1. Introduction

With the rapid development of science and electronic technology, microcomputer has been widely used in ship power control and monitoring.
In order to improve the fuel economy, reduce the emission requirement, improve the reliability and the flexibility of operation, realize timely adjustment, the electric control common rail diesel engine has become the inevitable trend of development.
After the unremitting efforts of various manufacturers, the all-electric diesel engine was successfully developed in 2003 and verified by the real ship, which marked the development of the diesel engine with another qualitative leap.
    

2. The difference between traditional diesel engine and electric control diesel engine.
   

The traditional diesel engine is controlled by the governor and its fuel injection quantity is controlled by the CAM, which can control the timing of injection and exhaust, and can optimize the performance of the diesel engine under the rated condition.
But when the operation condition of the diesel engine, sea state, the external environment change, fuel quality, camshaft wear or mechanical clearance change lead to injection timing, injection rate, valve timing and valve value deviate from its design parameters, such as the best value, all can affect the economic performance of diesel engine.
The combustion efficiency, fuel consumption and exhaust emission of Marine diesel engines have always been a concern.
According to the provisions of the international maritime organization marpol 73/78, the emission of NOx is strictly restricted.
The most effective way to control it is to lower the maximum combustion temperature and control the time of the gas at high temperature.
The electric control diesel engine is also known as the intelligent diesel engine, which is about to be applied to Marine diesel engine and become an important part of the new diesel engine.
According to diesel engine combustion theory, mainly is the application of electronic control technology, by controlling the fuel injection timing, injection volume, injection rate, pressure and inlet and exhaust valve timing, can effectively achieve the performance of the diesel engine under various load optimization, so as to achieve to meet the latest emissions requirements, to improve the efficiency, reliability, control flexibility and prolong service life.
   

3. Electric control common rail diesel engine.

3.1 the comparison of two mainstream intelligent Marine diesel engines is different:

(1) oil rail.
SulzerRT - flex models of public fuel rail has two, one is 20 mpa of lubricating oil, it is because in the electronic control system output energy co., LTD as a drive starting valve and exhaust valve, cylinder injection control device;
The second is the heavy oil of 100MPa, which is used as the fuel oil of the diesel engine to wait for the injection in the oil track.
The man-b&wme model's public oil rail is only a 20MPa oil slick, which is used as a power oil.
The difference in rail pressure depends greatly on the sealing technology of the oil rail, so the management of the oil rail should be treated differently.
   

(2) raw power.
RT - flex machine adopt the compound CAM crankshaft drives to drive plunger pump in the fuel rail 100 mpa fuel oil pressure, to a predetermined high injection pressure convey sufficient quantity of fuel into the cylinder head level set of high pressure fuel pipe (common rail).
The oil pressure of the servo lubricating oil 20MPa is maintained by a pump driven by the crankshaft through the drive gear.
ME models using input shaft axial hydraulic pump to oil rail lubricating oil (diesel engine with electric pump is before starting input oil), diesel engine by the main oil filter are divided into two after the road, all the way to the normal lubrication of the bearing and the piston cooling;
The diesel engine comes with a booster pump (double head piston pump).
After pressurizing, the lubricating oil reaches high pressure (about 20MPa) to the two large storage containers of each cylinder high pressure oil pump. The high pressure lubricating oil system generally maintains constant pressure and has little fluctuation.
Each cylinder of high pressure oil pump, fuel injection, is controlled by the electric control valve NC rapid high pressure lubricating oil (dynamic) in and out, to drive the rapid upper and lower piston movement, drive the high pressure oil pump plunger generate high voltage (75 ~ 120 mpa) fuel, the nozzle jet atomization;
Electric solenoid valve is controlled by microprocessor NC programming system ECSP, according to the diesel engine performance analysis system ECA OMCP and control the operating system of integrated information issuing commands and actions, thus its diesel common rail is driven lubricating oil of each cylinder of high pressure oil pump power.
   

(3) high pressure oil pump.
The high pressure oil pump of the rt-flex model is a plunger type booster pump, which is not much changed compared with the original.
The ME model USES a hydraulic pressure oil pump.
The former is the drive of the CAM to drive the fuel pump plunger, which is used as the driving force of high pressure oil.
   

(4) oil injection control.
The rt-flex machine is controlled by the control system to send the signal to the solenoid valve. The action of the solenoid valve changes the oil circuit of the servo, thus changing the fuel oil path and completing the injection process.
When controlling the injection of oil, the ME machine also sends a signal to the solenoid valve in the control system. After the solenoid valve changes the servo oil, the servo fuel oil pump is used to pressurize the fuel and complete the injection process.
The former controls servo oil, which controls power oil.
   

(5) sources of fuel oil.
The rt-flex model is derived from the oil track of 100MPa.
The fuel for the ME model is about 1MPa of fuel supplied to the pump.
  

3.2 advantages of electric control common rail diesel engine.

(1) the fuel system can meet both emissions and economic requirements.
The mechanical injection system, in the pre-combustion stage of combustion, is fast, the heat release rate is large, and the gas temperature is high, so the NOx amount in the gas is increased.
If the NOx is reduced by reducing the fuel injection advance Angle, the whole combustion process is longer and the subsequent combustion is serious due to the restriction of the structure, thus reducing the economic performance of the diesel engine.
In addition, the common rail system reduces the combustion temperature at the same time, and also increases the fuel injection rate to shorten the whole combustion process.
Common rail diesel engine provides two operating modes: fuel economy mode and low NOx mode.
In general navigation, fuel economy mode is used to comply with the international maritime organization (IMO) NOx emission standard;
In the special navigation area, the NOx mode is selected and the emission of diesel engine will meet the NOx emission standard of special aviation area.
In addition, the electric control common rail fuel system can control the fuel injection time and fuel injection rate to control the combustion process, thus achieving the goal of controlling NOx amount and improving economy in exhaust.
   

(2) controlled by electromagnetic valve injection, high control precision, high pressure oil will not appear in the bubble and the phenomenon of residual stress of 0, cyclic injection volume changes little, each cylinder combustion pressure, exhaust smoke temperature thermal parameters such as fairly evenly;
Low mechanical load and thermal load;
The internal mechanical force, torque and vibration of diesel engine are small.
  

(3) due to the good atomization of the fuel in each load state, the carbon reduction in the cylinder is obviously reduced, which can prolong the maintenance cycle and reduce the cost of spare parts for the ship.
   

(4) some loads have good operation and low stable speed.
When the diesel engine is operating at a low load, it can maintain a fairly high injection pressure while accurately controlling the fuel injection amount.
 

(5) cancelled large part such as CAM, reduce the weight and volume of the host, thereby increasing the reliability of diesel engines, reduce manufacturing cost, increase the overhaul interval, reduce the maintenance cost, and can prolong life.
   

3.3 the inadequacy and improvement measures of the electronically controlled common rail diesel engine electronic control common rail diesel engine compared with the traditional diesel engine has many advantages, but there are still some shortage of place, is also a common rail diesel engine problems which need to be solved in the future.
   

(1) due to public fuel rail oil pump shaft, initially started diesel engine speed is low, affect the rail pressure, the pressure some fluctuations, will inevitably affect the working condition of common rail system.
It has been suggested that the oil pump is powered by the motor, so the speed of the oil pump is no longer affected by the host, so it is easier to control.
   

(2) the cleaning degree of servo oil of common rail system is higher.
If the servo oil of the common rail system is designed as an independent system, adding a set of lubricating oil cooling and purification machinery will make the management of the common rail system more convenient.
   

(3) the electric control common rail diesel engine only optimizes the exhaust valve, which is not optimized for intake and scavenging, so the whole ventilation process is not optimized.
The improvement of this defect will be more favorable to the performance of diesel engine.
   

(4) there are more electromagnetic valves in the system and the excitation is frequent. Many electronic components work in high temperature, vibration and other environments for a long time, and the probability of damage is high, which leads to the increase of accidents.
In order to better monitor the working condition of diesel engine, the development of new sensor and solenoid valve must be increased.
(5) adopt advanced control mode and improve the function of control software.
Establish a complete diagnosis and alarm system.
   

(6) a large number of computer technologies are adopted, and higher requirements are put forward for ship management personnel.
Strengthen training for managers.
 

3.4 main points of operation and management of common rail diesel engines.

The management of common rail diesel engine is focused on technical management, especially in electronic control system, and higher requirements are put forward on the technical level of shipboard Marine engineers.
It is summarized as follows:

(1) ensure the cleaning of lubricating oil system.
As a part of the lubricating oil is used to control the system, it has a high requirement for cleanliness.
Special attention should be paid to the state of each filter and to be cleaned as required.
   

(2) ensure the seal of the common rail oil pressure pipeline.
The pressure of common rail oil pressure system is high, and it must be observed that its sealing is good during operation.
In particular, the pipeline entering the injector should ensure its sealing, while ensuring that its expansion is not too large to avoid the adverse effects on spray atomization.
  

(3) solenoid valve.
In the control unit of the common rail oil pressure system, the solenoid valve is an important and easily damaged component.
The cleanliness of the lubricating oil must be guaranteed, otherwise, the action of the solenoid valve will be delayed or jammed, or the solenoid valve will become more and more worn, resulting in a series of problems such as poor sealing.
In addition, excessive current will also cause the burning of solenoid valve.
Therefore, in daily management, special attention should be paid to the maintenance of the solenoid valve.
(4) sensor.
The sensor is the main way to control the working condition of the diesel engine.
The damage of the sensor will result in the malfunction of the control system, and the cleaning and maintenance of each sensor must be ensured, especially the sensors working in the harsh conditions should be paid special attention.
(5) NOx emission control.
In order to meet the emission standard of NOx, the electric control common rail diesel engine must improve its operation economy.
So this requires the engineer to grasp a degree.