Part 1: Engage (Anchoring Phenomenon)

Sometimes, a heavy-duty diesel truck will suddenly start accelerating wildly, emitting massive clouds of black smoke, and screaming at a dangerously high RPM. Even if the driver takes their foot completely off the gas pedal, the engine won’t stop. Turning the key off doesn’t work either! This terrifying event is called a “diesel runaway,” and the engine will literally run itself until it explodes or runs out of air.

1. Observations and Questions:

• How is it possible for an engine to continue running and accelerating without the driver adding fuel via the pedal?
• Generate at least two “need to know” questions about what is happening inside the engine cylinders during a runaway event.

Part 2: Explore (Simulation Investigation)

Open the Diesel Engine Runaway Phenomenon simulation.

2. Data Collection:

• Start the simulation in Normal Operation. Observe the intake, compression, power, and exhaust strokes. What is the source of the fuel being burned?
• Observe the energy outputs (like heat and motion). How does the system stay balanced?
• Trigger the Runaway Condition (e.g., introducing a leak in the oil seal). What new substance enters the combustion chamber?
• Observe the RPM gauge and the temperature gauge. What happens to the rate of energy conversion (kinetic energy and thermal energy) once the runaway starts?

Part 3: Explain (Sensemaking)

3. The Unintended Fuel Source:

• In a runaway condition, what is the engine using as its fuel source instead of regular diesel fuel?
• Why does turning the ignition key off fail to stop the engine in this situation? (Think about what a diesel engine needs to ignite fuel compared to a gasoline engine).

4. Energy at the Macroscopic Scale:

• During the runaway, describe the changes in energy at the macroscopic scale (e.g., the motion of the pistons, the heat of the engine block).
• How is the chemical potential energy stored in the engine oil being converted during this uncontrolled event?

Part 4: Elaborate/Evaluate (Argumentation & Modeling)

5. Developing a Model of Runaway: Develop a model to illustrate the energy transformations during a diesel runaway. Your model must illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles and their relative positions. Include:

• Relative Position (Potential): The chemical energy stored in the engine oil (the unintended fuel).
• Motion of Particles (Kinetic/Thermal): The extreme heat and pressure generated in the cylinder, and the rapid motion of the pistons (macroscopic kinetic energy).
• The Feedback Loop: Show why the reaction becomes self-sustaining and accelerates (more heat -> burns more oil -> creates more heat).