Engine Governing Methods – Which Applies to Compression-Ignition (Diesel) Engines? Compression-ignition engines control load and speed primarily using which governing method?

Introduction / Context:
Governing is the method by which engine output is regulated to meet load demands while maintaining speed. Different engine types achieve governing differently depending on how the charge is prepared and ignited. Understanding the correct approach for diesel engines helps explain their superior part-load efficiency and control strategies.

Given Data / Assumptions:

• Compression-ignition engine with direct injection of fuel into air.
• Airflow is largely unthrottled; load is controlled by fuel quantity.
• Governor adjusts injected fuel mass per cycle to control speed.

Concept / Approach:

Quantitative governing varies the total quantity of fuel injected while the amount of air is essentially constant for a given speed and boost. This is the hallmark of diesel operation. In contrast, qualitative governing (varying mixture strength) is typical of early gas engines and some SI systems, while hit-and-miss is associated with small, old stationary engines where firing cycles are skipped to control speed.

Step-by-Step Solution:

Verification / Alternative check:

Governor linkages or electronic control units adjust injection duration or rail pressure to vary fuel per stroke, directly demonstrating quantitative governing in practice.

Why Other Options Are Wrong:

Qualitative governing varies mixture quality, not applicable to diesel intake. Hit-and-miss is obsolete for modern diesels. A combination is not the standard diesel approach.

Common Pitfalls:

Confusing throttle-based SI control with diesel control; assuming diesels regulate air mass the same way as gasoline engines.

Final Answer:

quantitative governing (varying quantity of fuel admitted)