Oil Pumping Principle of Diesel Generator Set Plunger Pump

Today, we will introduce the oil pumping principle of some plunger pumps of diesel generator sets. The oil pumping mechanism of plunger pumps in diesel generator sets includes two sets of precision couplings, which have a great impact on diesel generator sets.

The plunger of the diesel generator set and the plunger sleeve of the diesel generator set are a pair of precision couplings, which cannot be interchanged after pairing and grinding. They require high precision, smoothness and good wear resistance, and their radial clearance is 0.002~0.003mm.

The cylindrical surface of the plunger head of the diesel generator set is cut with a chute, which is connected with the top through a radial hole and an axial hole, so as to change the circulating oil supply; The plunger sleeve of diesel generator set is provided with oil inlet and oil return holes, which are connected with the low pressure oil chamber in the upper body of the pump. After the plunger sleeve of diesel generator set is put into the upper body of the pump, it shall be positioned with set screws.

The method of changing the fuel supply is different with the different position of the chute at the plunger head of the diesel generator set. The oil outlet valve and the oil outlet valve seat are also a pair of precision coupling parts, which cannot be interchanged after pairing and grinding, and their fitting clearance is 0.01.

The oil outlet valve is a one-way valve. Under the spring pressure, the conical surface on the upper part of the valve closely matches with the valve seat. Its function is to isolate the high-pressure oil pipe from the upper cavity of the diesel generator set plunger when the supply is stopped, so as to prevent the oil in the high-pressure oil pipe from flowing back into the injection pump.

The lower part of the oil outlet valve is a cross section, which can guide and pass through diesel oil. There is a small cylindrical surface under the conical surface of the oil outlet valve, which is called the pressure reducing ring belt. Its function is to make the oil pressure in the high-pressure oil pipe drop rapidly at the end of oil supply, so as to avoid oil dripping at the orifice. When the ring belt falls into the valve seat, the upper volume increases rapidly, the pressure decreases rapidly, and the injection stops quickly.

Pump oil principle

During operation, under the action of the cam on the camshaft of the injection pump and the plunger spring of the diesel generator set, the plunger of the diesel generator set is forced to move up and down to complete the oil pumping task. The oil pumping process can be divided into the following three stages.

Oil inlet process

When the convex part of the cam turns, under the action of the spring force, the plunger of the diesel generator set moves downward, and the upper space of the plunger of the diesel generator set (called the pump oil chamber) generates vacuum. When the upper end surface of the plunger of the diesel generator set opens the oil inlet hole on the plunger sleeve of the diesel generator set, the diesel oil filled in the upper body oil passage of the oil pump enters the pump oil chamber through the oil hole, and the plunger of the diesel generator set moves to the bottom dead center, and the oil inlet is completed.

Fuel supply process

When the camshaft turns to the convex part of the cam to jack up the roller body, the plunger spring of the diesel generator set is compressed, the plunger of the diesel generator set moves upward, the fuel is pressurized, and part of the fuel flows back to the upper body oil chamber of the fuel injection pump through the oil hole. When the top surface of the plunger of the diesel generator set covers the upper edge of the oil inlet hole on the sleeve, the pump oil chamber at the top of the plunger of the diesel generator set becomes a sealed oil chamber due to the small fitting clearance (0.0015-0.0025mm) between the plunger of the diesel generator set and the sleeve. The plunger of the diesel generator set continues to rise, and the oil pressure in the pump oil chamber rises rapidly. When the pump oil pressure is greater than the spring force of the oil outlet valve+the residual pressure of the high-pressure oil pipe, push the oil outlet valve open, The high-pressure diesel enters the high-pressure fuel pipe through the outlet valve and is injected into the combustion chamber through the fuel injector.

Oil return process

The plunger of the diesel generator set supplies oil upward. When the chute (stop supply side) on the plunger of the diesel generator set is connected with the oil return hole on the sleeve, the low-pressure oil circuit of the pump oil chamber communicates with the central hole, radial hole and chute at the head of the plunger of the diesel generator set. The oil pressure drops suddenly, and the oil outlet valve quickly closes under the effect of the spring force to stop the oil supply. After that, the plunger of the diesel generator set will go up. When the convex part of the cam turns, the plunger of the diesel generator set will go down again under the action of the spring. The next cycle begins.

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