Characterization of structure of single particles from various automobile engines under steady-state conditions

Figures & data

Table 1. List of engines and vehicles used in this study.

		Engine size [L]	Model year	After treatment	Emission regulation	Mileage [km]
Diesel A	Engine of heavy-duty vehicle	8.00	1997	none	1992	—
Diesel B	Light-duty truck	2.95	2004	DOC	2002	34,700
Diesel C	Diesel passenger car	2.18	2012	DOC+DPF	2009	40,600
DISI A	Gasoline direct injection spark ignition passenger car	1.30	2011	three-way catalyst	2005	8000
DISI B	Gasoline direct injection spark ignition passenger car	1.79	2014	three-way catalyst	2009	14,200
PFI A	Gasoline port fuel injection passenger car	1.99	2014	three-way catalyst	2005	7400
PFI B	Gasoline port fuel injection passenger car	1.59	2014	three-way catalyst	2005	10,600
LPG A	LPG port fuel liquid injection passenger car	2.00	2013	three-way catalyst	2005	16,700
LPG B	LPG port fuel gas injection passenger car	1.60	2014	three-way catalyst	2005	18,300

Table 2. Combinations of experimental particle sizes and engine operations considered in this study.

Electrical mobility diameter [nm]	PSL	Diesel A (high idle)	Diesel A (high torque)	Diesel B 60 km/h	Diesel C 60 km/h	DISI A 20 km/h	DISI A 60 km/h	DISI B 60 km/h	PFI A 80 km/h	PFI B 80 km/h	LPG A 60 km/h	LPG B 60 km/h	Tunnel background
30	◎	◎	◎	◎	○^*	◎	◎	◎	◎	◎	◎	○^*	○^*
50	◎	◎	◎	◎	○^*	◎	◎	◎	◎	◎	◎	○^*	○^*
70	◎	◎	◎	◎	○^*	◎	◎	◎	◎	◎	×	○^*	○^*
100	◎	◎	◎	◎	○^*	◎	◎	◎	◎	◎	◎	○^*	○^*
200	◎	◎	◎	◎	−	◎	◎	◎	◎	−	−	−	−
300	◎	◎	◎	−	−	−	−	◎	−	−	−	−	−

^◎APM and TEM.

^○APM.

^×No experiment.

⁻No experiment because of low concentration.

* Experiment difficult to analyze because of low concentration.

Figure 1. Effective densities of particles. The results of the PSL particles are shown as raw data, and others were corrected using the PSL results. Values in parentheses are mass–mobility exponents calculated using Equation (3[3] ). Error bars indicate the standard deviations of multiple measurements.

Figure 2. Numbers of typical particle types as fractions of the total number of particles at various electrical mobility diameters. (a) Diesel A (high idle), (b) Diesel A (high torque), (c) Diesel B 60 km/h, (d) DISI A 20 km/h, (e) DISI A 60 km/h, (f) DISI B 60 km/h, (g) PFI A 80 km/h, (h) PFI B 80 km/h, (i) LPG A 60 km/h. N.M.: Not measured.

Figure 3. TEM images of typical particles with electrical mobility diameters D_m of 30 nm. (a) PSL particle, (b-1) Diesel A (high idle): Agglo, (b-2) Diesel A (high idle): Non-agglo-tra, (c) Diesel A (high torque): Agglo, (d) Diesel B 60 km/h: Agglo, (e) DISI A 20 km/h: Agglo, (f) DISI A 60 km/h: Agglo, (g-1) DISI B 60 km/h: Agglo, (g-2) DISI B 60 km/h: Non-agglo-opa, (h) PFI A 80 km/h: Non-agglo-opa, (i) PFI B 80 km/h: Non-agglo-tra, (j) LPG A 60 km/h: Non-agglo-opa. Scale bars with a length of 100 nm are included for reference. Agglo: Agglomerate electron-opaque particle, Non-agglo-opa: Non-agglomerate electron-opaque particle, and Non-agglo-tra: Non-agglomerate electron-transparent particle.

Figure 4. TEM images of typical particles with electrical mobility diameters D_m of 100 nm. (a) PSL particle, (b) Diesel A (high idle): Agglo, (c) Diesel A (high torque): Agglo, (d) Diesel B 60 km/h: Agglo, (e) DISI A 20 km/h: Agglo, (f) DISI A 60 km/h: Agglo, (g) DISI B 60km/h: Agglo, (h) PFI A 80 km/h: Non-agglomerate-tra, (i) PFI B 80 km/h: Non-agglomerate-tra, (j) LPG A 60 km/h: Non-agglomerate-tra. Scale bars with a length of 100 nm are included for reference. Agglo: Agglomerate electron-opaque particle, and Non-agglomerate-tra: Non-agglomerate electron-transparent particle.

Figure 5. Physical properties of agglomerates. (a) Average primary particle diameter d_p. (b) Average primary particle number N_p in a single agglomerate. Error bars indicate the standard deviations of the measured values for d_p and the propagation of error during each step of the calculation for N_p.

Table 3. Summary of plausible properties (average ± standard deviation) of agglomerates for Diesel A.

	Estimation from MOUDI, APM, and TEM results			Direct measurement by TEM
Electrical mobility diameter	Core diameter	Shell thickness	Primary particle diameter	Primary particle diameter
70	8.5 ± 2.7	5.1 ± 2.5	18.7 ± 4.4	20.8 ± 4.6
100	13.0 ± 4.2	7.4 ± 3.7	27.8 ± 6.7	28.5 ± 7.9
200	18.7 ± 5.0	6.8 ± 2.8	32.3 ± 6.4	33.2 ± 11.1
300	22.1 ± 2.6	6.3 ± 1.2	34.7 ± 3.0	36.7 ± 8.6

Units: [nm].

Standard deviations were obtained from the propagation of error during each step of the calculation.