# Research on Data-Driven Performance Assessment and Fault Early Warning of Marine Diesel Engine
## 3 Performance Degradation Trend Analysis and Fault Early Warning of Marine Diesel Main Engines
### Performance Degradation Analysis and Fault Early Warning
#### 3.4.2 Performance Evaluation and Degradation Trend Analysis  
Using the frequently encountered operational condition range as a case study, comprehensive performance evaluation and degradation analysis were conducted for marine diesel main engines. The first 1000 performance samples (collected from 19:00 on 7 July 2020 to 07:20 on 6 September 2020) were selected as the baseline performance sample space, with their statistical means summarized in Table 8. Subsequent calculation of Mahalanobis distances between performance samples from different time intervals and this baseline \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{1}{c}{**Parameter**} & \multicolumn{1}{c}{**Range**} \\ \hline \multicolumn{1}{c}{} & Cylinder 1 Exhaust Temperature (\({}^{\circ}\)C) & 352.71–361.28 \\ \multicolumn{1}{c}{} & Cylinder 2 Exhaust Temperature (\({}^{\circ}\)C) & 350.05–360.57 \\ \multicolumn{1}{c}{} & Cylinder 3 Exhaust Temperature (\({}^{\circ}\)C) & 351.51–361.32 \\ \multicolumn{1}{c}{} & Cylinder 4 Exhaust Temperature (\({}^{\circ}\)C) & 346.1–356.28 \\ \multicolumn{1}{c}{} & Cylinder 5 Exhaust Temperature (\({}^{\circ}\)C) & 355.71–363.86 \\ \multicolumn{1}{c}{} & Cylinder 6 Exhaust Temperature (\({}^{\circ}\)C) & 353.67–361.62 \\ \multicolumn{1}{c}{} & Lubricing Oil Intel Temperature (\({}^{\circ}\)C) & 45.19–46.34 \\ \multicolumn{1}{c}{} & Cylinder 1 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 88.29–89.69 \\ \multicolumn{1}{c}{} & Cylinder 2 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 88.21–89.87 \\ \multicolumn{1}{c}{} & Cylinder 3 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 87.86–89.31 \\ \multicolumn{1}{c}{} & Cylinder 4 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 88.02–89.37 \\ \multicolumn{1}{c}{} & Cylinder 5 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 88.6–90.01 \\ \multicolumn{1}{c}{} & Cylinder 6 Jacket Cooling Water Outlet Temperature (\({}^{\circ}\)C) & 88.32–89.74 \\ \multicolumn{1}{c}{} & Jacket Cooling Water Inlet Pressure (MPa) & 0.4685–0.4791 \\ \multicolumn{1}{c}{} & Fuel Flow Rate (kg/h) & 1935.52–2022.81 \\ \multicolumn{1}{c}{} & Specific Fuel Consumption (g/kWh) & 172.42–182.04 \\ \multicolumn{1}{c}{} & Jacket Cooling Water Inlet Temperature (\({}^{\circ}\)C) & 84.05 (Fixed) \\ \hline \end{tabular}
\end{table} 
Table 7: \(Cont.\)space yielded a time series comprising 22,720 data points. The resultant performance degradation trend curve is presented in Figure 5.  
Figure 5 demonstrates that the Mahalanobis distance exhibited a gradual increase from September 2020 to late January 2021, aligning with empirical patterns of marine diesel main engine performance degradation. However, a sharp surge and pronounced fluctuations in Mahalanobis distances were observed between mid-January and March 2021, indicative of acute systemic performance deterioration. After March 2021, the growth rate of Mahalanobis distances stabilized, demonstrating restoration of normative degradation patterns. This temporal pattern suggests anomalous parameter deviations during the mid-January-March 2021 period, potentially attributable to transient mechanical faults. The subsequent normalization of degradation trends implies successful fault mitigation through operational interventions.