Working Principle of Cooling Intensity Regulating Device
Working principle of cooling intensity regulating device in cooling system of diesel generator set
The cooling capacity of the cooling system is designed according to the common working conditions of the engine and the condition of high temperature to ensure reliable cooling. When the operating conditions, such as speed, load, temperature are changed, the heat transfer capacity of the radiator must be changed, so that the heat that needs to be removed from the cooling system is in harmony with the cooling system’s heat dissipation capacity. The cooling intensity is adjusted by changing the circulating flow rate or cooling air flow rate of cooling water flowing through the core of the radiator to ensure that the engine works at the optimum temperature.
1. Changing the circulating flow rate of cooling water flowing through the core of the radiator. Reducing the amount of water flowing through the alarm will reduce heat dissipation and increase the temperature of the entire cooling system. The amount of water flowing through the radiator is regulated by a thermostat installed in the water passage near the outlet of the cylinder head. There are two types of thermostats: expansion cylinder type and wax type.
Construction and working condition of double valve expansion cylinder thermostat. The elastic folding closed cylinder, made of brass, is a temperature-sensing part, and contains volatile liquid with low boiling point, the steam pressure of which varies with temperature. When the temperature is high, the steam pressure is high and the elastic expansion cylinder is much longer. When the cylinder is elongated, the bypass valve door and main valve welded on the top of the cylinder also move up, so that the bypass hole is gradually opened and the open degree pf main valve reaches the maximum when the bypass hole is completely closed. When the main valve is closed, all bypass holes are opened.
When the cooling water temperature is below 70 ℃, the main valve of the thermostat is closed and the bypass hole is opened. Cooling water can not flow into the radiator, only through the thermostat bypass hole into the backwater return pump, and then the pump pressure into the water jacket. The circulation of this cooling water between the pump and the water jacket is called small circulation. Since the cooling water does not flow through the radiator, it prevents the diesel engine from being undercooled and can make the cold diesel engine be heated quickly.
When the water temperature exceeds 70 ℃, the steam pressure in the elastic expansion cylinder makes the tube elongate, the main valve opens gradually, and the side hoe is gradually closed. One part of the cooling water is injected into the radiator through the main valve, the other part of the cooling water for small circulation. When the water temperature exceeds 80℃, the side holes are closed and the cooling water flows through the radiator, then enters the water pump, and compacts the water pump into the water jacket to cool the high temperature parts. Cooling water flow through the radiator into the water pump cycle called large circulation. The heat of the high-temperature parts is taken away by cooling water and dissipated through the radiator so that the diesel engine will not overheat.
The valve of expansion cylinder thermostat is opened by the steam pressure formed by volatile liquid in the cylinder, it is sensitive to the working pressure in the cooling system, has poor working reliability, short service life and complicated manufacturing process. It is now being replaced by wax thermostats that are insensitive to the pressure of the cooling system, reliable in operation and long in life.
Working principle diagram of waxy double valve thermostat. The upper bracket is riveted with the valve seat and the lower support is riveted into one body. The back-push rod is fixed at the center of the bracket and inserted in the center of the rubber sleeve. The cavity formed between the rubber sleeve and the thermostat housing contains paraffin wax. In order to prevent wax from flowing out, the upper end of the thermostat shell is curled inwards, and the rubber sleeve is pressed on the shoulder surface of the shell through the upper cover and seal gasket.
When the temperature is normal, the paraffin wax is solid. When the water temperature is below 76 ℃, the spring compacts the main valve against the seat and the main valve is completely closed. At the same time, drive the valve upward away from the valve seat, so that the valve open, cooling water for small circulation. When the water temperature rises, the paraffin gradually becomes liquid, and then volume expands, forcing the rubber sleeve to shrink, which produces the lifting force on the head of the back push rod cone, and the fixed back push rod produces a downward thrust on the rubber sleeve and the temperature sensor shell. When the water temperature of the diesel generator reaches 76 ℃, the lower thrust of the reverse push rod to the thermostat housing overcomes the spring tension to open the main valve. When the water temperature is over 86 ℃, the main valve is completely open, and the auxiliary valve is completely closed.
2. Change the flow rate of cooling air flowing through the core of the radiator
Blinds or windscreens can be installed in front of the radiator to partially or completely shield the radiator core. Blinds can be operated by the operator with a handle, or by the thermostat to automatically control the opening of the shutters.
