Experimental Investigation on the Emissions of a Port Fuel Injection

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Experimental investigation on the emissions of a PFI SI engine fueled with methanol-gasoline blends Dongwei Yao, Xinchen Ling, and Feng Wu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b01586 • Publication Date (Web): 02 Aug 2016 Downloaded from http://pubs.acs.org on August 4, 2016

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Experimental investigation on the emissions of a PFI SI engine fueled with methanol-gasoline blends Dongwei Yao*, Xinchen Ling, Feng Wu Power Machinery & Vehicular Engineering Institute, College of Energy Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China Abstract: Methanol as an alternative fuel for vehicles has a broad prospect in China for its good combustion properties, low production cost and renewable ability, but the in-cylinder combustion of methanol also brings extra emission concerns, such as alcohols and aldehydes. To investigate the impact of methanol-gasoline blends on the pollutant emissions of spark ignition (SI) engines, a GEELY MR479Q port fuel injection (PFI) SI engine was selected for tests of burning different methanol-gasoline blends at wide-open throttle operating conditions, and an AVL fourier transform infrared (FTIR) multi-component gas analyzer was used to measure all the emissions. Test results show that the methanol contained fuel blends had positive effects on the engine-out regulated emissions. Nitrogen oxide (NOx), carbon monoxide (CO) and non-methane hydrocarbon (NMHC) emissions were all dramatically reduced when the test engine was fueled with methanol-gasoline blends. Other hydrocarbon emissions such as ethylene (C2H4), propylene (C3H6) and soot precursors like acetylene (C2H2) and aromatic hydrocarbons (AHC) were also reduced when with methanol-gasoline blends. However, the methanol in the fuel blends caused significant rises of engine-out unburned methanol (CH3OH) and formaldehyde (CH2O) emissions at the same time, especially for those high methanol contained fuel blends, such as M50 and M70. When fueled with M70, the engine-out unburned methanol (CH3OH) emission could reach as high as 500 ppm, and the formaldehyde (CH2O) emission was almost 4 times as much as M0. For other emissions like ethanol (C2H5OH), acetaldehyde (C2H4O), and 1, 3-butadiene (C4H6), only a slight influence of methanol on them was observed during the engine tests. Keywords: Spark ignition engine; Methanol-gasoline blend; Alternative fuel; Exhaust emission; Unregulated emission

1. Introduction The rapid development of automobile industry over the past hundred years has greatly exacerbated fossil oil crisis and exhaust gas pollution around the world. For this reason, various clean and renewable alternative fuels were proposed and gradually utilized on vehicles in the late 20th century. Among a wide range of alternative fuels considered globally, methanol has attracted enormous interests because of its low production cost, renewable ability and good combustion related properties1. Since *

To whom correspondence should be addressed. Email: dwyao@ zju.edu.cn

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1970s, many countries in Asia, Europe and America had actively promoted the utilization process of methanol on vehicles, and methanol-gasoline blends had been widely used for a long time. In China, there are abundant coal resources, and the technology of coal to methanol is perfect with low cost, methanol clean fuel from coal has become one of the most popular vehicle alternative fuels. Since 1980s when China started to develop methanol vehicles, methanol-gasoline blends as alternative fuels for vehicles have been now promoted over five provinces, including Shanxi, Shaanxi, Gansu, Guizhou and Shanghai. Numerous studies have been conducted to investigate the impact of burning primary methanol or methanol-gasoline blends on the performance of SI engines. Methanol has a lower heating value, but the oxygen atom in its molecule makes the complete combustion of methanol only need less air, thus the heating value of stoichiometric air-methanol mixture is almost equal to that of air-gasoline. Methanol also has a high latent heat of vaporization, which can cool the intake air and improve the volumetric efficiency. For these two reasons, the methanol-burning SI engines could have better power performance than gasoline2, 3. Higher latent heat of vaporization also results in the lower maximum in-cylinder combustion temperature, which helps to suppress the generation of thermal NOx under stoichiometric operations4-6. The higher octane number and oxygen containing hydroxyl group in molecule structure of methanol can also create higher engine combustion efficiency and reduce HC, CO and particulate matter (PM) emissions dramatically7-10. Therefore, the unique combustion properties of methanol result in higher thermal efficiency, higher engine power and lower regulated emissions. However, the in-cylinder combustion of methanol can also produce a considerable amount of extra toxic emissions such as alcohols and aldehydes11-13. Wei found that burning methanol-gasoline blends could lead to the rise of unburned methanol and formaldehyde emissions14, 15. Zhang investigated the unregulated emissions from a low-content methanol-gasoline SI engine and found that the engine-out methanol and formaldehyde increased almost linearly with the methanol content in the mixed fuel16. Unburned methanol is toxic and corrosive. It can poison the human nervous and blood systems. Formaldehyde has already been widely recognized as a strong carcinogenic and teratogenic substance, which has great adverse effects on the human health. With the wide promotion of methanol as an alternative fuel for vehicles and the growing emphasis on environment protections, the methanol induced unregulated emissions and their control on SI engines will become critical issues. Many previous studies have concerned the impact of burning primary methanol or methanol-gasoline blends on the emission performance of SI engines. However, most of them only focused on the changes of conventional or regulated emissions4-10. Some existing studies considering the methanol induced unregulated emissions also only concerned several species, such as unburned methanol and formaldehyde11-16. Actually, other hydroxyl, carbonyl and alkyl compounds, like ethanol, acetaldehyde, olefins, alkyne and aromatic hydrocarbons will also be more or less affected by the methanol in the mixed fuel, and most of them are harmful for humans as well. On the other hand, traditional measuring methods used in the previous studies for methanol


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induced unregulated emissions mainly include the gas chromatograph (GC) and the high performance liquid chromatography (HPLC), but both of them have the disadvantages of non-continuous measurement, slow measuring rate and limited measuring accuracy. Therefore, it is necessary to acquire a reliable measuring method with high accuracy and good repeatability for systematically and comprehensively evaluating all the regulated and unregulated emissions from methanol-gasoline SI engines. Thus the impact of methanol-gasoline blends on the pollutant emissions of SI engines can be fully understood. In this paper, a GEELY MR479Q 4-cylinder 4-stroke PFI SI engine was selected as the test engine for burning different methanol-gasoline blends at wide-open throttle operating conditions. An AVL FTIR multi-component gas analyzer with features of continuous fast sampling and high accuracy was used to measure all the engine-out emissions when with methanol-gasoline blends at each engine operating condition. Besides the regulated NOx, CO and NMHC emissions, the species measured during the engine tests also covered various unregulated emissions, such as alcohols, aldehydes, olefins, alkyne and aromatic hydrocarbons, and the latter two were considered as the important soot precursors. Test results and data analysis have been finally illustrated to clarify the impact of methanol-gasoline blends on the pollutant emissions of SI engines.

2. Experimental setup 2.1. Engine test bench All the engine tests were conducted on an engine test bench, which is shown in Figure 1. A GEELY MR479Q PFI SI engine was selected as the test engine for burning methanol-gasoline blends. A CWK-5 dynamometer was used to control the load of engine at wide-open throttle operating conditions. A linear oxygen sensor with an air-fuel ratio meter was amounted in the exhaust manifold to detect and maintain the in-cylinder mixture air-fuel ratio around the stoichiometric one. All the test signals, including engine torque, engine speed, fuel consumption, exhaust temperature and air-fuel ratio, were collected and transmitted to the host PC through a measurement and control system. Commands from host PC were also delivered to the test engine, fuel meter and dynamometer to change the engine operating condition. An AVL FTIR multi-component gas analyzer was adopted to measure all the engine-out emissions when the test engine was fueled with methanol-gasoline blends.


Air-fuel ratio meter

Exhaust temperature

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Figure 1. Schematic diagram of the engine test bench 2.2. Engine specifications The test engine MR479Q was a 4-cylinder 4-stroke multi-point PFI SI engine. It had a displacement of 1.342L, a compression ratio of 9.3 and a maximum power of 63.2kW at 6000r/min with gasoline. More detailed information about the test engine can be found in Table 1. During the engine bench tests for burning methanol-gasoline blends, no special retrofit was made to the engine except for the adjustment of cyclic fuel delivery to keep the in-cylinder mixture air-fuel ratio around the stoichiometric one for the consideration of emission control. Table 1. Specifications of the test engine (MR479Q) item value 4-cylinder, 4-stroke, engine type water-cooling, 16-valve group ignition, multi-point control type sequential port fuel injection cylinder bore 78.7 mm piston stroke 69.0 mm displacement 1.342 L compression ratio 9.3:1 maximum power 63.2 kW@6000 r/min maximum torque 109.8 Nm@5200 r/min 2.3 Fuel properties For the methanol-gasoline blends used in the engine tests, commercial 93# gasoline bought from local market was used as the base fuel, and industrial grade methanol with a purity of 99.9% was mixed with it in fractions of 0%, 10%, 20%, 30%, 50% and 70% by volume. Those six fuel blends were thus named as M0, M10, M20, M30, M50 and M70 respectively, and the number in each fuel blend represented their methanol contents. To prevent the problem of miscibility, methanol-gasoline blends


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were all temporally prepared before each engine test and no additives were used in the fuel blends. Their specifications could be derived from the published properties of gasoline and methanol17. For each fuel blend, the density was a function of its methanol volume fraction.

ρ f = γ (ρ m − ρ g ) + ρ g (1) where ρf, ρm and ρg were the densities of fuel blend, methanol and gasoline; γ, the methanol volume fraction. The low heating value of fuel blend also depended on its methanol volume fraction.

hf =

γ (hm ρ m − hg ρ g ) + hg ρ g (2) ρf

where hf, hm and hg were the low heating values of fuel blend, methanol and gasoline. Similarly, the stoichiometric air-fuel ratio of fuel blend could be derived as below.

ϕf =

γ (ϕ m ρ m − ϕ g ρ g ) + ϕ g ρ g (3) ρf

where φf, φm and φg were the stoichiometric air-fuel ratios of fuel blend, methanol and gasoline. Thus the mixture heating value under stoichiometric condition of fuel blend could be calculated as below. hfm =

hf (4) 1 + ϕf

where hfm represented the mixture heating value under stoichiometric condition of fuel blend. Table 2 shows the detailed specifications of methanol-gasoline blends used in the engine bench tests. Table 2. Specifications of methanol-gasoline blends fuel ρf hf φf hfm γ type (kg/L) (MJ/kg) (kg/kg) (MJ/kg) M0 0.0 0.725 44.00 14.8 2.785 M10 0.1 0.732 41.42 13.9 2.780 M20 0.2 0.739 38.89 13.0 2.775 M30 0.3 0.746 36.41 12.1 2.770 M50 0.5 0.760 31.58 10.5 2.756 M70 0.7 0.774 26.93 8.8 2.739

2.4. Emission measurement The emission measuring system applied in the engine test bench was an AVL FTIR multi-component gas analyzer. By using a wide range of wavelengths, AVL FTIR can simultaneously measure all the spectral information of the gas sample. With a lot of outstanding advantages, including continuous online measurement, synchronous multi-component analysis, high accuracy and high sampling frequency, AVL FTIR has been widely used in the present measuring of engine emissions. After being calibrated, AVL FTIR can simultaneously measure over 30 kinds of exhaust emissions with a


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sampling frequency of 1 Hz and a relative error of less than 1%. In this paper, with the help of AVL FTIR, all the raw engine-out regulated and unregulated emissions of the test engine were measured when it was fueled with methanol-gasoline blends at wide-open throttle operating conditions. The impact of methanol-gasoline blends on the pollutant emissions of SI engines was then analyzed and illustrated.

3. Effect of methanol on regulated emissions Regulated emissions of PFI SI engines mainly include nitrogen oxide (NOx), carbon monoxide (CO) and non-methane hydrocarbon (NMHC). Figure 2-Figure 4 illustrate the experimental results of regulated emissions, including NOx, CO and NMHC of the test engine when it was fueled with different methanol-gasoline blends at wide-open throttle operating conditions. For each kind of methanol-gasoline blend, totally five operating conditions with common engine speed from 1200 r/min to 2800 r/min were considered. 3.1. NOx emissions Figure 2 shows the NOx emissions of the test engine at different speeds and different methanol-gasoline blends. It is known that the higher in-cylinder temperature causes the higher thermal NOx emissions. With lower heating value and higher latent heat of vaporization, methanol does help to reduce the maximum in-cylinder combustion temperature when mixed into gasoline as a fuel blend. As such, with the rise of methanol content in the fuel blends, NOx emissions at all the engine speeds decrease dramatically, as shown in Figure 2. M50 and M70 have the most significant effects of NOx emission reduction. NOx emissions with these two fuel blends can be reduced as much as 29.3% and 54.5%. For each fuel blend, NOx emissions rise gradually with the increase of engine speed, because the in-cylinder combustion temperature gets higher as engine speed and power increase.

Figure 2. NOx emissions at different engine speeds and fuels 3.2. CO emissions Figure 3 shows the CO emissions of the test engine at different speeds and different


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methanol-gasoline blends. The generating mechanism of in-cylinder CO is relatively complex. Ideally, CO2 and H2O would be the only final products during the complete combustion of fuel blends. However, the real in-cylinder process is highly influenced by the inhomogeneous and turbulent mixture. In some rich areas inside of cylinders, CO will be generated due to incomplete combustion. From Figure 3, CO emissions at all the engine speeds decrease dramatically with the rise of methanol content in the fuel blends. With M50 and M70, the reduction of CO of the test engine can be up to 47.6% and 70.9%. According to the previous studies, the most important factors affecting CO formation include the fuel carbon content, flame propagation velocity and in-cylinder residence time18. Actually, the carbon mole fraction of fuel blends is reduced with the mixing of methanol, so the generating amount of CO in the flame propagation process decreases. Meanwhile, the flame propagation velocity of methanol is higher than gasoline, thus the methanol reduces the duration of fuel blends combustion, and less CO is produced in this period. Moreover, higher flame propagation velocity also results in longer in-cylinder residence time, which means the existing CO has more time to be oxidized in the high-temperature in-cylinder environment. As a result, CO emissions are significantly reduced as the test engine is fueled with methanol-gasoline blends. For each fuel blend, CO emissions rise gradually with the increase of engine speed, as shown in Figure 3. The main reason is the high engine speed reduces the mixture formation time and increases the proportion of inhomogeneous mixture in cylinders, and this leads to the increase of CO production.

Figure 3. CO emissions at different engine speeds and fuels 3.3. NMHC emissions Figure 4 shows the NMHC emissions of the test engine at different speeds and different methanol-gasoline blends. It is clear that NMHC emissions at all the engine speeds decrease dramatically with the rise of methanol content in the fuel blends. As the test engine is fueled with M50 and M70, the reduction of NMHC emissions can be as much as 48.5% and 79.9%. Actually, the NMHC emissions mainly come from the incomplete combustion of gasoline, thus the higher the mixing ratio of methanol and gasoline is, the lower the NMHC emissions become. On the other hand, the methanol molecular has oxygen containing hydroxyl group, so the methanol in the fuel blends


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in fact is helpful to promote the complete combustion of gasoline and reduce the NMHC emissions. For each fuel blend, NMHC emissions decrease gradually with the increase of engine speed, as shown in Figure 4. The main reason is that the in-cylinder combustion temperature gets higher as engine speed and power increase, and this actually strengthens the oxidation process of NMHC, thus making NMHC lower.

Figure 4. NMHC emissions at different engine speeds and fuels From the discussion above, as the rise of methanol content in the test fuel blends, all the regulated emissions including NOx, CO and NMHC decrease dramatically at each engine operating condition due to the good combustion properties of methanol in the fuel blends. When the test engine is fueled with low-content methanol-gasoline blends (M10, M20 and M30), the improvement of regulated emissions can be already up to 20% of pure gasoline. When with the middle-content and high-content (M50 and M70) methanol-gasoline blends, the effect of methanol-gasoline blends on the regulated emission improvement of test engine will become more significant. With M70, in some test engine operating conditions, the reduction of regulated emissions can be more than 50%.

4. Effect of methanol on unregulated emissions As discussed in previous sections, methanol-gasoline blends can dramatically reduce the regulated emissions of test engine. However, the combustion of methanol in the fuel blends, on the other hand, can produce a considerable amount of extra toxic emissions such as alcohols and aldehydes. In addition, methanol in the fuel blends also can affect the normal combustion process of gasoline, thus changing other special emissions originally existing in SI engines, such as olefins, alkyne and aromatic hydrocarbons (AHC). Acetylene (C2H2) in alkyne and AHC are the important soot precursors. Figure 5-Figure 10 show the experimental results of various unregulated emissions, including alcohols, aldehydes, olefins and soot precursors of the test engine when it was fueled with different methanol-gasoline blends at wide-open throttle operating conditions. For each kind of methanol-gasoline blend, totally five operating conditions with common engine speed from 1200 r/min to 2800 r/min were considered.


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4.1. Alcohols emissions Figure 5 shows the methanol emissions of the test engine at different engine speeds and different methanol-gasoline blends. Previous studies have showed that the methanol (CH3OH) could be produced from isooctane, hexane and methyl tertiary butyl ether (MTBE) in pure gasoline SI engines14, through recombination of CH3 and OH radicals or CH3O and H abstracted from HC/NMHC. However, in this paper, almost no CH3OH emissions were detected from the test engine when it was fueled with pure gasoline, as shown in Figure 5. But with the rise of methanol content in the fuel blends, CH3OH emissions increase rapidly. When the test engine is fueled with M70, the max CH3OH emission can be over 500 ppm. This result above indicates that the CH3OH emission mainly comes from the unburned methanol of fuel blends. Thus the higher the fraction of methanol in the fuel blends, the higher the CH3OH emission in the exhaust gas. For each fuel blend, CH3OH emissions decrease gradually with the increase of engine speed, as shown in Figure 5. The main reason is that the in-cylinder combustion temperature gets higher as engine speed and power increase and this accelerates the oxidation process of CH3OH.

Figure 5. CH3OH emissions at different engine speeds and fuels Besides CH3OH, ethanol (C2H5OH) emission was also measured in the engine tests. However, the emission level of C2H5OH at each engine speed and methanol-gasoline blend was all below 10 ppm. Therefore, it seems that almost no C2H5OH emission was generated in the combustion of pure gasoline and methanol-gasoline blends. 4.2. Aldehydes emissions Two kinds of aldehydes were measured in the engine tests, including formaldehyde (CH2O) and acetaldehyde (C2H4O). CH2O is an important intermediate product during in-cylinder combustion of either gasoline or methanol. It has attracted much attention because of its high toxicity, especially when methanol is used as an alternative fuel for vehicles. Figure 6 shows the CH2O emissions of the test engine at different engine speeds and different methanol-gasoline blends. As shown in Figure 6, CH2O emission originally exists in the pure gasoline SI engine and the emission level in this paper is about 50-80 ppm. It indicates that CH2O emission can be generated by the oxidation process of pure gasoline, especially those partial oxidation events of hydrocarbon components. But overall, the CH2O emissions of pure gasoline engine are relatively


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low. However, as the methanol is mixed in the gasoline, the CH2O emissions of the test engine at all the engine speeds increase dramatically. The larger the mixing ratio of methanol and gasoline is, the higher the CH2O emissions become. From Figure 6, when the test engine is fueled with M70, the CH2O emission is almost 4 times as much as that of pure gasoline. It is because the CH2O emission mainly originates from the further reactions of C1 radicals including CH3, CH3O and CH2OH14. Therefore, methanol, as a fuel of C1 level in the methanol-gasoline blends, accelerates the generation process of engine CH2O emissions. For each fuel blend, CH2O emissions rise gradually with the increase of engine speed, as shown in Figure 6. The main reason is the high engine speed increases the in-cylinder combustion temperature and accelerates the partial oxidation process of HC and CH3OH, as shown in Figure 4 and Figure 5, and this leads to the increase of CH2O production.

Figure 6. CH2O emissions at different engine speeds and fuels Another aldehyde, the C2H4O emission, was also measured in the engine tests. A slight rise of C2H4O emissions was observed with the increase of methanol content in the fuel blends. However, compared with CH2O emission, the C2H4O emission level of the test engine was always kept relatively low, about 20-35 ppm. Hence it seems that the methanol in the fuel blends only has little influence on the engine C2H4O emissions. 4.3. Olefins emissions Olefins are harmless to human health in most cases, but they can cause environmental problems such as water and soil pollutions. In this paper, three olefin emissions were measured in the tests when the engine was fueled with methanol-gasoline blends, including ethylene (C2H4), propylene (C3H6), and 1,3-butadiene (C4H6). C2H4 is a reactive volatile organic compound. It can easily react with NOx emissions in the presence of solar radiation and produce ozone. Ozone is an important factor for the formation of photochemical smog near the ground, which can threaten the human health seriously19, 20. Figure 7 shows the C2H4 emissions of the test engine at different engine speeds and different methanol-gasoline blends. With pure gasoline, the test engine has the highest level of C2H4 emissions, about 80-120 ppm in most cases. As the rise of methanol content in the fuel blends, the C2H4 emissions at all the engine speeds decrease dramatically. When the test engine is fueled with M70, the C2H4


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emissions are reduced to about 40-60 ppm, only 50% of M0. Like NMHC, the C2H4 emission also mainly comes from the incomplete combustion of gasoline, thus the high methanol contained fuel blends have lower C2H4 emissions. On the other hand, the methanol molecular has oxygen containing hydroxyl group, so the methanol in the fuel blends also promotes the complete combustion of gasoline and reduces the C2H4 emissions. However, unlike the NMHC emissions in Figure 4, for each fuel blend, C2H4 emissions rise gradually with the increase of engine speed, as shown in Figure 7. It is mainly because the olefins, including C2H4, C3H6 and C4H6 are usually the products or intermediate products of HC/NMHC oxidation process. Therefore, with the rise of engine speed, the in-cylinder combustion temperature gets higher, more HC/NMHC is oxidized and more C2H4 emission is produced.

Figure 7. C2H4 emissions at different engine speeds and fuels Figure 8 shows the C3H6 emissions of the test engine at different engine speeds and different methanol-gasoline blends. The generating mechanism for C3H6 emission is very similar to C2H4. Therefore, as shown in Figure 8, the C3H6 emissions at all the engine speeds reduce quickly with the rise of methanol content in the fuel blends. For the same kind of fuel blend, the C3H6 emission has a tendency of increasing with the rise of engine speed.

Figure 8. C3H6 emissions at different engine speeds and fuels The 1,3-butadiene (C4H6) emission was also measured in the engine tests. However, the emission level of C4H6 at each engine speed and methanol-gasoline blend was all below 10 ppm. Therefore, almost no C4H6 emission was generated in the combustion


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of pure gasoline and methanol-gasoline blends. 4.4. Soot precursors The soot emission from PFI SI engines is very low, but it still attracts much attention because of the increasingly stringent emission regulations. The detailed generating mechanism of soot during in-cylinder combustion is very complex, and it is still not thoroughly understood up to now. However, several reduced kinetic models for engine in-cylinder soot formation have been proposed and widely accepted. In general, soot formation process involves several steps, including nuclei inception, surface growth, aromatic coagulation and oxidation21. Among those steps, acetylene (C2H2) actually plays an important role in the nuclei inception step to form the first benzene ring. Meanwhile, aromatic hydrocarbons (AHC) are treated as the key components for the coagulation step of polycyclic aromatic hydrocarbons (PAHs). Therefore, C2H2 and AHC are usually considered as the most important soot precursors. In this paper, both of C2H2 and AHC were measured in the tests when the engine was fueled with methanol-gasoline blends. Figure 9 and Figure 10 show the C2H2 and AHC emissions of the test engine at different engine speeds and different methanol-gasoline blends respectively. As the increase of mixing ratio of methanol and gasoline, the mole fraction of hydrocarbons in the fuel blends decreases. Both of C2H2 and AHC come from the incomplete combustion of hydrocarbons, thus their emissions are all reduced with the rise of methanol content in the fuel blends, as shown in Figure 9 and Figure 10. Actually, during the engine in-cylinder combustion, C2H2 is mainly produced from those high C number hydrocarbons. C2H2 is also a reactive component that can easily be polymerized22. Thus the final C2H2 emission is in fact a dynamic balanced process between production and consumption. On the contrary, AHC emission mainly consists of unburned aromatic hydrocarbons in gasoline, so higher methanol content in the fuel blends results in lower AHC emission. On the other hand, the oxygen containing hydroxyl group in the methanol molecular also greatly promotes the complete combustion of gasoline and reduces the C2H2 and AHC emissions. For each fuel blend, both of C2H2 and AHC emissions decrease gradually with the increase of engine speed, as shown in Figure 9 and Figure 10. The main reason is that the in-cylinder combustion temperature gets higher as engine speed and power increase and this accelerates the oxidation process of C2H2 and AHC.


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Figure 9. C2H2 emissions at different engine speeds and fuels

Figure 10. AHC emissions at different engine speeds and fuels

5. Conclusions The worldwide fossil oil crisis and exhaust gas pollution make it urgent to search for clean and renewable alternative fuels for vehicles. Many countries including China have/had been actively promoting methanol/methanol-gasoline blends as vehicular alternative fuels for their low cost, renewability and many benefits on the engine performance. However, the in-cylinder combustion of methanol also brings extra emission concerns, such as alcohols and aldehydes. To comprehensively investigate the impact of burning methanol-gasoline blends on the engine-out pollutant emissions, a GEELY MR479Q PFI SI engine was selected for tests of burning different methanol-gasoline blends at wide-open throttle operating conditions. An AVL FTIR multi-component gas analyzer was used to measure all the engine-out emissions when with methanol-gasoline blends at each engine operating condition. Test results show that the methanol-gasoline blends had positive effects on the engine-out regulated emissions. NOx, CO and NMHC emissions were all reduced dramatically when the test engine was fueled with methanol-gasoline blends, and the reduction effect of regulated emissions became more apparent as the rise of methanol content in the fuel blends. When fueled with M70, the reductions of NOx, CO and NMHC emissions of the test engine could be as much as 54.5%, 70.9% and 79.9%


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respectively, comparing with pure gasoline. Other engine-out hydrocarbon emissions such as C2H4, C3H6 and soot precursors like C2H2, AHC were also reduced as the rise of methanol in the fuel blends. However, the methanol in the fuel blends also caused significant rises of engine-out CH3OH and CH2O emissions. When the engine was fueled with M70, the engine-out CH3OH emission could reach as high as 500 ppm, and the CH2O emission was almost 4 times as much as M0. For the rest emissions such as C2H5OH, C2H4O, and 1,3-butadiene (C4H6), only a slight influence of methanol on them was observed during the engine tests.

Acknowledgment The work described in this paper was conducted in the Engine Optimization Control Lab at Zhejiang University and financially supported by the National Natural Science Foundation of China (General Programs, Grant Nos. 50776078 and 51106136).

Nomenclature AHC FTIR GC HPLC MTBE NMHC PAHs PFI PM SI

Aromatic hydrocarbons Fourier transform infrared analyzer Gas chromatograph High performance liquid chromatography Methyl tertiary butyl ether Non-methane hydrocarbon Polycyclic aromatic hydrocarbons Port fuel injection Particulate matter Spark ignition

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Experimental Investigation on the Emissions of a Port Fuel Injection

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