Layouts of Air-Cooled Cooling Systems in Diesel Generators

The air-cooled cooling system of diesel generators uses air as the cooling medium, also known as air cooling. The basic principle of this system is to use high-speed air generated by a fan to directly carry away the heat from the high-temperature components of the diesel generator engine, ensuring the engine operates at its optimal temperature. To enhance cooling performance, cooling fins are designed on the cylinder and cylinder head outer surfaces to increase the heat dissipation area. Additionally, air ducts and deflector plates are used to guide the cooling air efficiently, ensuring uniform and effective cooling.

Air-cooled System vs. Water-cooled Systems

The core components of the air-cooled system include cooling fins, fans, air ducts, and deflector plates. Compared to water-cooled systems, air cooling has several advantages, such as fewer components, simpler structure, lighter weight, easier operation and maintenance, and strong adaptability to environmental changes (such as water shortages, extreme cold, or heat). However, air cooling also has some limitations, such as higher noise levels, higher thermal load, greater fan power consumption, and lower air intake efficiency.

Structure and Working Principle of the Air-Cooled System

The air-cooled system primarily uses a fan to direct air to the critical components of the diesel engine, removing heat. The design and configuration of the system directly affect the cooling performance. The main components and working principles of the air-cooled system are as follows.

1. Cooling Fins

The purpose of cooling fins is to increase the surface area in contact with air, thereby improving heat exchange efficiency. Cooling fins are typically arranged on the outer surface of the cylinder and cylinder head to help dissipate heat.

2. Fan

The fan is the core component of the air-cooling system, responsible for drawing air into the system and accelerating airflow. The type and arrangement of the fan depend on the specific requirements of the diesel engine.

3. Air Duct and Deflector Plates

The design of the air duct and deflector plates ensures that cooling air is evenly distributed to all cylinders and cylinder heads, preventing uneven cooling or waste of cooling air.

Layout of the Air-Cooled System

The layout of the air-cooled system typically varies depending on the cylinder arrangement, fan type, and installation position of the diesel engine. Here are some common layouts for the air-cooled system.

1. Centrifugal Fan Layout for Single-Cylinder Diesel Engines

The centrifugal fan is typically integrated with the flywheel and installed at the rear end of the diesel engine, driven directly by the crankshaft. Air is drawn in axially through the intake and, after passing through the fan's scroll, is guided by the air duct to cool the cylinders and cylinder heads. This layout is simple, compact, and reduces the need for a separate fan drive mechanism, making it ideal for small air-cooled diesel engines.

2. Axial Flow Fan Layout

The axial flow fan is driven by the crankshaft through a V-belt and is typically located at the front of the diesel engine. Air flows axially, is drawn into the fan, and is directed into the air chamber. The air is then distributed to each cylinder through the air duct, with deflector plates helping to ensure even cooling. This layout is suitable for medium to small-sized diesel engines.

3. Double-Row Cylinder Air-Cooled Layout

In this design, the axial flow fan is usually located between the two rows of cylinders, driven by the crankshaft via a V-belt. The cooled air is then expelled from the lower side of each row of cylinders, ensuring uniform cooling for both rows.

Adjusting Cooling Intensity in the Air-Cooled System

The cooling intensity of the air-cooled system mainly depends on the air velocity through the cooling fins. To accommodate different operating conditions and environmental requirements, the cooling intensity often needs to be adjusted. Common adjustment methods include:

1. Fan Speed Adjustment

Increasing the fan speed increases airflow, thereby enhancing the cooling effect. Conversely, reducing the fan speed weakens the cooling effect. At low thermal loads, reducing fan speed not only decreases cooling intensity but also lowers noise and saves fan power. This is a commonly used and effective adjustment method. Fan speed is often adjusted using a hydraulic coupling, which regulates the oil quantity through a temperature sensor on the exhaust pipe or air vent.

2. Controlling Cooling Airflow

By setting temperature sensors to control the opening of adjustable louvers or throttling valves, the intake airflow and airspeed can be varied. This method is relatively simple, but since fan speed remains constant, it does not reduce fan power consumption and may increase flow resistance, affecting the overall efficiency of the diesel engine.

Conclusion

The air-cooled cooling system, with its simplicity, light weight, and adaptability, is widely used in small diesel generators and environments with demanding conditions. Although it has drawbacks such as higher noise and thermal load, the cooling efficiency can be effectively improved through proper design and adjustment to meet the operating requirements of diesel engines. Understanding the working principle and adjustment methods of the air-cooled system can help better maintain and optimize the performance of diesel generators in practical applications.