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To support the ongoing energy transition and minimize the environmental footprint of combustion related technologies, the paper presents a novel approach for combustion control in gas turbines and burners. It relies on spatially targeted injection of inert components in the spray core where existent concepts fail to deliver the desired dilution rate and are unable to fully govern the spatial distribution of heat release rates. Combustion process control is thus possible by actively adjusting the composition and mass flow of spatially selective introduction of inert species in the spray, optionally combined with classic, external exhaust gas recirculation, leading to an ultimate fuel-flexible concept which is capable of adjustments to heterogeneous fuels, their reactivity and physical properties. The proof of concept is demonstrated in a gas turbine combustion chamber first by investigating the isolated effects of spatially selective injection of inert species, its comparison to external exhaust gas recirculation and a combination of both. The results confirm the superiority of the approach as spatially selective mixture inertization is capable of 7% reduction of NO emissions with merely 3% increase of CO emissions and even 9% reduction of PM emissions. Furthermore, the concept proved transferrable together with all its benefits to combustion cycles with external exhaust gas recirculation. In this case, the 63% reduction of NO emissions with no observed CO penalty is possible. Simultaneous exploitation of spatially selective inertization, as well as external exhaust gas recirculation forms a fully controllable concept - spatially selective dilution control (SSDC), which enables extensive adjustability of dilution rates throughout the spray core and primary zone of combustion chamber. Compared to baseline case, such approach was proved to simultaneously reduce CO, NO and PM emissions normalized to fuel thermal power for 39%, 63% and 91%, respectively. The confirmation of applicability of the novel approach and its potential to influence the local conditions is opening a series of possible uses, either as an original design feature for future fuel-flexible systems or as a retrofit approach in existent combustion systems.

A pure tire pyrolysis oil produced from waste tires was utilized in a modern 4-cylinder, turbocharged and intercooled, automotive Diesel engine. Due to its low cetane number, cetane improvers, external energy addition or increased compression ratios are generally required for its use in Diesel engines. Successful utilization of pure tire pyrolysis oil is also achievable with the addition of pilot injection but limited to mid- to high-load operating range. The first objective of the present study is therefore focused on further extension of the operating range towards lower loads by novel combined application of the exhaust gas recirculation and tailored main injection strategy. As the second objective, the article provides for the first time an in-depth analysis of the particulate emissions of the tire pyrolysis oil measured with two different methods. In this area it identifies and reasons challenges related to determination of the particulate emissions for alternative fuels. The original contribution of the presented approach thus arises from the holistic assessment of interactions between the exhaust gas recirculation ratios, injection parameters and combustion as well as gaseous and particulate emissions formation phenomena.

To achieve a near zero emission footprint of combustion in power generation, introduction of fuels with low global warming potential, namely low-carbon or carbon neutral fuels and simultaneous reduction of harmful emissions through implementation of advanced combustion concepts is necessary. The study addresses this challenge experimentally by proposing a new approach which combines the benefits of highly oxygenated waste derived fuels, here represented by glycerol, and an introduction of external exhaust gasses recirculation (EGR) aimed for further reduction of NOx emissions. Thus, the recognized role of the high oxygen content in glycerol can positively influence the well-known penalties of EGR, which are commonly perceivable through elevated CO and soot emissions. The measurements were performed with an experimental gas turbine equipped with an exhaust heat regeneration system and feedback loop for 8% and 13% EGR content in compressor intake air. The proposed system layout represents a technically viable and cost-efficient approach for upgrading existent gas turbine setups with a goal to improve their emission footprint. Results confirm that with 8% and 13% EGR rate, NO [sub] x, CO and soot can be reduced simultaneously, thus improving the CO- NO [sub] x and soot- NO [sub] x trade off approximately 2-fold for each species. Additionally, underlying phenomena responsible for observed improvements while increasing EGR rate are identified as an increased soot reactivity, a competing effect of EGR related dilution and an increased primary air temperature together with spray related parameters linked to low stoichiometric ratio of glycerol.