In modern society, the importance of a stable power supply to national economic development and national defense is beyond question. However, in the vast plateau regions of China, the unique natural and environmental conditions pose significant challenges to conventional diesel generator sets designed for low-altitude operation. These challenges not only degrade generator performance and reliability, but also cause substantial economic losses in related sectors. This article provides an in-depth analysis of the effects of high-altitude environments on the performance of diesel generator sets and proposes effective countermeasures, with the aim of offering valuable references for industry practitioners and researchers.
- Power De-rating: Most conventional diesel generator sets currently manufactured in China are rated at altitudes below 1,000 m. When operating above this elevation, the air becomes increasingly thin and oxygen concentration decreases. Diesel engines rely on sufficient oxygen to support complete combustion. Reduced air density leads to insufficient intake air and deteriorated combustion conditions, preventing the engine from delivering its rated output power. In general, when generator sets are used at altitudes above 1,500 m, the impact of altitude on power output must be taken into account. For every 300 m increase in altitude, diesel engine power typically decreases by approximately 4%. For example, at an altitude of 4,000 m, the engine output power may be only about 60% of that at sea level.
- Increased Fuel Consumption: Due to thinner air and incomplete combustion, more diesel fuel is required to achieve the same power output, resulting in increased fuel consumption. This not only raises operating costs but also reduces the overall economic efficiency of the generator set.
- Increased Thermal Load: Incomplete combustion and reduced intake air volume prevent heat from being dissipated effectively during engine operation, leading to an increase in thermal load. Elevated thermal stress accelerates the aging of engine components, shortens service life, and increases the likelihood of failures.
- Degradation of Electrical Performance: At high altitudes, the reduced air density lowers the electrical breakdown voltage of electrical components, making them more prone to insulation breakdown under the same operating voltage. This directly affects the reliable operation of generator sets. In addition, increased ultraviolet radiation at higher altitudes accelerates the aging of rubber and plastic components, further reducing the overall reliability of the generator system.
- Reduced Cooling Performance: Thin air reduces both cooling airflow pressure and mass flow, while the boiling point of water decreases with altitude. As a result, the heat dissipation capability of conventional cooling systems deteriorates, causing higher operating temperatures that negatively affect performance and service life. In particular, open cooling circulation systems are not suitable for high-altitude environments. Instead, pressurized closed-loop cooling systems should be used to raise the coolant boiling point and improve cooling effectiveness.
- Starting Difficulties: High-altitude regions are characterized by low ambient temperatures and low atmospheric pressure. During engine starting, the pressure and temperature at the end of compression are often insufficient. Furthermore, turbocharging devices can restrict intake airflow during starting, further worsening starting performance. These factors make starting diesel generator sets particularly difficult, especially in remote field environments where no auxiliary power source is available.
Given the significant challenges posed by high-altitude environments, effective mitigation measures are essential. These measures can restore generator performance and enhance reliability and economic efficiency under plateau conditions. Key strategies are discussed below.
Intake turbocharging increases the density of air entering the cylinders by boosting intake pressure, thereby increasing the excess air coefficient. This enables more complete combustion and restores the indicated mean effective pressure, allowing the diesel engine to recover its rated low-altitude power output.
However, turbocharging raises intake air temperature, which can reduce air density recovery and significantly increase thermal load and exhaust temperature, adversely affecting reliability. Therefore, an intercooling system should be used to cool the compressed intake air, reduce thermal stress, and further improve power recovery.
Once power is restored through turbocharging, the original cooling system is often insufficient. The radiator and fan parameters must be reselected and optimized to ensure proper thermal balance of the diesel engine.
Due to reduced air density and a lower coolant boiling point at high altitudes, conventional cooling systems cannot meet heat dissipation requirements. A pressurized closed-loop cooling system should be adopted to raise the boiling point of the coolant and enhance cooling performance.
At the same time, radiator capacity and fan specifications should be optimized according to actual operating conditions to ensure reliable cooling under plateau environments.
As temperature decreases, battery capacity declines significantly. To ensure reliable engine starting, low-temperature, high-performance batteries should be used as the starting power source. This ensures sufficient cranking current is available even in cold, high-altitude conditions.
In remote high-altitude areas where no external power supply is available and starting conditions are harsh, fuel heaters can be employed. By using diesel combustion to forcibly circulate heat through the engine block, reliable starting can be achieved even at temperatures as low as –40 °C. This significantly improves starting performance in plateau regions.
Electronic fuel injection (EFI) systems are equipped with oxygen sensors that adjust air intake and fuel delivery based on actual operating conditions, effectively compensating for oxygen deficiency at high altitudes.
As a result, altitude has a smaller impact on the power output of electronically fuel-injected diesel engines compared with mechanically governed engines. EFI systems can therefore improve adaptability and performance under high-altitude conditions.
During design and equipment selection, circuit breakers with high breaking capacity should be used, and electrical clearances between live parts should be increased. Generator windings should incorporate anti-corona measures.
For high-voltage generator sets above 6.3 kV, special attention must be paid to component selection and clearance control. These measures effectively enhance electrical performance and reliability while reducing the risk of electrical failures in high-altitude environments.
Considering the tendency for increased ignition delay under high-altitude conditions, it is generally recommended to moderately advance the fuel injection timing for naturally aspirated diesel engines. This improves combustion quality, enhances power output, and improves fuel economy.
Different diesel engines have different rated power outputs and therefore exhibit varying levels of adaptability to high-altitude operation. Users should carefully consider the high-altitude capability of engines and strictly avoid overload operation.
Experimental studies in recent years have shown that exhaust gas turbocharging is an effective method for power compensation in high-altitude applications. Turbocharging not only compensates for power loss but also improves exhaust smoke characteristics, restores dynamic performance, and reduces specific fuel consumption.
To better illustrate the impact of high-altitude environments and the effectiveness of mitigation measures, consider a practical example. A military base located in a plateau region originally used conventional diesel generator sets. As altitude increased, the generators experienced significant power loss, higher fuel consumption, and increased thermal load, severely affecting normal power supply.
After analysis, intake turbocharging technology was applied, the cooling system was optimized, and low-temperature high-performance batteries and fuel heaters were installed. Following these modifications, the generator sets regained their original rated output power, fuel consumption was reduced, thermal load was effectively controlled, and starting performance improved significantly.
This case clearly demonstrates the effectiveness and feasibility of the proposed mitigation strategies.
High-altitude environments impose multiple adverse effects on diesel generator sets, including power derating, increased fuel consumption, higher thermal load, degraded electrical performance, reduced cooling efficiency, and starting difficulties. However, by implementing a combination of measures, such as intake turbocharging, cooling system optimization, low-temperature batteries, fuel heaters, electronic fuel injection, optimized electrical component selection, proper fuel injection timing adjustment, and appropriate engine selection, these challenges can be effectively addressed.
Strengthening fundamental research on the adaptability of electromechanical equipment to high-altitude environments is essential for the development of plateau-specific power generation equipment. Such efforts not only reduce economic losses caused by high-altitude conditions but also enhance social benefits and improve the effectiveness of power guarantee for military and civilian applications in plateau regions.
