**Nomenclature**


(The variable with superscript "\*" is its dimensionless form.)

The in-cylinder pressure curves with different ignition compression ratio while *Leff*\*=0.6765 are shown in Fig.23. It is clear that smaller ignition compression ratio or bigger ignition advance leads to higher peak pressure which is in agreement with the dimensionless results.

The in-cylinder pressure curves with different ignition compression ratio while *Leff*\*=1.0294 are shown in Fig.24. The sequence of the peak pressure achieved with different ignition compression ratio is <sup>4563</sup> *ign ign ign ign pppp* , which supports the dimensionless results. The combustion duration calculated via CFD is about 4.4~5.6ms with different ignition timings and effective stroke length, which has some deviation with the value in numerical simulating program which is defined based on the heat release rate of FPLA prototype. The deviations can be eliminated by using an iterative procedure between the numerical simulating program and CFD calculation when calculating a specific free-piston engine.
