Applied Mechanics and Materials Vols.592-594 (2014) pp 1526-1533 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.592-594.1526 Effects of Water-Diesel Emulsion on the Emission Characteristics of Single Cylinder Direct Injection Diesel engine - A Review Raj Kumar Gupta1, a, K.A.Sankeerth2,b, T.Karthikeya Sharma3,c, G. Amba Prasad Rao4,d and K. Madhu Murthy5,e 1 M.Tech. student, Dept. of Mechanical Engineering, NIT Warangal, India 2 B.Tech student, Dept. of Mechanical Engineering, KITS Warangal, India 3 Research Scholar, Dept. of Mechanical Engineering, NIT Warangal, India 4,5 a Professor, Dept. of Mechanical Engineering, NIT Warangal, India
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[email protected] Keywords: Diesel engine, Water-Diesel emulsion, NOx emission, PM emission, micro explosion; Abstract. Diesel engines generate undesirable emissions during the combustion process. Various control methods have been developed to reduce nitrogen oxides (NOx) and particulate matter (PM) emissions from diesel engines so that the strict emission regulations can be fulfilled. Oxides of nitrogen (NOx) and particulate matter (PM) are the main pollutants from diesel engines and it has been proven that the method of introducing water with fuel to be a powerful and economical technique for reducing these pollutants. Water-Diesel emulsion is a new type of fuel which can be used in place of diesel fuel for the purpose to get the reduction in emissions of diesel engines. Many studies have been done on emulsion fuels and have concluded that this technique has the potential to significantly reduce the formation of NOx and PM and improve combustion efficiency. The emulsified fuel contains water and diesel fuel with some suitable surfactants to stabilize the system. An important aspect pertaining to water-diesel emulsion as a fuel for diesel engines is that it can be used without any modification in the existing engine. This paper presents an overview of recent progress in research of using water-diesel emulsion for the purpose of improving emission characteristics of a single cylinder direct injection diesel engine. Introduction: Various undesirable emissions are exhausted by internal combustion (IC) engines which affect the environment and cause various problems such as ozone depletion, acid precipitation, global warming and respiratory hazards etc. Therefore it is very important for the researchers to arrive at clean burning fuel to contribute in reducing the environmental problems and growth of global warming. Major emissions from the diesel engines include nitrogen oxide (NOx), particulate matter (PM), unburnt hydrocarbons (HC), oxides of carbons and other carbon particles or soot. Non-stoichiometric combustion, impurities in fuel and air and dissociation of nitrogen are the key reasons for these emissions. For the treatment of these pollutants, there are generally two ways: first-Treatment inside the cylinder and another treatment outside the cylinder or after treatment. In this review paper the main focus is on water-diesel emulsion technique which comes under first category and which has been proved that it is an effective and most universal method for simultaneous reduction of NOx and PM without any modification on the existing engine. According to the European Union Emission Standards (Euro V and Euro VI), the amount of emissions of NOx must be below about 28–68% and the amount of emissions of PM must be below about 80% respectively as compared to Euro IV standard, as shown in Fig.1: a and b. Thus diesel engines are thought to be the most attractive solutions to meet emission standards by applying different methods of reduction of NOx and PM. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 218.248.13.196-04/07/14,07:12:15) Water-diesel emulsion technique is one of the powerful method which has potential for simultaneous reduction of NOx and PM. (b) for dispersing one liquid into the other sufficient agitation must be applied and (c) a suitable emulsifying agent or a combination of emulsifier must be present in the emulsion [6]. when water-diesel emulsion is to be used in diesel engine. The conditions necessary to form a stable emulsion for either type of emulsions are: (a) the two liquids chosen must be mutually insoluble or immiscible in each other. Water-Diesel Emulsions: Diesel engines generate high combustion temperature and the high pressure unlike gasoline engines and thus particularly diesel engines are suitable for the concept of using water-diesel emulsion as a fuel. 1.Applied Mechanics and Materials Vols. The delivery capacity of the injection system is the limiting factor for using water-diesel emulsions. 1. the water present in the emulsion get evaporated in the combustion chamber and thus get converted into steam by absorbing the some heat from the combustion chamber as latent heat of vaporization during the compression stroke [3]. thus raising concern to resolve this contradictory problem of diesel engine emissions. This problem is predominant when neat diesel being used as fuel in diesel engine. Micro-explosion is the phenomena which accelerate the evaporation of fuel droplets in the emulsions and also it has ability to eject the fragments of droplets several millimetres away from limit of spray jet with a high speed and because of this an improvement in the proper mixing of air-fuel takes place resulting in improvement in the combustion efficiency. The micro-explosion phenomena is the theoretical aspect behind this when water-diesel emulsion is used as a fuel in diesel engine [4]. . Generally there are two types of emulsification techniques used: (i) two-phase emulsion (sometimes called primary emulsion) and (ii) three-phase emulsion (sometimes called multi-phase emulsion) [5]. the emulsion is known as oil in water emulsion. Fig. If water-diesel emulsions are to be used in a diesel engine without any modification in the existing engine then the maximum quantity of water use and the degree of reduction in NOx emissions both are limited to 10-20% despite engine may not be able to get its rated power. (a and b) Passenger cars NOx and PM emissions overview of past and future requirements [1. Using water-diesel emulsions as a fuel in diesel engine have shown several interesting effects like reduction in NOx and PM emissions and at the same time improvement in the combustion efficiency. 2 illustrates two-phase (O/W) emulsion fuel containing 50% water. 592-594 1527 Fig. 3 shows the physical structure of two-phase (W/O) emulsion. the emulsion is known as water in oil emulsion. Two-phase emulsion: The emulsion where water is present in continuous phase or dispersion phase and oil is the dispersed phase. Fig. The emulsion in which water forms dispersed phase and oil is present in continuous phase or dispersion phase. 2]. The mechanism for formation of NOx and PM is contradictory. It results in a decrement in the temperature inside the combustion chamber and due to which formation of thermal NOx is controlled. In general. for introducing water are: (i) Direct injection into the engine through separate injectors (DWSI). 14]. Illustration of two-phase (O/W) emulsion fuel containing 50% water [7]. The reaction time reduces due the effect of micro-explosion which facilitates the mixing process. 4. The techniques available for the preparation of three-phase emulsion are: (i) phase inversion. Fig. food or pharmaceutical manufacturing.02 mm and they are thermodynamically stable [11].2 to 50 mm and they are kinetically stable whereas the size of the particles in micro emulsions range from 0. Among these. using a single injector (HDWI). Three-phase Emulsion: Depending on the inner and outer phases.01 to 0. The peak flame temperature is the main cause of NOx emissions and after a number of investigations it has been found that water-diesel emulsion has an influence on reducing this peak flame temperature thereby reducing NOx emissions. The introduction of water with diesel has two contradicting effects: (i) the improvement of engine emissions because of occurrence of micro-explosion due to which the enhancement of fuel atomization occurs and thus leading to better fuel–air mixing. Illustration of three-phase (O/W/O) emulsions [10]. the water-diesel emulsions are found to be an appropriate method because this method does not require any modification in the existing engine [15].1528 Dynamics of Machines and Mechanisms. In macro emulsions the size of the particles ranges from 0. Oil-in-water-in-oil emulsions are applicable to use as a fuel in internal combustion engines while water-in-oil-in-water type emulsions are mostly used in cosmetics. Fig. 4 shows the illustration of three-phase (O/W/O) emulsions. (ii) Hybrid injection. Fig. the three-phase emulsions are classified as: (i) oil-inwater-in-oil and (ii) water-in-oil-in-water emulsions. reduction in maximum local temperature leads to reduced reaction rate. Industrial Research Fig. 3. The emulsions can also be classified into two types depending on the size of the droplets: (i) Macro emulsions and (ii) Micro emulsions. Very limited literature is available on the application of oil-in-water-in-oil emulsions as a fuel in internal combustion engines. two-stage emulsion is used most frequently. (iv) Waterdiesel emulsions (WDE). 2. and (ii) it decreases the calorific value of the mixture thereby reducing engine efficiency as energy is lost in the evaporation of water (larger than 10 times as compared to energy needed for the evaporation of diesel fuel) [12]. 2. Illustration of two-phase (W/O) emulsion with Physical structure [8]. Though all four methods . The relative merits and limitations of these four methods are summarised in table-1. These have a combined effect of reduction in the formation of PM and soot [13. Moreover. (ii) mechanical agitation and (iii) two-stage emulsion [9]. Among all the four methods of introducing water into combustion chamber of diesel engine proposed above. The major approaches reported so far. (iii) Fumigating the water into the engine intake air (FWIA). DWSI HDWI FWIA WDE Relative NOx reduction Poor Best Poor Good Effect on PM emissions Poor Best Poor Good Variability of water addition Good Poor Good Good Lubricating oil dilution High Low High Low Expenditure High Average Low High The amount of water injected in HDWI method can be quickly varied depending on engine load and speed which is very important in view of transient operating conditions and during cold start. Addition of water with diesel fuel improves the combustion efficiency. Emission Characteristics: Oxides of nitrogen (NOx): Many researchers observed that the water-diesel emulsion technique is an effective technique to reduce emissions of NOx and PM simultaneously in diesel engines. under part load conditions an increase in the emissions of CO and HC as well as BSFC are observed [1]. Similar observations were reported based on experimental and numerical studies [25]. The ignition delay is not increased in HDWI. .]. Comparing these techniques with respect to PM emission. 17]. However. The reduction has been attributed to the reduction in adiabatic flame temperature and vaporization of water in water diesel mixture [22. it has been found that water-diesel emulsion is most powerful and effective technique for the reduction of PM in a single cylinder diesel engine which is due to micro-explosion which helps in improvement of atomisation and mixing process [16.]. Reduction in the emission of NOx of about 29-37% was observed when 13% of water content by volume in the water-diesel emulsion as a fuel is used in the diesel engine [15]. The water present in the water-diesel emulsion weakens luminous flames and thus causes a reduction in the peak temperature during diffusion-controlled combustion phase which leads to a lower peak pressure and thereby reducing the level of emission of NOx in the diesel engines. Table 1: Comparison of water addition methods [18]. Studies on the spray development and combustion revealed a longer droplet penetration and wider cone angle with water-diesel emulsion fuel as compared to neat diesel fuel [21].Applied Mechanics and Materials Vols. 20. 23. because only diesel is injected at the beginning of the cycle and subsequent injection of emulsions resulted in retarded combustion and reduced engine noise. but increases ignition delay [13. 592-594 1529 have been experimented by researchers the conclusion shows that all of them are effective in reducing the NOx emissions. 24. Though these two methods are unfavourable for the above reasons significant reduction in PM emissions are observed. 19. The methods of DWSI and FWIA demands greater amount of water than water-diesel emulsion for comparable reduction in the emission of NOx for reasons of water not being injected directly into the combustion region and thereby becoming ineffective [18]. Effects of Water-Diesel Emulsion on Combustion Process: It has been observed by many researchers that water-diesel emulsion has a positive effect on combustion efficiency. The increase in the proportion of water in emulsified diesel fuel reduces NOx emissions. 0. 27. 6 shows the variation of PM emission with increment in the percentage of water in water-diesel emulsion technique with different engine speed [4]. Most of the researchers [15. Numerical and Experimental study observed reduction in the soot emission of 68% and 75% that when 10% and 15% respectively of water content by volume in the water-diesel emulsion were used [25. 23. [25] reported more reduction in the emission of HC with a water content of 10% as compare to a water content of 15% by volume.] reported an reduction of emission of PM as the water content in the emulsion increases. Experimental investigations were carried out to compare the effect of 8% and 5% water content by volume in the emulsion.54 and 3. 26. and 0.5% Tween 20. The test fuel EM1 with a composition of 91%diesel. Experimental investigation with 10% and 20% water content by volume reported the reduction of hydrocarbon (HC) in exhaust gases at all load conditions [23. All the researchers [4. Reduction in NOx emission with increase in Percentage of water in water-diesel emulsion [4]. 0. respectively [26].5% Span 20. 26.92 respectively [26].5% Span 20.1530 Dynamics of Machines and Mechanisms. 8% water.] reported an improvement in the reduction of emission of HC as the water content by volume in the emulsion increases but Samec et al. 25. while the test fuel EM2 had a composition of 94% diesel. Unburned Hydro-Carbons: Studies on the performance. Fig. They reported a drastic decrease in the emission of NOx and reported decreased values of 28. 5.48% with the emulsified fuels EM 1 and EM 2. 6. 25. 5% water. 5 shows how NOx emission reduces as the percentage of water in waterdiesel emulsion increases [4].5% Tween 20. Industrial Research Fig. and 0. Fig. Fig.]. Furthermore the reaction rate will reduce because of reduction in the maximum local temperature. The combined effects of these two reduce the formation of PM and soot [13. Particulate Matter (PM): Mixing of air-fuel improves due to micro-explosion phenomena and thus will reduce reaction time. 14]. . emission and heat release characteristics of direct injection diesel engine using diesel oil emulsion observed a reduction of 60-90% in hydrocarbon (HC) emissions [15].52% and 24. Experimental investigation for the purpose of comparing the effect of 8% and 5% water content by volume in the emulsion resulted in decreased smoke opacity of 7. 27]. 26. Variation in PM emission with increase in percentage of water in water-diesel emulsion for different engine speed [4]. M. Variation of CO2 emission with pure diesel and different water content in water-diesel emulsion at different engine speed [28]. References: [1] S. This occurs firstly because of reduction in peak cylinder temperature due to vaporization of water content in the water diesel emulsion and conversion of water into steam and secondary because of occurrence of micro-explosion phenomena in the combustion chamber atomization of droplets occurs properly and thus results in the improvement in the mixing process of air-fuel inside the engine cylinder. CO and CO2 emissions. :Impact of emulsified water/diesel mixture on engine performance and environment. H.344.M. . Al. Int. Emeishb S.J.400–420. Fig. Conclusion: The technique of using water-Diesel emulsion in place of conventional diesel in diesel engines has been shown to be an effective method which has a great contribution in the reduction of emissions of diesel engines specially it has potential of simultaneous reduction in NOx and PM which are the main pollutants of diesel engine. 1. Thus finally it can be concluded that as the amount of water content in the water-diesel emulsion increases the main pollutants of diesel engine (NOx and PM) decrease. Kalam. reduction in Carbon Monoxide (CO) and carbon dioxide (CO2) were reported at all load conditions when the percentage of water in the emulsion is increased [29]. No.A. J. Masum. p. Energy Conversion and Management 76(2013). Mishra R.Applied Mechanics and Materials Vols.7.Ragheba M. Abu-Zaidc M. 7 shows the variation of CO2 emission as the water content increases in water-diesel emulsion fuel at different engine speed. Fig. Ball AD: Water injection effects on the performance and emission characteristics of a CI engine operating with biodiesel. Renew Energy. of Thermal & Environmental Engineering Volume 3 (2011). Some researchers [28. The reason for the increment in the emission of CO and CO2 with increase in water content in the emulsion fuel is the excess oxygen in the combustion mixture. Masjuki. Increase in emission of CO2 with increase in engine speed and decrease with increasing the water content in water-diesel emulsion were observed [28]. Palash .1-7. [3] Badrana O. A. p. Al-Hasana M.333. Gu F.H.M. [2] Tesfa B. with an increase in the amount of water content in the emulsion. The delivery capacity of the injection system is the limiting factor for using high content of water in water-diesel emulsions as a fuel in the diesel engine. This kind of inconsistency in the obtained results is because of use of different engine setups and different methodologies used by researchers. It has also been observed that some of the researchers reported an increase in the HC. p. B. Abedin: State of the art of NOx mitigation technologies and their effect on the performance and emission characteristics of biodiesel-fueled Compression Ignition engines. 592-594 1531 CO and CO2: One of the experimental studies on Diesel engine performance and emission characteristics reported that an increase in the emissions of CO and CO2 with increase in percentage of water [19]. M. On the other hand. 29] reported decrease in the emission of CO2 whereas Lif et al. [19] observed increase in the emission of CO2. Sanjid. CO and CO2 emissions with increase in the amount of water content in the water-diesel emulsion but some researchers found a decrease in the HC. Abu-Rahmaa T. 37(2012). (1997). Performance. Yamin. M. [22] A. [15] Jamil Ghojel. Vienna. [8] Cherng-Yuan Lin.: Effects of diesel/water emulsion on heat flow and thermal loading in a precombustion chamber diesel engine. EPA report no 420-P-02-007.. Hamdan: Engine performance using emulsified diesel fuel. University College of Dublin. p.. Austria.82(2003). emission and heat release characteristics of direct injection diesel engine operating on diesel oil emulsion.pdf. Fuel Processing Technology. Part A: Recovery Utilization. Fuel. p. :Combustion study of stabilized water-in-diesel fuel emulsion. Aziz. p. Csanyi. 2132-2141. [23] Kannan. Khaled Al-Khaleefi. journal homepage: www. [19] Anna Lif. Udayakumar: NOx and HC emission control using water emulsified diesel in single cylinder diesel engine. Yatsufusa. 8. A. Kidoguch: Advantage of Using WaterEmulsified Fuel on Combustion and Emission Characteristics in European Combustion Meeting. Energy Conversion and Management. 26(2006). p. E.122–132. p. Energy Conversion and Management 45(2004). direct injection diesel engine using water fuel emulsions. Magnus Nyden. p. ARPN Journal of Engineering and Applied Sciences. Fuel. Abdul Karim. Vol. M. Ireland.4 (2009). [18]O’Sullivan. 149.M. M. No. 231–239. dspace.T. Komatsu Technical Report.84 (2005).S.A. Y. Nakagawa. and Y. 1565-1582. Krister Holmberg: Water-in-diesel emulsions and related systems. Ingemar Denbratt: Optical studies of spray development and combustion of water-in-diesel emulsion and microemulsion fuels. [20]Abu Zaid: Performance of single cylinder. Tohru Okazaki. 85(2006). [6] Gonglun Chen. Vol. Csoka. p. Ghannam. Vol. Alahmer. [13] Armas.1367–1375. Advances in Colloid and Interface Science Vol.A. of Pages 6. JFUE 7413 No. . 1708–1713. Elfeky¸ S. p. Applied Thermal Engineering.Y. Energy Sources. [7] Kin-ichirou Watanabe. A. Li-Wei Chen: Engine performance and emission characteristics of three phase diesel emulsions prepared by an ultrasonic emulsification method. M. p. Sven Andersson. p. Vol. Vol. 86(2005). p. 21(2001). Agudelo: Characterization of light duty diesel engine pollutant emissions using water-emulsified fuel. Kulchitskiy: Influence of the structure of water-in-fuel emulsion on diesel engine Performance.A. Mitsuru Ueno.edu/bitstream/ handle/1721.R.elsevier. December (2002) [5] Mohammed Yahaya Khan. 2 September (2013). I. and Environmental Effects. STA6D140. 593-600. M. Eros: Structural analysis of W/O/W multiple emulsions by means of DSC. Anna Lif. Daniel Tao: An experimental study of stability of oil–water emulsion.transtutors. T. 499– 508. Kumura. Model 5G. Fuel 89(2010).com/locate/fuel. Journal of Thermal Analysis and Calorimetry.697-705. 18-22.E. [12] Ali M.. No. [11]http://www.E. Martos. A. Shouhei Nagasaka : Komatsu’s low emission engine. 123-126(2006).1532 Dynamics of Machines and Mechanisms. [17]Selim. [10] Anita Kovacs. [14] T. Vol. J. Kuo-Hua Wang: The fuel properties of three-phase emulsions as an alternative fuel for diesel engines.Y. p. Rashid A. [16] Selim. (2009).1/9346/44421003. Sakhrieh. Vol.: Investigation of the NOx and PM emissions from a diesel engine operating on nanoemulsified fuels. Applied Thermal Engineering. using water emulsified fuel. Fuel. Attia and A. K. Z. [9] Cherng-Yuan Lin. 32(2009). C.aspx. [21] Raul Ochoterena.com/chemistry homework-help/surface-chemistry/emulsion. Fuel. vol. Magdolna Konya. Vol. Vol.mit. 256274.Isa M Tan Ftwi Yohaness Hagos :Current trends in water-in-diesel emulsion as a fuel –A review. Feher and I. Damon Honnery. 48(2002). 491-497. 51(2010) p. Ballesteros.1011–1018. Industrial Research [4] United States Environmental Protection Agency: Impacts of Lubrizol’s PuriNOx water/diesel emulsion on exhaust emissions from heavy-duty engines. 82(2005). [28] Ali Alahmer. (2013). p. ISSN: 2231-1963.doi. Influence of using emulsified diesel fuel on the performance and pollutants emitted from diesel engine. Robert W. Version 1. vol. Veeranjaneya L. Premkartikkumar Selvi Rajaram: An Experimental Investigation into Chosen Parameters of Diesel-Water Emulsion on Combustion Processes. Energy Conversion and Management 73(2013). p. 592-594 1533 [24] Babu. Sendilvelan.S.. Khan: Emission control by using water emulsified diesel in single cylinder diesel engine.Applied Mechanics and Materials Vols. Breda Kegl. Fuel. Venkatesh B. Volume 11(2011).0. ShaValli P. 361–369. [26] Pradeep Kumar Arokiasamy Remigious. International Journal of Advances in Engineering & Technology (IJAET). R. Mayor of London.1155/2013/764514. [25] Niko Samec. (2003). [29] Pradeep S. Annamalai Kandasamy. Global Journal of Research Engineering. p. Hindawi Publishing Corporation Journal of Chemistry Volume Article ID 764514(2013). Reddy. Issue 2.: Numerical and experimental study of water/oil emulsified fuel combustion in a diesel engine. Kumar.org/10. Dibble.V. http://dx. S. 2035–2044. Rajeswari B.: Reduction of pollutants in CI engine using emulsion fuels to reduce overall traffic-induced emissions. [27] Lucy Sadler: The air quality impact of Water-Diesel Emulsion Fuel (WDE) and Selective Catalytic Reduction (SCR) Technologies. 81(200).6. .