## 3 Results
### Internal Flow  
The flow through the internal channels of the injection system represents an important topic. As the injection fluid is envisioned to be bleed air form the engine compressor, the total pressure loss across the channels from the bleed point to the injection orifices will represent an important parameter in determining the available mass flows and pressures for the injection system. Thus, in this paper, a preliminary study is conducted to determine the influence of the internal geometry of the channel. Four geometries are considered with different diameters of the vane interior injection chamber and characterized based on their influence on the pressure loss inside the injection channels and the overall performance of the turbine.  
Through representing velocity streamlines from the injection chamber inlet, it can be determined that smaller velocities are achieved in the lower part of the chamber, as presented in Figure 8b, because of constant mass flow decrease through injection in the turbine channels. After injection, the fluid interacts with the working fluid creating a deviation followed by the rapid change of direction and attachment to the suction side of the vane, as presented in Figure 8a.  
Figure 8: (**a**) Streamlines distribution in turbine channels (**b**) streamlines distribution in the internal injection chamber.  
Figure 7: Turbine power generation before and after injection for different partial regimes.  
As the injection chamber dimensions decrease, the velocity through these parts of the injection system increase, as can be determined from Figure 9, leading to higher pressure losses. The evolution of these losses with the increase in chamber diameter is presented in Figure 10, with pressure losses computed as the ratio between the total pressure at the chamber inlet and the mean value of total pressure at the injection points. The small dimensions of the chamber led to high pressure losses, over 20%. For higher dimensions, the influence of the chamber diameter decreases, the pressure losses being determined by the injection channels.  
In terms of overall performance, the introduction of the inside flow geometry to the numerical model resulted in lower influence of the injection system. This effect can be determined from Table 6 where the four internal flow configuration results are compared  
Figure 10: Pressure loss variation for different dimensions of the injection chamber.  
Figure 9: (a) Injection flow streamlines for first configuration (3.5 mm chamber diameter); (b) injection flow streamlines for second configuration (3 mm); (c) injection flow streamlines for third configuration (2.5 mm); (d) injection flow streamlines for fourth configuration (2 mm).  
with the ideal case (without considering the internal losses). As the numerical cases are constructed with the injection mass flow set at the chamber inlet, the pressure losses of the internal geometry led to higher pressures needed for injection in order to achieve a 2.5% injection mass flow.  
Comparing the four configurations studied, it was determined that decreasing the dimensions of the injection chamber, which led to an increase in injection pressure (in order to achieve the 2.5% injection mass flow), led to an increased pressure in the injection chamber and a better distribution of the injection fluid across the injection orifices from shroud to hub. This in turn leads to a slightly better deviation of the working fluid and increased influence of the injection system. The higher chamber pressure is shown in Figure 11 which presents a comparison of total pressure distribution for the configuration with the highest and the lowest diameter.