Diesel generator engine running at low speed instability is often shown as: idle speed running instability and the so-called “car”.
Idle instability means that the engine is fast and slow at idle speed, but the regularity is not strong, and there is chattering. Machinery in emergency deceleration and load when easy to stall, this phenomenon is caused by governor failure. Taking RSV governor as an example, the main causes of engine idling instability are as follows:
(1) The wear of the flying block due to poor lubrication of the governor or for a long period of use, the two small rollers in contact with the flying block and the speed regulating sleeve will be seriously worn. At idle speed, the opening degree of the flying block is the smallest. The speed regulating sleeve extends too far into the inside of the flying block due to the wear of the small roller, resulting in irregular direct collision with the body of the flying block, resulting in the idle speed instability. At this time, if you touch the refueling manipulator lightly, there will be a slight impact feeling.
(2) Idle stability spring adjustment or poor performance at idle, because the centrifugal force of the flying block is small, idle control is small, once the engine slows down suddenly, the adjustment of the oil supply rod moves too fast, may exceed the idle position, causing the engine to stall. In order to prevent this situation, there is an idle stability spring which can quickly push the oil supply tooth rod back to the idle position at the place directly opposite the oil supply tooth rod behind the governor cover. If the spring is too soft or skewed, it will weaken or fail to stabilize the speed, so that the idle operation is unstable. When the engine is running, the load increases and the speed decreases. If the idle stable spring or start spring becomes soft, the oil supply tooth rod can not quickly move to the direction of oil and make the speed increase, serious will cause the engine to stall.
(3) The oil supply in the low-pressure oil circuit is not smooth or contains water or air, which will make the oil supply quantity large or small, especially in the low-speed area, which will lead to the instability of engine speed
(4) The wear of the conical bearing of the camshaft supported by the injection pump is too large, which will cause the camshaft to have irregular movement in the axial direction, so that the engine speed is unstable.
(5) the fuel injection pump is not uniform, the oil supply is not timely or the injector is bad string 6 engine rotation at low speed, the rotational inertia of the crankshaft is not large, when the oil supply is not uniform, the oil supply is not timely or the injector is bad, it will have a greater impact on the stability of the speed, but this instability is slightly regular, and the cycle is short.
(6) The engine cylinder pressure is insufficient when the cylinder compression force drops, because the degree of pressure drop of each cylinder is not necessarily the same, so even if the fuel injection pump is balanced, but the combustion force situation may be different, which can cause the speed instability at low speed.
The so-called “running car” refers to the engine in the range of low or medium speed shows a long and regular cycle of fast and slow a fault phenomenon. This is the result of the governor’s reaction lagging too far behind the actual speed. The main reasons for this phenomenon are as follows:
(1) The pin hole of the internal lever connection of the governor is loose. The pin hole of the internal lever connection of the governor is loose due to wear and tear, which causes excessive lag in the movement of the two-way regulating valve that increases or decreases the oil supply. Speed regulating reaction needs to lag behind the actual speed change, but the lag should not be too large, otherwise it will produce a large adjustment amplitude.
(2) The oil supply tooth rod is not flexible. The oil supply tooth rod of the fuel injection pump must be kept very flexible to ensure the sensitivity of the speed regulation reaction. A sensitive spring balance is used to test the pull resistance of the toothed rod. Among them, the 2, 4, 6, 8 cylinder of the injection pump, the resistance should be 0.6, 0.9, 1.3, 1.5N. Due to rust, plunger matching parts and plunger spring break after deformation, ring gear and gear lever meshing of crush injury, serious wear, tooth rod end shaft sleeve fork type oil quantity adjusting mechanism of fork fastening Angle is not correct, domestic number I, ii and iii series pump speed governor of thrust plate and block of installation or cooperate with bad reasons, such as flexibility will affect the oil gear lever.
(3) Improper adjustment of the stable idle speed is similar to improper adjustment of the stable spring when the idle speed is unstable. Improper adjustment of the stable idle speed and the insufficient flexibility of the oil supply tooth rod work together, which will also lead to the engine “cruising”.
The cause of instability at high speed engine instability at high speed is usually characterized by instability at high speed without load. Diesel engines generally work in the medium speed range with the maximum output torque, because this speed range is easy to control and more fuel efficient. But in no load also often enter the speed range of speed governor high speed control. At this time, the reasons for unstable operation mainly include:
(1) Adjustment of speed improper adjustment of speed is an important index to evaluate the performance of the governor. It represents the fluctuation degree of the speed of high-speed spatial and temporal load relative to the speed of full load, which can be calculated by the following formula: Q = N1 – N2 /n2×100%(1), where: Q — adjusting rate N1 — the idling speed of the diesel engine when all the load is suddenly discharged, r/minn2 — the speed at rated power, r/min
If the speed is too large, when the load changes, the diesel engine speed fluctuation is also large, affecting the stability of the engine high-speed work, and idling speed is too high, will increase the body wear; Adjust the rate is too small (that is, high speed control allergy), will also cause high speed operation instability. Generally, the adjustment rate of vehicle is best controlled in ≤10%, the adjustment rate of construction machinery is between 8% and 12%, and the rental generator set is ≤5%. The size of the adjustment rate is achieved by the correct adjustment of the speed regulating spring. Speed regulating spring after long-term use, the elastic coefficient will change because of fatigue, so that the adjustment rate becomes larger, even if reluctantly used, will not get a good control effect, it is best to replace. RSV governor’s high speed control and idle deputy spring plays a part, if this spring is not good, will also affect the control of the highest speed without load.
(2) uneven oil or oil cut-off time inconsistent engine speed to high speed with no load, if continue to improve the speed, speed governor flying piece of centrifugal force is too big, can overcome the tension of the governor spring, make through push pull rod oil gear lever to reduce oil direction, the position of oil supply bar and lower oil gear lever position. Therefore, if the idle fuel supply is not evenly adjusted, the error is too large, it is bound to affect the stability of the maximum speed without load.
When the engine reaches the speed of oil stop, the injection pump should automatically cut off the oil, but if the quality of the plunger, oil valve couple is not uniform, or because of wear and tear caused by the time of oil break is not consistent, there may be some cylinders have no oil, and some cylinders still have a small amount of oil supply or oil break is slow, which will become the cause of unstable high-speed operation.
Jiangsu Meiao Power Technology Co., Ltd. is an important manufacturer of diesel generators. The company mainly manufactures and sells diesel generator sets with power of 3-3000kW, mobile power station of 24-600kW, Marine emergency diesel generator set of 24-800kW, gas generator set, heavy oil generator set and all kinds of imported series, special series (trailer, static speaker, mobile lighthouse, container, etc.) diesel generator At the same time, we are engaged in generator set maintenance and after-sale service of generator set accessories.
