Four-stroke cycle

Definition

The four-stroke cycle is a thermodynamic process used in internal combustion engines, which completes a power cycle in four distinct strokes: intake, compression, power, and exhaust. Each stroke corresponds to a specific movement of the piston within the cylinder, converting fuel into mechanical energy efficiently. This process is crucial for the functioning of piston engines, facilitating the conversion of chemical energy from fuel into kinetic energy to drive vehicles and machinery.

5 Must Know Facts For Your Next Test

1. The four-stroke cycle is used in many automotive engines, making it a fundamental concept in understanding engine operation.
2. Each complete cycle requires two full rotations of the crankshaft to complete all four strokes.
3. The efficiency of the four-stroke cycle is enhanced by using a cooling system that helps maintain optimal engine temperatures.
4. Fuel injection systems in modern engines often improve the performance of the four-stroke cycle by delivering precise amounts of fuel at the right time.
5. The exhaust stroke clears out burnt gases from the combustion chamber, making room for fresh air-fuel mixture in the next intake stroke.

Review Questions

• Explain how each stroke in the four-stroke cycle contributes to the overall efficiency of an internal combustion engine.
  • Each stroke in the four-stroke cycle plays a critical role in maximizing engine efficiency. The intake stroke draws in a fresh air-fuel mixture, while the compression stroke compresses this mixture to increase its energy potential. The power stroke then harnesses this energy through combustion, pushing the piston down to create mechanical power. Finally, the exhaust stroke removes spent gases from the cylinder, allowing for a clean intake of new mixture in the next cycle. Together, these strokes ensure that fuel is effectively converted into usable power while minimizing waste.
• Discuss how advancements in fuel injection technology have impacted the performance of engines utilizing a four-stroke cycle.
  • Advancements in fuel injection technology have significantly enhanced the performance of four-stroke engines by providing more precise control over fuel delivery. This precision allows for better combustion efficiency and improved throttle response. Electronic fuel injection systems can adjust fuel flow based on engine conditions, optimizing performance under various loads and speeds. As a result, engines are able to produce more power with better fuel economy and lower emissions compared to traditional carburetor systems.
• Evaluate the implications of environmental regulations on the design and operation of modern four-stroke engines.
  • Environmental regulations have greatly influenced the design and operation of modern four-stroke engines by necessitating reductions in emissions and increased fuel efficiency. Engineers are now required to incorporate advanced technologies such as catalytic converters and improved combustion processes to meet strict emission standards. These changes often lead to more complex engine designs that may increase production costs but also enhance performance and sustainability. The push for greener technologies has also accelerated research into alternative fuels and hybrid systems, shaping the future direction of engine development.

Related terms

Intake Stroke: The first phase of the four-stroke cycle where the piston moves down, creating a vacuum that allows the air-fuel mixture to enter the cylinder.

Compression Stroke: The second phase where the piston moves up, compressing the air-fuel mixture, which increases its temperature and pressure before ignition.

Power Stroke: The third phase of the cycle where the ignited air-fuel mixture expands rapidly, pushing the piston down and producing power.