Water In Diesel Emulsion Research Articles

Fuel properties, performance, and emissions of water-emulsified diesel fuel in an IDI diesel engine

This paper aims to verify the possibility of utilising water-in-diesel emulsions (WiDE) as an alternative drop-in fuel for diesel engines. An 8% WiDE was produced to be tested in a four-stroke, indirect injection (IDI) diesel engine and compared to EN590 diesel fuel. An eddy current brake and an exhaust gas analyser were utilised to measure different engine parameters such as torque, fuel consumption, and emissions at different engine loads. The results show that the engine running on emulsified fuel leads to a reduction in torque and power, an increase in the specific fuel consumption, and slightly better thermal efficiency. The highest percentual increment of thermal efficiency for WiDE is obtained at 100% engine load, 5.68% higher compared to diesel. The emissions of nitric oxide (NO) and carbon dioxide (CO2) are reduced, but carbon monoxide (CO) and hydrocarbons (HC) emissions are increased, compared to traditional diesel fuel. The most substantial decrease in NO and CO2 levels was achieved at 75% engine load with 33.86% and 25.08% respectively, compared to diesel.

The investigation of lecithin and cocamide DEA Biosurfactant concentrations on emulsified biodiesel fuel stability, properties, and the micro-explosion phenomenon

Water-in-diesel emulsion (WIDE) fuel has been employed to reduce the emissions from diesel engines. Emulsified fuel in combustion chamber experiences secondary atomization, leading to micro-explosions that lower the combustion temperature and improve atomization. As a result, it reduces emissions and improves combustion efficiency. Emulsified fuels often face challenges with water separation over time; therefore, chemical surfactants have traditionally been used to prevent water separation from emulsified fuel. While biosurfactants offer a more environmentally friendly option compared to traditional chemical surfactants, there is a research gap regarding use of emulsified fuel with biosurfactant. This study aims to investigate the effect of biosurfactant concentration on emulsified fuel properties, stability, particles size, and microexplosions. In this study, six emulsified biodiesel fuels were developed with 10 % distilled water and biosurfactants (lecithin 63 % and cocamide DEA 37 %) ranging from 0.5 % to 3.0 %. The emulsion stability and properties of these fuels were examined. Further, Microscopy was employed to examine particle sizes distributions and suspended droplets hot plate technique with high-speed camera was used to record the micro-explosions. The results illustrate increase in biosurfactant concentration in emulsified fuel increases density and viscosity while reducing surface tension, droplet size, and micro-explosion peak temperature.

The Impact of Varying Mixing Rates in a Surfactant-Free Fuel Emulsion Mixer on the Efficiency and Emissions of a Diesel Engine

The research focuses on water diesel emulsion (WDE), a topic that has captivated researchers for an extended period. While previous studies predominantly employed surfactants to enhance mixing efficiency, their non-economic feasibility in transportation logistics has prompted a shift in recent investigations. This study presents experiments utilizing a cost-effective WDE comprising 15% water and a mixer devoid of surfactants to investigate the impact of mixer blade rotation on engine performance, fuel consumption, and NOx emissions. NOx emission tests were conducted under a constant engine speed of 2,000 rpm and a 75% load (3,23 kW). The optimal brake-specific fuel consumption (BSFC) for the 15% WDE fuel occurred at a blade rotation speed of 3,000 rpm, resulting in a 1% power reduction (from 4,41 kW to 4,38 kW), a 13.3% decrease in BSFC (from 694,98 gr/kW.h to 602,52 gr/kW.h), and a 30% reduction in NOx emissions (from 54 ppm to 38 ppm). This discovery holds promise for future advancements in green energy applications within the transportation sector.

Impact of water‐in‐diesel emulsion on compression ignition engine's emissions and its challenges—A detailed review

AbstractCompression ignition engines/diesel engines release greenhouse gases like particulate matter (PM), carbon monoxide (CO), nitrogen oxides (NOx), and, unburnt hydrocarbons which pose environmental and human health risks. Water‐in‐diesel emulsion (WiDE) has emerged as a cost‐effective alternative fuel for reducing the emission of these gases in diesel engines. This paper reviews the effectiveness of using emulsion fuel in engines to reduce harmful emissions as well as the challenges associated with WiDE, which include emulsion stability and corrosion. The review is based on available experimental results from various studies in the literature. While there are a few conflicting outcomes among researchers, the majority of results support the benefits of using WiDE in a compression engine as the PM and NOx emissions, significantly decreased. The decrease in NOx is a result of the flame reaching a lower peak temperature during combustion. The reduction in PM occurs as a result of the micro‐explosion process, which enhances combustion efficiency. Even though WiDE significantly reduces the environmental impact of diesel engines, this study also shows that WiDE faces stability problems and enhances the corrosion of materials. The development of a systematic methodology that can accurately measure emulsion stability, the in‐depth study of the impacts of surfactant dosage, water content and temperature on the corrosion behavior of metals in WiDE and also the development of anti‐corrosion intervention suggestions have been suggested based on the analysis of earlier research.

An Experimental Study on the Performance and Emissions of an 8% Water-in-Diesel Emulsion Stabilized by a Hydrophilic Surfactant Blend

Diesel engines are known for their excellent efficiency and are therefore used in a variety of applications. However, they are also one of the main sources of hazardous emissions such as nitrogen oxides (NOx) and smoke. Water-in-Diesel Emulsion (WiDE) is an alternative fuel that can possibly reduce some of the pollutant emissions without compromising engine performance. The surfactant formulation for WiDE usually follows the one used in water-in-oil (w/o) emulsions, where low hydrophilic–lipophilic balance (HLB) emulsifiers are preferred for better solubility in the diesel phase and stabilization at storage temperatures. However, by using a hydrophilic blend with a non-ionic surfactant, it is possible to develop an optimized formulation at higher fuel temperatures, which occur during an engine’s operating condition, achieving possibly higher benefits. Across the different speeds, the results for the emulsion show 7.57% mean improvement in specific fuel consumption (SFC), 19.14% mean improvement in thermal efficiency (TE), 5.54% mean reduction in carbon dioxide (CO2), 20.50% mean reduction in nitric oxide (NO) and 75.19% mean reduction in smoke levels. However, carbon monoxide (CO) and hydrocarbons (HC) emissions were higher, with a mean increase of 81.09% and 93.83%, respectively.

Effect of fuel injection pressure on the performances of a CI engine using water-emulsified diesel (WED) as a fuel

BackgroundThe choice of energy sources is essential for sustainable development to combat different environmental issues caused by the consumption of fossil fuels. Though diesel engines are considered more efficient and reliable than other internal combustion engines, they emit different harmful pollutants which are detrimental to human health and the environment. Researchers are trying to find suitable alternative fuels for diesel engines with lower pollutant emissions and without much compromise in the efficiency of the engine. In this regard, water-emulsified diesel (WED) may be considered to be one of the most suitable alternative fuels. It is expected that the entire world will use electric vehicles in the long term. However, the complete replacement of IC engines in the near future is not feasible. In fact, different European countries have targeted to ban the use of diesel engine cars before the middle of the twenty-first century. Prior to that date, hybrid vehicles will be more popular and diesel engines will continue to play an important role. Hence, research involving improvements in diesel-operated IC engines is still relevant.MethodsAn experimental investigation was carried out using WED containing 10% water by volume as a fuel in a diesel engine at four different fuel injection pressures. The WED was prepared using an ultrasonicator.ResultsWith the increase of injection pressure, peak net heat release rate and in-cylinder pressure are found to have increased. Brake thermal efficiency is also found to have improved at higher injection pressure. The maximum efficiency was recorded when a WED at 210 bar of injection pressure is used, and it is about 3.3% higher than the maximum efficiency achieved when using normal diesel at the same pressure of fuel injection. At a higher load, neat brake-specific fuel consumption is found to be less compared to neat diesel, when only the amount of diesel contained in the emulsion as a fuel is considered. Maximum reduction in both NOx and smoke emission by using WED is recorded at 210 bar, and the average reductions are determined to be 32.6% and 51.9%, respectively.ConclusionsWED can be used as an alternative fuel for existing diesel engines without any retrofitting and with significant reduction in the emissions of pollutants compared to normal diesel fuel. It can also be concluded that at higher injection pressure, the combustion, performance and emission characteristics of compression ignition engines are improved when using emulsified diesel.

Investigating the Combined Impact of Water–Diesel Emulsion and Al2O3 Nanoparticles on the Performance and the Emissions from a Diesel Engine via the Design of Experiment

This study aims to assess the impact of the water ratio and nanoparticle concentration of neat diesel fuel on the performance characteristics of and exhaust gas emissions from diesel engines. The experimental tests were conducted in two stages. In the first stage, the effects of adding water to neat diesel fuel in ratios of 2.5% and 5% on engine performance and emissions characteristics were examined and compared to those of neat diesel at a constant engine speed of 3000 rpm under three different engine loads. A response surface methodology (RSM) based on a central composite design (CCD) was utilized to simulate the design of the experiment. According to the test results, adding water to neat diesel fuel increased the brake-specific fuel consumption and reduced the brake thermal efficiency compared to neat diesel fuel. In the examination of exhaust emissions, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in the tested fuel containing 2.5% of water were decreased in comparison to pure diesel fuel by 16.62%, 21.56%, and 60.18%, respectively, on average, through engine loading. In the second stage, due to the trade-off between emissions and performance, the emulsion fuel containing 2.5% of water is chosen as the best emulsion from the previous stage and mixed with aluminum oxide nanoparticles at two dose levels (50 and 100 ppm). With the same engine conditions, the emulsion fuel mixed with 50 ppm of aluminum oxide nanoparticles exhibited the best performance and the lowest emissions compared to the other evaluated fuels. The outcomes of the investigations showed that a low concentration of 50 ppm with a small amount of 11 nm of aluminum oxide nanoparticles combined with a water diesel emulsion is a successful method for improving diesel engine performance while lowering emissions. Additionally, it was found that the mathematical model could accurately predict engine performance parameters and pollution characteristics.

Research on technological innovation and application of modern diesel engines

Diesel engines have been instrumental in driving industrial advancement. This paper provides an in-depth analysis of the evolution and application of diesel engine technology across various sectors, set against the backdrop of the global energy crisis and swift technological progress. The research emphasizes technological breakthroughs like turbocharging and common rail fuel injection, which have been pivotal in augmenting combustion efficiency and reducing environmental impact. The potential of alternative fuels, such as biodiesel, synthetic diesel, and water-emulsified diesel, in curbing emissions and bolstering combustion efficiency is also critically assessed. The diverse applications of diesel engines, spanning marine vessels to aviation, are explored, highlighting the adaptability of these engines to evolving environmental norms and market needs. The paper further investigates strategies to enhance thermal efficiency and performance, spotlighting innovative combustion methods like HCCI and RCCI. The pivotal role of accurate fuel injection control and injector design in refining combustion quality is also accentuated. In summation, while the study underscores the persistent relevance of diesel engine technology amidst modern challenges, it also advocates for sustained innovation to harmonize performance with environmental concerns. The prospective trajectory for diesel engines might encompass an amalgamation of traditional and novel energy solutions to address shifting energy and emission standards.

Performance, emission, combustion, exergy, exergoeconomic and sustainability analyses of EGR incorporated CI engine fuelled with areca nut husk nano-additive dosed plastic oil–water-diesel emulsion blend

This first-of-a-kind research emphasizes the influence of exhaust gas recirculation (EGR) on engine characteristics, and exergy, sustainability, and exergoeconomic aspects of compression ignition engine, powered by plastic grocery bag-extracted plastic oil-diesel-water emulsion blend dosed with bio-nano-additive extracted from areca nut husk (D10EPO-15 ppm). Three EGR rates (5%, 10%, and 15%) were incorporated at varying engine loads. At 100% load, the EGR incorporation reduced the peak heat release rate and peak pressure up to 6.5 and 5.6%, respectively, in comparison to the base fuel without EGR. Up to 5.2 and 9.1% reduction in exhaust gas temperature and nitrogen oxide emission (NOx) was noticed with the EGR incorporation. However, carbon monoxide (CO), hydrocarbon (HC), and smoke emissions increased with the EGR incorporation. Nevertheless, considering the overall characteristics, 5% EGR was the most suitable one to have a lower NOx (3.4%) with a minimum penalty on CO (4.3%), HC (5.4%), and smoke (3.6%) emissions as well as fuel consumption (3%), at full load. Amongst the three EGR rates, 5% EGR incorporation also has the highest exergy efficiency (20.9%) and sustainability index (1.26). Exergoeconomic analysis also revealed the favorability of 5% EGR, and at full load, 5% EGR showed the lowest specific exergy cost inflow rate (0.8957 $/hr), the lowest specific exergy cost rate for shaft work (75.27 $/GJ), the lowest relative cost difference (3.99), and the highest exergoeconomic factor (9.95%).

Characterization of Spray Field for Water-Emulsified Diesel Using a Pressure Swirl Atomizer Under a Nonreacting Environment

Abstract Employing a mixture or an emulsion of water and diesel fuel is considered a way to reduce gas emissions such as NOx and soot in a gas turbine. This study presents detailed experimental results on the spray characteristics of a water–diesel emulsion injected by a pressure swirl atomizer with a 90-degree spray angle and a flow number of 0.58 under a nonreacting environment at high pressure and temperature conditions. Acquiring these data is a key step when configuring a combustor that will employ emulsified fuels. In addition, this study seeks to confirm that the emulsion stays intact when it gets sprayed into the combustor. Furthermore, this study attempts to understand if a water–diesel emulsion prepared by a sonicator improves fuel atomization as compared to a water–diesel mixture prepared by a static mixer, i.e., not a proper emulsion. Tests are conducted in a high pressure and temperature testing facility at two ambient pressures and three ambient temperatures and the water to diesel ratio (W/D) is varied from 11% to 100% by mass. Phase Doppler Particle Anemometry (PDPA) is employed to measure the spray characteristics. Through a backlit high-speed photography, overall spray patterns over different test conditions are visualized. Mie-scattering and planar laser-induced fluorescence imaging are utilized to visualize the mixture field. In general, the results indicate that emulsion stays intact as it gets sprayed into the combustor; and emulsion is a better solution to reduce emissions than a statically mixed mixture.

Wavelet analysis of combustion characteristics and numerical validation of CI engine with novel water emulsified fuels

This study examined the dependability of running a diesel engine on a novel water-emulsified diesel fuel with prolonged phase stability investigation. In order to develop a stable water emulsified fuel, experiments were conducted to standardize the composition ratios. The water-in-diesel emulsions were prepared using the surfactant named “Propylene Glycol Monostearate” along with Tween80 and Octanol was also chosen as co-emulsifier in order to enhance the phase stability. Using water-emulsified diesel fuel with the designations E0, E10, E20, E30, E40, and E50, the combustion stability using statistical and wavelet method were assessed on a 1-cylinder, 4-stroke CI engine. Even after being prepared for 100 days at room temperature, all water-in-diesel emulsions were discovered to be stable and homogenous. Moreover, to validate the combustion metrices such as in-cylinder pressure and HRR, a MATLAB-based single-zone thermodynamic model was developed. The combustion stability analyses using statistical method showed that the COV was found below 5 % at all loading conditions except E0 emulsion fuel whereas, the wavelet approach revealed that the E0 emulsion fuel's wavelet power spectrum (WPS) result showed a major intensity variance at high frequencies and lower frequencies for other emulsions and diesel 25 and 50 % loading condition. The analysis of the Global Wavelet Spectrum (GWS) results revealed that E0 exhibited higher peak power compared to diesel and other test fuels at 25 % and 50 % load conditions. The WPS and GWS results for E30 and E50 emulsion showed a similar trend as diesel fuel at all tested loading conditions implying a stable combustion with water-emulsified diesel. On the other hand, the prediction model anticipated the numerical values and was computed to be in strong conformity with the outcomes of the experiment. All numerical values lay within 95 % of the prediction band in regression analysis with an R2 value of 99.8 % and standard error (S = 0622) suggesting strong significant data and a better thermodynamic simulation model. In conclusion, PGM + Tween 80 could be used as a potential emulsifier to prepare stable water-in-diesel emulsion and Wavelet analysis proves to be a valuable tool for evaluating the cyclic variation observed in engine combustion. Additionally, the thermodynamic model is capable of providing accurate predictions of the engine combustion parameters.

Performance and emissions of water-emulsified diesel fuel in an IDI diesel engine under varying engine load

This paper aims to verify the possibility of utilising water-in-diesel emulsions (WiDE) as an alternative drop-in fuel for diesel engines. An 8% WiDE was produced to be tested in a four-stroke, indirect injection (IDI) diesel engine and compared to EN590 diesel fuel. An eddy current brake and an exhaust gas analyser were utilised to measure different engine parameters such as torque, fuel consumption, and emissions at different engine loads. The results show that the engine running on emulsified fuel leads to a reduction in torque and power, an increase in the specific fuel consumption, and slightly better thermal efficiency. The highest percentual increment of thermal efficiency for WiDE is obtained at 100% engine load, 5.68% higher compared to diesel. The emissions of nitric oxide (NO) and carbon dioxide (CO2) are reduced, but carbon monoxide (CO) and hydrocarbons (HC) emissions are increased, compared to traditional diesel fuel. The most substantial decrease in NO and CO2 levels was achieved at 75% engine load with 33.86% and 25.08% respectively compared to diesel.

Execution and emission characteristics of automotive compression ignition engine powered by cerium oxide nanoparticles doped water diesel emulsion fuel

The rising consumption of oil and air pollution in developing countries compelled us to seek suitable alternative fuels for the existing compression ignition engines used in power generation, transportation, and industrial sectors, all of which play a strong role in the development of the nation's economy. Moreover, rising demand and consumption also causes a huge impact on our economy as we are dependent on other nations to cater to our needs as domestic production fails to fulfill the present requirement and leads to huge import bills that affect the ordinary man. A water/diesel (W/D) emulsified formulation helps to diminish the engine exhaust discharge without compromising the engine’s performance. The current task experimentally evaluates the execution and discharge characteristics of cerium oxide nano-particles doped water diesel emulsion fuel viz E15, E15CeO2(40), E15CeO2(60), and E15CeO2(80) on multi-cylinder automotive compression ignition engine at steady 1650 rpm, under variable test load situation. Mechanical stirring was used to make E15 water diesel emulsion fuel, whereas ultrasonicator and mechanical stirrer were used to make E15CeO2(40), E15CeO2(60), and E15CeO2(80) blends. Surfactants span 80 and tween 80 were used. The concentrations of cerium oxide nanoparticles in emulsion fuel samples were 40, 60, and 80 ppm, respectively. The characteristics like thickness, flash point, and heating value of test fuels were evaluated and reported within the range as specified by governing standards. The execution and discharge characteristics of various emulsion fuel samples were compared to standard diesel. At maximum load, cerium oxide doped fuels greatly improve engine performance while lowering environmentally harmful engine pollutants such smoke opacity, NOx, carbon monoxide, and hydrocarbon emissions by 40.27%, 33.60%, 30%, and 18.75%, respectively.

Effect of injection strategy and water content on water emulsion fuel engine for low pollutant compression ignition engines

Diesel–water emulsion (DWE) is a low pollutant fuel technology that can be applied immediately to powertrain transition period. There are many previous studies on engine performance based on application of DWE; however, studies on analyzing the effect of injection strategy are limited. Therefore, in this study, two types of DWEs with different water content manufactured in-house were applied to a conventional diesel engine. The effect of water content and injection timing was then analyzed and an optimal injection strategy was proposed. When the water content of DWE increased and injection timing was retarded, the nitrogen oxides (NOx) emission decreased. When the water content of DWE increased and injection timing was advanced, particulate matter (PM) emission decreased; however, when the water content was 20 wt% or more, PM emission was almost non-existent. Coefficient of variance of indicated mean effective pressure (CoVIMEP) was maintained below 2% even after increase in the water content and adjustment in injection timings under test conditions. PM emission is more influenced by water content of DWE than by injection timing. Therefore, to optimize pollutant emissions from DWE, delaying injection timing as much as possible is advantageous even if PM emissions increase slightly.

Unveiling the status of emulsified water-in-diesel and nanoparticles on diesel engine attributes

Due to the obvious increase in the environmental and human health concerns produced by diesel engines, there has been a lot of interest in ecologically friendly diesel fuels. Current research and development efforts are focused on water-in-diesel emulsion (WiDE) fuels, which have the potential to reduce nitrogen oxide (NOx) and particulate matter (PM) emissions while enhancing performance and allowing for more efficient energy development in a cleaner environment using existing diesel engines. The current topic is concerned with the WiDE fuel principle, emulsification stability, physio-chemical attributes, latest trends in emulsion fuel, the impact of WiDE fuel on engine attributes and the barriers to commercialization of emulsified fuel. Furthermore, the importance of nanoparticle additives in WiDE, nano-fuel formulation, and their impact on engine attributes are explored.

Study of Performance and Emission Characteristics DI Diesel Engine using Diesel-Water Emulsion

Study of Performance and Emission Characteristics DI Diesel Engine using Diesel-Water Emulsion

Cow-urine emulsified diesel fuel: preparation, stability, and rheological study for diesel engine application.

Water-diesel emulsion fuel has been found as a prominent alternative fuel by various researchers. Alike this technology, cow-urine (Bos indicus urine) emulsified diesel fuel (GMD emulsion) has been explored in this study. Making of homogeneous and stable emulsion is a crucial aspect in this approach while maintaining the diesel standards. Hence, the applicability of this fuel has been examined based on physicochemical properties for diesel engine application. The stability was assessed by creaming index, droplet size, Pdi, and interfacial tension. The minimum droplet size (278nm) and 0.282 Pdi was obtained with 5.72 HLB value, 4% (v/v) surfactant, and 10% (v/v) of cow-urine through ultra-sonication. The optimized 10% GMD emulsion was found stable for more than 80days. Viscosity and density of the fuel got increased with cow-urine and surfactant; however, they found within the standard limits. The physicochemical analysis exhibited the feasibility of the GMD emulsion for diesel engine application.

The effect of different in-line mixers producing emulsifier-free bio-diesel emulsion on the diesel engine combustion performance and exhaust emission

The energy crisis that the world facing right now causes researchers all over the world to opt for alternative fuels. Alternative fuels such as water in diesel emulsion gained attention in various studies due to their performance and capability in reducing harmful emissions such as NOx and PM. A new concept was introduced to make water in diesel emulsion without using a surfactant through a device called Real-Time Non-Surfactant Emulsion Fuel Supply System (RTES) and directly supply the fuel to the engine. This real-time emulsification concept requires a strong mixer, however, it consumes high energy. Thus, this study focused on the effect of different in-line mixers producing emulsifier-free bio-diesel emulsions on stability, diesel engine combustion, performance, and exhaust emission. The original RTES consists of a high shear mixer and ultrasonic mixer, while a new parameter for RTES (RTES-SM) is the high shear mixer and static mixer. The effect of the different inline mixers of RTES and RTES-SM was tested on the stability testing, engine dynamometer under various loading of 2 kW, 4 kW, and 6 kW, and real vehicle testing. The water percentage was set in the range of 7–10 %. Overall, the RTES showed better results on stability and engine dynamometer, but on real vehicle testing, the result is comparable to RTES-SM. Thus, this new concept of an inline mixing system of non-surfactant biodiesel emulsion (RTES-SM) showed better energy efficiency, promising results in real vehicle testing, and potential options in emulsion mixing technologies.

Experimental investigation on impact of water in diesel emulsion in a single-cylinder research diesel engine

The current study focuses on assessing the impact of water-emulsified fuel on single-cylinder diesel engine. The effect of water concentration, homogeniser speed and surfactant concentration on the stability of water in diesel emulsion is studied. The performance, emission, and combustion analysis have been carried out by varying compression ratio, injection timing, and injection pressure. It is noted from stability analysis that for 10% water at 15,000 RPM homogeniser speed, 1% surfactant mixture is the optimal parameter to achieve stability of WD emulsion. Ignition delay period and combustion duration increase as water concentration is increased in the emulsion. At a compression ratio of 18, injection timing 23bTDC and pressure 210 bar show reduced carbon monoxide, hydrocarbon, oxides of nitrogen, and smoke emission by 8.3%, 8.57%, 21.25%, and 43.07%, respectively, compared to standard diesel. The injection pressure of 250 bar shows enhanced brake thermal efficiency compared to 210 and 230 bar.

Stability characteristics according to cumulative time after manufacturing of water emulsion fuel prepared by porous membrane method for low-pollutant engines

Diesel water emulsion (DWE) is an alternative fuel that can simultaneously reduce nitrogen oxides (NOx) and smoke. Studies on reducing pollutant emissions by applying DWE to internal combustion engines have been ongoing, but there have been no studies on the stability of manufactured DWE. To verify the pollutant emissions performance of DWE, total hydrocarbon (THC), NOx, and Smoke emissions were measured by converting fuel of a conventional diesel engine. When DWE was applied, NOx and THC were reduced slightly, and smoke was greatly reduced. Thereafter, 12 types of DWE were manufactured according to water content and surfactant type, and the stability according to the cumulative time after manufacturing was evaluated. The stability was evaluated by measuring the mean water droplet diameter, water droplet diameter distribution width, water droplet cumulative distribution, and water droplet diameter trend. When an appropriate surfactant was used during the manufacturing, there was no difference in the stability according to the water content. It was confirmed that it is most advantageous to use Span 80 in the case of refueling after manufacturing DWE in advance, such as in automobiles, and that using Polyglyceryl 4-opleate is advantageous for manufacturing small mean water droplet diameters in a short time.