High-speed compression engines: identify the thermodynamic cycle of operation In internal-combustion engine theory, high-speed compression-ignition (diesel) engines are modeled to operate on which idealized cycle for analysis and design understanding? Choose the correct option.

Concept
High-speed compression-ignition engines are better represented by the dual (mixed) cycle, which has part constant-volume heat addition (to capture rapid initial combustion) and part constant-pressure heat addition (to capture continued burn during piston travel). Low-speed CI engines are closer to the ideal Diesel cycle; SI engines are modeled by the Otto cycle.

Why the other options are not best
Otto cycle assumes fully constant-volume heat addition (typical for SI). Diesel cycle assumes fully constant-pressure heat addition. The dual cycle combines both, matching high-speed CI combustion phasing more closely.

Final Answer
Dual-combustion (mixed) cycle