## 4 Conclusions  
In this paper, a two-part study was conducted in order to characterize the performance enhancement method for axial turbines. The system, which implies the injection of a fluid in specific parts of turbine vanes, was studied in terms of overall performance variation, considering in the initial part of the study an ideal injection geometry, and in terms of internal flow characteristics, considering in the second part four configurations of the internal geometry. Considering the influence of the system in turbine channels, the injection process leads to a deviation of the working fluid form the suction side of the vane downstream of the injection points and a decrease in the flow section. Through placing the injection orifices in the vicinity of the minimal section of the vanes, a small overall flow path is obtained, resulting in increased velocities through the channels and higher powers \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Configuration** & \begin{tabular}{c} **Internal Injection** \\ **Chamber Diameter** \\ \end{tabular} & \begin{tabular}{c} **Injection** \\ **Mass Flow [\%]** \\ \end{tabular} & \begin{tabular}{c} **Regime** \\ **[\%]** \\ \end{tabular} & \begin{tabular}{c} **Power without** \\ **Injection [kW]** \\ \end{tabular} & \begin{tabular}{c} **Power after** \\ **Injection [kW]** \\ \end{tabular} & \
\begin{tabular}{c} **Power** \\ **Increase [\%]** \\ \end{tabular} &
\begin{tabular}{c} **Pressure** \\ **Losses [\%]** \\ \end{tabular} \\ \hline Without internal & - & 2.5 & & & 186.3 & 21.5 & - \\ geometry & & & & & 174.8 & 14.0 & 9.7 \\ \hline
1 & 3.5 & 2.5 & & 176.8 & 15.2 & 10.7 \\ \hline
2 & 3 & 2.5 & & 178.3 & 16.2 & 13.3 \\ \hline
3 & 2.5 & 2.5 & & 178.5 & 16.4 & 21.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Turbine power generation for different internal flow configurations. Figure 11: (**a**) Total pressure distribution near the vane hub for first configuration; (**b**) total pressure distribution near the vane hub for fourth configuration. generated by the rotor. For the turbine studied in this paper, a power increase of more than 21% was obtained when compared with the case without injection, with higher values obtained for higher partial regimes. The power increase is achieved without adding mass in the channel as the mass flow is fixed at the rotor outlet, the added mechanical power being a result of a modified flow geometry better adapted to the respective partial regime. The results are in line with previous works conducted on the axial turbine performance enhancement method. The injection system internal flow was discussed in terms of flow characteristics for four configurations of the internal geometry. The decrease in injection chamber diameter leads to higher velocities, as the aim of the system is to achieve a 2.5% injection mass flow, which led to higher pressure losses (over 20% for the geometries studied in this paper). Higher dimensions of the chamber led to lower pressure losses, approximately 10%, with values being determined by the injection channels. In terms of overall performance, the introduction of the internal geometry resulted in a decrease in added power with the best results obtained for smaller dimensions of the injection chamber as the increased pressure in the chamber led to better mass flow distribution across the vane height. Conceptualization, R.E.N. ; methodology, R.E.N. ; formal analysis, R.E.N. ; investigation, R.E.N. ; resources, R.E.N. ; data curation, R.E.N. ; writing--original draft preparation, R.E.N. ; writing--review and editing, D.E.C. and V.A.V. ; supervision, D.E.C. All authors have read and agreed to the published version of the manuscript. This research was funded by the Romanian Research Innovation and Digitalization Ministry through the NUCLEU program under the National Plan for Research Innovation and Development 2022-2027 grant number PN.23.12.01.01. Not applicable. Data are contained within the article and in referenced papers. The authors declare no conflicts of interest.