Plain summary
A two‑piston, pressure‑coupled cylinder that “self‑charges” the chamber each cycle. The floating piston shares the combustion space but is not crank‑driven; the same in‑cylinder pressure accelerates both pistons in the same direction, raising indicated work without crank back‑drive. Shaped timing/area of the floating piston produces unsteady in‑cylinder compression and scavenging—an internal, every‑cycle charging effect.

Conventional engines sacrifice efficiency to friction at high mean piston speed and to pumping/heat losses during gas exchange. By increasing indicated work at lower RPM while improving charge preparation, the Self‑Charging Cylinder targets lower fuel consumption and emissions—first in stationary power and heavy‑duty applications, then in broader ICE/hybrid use cases.

1. Decoupled floating piston. Shares the chamber but is not mechanically linked to the crankshaft; no shaft back‑drive.
2. Pressure‑driven motion. During combustion, the pressure field does work on both pistons, with the crank receiving torque only from the main piston.
3. Unsteady charging. The floating piston’s geometry and timing create cycle‑by‑cycle compression and enhanced airflow/scavenging inside the cylinder—an internal supercharging effect without external compressors.

Phased coupling (overview). We start decoupled so in‑cylinder pressure drives the floating piston to co‑accelerate with the main piston in the same direction. After geometry/timing are validated, we link the floating piston to the crank via two rods to stabilize motion, capture a small net positive torque contribution (~3% historically observed from skirt‑effect data), and use the return portion of the power event to compress the air above the floating piston—replacing the separate compression stroke in a conventional cylinder.

Initial decoupled mode (technical). Combustion pressure first accelerates the floating piston toward the crank, aligning its motion with the main piston. As the pressure field evolves, the floating piston’s instantaneous acceleration can change sign, but its net displacement over the cycle remains co‑directed with the main piston. Any small pressure‑driven “shake” informs sizing/timing during this phase.

Stabilized linked mode (technical). Once validated, two connecting rods couple the floating piston to the crank. The crank then damps residual oscillation and harvests a small average positive driving force. During the return, the linkage provides the additional function of compressing the air pocket above the floating piston. This is not an added loss vs a conventional cylinder; it relocates compression work (done in a separate stroke in conventional cycles) into the return of the same cycle, while the Relative Motion Cylinder may employ a larger bore and shorter stroke.

• Static Pascal assumptions fail in open, unsteady flow. Early concepts that treated the chamber like a closed hydraulic system (or added springs) under‑performed.
• Co‑acceleration is key. Removing springs and shaping the floating piston to co‑accelerate with the main piston improved unsteady compressible‑flow coupling and charge handling.
• Use standard engine metrics. Report IMEP/indicated work separately from PCP (peak cylinder pressure) and from brake metrics (BMEP/BSFC). Avoid nonstandard terms.

• Indicated cycle work: ~30–40% increase vs a matched single‑piston baseline (ANSYS/CONVERGE studies, 2017–present).
• Pressure capability: simulated PCP up to ~180 bar with acceptable pressure‑rise rates in tuned cases.
• Charge enhancement: at selected operating points, simulations show up to ~2.6× airflow vs conventional naturally aspirated (NA) operation—comparable to strong turbocharging without external hardware.
• Friction potential: operation at lower mean piston speed for a given brake load targets FMEP reductions (quantified by motored tests in hardware).

All figures above are simulation‑only until confirmed on an instrumented single‑cylinder test rig. Full model details (mesh, chemistry, turbulence, wall heat transfer, boundary/ICs, sensitivity) will accompany publication.

• “Space void.” In standard terms: transient gas displacement by the floating piston that raises local pressure and changes in‑cylinder flow. We describe this as a pressure‑wave/gas‑spring effect, not a literal void.
• “Trapped mass phenomenon.” Certain CONVERGE post‑processing runs reported apparent trapped mass above the nominal input. We treat this as a modeling/recirculation and discretization artifact until verified experimentally. We continue to collaborate on diagnostics and mesh/solver sensitivity.

• Higher indicated work at lower RPM → potential BSFC gains after friction/pumping losses are measured.
• Internal, every‑cycle charging → improved mixture preparation and scavenging without external compressors.
• Friction reduction via lower mean piston speed for a given brake load (to be quantified as FMEP).
• Diesel‑class power density at lower rated speed. Completing effective gas‑exchange every cycle can raise work per rev; goal: match gasoline‑class power density with diesel‑class speeds (hardware validation pending).
• Materials & NVH potential. Concentrating peak combustion loads within the floating‑piston structure may enable aluminum blocks in diesel‑class applications and reduce block‑borne noise/vibration (to be tested).
• Emissions levers in‑cylinder. Mixture/temperature control and pressure‑wave charging aim to reduce aftertreatment load; we will demonstrate NOx/CO/HC/PN vs baseline on a certified bench.
• EGR conflict mitigation. Internal re‑breathing via exhaust valve sizing/position can decouple airflow enhancement from NOx control, targeting 30–40% internal exhaust fraction without intake‑path recirculation.
• Oil consumption. A patented sleeve/sealing approach addresses historical sleeve‑engine oil usage (details under NDA).

Validated in simulation

• +30–40% indicated work (IMEP) at selected points.
• PCP ~180 bar in tuned cases with acceptable PRR.
• Up to ~2.6× airflow vs NA baseline at matched conditions.

To be validated in hardware

• BSFC improvement at equal brake torque (target ≥10%).
• FMEP reduction at matched load/speed.
• Emissions: NOx/CO/HC/PN equal‑or‑better than baseline.
• Durability, blow‑by, and NVH within design limits.

• Vibration management: pressure‑coupled floating piston reduces lateral forces and block‑borne excitation.
• Friction: fewer high‑speed valvetrain events at a given output → lower FMEP potential.
• Parts count: simplified external air‑handling; potential elimination of side camshafts in some architectures.
• Gas exchange: no partial loss of compressed intake through early exhaust opening; longer effective scavenging window per cycle.
• Scalability: internal charging can stand alone or stack with turbocharging if higher overall pressure ratio is required.

• Naturally aspirated internal‑charging for simplicity and cost.
• Hybrid with turbocharging where additional pressure ratio is needed.
• Control strategy uses piston geometry/timing and conventional ECU maps for SoI/spark/EGR; no exotic hardware required.

• Phase 1: single‑cylinder rig with fast in‑cylinder pressure, torque, emissions bench; IMEP/BMEP/BSFC mapping and motored FMEP.
• Phase 2: 25–100 kW pilot genset prototype with partner; third‑party validation.
• Phase 3: certification pathway and OEM licensing/retrofit packages.