Experimental study on mechanical filtration through tobacco columns: Influence of cut-filler shape and size distribution on filtration efficiencies

Figures & data

Figure 1. A scanned image of the cut-filler shape and size in a tobacco column used in this study. The cut-fillers were scanned by a printer (Hewlett Packard, Palo Alto, CA, USA, C5280) and analyzed by an image processing software (MathWorks Inc., Natick, MA, USA, Matlab).

Table 1. The physical properties of sample cigarettes.

Sample name	Net tobacco weight (g/cigarette)	Packing density (−)	Apparent density (g/cm^3)	Column length (mm)	Circumference (mm)
Commercial brand A	0.475	0.394	0.437	57.0	24.9
Commercial brand B	0.665	0.384	0.605	59.0	24.9
Commercial brand C	0.700	0.373	0.658	59.0	24.9
Commercial brand D	0.655	0.391	0.587	59.0	24.9
Commercial brand E	0.530	0.421	0.457	57.0	24.9
Commercial brand F	0.780	0.360	0.759	59.0	24.9

Figure 2. Experimental diagram of the measurement for particle filtration efficiency.

Figure 3. Schematic drawings of the measurement for filtration efficiency during burning.

Figure 4. Comparison results between the PSL logarithmic penetration ratio and the smoke components logarithmic penetration ratio.

Figure 5. The actual filtration efficiency and the predicted filtration efficiency of each reference through a tobacco column. (a) Flow velocity vs. filtration efficiency (PSL: 200 nm) and (b) PSL particle size vs. filtration efficiency (flow volume: 1.05 L/min).

Table 2. The dominant collection mechanisms under the experimental conditions.

	Particle diameter (nm)
Flow volume (L/min)	55	101	202	300	402	505	602
0.40	D	D	D	D	D + R	D + R	D + R
0.60	D	D	D	D + R	D + R	D + R	D + R
0.80	D	D	D	D + R	D + R	D + R	D + R
1.05	D	D	D + R	D + R	D + R	D + R	I + R
1.30	D	D	D + R	D + R	D + R	R	I + R
1.65	D	D	D + R	D + R	R	R	I + R
2.00	D	D	D + R	R	R	I + R	I + R
2.50	D	D	D + R	R	I + R	I + R	I + R

Note. D: Diffusion, R: Interception, I: Inertia.

Figure 6. Comparison results between the experimental filtration efficiency and the predicted filtration efficiency calculated by the modified equations. (a) Flow velocity vs. filtration efficiency (PSL: 200 nm) and (b) PSL particle size vs. filtration efficiency (flow volume: 1.05 L/min).

Table 3. The shape-size factor and the distribution factor determined through each of the measurements.

	Pressure drop measurement		Sieve measurement
	Takahashi modified		Ergun	Air volume (L/min)								Weight basis	Defined by this study
Sample name	DG(μm)	Shape-size factor(−)	DG(μm)	0.40	0.60	0.80	1.05	1.30	1.65	2.00	2.50	Ave. granule size(mm)	Distribution factor(−)
				Pressure drop (Pa/tobacco column)
Commercial brand A	821	6.79	653	186	304	441	618	843	1167	1559	2295	2.14	5.13
Commercial brand B	810	7.98	548	216	333	490	667	902	1255	1687	2618	2.24	4.86
Commercial brand C	675	4.73	612	157	235	353	481	657	912	1216	1755	2.07	5.14
Commercial brand D	821	6.37	613	177	275	402	559	755	1069	1412	2128	2.04	4.93
Commercial brand E	808	5.71	668	196	340	493	696	925	1278	1265	2442	2.17	4.64
Commercial brand F	791	9.58	501	216	333	490	667	892	1265	1677	2667	1.85	4.38

Note. Average granule size means mass median diameter that was calculated by the relationship between log-minus sieve size and normal standard cumulative distribution function (NORMSINV). Average granule size is the value of sieve size that corresponds to NORMSINV (0.5).

Figure 7. Experimental results of sieve measurements with the commercial brands. (a) Weight frequency of log-normal size distribution and (b) inverse standard normal cumulative distribution (NORMSINV) vs. log minus sieve size.

Figure 8. Relationships between the filtration efficiency under the condition of PSL: 200 nm and flow volume: 1.05 L/min and (a) the shape-size factor, (b) the distribution factor, and (c) the average granule size.

Figure 9. Relationships between the filtration efficiency under the condition of PSL: 200 nm and flow volume: 1.65 L/min and (a) the shape-size factor, (b) the distribution factor, and (c) the average granule size.

Figure 10. Comparison results of the filtration efficiency during burning with commercial product A under three types of smoking conditions.

Figure 11. Comparison results of filtration efficiency during burning with commercial products under the condition of ISO. (a) Predicted without the shape-size factor and (b) predicted with the shape-size factor.