# Fuel-Water Emulsions as an Alternative Fuel for Gas Turbines: A Project Summary
## 4 Conclusions  
The manuscript presents the results of experimental and numerical studies on the combustion of a fuel-water emulsion with a water content of up to 12% with the addition of a 2% active agent in a miniature gas turbine. The influence of the addition of an emulsifier in an amount of up to 5% on the combustion process and emissions from the gas turbine was also examined. The possibility of an emulsion fuel creating deposits on engine components was also discussed.  
Based on the presented results of experimental and numerical tests, their analysis and literature studies, the following main conclusions regarding the combustion of fuel-water emulsions in gas turbines are made:  
* The use of a fuel-water emulsion leads to the reduction of NOx emissions in miniature gas turbines and full-size turbines. It occurs as a result of the extinction of hot spots in the primary combustion zone, where NO is produced intensively according to the thermal mechanism. However, it should be borne in mind that the nitrogen contained in the fuel in the case of emulsion fuel counteracts the reduction in NOx emissions, and that this effect is more intense the more water there is in the emulsion.
* Adding water to fuel in miniature gas turbines can lead to a reduction in CO emissions. This effect is caused by changes in the distribution of reaction intensity in the combustion zone, which promote the further oxidation of CO.
* When feeding the turbine with a fuel-water emulsion, the total flow rate of the fuel mixture applied to the combustion chamber increases compared with the case in which the turbine operates at the same speed and is fed with standard fuel. However, the consumption of base fuel (after subtracting the mass of water and emulsifier) is reduced in the GTM120 miniature gas turbine. For a rotational speed of 80 krpm and an emulsion containing 12% water, a reduction of 5.46% in the consumption of base fuel was recorded.
* The surfactant used in the tests, added to the fuel in an amount of 2% of the mixture mass, does not affect NOx emissions but has a negative impact on CO emissions. Increasing its content to 5% reduces NOx emissions compared with the emissions recorded for the reference case and has no impact on CO emissions. Moreover, the addition of emulsifiers in the amount of both 2% and 5% does not have a statistically significant effect on the thrust-specific fuel consumption.
* The use of emulsion fuel may lead to the formation of deposits on the elements of the hot section of the gas turbine. The glassy greenish coatings should be attributed to the surfactant, while the deposits in the form of white dust should be attributed to the water present in the emulsion or the synergistic effect of water and the surfactant.  
Conceptualization, P.N. and M.G.; methodology, P.N. and M.G.; validation, P.N.; formal analysis, P.N. and M.G.; investigation, P.N.; resources, M.G.; data curation, P.N.; writing--original draft preparation, P.N.; writing--review and editing, M.G.; visualization, P.N.; supervision, M.G.; project administration, P.N. and M.G.; funding acquisition, M.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
The authors declare no conflicts of interest.