VIETNAM JOURNAL OF CHEMISTRY VOL. 51(5) 576-583 OCTOBER 2013
SIZE DISTRIBUTION AND THE DENSITIES OF PARTICLES BY USING ELECTRICAL LOW PRESSURE IWIPACTOR IN FOUR-STROKE
MOTORCYCLES TAILPIPE
Dao Ngoc Nhiem'*, Duong Thi Lim^ Phung Dinh Ta''*
'institute of Materials Science. Vietnam Academy of Science and Technology
^Institute of Geography, Vietnam Academy of Science and Technology
^Department of Biological Engineering and Environmental Sciences. National Tsing Hua University, Hsinchu, Taiwan 30013, R O. C
''Technical Materials and Resources Import-Export Joint Stock Company Received 3 June 2013
Abstract
The electrical low pressure impactor (ELPl) is usefiil tool for momtonng size distribution of particles and collecting them from exhaust of four-stroke motorcycle. Two kinds of gasoline A-92 and A-95, the most popular gasoline in Taiwan were used in this study. The particle size distributions were under real condition m the tailpipe exhaust of four- stroke motorcycle using the cold start condition. Almost of them are unimodal distnbutions at 28 ran. The higher octane ratio of gasoline is used, the more particle numbers is emitted. The efrective densities are estimated and changed with speeds and gasoline. They are more than 1 g/cm^ at 28 nm aerodynamic diameters and reduce gradual linear when the particle aerodynamic diameter increases.
Keywords: Electrical low pressure impactor (ELPI); particle size distributions; gasoline A-92 and A-95; exhaust of four stroke motorcycle's tailpipe.
1. INTRODUCTION
Transportation is a basic necessity of daily life.
Among all types of fransport action tools, motorcycle vehicles have the deepest influence on the way of fraveling around and are the most important fransportation means for many countries for example Asia countries such as Taiwan, Thailand, Vietnam and Europe such as Italy, Germany,,.. The motorcycle industrial development in Taiwan is increased (Her,2007), Total motorcycles estimated to 2005 were over 12 milhons of motorcycle registered m Taiwan which has the highest motorcycle precipitant density (two persons per motorcycle) in the world. According Taiwan's motorcycle production the number of motorcycle is expected to increase in the future. The fiiel demand especially gasoline will be increased. The increasing use of gasoline with low sulfur is a response to increasingly stringent emission standards developed because conventional gasoline motorcycle have been linked to serious adverse health effects. Heightened awareness of potential particle matter (pm) health
effects has led to the tightening of ambient air quality standards the current public debate on air biome particle matter is driven by the results of epidemiological studies which show correlation of the occurrence of ambient pm and adverse health effects (Veda!, 1997 and Dockery et al., 1994) with an aerodynamic diameter smaller than 2.5 mm (pm 2.5). Atkinson et al. (2001) on the Air pollution and Health: a European Approach (APHEA) two project investigated short-term health effects of pm 10 particles and black smoke and daily coimts of emergency hospital admissions for asthma (0-14 and 15-64 year), chronic obstructive pulmonary disease and all respiratory disease (65 year) confrolling for environmental factor and temporal difference of ulfra fine particles smaller than 0.1 pm of daily mortality was respected to associated health effects (which Mann et al (2000). Debate continues over the extent to which confounding pollutant emission from motorcycles is a major issue in improving air quality in Taiwan. Most motorcycles are light duty with displacement of 50-150cc.
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The objectives of this paper are to study particle distributions and the effective densities of particles collected from four-sfroke motorcycle with metal catalyst applied by using electrical low pressure impactor (ELPI) two kinds of unleaded gasolme A- 92 and A95 from commercial fiiel from Chinese pefroleum company Taiwan, are used four speeds idle, 30 km/h, 50 km/h and 70 km/h conditions of motorcycle are tested. The experiment coefficient values of variation are presented in the case of this motorcycle.
2. ELPI TECHNIQUE
The ELPI 4.0 combines aerodynamic size classification with the electrical detection of parfrcles with 13 stages in the 50% cut size diameter 0.028; 0.055; 0.92; 0.16; 0.26; 0.38; 0.61; 0.95; 1.6;
2.4; 4.0; 6.63; 9.93 pm and filter stage that can collect particle size with 7 nm of 50% cut size diameter. The test aerosol first undergoes unipolar charging in a diode type corona discharge and the passes through a Brermer low pressure cascade impactor to separate particles of different aerodynamic size. Elecfrometers record current deposited on each impactor stage at a rate up 1 Hz.
The provide raw date from the ELPI in the from electncal current versus aerodynamic diameter versus time (ELPI is used some reasons following:
corrections are needed to account for diffusion and elecfrostatic particle losses in the charger and cascade impact or and an algorithm is required to convert the raw current distnbution to the desired information such as a number or mass distnbution) Keskinen et al. (1992) and Marjamaki et al. (2000) provided a detailed description of this instrument and its operation and evaluated the performance of ELPI at a nominal flow rate of 10 l/min. Shi et. al.
(1999) used ELPI to study the number and distribution of particles emitted from a diesel engine and investigated the similar results of particle emissions at using ELPI and scanning mobility particle size (SMPS). Marjamaki et. al (2000) gave that the curves of ELPI are in fact not too shallow in the present configuration and the agreement with the SMPS measurement is reasonably good. Marieq et al. (2000) compared particle disfribution of three diesel and three gasoline vehicles operating in steady states and on the federal. Test procedure (FTP) by using SMPS and ELPI and gave the steady particle size dishibutions are in close agreement except for the 37 nm impactor stage for the ELPI. Tsukamoto et al. (2000) used ELPI to measure diesel particulate mass and size distnbution, together with time series behaviors under vanous driving patterns. Jeong
Dao Ngoc Nhiem, et al.
(2002) used ELPI with two sample dilution ratios 8.6:1 and 78:1 at idle speed, tested and dilution temperatiore and identified that the number of particles were measured 50% less in a two-stage dilutes system (78 ratio) than in single-stage dilutes system (86 ratio) and 20%. of particles in the size range of 20-300 nm was reduced by heating the dilution air from 25°C to 200°C.
However, van Gulijk. et al. (2001, 2003) reported that some of disadvantage of ELPI behavior are particle bounce, wall or interstate loss, overloading or surface hail up and losses due to elecfrostatic - effects and to charger non ideal efficiency.
Van Gulijk. et al. (2004) gave an underestimation of the apparent size of particles of ELPI due to their fractal-like structure and over estimates the diameter of particles because the mobility diameter of a fractal-like particle is larger than the aerodynamic diameter of that same particle.
3. EXPERIMENT SECTION
The four-sfroke motorcycle with two kinds of gasoline A-92 and A-95 respectively were used for this study. The main characteristics of the motorcycle were shown on table 1.
Table 1: Main charactenstics of motorcycle
Type Transmission Maximum speed
Net weight Cumulative mileage
125cc-4sfrokeair cooled Automatic (CVT)
65 mph 105 kg 1600 km The gasoline's contained 180 ppm of sulfur content while fuel combustion, contained in fuel may increase the emission of fly. The characteristics of two kinds of gasoline are presented in table 2.
The tests were performed on cold start with four constant speeds such as idle 30, so and 70 km/h at ambient condition 30°C from 40 rmn to one hour and kept 15 minutes for motorcycle warming very cycle agent 3 times experiment speeds were measured by using the speeds on the clock of the motorcycle by dnving motorcycle on the road and making the mark of each speed. Aluminum foil filter purchased from pall corporation without grease oil on surface were used for all stage of ELPI, and the electrometer range setting was 40000 FA, Data were recorded using the "AVERAGA" option in the ELPI 40 software during 5 seconds. The EPLI software
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algorithms automatically report negative measured currents as 0 particles/cm^. Therefore, instrument zeroing is critical for computing accurate particle number concenfrations from the measured current data, hi this sttidy, all ELPI stage were zeroed at measurement range 40000 FA before the beginning of each sampling day using the "ZEROING"
command and the ELPI fiish pump.
The experiment setup is presented by figure 1.
The diluter was directly cotmected to the tailpipe with 10 cm stainless steel line and 2 mm mner
Size distribution and the densities of...
diameter. To quantify ELPI noise level dilution air with ambient temperature used to dilute tailpipe exhaust was dried by silica and cleaned with HEPA filter. Dekati diluter with dilution ratio about 8.6 was used to dilute the exhaust gas before sample was passed through Electrical low pressure Impactor (ELPI) with capacity 10 liters/min. The exhaust gas temperature was around 32°C after dilution. In this exhaust of motorcycle by using A-92 and A-95 gasoline are called PA-92 and PA-95 respectively.
Table 2: Main characteristics of gasoline
Items Density at 15°C,g/ml
Octane No Color Reid vapor pressure at 37.8''C,
Kpa Corrosion copper strip 3 hrs at
50°C Oxidation stability, induction
period, minutes Oxygen content, wt % Benzene content, vol.%
Sulfur content, ppm w/w Lead content, gpl/1 Distillation temperature, °C
- 10% vol.% evaporated - 50% vol.% evaporated - 90% vol.% evaporated
- End point Dishllation residue, vol.%
MTBE, vol.%
Min
Max
Max Mm Max Max Max Max
Max Max Max Max Max Max
A-92 Report
92 Blue 61.3
No.l 240 2 1 180 0 013
70 121 190 225 2 11
A-95 Report 95 Yellow
61.3
No.l 240 2 1 180 0.013
70 121 190 225 2 11
Test method 12017 CNS 12011
CNS Visual 12012 CNS 219 CNS
12014 CNS 14297 CNS 14561 CNS 12376 CNS 12013
CNS 1218 CNS
D 1298 ATSM D 2699 ASTM
visual D 232 ASTM
D 130 ASTM D 525 ATSM D 4815 ATSM D 3606 ATSM D 1266 ATSM D 3237 ATSM D 86 ATSM
12614 CNS 1 The coefficient of variation (COV) is estimated
by the equation:
V = 1 0 0 . S
X
Where: Sx is standard deviation estimated by
jV_jZ.,.iV. I J
N Where: N is number of measurements.
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Figure 1: Expenment setup
4. RESULTS AND DISCUSSION 4.L Repeatability of measurements
Variation of particle emissions during acceleration to investigate emission of particle numbers during accelerating speed of the motorcycle from idle to 30 km/h, from 30 km/h to 50 km/h and from 50 km/h to 70 km/h, the number concentrations of particles at four speeds are compared by talking the mean of particulate concenfrations dunng the 5 minute at beginning of each measurement. Figure 2 shows that the total number concenfration of particles (with particles sizes from 7 nm to 6.63 nm) would increase with speeding motorcycle from idle to what by using gasoline. However, the total numbers of particles with particles size from 7 nm to 6.63 nm were not changed at idle and 30 km/h using
Dao Ngoc Nhiem, et al.
gasoline. They increased from 30 km/h to 50 km/h after that number particle reduced at 70 km/h. Vogt.
et al. (2003) identified that the sfronger increase of total particle number concenfration is an indication for the occurrence nucleation particles. Dunng acceleration, the afr-to-fiiel ratio is decreased and the exhaust contains a larger amount of hydrocarbon from unbumed fuel. This volatile material can either condense on exiting particles this increase the volatile orgamc faction or from new particles.
Therefore, the higher speed of motorcycle by using A-95 is, the more particulates are emitted. The higher octane rating correlates to higher activation energies. Activation energy is the moimt of energy necessary to start a chemical reaction. Octane rating has no direct impact on the deflagration (bum) of the air/fuel mixture in the combustion chamber.
Detonation is a different type of combustion and this IS to be avoided in spark ignited gasoline engines.
Octane rating is a measure of detonation resistance.
Using a fuel with higher octane lets an engine run at a higher compression without having problems with knock. Actual compression in the combustion chamber is determined by compression ratio as well as the amount of air restriction in the engine is producing its maximum power. Therefore, the yield of combustion of A-92 gasoline is more completed than A-95 at 70 km/h and created smaller unbumed particle than at the same speed and compared with 50 km/h with the same fuel.
900 1200 Time (seconds)
Figure 2: Particle number variation with speed (1) at idle, (2) at 30 km/h, (3) at 50 km/h and (4) at 70 km/h
4.2. Measurement of particle size distribution gasoline A-92 and A-95. All of them are in nucleation mode with peak at 28 nm. At idle, 30, 50 The number particle distributions measured with and 70 km/h, unimodal size distribution was observed 4-sfroke motorcycle were shown on figure 3(a, b, c, from 7 nm to 93 nm which are typical for soot mode d) for speeds at idle, 30, 50 and 70 km/h with kinds of particles. All soot particle sizes concenfrated at 28
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nm. These distributions are quite similar for the four speeds. The higher velocity is the bigger particle number at 28 nm was emitted. Total number concentration of PA.95 higher than that of PA.92-
Estimation of the effective densities of particle size Kittelson (1998) identified that the particle of ignition engines consist mainly of highly agglomerated solid carbonaceous material and ash and volatile organic and sulfur compounds. Andrew et al. (2001) used ELPI to estimate the particle effective density as a fimction of size to 1.5-2.0 gJcTci in passenger car with diesel and concluded that the estimated mass can be very important for particles bigger than 1 mm. Virtanen et al. (2002) estimated the particle effective density to 1.1-1.2 g/cm^ of diesel as a function of their size. Lervas et al. (2006) employed ELPI to measure the particles number and size disfribution of exhaust gas of Euro passenger car and calculated the mitial density values of 1-7 ELPI stages about 0.62 g/cm^. Shi et al. (1999) and Tsukamoto et al. (2000) gave an average density of 1.0 g/m^ or Witze et al. (2004) was 0.5 g/cm^ The density decreases with the
Size distribution and the densities of...
particle size because the smaller size particle are more spherical and consequently have higher density, while the bigger particle are aggregates of small particle and this have more intemal emp^
space. Ahlvik et al. gave particle density depending linearly on size (1.2 g/cm' at the first ELPI stage and 0.1 g/cm^ at the 12"^). Witze et al. (2004) estimated the particle density values of 1.2 g/m^ to 0.3 g/m^
Marieq et al. revealed a sharp decline in soot effective density from 1.2 g/m^ at 30 nm to 0.3 g/cm^ at 300 nm and the effective measurements made for steady - state vehicle operation from 20 to 70 km/h is independent of vehicle speed. Andrew et al. (2001) suggested values of 1.5-0.2 g/cm^ or Virtanen et al. (2002) about 1.1-1.2 g/cm^ Witze (2004) compared simultaneous SMPS and ELPI measurement of consistent with the averaged measured effective density of 0.85-0.91 g/cm\ Shi et al. (1999) found that ELPI and SMPS predict 1.3-1.6 times more mass than this collected on fitness.
Khalek (2000) concluded that ELPI overestimates the total mass emissions comparing to filter mass measurements when using for heavy duty engine.
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Figure 3: (a) Number particle distnbution at idle speed; (b) Number particle distnbution at 30 km/h;
(c) Number particle distribution at 50 km/h; (d) Number particle distribution at 70 km/h
VJC, Vol. 51(5). 2013
To estimate the effective density of each stage from ELPI, some assumptions are used: The particle collected on each stage are spheres, the effective density is estimated by die equation:
m, = N , V,.P,
Where N, is the number particle on each filter stage, m f is particle mass on each filter stage measured by balancing on balance with exact 0.01 mg, V,. is the volume of sphere particles on each filter stage estimated by mean diameter of each ELPI stage (defined as D,- = (jD^D^ ) where D„ and D^ are the lower and upper diameters of each EPLI) and P, IS the effective density of each EPLI stage. We only
Dao Ngoc Nhiem, et al.
estimated the effective densities of 8 stage of ELPI because the particle masses of 9 to 11 stage were small. The particle masses collected by EPLI were measured, estimated by mg/cm^ performed by figure 4. The effective densities were changed with the sizes of particle from 1.6 to 0.13 g/cm^ shown by figure 5. This result is similar with Ahlvik et al.
(1998) and (2004), The best fit Lines y = ax + b and the coefficient of determmation r^ of the estimated versus measured values are calculated for each diameter. Table presents the values of a, b and r^ for these configurations. The effective densities of PA-9I are bigger than those of PA-9S when the motorcycle were at the meantime motorcycle at higher speed would exhaust larger effective densities of particle and 70 km/h. This is resulted by hydrocarbon soot created by nucleation and the engine combustion that it is no completed.
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Figure 5: The effective densities of 8 stages of ELPI estimated with speeds 50 km/h and 70 km/h with two kinds of gasoline A-92 and A-95
The coefficients of variation of particle mass 50 k m * of A-92, 6-16% for 70 kmA of A-95 and 6 dunng measurements. The coefficients of variation -15% for 70 km/h of A-92.
fluctuated 2.4-10% for 50 km/h of A-95, 8-17% for
VJC, Vol. 51(5), 2 0 1 3 Size distribution and the densities of...
Table 3: T h e a, b a n d r^ o f the b e s t fit lines y = ax + b of t h e e s t i m a t e d v e r s u s effective density Items
50 km/h with A-92 50 km/h with A-95 70 km/h with A-92 70 km/h with A-95
a -0.15 -0.14 -0.14 -0.2
b 1.6 1.3 1.7 1,7
,>
0.99 0.95 0.97 0.97 4. C O N C L U S I O N S
T h e four-sfroke m o t o r c y c l e u s m g t w o k i n d s of gasoline A - 9 2 a n d A - 9 5 w a s tested at cold start condition. T h e result of this study w a s s h o w n the following.
T h e coefficients of v a n a t i o n particle n u m b e r for filter stage a n d 11 E L P I stages c h a n g e d from 4 % to 173% at four speeds s u c h as idle, 3 0 km/h, 50 km/h, 70 km/h b y using t w o k i n d s of gasoline A - 9 2 a n d A - 9 5 .
T h e total n u m b e r concenfration of PA.95 to ambient increased with s p e e d i n g t h e motorcycle from idle to 70 k m / h . N u m b e r concenfration of PA-92 increase when changing s p e e d from 3 0 k m / h to 50 km/h and decrease w h e n accelerating from 5 0 k m / h to 70 km/h.
T h e number particle distribution of all speeds is unimodal from 7 n m to 55 n m .
T h e effective densities of eight E L P I stages are 1.1-0.13 g/cm^. T h e y r e d u c e d n e a r linear w h e n the particle sizes increase. T h e effective densities of PA-92 are higher than those o f PA-95 w i t h the s a m e speed.
T h e coefficients of v a n a t i o n o f particle m a s s measured on filter stage e s t i m a t e d b y mg/cm^ are estimated and changed 2.4—17%.
R E F E R E N C E S
1. P. Ahlvik, L. Ntziachristos, J. Keskinen and A.
Virtanen. Real time measurements of diesel particle size distribution with an electrical low pressure impact or, SAE Technical Paper, 980410 (1998).
2. M. Marjamaki, J. Keskinen, D. R, Chen and D. Y. H.
Pui. Performance Evaluation of the Electrical Low- Pressure Impactor (ELPI), Journal of Aerosol Science, 31(2), 249-261 (2000),
3, A. Virtanen, M. Maijamaki, J. Ristimaki, J.
Keskinen. Fine particle losses in electrical low- pressure impactor, Joumal of Aerosol Science, 32, 389-401(2001)
4, M. Marjamaki. Electrical Low Pressure Impactor:
Modifications and Particle Collection
Characteristics, PhD thesis, T a n p e r e University of Technology Publications, 449 (2003).
5. K. Patlas, N . Kyriakis, Z. Samaras, P. Pistikopoulos, L. Ntziachnstos. Effect of DPF on Particulate Size Distribution using an Electrical Low Pressure Impactor, SAE Technical paper series 980544 (1998).
6. Y. Tsukamoto, Y. Goto and M. Odaka. Continuous Measurement of Diesel Particulate Emissions by an Electrical Low-Pressure Impactor, SAE Technical paper senes 2000-01-1138 (2000).
7. A. R. Khalek. Characterization of Particle Size Distribution of a Heavy-Duty Diesel Engine during FTP Transient Cycle Using ELPI, SAE Technical paper series 2000-01-2001 (2000).
8. M. Mancq, D. Podsiadlik, R. Chase. Size Distributions of Motor Vehicle Exhaust PM: A Comparison between ELPI and SMPS Measurements, Aerosol Science and Technology, 33, 239-260 (2000).
9. A. Virtanen, J. Ristimaki, M. Marjamaki, K. K, J.
Vaaraslahti. Effective density of Diesel Exhaust Particles as a Function of Size, SAE Technical paper series 2002-01-0056 (2002).
10. P. O. Witze, R. E. Chase, M. M. Marieq, D. H.
Podsiadlik, N Xu. Time. Resolved Measurements of Exhaust PMfor FTP-75: Comparison of LU. ELPI.
and TEOM Techniques, SAE Technical Paper Senes 2004-01-0964(2004).
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12. r. Gouriou, J. P. Morm & M. E. Weill On-road measurements of particle number concentrations and size distributions in urban and tunnel environments, Atmospheric Environment, 38, 2831-2840 (2004).
13. W. Glover & H. K. Chan. Electrostatic charge characterization of pharmaceutical aerosols using electrical low-pressure impaction (ELPI), Journal of Aerosol Science, 3 5 , 755-764 (2004).
14. P. Kwok, R. Collins, H. K. Chan. Effect of spacers on the electrostatic properties of metered dose inhalers, Joumal of Aerosol Science, 37,1671-1682 (2006).
15. J, Maijala, J. P. Keitamo, J. Gron & L. Kettunen.
Modeling and simulation of the electric field and
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particle trajectories in simultaneous two-sided dry surface treatment of paper. Surface & Coatmgs Technology, 195, 41-53 (2005).
16. S. C. Heradon, T. B. Onasch, B. P. Frank, L. C. Mair,
Dao Ngoc Nhiem, et ai 3. T. Jayne, M. R- Canagaratna, J. Grygas, T. Lanni, B. Anderson, D. Workshop & R. C. Miake-Lye.
Particulate Emissions from in-use Commercial Aircraft, Aerosol Science and Technology, 39, 799- 809 (2005).
Corresponding author: Dao Ngoc Nhiem Institute of Materials Science,
Vietnam Academy of Science and Technology 18 Hoang Quoc Viet, Cau Giay, Hanoi E-mail: [email protected].
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