Examkin

Question

Difficulty: MediumEngine Principles and Internal Components

Inside an engine cylinder, both the intake and exhaust valves remain sealed shut while the piston travels upward from bottom dead center (BDC) toward top dead center (TDC). Which stroke of the operating cycle is taking place?

  1. A
    Exhaust stroke
  2. Compression strokeAnswer
  3. C
    Power stroke
  4. D
    Intake stroke

Answer

Compression stroke
During the compression stroke, the piston travels upward from bottom dead center (BDC) to top dead center (TDC) to compress the air-fuel mixture into the combustion chamber, which requires both the intake and exhaust valves to remain completely closed.

Step-by-Step Solution

1
Analyze the valve operating states
Both the intake and exhaust valves are fully closed.
Both valves are closed only during two phases of the four-stroke cycle: the compression stroke and the power stroke.
2
Evaluate the direction of piston travel
The piston travels upward from BDC toward TDC.
Upward piston motion reduces the volume of the combustion chamber, compressing the trapped charge.
3
Combine physical conditions to identify the stroke
The cycle phase is the compression stroke.
The power stroke involves downward piston travel, making the compression stroke the only phase matching upward motion with both valves closed.

Key Concept

Four-stroke internal combustion engine cycle phases and valve operating states
Estimated Time:45s
Rate this question

Topics

Engine Principles and Internal Components

More questions from this topic