a review on effect of oxygenated fuel additive on the

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A REVIEW ON EFFECT OF OXYGENATED FUEL ADDITIVE ON THE PERFORMANCE AND EMISSION CHARACTERISTICS OF DIESEL ENGINE

Bhavin H. Mehta*

P.G. Student, Mechanical Department, L. D. College of Engineering, Ahmedabad

Hiren V. MandaliaP.G. Student, Mechanical Department, L. D.

College of Engineering, Ahmedabad

Alpesh B. MistryLecturer, Mechanical Department, L. D. College of Engineering,

Ahmedabad

ABSTRACT The emissions from diesel engines also seriously threaten the environment and are considered one of the major sources of air pollution. The pollutants emitted from marine vessels are confirmed to cause the ecological environmental problems such as the ozone layer destruction, enhancement of the greenhouse effect, and acid rain, etc. Marine diesel engine emissions such as particulate matter and black smoke carry carcinogen components that significantly impact the health of human beings. Investigations on reducing pollutants, in particular particulate matter and nitrogen oxides are critical to human health, welfare and continued prosperity. The addition of an oxygenating agent into fuel oil is one of the possible approaches for reducing this problem because of the obvious fuel oil constituent influences on engine emission characteristics. The paper describes some properties of synthetic oxygenates and their influence on exhaust emissions from diesel engines. According to the results of examinations, oxygenates are an effective method for obtaining the reduction in the PM, CO and HC emissions without a significant increase in the NOx emission.Keywords: Oxygenates, Diesel engine, Emission.

1. INTRODUCTION

Diesel engines though enjoying higher fuel economy than gasoline engines suffer from inherent higher PM and nitride oxide (NOx) emissions. Currently there are many techniques that are capable of improving the combustion processes of diesel engines, such as the fuel injection retarding, exhaust gas recirculation (EGR), high-pressure injection, and air intake supercharging. However, due to the trade-off between the PM and NOx emissions, it is very difficult to have simultaneous reductions of both. In order to meet Euro IV, or the Chinese 4th Stage

Emission Standards, and the future regulations, diesel vehicles usually employ two types of technical strategies: (1) Reduce NOx by EGR and PM by diesel particulate filter (DPF) and (2) Control PM by high-pressure injection and reduce NOx by selective catalytic reduction (SCR). That is to say, the meeting of the 4th Stage or higher regulations requires exhaust after treatment devices to be installed. Because the cost of diesel after treatment devices are much higher than the three-way catalyst used on gasoline vehicles, the competitiveness and applicability of future diesel vehicles have been largely hindered. The reduction of diesel engine emissions could be considered from three aspects: the combustion improvement technique, the exhaust after treatment technology, and the fuel melioration. However, the relevant research on fuels especially on liquid fuels was still less investigated until very recently. The research on dimethyl ether (DME) as an alternative fuel produced great enlightenment. DME contains oxygen element and has no C–C bonds, which therefore helps to achieve smokeless combustion that is superior than with a diesel fuel even without high-pressure injection or turbocharger, however, the use of DME requires significant modifications on the fuel supply, delivery, and injection systems, which largely limits its application. The blending of oxygenates into a diesel fuel could effectively reduce the smoke emission from diesel engines, which has a strong synergy to the use of methanol, ethanol, or dimethyl carbonate (DMC). The studies are carried out on a set of oxygenated fuels, which include DMC, diethylene glycol dimethyl ether (DGM), and diethyl succinate (DES). The results indicated that the smoke emission decreased linearly as the oxygen content increased and notably near zero smoke emission was attained when the oxygen content was higher than 30%. The authors of this paper had utilized the highly soluble characteristics of biodiesel

13-14 May 2011 B.V.M. Engineering College, V.V.Nagar,Gujarat,India

National Conference on Recent Trends in Engineering & Technology

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to blend a high proportion of ethanol with the diesel fuel, which produced a significant reduction in smoke emission. However, the PM was not found reducing by the same extent, because the worsened ignitability of ethanol had led to a large increase in the soluble organic fraction (SOF) of PM. Biodiesel is also an oxygenated fuel and contains no aromatics. Many literatures reported that biodiesel could significantly reduce the smoke and PM emissions with slightly increase in NOx. From these studies, we considered it promising to significantly reduce the PM emission from diesel engines and thus to meet more stringent emission standards via fuel formulization design, at the current engine technology level and without using an exhaust after treatment device. The investigation was carried out by T. Nibin, A. Sathiyagnanam and S. Shivprakasam, 2003 to improve the performance of a diesel engine by adding oxygenated fuel additive of known percentages. The effect of fuel additive was to control the emission from diesel engine and to improve its performance. The fuel additive dimethyl carbonate was mixed with diesel fuel in concentrations of 5%, 10% and 15% and used. The experimental study was carried out in a multi-cylinder diesel engine. The result showed an appreciable reduction of emissions such as particulate matter, oxides of nitrogen, smoke density and marginal increase in the performance when compared with normal diesel engine [1].This paper prepared by J. Wang, J. Xiao and S. Shuai, 2009 explores the possibility to significantly reduce the particulate matter (PM) emissions by new fuel design. Several oxygenated blends were obtained by mixing the biodiesel, ethanol, and dimethyl carbonate (DMC), and diesel fuels. The tests were conducted on two heavy-duty diesel engines, both with a high-pressure injection system and a turbocharger. The total PM and its dry soot (DS) and soluble organic fraction (SOF) constituents were analyzed corresponding to their specific fuel physiochemical properties. A blended fuel that contains biodiesel, DMC, and high cetane number diesel fuels was chosen eventually to enable the diesel engines to meet the Euro IV emission regulation. Based on the test results, the basic design principles were derived for the oxygenated blends that not only need the high oxygen content, but also the high cetane number and the low sulfur and low aromatic contents. The fuels used in this study include a baseline diesel fuel, three types of biodiesels, and their blends with ethanol, DMC, DMM, and straight-run (or directly distilled) diesel fuel. Ethanol, DMC, and DMM are used as oxygenates to raise the oxygen content, while the straight-run diesel fuel is used to improve the auto-ignition capability of the blended fuel. When fueling oxygenated blends, the direct soot constituent in PM emissions decreases significantly as the fuel oxygen content increases. However, when the oxygen content reaches 15% or higher, reduction rate becomes slow [2].

This experiment was carried out by H. Hess, A. Boehman and J. Perez on six cylinder diesel engine by using a diesel fuel reformulating agent, CETANER, has been examined in a popular light-medium duty turbo diesel engine over a range of blending ratios. As much as an 83% reduction in particulate mass emissions was observed and the impact of the additive on gaseous emissions is not as clear, with substantial scatter observedin CO and total hydrocarbon emissions. Emissions of NOx were consistently lower for all CETANER blend ratios, although the trend with increasing CETANER concentration is noisy and examination of the combustion process through in cylinder pressure trace analysis showed only a slight decrease in peak pressure and a slight increase in combustion duration, with no significant change in ignition delay [3].

2. OXYGENATED FUEL ADDITIVE: Oxygenated fuel is nothing more than fuel that has a chemical compound containing oxygen. It is used to help fuel burn more efficiently and cut down on some types of atmospheric pollution. In many cases, it is credited with reducing the smog problem in major urban centers. It can also reduce deadly carbon monoxide emissions.

Oxygenated fuel works by allowing the gasoline in vehicles to burn more completely. Because more of the fuel is burning, there are fewer harmful chemicals released into the atmosphere. In addition to being cleaner burning, oxygenated fuel also helps cut down on the amount of non-renewable fossil fuels consumed. Various additives used for oxygen enrichment of fuel are as below.

Dimethyl carbonate, often abbreviated DMC, is a flammable clear liquid boiling at 90 °C. It is a carbonate ester which has recently found use as a methylatingreagent. It was also classified as an exempt compound under the definition of volatile organic compounds by the U.S. EPA in 2009. Its main benefit over other methylating reagents such as iodomethane and dimethyl sulfate is its much lower toxicity and its biodegradability. Also, it is now prepared from catalytic oxidative carbonylation of methanol with carbon monoxide and oxygen, instead of from phosgene. This allows dimethyl carbonate to be considered a green reagent.

Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a clear, colorless, aprotic, and liquid ether that is used as a solvent. Dimethoxyethane is miscible with water. Dimethoxyethane is often used as a higher boiling alternative to diethyl ether and THF. Dimethoxyethane forms chelate complexes with cations and acts as a bidentate ligand. It is therefore often used in



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organometallic chemistry like Grignard reactions, hydride reductions, and palladium-catalyzed reactions like Suzuki reactions and Stille coupling. Dimethoxyethane is also a good solvent for oligo- and polysaccharides.

2-Ethylhexyl acrylate is a water white liquid with a characteristic odor. It is supplied inhibited to prevent polymerization. It is a stable product, with only negligible solubility in water. It is readily polymerized and displays a range of properties dependent upon the selection of the monomer and reaction conditions. 2-ethylhexyl acrylate is used in the production of homopolymers. It is also used in the production of co-polymers, for example acrylic acid and its salts, esters, amides, methacrylates, acrylonitrile, maleates, vinyl acetate, vinyl chloride, vinylidene chloride, styrene, butadiene and unsaturated polyesters. 2-ethylhexyl acrylate is also used in pressure sensitive adhesives. Among alcohol fuels, ethanol has good solubility, biodegradability, causticity and emissions performance, and is therefore more appropriate than methanol for a diesel engine. A merit of ethanol is that the oxygen content is as high as 34.8%, but it’s disadvantageous cetane number is as low as merely eight and its viscosity as low as less than 1/3 of a diesel fuel. Additionally, the boiling point of ethanol is relatively low, and therefore its transportation and storage safety control should be treated the same as gasoline. Dimethyl carbonates (DMC) and Dimethoxy methane (DMM) also have high oxygen content and have been considered as diesel fuels. DMC and DMM contain 53.3% and 42.1% of oxygen by mass respectively; and both of which are higher than the ethanol oxygen content. Their cetane numbers are 36 and 30, respectively, higher than ethanol’s cetane number too. Therefore, according to the above basic principles – a high oxygen content and a high cetane number – these two oxygenates are both better than ethanol especially ideal for DMC. The boiling point of DMC is 910 C which is higher than ethanol’s 780 C and DMM’s 430 C. The viscosity values of DMC, DMM, and ethanol are all very low, which could be used to offset the high viscosity of the biodiesel constituent in the blended fuel.

3. EXPERIMENTAL SET-UP:

Figure 1. Experimental Set-up [3]

A single-cylinder, 4-Stroke, water-cooled diesel engine of 5 hp rated power will be considered for the purpose of experimentation. The engine is coupled to a rope brake dynamometer through a load cell. It is integrated with a data acquisition system to store the data for the off-line analysis. The effects of oxygen enrichment in base fuel on diesel combustion and emissions will be studied separately at different loads in a DI diesel engine at a constant speed of 1520 rpm. Oxygenated fuel additive will be added in diesel at different proportion and its effect on engine performance and emission will be measured.

4. EFFECT OF OXYGENATED FUEL ADDITIVE ON THE PERFORMANCE AND EMISSION CHARACTERISTICS OF THE ENGINE:

4.1 Brake thermal efficiency: As shown in fig 2 with increase in brake power brake thermal efficiency increases. The maximum brake thermal efficiency is achieved when 5% DMC is added to diesel fuel [1].



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Figure 2. Brake thermal efficiency against brake power for different proportion of DMC.

4.2 Smoke Density:

Figure 3. Smoke density against brake power for different proportion of DMC.

Figure 3 shows the variation of smoke density with brake power at 2000 rpm. It can be observed that smoke density increases with increase in the brake power. Maximum emission occurs at maximum load. Smoke density is 30 HSU for the normal diesel engine operation. It can be seen that 5% DMC added to diesel fuel effectively reduces the smoke density. The oxygen enrichment provided by the DMC leads to smoke reduction. The smoke reduction rate and smoke emission show linear relationship with DMC percentages. Smoke is reduced by 20 % for 5 % DMC addition [1].4.3 Particulate Matter:

Figure 4. Particulate matter against brake power for different proportion of DMC.

Figure 4 shows that particulate emissions increase with increase in the brake power with the maximum emission occurs at maximum load. Particulate emission is 0.15 g/h for the normal diesel engine operation and 5% DMC added to diesel fuel effectively reduces the particulate matter. This is due to higher combustion temperature [1].4.4 Oxides of Nitrogen: Figure 5 shows the variation of NOx with brake power. It can be observed that NOx increases with increase in brake power. It can be seen that 5% DMC added to diesel fuel, considerably increases the NOx emission when compared to the normal diesel engine. The increase in NOx with DMC added may be caused by the high temperature promoted by combustion and oxygen enrichment [1].

Figure 5. Oxides of Nitrogen against brake power for different proportion of DMC.

4.5 Soot: Figure 6 shows the variation of soot with brake power. It can be observed that soot increases with increasing the brake power. It can be seen that 5% DMC added to diesel fuel effectively reducing the soot by 52 %[1].

Figure 6. Soot against brake power for different proportion of DMC.

5. SUMMARY: Various oxygenated fuel additives are available which posses more oxygen content compared to diesel. If these additives are added in diesel at appropriate proportion it will improve the engine performance and emission characteristics. If the proportion of these additives is more than engine performance declines



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because the additives have lower calorific value compared to diesel. Other barriers in the use of oxygenated fuel additives are their high price and poor availability.

REFERENCES:[1] T. Nibin, A. Sathiyagnanam, S. Sivaprakasam, 2003, “Investigation on emission characteristics of a diesel engine using oxygenated fuel additive”. [2] J. Wang, F. Wu, J. Xiao, 2009, “Oxygenated blend design and its effects on reducing diesel particulate emissions”, Science direct, 2037-2045.[3] H. Hess, J. szybist, J. Perez, “Impact of oxygenated fuel on diesel engine performance and emissions”.

[4] C. Y. Lin and J. C. Huang, 2003, “An oxygenating additive for improving the performance and emission characteristics of marine diesel engines”, Science direct, 1699-1715.[5] Miłosław Kozak, Jerzy Merkisz, 2007, “SOME CONSIDERATIONS ON THE OXYGENATED FUELS FOR DIESEL ENGINES”, Ol-pan, 129-136.



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