The Lubrication System of Diesel Generator

In the industrial sector, diesel generators play a vital role as essential backup power equipment. Their stability and reliability are of utmost importance. Whether it is for emergency power supply in large factories or independent power supply in remote areas, diesel generators are indispensable. The lubrication system, as a core component of diesel generators, is crucial for ensuring the efficient operation of the engine. Today, let's delve into the mysteries of the lubrication system in diesel generators.

The lubrication system of diesel generators, like that of other engines, primarily performs several key functions.

The lubrication system delivers a certain amount of clean, temperature-appropriate lubricating oil to various friction surfaces, forming a layer of oil film. This reduces direct contact between moving parts, thereby decreasing wear. For example, between the piston and the cylinder wall, lubricating oil forms a thin film that prevents direct metal-to-metal friction, significantly extending the engine's lifespan.

During the lubrication process, lubricating oil carries away metal shavings and impurities generated by friction surfaces, serving a cleaning function. At the same time, it absorbs and removes heat generated by friction, cooling the engine. In the hot summer, lubricating oil acts as a "coolant" for the engine, helping to maintain an appropriate temperature range and preventing the engine from overheating.

The lubrication system also enhances the sealing performance of moving parts such as piston rings and cylinder walls. Lubricating oil fills the tiny gaps between these parts, improving the seal and preventing gas leakage. Additionally, it forms a protective film on metal surfaces, preventing contact with air and thus preventing rust, protecting the internal engine components from corrosion.

Engines are categorized into three main lubrication methods based on how the engine oil is delivered to the friction surfaces of the moving parts: splash lubrication, pressure lubrication, and combined lubrication.

Splash lubrication (also known as splash lubrication) is mainly suitable for friction parts with lower loads, such as cylinder walls, camshafts, and tappets in the valve train. This method involves oil splashing from the gaps in the main bearings and connecting rod bearings of the crankshaft, or from the lower end of the connecting rod hitting the oil in the sump, creating oil droplets or mist that lubricate the friction parts. The advantages of splash lubrication are its simple structure and low cost. However, its disadvantages are also evident: it is less reliable for lubrication, has a higher oil consumption, and is prone to oxidation and contamination. Therefore, it is usually used only in parts with lower lubrication requirements.

Pressure lubrication is suitable for friction surfaces that bear higher loads and have higher relative motion speeds, such as main bearings, connecting rod bearings, and camshaft bearings. This method uses the pressure of the oil pump to deliver oil from the sump through oil passages and pipes to the friction surfaces of the moving parts for lubrication. The advantages of pressure lubrication are its reliability, effectiveness, and excellent cleaning and cooling capabilities. It ensures that lubricating oil is evenly distributed under high pressure to all critical areas, providing full protection for the engine.

Combined lubrication is the lubrication method widely used in modern multi-cylinder engines. It employs both pressure and splash lubrication methods to supply oil to the friction surfaces of the engine. This method not only ensures reliable operation but also simplifies the structure of the entire lubrication system. By combining the advantages of both lubrication methods, combined lubrication better meets the lubrication needs of different engine parts, enhancing the overall performance of the engine.

Since the lubrication systems of various engines are essentially the same, with some differences in the storage of engine oil in large and medium-sized diesel engines, they are divided into two types of circulation systems: dry sump and wet sump.

A dry sump system stores the engine oil separately in an external oil tank. The sump on the engine only collects the oil that returns from the various lubricated parts and then sends it to the oil tank through a suction pump. The oil in the tank is then delivered to the friction surfaces by a pressure pump. This system is suitable for mobile large and medium-sized low-speed diesel engines. The advantage of the dry sump system is its larger oil storage capacity, which can better meet the needs of large engines. Moreover, since the oil tank is located outside the engine, the cooling effect of the oil is better, helping to maintain a stable oil temperature.

A wet sump system stores the engine oil directly in the sump. This system does not require a suction pump; it only needs two pressure pumps to circulate the oil. Medium and small-sized engines usually adopt this circulation system. The wet sump system has a simple structure, low cost, and since the oil is stored directly in the sump, it reduces oil loss during circulation, improving the efficiency of the lubrication system.

The lubrication system of modern engines consists of the following basic parts:

Oil storage and delivery devices include the oil pump, oil passages, and sump. The sump stores the lubricating oil and, in most diesel generators, also serves to cool the oil. The oil pump is the heart of the lubrication system. It draws a certain amount of lubricating oil from the sump, pressurizes it, and continuously delivers it to the surfaces of various parts for lubrication, maintaining the circulation of the oil in the system. The oil pump is usually mounted inside the crankcase, although some diesel generators have it mounted outside. The oil pump is driven by gears through the camshaft, crankshaft, or timing gear.

Oil filtration devices include the primary and secondary oil filters, which remove various impurities from the oil. The function of the oil filter is to remove impurities, metal shavings, sludge, and moisture from the lubricating oil, ensuring that clean oil is delivered to all lubricated parts. The filters in the lubrication system are divided into three types based on their filtering capacity and are installed at different locations in the system. The oil strainer, usually a mesh type, removes larger impurities from the oil with low flow resistance and is installed in series before the oil pump inlet. The primary oil filter removes larger impurities from the oil with low flow resistance and is installed in series between the oil pump outlet and the main oil passage. The secondary oil filter can remove finer impurities from the oil but has higher flow resistance, so it is usually installed in parallel with the main oil passage, with only a small amount of oil passing through the fine filter.

Oil cooling devices include oil coolers or oil radiators, which are used to cool the oil and prevent it from overheating, which could affect the normal operation of the engine. During the lubrication process, oil absorbs a large amount of heat. If the oil temperature is too high, it can degrade the performance of the oil and affect the lubrication effect. Therefore, the oil cooling device is crucial for maintaining a stable oil temperature. Through the cooler or radiator, the oil can dissipate excess heat into the air, ensuring that the oil remains within an appropriate temperature range.

Safety protection devices include safety valves, pressure-limiting valves, and various alarm devices and automatic shutdown devices for low oil pressure in high-power engines. These devices ensure the normal operation of the lubrication system and prevent failures. For example, the pressure-limiting valve restricts the oil pressure output by the oil pump to prevent excessive pressure from damaging the engine. When the oil pressure is too low, the alarm device will sound, alerting the operator to take timely action. If the low oil pressure condition persists, the automatic shutdown device will activate, stopping the engine to prevent damage due to insufficient lubrication.

Indicating devices include oil temperature gauges and oil pressure gauges, which monitor the working condition of the lubrication system. Through these devices, operators can monitor the temperature and pressure of the lubricating oil in real time and promptly detect any potential problems with the lubrication system. For example, if the oil temperature is too high or the oil pressure is too low, the operator can adjust the engine's operating conditions based on the readings to ensure the normal operation of the lubrication system.

To ensure the normal operation of the lubrication system in diesel generators, regular maintenance and care are essential. Here are some common maintenance and care measures:

Regular Oil Change: Lubricating oil will gradually deteriorate and lose its lubricating properties during use. Therefore, regular oil changes are crucial for maintaining the normal operation of the lubrication system. When changing the oil, it is important to select the appropriate type of lubricating oil for the diesel generator and strictly follow the operating procedures to ensure the quality and quantity of the oil.

Inspection of Oil Filters: Oil filters will accumulate a large amount of impurities during use, affecting their filtering efficiency. Therefore, it is necessary to regularly inspect and replace the oil filters. When replacing the filter, ensure its seal to prevent impurities from entering the lubrication system.

Inspection of the Sump: The sump is the container for storing lubricating oil and should be regularly inspected for its seal and cleanliness. If leakage or contamination is found in the sump, it should be repaired and cleaned promptly to ensure the quality of the lubricating oil.

Inspection of the Oil Pump: The oil pump is a core component of the lubrication system and should be regularly inspected for its performance. If any faults are found in the oil pump, it should be repaired or replaced promptly to ensure the normal circulation of the lubricating oil.

Inspection of the Oil Cooler: The oil cooler may become clogged or damaged during use, affecting its cooling efficiency. Therefore, it is important to regularly inspect and clean the oil cooler.

The lubrication system of diesel generators is the key to ensuring the efficient operation of the engine. By understanding the basic functions, lubrication methods, circulation methods, components, and maintenance and care measures of the lubrication system, we can better manage and maintain diesel generators to ensure their stable operation under various conditions. Whether in industrial production or as backup power, the normal operation of the lubrication system is the guarantee of the reliability of diesel generators. It is hoped that this article will help everyone better understand the importance of the lubrication system in diesel generators and provide a reference for daily maintenance and care.