LO 7-1 Identify and describe the purpose, operating, and regulatory factors influencing cylinder component design and construction

1. What Are Cylinder Components?

What Are Cylinder Components?

Cylinder components are the engine components first used to convert combustion forces into mechanical power, which makes them a logical starting point to examine diesel engine construction Figure 1. Cylinder components include pistons, piston rings, piston pins (also called wrist pins ), piston pin bushings, and connecting rods (also called con-rods ) Figure 2. These components convert and transfer combustion forces to the crankshaft. They are also the most highly stressed parts of the diesel engine. Flame temperature of diesel fuel is over 3900° F (2149° C), and cylinder pressures can now exceed 3000 pounds per square inch (psi; 20,684 kilopascals [kPa]) of force. Because of these stresses, the design, construction, and operation of cylinder components are critically important to engine performance and durability. In addition, cylinder components (together with other engine systems) are used to reach emissions targets. Design updates and new construction techniques (necessary to meet regulatory standards) mean that cylinder components in contemporary diesels have undergone numerous refinements to help meet higher standards for performance, life expectancy, and low emissions output. Major engine repairs and rebuilding involve replacing or determining the serviceability (remaining service life) of these parts, so technicians need to familiarize themselves with the construction, operating principles, and failure modes of these parts. Engine failures often involve damage to cylinder components; therefore, analyzing failure modes is an important skill to identify and correct root causes of damage to these components. To maintain an engine’s compliance with regulatory standards, technicians should also familiarize themselves with emissions-related features to make correct service recommendations and follow best service practices.

FIGURE 07-1: Cylinder components are used to convert combustion forces into mechanical energy.

FIGURE 07-2: Cylinder components of a diesel engine.

1.1. Cylinder Components and Regulatory Standards

Cylinder Components and Regulatory Standards

Today’s diesel engines are not designed or constructed like those built a decade or more ago. Emissions legislation from the U.S. Environmental Protection Agency (EPA) and the European Union impose new design features on cylinder components through useful life requirements, which are legislated standards for engine durability. These regulations require manufacturers to build engines rugged enough to adapt to wear and with features that help them to remain emissions compliant throughout their useful life period. Greenhouse gas (GHG) and noxious engine emissions must remain below specific certification thresholds for the expected useful life of an engine. This means cylinder components are now constructed to extend engine life and meet durability requirements more than previous generations of engines TABLE 7-1.

TABLE 7-1: Engine Durability Requirements for Greenhouse Gas and Noxious Emissions   Category Useful Life EPA Standards EURO IV and V Standards EURO VI Standards Medium-duty 185,000 miles (297,729 km) 10 years Between 100,000–200,000 km (62,137–124,274 miles) or 6 years 300,000 km (186,411miles) or 6 years   Heavy-duty 435,000 miles (700,065 km) 10 years 500,000 km (310,686 miles) or 7 years 700,000 km (434,960 miles) 7 years Tier 3 (2017–2025) 150,000 miles (241,400 km) 15 years         To meet GHG legislation standards required for engines, friction reduction strategies are a top priority for manufacturers. Reducing internal friction means less fuel energy is wasted overcoming resistance between moving parts. Because cylinder components have considerable sliding friction between pistons, rings, cylinder walls, and on bearing surfaces, new materials and designs are rapidly changing the construction features of cylinder components Figure 3.

FIGURE 07-3: This articulated piston with a four-bolt connecting rod illustrates typical cylinder components.