MPRR

AcronymDefinition
MPRRMissouri Pacific Railroad
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It has been demonstrated that too early first injection timing would lead to high CO and HC emissions and consequently low combustion efficiency, while late first injection timing results in high MPRR and combustion noise.
Due to the single heat release process, MPRR in HCCI mode is high, achieving or exceeding the criteria of 10 bar/deg as shown in Figure 7.
In HCCI mode, larger IMEP or higher compression ratio would lead to higher MPRR, exceeding the criteria of 10 bar/deg.
Design candidates from the DoE optimization Operating SOI TNA Nozzle Angle Bowl CR conditions #Nozzle [CAD] (diameter) [[degrees]] B50 -9 ARCD_C 20.5 B75 9 -6 1.3 149 A75 -5 (0.2mm) C100 -2 B50 -8 ARCD_E 20.5 B75 9 -6 1.3 158 A75 -5 (0.2mm) C100 -2 Bowl ISFC [g/hp-hr] Soot [g/kg_fuel] N[O.sub.x] [g/kg_fuel] 118.9 -1.9% 0.126 -33.3% 21.6 7.4% ARCD_C 112.0 -1.9% 0.095 -24.8% 20.8 -4.1% 120.7 -2.8% 0.059 -49.7% 20.8 -19.2% 122.2 -1.2% 0.133 -18.2% 18.7 -10.3% 119.5 -1.1% 0.195 3.5% 21.2 5.3% ARCD_E 121.5 -1.6% 0.124 -1.9% 22.3 2.8% 121.4 -2.3% 0.077 -34.8% 20.4 -20.8% 121.2 -2.0% 0.112 -30.9% 23.0 10.6% Bowl MPRR [bar/ca] PCP [bar] EGR 8.0 173.2 36.2% ARCD_C 7.7 217.9 33.3% 9.1 210.9 32.8% 6.9 221.2 28.0% 7.6 170.1 35.9% ARCD_E 8.0 217.4 33.2% 9.7 208.2 32.8% 6.9 224.4 29.5%
Naphtha 2 was formulated to target a RON of 70 (CN30), which has been shown in the literature to offer a wide PPCI operation range with a good balance between MPRR control at high load and combustion stability at low load [11].
Cylinder pressure and heat release rate at A25, B50, and C100 for Naphtha 1 SET operation at engine-out NOx of 2 g/hp-hr A25 B50 C100 SOI [[degrees]ATDC] -6 -7 -5 CA50 [[degrees]ATDC] 4.4 6.4 11.0 ID CAD 6.3 4.2 3.3 CD CAD 14.0 20.8 24.1 MPRR [bar/CAD] 8.0 7.4 5.6 Note: Table made from bar graph.
The key engine operation limits imposed were: NOx [less than or equal to] 0.2 g/hp-hr, smoke [less than or equal to] 0.2 FSN, and MPRR [less than or equal to] 15 bar/CAD.
Early PPCI cylinder pressure and heat release rate for Naphtha 1 and Naphtha 2 at 5 bar BMEP Naphtha 1 Naphtha 2 SOI [[degrees]ATDC] -15 -15 CA50 [[degrees]ATDC] -0.4 1.8 ID [CAD] 11.8 14.0 MPRR [bar/CAD] 13.9 13.1 Note: Table made from bar graph.
With decreasing Diesel fraction, the MPRR (see Figure 5) and the ROHR (see Figure 6) is lowered and wall heat losses are slightly reduced, which compensates losses due to incomplete combustion.
This might explain the continuous increase in CO-emissions, the continuous decrease in MPRR as well as the reduced need for EGR to be compliant to EU-6 N[O.sub.x]-emissions at high ethanol shares.
In addition to the engine-out pollutant emissions, noise emissions could also be lowered by reducing the MPRR even below that of Diesel.
Even though the MPRR is lower at RCCI operation and the given COV(IMEP) of 2% is well within the limits, RCCI causes higher fluctuations in the peak firing pressure (PFP), see Figure 10.