Analysis of Starting Failure of Compressed Air Start Marine Diesel Engine

As a main power unit, diesel engines are widely used in modern ships.

The starting methods of diesel engines mainly include manpower starting, electric starting, and compressed air starting. Among them, large and medium-sized diesel engines that are directly returned are started by compressed air. Compressed air starts the diesel engine. The air with a certain pressure is sent to the cylinder through the start valve of each cylinder at the beginning of the power stroke according to the firing sequence of the diesel engine. The piston is moved by the expansion of the compressed air, and the crankshaft rotates through the connecting rod. When the crankshaft speed reaches After the minimum starting speed, the diesel fuel injected into the cylinder will be fired by itself, thus achieving the starting of the diesel engine. 121. The starting performance of the diesel engine directly affects the maneuverability and safety performance of the ship. In severe cases, it will pose a serious threat to the navigation of the ship. .

The composition of the compressed air starting system is one of the main reasons for the difficulty in starting the diesel engine to start the compressed air. 1 The diesel engine fuel system is faulty. The main reason for the difficulty in starting the fuel system due to the failure of the fuel system is fuel quality, fuel delivery system, fuel heating system, fuel oil. Several aspects such as the injection system.

(1) Impact of fuel quality Fuel quality mainly refers to parameters such as freezing point, flash point, cetane number, distillation range and viscosity of diesel. Generally speaking, it is necessary to reasonably select the fuel of the appropriate grade according to the ambient temperature of the diesel engine. For the fuel with poor freezing point and high flashing performance, it should be reasonably heated according to the situation, and the fuel supply advance angle of the diesel engine should be timely. Adjustment.

The failure of the fuel delivery system generally means that the fuel supply pump of the main engine is under pressure, causing the fuel to vaporize, resulting in the fuel not being supplied in time.

The failure of the fuel heating system is mainly due to the adjustment of the viscometer or the heater, so that the viscosity of the fuel is too high or too low, resulting in vaporization or high viscosity of the oil and poor atomization.

The failure of the fuel injection system mainly occurs on the fuel injection pump, the fuel injector and the fuel injection pipe. The failure of the high pressure oil pump often occurs in the wear of the plunger sleeve, the jam, and the breakage of the oil delivery valve spring. Injector failure is often manifested by a stuck needle valve, a blocked orifice, and poor atomization.

During the normal operation of the diesel engine, the gas distribution system regularly opens and closes the inlet and exhaust valves, supplies fresh air to the cylinders, and discharges the exhaust gas in time according to the working sequence of the cylinders and the requirements of the working process. When the diesel engine is started, the compressed air enters the cylinder through the cylinder start valve after the piston is at the top dead center or top dead center.

If the exhaust valve is opened too early, the stroke of the compressed air pushing the piston to work will be reduced. Even in a certain position, the compressed air will directly rush out from the exhaust valve (the exhaust port of the two-stroke diesel engine), and a large amount of air is outside. The venting does not push the piston to move, causing the diesel engine to fail to start.

Sometimes, due to mechanical failure, the intake and exhaust camshafts are not reversing in the forward and reverse reversing directions, causing the forward and exhaust cams of the reversing vehicle to mesh with the valve ejector at the same time, causing chaotic timing of intake and exhaust. The diesel engine cannot be started.

3 start control system faulty compressed air starter diesel engine start control system is generally divided into two categories, one is the direct start valve start system, the other is the indirect open valve start system.

The so-called direct valve-starting system means that the compressed air for starting is distributed through the starting air distributor and then enters the cylinder through the cylinder starting valve. The indirect valve-starting system means that the compressed air for starting enters the cylinder through the cylinder starting valve respectively, and the cylinder starting valve acts on the pilot valve to open the compressed air outputted by the starting air distributor. Faults in the operating system typically occur on starter air distributors, cylinder start valves, main start valves, and other pneumatic and electronic components.

The starting air distributor failure is generally caused by mechanical wear and other causes of the intake timing failure; or the sealing surface of the starting air distributor is worn to cause air leakage, so that the cylinder starting valve cannot be closed in time. The cylinder start valve is mostly caused by the valve plug or the poor sealing of the copper sleeve.

Hu Yongwen: Analysis of the difficulty in starting the diesel engine for compressed air starter 4. The propeller is damaged by external jamming, shafting and bearing bushing and other causes. The propeller of the ship may be wound by the wire mesh material such as the fishing net during the voyage or cause the host to stop or Difficult to start. At the same time, it may not be started due to mechanical jamming, the disc drive is not disengaged, and the protective device is not reset.

Second, common fault phenomena, causes and troubleshooting methods 1 diesel engine can not start the phenomenon of failure of the diesel engine can usually start the following three phenomena: (1) during the operation of the vehicle, the operating system does not work or only part of the action, start air distribution No air is entering.

(2) During the operation of the vehicle, the operating system has an action, and the starting air distributor also has air entering, but the diesel engine cannot rotate or does not reach the minimum starting speed.

(3) During the operation of the vehicle, the control system is normal, the diesel engine can also reach the minimum starting speed, but it can not be ignited or intermittently fired, and the diesel engine is stopped when it is operated to the “working” position.

2. The cause of the failure of the diesel engine can not be started and the troubleshooting method (1) During the starting process, the starting air cannot enter the starting air distributor: it may be caused by some valve parts of the operating system due to jamming or failure; it may also be the main starting valve (Indirect valve-starting system has a main starting valve set in front of the cylinder starting valve and the starting air distributor), the compressed air of the starting system is not opened, resulting in failure to start; in addition, it may be the starting air pressure The control system interlocks and other factors can not be started.

(2) The operating system has action, the starting air distributor also has air in, but the diesel engine can't rotate or can't reach the minimum starting speed: this phenomenon is more common, usually it should be considered firstly that there may be problems with the starting air distributor (more common on board) ), it is often the sliding valve of the starting air distributor that is blocked and cannot be started to ensure air quality. In addition, some important valve parts of the starting and operating system should be lubricated regularly.

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