Fault analysis of fuel injection nozzle of the hot

2022-08-18
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The function of diesel engine injector is to inject diesel oil into the combustion chamber with fine atomized particles to form a good combustible mixture with air. The fuel injector is installed on the cylinder head. The fuel injector goes deep into the combustion chamber of the diesel engine and works under the environment of high temperature, high pressure and gas corrosion for a long time. The internal moving parts are impacted by the high-speed flowing fuel and repeatedly washed by the micro mechanical impurities in the fuel. It is very easy to wear and be corroded. Graphene can be mixed with glass or carbon for corrosion. It is one of the most faulty components in the diesel engine fuel system. Today, I will briefly introduce the common faults and precautions of the fuel injector ~

causes of diesel engine fuel injector faults

first, poor atomization of the fuel injector

when the injection pressure is too low, the nozzle hole is worn and there is carbon deposition, and the spring end face is worn or the elasticity decreases, the fuel injector will open in advance, delay to close, and form the phenomenon of poor atomization of fuel injection. If it becomes a powerful boom cylinder diesel engine for the successful transformation of enterprises, it will not work; If it is a multi cylinder diesel engine, the power decreases, the exhaust emits black smoke, and the machine operation sound is abnormal. In addition, because the diesel droplets with too large particle size can not be fully burned, they flow into the oil pan along the cylinder wall, which increases the oil level of the engine oil, reduces the viscosity, deteriorates the lubrication, and may also cause the accident of burning tiles and pulling cylinders

solution: the fuel injector should be disassembled, cleaned, overhauled and re debugged

second, the fuel return pipe of the fuel injector is damaged

when the needle valve coupling is seriously worn or the needle valve body is not closely matched with the fuel injector shell, the fuel return volume of the fuel injector will increase significantly, and some can reach 0.1 ~ 0.3 kg/h. If the oil return pipe is damaged or missing, the oil return will be lost in vain, resulting in waste. Therefore, the oil return pipe must be intact and sealed so that the oil return can flow smoothly into the oil tank. If the oil return pipe is connected to the diesel filter, a check valve shall be set at its terminal to prevent the diesel in the filter from flowing back into the injector

III. needle valve orifice expansion

due to the continuous spray erosion of high-pressure oil flow, the needle valve orifice will gradually grind larger, resulting in the decrease of injection pressure, the shortening of injection distance, poor diesel atomization, and the increase of carbon deposition in the cylinder

solution: the hole diameter of single hole axial needle injector is generally greater than 1mm. A steel ball with a diameter of 4 ~ 5 mm can be placed at the hole end and gently knocked with a hammer to cause plastic deformation in the spray hole and reduce the hole diameter. Due to the large number of holes and small hole diameter, the porous direct injection injector can only be gently knocked on the hole end with the punching sample ground by high-speed steel. If it is still unqualified after debugging, the needle valve coupling should be replaced

IV. the needle valve will bite

the water or acid in the diesel oil will make the needle valve rust and get stuck. After the sealing cone of the needle valve is damaged, the combustible gas in the cylinder will also escape into the mating surface to form carbon deposition, which will make the needle valve bite, and the injector will lose its fuel injection function, causing the cylinder to stop working

solution: put the needle valve into the waste oil and heat it until it boils and smokes, then take it out, clamp the tail of the needle valve with a pliers padded with a soft cloth and move it slowly, take it out and dip it with clean engine oil, and let the needle valve move and grind repeatedly in the valve body until the needle valve can slowly retreat from the valve body when the needle valve is inverted, and evaluate whether this order can be received and what price it should be offered. If the test of installing the fuel injector fails, replace the needle valve coupling

v. the end face of the needle valve body is worn

the end face of the needle valve body is impacted by the frequent reciprocating motion of the needle valve, and over time, pits will gradually form, thereby increasing the lift of the needle valve and affecting the normal operation of the injector

solution: clamp the needle valve body on the grinder to grind this end face, and then grind it on the glass plate with fine grinding paste

VI. gas leakage and oil channeling in the joint hole between the fuel injector and the cylinder head

when the fuel injector is installed in the cylinder head, the carbon deposit in the installation hole should be carefully removed, and the copper gasket must be flat, and it should not be replaced by asbestos board or other materials, so as to prevent poor heat dissipation or failure to play the role of lifelong technical service seal. If the copper washer is self-made, it must be processed with red copper according to the specified thickness to ensure that the distance of the fuel injector extending out of the cylinder head plane meets the technical requirements. In addition, the concave shape of the pressure plate of the fuel injector should be installed downward. When tightening, avoid unilateral bias, and tighten it evenly according to the specified torque, otherwise the head of the fuel injector will leak gas and oil due to deformation and deflection

VII. Wear of needle valve and needle valve hole guide surface

the frequent reciprocating motion of needle valve in the needle valve hole, coupled with the invasion of impurities and dirt in diesel, will gradually wear the needle valve hole guide surface, resulting in increased clearance or strain marks, resulting in increased internal leakage of fuel injector, low pressure drop, reduced fuel injection volume, and delayed fuel injection time, resulting in difficult starting of diesel engine

solution: when the fuel injection time is delayed too much, the locomotive can't even run. At this time, the needle valve coupling should be replaced

VIII. Oil dripping from the injector

when the injector is working, the sealing cone of the needle valve body will be subjected to frequent strong impact from the needle valve. In addition, the high-pressure oil flow will continuously spray out from there, and the cone will gradually appear nicks or spots, thus losing the seal, resulting in oil dripping from the injector. When the diesel engine temperature is low, the exhaust pipe emits white smoke, and when the engine temperature rises, it turns into black smoke, and the exhaust pipe will emit irregular shooting sound. At this time, if the oil supply to the cylinder is stopped, the smoke exhaust and gunfire sound will disappear

solution: disassemble the fuel injector, dip a little chromium oxide fine grinding paste on the head of the needle valve (pay attention not to dip it in the needle valve hole) to grind the conical surface, then clean it with diesel oil and put it into the fuel injector for test. If it is still unqualified, replace the needle valve coupling

precautions for reducing fuel injector failure

I. inspection of fuel injector

first, check the starting injection pressure and sealing of fuel injector. Secondly, check the atomization quality of the fuel injector, carefully observe the shape, number, fineness and distribution of the spray column, and pay attention to whether there is fuel leakage at the spray hole before the valve opening pressure and after injection. Good atomization quality means that the spray column meets the requirements, and there is no oil droplet gushing or leakage, and there is a crisp "squeak" sound during the whole spraying process

II. Precautions during assembly

before installing the fuel injector into the cylinder, first check whether the sealing ring on the fuel injector is intact, and then check the cleanliness and tightness of the sealing surface between the fuel injector and the cylinder head. If necessary, clean and grind it to prevent fuel gas from leaking out and burning the fuel injector. At the same time, pay attention that the fastening nut of the fuel injector on the cylinder head should not be over tightened, and it should be strictly in accordance with the provisions of the operation manual

III. try to keep the diesel engine in a good working condition

under the condition of meeting the use requirements, try to keep the diesel engine running under a higher load, and the combustion quality is the best when the load is more than 80%

IV. reasonable selection of fuel

the most appropriate fuel should be selected, and the fuel with low sulfur content should be selected as far as possible to ensure the cleanliness of the fuel and reduce the content of impurities and water

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