Dual Cycle in Internal Combustion Engine

Summary:

The Dual Cycle is an air-standard cycle used in modern-era Diesel engines and hot-stop ignition engines. It combines constant pressure and constant volume heat addition for more efficient combustion. The cycle involves five processes: suction stroke, compression stroke, ignition phase, expansion stroke, and exhaust stroke. The P-V and T-S diagrams illustrate these processes. Various ideal formulas and thermodynamic relations are presented, including specific heat ratio, gas constant relations, heat added, heat removed, compression ratio, pressure ratio, cut-off ratio, expansion ratio, clearance volume, mean effective pressure, and cycle efficiency. The Dual Cycle finds applications in gas turbine-related machinery, high-speed compression engines, and electric generators.

Excerpt:

Dual Cycle in Internal Combustion Engine

INTERNAL COMBUSTION ENGINE
IV. Dual Cycle

A. WHAT IS A DUAL CYCLE?
A Dual Cycle is an air-standard cycle that uses both constant pressure and constant volume heat addition; it is also called Dual Combustion Cycle, Semi-Diesel Cycle, Mixed Cycle, Limited Pressure Cycle, Trinkler Cycle, Seiliger Cycle, or Sabathe Cycle. It was introduced by Russian-German Engineer Gustav Trinkler (who never claimed to have developed the cycle, though). This kind of cycle has a feature that has two ways of combustion, giving the fuel more time to completely combust, which is why it is used for modern-era Diesel engines and hot-stop ignition engines.

The Dual Cycle also has very high power-to-weight ratios making them applicable to gas turbine-related machinery (e.g. aircraft, helicopters, and ships), high-speed compression engines, and electric generators.

B. PROCESSES
An air-standard Dual cycle has five processes involved, which involve four-piston movements requiring two crankshaft revolutions to complete the four strokes (and one phase):

1. Suction Stroke – A stroke where the air from a vacuum chamber is sucked in below the atmosphere; the inlet valve is open while the exhaust valve is initially open here.
2. Compression Stroke – A stroke that raises the air temperature compressing them to the TDC; both intake and exhaust valves are closed here. This cycle, this one is also called isentropic compression.
3. Ignition Phase – In this phase, constant-volume heat addition from an external source is done while the piston rests on TDC, representing the subsequent rapid burning.