The exhaust temperature of a screw air compressor is limited by the upper and lower temperatures. This article will take you through the key component of temperature control in screw air compressors - the temperature control valve, and answer questions about the differences between split flow and mixed flow.
1. The sampling point for the exhaust temperature of the screw air compressor is located near the outlet of the compressor, which is the temperature of the oil and gas mixture at the outlet of the main engine. The most important way to control the outlet temperature of the compressor is to control the oil injection temperature of the compressor, and the temperature control valve is responsible for it.
The exhaust temperature of screw air compressors has special requirements, neither too high nor too low. That is to say, there are two temperature restrictions.
The exhaust temperature of screw air compressors is too high, which can cause tripping, carbon deposition, reduced efficiency, and even damage to parts. The upper limit of general exhaust temperature control is 110 ℃. However, the lower temperature limit is affected by environmental temperature, humidity, and pressure, which can prevent changes in condensed water during operation, leading to lubricant emulsification, damaging the cooling and lubrication effects of the unit, and reducing its performance.
2. Screw air compressor lubrication and cooling system. Screw air compressor belongs to volumetric compressor, and its cooling and temperature control are achieved by injecting a large amount of lubricating oil into the cylinder block to remove heat. It is an internal cooling method with more obvious cooling effect. Compared with insulation processes and indirect cooling methods, the required cycle indicator power is lower, reducing power consumption and improving efficiency.
Comparing the cycle indication power of different cooling methods, it can be seen that the cycle indication power of the screw air compressor is 80%, and the indirect cooling is 97%. Therefore, it can be seen that the power of oil injection cooling is much lower than that of general indirect cooling.
The continuous operation of screw machines generates a large amount of heat, and lubricating oil is often designed as a closed cycle system as a cooling medium.
It is a common lubricating oil system for screw machines, equipped with a cooler, temperature control valve, and oil filter. The lubricating oil with a certain pressure in the oil separator is cooled by the oil cooler, mixed with the uncooled lubricating oil, and then sprayed into the screw machine through the oil filter to control the temperature.
The lubricating oil system of the screw machine mixes and filters lubricating oil, which is directly sprayed into the screw machine. The system pipeline configuration is simpler. Under the pressure of the oil and gas separator, the lubricating oil demand is adjusted according to the load change through a temperature control valve. After filtration, it is directly sprayed into the compression chamber of the screw machine to cool the heat generated by compression.
3. The principle and structure of the temperature control valve of the air compressor should ensure the accuracy and controllability of the exhaust temperature of the screw air compressor. The temperature control valve is a key component for temperature control in the lubricating oil cooling system. This valve is a type of valve that uses special temperature paraffin as the valve core to control fluid temperature. It utilizes the linear expansion characteristics of paraffin volume during solid-liquid phase transition to convert temperature change signals into valve core displacement changes to control the lubricating oil of the oil cooler.
This is the commonly used temperature control valve structure in screw machines at present. The valve body design has 4 valve ports, with the inlet receiving lubricating oil from the oil and gas separator, and 2 intermediate interfaces R1 and R2. Interface R1 connects to the inlet of the oil cooler, and interface R2 connects to the outlet of the oil cooler. At this point, the hot oil is transported to the oil cooler, and the cooled oil flows back to the valve body. The lubricating oil is then transported to the screw machine through a filter.
Thermal power components expand or contract within a predetermined temperature range.
When the oil temperature in the oil and gas tank is high and reaches the control point, the thermal power element pushes the valve core to move downward against the force of the spring. The higher the temperature, the greater the displacement of the valve core, and the larger the valve opening leading to the oil cooler. When the oil temperature reaches the upper limit of the thermal power element temperature range, all openings are opened and the oil passes through the oil cooler.
When the oil temperature drops, the thermodynamic components are opposite to the above. When the oil temperature drops below the temperature sensing range of the thermal power component, the valve core returns to its initial position, and all valve openings leading to the oil cooler are closed. The oil in the oil and gas tank flows directly to the screw machine without the need for an oil cooler.
For screw air compressors, a lubricating oil temperature between 70-85 ℃ is preferred. Lubricating oil. At temperatures between 70-85 ℃, the volatility is relatively low. The gap between screw rotors is generally 5-12um, with larger machines being larger and smaller ones being smaller. The bite expansion temperature is generally between 130-140 ℃, and the temperature of the compressor needs to be controlled, with most upper limits set at 110 ℃. Meanwhile, supporting bearings are generally not allowed to operate at temperatures above 100 ℃ for extended periods of time.
The temperature control valve adopts a diversion control mode (which is quite common and is usually used for small and medium-sized screw machines to control the temperature of the valve core. As far as the author knows, there are 71 ℃ and 76 ℃)
The temperature control valve adopts mixed flow control mode (usually used for large screw machines, temperature control valve core temperature, as far as the author knows, there are 54 ℃ and 43 ℃)
Additionally:
① In summer and very humid areas, special attention must be paid to the exhaust temperature of the screw compressor unit, preferably above 95 ℃;
② Suggest using synthetic oil in high temperature and humid areas in the south;
③ Raise the exhaust temperature of the machine to between 95 ℃ and 100 ℃ from May to September;
④ If the discharge temperature is low, the measures are as follows: by blocking the ventilation area of the aluminum cooler, reducing the cooling water volume or water pressure, an air-cooled machine can be achieved.
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