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In the study, the effect of hydrogen addition with air taken from the intake manifold at different rates on performance and emissions in a single-cylinder, four-stroke diesel engine has been numerically investigated. The first and second law analyses of thermodynamics are performed for each hydrogen addition condition. Numerical analysis has been performed with ANSYS-Forte, energy and exergy calculations have been carried out according to the analysis results. The results of the analysis show that with the addition of hydrogen, CO emissions decrease while the engine performance and NOx emissions increase.
Biofuels such as ethanol have been used in internal combustion engines to reduce polluting emissions. However, some studies show that they affect engine performance due to their differences in thermophysical properties. Besides, pure ethanol has not been properly evaluated in compression ignition engines. Therefore, this work shows the results of an exergy analysis in a single cylinder compression ignition engine converted to spark ignition engine of varying compression ratio, operated with diesel, ethanol, and gasoline/ethanol blends, in different operating parameters. Tests were carried out on the engine without modifications operating diesel at a compression ratio of 17:1 and converted to spark ignition with 50%, 10% gasoline/ethanol blends and pure ethanol at compression ratios of 9:1, 12:1 at rotation speeds of 1500, 2100, 2600 and 3200 rpm. Under the experimental operating conditions, the results of the modified engine showed that the blend 50% and ethanol performs better by operating with 12:1 compression ratio, in relation to exergetic efficiency and environmental effect factor. Besides, the engine showed a better performance by becoming to spark ignition operating with ethanol and gasoline/ethanol blends.
A paradigm shift towards the utilization of carbon-neutral and low emission fuels is necessary in the internal combustion engine industry to fulfil the carbon emission goals and future legislation requirements in many countries. Hydrogen as an energy carrier and main fuel is a promising option due to its carbon-free content, wide flammability limits and fast flame speeds. For spark-ignited internal combustion engines, utilizing hydrogen direct injection has been proven to achieve high engine power output and efficiency with low emissions. This review provides an overview of the current development and understanding of hydrogen use in internal combustion engines that are usually spark ignited, under various engine operation modes and strategies. This paper then proceeds to outline the gaps in current knowledge, along with better potential strategies and technologies that could be adopted for hydrogen direct injection in the context of compression-ignition engine applications-topics that have not yet been extensively explored to date with hydrogen but have shown advantages with compressed natural gas.
Diesel engines are widely used in the world for trade and human transportation because of their efficiency and economical aspects. Approximately thirty percent of the greenhouse gases that cause global warming in the world are due to the transportation sector. The purpose of this study is to examine the effect of four-stroke single-cylinder diesel engine on combustion characteristics and exhaust gas emissions by changing intake valve lift distances. Combustion analysis and visualisation of analysis results at different valve lift values were applied with ANSYS-Forte, which is a commercial software, using computational fluid dynamics (CFD) for combustion system analysis and ANSYS-Chemkin which is used for reaction kinetics of combustion. Numerical results are shown that CO, CO2, NO, NO2 emissions, pressure and temperature with respect to crank angle. Numerical analysis results were compared with previous experimental data and parametric studies were applied based on verified model. The cylinder pressure and temperature values were found to be parallel with the data examined in the literature. The current study found that gross indicated power, indicated main effective pressure (IMEP) and combustion efficiency increase with the valve lift extension.
It has been shown that using fuel additives play an important role in enhancing the combustion
characteristics in terms of efficiency and emissions. In addition, free piston engines have shown
capable in reducing energy losses and presenting more efficient and reliable engines. In this
context, the objective of the present work is to investigate the effect of using Hydrogen as a fuel
additive in natural gas HCCI free piston engine. To this aim, two models have been iteratively
coupled: 1) the combustion model that is used to calculate the heat release of the combustion and
2) the scavenging model that is employed to determine the in-cylinder mixture state after
scavenging in terms of its homogeneity and species mass fractions and to obtain the finial
pressure and temperature of the in-cylinder mixture. In the former model, the 0-D approach
through Cantera toolkit has been considered due to the fact that HCCI combustion is very rapid
and the fuel-air mixture is well-homogenous, whereas in the latter model, 3D-CFD approach
through Ansys fluent software is considered to ensure precise calculations of the species
exchange at the end of each engine cycle. The effect of Hydrogen as a fuel additive has been
quantified in terms of the combustion characteristics (e.g., ignition delay, heat release rate,
engine overall efficiency and emissions, etc.). It has been shown that hydrogen addition reduces
ignition delay time, decreases the in-cylinder peak pressure, while allowing the engine to operate
with higher mechanical efficiency as it has high heat release rate, increases the NOx emission
levels of the engine, but decreases the carbon monoxide (CO) levels
In this paper, energy, exergy and economic evaluation of a single cylinder diesel engine fuelled with diesel fuel and two types of biodiesel-diesel fuel blends (i.e., B10 and B50) were conducted by evaluating experimental data. Experiments were carried out at five different engine speeds and full load conditions. Energy and exergy components of the engine were calculated and compared for each operating conditions and test fuels. Results obtained from biodiesel-diesel fuel blends were found to be better than neat diesel fuel in respect of both energy and exergy analysis. The maximum brake thermal efficiency and exergy efficiency of the test engine were found to be 40.41% and 37.83%, respectively, at 2000 rpm for B10. Also, the minimum exergy destruction occurred at 2000 rpm for all test fuels. However, from the point of specific fuel costs, B10 and B50 gave quite higher economic costs in compared to diesel fuel. Since fuel price per litre of biodiesel is quite higher than diesel fuel, higher biodiesel rates in the blend dominate increase in specific fuel costs even specific fuel consumption decrease.
Linear and nonlinear renormalization group (RNG) k-epsilon models are compared for the prediction of incompressible turbulent flows. The multidimensional finite-volume code KIVA-3 \ is used to explore the alternative models versus the standard k-epsilon model. Test cases include the classic backward-facing step and the confined co-flow jet flows. Our results suggest that the linear RNG k-epsilon model can yield significant improvements over the standard k-epsilon model for recirculatory flows, because of its less dissipative nature. While the nonlinear RNG k-epsilon model can also improve predictions compared to the standard k-epsilon model, its greatly increased cost compared to the linear RNG model renders it less attractive. However, for the case of shear flows, such as for confined co-flow jets, the RNG-based k-epsilon models are in less favorable agreement with experiments compared to the standard k-epsilon model. Overall, it is concluded that combining the claimed universality of the RNG-based k-epsilon model constants with the anisotropies introduced by the nonlinear k-epsilon model cannot enhance predictions of both recirculating and shear incompressible flows.
Recently, the increasing demand for energy requires the use of alternative fuels, especially in fossil fueled power systems. As a promising alternative fuel for next-generation diesel engines that utilize fossil fuel, hydrogen fuel is one step ahead due to its positive properties. In this study, the effects of hydrogen on the performance of a diesel engine have been numerically investigated with respect to different injection ratios and timings. The numerical results of the study for 25% load conditions on a single-cylinder, four-stroke diesel engine have been validated against experimental data taken from literature and good agreement has been observed for pressure results. Emission parameters such as NOx, CO and performance parameters such as cylinder temperature, pressure, power, thermal efficiency and IMEP are presented comparatively.
The results of numerical analyses show that the maximum pressure, temperature and heat release rate are observed with injection ratio of H15 and early injection timing (20° CA BTDC). Besides that, engine power, thermal efficiency and IMEP are greatly improved with increasing injection ratio and early injection timing. Although combustion chamber performance parameters improve with rising the hydrogen injection ratio, higher NOx emissions have also been detected as a negative side effect. Furthermore, while early injection timing increases diesel engine performance, it also causes an increase in NOx emissions. Therefore, precise determination of injection timing together with the optimum amount of hydrogen has revealed that it brings crucial improvement in engine performance and emissions.
Many applications use hydrogen addition and high-pressure fuel injection technology to improve combustion performance. In this study, spray atomization and combustion characteristics of a diesel fuel jet, under the injection pressure of 350 MPa, injecting into a constant volume combustion vessel filled with air-hydrogen mixture at the diesel engine relevant condition are investigated by simulation method. A simplified mechanism of the n-heptane (C7H16) oxidation chemistry mechanism consisting of 26 reactions and 25 species integrated with the Kéromnès-2013 hydrogen combustion mechanism and EDC combustion model are utilized to predict the diesel fuel spray auto-ignition and combustion. The ambient gas is the mixture of air and hydrogen range in volume fraction from 0% to 10%. The ambient temperature and pressure is set to 1000 K and 3.5 MPa, respectively. The results indicate that as the hydrogen volume fraction is 2%, the minimum overall droplet SMD (Sauter Mean Diameter) is approximately 0.95 μm, which is obviously smaller than that of the case with the conventional high injection pressure. In cases that H2 v/v% larger than 4%, the maximum gaseous temperature increased significantly up to 2700 K. There are two peaks in the temperature growth rate curves as the hydrogen fraction of 8% and 10%. The high temperature at the outer edge of the spray is clearly seen due to its high value when the hydrogen fraction is larger than 4%. The hot reaction layer is the main location of CO formation. The H, OH radicals are formed at the edge of the spray where the temperature is high. The hydrogen species obviously promotes the oxidation and combustion of diesel fuel.
Compared with traditional hydrocarbon fuels, hydrogen provides a high-energy content and carbon-free source of energy rendering it an attractive option for internal combustion engines. Co-combusting hydrogen with other fuels offers significant advantages with respect to thermal efficiency and carbon emissions. This study seeks to investigate the potential and limitations of multi-zone combustion models implemented in the GT-Power software package to predict dual fuel operation of a hydrogen-diesel common rail compression ignition engine. Numerical results for in-cylinder pressure and heat release rate were compared with experimental data. A single cylinder dual-fuel model was used with hydrogen being injected upstream of the intake manifold. During the simulations low (20 kW), medium (40 kW) and high (60 kW) load conditions were tested with and without exhaust gas recirculation (EGR) and at a constant engine speed of 1500 rpm. Both single and double diesel injection strategies were examined with hydrogen energy share ratio being varied from 0-57 percent and 0-42 respectively. This corresponds to a range in hydrogen air-equivalence ratios of approximately 0-0.29. The results show that for the single-injection strategy, the model captures in-cylinder pressure and heat release rate with good accuracy across the entire load and hydrogen share ratio range. However, it appears that for high hydrogen content in the charge mixture and equivalence ratios beyond the lean flammability limit, the model struggles to accurately predict hydrogen entrain-ment leading to underestimated peak cylinder pressures and heat release rates. For double-injection cases the model shows good agreement for hydrogen share ratios up to 26 percent. However, for higher energy share ratios the issue of erroneous hydrogen entrainment into the spray becomes more accentuated leading to significant under-prediction of heat release rate and in-cylinder pressure.
In this study, the change rules and influence mechanism of injection pressure and timing on exergy terms at different working conditions are investigated based on a turbocharged diesel engine test platform, a multi-dimensional simulation model and subsequent theoretical calculation. To have a comprehensive analysis, the detail mechanism and distribution characteristic of exergy destruction were also studied at different injection parameters from the perspective of in-cylinder microscopic field. The results showing that first, adjusting injection pressure from 130 MPa to160 MPa, exergy efficiency and heat transfer exergy are positively correlated with injection pressure, while exhaust exergy and exergy destruction are negatively correlated with injection pressure, but the influence of injection pressure on heat transfer exergy and exergy destruction is relatively weak. Secondly, advancing injection timing from 1.7°CA BTDC to 6.7°CA BTDC, the exergy efficiency and heat transfer exergy increase significantly, while the exhaust exergy and exergy destruction decrease gradually, compared with injection pressure, injection timing has a greater impact on exergy terms. Third, variation of exergy terms occurs mainly in combustion process at different injection parameters. Fourth, the higher exergy destruction mainly concentrates in the region with equivalence ratio of 1–1.5 at different injection pressures, the EDR (exergy destruction rate) is proportional to HRR (heat release rate) in the same temperature range at different injection timing, the root influence causes of injection pressure and timing on exergy destruction are inhomogeneity of equivalent ratio and local temperature during combustion process, respectively. Finally, increasing exergy efficiency is accompanied by decrease of exergy destruction, reasonable adjustment of injection parameters of turbocharged diesel engine to enhance high-temperature and lean combustion characteristics during combustion process of in-cylinder mixture can effectively promote the exergy efficiency and restrain exergy destruction.
Natural gas/diesel dual-fuel combustion compression ignition engine has the potential to reduce NOx and soot emissions. However, this combustion mode still suffers from low thermal efficiency and high level of unburned methane and CO emissions at low load conditions. The present paper reports the results of an experimental and numerical study on the effect of diesel injection timings (ranging from 10 to 50 °BTDC) on the combustion performance and emissions of a heavy duty natural gas/diesel dual-fuel engine at 25% engine load. Both experimental and numerical results revealed that advancing the injection timing up to 30 °BTDC increases the maximum in-cylinder pressure. However, with further advancing the injection timing up to 50 °BTDC, the maximum in-cylinder pressure decreases which is mainly due to the lower in-cylinder temperature before SOC. Moreover, the analysis of OH spatial distribution shows that, at very advanced diesel injection timings, the non-reactive zones are much narrower than later injection timings during the last stages of combustion, indicating a more predominant premixed combustion mode. At retarded diesel injection timings, the consumption of premixed fuel in the outer part of the charge is likely to be a significant challenge for dual-fuel combustion engine at low engine load conditions. However, with advancing the diesel injection timing, the OH radical becomes more uniform throughout the combustion chamber, which confirms that high temperature combustion reactions can occur in the central part of the charge. Diesel injection timing of 30 °BTDC appears to be the conversion point of all conventional dual-fuel combustion modes. Further advancing diesel injection timing beyond this point (30 °BTDC) results in noticeable reduction in NOx and unburned methane emissions, while CO emissions exhibit only slight drop. However, at very advanced diesel injection timings of 46 and 50 °BTDC, NOx, and unburned methane emissions continue to drop, whereas and CO emissions tend to increase. The results showed also that the highest indicated thermal efficiency is achieved at these very advanced diesel injection timings of 46 and 50 °BTDC. Finally, the results revealed that, by advancing diesel injection timing from 10 °BTDC to 50 °BTDC, NOx, unburned methane, and CO emissions are reduced, respectively, by 65.8%, 83%, and 60% while thermal efficiency is increased by 7.5%.
This study investigates the effects on the performance of a diesel generator set at constant electric power of 2.43 kW (approximately 60% nominal engine load condition) and rotation at 3600 rpm operating with a 7% biodiesel-diesel blend (B7) and being doped with hydrogen into the intake air. Hydrogen was injected continuously into the engine intake manifold at different mass concentrations of 2, 6, 8 and 10% of the total fuel mass (B7 + hydrogen) which represents energy fractions of 5, 15, 20 and 24% of total fuel energy. To this, a small L-shaped tube installed at the center of the pipe was used. It is anticipated that the intake air fluctuations at that location, due to opening and closing the intake valve, allows a rapid mixture of hydrogen and air. Due to the addition of hydrogen the total amount of energy in the fuel (B7 + hydrogen) introduced into the engine was increased, so that the engine speed tends to increase, but this was prevented by the governor of the fuel injection pump which decreases the amount of B7 injected until the working frequency of the generator was 60 Hz. The test results showed a reduction in the specific fuel consumption as a function of the increase of hydrogen concentrations. Likewise, CO2, CO and HC emissions decreased proportionately as the hydrogen concentration was increased. On the other hand, the emissions of nitrogen oxides (NOx) increased due to the increase in the average temperature inside the cylinder. There was also an increase in the peak pressure and in the heat release rate inside the cylinder, since B7 ignition delay was reduced due to the increase in hydrogen content.
There is an intimate connection between energy, the environment and sustainable development. A society seeking sustainable development ideally must utilize only energy resources which cause no environmental impact (e.g. which release no emissions to the environment). However, since all energy resources lead to some environmental impact, it is reasonable to suggest that some (not all) of the concerns regarding the limitations imposed on sustainable development by environmental emissions and their negative impacts can be in part overcome through increased energy efficiency. Clearly, a strong relation exists between energy efficiency and environmental impact since, for the same services or products, less resource utilization and pollution is normally associated with increased energy efficiency. Presented in this paper are (i) a comprehensive discussion of the future of energy use and the consequent environmental impacts in terms of acid precipitation, stratospheric ozone depletion and the greenhouse effect, (ii) some solutions to current environmental issues in terms of energy conservation and renewable energy technologies, (iii) some theoretical and practical limitations on increased energy efficiency, (iv) discussions of the relations between energy and sustainable development, and between the environment and sustainable development, and an (v) illustrative example. In this regard, a number of issues relating to energy, environment and sustainable development are examined from both current and future perspectives. In addition, some recommendations are drawn from the results we present for the use of energy scientists and engineers and policy makers, along with the anticipated effects.
An energy-exergy analysis for a diesel engine has been conducted. Both First and Second Laws of Thermodynamics are employed to take into account the quantity and quality of energy. The availability or exergy analysis based on the Second Law is utilized to identify the source of losses in useful energy within the components of diesel engines. This shows about 50% of the chemical availability of the fuel is destroyed due to uncounted factors and about 15% is lost in the cooling water or exhaust gases. On the other hand, the energy analysis shows 50% is wasted in the cooling water and exhaust gases and 15% is lost due to uncounted factors.
The present study experimentally investigated the performance and emission characteristics of the diesel engine with hydrogen added to the intake air at late diesel-fuel injection timings. The diesel-fuel injection timing and the hydrogen fraction in the intake mixture were varied while the available heat produced by diesel-fuel and hydrogen per second of diesel fuel and hydrogen was kept constant at a certain value. NO showed minimum at specific hydrogen fraction. The maximum rate of incylinder pressure rise also showed minimum at 10 vol. % hydrogen fraction. However, it is desirable to set the maximum rate of incylinder pressure rise less than 0.5MPa/deg. to realize low level of combustion noise and NO emission. We attempt to reduce further NO and smoke emissions by EGR. As the result, in the case of the diesel-fuel injection timing of −2 °. ATDC with 3.9 vol. % hydrogen addition, the smoke emission value was 0%, NO emission was low, the cyclic variation was low, and the maximum rate of incylinder pressure rise was acceptable under a nearly stoichiometric condition without sacrificing indicated thermal efficiency.
This study presents the energy, exergy and heat release analysis of a John Deere 4045 T 4.5 L, four-stroke, four-cylinder, turbocharged diesel engine. The engine was run with four different types of fuel: yellow grease methyl ester (YGME); soybean oil methyl ester (SME); and soybean oil methyl ester containing either 0.75 or 1.5 w/w % of the cetane improver 2-ethylhexyl nitrate (SME-0.75%EHN and SME-1.5%EHN, respectively). The engine was tested at 1400 1/min under a full load of 352 Nm. For reliability, the fuels were tested three times, and the mean values were compared using different statistical techniques. The objective in this study was to determine the effect of cetane number and ignition delay on the energy and exergy efficiencies of an internal combustion engine and to compare the results for the types of fuel stated earlier. The average thermal efficiency was approximately 40.5%, and the exergetic efficiency was approximately 37.3%. The mean exergetic efficiencies of the fuels were in the order ψSME > ψSME–0.75%EHN > ψSME–1.5%EHN > ψYGME. There were significant differences among the mean values according to Student's t-tests. It is concluded that a lower cetane number, a longer ignition delay period and a higher level of premixed combustion may increase the exergetic efficiency of a diesel engine.Research Highlights► Cetane number and the ignition delay effect on combustion parameters ► on energetic and exergetic efficiencies of a turbocharged diesel engine using biodiesel fuels. ► Study couples combustion analysis with energetic and exergetic efficiency analyses. ► As cetane number increases efficiency decreases.
In a quest to improve air quality, many experts are supportive of using hydrogen as the fuel of the future. More recently, two other key objectives of several nations have been instrumental in accelerating development for an alternative fuel, independence from foreign oil and securing renewable, affordable energy sources.Most experts suggest that hydrogen as an alternative fuel has the elements to address all three of these concerns. In its purest form there are zero emissions, the supply is endless and production may use a variety of energy sources, including renewable.The purpose of this paper is to explore and understand the challenges related to moving to a hydrogen-fueled economy. The efforts of some countries and leaders in the automotive sector are reviewed as they strive to develop the technology and find possible answers to production, storage and distribution challenges.There are many opinions on how best to proceed. Some favor moving directly to a hydrogen infrastructure, while others advocate transitioning by using hydrogen fuel cell technology. While the problems of migrating to hydrogen are complex, there is no doubt that hydrogen is the energy source for the 21st century.