Common Faults in Diesel Generator Intake and Exhaust System

As an essential support for modern industrial, commercial, and emergency power systems, the stable and reliable operation of diesel generator sets is directly related to production efficiency and electricity safety. In practical use, the intake and exhaust system, as the core part of the diesel engine’s breathing and emission, plays a crucial role in engine power performance, fuel efficiency, and emission levels. However, due to prolonged operation, environmental factors, or component aging, the intake and exhaust system is prone to various faults, which can affect the overall performance of the diesel engine. Therefore, a deep understanding of the composition, common faults, and maintenance methods of the diesel generator's intake and exhaust system is of great significance for ensuring efficient and stable operation of the diesel generator set.

The intake system of a diesel generator is like its respiratory system and is an indispensable part of its normal operation. The system mainly consists of key components such as the air filter, intake piping, compressor, intercooler, and intake manifold. Each component plays an indispensable role in the entire intake process, and they work together to directly affect the diesel engine's power performance.

The air filter has a vital role in the intake system. Its main function is to remove dust and impurities from the air and then deliver clean air into the combustion chamber. Through this process, the air filter effectively reduces wear between the piston and cylinder liner, piston assembly, and valve assembly, thereby extending the service life of these key components. In addition, the air filter also suppresses diesel engine intake noise, creating favorable conditions for the smooth operation of the generator set.

However, if the air filter element becomes clogged or if airflow is affected due to quality issues, the diesel engine will suffer from insufficient air intake. When the amount of air entering the cylinder is reduced, the fuel injected into the cylinder cannot fully combust due to insufficient oxygen. At this point, the diesel engine will experience power loss and emit black smoke, seriously affecting the normal operation of the generator set.

The duct connecting the air filter and the diesel engine's intake manifold (or, for turbocharged diesel engines, the compressor inlet) is usually connected with a section of rubber hose. This rubber hose plays a crucial role in the intake system, as it is responsible for delivering air that has been purified by the filter to subsequent intake components.

If, for some reason, the hose is crushed, internally peeled, or damaged, the airflow will be severely affected. The consequences are the same as a clogged air filter: the diesel engine will experience power loss and black smoke emissions due to insufficient air intake. Therefore, regularly checking the integrity and unobstructed condition of the intake piping is essential for ensuring the stable operation of the generator set.

The diesel engine's exhaust gas turbocharging system is an important part of the intake system. Its main purpose is to increase the pressure of the air entering the cylinders, thereby enhancing air density. In this way, the injected fuel quantity can be increased and power output improved, allowing the diesel generator to deliver stronger power under high-load operation.

However, if the boost pressure is insufficient for some reason, or if the piping downstream of the turbocharger (such as the intercooler or intake manifold connections) is blocked or leaking, the diesel engine may experience power loss due to insufficient air intake. In addition, if the intake port gasket on the cylinder head is damaged and fails to seal properly, the boost pressure will decrease, leading to diesel engine power loss.

When a diesel engine runs normally at idle but produces black smoke under load, it is likely due to a clogged air filter causing insufficient air intake. At this time, a simple method can be used for preliminary diagnosis: temporarily remove the air filter element and start the diesel engine under load. If the black smoke disappears, the air filter element is clogged and should be cleaned or replaced promptly.

If the diesel engine exhibits unexplained abnormal wear on pistons and other components, after ruling out factors such as part quality and engine oil quality, the main cause should be unclean intake air. In this case, the entire intake system, from the air filter inlet to the intake port on the cylinder head, needs to be carefully inspected to confirm whether there is any damage or air leakage. Special attention should be paid to certain special-purpose ports on the intake piping to see if they cause air short-circuiting.

The diesel engine's exhaust system mainly includes the exhaust manifold, turbocharger, and other key components. These components play a crucial role in the operation of the diesel engine, ensuring that exhaust gases are smoothly discharged while using exhaust energy to drive the turbocharger, providing boost for the intake system.

Turbocharger surge is a common fault in the intake and exhaust system, characterized by severe airflow fluctuations and loud roaring sounds. Airflow manifests in periodic and intense pulses, with sharp changes in pressure, velocity, and flow. When surge occurs, engine operating conditions drop, and the engine automatically reduces speed. If the surge cannot be overcome, the engine can only operate at reduced power, causing significant economic loss.

The main causes of turbocharger surge include: blockage in the turbo system flow path (the most common reason), low-speed high-load operation, severely uneven cylinder loads, load clustering, and mismatch between the turbocharger and engine operation. These factors can cause abnormal turbocharger operation, leading to surge faults.

Bearings are a crucial part of the turbocharger, ensuring normal and reliable operation. Floating bearings prevent radial movement of the rotor assembly, completing the positioning of the rotor so that it can rotate stably in the designed position, avoiding friction with the intermediate body or turbine housing.

However, bearing damage is a serious issue that can occur during turbocharger operation. In most cases, bearing damage is caused by low oil pressure, insufficient oil supply or oil cut-off, excessively dirty oil, or metal debris in the oil. These problems prevent proper lubrication and cooling, leading to bearing overheating and failure, affecting turbocharger operation.

Abnormal noise during turbocharger operation may be caused by multiple factors, such as impeller damage, rotor-to-housing clearance being too small, severe wear on bearings and thrust plates, excessive rotor play causing the impeller edges to rub against the housing, or dry friction of moving parts such as bearings and seals. These faults not only affect turbocharger performance but may also lead to further damage.

In addition, turbocharger overtemperature is another potential problem in the exhaust system. The causes mainly include excessively high exhaust temperature, high oil return temperature, high coolant temperature, and reduced boost pressure. When airflow decreases, the turbocharger temperature rises, affecting normal operation. Therefore, timely monitoring and control of these temperature parameters is crucial to prevent overtemperature faults.

During engine operation, if there is a rhythmic and continuous tick-tick sound that increases or decreases with engine speed, it may indicate valve faults. Excessive valve clearance due to wear or incorrect assembly, broken valve springs, or severe camshaft wear causing excessive cam movement can all lead to this abnormal noise.

Valve leakage is another common issue, producing black smoke, low-temperature white smoke, or high-temperature black smoke, as well as power loss and audible air leaks. The contact surfaces of modern diesel engine exhaust valves experience complex working conditions. Repeated movement under high temperature and high pressure requires minimal wear to maintain high efficiency throughout the engine's service life.

In a four-stroke diesel engine, the intake valve opens to allow air into the combustion chamber and then closes to facilitate compression and combustion of the fuel-air mixture. During this stage, the exhaust valve closes, then opens to discharge hot combustion gases, then closes again, repeating the process. Valve contact surfaces face complex and severe contact conditions. Valve closure involves relatively high impact on the valve seat, and proximity to combustion exposes the valve to high temperatures. Exhaust valves, repeatedly exposed to residual hot combustion gases, are prone to carbon buildup. Therefore, regular inspection and maintenance of valve sealing is crucial for normal engine operation and exhaust performance.

The stable operation of a diesel generator set depends on regular maintenance. Any fault in the intake or exhaust system can lead to power loss, increased fuel consumption, and abnormal emissions. Therefore, maintaining and servicing the intake system is essential. Regularly inspecting the air filter, intake piping, and turbo system, and promptly addressing potential issues, is key to ensuring stable operation and extending service life. Similarly, exhaust system maintenance is necessary to prevent blockages.

Diesel engine air filters can be classified as inertial, filtration, or composite types. Their main function is to remove airborne particles and dust, preventing blockages. By ensuring clean air intake during engine operation, the air filter reduces wear between the cylinder liner and piston, extending engine service life.

If dust or other impurities are inhaled, engine component wear increases. It also causes insufficient air intake, incomplete fuel combustion, reduced power, increased fuel consumption, reduced economic efficiency, black smoke emissions, higher exhaust temperature, and higher coolant temperature. Therefore, timely replacement and cleaning of air filters is a critical maintenance measure to ensure normal operation of the diesel generator.

Exhaust gases drive the turbocharger, making the exhaust path critical for normal intake and exhaust operation. Blocked exhaust piping increases backpressure, causing turbocharger operation abnormalities, engine overheating, speed reduction, power loss, and insufficient power.

If deposits in the exhaust pipes accumulate and block the piping, the diesel engine may experience starting difficulties or even fail to start. This usually occurs due to incomplete fuel combustion producing black smoke or solid particles that adhere to the exhaust pipes, causing partial or complete blockage. Therefore, regular cleaning of exhaust pipes to prevent carbon and debris buildup is vital for stable generator operation and longevity.

The intake and exhaust system is the core of normal diesel generator operation. Any component failure can lead to power loss, increased fuel consumption, and abnormal emissions. Regular maintenance, including inspection of air filters, intake piping, turbo systems, and exhaust pipes, and timely resolution of potential problems, is essential for stable operation and prolonged service life. By doing so, diesel generator sets can maintain optimal working conditions, providing reliable power support for production and daily life.