The phenomenon of diesel engine runaway is the phenomenon of diesel engine running, especially in the process of small and medium load operation, due to some reasons, the diesel engine speed increases sharply, overspeeding without automatic control, exhaust smoke, sound and vibration.
After the occurrence of “speeding”, as the speed of the diesel engine increases, the leakage between the plunger of the fuel injection pump and the plunger sleeve decreases, and the amount of diesel entering the cylinder increases, causing the speed of the diesel engine to increase again, thus forming a vicious circle. The continuous increase of the diesel engine speed causes the temperature in the cylinder to continue to rise, the expansion of the piston increases, the movement of the parts of the piston connecting rod group increases, and the load increases. After the strength limit is exceeded, the cylinder body will be damaged, the connecting rod will be broken, and the connecting rod will be broken. Serious accidents such as broken crankshaft and broken pistons, cylinder liners and cylinder heads. Therefore, once the diesel engine “speeding” occurs, measures must be taken to shorten the “speeding” time and reduce losses.
One analysis of the cause of diesel engine runaway
A lot of practice has proved that the main cause of diesel engine “speeding” is that the fuel injection pump governor fails, and the other is that extra fuel enters the combustion chamber to participate in the combustion.
1 Reason analysis of fuel injection pump governor
Under normal circumstances, when the load of the diesel engine changes, the governor can automatically adjust the fuel injection pump’s fuel supply to keep its speed stable; on the contrary, when the diesel engine load changes, the fuel injection pump’s fuel supply cannot respond, that is, “Flying car” will happen. The reasons why the fuel supply quantity of the fuel injection pump cannot change with the load are as follows: the adjustment rack rod of the B type fuel injection pump or the adjustment rod of the No. Ⅱ fuel injection pump is stuck at the position of the maximum fuel supply; the plunger spring of the fuel injection pump is broken and the plunger is stuck. High-speed position; the plunger adjusting ring gear or shift fork is loose and shifting to make the plunger out of control; the oil quantity adjusting gear rod is disconnected from the governor lever; the governor lever pin falls off; the governor fly iron pin is broken and flying The iron falls off; the fly-iron pressure bearing is damaged; the governor spring is broken or the elasticity is weakened; too much oil is added to the governor, and the oil viscosity is too high; the governor’s high-speed limit screw or maximum oil limit screw is improperly adjusted.
2 Analysis of the reason for the extra oil entering the combustion chamber
The main ways for extra oil to enter the cylinder are:
Excessive oil in the engine oil pan, excessive wear of the cylinder and piston ring, causing oil to escape into the cylinder; inertial oil bath air filter, residual cleaning oil after cleaning or excessive oil filling, is sucked into the combustion chamber; The oil seal of the turbocharger of the diesel engine is damaged, and the oil enters the combustion chamber; the solenoid valve of the low-temperature starting device leaks diesel oil, causing it to enter the cylinder.
Two emergency measures after “speeding”
As mentioned earlier, after a diesel engine “speeding”, emergency measures must be taken immediately to stop it, otherwise it will severely damage the parts and even cause a major accident. The main methods to stop “speeding” are:
1. Put the speed control handle (pedal) in the non-fuel position;
2. The fuel injection pump with the fuel supply rod or rack rod exposed can quickly pull the rod back to the non-fuel position;
3. If there is a decompression device, quickly place the decompression handle at the decompression position;
4. If the air inlet has a valve, close the valve quickly. If there is no valve, the air filter cover can be removed, and the air inlet can be blocked with clothes or other items;
5. For mechanical vehicles with mechanical transmission system (mechanical vehicles with hydraulic mechanical transmission systems, and with a clutch to lock the clutch), the mechanical vehicles should be put on high gear in time, step on the brake pedal, and slowly release the clutch pedal to force the diesel engine to stop;
6. Quickly loosen the high-pressure oil pipe joints or the low-pressure oil pipe joints that enter the fuel injection pump; when there is no wrench, emergency measures for breaking the oil pipes can also be used.
After the “flying car” is stopped, the cause must be carefully found, and the main moving parts should be inspected if necessary, and the problem should be completely eliminated to prevent the “flying car” accident from recurring and ensure the safe operation of the diesel engine.
