Diesel Engine Starting System

How Does a Diesel Engine Start?

When the diesel engine is in a static state, it must rely on external force to create certain conditions before it can start running. The conditions for realizing the starting of the diesel engine are: there is a certain external torque to overcome the starting resistance torque and drive the crankshaft to rotate. Secondly, the minimum starting speed of the starting operation must be guaranteed. This whole system is called the diesel engine starting system.

The so-called starting resistance torque mainly refers to the friction resistance torque, inertia moment, and compression resistance torque of the piston when the piston compresses gas when the parts move. This makes it necessary to understand the diesel engine lubrication system. The temperature is low, the viscosity of the lubricating oil is large, and the resistance torque is large, so it is more difficult to start in winter than in summer.

The starting speed is to ensure that the gas temperature at the end of compression in the cylinder is higher than the self-ignition temperature of diesel, and at the same time to ensure that the fuel injection pump can establish enough fuel injection pressure to make the diesel spray atomized. The starting speed is about 250~300 rpm, which is A device that obtains the necessary conditions for starting a diesel engine is called a diesel engine starting system.

The common starting methods of diesel engine starting systems are as follows:

1. Start by hand

Use manpower to directly rotate the crankshaft and flywheel with hand crank ropes, etc., to realize the starting of the diesel engine. This is the easiest way to start. The hand crank has a simple structure and reliable operation, but the labor intensity of the workers is high. Therefore, it is only used on low-power diesel engines. Although some diesel engines use other starting methods, they still retain the manual starting structure for backup.

The motor starter is commonly used on diesel generator sets.

2. Starting the gasoline engine

The diesel engine is started with the help of the gasoline engine with less power and is easy to start. This method can ensure that the diesel engine can be started smoothly at a lower temperature, and the starting time and times are not limited. However, the starting system is complicated in structure, requires two fuel supply systems, and is inconvenient to operate.

3. Compressed air starting

Compressed air starts to fill the compressed air into the cylinders according to the explosion sequence of each cylinder of the diesel engine. Because the compressed air expands in the cylinder, it pushes the piston to move, drives the crankshaft to rotate, and realizes the starting of the diesel engine. This method is characterized by a large starting torque, and rapid and reliable starting. However, the structure is complex, and sufficient compressed air needs to be prepared. At present, it is widely used in large and medium-sized diesel engines.

4. Motor Start

Electric starting system: The electric starting system consists of a battery, regulator, charger, starter, etc.

To start the diesel engine, first press the start button to connect the electromagnetic switch circuit between the battery and the starter to make the starter rotate. At the same time, under the action of the electromagnetic switch, the pinion of the front axle of the starter is dialed into the flywheel ring gear of the diesel engine to start the diesel engine.

After the diesel engine starts to catch fire, the start button should be released immediately, the power supply should be cut off, the spring on the electromagnetic switch will return to its original position, and the starter gear should be disengaged from the ring gear.

In recent years, chargers have been improved to replace commutator rectifier DC generators with silicon rectifier generators. Due to the advantages of large specific power, small size, and good low-speed charging performance, the silicon rectifier alternator has the potential to gradually replace the DC generator.

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In the starting system of a diesel engine, a variety of different methods are used to ensure that the engine can start under various conditions. From simple manual starting to the use of compressed air and electric starters, these methods have their own advantages and applicable scenarios. With the continuous advancement of technology, the starting system of diesel engines is also constantly evolving and adapting to different working environments and needs. At the same time, the provision of hydraulic pumps and other accessories also facilitates the maintenance of diesel engines.