Electron Microscopy Investigation of Particulate Matter from a Dual Fuel Engine

Figures & data

TABLE 1 Engine specifications

Engine type	Lister Petter single- cylinder, DI, water cooled
Bore/Stroke	87.3/110 (mm)
Swept volume	659 (cm^3)
Connecting rod length	231.9 (mm)
Compression ratio	16.5
Injection timing by spill	28°bTDC
Engine speed	1750 rpm

FIG. 1 TEM micrograph showing the measurements of primary particle area in an agglomerate and the maximum projected length (L_max) and width (W_max) of the agglomerate.

FIG. 2 Primary particle size distributions at different engine fueling conditions: (a) diesel low load (3 nm); (b) diesel high load (28 nm); (c) diesel-NG (28 nm); (d) diesel-BG1 (80% CH₄ and 20% CO₂) (28 nm); (e) diesel-BG2 (67% CH₄ and 33% CO₂) (28 nm); (f) diesel-BG3B (58% CH₄ and 42% CO₂) (28 nm); and (g) diesel-BG3A (59% CH₄, 41% CO₂ and about 820 ppm H₂S) (28 nm).

FIG. 3 Number size distribution with fitted bimodal lognormal distribution of the PM agglomerates measured for different engine operating conditions. CMD = count median diameter; GSD = geometric standard deviation.

FIG. 4 Shape factor (SF) trends of the PM collected on SEM filters for diesel and dual fueling (1750 rpm, and pilot = 0.6 kg/h for dual fueling).

TABLE 2 Fractal dimensions of the PM sampled for different engine fueling conditions

Engine fueling	Fractal dimension, D fL
Diesel low load	1.72
Diesel high load	1.69
Diesel-NG	1.73
Diesel-BG2 (67% CH4 and 33% CO2)	1.80
Diesel-BG3B (58% CH4 and 42% CO2)	1.84
Diesel-BG3A (59% CH4, 41% CO2 and about 820 ppm H2S)	1.88

TABLE 3 Fractal dimension measured for the PM sampled from CH₄/O₂ premixed flames and diesel-NG dual fueling in diesel engine.

Investigators	PM source	Method	Fractal dimension
Zhang et al. (1988)	CH4/O2 premixed flame	TEM	1.72 ± 0.10
		LS	1.61 ± 0.06
Gangopadhyay et al. (1991)	CH4/O2 premixed flame	LS	1.6–1.8
Sorensen et al. (1992)	CH4/O2 premixed flame	LS	1.70–1.79
Cai et al. (1993)	CH4/O2 premixed flame	TEM	1.70
Cai et al. (1995)	CH4/O2 premixed flame	TEM	1.74
This work (diesel engine)	Diesel-NG dual fueling	TEM	1.73
	Diesel-biogas dual fueling	TEM	1.8–1.88

FIG. 5 Plot of fractal data of PM agglomerates sampled for diesel low load operation (best fit with D _fL = 1.72). The number of primary particles per agglomerate N is correlated with the fractal dimension as, N = k _L(L _max/

_P ) ^{D _fL} ; While the fractal dimension, D _fL represents the slope, k _L (a correlation prefactor) determines the magnitude of the least-squares linear fit to the data in the ln (N) versus ln (L _max/

_p ) plot.

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