Một số ví dụ được cung cấp như các tập tin của ổ đĩa được đọc vào chương trình. Đây là những ghi nhận trong văn bản. Học sinh được khuyến khích để điều tra các ví dụ với ENGINE chương trình để phát triển một sự hiểu biết và cái nhìn sâu sắc đến sự tinh tế của chủ đề này. Hướng dẫn sử dụng cho động cơ chương trình được cung cấp trong Phụ lục A có thể được đọc hoặc được gọi trong chuỗi, không có mất mát trong liên tục, để có được quen với các. | FIGURE 13-20 Free-body diagrams for forces due to masses at the crankpin Note that unlike the inertia force in equation p. 619 which was unaffected by the gas force these pin forces are a function of the gas force as well as of the -ma forces. Engines with larger piston diameters will experience greater pin forces as a result of the explosion pressure acting on their larger piston area. Program ENGINE calculates the pin forces on all joints using equations to . Figure 13-21 shows the wrist-pin force on the same unbalanced engine example as shown in previous figures for three engine speeds. The bow tie loop is the inertia force and the teardrop loop is the gas force portion of the force curve. An interesting trade-off occurs between the gas force components and the inertia force components of the pin forces. At a low speed of 800 rpm Figure l3-2la the gas force dominates as the inertia forces are negligible at small co. The peak wrist-pin force is then about 4200 lb. At high speed 6000 rpm the inertia components dominate and the peak force is about 4500 lb Figure 13-2lc . But at a midrange speed 3400 rpm the inertia force cancels some of the gas force and the peak force is only about 3200 lb Figure 13-2lb . These plots show that the pin forces can be quite large even in a moderately sized liter cylinder engine. The pins links and bearings all have to be designed to withstand hundreds of millions of cycles of these reversing forces without failure. Figure 13-22 shows further evidence of the interaction of the gas forces and inertia forces on the crankpin and the wrist pin. Figures 13-22a and 13-22c show the variation in the inertia force component on the crankpin and wrist pin respectively over one full 630 DESIGN OF MACHINERY CHAPTER 13 a 800 rpm b 3400 rpm 1 Cylinder 4 Stroke Cycle Bore in Stroke B S UR c 6000 rpm FIGURE 13-21 Forces on the wrist pin of the single-cylinder engine at various speeds ENGINE DYNAMICS 631 .
