The results at the fast idle condition (1200 rpm, 2 bar NIMEP) are shown in Fig.
The accumulation mode PN emissions for premixed methane-air mixture as a function of NIMEP are shown in Fig.
At 2000 rev/min the engine was successfully able to run at an NIMEP level equivalent to 23.6 bar BMEP on a multi-cylinder engine at stoichiometric air fuel ratio.
Inlet pressure is visibly higher in the Magma case, to compensate for reduced inlet valve opening period (NIMEP is also higher in this case, requiring increased airflow).
Delaying the intake timing results in lower NIMEP for cycles #1 and #2 due to the reduced effective compression ratio (Figure 11, top).
The higher residual gas fraction from early EVC does not impact substantially the NIMEP trace and the engine speed run-up when compared to the baseline case.
The rightmost points with each stroke in Figure 3 are those at the maximum achievable EGR rate, and thus maximum work or nIMEP. Those in the lower left plots are with the timing optimized for best efficiency (MBT timing).
Data taken at 4000 rpm is presented in Figures 5 and 6, with nISFC plotted versus nIMEP and EGR rate respectively.
The NIMEP and HC emissions as a function of the injection timing are shown in Fig.
Figures 18 and 19 show the dependence of NIMEP, HC and PM emissions on the combustion phasing, quantified by the point for 50% of heat release (CA50).
18, right), the early EVC setting resulted in lower NIMEP. This difference can be explained by the GIMEP loss associated with early EVO, and the increase in pumping losses caused by the early EVC (see Fig.
A sharp reduction in NIMEP is observed for the first three engine cycles of the symmetric NVO case.