# Residue Cost Formation of a High Bypass Turbofan Engine
## 8 Conclusions  
This paper presents a general application of thermoeconomic cost accounting to a turbofan aircraft engine, in which the formation and abatement costs of residues are included. The production structure of the turbofan helped to identify where the waste would have been formed and to allocate its costs. For a turbofan engine, the waste heat dissipated in the bypass section was formed by the diffuser and fan; while the waste heat dissipated from the core engine nozzle was formed by the diffuser, fan, compressor, and combustion chamber. Finally, the chemical exergy of exhaust gases was produced only by the combustion chamber. This work intended to show that residue allocation has a considerable effect on the computation of the production cost, and it becomes important when these costs are used in the thermoeconomic diagnosis to assess and quantify a malfunction effect in terms of additional fuel impact. This study also showed that a malfunction not only causes an increase of resource consumption, but it also causes an increase of residue generation.  
The GE90-115B turbofan engine under takeoff conditions and a thrust requirement of 510 kN was taken as a case study. The exergy efficiency of the GE90-115B aircraft engine was 0.36% with a fuel consumption of 5.86 kg\({}_{\text{f}}\)/s and airflow of 2235.82 kg\({}_{\text{a}}\)/s. The total production exergy cost of the aircraft engine was 271.51 MW. According to this methodology, the irreversibility and formation costs of the waste heat dissipated from the bypass section and core engine corresponded to 39.78% and 0.06%, respectively, of the total production exergy cost. The irreversibility and formation costs of the chemical exergy of exhaust gases corresponded to 21.19% and 2.89%, respectively. Regarding the exergoeconomic cost, \(\dot{\Pi}_{P_{T}}\) = 26,754.28 USD/h, of the kinetic exergy produced by the turbofan engine, the methodology was used to determine the contributions of the external resources (61.04%), residues (0.14% and 33.07% for waste heat dissipated from the cS and hS and 3.28% for the chemical exergy of the exhaust gases), and capital and operating costs (2.47%). The malfunction analysis revealed that the performance deterioration of the compressor due to a 10% reduction in its isentropic efficiency under the same flight conditions and thrust requirement reduced the total kinetic exergy production by -0.77 MW, increased the fuel consumption by 0.49 MW, and generated irreversibilities and residues of 0.80 and 0.45 MW, respectively.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & \(\Delta\mathbf{c}_{Pe}^{t}\mathbf{P}(\mathbf{x_{0}})\) & \(\mathbf{c}_{Pe}^{t}(\mathbf{x})|\mathbf{P})(\mathbf{x})\mathbf{MFR}^{t}\) & \(\mathbf{c}_{Pe}^{t}(\mathbf{x})|\mathbf{P})(\mathbf{x})\Delta\mathbf{P}_{s}\) \\  & & **(USD/h)** \\ \hline D & 0 & 0 & 0 \\ F & 0 & \(-\)0.54 & 0 \\ FN & 0 & 0 & 219.80 \\ C & 0 & 86.33 & 0 \\ CC & \(-\)14.72 & \(-\)5.04 & 0 \\ HPT & 0 & 67.72 & 0 \\ LPT & 0 & 54.39 & 0 \\ N & 0 & 7.03 & \(-\)372.45 \\ \hline GE90 & \(-\)14.72 & 209.89 & \(-\)152.65 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Exergoeconomic cost decomposition of fuel impact.  
**Author Contributions:** Conceptualization, S.-P.M. and L.-L.R.; data curation, T.-G.E.V.; formal analysis, L.-M.H. and V.-L.J.; investigation, T.-G.E.V.; methodology, L.-M.H., T.-G.E.V., C.-H.S., and L.-L.R.; project administration, L.-L.R.; software, L.-M.H. and T.-G.E.V.; supervision, S.-P.M. and L.-L.R.; validation, L.-M.H. and C.-H.S.; visualization, C.-H.S.; writing, original draft, L.-M.H.; writing, review and editing, S.-P.M., V.-L.J., and L.-L.R. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Acknowledgments:** [PERSON] gratefully acknowledges the scholarship from the Mexican National Council for Science and Technology (CONACyT) to pursue his postgraduate studies.  
**Conflicts of Interest:** The authors declare no conflict of interest.