Commings engine PT spray hole drop oil phenomenon analysis

In the early 80s, the Shandong bulldozer main plant the D85A-18 crawler dozer which introduced from the Japanese small pine manufacture, used the Commings engine. Commings engine PT fuel delivery system's characteristic:��The fuel feed is decided in the PT pump supplies spray hole fuel pressure and opens the spray hole gauged orifice the absolute time.��The PT pump is the low press pump, the discharge pressure generally in 0.8~1.2MPa, the spray hole spraying fuel oil pressure in 68~136MPa.��The PT fuel system (Figure 1), fuel oil tank's position is higher than the PT pump and the PT spray hole.

Figure 1 PT fuel system's composition

1 PT spray hole structure

The PT spray hole is the machinery opens the type spray hole. In the spray hole mouth the uniform distribution has 7 or 8 nozzles, the nozzle diameter approximately 0.2mm, the nozzle spool thread with is vertical has 17�� the angle in the spray hole plunger 17 spool thread's planes, its structure see Figure 2.

Figure 2 PT spray hole structure

2 PT spray hole drop oil phenomenon analysis

The PT fuel system pertinent data indicated that the PT spray hole's fuel oil measurement stage is moves from the piston after the intake stroke top dead center when the crank corner 44�� position starts, moves upwardly until the piston before the compression stroke top dead center 28�� the crank corner position, in the spray hole measurement stage, the fuel oil enters the oil duct and the spray hole pressure chamber is interlinked, again 7 or 8 nozzles and the air cylinder is interlinked through the pressure chamber mouth. The spray hole has provided the possibility in the structure for the drop oil phenomenon. the table 1 (take 6 cylinder engines as example, work order is 153624) draws the oblique line part for each cylinder PT spray hole fuel oil measurement stage crank corner position. May see crank's any position from the table to correspond has 2 or 3 cylinder's stage PT spray holes is at the fuel oil measurement stage.