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Abstract

This article chose the new type alcohol-based fuel as the engine fuel, realized lean burn in a CA4GA5 engine, and got the lean burn limit to 20.6. Taking the gasoline as equivalent fuel, and according to 10%, 20%, and 30% volume proportion of alcohol-based fuel, three new types of alcohol-based gasoline synthetic fuel, M10, M20, and M30, were formed. A comparative study of the original engine emissions used new types of alcohol-based gasoline synthetic fuels with Compressed Natural Gas (CNG) and different blending ratios based on M0 at different stoichiometric air-to-fuel ratios was carried out. This article studied the influence of air-to-fuel ratio on cycle emissions under the lean burn condition and analyzed the characteristics of the new European driving cycle. Experimental results show that compared with the working condition of pure gasoline engine, the emissions of total hydrocarbon and carbon monoxide gradually reduce with the increase of alcohol-based fuel blending proportion, while the NO_x content presents the rising trend.

Keywords

Spark ignition engine alcohol-based fuel lean burn emission characteristics new European driving cycle

Introduction

Along with the rapid development of auto industry and the sharp increase of the vehicle holdings, the energy security and atmospheric environment are facing increasingly severe challenges.¹ From the 1960s, under the condition that the oil crisis put great pressure on European and American countries’ energy securities, alcohol fuel came into sight.^2–5 With the development of social economy, the Chinese oil import has gotten a rapid growth,^6–11 and the external dependence on oil has also increased. China became a net importer of oil since the early 1990s. As a fuel, methanol is an oxygen-rich content which can be full combustion. With the deepening of methanol research, it was found that up to 50% oxygen content was conducive to the complete combustion of fuels and then reduced the exhaust emission of hydrocarbons of vehicles.^12–16 And it had a great substituted ratio and its sources of raw materials were abundant, such as coal, natural gas, coke-oven gas, and coal bed methane. China has abundant coal resources, and the technology of producing methanol by coal is mature with low cost. So the methanol can be one of the most effective alternatives to petroleum resources in China. Since the 21 st century, although the international research and application of methanol fuel have stalled and become a controversial issue in China, there are still some researchers continuing to carry out relevant researches.^17–19 Some studies used 3%–5% methanol and gasoline blending.²⁰ This mixing effectively increased oxygen content in gasoline with a little agent and has been widely used in Europe and China. The result showed that it had no effect on the dynamic properties of gasoline and increased the octane number and reduced the exhaust pollution. Some studies used 85% methanol and 15% of additive.²¹ In spite of this, the methanol gasoline research is still not mature enough. The current studies mostly focus on alcohol-based fuel which contains only one kind of alcohol, such as methanol gasoline. This article is designed to study the emission characteristics of new fuels. In order to achieve this goal, the new types of alcohol-based were used as the engine fuel. A comparative study of the original engine emissions used new types of alcohol-based gasoline synthetic fuels with CNG and different blending ratios based on M0 at different stoichiometric air-to-fuel ratios (AFRs) was carried out. And then the influence of the different alcohol-based fuel blending ratios on the new European driving cycle (NEDC) cycle emission performances such as the cold-start emission performance was analyzed.

The new types of alcohol-based gasoline synthetic fuel

The blending technology of alcohol-based fuel

The two-step method was adopted to deal with the methanol. The methanol was blended by incomplete dehydration method and distilled by adding effective additives simultaneously. The molecular structure was combined by catalysis again and the alcohol-based fuel was obtained. In addition, in order to reduce the vapor pressure of alcohol-based fuel and improve its distillation range and calorific value, a certain proportional additives was still needed to be added to the obtained alcohol-based fuel. And we should dehydrate the industrial methanol and remove the impurities at atmospheric pressure.

The blending of new types of alcohol-based gasoline synthetic fuel

The new type of alcohol-based gasoline synthetic fuel was blended by adding a certain proportion of the alcohol-based fuel into the gasoline. The fuel was composed of low-carbon alcohol, multi-carbon alcohol, aromatic hydrocarbon, solvent naphtha, additives, and others. Among them, the low-carbon alcohol was the main constituent of the methyl alcohol, and the solvent naphtha was gasoline. The general volume fraction is shown in Table 1.

Table 1.

New vehicle alcohol-based gasoline fuel composition.

Name	The alcohol-based fuel (calculate according to 100%)				Solvent oil
Name	Low-carbon alcohol	Multi-carbon alcohol	Aromatic hydrocarbon	Additives (aether and ester)	93^#(Octane Number 93)gasoline
Volume fraction	70%	10%	15%	5%	M10 (90%) M20 (80%) M30 (70%)

Experimental apparatus and equipment

Experimental engine

The engine (CA4GA5) was a four-cylinder electronic control 16 valves, Variable Cam Timing-Intake (VCT—i) port fuel injection gasoline engine produced by China FAW Group Corporation. Before operation and performance testing, the engine operation specification has been completed and the transformation of lean burn has been completed. The main parameters are shown in Table 2.

Table 2.

Main parameters of CA4GA5 engine.

Parameters	Specification
Displacement (dm³)	1.497
Model	Inline four-cylinder, liquid cooled, four-stroke
Cylinder diameter (mm) × stroke (mm)	73 × 89.4
Maximum torque (N m/r/min)	135/4400
Rated power (kW/r/min)	75/6000
Valve type	16 valves, VCT—i valve timing system
Specific fuel consumption (g/kW h)	275
Compression ratio	10.2
Mixing way of oil and gas	Electronically controlled multi-point injection of inlet fuel

Based on the differences in the volume fraction of the alcohol-based fuel, the new types of vehicle alcohol-based gasoline synthetic fuel were divided into M10, M20, and M30. In order to analyze the original emission characteristics of M10, M20, and M30, the three-way catalytic converter installed in the original machine was replaced by an empty substrate without precious metal coating.

Vehicle drum test bed

Vehicle drum test bed mainly included environment simulation module, chassis dynamometer system (including driver auxiliary equipment), exhaust analysis system, and main control center:

Environment simulation module. Using the Electronic Throttle Control (ETC) environment simulation module produced by the United States ETC company, temperature ranges from −40°C to 60°C; control accuracy of ±1°C; humidity ranges from 5% relative humidity (RH) to 95% RH; control accuracy of ±5 RH; the maximum wind speed of 200 km/h; the maximum illumination intensity of 1200 W/m²; control accuracy of ±2.5%; thermal simulation system ranges from +20°C to +75°C.

Chassis dynamometer system. The main parameters of the selected dynamometer were as follows: maximum measurement speed of 200 km/h; speed accuracy of 0.08 km/h; maximum range of 5840 N; full-scale accuracy of ±0.1%.

Experimental vehicle

The vehicle used here is a self-brand gasoline/CNG dual-fuel economy sedan. The main parameters are shown in Table 3.

Table 3.

Parameters of testing vehicle.

Parameter	Specification
L × W × H (mm)	4290 × 1680 × 1500
Wheelbase (mm)	2425
Tread (front/rear, mm)	1440/1420
Gearbox	5MT
Fuel consumption (L/100 km)	≤6.1
Curb mass (kg)	995
Maximum speed (km/h)	≥180

Analysis of AFRs impact on emission performance

Figures 1 –3 demonstrate the relationship between the emission of total hydrocarbon (THC), carbon monoxide (CO), or NO_x and AFR with pure gasoline M0 and new types of alcohol-based gasoline synthetic fuels M10, M20, and M30 under the conditions of P_me is 0.3 MPa or 0.7 MPa and the engine speed is 2000 r/min or n = 3200 r/min. According to these figures, when the engine is under working condition with the same load and different speeds, the AFR has a certain effect on the emission performance of these four fuels.

Figure 1.

Comparisons of THC emission at different AFRs:(a) on P_me (0.3 MPa) and (b) on P_me (0.7 MPa).

Figure 2.

Comparisons of CO emission at different AFRs:(a) on P_me (0.3 MPa) and (b) on P_me (0.7 MPa).

Figure 3.

Comparisons of NO_x emission at different AFRs: (a) on P_me (0.3 MPa) and (b) on P_me (0.7 MPa).

From Figure 1, as the AFR increases from 14.7 to 20.6, the THC emission reduces first and then increases. In the process of AFR increase from 14.7 to 17.6, the THC emission (P_me = 0.3 MPa, n = 2000 r/min) of M0, M10, M20, or M30 reduces by 52.14%, 57.73%, 51.61%, and 67.03%, respectively. When AFR = 17.6, the emission of THC reaches the minimum. And the THC emission (P_me = 0.3 MPa, n = 2000 r/min) of M0, M10, M20, or M30 is 2357, 1942, 1845, and 1143 ppm, respectively. During these processes, the increase tendency of THC emissions is obvious. When AFR = 20.6, the emission of THC reaches the maximum. And the THC emission (P_me = 0.3 MPa, n = 2000 r/min) of M0, M10, M20, or M30 reaches 21,750, 16,305, 14,246, and 11,861 ppm, respectively, correspondingly increasing by 822.34%, 739.22%, 672.74%, and 937.10%, compared with those in the same working condition with AFR = 17.6. The trend of increase is greater than that of decrease. This is mainly because that with the increase of AFR, the in-cylinder mixture is more dilute. And the fuel is burnt more fully, which is in favor of the reduction of THC emission. When AFR = 17.6, the combustion of in-cylinder mixture is the most abundant and THC emission reduces to the minimum. With the further increase of AFR, the combustible mixture is too thin and results in slowing the burn rate, aggravating surface quenching phenomena, thickening the chilled layer, increasing incomplete combustion of mixture, and causing a large number of unexploded THC emission.

From Figure 1, it can be seen that in the increasing process of AFR, with the increase of the mixing proportion of alcohol-based fuel under the same operating conditions, the THC emission is on a declining curve. This is mainly because that the alcohol-based fuel is oxygenated fuel, the percentage of oxygen in fuel gradually increases with the increase of blending ratio, which is conducive to the oxygenation of THC. The THC emission of M0 or M10 is similar with each other, whose change of average rate is 0.05%, while the THC emission of M20 is close to that of M30 (the change of average rate is 0.17%). Compared with the THC emission changes of M20, the average reduction rate of M10 is about 16.86%. This is largely because that although the oxygen content of M10 increases, mixing proportion is still low and its influence on M10 is not obvious, while the mixing proportion of M20 or M30 is relatively high, and their influence on THC emission is more apparent.

From Figure 2, it can be seen that with the AFR gradually increasing from 14.7 to 20.6, the CO emissions of these four types of engine fuel are on a declining curve. When AFR is 14.7, the CO emission reaches the maximum, and with the increase of AFR, the CO emission rapidly reduces. When AFR is 20.6, the CO emission reaches the minimum. And when AFR changes from 19.8 to 20.6, the change of CO emission becomes unobvious. This is mainly because that with the increase of AFR, the oxygen content of combustible mixture also increases, which offers a favorable condition for the further oxidization of CO. Therefore, with the gradually increase of AFR, the CO emission rapidly reduces. After AFR increases to 19.8, the increase of AFR has little influence on CO emission since oxygen content has been excessive.

Form Figure 2, under the same operating condition, with the increase of blending ratio of alcohol-based fuel, the CO emission presents a downward trend. This is mainly because that the alcohol-based fuel is oxygenated fuel. The gradual increase of the percentage of oxygen in fuel with the increase of blending ratio provides an appropriate condition for further oxidation of CO. At the same AFR, the CO emission of M0 is close to that of M10, and that of M20 is close to that of M30. Compared with M10, the CO emission of M20 decreases more obviously at the beginning. This is because the blending ratio of M10 is lower and the influence on CO emission is not obvious compared with gasoline. The blending ratio of M20 or M30 is higher, and the oxygen promotes the further oxidation of CO. It can be concluded from the above that at the early stage, the CO emission of different alcohol-based fuel rapidly declines with the increase of AFR and then decreases slowly. Until the AFR reaches 19.8, the change trend of CO emission tends to be flat. Besides, along with the increase of blending ratio of alcohol, the CO emission under the same AFR presents a downward trend.

As the AFR increases gradually from 14.7 to 20.6 in Figure 3, the NO_x emissions of these four types of fuel increase first and then show a trend of decline. What is more, it reaches the maximum value when the AFR is in the range of 17.5–19.5. This is mainly because that with the increase of AFR from 14.7, the oxygen concentration in the mixture gradually increases, the combustion tends to be more completely with higher combustion temperature and the NO_x emission increases. When the AFR is in the range of 17.5–19.5, the engine is in the economic fuel consumption area with the best combustion status and highest combustion temperature. At this time, the mixture in cylinder is under the oxygen-enriched condition. The concurrence of high temperature of the engine, oxygen-enriched condition, and the duration of high temperature make the NO_x emission reaches the peak value, and the NO_x emission of M0, M10, M20, or M30 (P_me = 0.7 MPa, n = 3200 r/min)is 2950, 3014, 3141, and 3183 ppm, respectively. With the further increase of AFR, the mixture becomes rarer and rarer, resulting in a decrease of the maximum combustion temperature of mixture and thus making the NO_x emission decrease. When the AFR is 20.6, the NO_x emission reaches the minimum value, and the NO_x emission of M0, M10, M20, or M30 (P_me = 0.7 MPa, n = 3200 r/min)is 407, 428, 513, and 609 ppm, respectively.

From Figure 3, it can be seen that under the same operating conditions, the NO_x emission shows a trend of increasing with the increase of blending ratio of alcohol-based fuel in the alcohol-based gasoline synthetic fuel. This is mainly because that the alcohol-based fuel is an oxygenated fuel. And the ratio of oxygen, which is conducive to the generation of NO_x, increases gradually with the increase of blending ratio. Although the latent heat of vaporization of alcohol-based fuel reduces the combustion temperature and suppresses the formation of NO_x, the promoting effect of oxygen content in alcohol-based fuel is greater than the inhibiting effect of latent heat of vaporization. At the same AFR, the NO_x emission of M0 or M10 is very close, and the average changing rate of that is 3.17% (P_me = 0.7 MPa, n = 2000 r/min). While the NO_x emission of M20 is close to that of M30, the average change rate of that is 13.32% (P_me = 0.7 MPa, n = 2000 r/min). This is mainly because that when the blending ratio of alcohol-based fuel is higher than 20%, the oxygen atom from the combustion of the mixture will magnify the oxygen concentration of part of the cylinder, which is conducive to the generation of NO_x.

Experimental study on NEDC emission characteristic

Experimental program

The experiment was carried out in accordance with the “Emission Test of Exhaust Pollutants After Cold Start at Normal Temperature (Type I Test)” formulated in GB18352.3-2005 “Limits and Measurement Methods for Emission of Light Pollutants for Vehicles (III, IV),” including Urban Driving Cycle and Extra Urban Driving Cycle, as shown in Figure 4. The “Urban Driving Cycle” is divided into six parts according to the operation, as shown in Table 4. The “Extra Urban Driving Cycle” is divided into six parts according to the operation, as shown in Table 5.

Figure 4.

New European driving cycle (NEDC).

Table 4.

Operation of urban driving cycle decomposition.

Cases	Time (s)	Proportion (%)
Idle	60	30.8
Idle, deceleration, clutch off	9	4.6
Shift	8	4.1
Accelerate	36	18.5
Uniform	57	29.2
Deceleration	25	12.8
Total	195	100

Table 5.

Operation of extra urban driving cycle decomposition.

Cases	Time (s)	Proportion (%)
Idle	40	10.0
Idle, deceleration, clutch off	10	2.5
Shift	6	1.5
Accelerate	103	25.8
Uniform	209	52.2
Deceleration	32	8.0
Total	400	100

Effect of alcohol-based fuel on the THC emission of driving cycle

It can be seen from Figure 5(a) that there are more THC emission of M0, CNG, M10, M20, or M30 in 195 s’ urban cycle case 1. This is because that the AFR is under the stoichiometric value due to the enrichment for fuel in the cold-start stage. In addition, cold shock effect is strong, mixed gas atomization is not good, and combustion is not stability due to the low temperature of cylinder and piston under the cold-start condition. THC emission of M0, CNG, M10, M20, or M30 in urban cycle cases 2, 3, and 4 is steady relatively because of the increasing of temperature and complete combustion. Figure 5(c) shows THC emission under Extra Urban Driving Cycle. The THC emission of M10, M20, or M30 is greater than M0 and CNG, and the fluctuation frequency is larger. That is because the enrichment for fuel leads to the incomplete combustion.

Figure 5.

Comparisons of THC emission: (a) on NEDC (1–195 s), (b) on NEDC (196–780 s), and (c) on NEDC (781–1180 s).

Effect of alcohol-based fuel on the CO emission of driving cycle

As it is shown in Figure 6(a), the peaks of the CO emissions of these five fuels occur in urban cycle case 1 because the non-uniform fuel atomization and low mixture gas temperature at the beginning of the engine operation. And the CO emission gradually reduces and then stabilizes in urban cycle cases 2, 3, or 4 because of the higher mixture gas temperature, uniform fuel atomization, and enough CO oxidation under engine stable operation according to Figure 6(b). However, the CO emission is relatively high under 400 s suburban driving cycles because the fuel delivery increases and the O₂ decreases relatively under heavy load operating conditions.

Figure 6.

Comparisons of THC emission: (a) on NEDC (1–195 s), (b) on NEDC (196–780 s), and (c) on NEDC (781–1180 s).

Effect of alcohol-based fuel on the NO_x emission of driving cycle

By comparing the statistics of Figure 7(a) and (b), the NO_x emission under urban driving conditions 2, 3, or 4 is higher than that of urban driving condition 1. That is mainly because the production of NO_x is lower with the non-uniform fuel atomization and low burning temperature at the beginning of the engine operation. By comparing the statistics of Figure 7(b) and (c), the NO_x emission under suburban driving conditions is relatively high. That is mainly because the engine speed is higher under suburban conditions, which causes the increase of in-cylinder fuel mass per unit time and the increase of NO_x emission.

Figure 7.

Comparisons of NO_x emission: (a) on NEDC (1–195 s), (b) on NEDC (196–780 s), and (c) on NEDC (781–1180 s).

Conclusion

This article took gasoline as an equivalent fuel and formed other three new types of alcohol-based gasoline synthetic fuel, M10, M20, and M30, according to 10%, 20%, and 30% volume proportion of alcohol-based fuel. And the effect of AFR on the original engine emissions of three conventional emissions, THC, CO, and NO_x, of new types of vehicle alcohol-based gasoline synthetic fuel under the lean burn condition were studied. And then the test that used pure gasoline M0, CNG, and new alcohol-based gasoline synthetic fuels M10, M20, M30 was carried out on the drum test bed under NEDC. The following conclusions are drawn:

First, under certain engine speed and load, the fuel consumption ratio of M0, M10, M20, and M30 reduces first and then increases with the increase of AFR. The minimum value appears when AFR is in the range of 16.5–18.5.

Second, with the increase of AFR, the THC emission of M0, M10, M20, or M30 reduces first and then increases. The minimum value appears when AFR = 17.6. And when AFR is less than 17.6, the decreasing trend is smaller than the increasing trend when AFR is greater than 17.6. Under the same operating conditions, with the increase of blending ratio of alcohol-based fuel, the THC emission reduces. With the increase of AFR, the CO emission gradually decreases. And under the same operating conditions, with the increase of blending ratio of alcohol-based fuel, the CO emission reduces. With the increase of AFR, the NO_x emission increases first and then reduces, and the minimum value of that appears when AFR changes from 17.5 to 19.5. Under the same operating conditions, with the increase of blending ratio of alcohol-based fuels, the NO_x emission presents an increasing trend. And the emissions have the similar trend on the drum test bed under NEDC.

Third, in the first urban driving cycles, due to cold start of the engine, the temperature of combustible mixture is low and the narrow gap effect is obvious. These bring out a large amount of unburned THC and combustion intermediate CO, which reach peak under this driving condition. And the low combustion temperature and anoxic environment lead to the minimum NO_x emission peak during the whole experiment process.

Footnotes

Handling Editor: Haiping Du

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors wish to express their deep gratitude to National Science Foundation of China (approval no. 51576140), National High Technology Research and Development Program (“863” Program) of China (approval no. 2008AA06Z322).

References

Dagaut

Togbé

Oxidation kinetics of butanol–gasoline surrogate mixtures in a jet-stirred reactor: experimental and modeling study. Fuel 2008; 87: 3313–3321.

Brakora

Reitz

et al . Development and validation of a reduced reaction mechanism for biodiesel-fueled engine simulations. SAE Int J Fuels Lubr 2009; 1: 675–702.

Kitamura

Kee

Mohammadi

et al . Study on NO_x control in direct-injection PCCI combustion—fundamental investigation using a constant-volume vessel. SAE technical paper 2006-01-0919, 2006.

Ryu

Kim

Lee

A study on the spray structure and evaporation characteristic of common rail type high pressure injector in homogeneous charge compression ignition engine. Fuel 2005; 84: 2341–2350.

Toorisaka

Minamikawa

Narita

et al . DPR developed for extremely low PM emissions in production commercial vehicles. SAE Transactions 2004; 113: 447–456.

Shuai

Wang

JX.

Study on combustion characteristics and PM emission of diesel engines using ester–ethanol–diesel blended fuels. P Combust Inst 2007; 31: 2981–2989.

Kohse-Höinghaus

Oßwald

Cool

et al . Biofuel combustion chemistry: from ethanol to biodiesel. Angew Chem Int Edit 2010; 49: 3572–3597.

Heimrich

Albu

Ahuja

Electrically heated catalysts for cold-start emission control on gasoline- and methanol-fueled vehicles. J Eng Gas Turb Power 1992; 114: 496–501.

Wei

Liu

et al . Improvement of spark-ignition (SI) engine combustion and emission during cold start, fueled with methanol/gasoline blends. Energ Fuel 2007; 21: 171–175.

10.

Gao

Shen

Experimental comparisons of hypothesis test and moving average based combustion phase controllers. ISA T 2016; 65: 504–515.

11.

Xie

Song

A hybrid disturbance rejection control solution for variable valve timing system of gasoline engines. ISA T 2014; 53: 889–898.

12.

Impact of lean-burn control technology on the fuel economy and NOx emission of gasoline engines. Proc IMechE, Part D: J Automobile Engineering 2010; 224: 1041–1058.

13.

Lumsden

Eddleston

Sykes

Comparing lean burn and EGR. SAE technical paper 970505, 1997.

14.

Hori

Okumura

Goto

et al . Development of new selective NO_x reduction catalyst for gasoline leanburn engines. SAE technical paper 972850, 1997.

15.

Takami

Takemoto

Iwakuni

et al . Development of lean burn catalyst. SAE technical paper 950746, 1995.

16.

Dahl

Denbratt

Koopmans

An evaluation of different combustion strategies for SI engines in a multi-mode combustion engine. SAE Int J Engines 2009; 1: 324–335.

17.

Burch

Millington

Selective reduction of nitrogen oxides by hydrocarbons under lean-burn conditions using supported platinum group metal catalysts. Catal Today 1995; 26: 185–206.

18.

Fendeleur

Pope

Mahzoul

et al . A laboratory study of NO_x reduction during the rich operating period over a NO_x storage catalyst. SAE technical paper 1999-01-3502, 1999.

19.

Strehlau

Leyrer

Lox

et al . New developments in lean NO_x catalysis for gasoline fueled passenger cars in Europe. SAE technical paper 962047, 1996.

20.

Wang

Liu

et al . Emission reduction on the mixed alcohols-gasoline fuel. Trans CSICE 2008; 4: 359–363.

21.

Wang

et al . Contribution ratio of methanol to HC emission of a gasohol fueled spark ignition engine. J Xi’an Jiaotong Univ 2014; 3: 39–43.

Experimental investigation of emission characteristics based on new alcohol-based gasoline fuel

Abstract

Keywords

Introduction

The new types of alcohol-based gasoline synthetic fuel

The blending technology of alcohol-based fuel

The blending of new types of alcohol-based gasoline synthetic fuel

Experimental apparatus and equipment

Experimental engine

Vehicle drum test bed

Experimental vehicle

Analysis of AFRs impact on emission performance

Experimental study on NEDC emission characteristic

Experimental program

Effect of alcohol-based fuel on the THC emission of driving cycle

Effect of alcohol-based fuel on the CO emission of driving cycle

Effect of alcohol-based fuel on the NOx emission of driving cycle

Conclusion

Footnotes

Declaration of conflicting interests

Funding

References

Effect of alcohol-based fuel on the NO_x emission of driving cycle