Many people feel at a loss when an electronically controlled main engine alarms, and because they do not use the system's own fault detection to identify the fault, they take many detours. Last night I compiled this article by drawing on my own experience and referring to some experience of others. I believe it will provide high reference value for frontline colleagues.
The MOP computer, the human-machine interface of the ME main engine, has functions such as manual input, status monitoring, alarm lists, andTroubleshooting. Among the Troubleshooting functions, a very important one is HCU events, which includes the control and feedback signal monitoring of the FIVA, fuel pump, and exhaust valve in the HCU unit. When an HCU fault occurs, the system automatically records it and displays it intuitively on the real-time monitoring curve. Using this function, the fault point can be located more accurately, helping to quickly resolve the fault.
FIVA Set Point (yellow line): the FIVA position setpoint; the signal comes from the multifunction controller (MPC);
FIVA Feedback Ch30 (green line): FIVA position feedback signal line; the signal comes from the FIVA position sensor; under normal conditions it follows the FIVA position setpoint and almost overlaps it;
FIVA Controller Ch70 (light blue line): FIVA control signal; the signal comes from the MPC;
Plunger Position Ch31 (blue line): fuel pump plunger position feedback signal; the signal comes from the fuel pressure booster position sensor; the signal varies with its stroke, and may also vary with the fuel injection quantity;
Exhaustvalve Position Ch34 (pink line): exhaust valve position feedback signal; the signal comes from the exhaust valve position sensor; the signal changes with its stroke height (normally 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 their normal patterns, 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 fully closed conditions, the value is around 10,000; in the figure it is around 14,000, indicating that it has not been closed to the bottom. The exhaust valve timing may have problems, or there may be strong hydraulic damping from the upper part or other unknown causes.
Figure 3 MPC fault line diagram
3.FFIVA Feedback Ch30 (green line): in the second working cycle, the FIVA feedback signal line deviated from the FIVA control signal line, but immediately returned to normal afterwards.
FIVA Controller Ch70 (light blue line): compared with a normal cycle, the control signal shows a large peak, deviating from the normal pattern diagram. This indicates that the MPC multifunction controller momentarily output an abnormal value.
Plunger Position Ch31 (blue line): while the above two signals were abnormal, the fuel pump plunger position signal immediately became a flat straight line, so it can be determined that the fuel pump stopped working.
The other two lines in the figure are in a normal state, which can be compared with the normal cycle lines for judgment.
It can be judged from the characteristic lines in the above figure that the FIVA control signal returned to normal after a brief abnormality, causing abnormal FIVA action and finally abnormal exhaust valve opening. The system detected the abnormality and immediately stopped the fuel injection command for that cylinder.
Figure 4 FIVA fault line diagram
4. FIVA Feedback Ch30 (green line): In the figure, the FIVA position feedback signal is abnormal in all three cycles. In the first two cycles it deviates from the setpoint but immediately resets. In the third cycle, the FIVA position feedback signal deviates greatly from the setpoint and never resets.
FIVA Controller Ch70 (light blue line)
After the FIVA fault occurs, in order to protect the diesel engine, the control system stops the fuel injection command and continuously issues the exhaustvalve normally-open command.
Plunger Position Ch31 (blue line)
After the FIVA fault, the fuel pump plunger position signal remains at a fixed position and stops fuel injection.
Exhaustvalve Position Ch34 (pink line)
The exhaust valve position signal indicates (always downward) that after the FIVA fault, the exhaust valve is in the open position and gradually closes as the hydraulic oil in the driving pipe leaks.
The above figures show the characteristic line patterns of abnormal exhaust valve opening and fuel injection stop caused by a FIVA fault. A FIVA fault may also cause fuel injection faults, resulting in continuous injection and further leading to cylinder detonation.
Figure 5 Intermittent exhaust valve position fault line diagram
5.Exhaustvalve Position Ch34 (pink line)
The exhaust valve position signal shows intermittent abnormalities in two working cycles.
In the above figure, only the exhaust valve position feedback signal is abnormal, while the other line shapes are normal. Such symptoms are generally caused by sensor faults or electronic interference in the wiring.
Figure 6 Fuel pressure booster position fault line diagram
6.The following abnormalities were recorded:
Plunger Position Ch31 (blue line)
Within two cycles, the fuel pump plunger position signal showed a group of 4 stroke changes. The other curves were normal.
Based on the above curves, it can be judged that the fuel pressure booster pump sensor may be faulty or the signal line may have been subjected to electronic interference.
Figure 7. Typical FIVA valve positioned at the fuel injection position
7.Exhaust valve position feedback curve (the pink curve in the figure: EXHAUST VALVE POSITION), FIVA valve feedback position curve(the green curve in the figure: FIVA FEED BACK) and the fuel pressure booster pump plunger position curve (the blue curve in the figure: PLUNGER POSITION) were all normal before the fault occurred. At the instant the fault suddenly occurs, it can be seen that the exhaust valve position feedback curve drops rapidly and then locks at a position;
The FIVA valve position feedback curve (green line) rises sharply and then locks at a position; the fuel boost pump position curve suddenly rises and then locks at a position. From these three pieces of information, it can be seen that the position curve deviates significantly from the normal position.
The system detects an abnormality and stops the fuel injection command for that cylinder.
Based on this, it can basically be determined that the FIVA valve is stuck at a large travel (abnormal) position.
This paper introduces the meanings of the recording curves in the HCU events interface of the troubleshooting function, and analyzes various typical HCU fault characteristic patterns, hoping to serve as a modest spur to induce more valuable contributions.
