Tham khảo tài liệu 'mechanism of steam engines part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | lổ MECHANISM OF STEAM ENGINES work done by the steam during the forward stroke and the work done against the steam during the return stroke will be the net work done by the steam on the head end of the piston during a complete revolution of the crank. The work done in the crank end can be found in the same way. The sum of the two will be the total work done on the piston during one revolution. This multiplied by the number of revolutions per minute and divided by 33 000 will give the horse power of the engine. In actually making use of the card to find the power which the engine is developing the following method is commonly used. The area enclosed by the curve ABCRK is measured in square inches by an instrument called a planimeter. This area divided by the length of the card in inches will give the average of all the ordinates which represent net effective pressures that is the average of all the ordinates for the upper curve minus the average of the ordinates on the lower curve. This average net length of ordmate multiplied by the scale of the indicator spring gives the average effective pressure per square inch of piston area which is available throughout a complete revolution for work on that side of the piston. The name mean effective pressure abbreviated . is commonly given to this quantity. Then . X area of piston in square inches X length of stroke in feet X . 4- 33 000 . indicated by this card. The sum of this result and the corresponding one for the other end will give what is known as the indicated horse power of the engine . . 14. Types of Engines. Reciprocating steam engines may be classified in a variety of ways some of which are as follows 1. By position a Horizontal. Ỉ Vertical. 2. By expansion of steam a Simple. 6 Compound. c Multiple-expansion. Cross compound. Tandem compound. Angle compound. 3. By disposal of exhaust ơ Non-condensing. 6 Condensing. 4. By kind of valve or valve mechanism. GENERAL DISCUSSION OF A .