Many people feel confused when an electronically controlled main engine fault alarm occurs, and do not know how to use the system's own fault detection to identify the fault, thus taking many detours. Last night, using my own experience summary and referring to some experience of others, I worked overtime to organize this article. I believe it will certainly bring high reference value to frontline brothers.
The human-machine interface of the ME main engine, the MOP computer, has functions such as manual input, status monitoring, alarm list, and Troubleshooting. Among them, a very important function in the Troubleshooting function is HCU events, which includes monitoring of the FIVA, fuel pump, and exhaust valve control and feedback signals in the HCU unit. When a certain HCU fails, the system will automatically record it and display it intuitively on the real-time monitoring curve. Using this function, the fault point can be found relatively accurately, helping to quickly resolve the fault.
FIVA Set Point (yellow line): FIVA position setpoint, signal from the multi-purpose controller (MPC);
FIFA Feedback Ch30 (green line): FIVA position feedback signal line, signal from the FIVA position sensor; under normal conditions it follows the FIVA position setpoint change and almost overlaps with it;
FIVA Controller Ch70 (light blue line): FIVA control signal, signal from the MPC;
Plunger Position Ch31 (blue line): fuel pump plunger position feedback signal, signal from the fuel booster position sensor, the signal changes with its stroke size and may vary with the injection quantity;
Exhaustvalve Position Ch34 (pink line): exhaust valve position feedback signal, signal from the exhaust valve position sensor, the signal changes with its stroke height (usually the highest and lowest values should be relatively stable);
Tacho Angle Cyl.x (red line): crankshaft angle signal, between two TDCs, the signal gradually increases.
1. Normal curve: The motion curves of each component follow the pattern, with no abnormal changes
2. When an exhaust valve closed position change alarm occurs, it can be clearly seen that the position feedback curve deviates from the normal position (the pink curve in the figure). Under normal closing in place, its threshold is around 10000, but in the figure it is only around 14000, indicating it has not closed to the bottom. The exhaust valve timing may have a problem, or there may be strong hydraulic damping in the upper part or other unknown reasons.
Figure 3 MPC fault linear graph
3. F IFA Feedback Ch30 (green line): The FIVA feedback signal line deviated from the FIVA control signal line during the second working cycle, but immediately returned to normal afterwards.
FIVA Controller Ch70 (light blue line): Compared with the normal cycle, the control signal showed a relatively large peak, deviating from the normal pattern graph. This indicates that the MPC multi-purpose controller momentarily output an abnormal value.
Plunger Position Ch31 (blue line): At the same time as the above two signals were abnormal, the fuel pump plunger position signal immediately became a flat straight line, which can be judged as the fuel pump stopping work.
The other two lines in the figure are in normal state, and their status can be judged by comparison with the normal cycle lines.
Judging from the characteristic lines in the above figure, it is a brief abnormality in the FIVA control signal that returned to normal, causing abnormal FIVA action, ultimately causing abnormal exhaust valve opening. The system monitored the abnormality and immediately stopped the fuel injection command for that cylinder.
Figure 4 FIVA fault line pattern graph
4. FIFA Feedback Ch30 (green line) In the figure, the FIVA position feedback signal showed abnormalities in all three cycles. In the first two cycles it deviated from the setpoint but reset immediately. In the third cycle, the FIVA position feedback signal showed a large deviation from the setpoint and never reset.
FIVA Controller Ch70 (light blue line)
After the FIVA abnormality occurred, in order to protect the diesel engine, the control system stopped the fuel injection command and continuously gave an exhaust valve normally open command.
Plunger Position Ch31 (blue line)
The fuel pump plunger position signal, after the FIVA fault, is at a fixed position and stops fuel injection.
Exhaustvalve Position Ch34 (pink line)
The exhaust valve position signal shows (continuously downward) that after the FIVA fault occurred, the exhaust valve is in the open position and gradually closes as the hydraulic oil in the drive pipe leaks.
The above figures show the various line characteristics of abnormal exhaust valve opening and fuel injection stop caused by FIVA faults. FIVA faults may also cause fuel injection faults, resulting in continuous fuel injection, which in turn leads to cylinder detonation.
Figure 5 Intermittent exhaust valve position fault line pattern graph
5. Exhaustvalve Position Ch34 (pink line)
The exhaust valve position signal showed intermittent abnormalities in two working cycles.
In the above figure, only the abnormal exhaust valve position feedback signal appeared, and the other line patterns were in normal state. This type is generally caused by sensor failure or electronic interference on the line.
Figure 6 Fuel booster position fault line pattern graph
6. The following abnormalities appeared in the record:
Plunger Position Ch31 (blue line)
The fuel pump plunger position signal showed a group of 4 stroke changes within two cycles. The other line patterns are normal.
Based on the above line patterns, it can be judged that the fuel booster pump sensor may have failed or the signal line may have been subject to electronic interference.
Figure 7. Typical FIVA valve positioned at the fuel injection position
7. The exhaust valve position feedback curve (pink curve in the figure: EXHAUST VALVE POSITION), the FIVA valve feedback position curve (green curve in the figure: FIVA FEED BACK), and the fuel booster pump plunger position curve (blue curve in the figure: PLUNGER POSITION) were all normal before the fault occurred. At the instant the fault suddenly occurred, it can be seen that: the exhaust valve position feedback curve dropped rapidly and then locked at one position;
the FIVA valve position feedback curve (green line) rose rapidly and then locked at one position; and the fuel booster pump position curve suddenly rose and then locked at one position. From these three pieces of information, it can be seen that the position curves deviated severely from their normal positions;
the system detected the abnormality and stopped the fuel injection command for that cylinder;
on this basis, it can basically be determined that the FIVA valve was stuck at a large-stroke (abnormal) position;
This article introduces the meaning of each recorded line in the HCU events interface of the troubleshooting function and analyzes the characteristic graphs of various typical HCU faults, in the hope of offering a modest contribution to stimulate further discussion.
