Diesel Combustion Process Research Articles

The Influence of Injector Nozzle Diameter on High-Density and Lean Mixture Combustion in Heavy-Duty Diesel Engines

In order to improve the fuel economy of heavy-duty diesel engines under high-load conditions, based on the combustion pathway model, it is proposed that the proportion of lean mixture with 0 < Φ < 1 is the most important spray characteristic affecting the overall diesel combustion process. Answering the question of how to increase the proportion of lean mixture inside the spray is the key to achieving the efficient and clean combustion of diesel engines. This paper investigated the mechanism of injector nozzle diameter on the in-cylinder air–fuel mixture and combustion process based on a high-density and lean mixture characteristic combustion strategy. The experimental results show that with an increase in nozzle diameter, the peak pressure and instantaneous heat release rate significantly increase, the combustion duration is shortened by about 20%, and the heat release becomes more concentrated. At 1200 rpm and IMEPg~2.3 MPa conditions, the indicated thermal efficiency increases by 1.3%, reaching a maximum of 51.5%. The numerical simulation results show that with the increase in nozzle diameter from 0.169 mm to 0.218 mm, the spray ejection momentum per unit time increases by 30%, the momentum transferred to the air by the spray increases, the oxygen transport process becomes more intense, and the air entrainment mass during the spray free development stage increases by 42%. The proportion of lean mixture inside the spray throughout the entire spray development process increases, resulting in an increase in the heat release rate of the lean mixture, making the overall combustion more intense and concentrated.

Research of the combustion process in a tractor diesel engine when operating on alcohol and vegetable oil

BACKGROUND:Tractor diesels are widely used in agriculture, industry and transport due to their high efficiency, reliability, manufacturability and economy. Nevertheless, the ever-increasing tractor fleet is one of the main causes of environmental pollution and the increase in the consumption of petroleum motor fuel. The paper substantiates the use of an alternative fuel, suitable in its physical and chemical characteristics and properties for efficient and environmentally friendly combustion in a tractor diesel, such as ethanol and rapeseed oil. AIMS:Research of the combustion process in a tractor diesel engine operating on ethanol and rapeseed oil, establishment the dependencies of the influence of tractor diesel operating modes on the combustion process indicators and determination of their numerical characteristics. METHODS:An experimental sample of a tractor diesel engine was converted for operation on ethanol and rapeseed oil. Ethanol was used as the main fuel and was ignited with a jet of rapeseed oil entering the diesel combustion chamber. Ethanol has a lower calorific value compared to diesel fuel, therefore, there was a need to determine the optimal cyclic supply of the ignition portion of rapeseed oil and to study the indicators of the combustion process. RESULTS:The results of experimental studies of the effect of the use of ethanol and rapeseed oil as a pilot fuel on the indicators of the combustion process of tractor diesel are presented. The optimal value of the cyclic supply of rapeseed oil has been determined, a decrease in the value of which from the optimal value leads to an increase in exhaust gas temperature, specific effective and total fuel consumption, worsens the combustion process, while an increase of it worsens the environmental performance of a tractor diesel engine, including the smokiness of exhaust gases. The results of scientific research on the determination of optimal installation angles of advance injection of ethanol and rapeseed oil are presented. CONCLUSIONS:The complete replacement of petroleum diesel fuel with alternative fuels has been achieved without making significant changes to the design of a tractor diesel engine, improving its environmental characteristics while maintaining power indicators at the level of a serial diesel. On the basis of the conducted studies of the operating process of a tractor diesel engine on ethanol and rapeseed oil, the dependencies of the influence of its operating modes on the indicators of the combustion process are established and their numerical characteristics are determined.

Optical diagnostic study of internal and external EGR combined with oxygenated fuels of n-butanol, PODE3 and DMC to optimize the combustion process of FT synthetic diesel

With the introduction of carbon neutrality target, Fischer-Tropsch (FT) synthetic fuels are coming back into the limelight as a kind of carbon–neutral fuel. However, the mismatch between the overly high cetane number (CN) and the relatively low vaporability of FT synthetic diesel is unfavorable to the soot emission control, which will make it difficult to meet more stringent fuel consumption and emission regulations in future applications. To investigate the potential of oxygenated fuels combined with different exhaust gas recirculation (EGR) introduction schemes to achieve high-efficiency and clean combustion of FT synthetic diesel, an optical diagnostic study was carried out based on high-speed photography and the two-color method. The results show that all three kinds of oxygenated fuels could suppress soot emissions via self-carrying oxygen and adjusting the physicochemical properties of the fuel blend. Compared with the combustion characteristics of FT synthetic diesel, the flame area and luminosity of oxygenated blends are reduced, and the in-cylinder temperature and soot KL factor are lowered. Among them, n-butanol exhibits a greater capability of soot control compared to polyoxymethylene dimethyl ethers (PODE3) and dimethyl carbonate (DMC). In addition, introducing internal and external EGR to the engine fueled by n-butanol/FT synthetic diesel blend shows that with the increase of EGR rate, the external EGR exhibits a gradually stronger inhibiting effect on the heat release process and soot KL factor, while the internal EGR exhibits an inhibiting and then promoting effect. Moreover, the high ratio internal EGR shortens the ignition delay (ID) significantly due to the strong heating effect, which is unfavorable to the control of soot emission. The combination of oxygenated fuels and internal/external EGR could effectively optimize the combustion process of FT synthetic diesel and inhibit soot generation, but the EGR rate needs to be controlled within a proper range.

New insights into the carbon chain structure of alcohol on the combustion of diesel surrogates using ReaxFF molecular dynamics simulations

Achieving clean and efficient combustion of diesel fuel is the main trend in the development of diesel engines in the future. Adding oxygen-containing alcohol to diesel fuel is an effective way to improve diesel combustion efficiency and reduce carbon smoke emissions, which is of great significance for reducing the consumption of traditional fossil fuels and reducing environmental pollution. In this work, the reactive molecular dynamics (RMD) simulations are conducted to compare the combustion of diesel without/with various alcohols, focusing on the intermediates and product distribution, oxygen consumption, ignition delay time, initial combustion pathways, and the related kinetics. It can be found that the addition of alcohols can significantly improve the combustion of diesel with the promoting order being n-pentanol > n-butanol > ethanol > cyclopentanol. The longer ignition delay of the diesel/ethanol is related to the lower cetane number of ethanol compared to other alcohols. The promoting combustion effect of alcohols can be attributed to higher reaction rate of their unimolecular bond dissociations and hydrogen abstraction reactions. In addition, the straight-chain alcohols have higher oxygen consumption and perform better in reducing soot than cyclic alcohols with the same number of carbon atoms. A significant decrease in activation energy is observed in the diesel/n-pentanol combustion system compared to the pure diesel combustion based on the RMD Arrhenius parameters from the first-order kinetic analysis. From the RMD simulations on the diesel/n-pentanol with different oxygen concentrations, it can lead to the conclusion that when the oxygen amount in the system reaches stoichiometric combustion, adding more oxygen does not produce a significant promoting effect on the diesel combustion process.

Dual combustion oxyhydrogen-diesel: Effects on internal components of engine

In Mexico, diesel is the second most used fuel, representing 28% of the national consumption, being the largest greenhouse gas emitter. In this work, the diesel engine can run smoothly in dual combustion mode diesel fuel/oxyhydrogen gas (OH2G) because OH2G fed to the diesel engine is limited by the volume available in the combustion chamber; this allows the timing and pressure in the combustion chamber to be kept within the limits of the engine y a combustion without detonations was observed, the existing infrastructure is used, and the consumption of diesel and contaminants emissions could be reduced. This study shows the effects produced in the engine combustion chamber by the dual combustion process of diesel fuel/oxyhydrogen after 500 h of operation. Two air-cooled mono-cylinder diesel engines with a displacement of 405 cm3 were operated; a D100 engine was operated with 100% diesel and OH210 engine in dual combustion (diesel fuel/oxyhydrogen) was operated. Both engines were maintained at 40% load with respect to their maximum power during 500 h OH2G was generated in situ by alkaline electrolysis, and a flow of 2 sL min-1 was fed through the intake port during the suction stroke of the engine. Visual analysis, weight and dimensions of the engine parts, metallographic analysis, oil analysis, and electrolyte drag were used to determine the effects on the component materials. For the engine with dual combustion, diesel fuel/oxyhydrogen, was no structural damage to the engine components, although a slight corrosion onset was observed in some components, such as the piston ring. Moreover, iron and aluminum in the oil were off-standard, which is attributed to the corrosion processes occurring because of water steam containing electrolyte traces being fed to the engine with the oxyhydrogen gas. This implies that more oil changes are necessary within a short period. Therefore, a more robust gas purification process will be implemented, and the injection system will be optimized.

An innovative method of ammonia use in a light-duty automotive diesel engine to enhance diesel combustion, performance, and emissions

This study investigated the novel method of ammonia use in a light-duty automotive diesel engine. An emulsification technique and ammonia solution are combined and adopted to prepare ammonia solution in diesel emulsion referred to as emulsified diesel-ammonia solution (EDAS) and tested under similar diesel combustion conditions. The ammonia solution concentration in EDAS was fixed as 10% by volume (EDAS10) with 2% v/v of surfactant to avoid excessive ammonia slip, corrosive effects, and oxides of nitrogen (NOx) formation. The aim of this study is to explore the effect of presence of hydrogen in EDAS10 on the diesel combustion process under high-pressure multiple injection strategies. Experiments were performed at low, medium, and high loads at the same combustion phasing (CA50) and total energy input as that of diesel to investigate the influence of EDAS10 on combustion, performance, and emissions. The start of injection of EDAS10 and exhaust gas recirculation rate was varied to attain the CA50. The combustion results showed that the EDAS10 blend had increased the heat release rate in the premixed combustion phase with shortened duration and decreased the heat release rate in the diffusion combustion phase compared to neat diesel operation. Double and triple injection of EDAS10 blend also increased the indicated and brake thermal efficiencies by about 4–7% than neat diesel operation. A decrease in 50–67% unburnt emissions, 8–13% decrease in smoke, and 7–19% increase in NO emissions, 2–10% increase in CO2emissions were observed with EDAS10 when compared to diesel operation.

Experimental study on wall heat transfer from diesel spray flame in two-dimensional combustion chamber operated with rapid compression and expansion machine (RCEM)

Heat transfer phenomenon in internal combustion diesel engine is one of problems to be solved. This study was conducted to investigate the relationship between diesel spray impingement, combustion processes, and heat loss using a rapid compression and expansion machine (RCEM). Furthermore, spray combustion and heat transfer processes were investigated using multiple injection strategies with a 6-holes injector. The amounts of diesel fuel used in the pilot, pre-injection, and main injection sprays were 3.964, 0.747, and 11.205 mg, respectively. Variations in common rail pressure conditions (30, 120, and 180 MPa) were applied to properly investigate spray evaporation, air–fuel mixture formation, and heat transfer in the combustion chamber. In addition, a local wall heat flux sensor was installed in the cylinder (head and liner) and piston cavity (upper lip, lip, and bottom) to measure the heat flux distribution, and a diffused backlight illumination method was used to visualize the spray and flame behavior in the combustion chamber and 2D piston cavity. The results showed that the impingement flame surrounding the cylinder head contributed to the highest magnitude and longest duration of the heat flux on the cylinder side owing to the spray flame velocity, impingement, and residence time. Meanwhile, the highest different temperature at cavity bottom induced more heat flux on the cavity side than that on the squish side. In addition, the higher injection pressure increased the spray momentum and spray tip penetration which led to a better air–fuel mixture, better evaporation rate, and less flame residence that contributed to reduce the accumulated heat loss in combustion chamber. Furthermore, a low common rail pressure was found to induce a greater difference in the accumulated heat flux ratio than a high common rail pressure which is owing to longer flame residence time in the combustion chamber. They were approximately 14% and 6% greater than that compared to the baseline common rail pressure which mean that a high common rail pressure contributes for the improving thermal efficiency in spray combustion.

Experimental study of the effect of HHO gas injection on pollutants produced by a diesel engine at idle speed

In this study, with the aim of reducing the energy consumption in the production of HHO gas for use in the combustion process of diesel fuel, different modes of gas production were investigated using electrolyzers. According to previous studies, the energy consumption rate of the electrolyzer to produce a high volumetric flow of HHO gas is very high. This high rate will restrict the use of equipment such as high-capacity batteries. The effects of HHO gas injection at the idle speed of the engine at a low temperature were evaluated. Because in this situation, the engine makes high air pollution. The results showed that the percentage of CO, CO2, HC, and NOX gases decreased by 66%, 33%, 38%, and 11%, respectively. On the other hand, the amount of O2 gas in the exhaust increased by 18%. These results were reported for HHO gas injection from 10 to 45 ml/s. The performance of Group Method of Data Handling (GMDH) neural network was desirable in modeling diesel engine pollutants. Because the Root-Mean-Square Error (RMSE) criterion for all evaluated gases is less than 0.32. The GMDH neural network was used for modeling the operation of the diesel engine with HHO supplemental fuel. The GMDH results showed that this artificial network can measure all engine exhaust gases. It can be used as a sensor and virtual simulator for this diesel engine with HHO supplemental fuel.

THE IMPACT OF A TWO-PHASE DIESEL FUEL PILOT INJECTION ON THE COMPRESSED NATURAL GAS AIR–FUEL MIXTURE COMBUSTION PROCESS IN A DIESEL ENGINE

Nowadays, there is a global trend towards the use of alternative fuels in order to reduce environmental pollution. For example, Compressed Natural Gas (CNG) has become more widely used around the world. The use of different fuels in engines affects the combustion process and efficiency, with the latter potentially being reduced by such means as, for example, the use of gaseous fuels in conventional diesel engines. Therefore, it is also important to know how CNG combusts in a diesel engine and how the combustion process can be improved. Consequently, the aim of the study is to give an overview of the effect of divided Diesel Fuel (DF) pilot injection on the combustion process of a naturally aspirated diesel engine using dual-fuel mode, with one fuel being DF and the other CNG. The focus of the article is on the commonly used engines on which the diesel injection system works regularly, and CNG fuel is injected into the intake manifold as an additional fuel. The engine DF quantity and injection timing are regulated by the acceleration pedal. The article provides an overview of the diesel and dual-fuel combustion process, and compare the DF and dual-fuel combustion processes. For this purpose, a test was carried out in order to measure the various involved parameters, such as the combustion pressure, torque, and fuel consumption. The results demonstrated that ignition delay does not significantly vary with the use of gas as a fuel source, and the maximum combustion pressure is actually higher with gas. The combustion is more rapid in dual-fuel mode and results indicate that when using dual-fuel mode on regular engines, it would be necessary to regulate the pre- and main-injection timing.

Calibration of 0-D combustion model applied to dual-fuel engine

To acquire a highly accurate 0-D combustion model of the Wiebe function, a genetic algorithm (GA) based on algebraic analysis is developed. By analyzing the in-cylinder combustion process of biodiesel and diesel, a new method is proposed for determining the number of Wiebe functions and the transition angle between premixed and diffusive combustion in dual-fuel engine. First, for different operating conditions, the number of required Wiebe functions and the initial value of Wiebe parameters are determined by algebraic analysis method. Then, genetic algorithm is applied to obtain the further optimized Wiebe parameters and finally compared with Levenberg-Marquardt (LM) algorithm on fitting precision. The algorithm is applied to a dual-fuel engine under the conditions of propeller performance. The results show that, based on the initial value of Wiebe parameters, the fitting process of both LM algorithm and genetic algorithm converges rapidly, the R2 of xb are all at a high level (larger than 0.997), but the RMSE values of genetic algorithm are all in a low range (smaller than 0.013). The fitting effect of genetic algorithm is obviously better than that of LM algorithm. Therefore, genetic algorithm based on algebraic analysis is an incredibly precise algorithm for structuring a 0-D combustion model.

Diesel blends with high concentrations of biodiesel and n-butanol: Effects on regulated pollutants and polycyclic aromatic hydrocarbons

Despite advances in alternative energy production (including electric vehicles and hydrogen fuel cells), fossil fuels remain ubiquitous and an ongoing threat to the environment. Alternative biofuels such as biodiesel and n-butanol have garnered substantial attention in recent years as additives to fossil diesel as a means to control emissions such as nitrous oxides (NOx) and carbon monoxide (CO). In addition, as biodiesel and alcohols do not contain aromatic hydrocarbons in their chemical structures, they provide potential additional advantages for reducing toxic emissions, including polycyclic aromatic hydrocarbons (PAHs); however, this is often only demonstrated for relatively low blend ratios (<20 %). In this study, the effects of neat diesel, waste oil biodiesel, and n-butanol blends on engine function, regulated, and unregulated emissions were investigated for blends containing 50/50 vol% diesel/biodiesel (D50B50), 50/25/25 vol% diesel/biodiesel/n-butanol (D50B25Bu25), and 50/50 vol% diesel/n-butanol (D50Bu50), in addition to neat standard road diesel (D100) and waste oil derived biodiesel (B100). In these blends NOx was reduced by up to 28.1 % relative to D100 for loads above idle, while increasing exhaust gas temperatures up to 33.5 % and increasing unburned hydrocarbons (HC) and CO by up to 84.2 % and 93.8 %, respectively. Measured against neat diesel, biodiesel and the diesel-biodiesel-butanol blend reduced PAH toxicity by up to 46.4 %, while diesel-biodiesel and diesel-butanol blends showed an increase up to 14.3% and 504%, respectively, due to higher concentrations of 5-ring PAHs. It has been concluded that in addition to fuel aromaticity, other factors such as fuel properties affecting the diesel combustion process (i.e. cetane number), can cause PAH formation.

Effects of metal-organic framework nanoparticles on the combustion, performance, and emission characteristics of a diesel engine

This study was set to use metal-organic framework nanoparticles in diesel fuel formulation for the first time. Zeolitic imidazolate framework nanoparticles were synthesized using a green technique at room temperature, characterized using various characterization techniques, and used in a diesel-water emulsion fuel at two different concentrations (15 and 30 ppm). The prepared fuel blends were tested in a diesel engine at various loads (25–100% of full-load operation). The effects of fuel composition and engine load were assessed on the behavior of the engine. The combustion and performance parameters of nano-emulsion fuel blends were analogous to those observed for diesel. Nano-emulsion fuels resulted in significantly lower nitrogen oxide emissions than diesel at engine loads up to 75% of full-load operation. Nano-emulsion fuels also markedly outperformed diesel in terms of smoke emission at full-load operation. More specifically, nano-emulsion fuels could result in a significantly lower nitrogen oxide than diesel fuel, with an average reduction of about 15%. These findings were achieved with a slight penalty on the unburned hydrocarbon emissions. The encouraging results obtained in the current preliminary study can serve as an invaluable starting point for future studies to attain a more environmentally friendly diesel combustion process using MOF nanoparticles.

Development of a reduced n-heptane/toluene/tetrahydrofuran mechanism for dual-fuel engine combustion prediction

Tetrahydrofuran (THF) is being proposed as a promising alternative fuel for internal combustion engines. However, the reaction chemistry of THF for multi-dimensional engine simulations has not been well established. In this study, a reliable n-heptane/toluene/THF mechanism was developed to simulate combustion of diesel and THF dual-fuel engine. Firstly, a reduced THF reaction mechanism was obtained by employing various mechanism reduction methods. Secondly, a combined mechanism was constructed based on decoupling methodology, which contained the reduced oxidation sub-mechanisms of n-heptane, toluene and THF, a reduced C2-C3 mechanism and a detailed H2/CO/C1 mechanism. Thirdly, the reaction rate constants of selected reactions involved in the combined mechanism were optimized and the newly developed reduced tri-component mechanism consisting of 65 species among 214 reactions. Subsequently, validations of the developed mechanism were performed using the previously published experimental results of ignition delay times in shock tubes, species mole fractions in laminar premixed flames and jet-stirred reactors, and laminar flame speeds. Meanwhile, dual-fuel engine experiments were conducted and new experimental data of in-cylinder pressure and heat release rate were also used to verify the developed mechanism. The validation indicates that the n-heptane/toluene/THF mechanism of this work can be applied for predicting the combustion process of diesel and THF dual-fuel engine.

A Comparison in Combustion Characteristics in a CVCC with Biodiesel Blends

This paper presents the comparison of combustion characteristics in a constant volume combustion chamber (CVCC) with alternative fuel biodiesel blends. To achieve this goal, a CVCC experimental was established, and the biodiesel was made from fish oil and was used as test fuel. The combustion process of diesel fuel (B0) and bio-diesel 10% (B10) will be investigated based on doing experiments with two conditions: air-fuel mixed before and after ignition timing. The influence of the oxygen concentration on the burning process is also being investigated. The results of the research show that the heat release rate of B0 is faster and higher than that of B10 in the case of air-fuel mixed before ignition timing. In the case of after ignition timing, these values are almost similar to B0 and B10.

Effects of Different Ethanol/Diesel Blending Ratios on Combustion and Emission Characteristics of a Medium-Speed Diesel Engine

In order to better evaluate the effects of ethanol/diesel blends on engine combustion and emission characteristics, we developed an engine cylinder model using the software CONVERGE combined with the program CHEMKIN. The model was validated experimentally. A modified chemical kinetic mechanism was used to calculate the combustion process of diesel fuel and ethanol for the diesel engine, including 154 reactions and 68 species. Furthermore, the influence of different ethanol proportions on diesel engine combustion and emission characteristics, including power, brake specific fuel consumption, brake thermal efficiency, cylinder pressure, cylinder temperature, nitrogen oxide (NOx), carbon monoxide (CO), and soot emissions, was also investigated. Our results showed that cylinder pressure and temperature increased with increased ethanol content. When the ethanol content increased to 20% at 100% load, the cylinder pressure increased by 0.46%, and the thermal efficiency increased by 3.63%. However, due to the lower calorific value of ethanol, the power decreased by 4.12%, and the brake specific fuel consumption increased by 4.23%. In addition, the ethanol/diesel blends significantly reduced CO and soot emissions. Compared with diesel, soot and CO emissions from the D80E20 at 100% load reduced by 63.25% and 17.24%, respectively. However, NOx emission increased by 1.39%.

EXPERIMENTAL STUDY OF DIESEL SPRAY AND COMBUSTION PROCESSES UNDER SPLIT INJECTION STRATEGY; PHENOMENA OBSERVATION FROM LATERAL SIDE OF A TWO-DIMENSIONAL PISTON CAVITY IN A RAPID COMPRESSION AND EXPANSION MACHINE

EXPERIMENTAL STUDY OF DIESEL SPRAY AND COMBUSTION PROCESSES UNDER SPLIT INJECTION STRATEGY; PHENOMENA OBSERVATION FROM LATERAL SIDE OF A TWO-DIMENSIONAL PISTON CAVITY IN A RAPID COMPRESSION AND EXPANSION MACHINE

Rapid Transformation of Furfural to Biofuel Additive Ethyl Levulinate with In Situ Suppression of Humins Promoted by an Acidic-Oxygen Environment

Sustainable production of biofuel additive ethyl levulinate (EL) from biomass-derived furfural (FF) is an interesting way owing to its application in improving the diesel combustion process without...

Noise emission of combustion engines and road vehicles - a historical review

This paper deals with the historical development of the noise emission of cars, trucks and their petrol and diesel engines; it focus on the European Union and the time period between 1910 and 2020. Combustion engines were and are important noise sources of road vehicles. Until around 1970 engine noise levels were increased strongly by higher speeds, by higher cylinder pressures and especially for truck engines by the introduction of the diesel combustion process. The noise emission was mainly caused by the drive train until the 1960ies for cars and until the 1970ies for trucks. Since then the development of acoustically more advantageous engines was forced by noise regulations and simultaneously enabled by technical advancements. As a consequence of the acoustical optimization of the engines the tire/road noise became dominant. Despite of the technical advancements the road noise stress of the population is still much too high. Therefor the necessary short-term reduction of noise stress has to be realized by regulatory measures.

Influence of Aromatic Contents in Low Sulphur Fuel on Particulate Formation and Oxidation Process in Diesel Combustion - Investigation of Soot Estimation Method with Radical Luminous Time Measurement

The IMO sulphur limit for ships' fuel oils has just started since 2020. In order to reduce sulphur concentration, it is predicted that LCO (Light Cycle Oil) fuels will be more commonly used as low sulphur base materials. However, aromatics in LCO fuel affect not only self-ignition but also combustion characteristics, especially soot emission. Therefore, it is important to evaluate combustion characteristics of aromatics in a simplified manner.

Developing Small Dual-Fuel Diesel Engine to Control Marine Pollution by Reducing NOx Emission for Application in Fishing Vessels

Using natural gas for fueling a ship growing extensively since environmental issues become one of the priorities in the shipping industry. The ship uses natural gas as the main fuel commonly called as a gas-powered ship. Gas has lower specific prices compare with any type of diesel fuel. But due to handling, storage, and distribution costs then gas prices for ships become higher even still a bit cheaper than diesel fuels. Besides prices, technically gas is cleaner so it may give the lower emission levels. Dual fuel technology is the best choice in occupied gas as ship fuel due to the existence of the IGF Code. Established Dual-fuel diesel engine is very expensive and available for big power capacity. This research develops a small dual-fuel diesel engine from a conventional engine with power less than 10 HP. The piston crown is a part of the engine that was modified so that the engine can use natural gas in the best performances as the conventional one. NOx as the most hazard emission in the diesel combustion process is controlled to be as the lowest as possible. The quality of air may be significantly affected by those small engine pollutions because of the large number of vessels in that dense environment in the typical fishery villages. In conclusion, the modified dual-fuel diesel engine capable of reducing NOx emission by up to 31% at a practical safe operation of 50% dual-fuel. The higher gas portion gives a lower NOx emission level.