## 3 Results and Discussion
### \(O_{2}\) Production System Design Process Results
#### 3.2.1 Turbocharging System  
Figure 10 presents the effect of the turbocharger size ratio on the turbocharger behavior (summarized in Table 3), and Figure 11 shows the resulting air conditions at the MIEC membrane and the mass fuel consumption in the burners for each turbocharging configuration. The graphs are intended to be read from right to left, as the sweep was carried out by downsizing the second turbocharger, as explained in the Method section of this document. The bottom axis of the graphs is the turbine scale factor, which is the same as that of the full turbocharger, since no further correction is required, as opposed to for the compressor. The upper axis is the corresponding scale factor of the compressor with respect to the original size, after adjusting its corrected mass flow factor. Scale factors are in percentage; therefore, 100% means that the turbomachinery has equal size to the original engine turbochargers, while lower values mean that the turbomachinery size--maximum diameters--has been reduced. Finally, to facilitate the analysis of Figure 11a, the blue vertical dash-dot line points out the turbocharger size ratio that consumes the least fuel. * _Parallel configuration_ (Figure 4): When the turbochargers are connected in parallel, the turbines share the N\({}_{2}\) inlet line, so it must be divided so that each receives a part of the flow. If the turbines are of the same size, both such in equal amounts of N\({}_{2}\), but if one of them is smaller, the N\({}_{2}\) intake flow will be reduced. This characteristic in parallel arrangement explains the evolution of the behavior in the turbochargers when performing the size sweep of the TCH-2 NA turbo (see Figure 10c). The TCH-1 NA turbocharger has a predictable tendency, as the higher the N\({}_{2}\) corrected mass flow through the turbine, the higher the speed, power, and pressure ratio of the turbine and compressor; however, the same is not true for the TCH-2 ON turbocharger, because there are other factors aside from the N\({}_{2}\) mass flow, affecting its performance. As Table 3 presents, the pressure ratio in TCH-2 ON turbine increases because the rise in the pressure ratio in the TCH-1 NA compressor leads to a higher pressure of N\({}_{2}\) flowing out of the MIEC. However, its temperature is lower due to the drop in fuel consumption (see Figure 11a); as a result of these conditions in the N\({}_{2}\) coming out of the MIEC, the THC-2 ON turbocharger power decreases. After this analysis of turbocharging variation, it is possible to explain the effect on MIEC operation and fuel burner expenditure in parallel configuration (Figure 11a). The increase in power and pressure ratio of TCH-1 NA turbocharger entails an increase in the air mass flow coming in the system and in the air pressure after compression, thus contributing to the increment in the O\({}_{2}\) partial pressure on the feed side. On the other hand, the decrease in THC-2 ON turbocharger power causes a lower suction in the O\({}_{2}\) flow line and and thus leads to to a higher O\({}_{2}\) partial pressure on the permeate side. Despite the latter, the ratio of O\({}_{2}\) partial pressures in the MIEC increases because the growth rate of the partial pressure on the feed side is higher than on the permeate side until it reaches 10% of the turbine scale factor, beyond which the tendency is the opposite. The lowest fuel consumption appears at around 12.5% of the TCH-2 NA turbine scale factor, in the range where the ratio of O\({}_{2}\) partial pressures is the maximum, and within this, where the temperature of the air entering the MIEC is higher. * _Serial configuration_ (Figure 5): When the turbochargers are placed in series, the larger one (low-pressure turbine) always receives all the N\({}_{2}\) flow entering the turbocharging system, while the smaller one (high-pressure turbine) could be bypassed to regulate the flow boosting the turbine and thus to avoid working out of range.