## 3 An Analysis of Application of Steam Injectors in a Boiler Regenerative Feed Water System
### Application of Steam Jet Injectors in Complex Regenerative Feed Water Systems
#### 3.2.2 Application of Two-Stage Regenerative Injectors  
In a single-stage steam injector system, a significant portion of the heat used to heat the feed water is supplied in the overpressure heat exchanger. The maximum steam pressure on the outlet of the injector fed from the 6.6 barA bleed is 1.061 barA, allowing the water to be heated in the mixed heat exchanger up to 100 \({}^{\circ}\)C.  
To obtain the temperatures of the feed water, it is necessary to use a two-stage injector unit. Figure 10 shows a thermal flow diagram of a system with a two-stage injector unit. The steam flux from the first stage injector feeds a vacuum heat exchanger in which the boiler water is heated up to a temperature of 80 \({}^{\circ}\)C and, at the same time, is partially drawn by the second stage injector. Figure 9: Thermal flow diagram of the regenerative cycle with single-stage regenerative injectors. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Control Plane** & \begin{tabular}{c} **P abs** \\ **[barA]** \\ \end{tabular} & \begin{tabular}{c} **t** \\ **[\({}^{\circ}\)C]** \\ \end{tabular} & \
\begin{tabular}{c} **i** \\ **[kJ/kg]** \\ \end{tabular} &
\begin{tabular}{c} _in_ \\ **[kg/s]** \\ \end{tabular} \\ \hline  
6 & 0.0747 \\ \hline \multirow{2}{*}{Assumed Ejection Ratio} & \multicolumn{2}{c}{6 1} & 0.167 & \multicolumn{1}{c}{} & \\ \cline{2-5}  & \multicolumn{2}{c}{6 2} & 0.143 & \multicolumn{1}{c}{} & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Thermodynamic parameters of the working fluid in the control planes of the regenerative cycle with single-stage injectors. Figure 10: Thermal flow diagram of the regenerative cycle with two-stage injectors. The parameters of the steam states in the individual control planes are presented in Table 5, along with the values of mass flows determined on the basis of the system of balance Equations (15) and (11)-(12). \[\left\{ \begin{array}{l}\dot{m}_{21}(i_{21}-i_{22})-\dot{m}_{13}(i_{13}-i_{12})= 0\\ \dot{m}_{21}i_{22}+\dot{m}_{19}i_{19}+\dot{m}_{17}i_{17}+\dot{m}_{10}i_{10}= \dot{m}_{11}i_{11}\\ \dot{m}_{21}+\dot{m}_{19}+\dot{m}_{17}+\dot{m}_{10}=\dot{m}_{11}=1\\ \dot{m}_{15}(i_{15}-i_{16})-\dot{m}_{10}(i_{10}-i_{9})=0\\ \dot{m}_{14}=\dot{m}_{20}+\dot{m}_{15}\end{array} \right. \tag{15}\]  
Calculated from the following relationship, the efficiency of the system is:  
\[\eta_{CRreg2}=\frac{\dot{m}_{1}(i_{1}-i_{4})-\dot{m}_{2}(i_{2}-i_{4})-\dot{m}_ {3}(i_{3}-i_{4})}{\dot{m}_{1}(i_{1}-i_{13})}=0.374941 \tag{16}\]  
Due to the modification, the regeneration degree of the system is:  
\[\varepsilon_{CRreg2}=\frac{\eta_{CRreg2}-\eta_{CRref}}{\eta_{CRref}}=0.518\% \tag{17}\]  
As a result of the application of a two-stage steam jet injector unit, it is possible to obtain a higher steam pressure on the outlet of the injector feeding the deaerator, and thus to heat the water in it to a temperature of 120 \({}^{\circ}\)C. The use of a two-stage unit, despite a significant increase in the water heating temperature in the exchangers fed by regenerative injectors, slightly changes the amount of the recovered latent heat of the exhaust steam from the turbine. Thus, the level of regeneration of the system increases slightly from 0.503% to 0.518%. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Control Plane** & **P abs** & **t** & **i** & \(\dot{m}\) \\
**[barA]** & **[\({}^{\circ}\)C]** & **[kJ/kg]** & **[kg/s]** \\ \hline  
6 & 0.0385 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Thermodynamic parameters of the working fluid in the control planes of the regenerative cycle with two-stage injectors. 3.2.3 Application of Combined Single- and Two-Stage Injectors Units in a Complex Regenerative System  
Looking for further possibilities of waste heat utilization and the improvement of cycle efficiency, systems with the use of additional heat exchangers were considered.