A diesel generator set is an electrical equipment that converts chemical energy of fuels such as diesel into electrical energy. It mainly consists of a diesel engine and a generator. The diesel engine generates power by burning diesel, and then transmits the power to the generator, which converts the kinetic energy into electrical energy.
It is widely used in emergency power supply, power supply in remote areas, industrial production, shipping industry, military field and many other fields.
What is diesel generator?
Diesel generators are powered by a diesel engine that converts the chemical energy into mechanical energy to drive the generator to generate electricity. The generator convert the mechanical energy into electrical energy according to the principle of electromagnetic induction. (From wikipedia electromagnetic induction: When a changing magnetic field is applied to a conductor, an electromotive force (EMF) is induced, which starts an electric current, when there is a suitable path.)
(Diesel engine working principle)
Diesel generator consists of fuel supply system, electrical control system, cooling system, an excitation and voltage stabilization system, these complex systems are also called a diesel generator set (also known as a DG set or diesel genset).
Diesel supply system:
The diesel supply system is composed of diesel tank, diesel pump, diesel filter and a fuel injector. Diesel in the fuel tank is transferred to the diesel filter through the diesel pump for filtration and atomization, and then enters the fuel injector. The fuel injector sprays diesel mist into the cylinders under high pressure.
Electrical control system:
Diesel generators have various sensors, such as water temperature sensors, which receive and convert electric signals. The electrical control system processes these signals and visualizes them, so that operators can control the diesel generator through a few simple buttons on the control panel, and monitor the real-time operating status of the machine.
Excitation system:
The excitation system consists of an excitation regulator ( which controls the output of the excitation power unit) and an excitation power unit (which provides DC excitation current to the generator rotor winding).
By adjusting the strength of the magnetic field inside the generator, it affects the magnitude of the electromotive force and voltage generated, which has a great impact on the generation of current and the safe and stable operation of the generator itself.
Voltage stabilization system:
The voltage stabilizer is used to stabilize the fluctuating voltage of the current generated by the diesel generator set so that it remains within a suitable range for use by power supply equipment.
Diesel generators are often used as backup power sources for buildings, and are also used in industrial, construction and mining operations that require electricity but are not connected to the grid. Diesel generators are also very good at teamwork. Multiple diesel generators are combined into diesel generator sets through parallel connection and other methods. They can not only provide more power, but also provide higher voltage through corresponding devices, and can also cope with long-term power generation work with ease.
Diesel generator sets are not necessarily all working when they are working. For example, a DG set composed of three DG generators usually only has two running at full capacity, and the other is generally running at low load. At the same time, they can also alternately enter low load operation state, so that the entire DG set can maintain long-term high-efficiency operation. DG sets are very common in power plants, industrial plants and highway and railway construction sites, and can be said to be essential equipment in these places.
Although it is called a diesel generator, it can not only use diesel, but also use natural gas, gasoline and other fuels to generate electricity. Diesel generators are best known for their reliability, because diesel is less likely to degrade or deteriorate over time than gasoline or propane. Diesel engines are also known for their durability, as they can withstand the rigors of continuous use and can run for long periods of time without maintenance. In addition, diesel generators are more efficient than gas generators, which reduces fuel costs and extends operating time.
How does a diesel generator work?
A diesel generator is a device that converts chemical energy into electrical energy. It is divided into two parts, one is the diesel engine and the other is the diesel generator. The working principles of the two parts of how does a diesel generator work will be explained below.
What is the diesel engine working principle?
The working principle of a diesel engine is based on the working principle of an internal combustion engine, including fuel supply, compressed air entering the cylinder, fuel injection into the cylinder, oil and gas mixing and combustion, chemical energy release and conversion into mechanical energy, etc.
Compressed air enters the cylinder
Diesel generators use compression ignition. The first thing that enters the cylinder is the air that has been filtered by the filter. The air enters the cylinder through the intake valve, and then the piston moves upward to compress the air, increasing the temperature and pressure in the cylinder.
Diesel is sprayed into the cylinder
When the piston reaches the top, the injector sprays diesel into the cylinder. Since the air in the cylinder is compressed, the diesel and air are easily ignited and burned after mixing. The injection time and injection amount of diesel are precisely adjusted by the engine control system to ensure complete combustion of the diesel.
Combustion and energy release
Diesel is ignited and burned after mixing with compressed air in the cylinder, producing high-temperature and high-pressure gases. The energy released by these gases pushes the piston downward, thereby driving the crankshaft to rotate. The rotational motion of the crankshaft is converted into reciprocating motion through the connecting rod and piston, ultimately driving the generator rotor to rotate.
What is the diesel generator working principle?
There are two types of diesel generators: DC generators and AC generators, and AC generators are generally more commonly used.
The DC generator (Direct current generator) is mainly composed of a generator housing, a magnetic pole core, a magnetic field coil, an armature and a carbon brush.
Working principle:
When the diesel engine drives the generator armature to rotate, due to the residual magnetism of the generator’s magnetic pole core, the armature coil cuts the magnetic lines of force in the magnetic field. According to the principle of electromagnetic induction, the magnetic induction generates current and outputs the current through the carbon brush.
The AC generator (Alternating current generator) is mainly composed of multiple permanent magnets with alternating north and south poles made of magnetic materials (called rotors) and armature coils made of silicon cast iron and wound with multiple sets of series coils (called stators).
Working principle: The rotor is driven by the diesel engine to axially cut the magnetic lines of force, and the alternating magnetic poles in the stator form an alternating magnetic field in the coil core. When the rotor rotates one circle, the direction and size of the magnetic flux change many times.
Due to the change of the magnetic field, an induced current with changing size and direction will be generated in the coil and the current will be transmitted by the stator coil.
Output power:In order to obtain usable and stable power output, a series of control elements, device protection devices and coil loops are required. Through the rotation of the generator rotor, the induced current is extracted. In order to protect the electrical equipment and maintain its normal operation, the current emitted by the generator also needs to be regulated and controlled by a regulator.
Finally, after being processed by the rectifier and the voltage stabilizer, the output is stable AC power, which can be supplied to power equipment and the power grid to meet power demand.
In summary, the working principle of the diesel generator set is:
- The clean air filtered by the air filter and the high-pressure atomized diesel injected from the injector are fully mixed in the cylinder of the diesel engine.
- Under the pressure of the upward movement of the piston, the volume of the oil-gas mixture is compressed, the temperature rises, and reaches the ignition point of the diesel.
- The diesel in the cylinder is ignited, the oil-gas mixture burns violently, the volume expands rapidly, and pushes the piston downward, which is called work.
- Each cylinder works in a certain order, and the thrust acting on the piston is converted into the force that drives the crankshaft to rotate through the connecting rod.
- The crankshaft drives the generator armature to rotate and periodically cuts the magnetic field inside the generator. According to the principle of electromagnetic induction, an induced electromotive force is generated to obtain voltage, and the electrons in the coil winding begin to flow and generate current.
- Finally, after passing through the diesel generator set’s control system, voltage stabilizer and other electrical components, the diesel generator set is able to produce stable electrical energy.
- In this way, the diesel generator ultimately converts chemical energy into electrical energy, providing portable and reliable power support for people’s lives and work.
What are the 3 types of generators?
Portable diesel generator
It is very convenient and suitable for homes, shops and outdoor work places. It can be very small and can be carried anywhere by hand, it can be also equipped with wheels like a car to easily move to other places as needed. This type of generator is represented by mobility and portability, and it has a container or silent box design to reduce the noise generated during its operation.
Standby diesel generator
This type of generator will stay in one location for most of its life and it usually has a container or machine room because it is designed as a primary fixed power source and is usually combined with multiple standby diesel generators to form a diesel generator set. The most common application scenario is the backup power supply of a power plant or factory. The main operating cost of a standby diesel generator is fuel, and investing in standby diesel generators with optimal fuel efficiency makes good economic sense.
Silent diesel generator
Silent diesel generator is the latest technology of diesel generator, which adopts advanced silent engine and motor, and is equipped with multiple protection and noise reduction measures, including high-efficiency vibration reduction bridge structure, sound-absorbing material soundproof cover, intake and exhaust impedance composite silencer, etc.
It has significant low noise performance, and the unit noise can be less than 75dB(A) (1m away from the unit), which abandons the disadvantage of huge noise generated by traditional diesel generators when generating electricity. It has been widely used in post and telecommunications, communication, hotels, entertainment, hospitals, schools, high-rise buildings, and industrial and mining industries, etc., which have strict requirements on noise.
If you need a diesel generator but don’t want to endure the noise intrusion, silent diesel generator will be the perfect choice.
How to choose a diesel generator set?
In modern times, diesel generator sets have become the core of infrastructure projects, construction sites, and any other type of field work, construction, mining, etc. Therefore, in order for the project to be completed smoothly, choosing the best diesel generator set is the key to the smooth completion of the project, because electricity is always a key node to ensure the progress of the project. Whether the electricity is stable and reliable depends on whether the diesel generator set that provides power guarantee is reliable.
Therefore, when looking for high-quality diesel generator sets, pay attention to some basic tips in order to choose the best diesel generator set. In fact, it is very simple. When choosing a generator, you should first ask yourself the following three questions to help you buy the best diesel generator that meets your requirements.
What type of diesel generator is needed?
Choosing the right type of diesel generator will have a huge impact on the reliability, performance and maintainability of the unit. Many people do not spend enough time evaluating their needs, which can lead to problems later when the diesel generator does not meet actual needs.
Consider the use scenario of the diesel generator, whether it is for home use, small shopping malls or construction sites. It is recommended to choose a silent diesel generator for home and shopping mall use.
Consider whether it is used as the main power source or as a backup power source.
Do you need to generate electricity for a long time?
Do you want a mobile trailer diesel generator or a silent diesel generator or a container diesel generator?
Clarifying these questions will help you quickly determine the type of diesel generator that is suitable.
What diesel generator wattage do I need?
When sizing a generator, you need to take into account the high inrush current that may occur when starting a motor or transformer. This can be six times the load current, and modern high-efficiency motors can even double the inrush current.
It has become common practice to use motor and transformer starting KVA figures as a general standard to try and determine the size of generator you need. This approach works, but you may end up with a generator that is too powerful for the motor, and the choice has no real bearing on the needs of your particular application.
Many modern diesel generators have solutions designed to handle the extra excitation required of the alternator during start-up; these are auxiliary windings or permanent magnets. These provide the generator with three times the rated current to combat any surge peaks from the excitation residual current for at least ten seconds.
Other advanced systems are available to ensure safer generation start-up and more efficient management of power. As a result, there is no need to buy a larger generator so it can cope with the initial power surge that may be encountered at start-up. When you have smarter control over the voltage output, you can achieve better fuel consumption and significantly reduce maintenance costs.
Do diesel generators need to be load paralleled?
Before configuring a larger diesel generator, it is better to consider a more modular approach. Using multiple smaller generators can make your business more flexible, or you may want to use them in parallel to create a load-sharing power source.
This can improve fuel efficiency, and some generators can be taken offline during idle periods or for refueling and maintenance. Then during high-demand periods, each generator can be brought back online to meet the growing power demand.
There are other benefits to choosing to parallel loads over a single larger diesel generator. First, costs and service intervals are shorter because there is no need to stop the entire power system when necessary maintenance is required. Second, equipment reliability is improved because the failure of a single generator can be mitigated by other generators that can increase their power output to make up for the shortfall.
How to maintain diesel generator sets?
Just like the other machinery, the long-term efficiency of diesel generator also requires regular maintenance, such as remove oil sludge, air filter blockage, coolant level, radiator and external ventilation, engine drive belt set.
Refer to the OEM maintenance manual or following suggestions for maintenance methods and frequency:
- After a new unit has run for 200-300 hours, check the valve clearance and check the injector;
- After every 400 hours of operation, check and adjust the drive belt, replace it if necessary; check and clean the radiator chip and drain the sludge in the fuel tank;
- Every 600 hours of operation, replace the lubricating oil and lubricating oil filter;
- Every 800 hours of operation, replace the oil-water separator and fuel filter, check and clean the fuel pipe;
- Every 1200 hours of operation, clean or replace the air filter and adjust the valve clearance;
- After every 2000 hours of operation, replace the coolant, thoroughly clean the water tank, radiator chip and water pipe;
- After every 2400 hours of operation, check the oil injector, thoroughly check and clean the turbocharger, and conduct a comprehensive inspection of the generator set equipment.
FAQ
What is the difference between diesel and gasoline generator?
Compared with gasoline generator, diesel generator has the following advantages:
- Diesel generatorhas a higher power, smaller size and lighter Diesel generators of the same size and weight can generate more electrical energy than gasoline generators.
- Diesel generatorhas higher combustion efficiency due to it uses compression to light up while gasoline generator through electric spark.
- Diesel generators are more durable and suitable for long time in harsh operations.
- Diesel generators are generally quieter and have less vibration than gasoline generators.
However, diesel generators also have their drawbacks:
- The start-up of diesel generators is more complicated, requires preheating, and has higher requirements for the quality of diesel
- Diesel generators have large emissions and cause certain pollution to the environment.
When using diesel generators pay attention to following points:
- Keep the diesel generator clean, perform regular maintenance and repairs to ensure its normal operation.
- Choose suitable diesel and ensure the quality of diesel.
- Follow the safe operating procedures of diesel generators to ensure the safety of operators.
What is KVA meaning? Difference between KVA and KW
While purchasing diesel generator, pay attention to the relationship between rated power and backup power, and the relationship between KVA and KW. Some manufacturers in the market only say “power” and introduce and sell the unit with backup power as rated power.
In fact, backup power = 1.1x rated power. And the backup power can only be used for 1 hour in 12 hours of continuous operation. KVA is apparent power, KW is effective power, and the relationship between them is 1KVA = 0.8KW.
This means that a 55KVA three-phase generator has a true power of 44 kW (55 x 0.8 = 44). The KVA value is important because you need to make sure that the generator you purchase has enough power to run the equipment you intend to use, while also avoiding current overloads that may cause damages and safety hazards to the generator and equipment that it connected to.
How to calculate diesel generator fuel consumption?
Here is an example, if the fuel consumption of a 10KW gasoline generator set is marked as 700g/KW/h, means that it will consumes 700g fuel per KW per hour. However many customers will think that this generator consumes 700g per hour. In fact, it is not the case. It is 700g per 1KW per hour, which means that when this machine runs at full load, it will consumes 700g gasoline to produce 1 kilowatt electricity in an hour, and 10 kilowatts is 10 times 700g.
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