pressure gain, cooling, durability, fuel flexibility and emissions before installation in a complete gas turbine. The programme must also demonstrate reliable operation during start-up, shutdown and load changes. Industrial gas turbines are not evaluated solely on peak efficiency: availability, maintainability and predictable operating behaviour are equally important. A successful pilot will therefore require co-operation between Finno Exergy, an asset owner, a gas turbine OEM or experienced independent service provider, research and testing organisations, component


A new route to GT modernisation Gas turbine decarbonisation is often discussed in terms of fuel substitution, carbon capture or replacement with renewable generation and storage. All may have a role, but improving the efficiency of the installed fleet should not be overlooked. A gas turbine consuming 10% less fuel can reduce operating costs and carbon dioxide emissions from the moment the upgrade enters service. It can also reduce the amount of future low-carbon fuel required to produce the same output.


At the same time, the current gas turbine supply shortage is changing the economics of asset replacement. Strong electricity-demand growth, AI data-centre development and limited manufacturing capacity mean that a new machine may be more expensive and less readily available than operators previously expected. Existing gas turbines should therefore not be viewed only as ageing equipment approaching retirement. Machines with robust core architecture and established service support may represent strategic assets that can be refurbished, modernised and operated for many additional years. Combined with an appropriate life-extension programme, PGC could offer an alternative between continuing to operate an inefficient ageing machine and purchasing an entirely new gas turbine.


The value proposition is straightforward: retain the serviceable core of the existing asset; restore its mechanical life; replace the conventional combustion system; and achieve a step change in efficiency. In selected applications, the resulting machine could approach the performance range of newer turbines at a fraction of the capital cost and with a substantially shorter delivery and installation schedule. Finno Exergy has demonstrated its combustion concept at small scale, completed an initial gas turbine feasibility study and identified a practical route towards industrial deployment.


Full-scale performance, durability, emissions, controls, turbine interaction and long-term availability must still be demonstrated. However, the potential reward is significant: a retrofit and life-extension solution capable of delivering renewed operating life, lower fuel consumption and reduced emissions while helping asset owners respond to an increasingly constrained gas turbine supply market. By bringing together technology developers, OEMs, independent service providers and asset owners, Finno Exergy aims to transform pressure gain combustion from a promising prototype into a commercially deployable gas turbine modernisation solution.


www.modernpowersystems.com | July/August 2026 | 35


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