ML20043F674
| ML20043F674 | |
| Person / Time | |
|---|---|
| Issue date: | 02/12/2020 |
| From: | Office of the Chief Human Capital Officer, Woodard Corp |
| To: | |
| Gary Callaway | |
| Shared Package | |
| ML20043F634 | List:
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| References | |
| Download: ML20043F674 (51) | |
Text
Chapter 3 DIESEL ENGINE CONSTRUCTION
Learning Objectives As a result of this chapter, you will be able to:
- 1. Describe the basic construction and identify the loads imposed on structural components of a diesel engine.
- 2. Describe the basic construction and function of major rotating and reciprocating components of a diesel engine.
- 3. Describe the basic construction and state the function of cylinder head, valves, and related components of a diesel engine.
- 4. Describe the basic construction and purpose of camshafts, cam followers, and valve operating mechanisms.
Structural Components Must have sufficient strength and rigidity To absorb dynamic forces of the pistons and maintain alignment of the cylinders to the crankshaft.
To absorb the dynamic and torsional forces created by crankshaft loadings.
Figure 3-1 Cylinder Forces
60K 54K 48K 42K 36K 30K 24K 18K 12K 66K VERTICAL FORCES CYLINDER FORCES - POUNDS X 1000 HORRIZONTAL FORCE Figure 3-1A Vertical and Lateral Forces during power stroke superimposed on Pressure vs Crank-angle Diagram.
Figure 3-2 Multi-Piece Construction
Figure 3-3 12-Cylinder OP Engine Cylinder Block
Figure 3-4 16-Cylinder PC Engine Cylinder Block
Engine Cylinders The bore of each cylinder provides the enclosure which acts to guide the motion of pistons.
The wall of the cylinder works in conjunction with the piston rings to create a gas tight seal to prevent loss of combustion pressure.
Most diesel engines use replaceable cylinder liners rather than boring cylinders directly into the engine block. Examples of cylinder liners are shown on Figures 3-5, 3-6, and 3-7.
Figure 3-5 Dry Type Cylinder Liner
Figure 3-6 Wet Type Cylinder Liner
Figure 3-7 Integral Type Cylinder Liner
Engine operation involves the relative motion of a vast number of individual components. Where there is relative motion, and loads or forces are being transmitted, some type of bearing is normally used:
Journal bearings - engine main and connecting rod bearings.
Figure 3-24 (later) shows OP engine crankshaft -
typical of all crankshafts, which are supported by journal type bearings.
Figure 3-8 OP Engine Main Bearings
Figure 3-8-A OP Engine Main Bearings (Top Enlarged)
Figure 3-8-B OP Engine Main Bearings (Bottom Enlarged)
Roller bearings are typically used in components such as jacket water pumps, lube oil pumps, cam followers, and governor drive mechanism bearings, vertical drives, auxiliary drives, etc.
Journal type bearings are capable of much higher loading than are roller, tapered roller or ball bearings. This will be discussed in Chapter 5, Engine Lubrication Systems.
Rotating and reciprocating components:
Must be properly designed to perform their functions.
Must be constructed of proper materials to withstand dynamic forces and temperatures involved in operation of the engine.
Must be designed and constructed with proper interfaces between stationary components to ensure operation and longevity.
Pistons and associated parts The next few slides show designs of pistons and the parts most associated with the piston, such as the rings, connecting rods, con-rod bearings, and their association to the crankshaft.
Figure 3-9 OP Piston and Con-Rod Assembly
Figure 3-10 Trunk Type Piston
Figure 3-11 Floating Skirt Piston used on EMD Engine.
Figure 3-12 Piston Ring Nomenclature
Figure 3-13 Piston Ring Sealing (Compression Rings)
Figure 3-14 Compression Ring Designs (Rectangular or Barrel/Crowned are most common)
Figure 3-15 Piston Ring Joint Designs (Square Cut is most common)
Figure 3-16 Oil Control Ring
Figure 3-17 Oil Control Ring Designs
Figure 3-18 Piston Ring Placement
Figure 3-19 Two-piece Crown Piston with Connecting Rod and Wrist Pin Assembly
Figure 3-20 Conventional Connecting Rod Figure 3-21 Angle-Cut Connecting Rod
Figure 3-22 Articulated Connecting Rod Assembly
Figure 3-23 Fork and Blade Connecting Rod Design EMD
Figure 3-24 OP Engine Crankshafts
Figure 3-25 Engine Crankshaft Oil Passages
Flywheels and Torsional Dampers Following slides show a flywheel and torsional dampers used on most engines to steady the crankshaft twisting induced by energy impulses from firing of each cylinder. In EDG service, the generator supplies enough flywheel effect that the engine does not need its own flywheel.
Flexible drive assemblies resemble torsional dampers and work much the same way - to dampen torsional vibrations so they don't harm other components of the engine.
Figure 3-26 Engine Flywheel
Figure 3-27 Spring Type Vibration Damper
Figure 3-28 Gear Type Viscous Vibration Damper
Figure 3-29 Bifilar Type Vibration Damper
The engine cylinder heads:
Provide closure of the engine cylinder to the engine block.
Provide for mounting of the valve operating rocker arms on top of the cylinder heads, and valves in the cylinder heads.
Provide for cooling water circulating, through the heads, to remove excess heat.
Provide location for mounting fuel injectors.
Figure 3-30 Cylinder Head Assembly
Figure 3-31 Valve Seat Angles Figure 3-32 Valve and Spring Assembly
Camshafts and their cam followers perform the following functions, in the proper time sequence, during the combustion cycle:
Actuate intake and exhaust valves to open and close via push rods and rocker arm assemblies.
Actuate fuel injection pump plungers to provide fuel at high pressure to the injectors.
Figure 3-33 Camshaft Lobes
Figure 3-34 Cam Followers
Camshafts are either gear-or chain-driven to maintain a positive, direct relationship with the crankshaft as shown in Figures 3-35 and 3-36.
Figure 3-35 Gear Type Camshaft Drive Mechanism
Figure 3-36 Chain-Type Camshaft Drive Mechanism OP Engine
Figure 3-37 Rocker Arms and Pushrods
END OF CHAPTER 3