Many users believe that running diesel generator sets under long-term no-load or low-load conditions is beneficial, especially during equipment testing or maintenance. However, this is not the case. Long-term no-load or low-load operation can lead to several potential hazards and even shorten the lifespan of the equipment. In this article, we will analyze the various issues caused by long-term no-load and low-load operation of diesel generator sets.
Incomplete Combustion and Carbon Formation
When a diesel generator set operates under no-load or low-load conditions, the engine's cylinder pressure and temperature are low. The temperature in the combustion chamber does not reach the ideal combustion state. This incomplete combustion results in unburned diesel and oil forming carbon deposits inside the engine. Carbon deposits accumulate on components such as the valves, pistons, and intake paths, gradually affecting the engine's power and efficiency. In severe cases, carbon buildup can even clog the fuel injectors, affecting the proper functioning of the fuel system.
Additionally, low-load operation causes the diesel generator to emit large amounts of white smoke. This occurs because incomplete combustion leads to unburned diesel being discharged along with exhaust gases, causing environmental pollution. As carbon builds up, the engine's power gradually decreases, potentially requiring an early overhaul.
Lubrication System Issues and Oil Contamination
No-load or low-load operation causes the engine oil temperature to remain low, reducing the oil's lubrication effectiveness. When the oil temperature and pressure are too low, it cannot adequately lubricate the engine's internal components. This results in increased friction within the engine, accelerating wear on parts.
Moreover, incomplete combustion allows unburned diesel and engine oil to enter the lubrication system, contaminating the oil. Impurities, water, and unburned fuel in the oil reduce its cleanliness and lubricating properties, speeding up engine wear and increasing the risk of failures.
Turbocharger Damage
For diesel generator sets equipped with turbochargers, low-load operation can lead to turbocharger damage. During low-load operation, the exhaust temperature and boost pressure are lower, which reduces the turbocharger's efficiency. This causes oil to seep into the boost chamber. As oil is drawn into the combustion chamber, the turbocharger's sealing effect diminishes, leading to turbocharger failure. Long-term low-load operation accelerates turbocharger wear and may lead to premature failure, impacting the overall performance of the generator set.
Increased Mechanical Wear
During low-load operation, the engine's cylinder pressure is lower, and components such as piston rings and valves cannot function properly. Unburned fuel and oil enter these parts, leading to increased wear. Over time, poor sealing becomes more severe, reducing the engine's compression ratio, lowering power output, and increasing fuel consumption.
Long-term low-load operation also affects the engine's thermal expansion, causing increased gaps between components such as cylinder liners and pistons, which accelerates wear. This not only affects engine performance but also brings forward the need for major repairs, increasing the costs of maintenance and parts replacement.
Effects on Cooling and Heat Dissipation Systems
The cooling system of a diesel generator set needs to maintain a specific temperature range to ensure proper engine operation. During no-load or low-load operation, the coolant temperature remains low and cannot effectively dissipate the heat produced by the engine. This reduces the cooling efficiency and causes the engine's working temperature to be too low. At low temperatures, the oil's lubricating properties weaken, and water and impurities tend to accumulate inside the engine, increasing the risk of overheating.
Additionally, prolonged low-temperature operation can prevent the engine from expanding fully, leaving gaps that cause oil and water leaks. Failures in the cooling system and poor heat dissipation directly affect the lifespan and efficiency of the diesel generator set.
Fuel System Hazards
When a diesel generator set operates under low load, the fuel injection system's working pressure is lower, causing poor fuel atomization and uneven mixing of fuel and air. This worsens the combustion conditions in the combustion chamber, leading to incomplete combustion and unburned fuel being expelled into the exhaust system. This incomplete combustion leads to carbon buildup, which can clog the fuel injectors and even damage the fuel system, affecting its normal operation.
At low load, fuel consumption is reduced, and the efficiency of the combustion system declines. This results in fuel wastage and increased pollutant emissions, raising the operational costs of the diesel generator set.
Shortened Service Life and Increased Maintenance Costs
Long-term no-load or low-load operation causes severe damage to various systems of the diesel generator set. This accelerates wear on components and shortens the engine's lifespan. With the accumulation of carbon buildup, oil contamination, and turbocharger damage, the generator set's efficiency declines, and failure rates increase, leading to more frequent maintenance and higher costs.
Because long-term low-load operation worsens the working environment of the generator set, its service life is significantly shortened. Major repairs and part replacements will be needed earlier, which not only increases repair costs but also affects the equipment's economic efficiency.
Recommendations for Proper Use of Diesel Generator Sets
To avoid the various problems caused by long-term no-load or low-load operation, users should follow these guidelines when using diesel generator sets.
Appropriate Load: Diesel generator sets should operate at least at 30% load to ensure the engine reaches its normal working temperature and avoids incomplete combustion. The ideal load range is 60% to 75%, which helps improve efficiency and extend the service life of the generator set.
Startup and Load Connection: When starting the generator, let it run for 3 minutes to warm up. After the temperature stabilizes, gradually increase to the rated speed and connect the load only after the voltage stabilizes.
Limit No-Load Time: No-load operation should be limited to 5 minutes and used only for short-term testing and diagnostics. Avoid long-term no-load operation.
Temperature and Cooling Management: Ensure the coolant temperature exceeds 60°C before load operation and maintain the cooling system at saturation to ensure effective engine heat dissipation.
Regular Inspections and Maintenance: Regularly inspect critical components such as engine oil, injectors, and turbochargers. Ensure all systems are functioning properly and address potential issues in a timely manner.
Conclusion
Long-term no-load or low-load operation of diesel generator sets causes a range of issues, including carbon buildup, oil contamination, and turbocharger damage. These problems not only reduce equipment efficiency but also shorten its service life and increase maintenance costs. To ensure the efficient and safe operation of diesel generator sets, users should avoid prolonged no-load or low-load operation, select appropriate loads, conduct regular maintenance, and address faults promptly. With proper operation and maintenance, diesel generator sets can provide stable and lasting service, ensuring long-term, safe operation.
