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The valve needs to be operated frequently, so it should be installed in a location where it is easily accessible. When installing, pay attention to the direction of the medium and the direction of the arrow marked on the valve body.
The sources of deposits in the choke valve are complex, but can be grouped into the following categories:
(1) Mechanical impurities in the oil or colloid, asphalt, carbon slag and other dirt precipitated by oxidation accumulate in the throttling gap.
(2) Due to the aging of the oil or the generation of charged polarized molecules after being squeezed, and there is a potential difference on the metal surface of the choke valve gap, the polarized molecules are adsorbed to the surface of the gap to form a firm boundary adsorption layer. The thickness is generally 5 to 8 microns, which affects the size of the throttling gap.
When the above accumulation and adsorbate grow to a certain thickness, they will be washed away by the liquid flow, and then reattached to the valve port. This cycle is repeated, forming a pulsation of the flow.
(3) When the pressure difference of the valve port is large, due to the high temperature of the choke valve port, the degree of liquid extrusion is enhanced, and the metal surface is more susceptible to friction to form a potential difference, so it is easy to cause blockage when the pressure difference is large.
(4) The source of PCV exhaust gas: The combustible gas mixture in the combustion chamber enters the crankcase through the piston gap and is mixed with the oil vapor.
To avoid dilution and contamination of the oil, the gas mixture is drawn into the intake port by a positive crankcase ventilation system (PCV) for secondary combustion. After this part of the exhaust gas enters the intake port, it will condense to form a liquid state due to the decrease in temperature, and the "unstable components" in it will be oxidized and condensed at high temperature, forming grease on the surface of the choke valve and adhering to it.
(5) In-depth lubricating oil for turbocharged compressors: For turbocharged engines, the exhaust gas drive method is generally adopted at present, that is, the high-pressure exhaust gas generated by the exhaust port is used to drive the turbine, and the compressor blades in the intake port are driven by the coaxial shaft, forming a supercharged air flow in the intake port.
However, under long-term and harsh working conditions, the coaxial bearing is prone to the penetration and volatilization of the lubricating oil. Besides, the inflation efficiency increases exponentially, which is more likely to form heavy oil pollution and aggravate the adhesion of the deposits in choke valve.
(6) Fuel vapor discharged from the carbon canister: In the fuel vapor adsorbed by the engine carbon canister, it is easy for cyclopentadiene to form choke valve deposits, which can be oxidized and condensed to form a colloidal oil scale under continuous high temperature.
When the choke valve (ie butterfly valve) is blocked by sediment, the opening value of the choke valve is disordered, the engine cannot control its opening stably and accurately. If the opening value is too low, it will cause difficulty in starting, unstable idling or abnormal flameout; when the engine accelerates and decelerates, the choke valve cannot respond in time, which will cause acceleration delay or sudden acceleration.
Most of the opening and closing parts of the choke valve are of conical streamline type, which can adjust the flow and pressure by changing the cross-sectional area of the passage. The choke valve is used to reduce the medium pressure in the case of extremely high pressure.
