The reasons of fuel atomization poor in 250kva diesel generator

When the fuel injector of 250kva generator set works, it must have a good atomization function, so as to ensure the fuel combustion of the genset is good, the smoke color of the unit is normal, and the power of the generator is normal.

But maybe we meet fuel atomization of the injector is poor, why? Today Starlight tells you the reasons.

The process of dispersing fuel into fine particles is called fuel spray (or atomization). That can greatly increase the surface area of fuel evaporation and the chance of fuel and oxygen contact to achieve rapid mixing. There are many factors that affect the characteristics of the fuel spray, mainly is structure and size of fuel injector, injection pressure, back pressure of compressed air in cylinder, fuel pump cam contour and speed, fuel viscosity etc.

1.Back pressure of compressed air in cylinder

When Back pressure of compressed air in cylinder of 250kva generator set increasing, density of compressed air will increase, which can increase air resistance acting on fuel spray. Therefore, fuel atomization can be improved, spray cone angle is increased, and range is reduced. In the non supercharged diesel generator, the reverse pressure of the compressed air in the cylinder does not change much, so it has no significant effect on the characteristics of the oil spray.

2.Fuel pump cam contour and speed

When the cam contour is steep or the camshaft speed is high, the speed of fuel supply in plunger of injection pump will increase. Because injector orifice reduces expenditure, fuel can not folw out directly. Which causes fuel pressure in fuel pipe increased and the speed at which fuel flows out of the orifice increased. Therefore, fuel spray and spray cone angle increases.

3.Fuel viscosity

When the viscosity of the fuel increases, the fuel particles are not easy to disperse into fine drops, resulting in poor atomization. Therefore, for high-speed diesel generators, we generally select light diesel oil with low viscosity as fuel oil.

4.Structure and size of fuel injector

Different structure of injector, the internal perturbation of oil spray will be different, which produce different types of oil spray. The fuel bunches should be closely matched with the combustion system. Different combustion modes require different oil spray, so the fuel injectors with different structures are used.

Under the conditions of unchanged injection pressure, back pressure of compressed air in cylinder and the total size of injector hole, to increase the quantity of injector hole, as the diameter of each orifice decreases, fuel will be throttled more when it flows out of the orifice. So the disturbance increases in the orifice. Therefore, the quality of atomization is improved. If diameter of each orifice increases, the core of the oil spray is dense and the range is increased.

5.Injection pressure

The bigger injection pressure, the bigger initial speed of fuel outflow. Degree of fuel disturbance in the injector hole is bigger, and resistance of compressed air after fuel flow out injector hole, so that the fineness and uniformity of atomization are improved, that is a good quality  atomization. When injection pressure increases, range of oil spray will increase.

How to maintain injector of 250kva diesel generator set?

In order to make the fuel injected into the cylinder by the injector burn completely in time, the oil supply time of the oil pump must be checked regularly. If the fuel supply time is too early, the unit will have difficulties in starting and knocking fault. If fuel supply time is too late, it will lead to black smoke from exhaust, high temperature and increased fuel consumption. The fitting accuracy of the injector needle valve is very high, and the orifice diameter is very small, so we must select specific diesel oil by seasonal variation. Otherwise, the fuel injector can not operate normally.

Do not collide with other hard objects or drop them to the ground when cleaning the needle valve parts of the fuel injector to avoid damaged. When replace the needle valve parts of the fuel injector, should immerse the new coupling in 80℃ hot diesel oil for about 10s. After antirust oil is fully dissolved, spasm the needle valve back and forth in the valve body in clean diesel oil, and thoroughly clean it. In this way, the failure of sticking needle valve due to the dissolving of antirust oil can be avoided.

Above information is about the reasons of fuel atomization poor in 250kva diesel generator set, hope it is helpful to you. When you meet the problem, you can check and remove faults by above reasons.

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Created on Dec 18th 2019 19:49. Viewed 327 times.

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