Fuel 218 (2018) 266–274
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Full Length Article
Reducing volatile organic compound emissions from diesel engines using canola oil biodiesel fuel and blends Jun Cong Gea, Ho Young Kima, Sam Ki Yoonb, Nag Jung Choia, a b
T
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Division of Mechanical Design Engineering, Chonbuk National University, 567 Baekje-daero, Jeonjusi 561-756, Jeollabuk-do, South Korea Technical Education Center, GM Korea Company, 72 Saengmuol-ro, Gunsansi 573-882, Jeollabuk-do, South Korea
A R T I C L E I N F O
A B S T R A C T
Keywords: Canola oil biodiesel fuel Alternative fuel Volatile organic compounds Diesel engines Gas chromatography/mass spectrometry
Volatile organic compounds (VOCs), a group of environmental pollutants, are emitted in large quantities when fossil fuel is burned in automobiles. This research investigates the VOCs in the exhaust emissions from a common rail diesel engine fueled with canola oil biodiesel fuel (COBF), conventional diesel fuel (CDF), and B20 (20% COBF blended with 80% CDF by volume) at various engine loads (30 Nm, 80 Nm, 130 Nm) and a constant engine speed of 1500 rpm. The results indicate that the regulated emissions (CO, HC, PM) were reduced obviously when COBF and B20 were used in a CRDI diesel engine, and a larger number of VOCs (about 30 types) are emitted with CDF and the quantity emitted is greater than with B20 and COBF. The total VOC emissions (TVOC) of B20 were lower than those with the other test fuels at all experimental conditions. In addition, this paper presents a simple approach for sampling VOC emissions from diesel engines, uses a gas chromatography/mass spectrometry (GC/ MS) analysis, and also confirms that COBF blended with CDF in a volume fraction of 20–80 is an excellent alternative fuel based on VOC emissions.
1. Introduction Volatile organic compounds (VOCs) are harmful air pollutants that pose a serious threat to human health and negatively impact the environment. VOC sources are divided into indoor and outdoor [1,2]. Indoor sources include building materials [3], painting materials [4], packaging materials [5], and furniture items [6]. Outdoor sources include combustion of fossil fuels [7], vehicle exhaust [8–11], and industrial exhaust [12,13]. Overexposure to VOC in humans can produce dizziness, nausea, vomiting, weakness of limbs, and other symptoms of discomfort. Prolonged exposure to VOCs can lead to kidney failure, cancer, and death [14–16]. In addition, with sufficient illumination, a photochemical reaction between VOCs and NOx produces ozone, which also threatens human health as well as that of animals and plants [17]. Therefore, reducing the VOC content in the air is a particularly important topic in the field of environmental protection research. Currently, there are two main ways to reduce VOCs in the air, and these, like diesel engine exhaust emissions, can be divided into “posttreatments” and “pre-treatments.” The “post-treatment” technique involves adsorbing or decomposing VOCs using some sort of adsorbent material [18–20]. As nanocomposite technology has developed, a variety of nanocomposite adsorption materials for air purification [21–23] have been developed. Some researchers have used
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electrospinning technology to synthesize nanocomposite films [24–26] that offer good VOC adsorption from air. For example, Kim et al. [25] succeeded in combining fly ash (FA) powder with polyurethane (PU) using electrospinning technology. They reported that PU with 30 wt% FA can adsorb about 35 µg of benzene and 40 µg of toluene per gram of fiber. Celebioglu et al. [27] reported that hydroxypropyl-beta-cyclodextrin and hydroxypropyl-gamma-cyclodextrin electrospun nanofibers have high adsorption capability for the VOCs aniline and benzene. Nanofibers produced by electrospinning technology have higher surface area than the same materials in powder form. Many materials can adsorb VOCs, such as activated carbon [28], activated carbon nanofiber material [29], cyclodextrin polymers [30], and titanium dioxide [31]. However, despite the many modern materials [32,33] that can adsorb VOCs, associated treatments merely reduce VOCs after they have been emitted; they cannot solve the problem at the source. Pre-treatment techniques, such as biodiesel fuels, can reduce the amount of VOCs emitted into the air by fossil-fuel combustion applications [34,35]. Biodiesel fuels, an alternative to fossil fuels, can be produced from vegetable oils or animal fats and have the unique advantages of being non-toxic, harmless, recyclable, environmentally friendly, and biodegradable [36,37]. Fig. 1 compares the exhaust emissions of fossil fuels and biodiesel fuels. Since the 1890s, when Rudolph Diesel first discovered that vegetable oil could be used in diesel engines, the study of
Corresponding author. E-mail addresses:
[email protected] (J.C. Ge),
[email protected] (H.Y. Kim),
[email protected] (S.K. Yoon),
[email protected] (N.J. Choi).
https://doi.org/10.1016/j.fuel.2018.01.045 Received 11 October 2017; Received in revised form 9 January 2018; Accepted 12 January 2018 Available online 30 January 2018 0016-2361/ © 2018 Elsevier Ltd. All rights reserved.
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Fig. 1. Exhaust emissions comparison between fossil fuels and biodiesel fuels.
biodiesel fuels has been ongoing [38–40]. Many researchers have demonstrated that biodiesel fuels can be applied directly to unmodified diesel engines [41,42]. However, unmodified diesel engines cannot operate long-term on pure biodiesel fuels because their high density and viscosity erode the engine’s rubber rings and tubing, clog nozzles, and increase carbon deposition. Therefore, biodiesel has to be blended with conventional diesel fuel [43–45]. At present, the research on VOC emissions from a diesel engine fueled with biodiesel fuel is inadequate. In this study, the emissions of 15 types of VOCs (1-butene, 1-pentene, furan, 2-propenal, 2-propanone, dichloromethane, 2-methyl-1-pentene, chloroform, benzene, toluene, oxylene, n-nonane, benzaldehyde, octane, and n-octyl ether) were investigated in a common rail direct injection (CRDI) diesel engine fueled with canola oil biodiesel fuel (COBF), conventional diesel fuel (CDF), and B20 (20% COBF blended with 80% CDF by volume) at various engine loads (30 Nm, 80 Nm, 130 Nm) and a constant engine speed of 1500 rpm. The total VOC emissions (TVOC) from burning B20 were lower than those from CDF and COBF at all experimental conditions. We also offer improved data about COBF applications to diesel engines based on our previous studies [46–48].
Table 1 Properties of CDF, B20, and COBF. Properties
Unit
CDF1
B202
COBF3
Density (at 15 °C) Viscosity (at 40 °C) Lower Heating Value Cetane Number Flash Point Pour Point Oxidation Stability Ester Content Sulfur Oxygen
(kg/m3) (mm2/s) (MJ/kg) – (°C) (°C) (h/110 °C) (%) ppm (%)
830.1 2.872 42.31 48.5 93 −21 25 – 500 0
840.1 3.016 41.756 51.1 110.8 – – – – –
880 4.290 39.49 61.5 182 −8 15 98.9 0 10.8
1 2 3
Conventional diesel fuel. 80% conventional diesel fuel blended with 20% canola oil biodiesel fuel by volume. Canola oil biodiesel fuel.
2.2. VOC emissions sampling system and VOC emissions analysis system 2.2.1. VOC emissions sampling system The temperature of exhaust emissions increases by about 350 °C when the CRDI diesel engine runs under high speed or high load conditions, and that high temperature can easily burst the sampling bag, causing collection failure. Therefore, a cooling device is needed to reduce the temperature of the exhaust gas enough for it to be safely collected by the sampling bag. A schematic diagram of the VOC emissions sampling system used in this experiment is shown in Fig. 2. The cooling fan from a diesel engine (2004 Hyundai Santa Fe, Ulsan, Korea) was used to cool the exhaust gas to a constant temperature of 30 ± 3 °C. A manifold was arranged at the rear end of the exhaust pipe after the cooling system. The VOC emissions sampling bag (5L, TDAP05, Aluminum Gas Sampling Bag, LKLABKOREA Inc., Gyeonggi-do, Korea) was connected to the manifold through a valve, and 5 L of exhaust gas for each of the 3 test fuels (CDF, B20, COBF) were collected at engine loads of 30 Nm, 80 Nm, and 130 Nm, all at a constant engine speed of 1500 rpm.
2. Materials and methods 2.1. Characteristics of test fuels Previous studies [46–48] found that, when the volume ratio of biodiesel to diesel reached 20%, the engine had excellent engine combustion performance and emitted only a small amount of harmful exhaust. Therefore, we selected CDF (SK self-service gas station, Jeonjusi, Korea), B20, and COBF (GS Bio, Yeosu-si, Korea) as test fuels. COBF, an alternative fuel, has been a research focus for a long time because of its low cost, safety, high environmental stability, rich oil content, and other desirable properties. Their physical and chemical properties are shown in Table 1. Clearly, the density and lower heating value of CDF and COBF are very similar, and the COBF has a high cetane number and oxygen content. They operate well in diesel engines as a good blended fuel because of their mutual dissolution properties.
2.2.2. VOC emissions analysis system The VOC emissions from the three test fuels were analyzed using a Purge & Trap analyzer (JDT-505II/2010GC/QP2010MS, Japan 267
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Table 2 Specifications of the test engine. Engine parameter
Units
Specifications
Type
–
Number of Cylinders Cylinder Diameter Stroke Injector hole diameter Number of injector nozzle holes Compression Ratio Max. Power
– mm mm mm –
CRDI diesel engine with a turbocharger 4 81 96 0.17 5
– kW/rpm
17.7:1 82/4000
2.3. Experimental details VOC emissions from a diesel engine (2004 Hyundai Santa Fe, Ulsan, Korea) fueled with the 3 test fuels were collected in VOC sampling bags at 30 Nm, 80 Nm, and 130 Nm at a constant engine speed of 1500 rpm. The 2.0 L experimental diesel engine was equipped with a turbocharger, 4 in-line cylinders, a high-pressure common rail, and a direct injection system. The specific parameters of the engine are shown in Table 2. Fig. 4 shows the specific settings diagram of this experiment. The CDF, B20, and COBF were individually injected directly into the combustion chamber via the high-pressure common rail system. The main injection timing was fixed at top dead center (TDC) 0° (crank angle/ oCA) by a combustion analysis and control system (HWANWOONG MECHATRONICS, Gyeongsangnam-do, Korea). The engine load was controlled at 30 Nm, 80 Nm, 130 Nm, while the speed was 1500 rpm, both controlled by an EC dynamometer (DY-230kW, HWANWOONG MECHATRONICS, Gyeongsangnam-do, Korea). The combustion pressure in the chamber was measured by a pressure sensor (KISTLER Type 6056A, Kistler Korea Co., Ltd., Gyeonggi-do, Korea). The combustion pressure signals were collected and arranged by a charge amplifier (KISTLER Type 5011, Kistler Korea Co., Ltd., Gyeonggi-do, Korea) and combustion analysis software (Cass Program, HWANWOONG MECHATRONICS, Gyeongsangnam-do, Korea). The CO and NOx emissions were measured by a multi-gas analyzer (GreenLine MK2, Eurotron (Korea) Ltd., Seoul, Korea). The HC emission was measured by a portable gasoline petrol and diesel exhaust gas analyzer (HPC501, Nantong Huapeng Electronics Co., Ltd., Jiangsu, China). An opacity smoke meter (OPA-102, QROTECH Co., Ltd., Gyeonggi-do, Korea) with the partial flow sampling method was used to measure the amount of PM emission. The cooling water temperature and intake air temperature were controlled at 85 ± 3 °C and 30 ± 3 °C, respectively. The specific experimental control conditions are shown in Table 3.
Fig. 2. Schematic diagram of the VOC emissions sampling system.
Analytical Industry, Tokyo, Japan) installed in the Center for University-Wide Research Facilities at Chonbuk National University, Korea. Fig. 3 shows a schematic diagram of the VOC emission analysis system. The JDT-505II and 2010GC/QP2010MS were used for purge and trap sampling and qualitative and quantitative analysis of VOC emissions, respectively. The specific experimental procedures are as follows. We used a Tenax Absorber (Tenax-GR; Japan Analytical Industry, Tokyo, Japan) to absorb 1L of VOCs from the sampling bag for qualitative analysis. The flow rate of the gas absorbed into the Tenax absorber was maintained at 0.065 L/min using a gas flow pump (MPS30; SIBATA, Tokyo, Japan). The VOCs were completely desorbed at 280 °C; the desorption time was 30 min at a gas flow rate of 0.05L/min. The temperatures of the cold-trap for sample trapping, pyrolysis, transmission tube, needle heater, and cold-trap heater were −40 °C, 280 °C, 280 °C, 280 °C, and 200 °C, respectively. The head pressure was 86 MPa, column flow rate was 0.001 L/min, and split ratio was 1/10. The 2010GC/QP2010MS was used to analyze the VOC composition. The experimental details are as follows: DB-624 column (30 m × 0.251 mm × 1.40 mm; Agilent Technologies, Wilmington, DE, USA); 30–600 mass scan; 0–30 min oven temperature program (40 °C for 3 min hold, 10 ml/min up to 260 °C, 5 min hold); 200 °C, ion source; 250 °C, transfer line; and 70 eV, EM voltage.
Fig. 3. Schematic diagram of the VOC emissions analysis system.
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Fig. 4. Schematic diagram of the experimental apparatus.
temperature and pressure inside the cylinder are relatively low, the mixture of fuel and air reaches a lean burn condition, the beginning of the combustion is mainly the chemical reaction of the fuel [49], and finally produces a small ROHR peak. Moreover, the ROHR of the three fuels decreased very obviously after BTDC0o (the red ring area in Fig. 1), it contributed to the main injection occurring at BTDC0o, the injected fuel absorbed a certain amount of heat when a large amount of fuel was atomized. The ignition delay is gradually shortened with the increase of the mixture ratio of canola oil biodiesel. This is because the cetane number of the COBF is 26.8% higher than that of the CDF (see Table 1), which makes it has a good ignition performance. These studies are in accordance with the observation reported in other literatures [41,43,47,48]. Fig. 5b shows the brake specific fuel consumption (BSFC) of three test fuels at various engine loads. The BSFC of three fuels gradually decreases with the increase of the engine load, and the BSFC of COBF is the highest compared with CDF and B20, this is because COBF has the lowest lower heating value among the three test fuels, which leads to COBF and B20 fuels’ consuming more fuel to produce the same power compared with CDF. In addition, similar to the results of Ge's study [47], the increasing trend of COBF's BSFC is most obvious compared with other fuels under low engine load (30 Nm) due to the high viscosity of COBF with the bad spray effect.
Table 3 Experimental and operating conditions. Test Parameters
Units
Operating Conditions
Engine Speed Engine Load Test Fuels Cooling Water Temp. Intake Air Temp. Main Injection Timing IVO5 IVC6 EVO7 EVC8
rpm Nm – °C °C Degree Degree Degree Degree Degree
1500 ± 5 30, 80, 130 CDF1, B202, COBF3 85 ± 3 30 ± 3 TDC4 0 353 223 128 366
1 2 3 4 5 6 7 8
Conventional diesel fuel. 80% conventional diesel fuel blended with 20% canola oil biodiesel fuel by volume. Canola oil biodiesel fuel. Top dead center. Intake valve opening timing. Intake valve closing timing. Exhaust valve opening timing. Exhaust valve closing timing.
3. Results and discussion 3.1. Combustion characteristics
3.2. Exhaust emission characteristics
The combustion characteristics of three test fuels are shown in Fig. 5. Fig. 5a shows the combustion pressure and rate of heat release (ROHR) of three test fuels in a CRDI diesel engine at 80 Nm with a constant engine speed of 1500 rpm. As shown in Fig. 5a, it can be clearly seen that the combustion pressure and ROHR of three test fuels are very similar, and the combustion pressure and ROHR of CDF is a little higher than that of B20 and COBF because of the highest lower heating value (see Table 1). In this study, as shown in Fig. 6, the pilot injection timing and main injection timing were controlled at before top dead center (BTDC) 10° and TDC0o, respectively. So there are two peaks (lift is pilot injection, right is main injection) on the ROHR curve in Fig. 6. A small amount of fuel is injected at BTDC10o, while the
3.2.1. Regulated emissions (CO, HC, NOx and PM) The exhaust regulated emission characteristics of three test fuels in a CRDI diesel engine under a constant engine speed of 1500 rpm and various engine loads are shown in Fig. 7. As shown in Fig. 7, overall analysis shows that CO, HC and PM have decreased a lot with the increase of the canola oil biodiesel ratio, while NOx is slightly increased. These similar results have been widely reported by many researchers in the field of biodiesel research [41,43–45,50]. In general, the CO and HC emissions exhaust from the diesel engine are negligible compared with the gasoline engine because the air fuel ratio of diesel engine is higher than that of gasoline. In Fig. 7, CO, HC and PM of three fuels are almost the same at low engine load of 30 Nm. This trend could be explained by 269
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Fig. 5. Combustion pressure (a) and brake specific energy consumption (b) for three test fuels.
that the promoting combustion performance of the oxygen atom in the canola oil biodiesel is not excited due to low cylinder pressure and temperature, furthermore, the viscosity of canola oil biodiesel is higher than that of diesel, its effect on fuel atomization is serious under low engine load. On the other hand, the CO, HC and PM of B20 and COBF have been obviously reduced a lot compared with CDF under medium and high engine load (80 Nm and 130 Nm). This can be explained in that the atomization effect of fuels is gradually improved with the increase of engine load [51,52]. Meanwhile, the promoting combustion performance of oxygen atom in canola oil biodiesel is also gradually activated at high cylinder pressure and temperature. At 80 Nm, CO, HC and PM of B20 and COBF is reduced by 45.7%, 57.1%, 42.3%, 50.0%, 54.1% and 75.7% compared with CDF, respectively. At 130 Nm, CO, HC and PM of B20 and COBF is reduced by 35.7%, 42.8%, 62.1%, 63.8%, 47.3% and 72.8% respectively, compared with CDF. For NOx emission, the NOx emission is slightly increased with the increase of mixing ratio of canola oil biodiesel under the low and medium engine load (30 Nm and 80 Nm), however, NOx of B20 and COBF are significantly increased by 8.6% and 55.1%, respectively, compared with CDF at high engine load of 130 Nm. Under high engine load, a large amount of oxygen is needed to achieve the state of complete
Fig. 6. Curve of combustion characteristic of CDF at 80Nm (obtained from the DL708E digital scope).
(a) CO and HC
(b) NOx and PM
Fig. 7. Regulated emission characteristics of three test fuels on (a) CO and HC, (b) NOx and PM.
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Fig. 8. Types of harmful of VOCs emitted by a diesel engine fueled with CDF at a constant engine load of 30 Nm.
(a) CDF
(b) B20
(c) COBF Fig. 9. VOC emissions from a diesel engine fueled with (a) CDF, (b) B20, (c) COBF.
speeds and high engine load conditions. Therefore, the VOCs emitted from the combustion of CDF, B20, and COBF in a CRDI diesel engine were collected under various engine loads of 30 Nm, 80 Nm, and 130 Nm with a constant speed of 1500 rpm and were analyzed using GC/MS.
combustion, at this time, the oxygen atoms of canola oil biodiesel will play an important role to make the fuel fully burn and generate a lot of heat, which directly leads to a significant increase of NOx. These similar results were also observed by [53–55].
3.2.2. Unregulated emissions (VOCs) Diesel engines produce large amounts of exhaust emissions at low
3.2.2.1. Types of harmful VOCs emitted. Fig. 8 shows the types of 271
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(a) 30 Nm
(b) 80 Nm
(c) 130 Nm Fig. 10. Comparison of VOC emissions from a diesel engine fueled with CDF, B20, and COBF at (a) 30 Nm, (b) 80 Nm, (c) 130 Nm.
reduced, along with CO and PM emissions [47]. As shown in Fig. 9b, the emissions of 1-butene, 1-pentene, 2-methyl-1-pentene, benzene, toluene, and n-nonane from B20 at 130 Nm were reduced by 37.8%, 31.1%, 2.0%, 61%, 38.3%, and 4.7%, respectively, compared with those at 30 Nm, and there were no furan, 2-propenal, 2-propanone, dichloromethane, octane, n-octyl ether, and o-xylene emissions. However, benzaldehyde emissions increased significantly as the engine load increased from 30 Nm to 130 Nm because benzaldehyde was heavily oxidized during the combustion of oxygen-rich B20 [34,42,47]. As shown in Fig. 9c, most VOC emissions from COBF were 0 at the high engine load of 130 Nm because most VOC emissions are closely related to the combustion state of the fuel. COBF is a high viscosity fuel, which makes it very difficult to burn fully at a low engine load of 30 Nm. On the other hand, benzene emissions were the largest of all VOC emissions from the three test fuels at all engine loads, about 41%. This finding is similar to previous results [34,56]. The VOC emission characteristics of the three test fuels were analyzed in detail for each engine load. Those results are shown in Fig. 10. Clearly, most of the VOC emissions from B20 were lesser than those from CDF and COBF, presumably because of the characteristics of B20, such as flash point, oxygenation, oxygen content, and certain number, as also suggested by Peng et al. [34], Hu et al. [57], and Ferreira et al. [58]. At 30 Nm, the TVOC emissions from B20 were 54.8% lower than those from CDF and 35.2% lower than those from COBF; at 80 Nm, the TVOC emissions from B20 were reduced by about 40.2% compared
harmful VOCs collected from burning CDF. Clearly, fueling the engine with CDF produced many peaks, each of which represents a specific kind of VOC. Through our GC/MS analysis, we found 30 kinds of VOCs in the CDF emissions, 22 kinds in the B20 emissions, and 19 kinds in the COBF emissions. The 15 most abundant harmful VOCs produced from burning CDF were 1-butene, 1-pentene, furan, 2-propenal, 2propanone, dichloromethane, 2-methyl-1-pentene, chloroform, benzene, toluene, o-xylene, n-nonane, benzaldehyde, octane, and noctyl ether. However, only 12 types of harmful VOCs were emitted with B20 (no octane or n-octyl ether), and only 11 kinds were emitted with COBF (no o-xylene, n-nonane, octane, or n-octyl ether). This result suggests that those VOCs were eliminated through some characteristic of canola oil, for example, its oxygen richness, which is about 10.8% (Table 1). These findings are similar to the reports of Peng et al. [34] and Correa et al. [56]. 3.2.2.2. VOC emissions. The characteristics of the VOC emissions from the CRDI diesel engine fueled with three test fuels under a constant engine speed of 1500 rpm and various engine loads are shown in Fig. 9. Clearly, most of the VOC emissions from all three test fuels decreased substantially as the engine load increased from 30 Nm to 130 Nm because the conditions in the combustion chamber, such as high injection pressure, good atomization, high combustion pressure, and turbulence intensity, improved with increased engine load [57]. In such a suitable combustion environment, the VOC emissions are greatly 272
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(a) 30 Nm
(b) 80 Nm
(c) 130 Nm Fig. 11. The most harmful VOCs emitted from a diesel engine fueled with CDF, B20, and COBF at (a) 30 Nm, (b) 80 Nm, (c) 130 Nm.
compared with CDF and by 36.8% compared with COBF. Therefore, the average value of CBT emissions at all test engine loads were reduced about 37.4% for B20 and 24.0% for COBF compared with CDF. In addition, benzene emission was significantly reduced for B20 compared with CDF at all engine loads. This indicates that B20 is an appropriate mixture for a blended fuel and is an oxygenated fuel that promotes efficient fuel burning. These results are similar to those reported previously [34,56–58].
with CDF and by 1.6% compared with COBF; at 130 Nm, the TVOC emissions from B20 were reduced by about 19.1% compared with CDF and 11.2% compared with COBF. Clearly, the decrease in VOC emissions was more evident at a low engine load (30 Nm) than at the high engine loads (80 Nm and 130 Nm). The temperature in the combustion chamber of the engine is lower at a low engine load than at a high engine load, so at the low load, some VOCs, such as 2-propanone and benzaldehyde, could not be oxidized. In addition, some VOCs (ethanone, benzoic acid, 1,3-isobenzofurandione, and maleic anhydride) were only present under a high engine load (130 Nm), and that trend increased with canola oil blend ratio, as so was particularly prevalent in COBF. COBF has higher viscosity and oxygen content than CDF; thus, the higher viscosity worsens the combustion conditions at a low engine load. However, the influence of viscosity decreases with the optimization of combustion conditions as the engine load and injection pressure increase. Therefore, many of these easily oxidized VOCs were produced under sufficient combustion and oxygen conditions [34]. Fortunately, however, the content and toxicity of those VOCs were insignificant compared with those of chloroform, benzene, and toluene.
4. Conclusions The combustion and exhaust emission characteristics (including to regulated and unregulated emissions) of the CRDI diesel engine fueled with CDF, B20, and COBF were comparatively analyzed under various engine loads and a constant engine speed of 1500 rpm. The specific conclusions are summarized as follows: i. The CRDI diesel engine can run well on three test fuels without engine modification. The combustion state of the engine was almost close to complete combustion at 80 Nm compared with 30 Nm and 130 Nm based on the combustion and emission characteristics. At this time, the regulated emissions (CO, HC and PM) of B20 and COBF were reduced by about 50% compared with CDF. ii. The types and amounts of VOCs emitted from CDF combustion were the largest, compared with those of B20 and COBF. Benzene was the main component, about 41%, of the VOCs emitted by all three test fuels. iii. The amount of VOCs emitted by the three test fuels decreased significantly as the engine load increased from 30 Nm to 130 Nm due to improved conditions in the combustion chamber. iv. Not all VOC emissions were reduced by increasing the mixing ratio of biodiesel. For example, benzaldehyde and benzoic acid were
3.2.2.3. Most harmful VOC emissions. Chloroform, benzene, and toluene are the VOCs most damaging to humans. Especially Benzene, is one of the carcinogenic substances. Fig. 11 shows the most harmful VOCs emitted from the CRDI diesel engine fueled with CDF, B20, and COBF under a constant engine spend and various engine loads. As shown in Fig. 11a, at 30 Nm, the average value of chloroform, benzene and toluene (CBT) emissions from B20 was reduced by about 31.0% compared with those from CDF and by 10.7% compared with those from COBF. As shown in Fig. 11b, at 80 Nm, the average value of CBT emissions from B20 was reduced about 42.9% compared with CDF and 24.4% compared with COBF. As shown in Fig. 11c, at 130 Nm, the average value of CBT emissions from B20 was reduced by about 38.3% 273
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readily oxidized at high temperatures and pressures. v. The amount of VOC emissions for B20 was lower than that for CDF and COBF under all experimental conditions. These findings once again demonstrate that B20 is an excellent alternative fuel.
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