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Some effective measures to prevent the fuel system of diesel generator sets from being damaged by cavitation

July 22, 2022
Cavitation, also known as bubble corrosion or cavitation, is a local corrosion damage, diesel generator fuel system cavitation usually occurs in the high-pressure fuel pump, high-pressure fuel pipe and injectors, etc., if not dealt with in a timely manner, will directly affect the normal work of the diesel generator set.
The harm of cavitation
1. cavitation can cause high-pressure oil pump pump body penetration, resulting in poor sliding performance of the plunger coupling or cassette.
2. Cave corrosion causes high-pressure oil pipe aperture change or oil pipe fracture, further affecting the oil volume change.
3. Cavitation also causes poor atomization of the injector needle valve coupling, dripping oil or even no atomization at all, thus worsening the combustion state of diesel generators, increasing fuel consumption and seriously affecting the economy, reliability and durability of diesel generators.
Causes of cavitation
Diesel generator fuel system in the high-pressure oil pump plunger, outlet valve, injector needle valve and high-pressure fuel pipe may have cavitation, which is the combined result of physical and chemical effects, usually the fuel system cavitation are the following two kinds: 1.
1. Fluctuation cavitation: mainly occurs in the high-pressure fuel pipe. High pressure fuel flow in the fuel system and the propagation of pressure waves, especially at the end of the injection will make some parts of the pressure changes greatly, and even produce negative pressure waves, resulting in bubbles, high pressure and bubble collapse cavitation, known as fluctuation cavitation. Diesel engine low load operation fluctuations cavitation corrosion is more serious.
2. Flow cavitation: mainly occurs in the high-pressure fuel pump plunger near the spiral groove and injector needle valve cross-section changes. In the fuel system, the high pressure fuel flow through the channel cross-sectional changes in the strong throttling, pressure drop and the formation of bubbles, the subsequent increase in pressure and bubble collapse and cavitation, known as flow cavitation. The throttling effect increases when the diesel engine is running under high load, making cavitation more serious.
Effective measures to prevent cavitation damage
Prevention of fuel system cavitation can be through structural design changes, materials, heat treatment, manufacturing accuracy and use of the unit's maintenance and maintenance of the five aspects to consider measures, as follows.
1. Improvement of structural design, optimization design of fuel supply cam surface, reasonable design of fuel supply cam surface to adapt to the changing law of instantaneous fuel supply volume and oil pressure.
2. Adopt process plug, currently in some high-pressure oil pump pump body using process plug to resist cavitation and prolong the service life of high-pressure oil pump; use high-strength alloy material in the design of the product using high-strength alloy material to prevent cavitation on the fittings.
3. Adopt buffer type oil discharge valve, buffer type oil discharge valve is improved on the basis of the original lower equal capacity unloading structure. Before the valve is seated, the fuel inside the valve is sealed to some extent after the unloading flange enters the guide hole, and the fuel can only be discharged through the 6 mm and 14 mm clearance. The damping effect of the fuel slows down the seating speed of the discharge valve and reduces the return speed in the system at the end of the fuel supply. It also receives the effect of reducing the amplitude of pressure wave oscillation and mitigating secondary injection. Injector needle valve coupling cavity corrosion is reduced.
4. The use of pressure unloading type oil valve. It is used to seem to control the system pressure saved by the pump body between the two injections to prevent the backflow of fuel from the injector after injection.
The outlet valve is equipped with a down-flow valve and a back-flow valve each. It ensures that the residual pressure in the high pressure fuel line remains constant under all working conditions of the diesel generator. It is not affected by the load and speed of the diesel generator, which can improve the performance of the diesel generator under partial load and improve the service life of the injector; the careful maintenance of the use department and careful maintenance and strict overhaul are also essential conditions to ensure the reduction of cavitation.
5. injector coupling material selection, with the diesel generator power level and strengthening the degree of improvement, the injector coupling material selection has become an important issue. Because the real valve body material selection and its working temperature in the diesel generator has a close relationship.