A review study on diesel and natural gas and its impact on CI engine emissions

Diesel engines produce high emissions of nitrogen oxide, smoke and particulate matter. The challenge is to reduce exhaust emissions but without making changing their mechanical configuration. This paper is an overview of the effect of natural gas on the diesel engine emissions. Literature review suggests that engine load, air-fuel ratio, and engine speed play a key role in reducing the pollutants in the diesel engine emissions with natural gas enrichment. It is found that increasing the percentage of natural gas (CNG) will affect emissions. Nitrogen oxide (NOx) is decreased and increased at part loads and high loads respectively when adding CNG. The reduction in carbon dioxide (CO2), particulate matter (PM) and smoke are observed when adding CNG. However, carbon monoxide (CO) and unburned hydrocarbon (HC) are increased when CNG is added

A two-component CFD studies of the effects of H2, CNG, and diesel blend on combustion characteristics and emissions of a diesel engine

Numerical simulations were conducted on a Ricardo Hydra diesel engine which is single cylinder engine and uses direct injection method. This study was performed by using a two-dimensional CFD code to examine the combustion characteristics and emissions of a diesel engine in diesel-CNG and diesel-H2 dual-fuel operations, as well as in the diesel-CNG-H2 tri-fuel operation at various air-fuel ratios. The results indicate that the peak in-cylinder pressure and peak temperature were increased with the addition of gaseous fuels at low and medium values of exceeds air. Compared with Diesel-H70-N30 for tri-mode and Diesel-H2 for dual mode, it is observed that there were no effects on the peak temperature at high exceed air. At 2.4 exceed air, the peak pressure increases by means of adding the limit value of hydrogen, such as H30-N70 and H50-N50, to CNG and it begins to decrease with H70-N30 and H2-Diesel operations. Diesel-H2-CNG operations decrease CO/CO2 emissions compared with Diesel-CNG operation and decrease NO emission compared with Diesel-H2 operation at every exceed air. The reduction in CO/CO2 emissions was suggested at high hydrogen fraction in CNG (H70-N30) with all exceeds air whereas low hydrogen fraction in CNG (H30-N70) can repress uncontrolled hydrogen combustion and further limit the increment of NO emission

A review of the effect of hydrogen addition on the performance and emissions of the compression – ignition engine

Diesel engines produce high emissions of smoke, particulate matter and nitrogen oxide. The challenge now is to decrease exhaust emissions without making any major changes on their mechanical configuration. Therefore, adding hydrogen becomes a natural choice to enhance the performance and emissions of diesel engines. This paper offers an overview of the effect of hydrogen additional to the diesel engine. The overall finding from the review suggests that the air–fuel ratio, engine speed, and engine load play a key role in the performance and emission of diesel engines with hydrogen enrichment. The brake thermal efficiency (BTE), brake power output, brake means effective pressure (BMEP), and specific energy consumption (SEC) are dependent on the operating conditions of the engine when adding the hydrogen. It is also found that increasing the percentage of hydrogen will affect emissions, so that the reduction in unburned hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO2), particulate matter (PM), and smoke are observed when adding the hydrogen. However, nitrogen oxide (NOx) is increased when enriching H2, but this increase in NOx can be controlled by numerous injections, exhaust gas recirculation (EGR) or water injection as well as exhaust after-treatment as has been discussed in this paper

Large-vscale hydrogen production and storage technologies: Current status and future directions

This is an accepted manuscript of an article published by Elsevier in International Journal of Hydrogen Energy on 13/11/2020, available online: https://doi.org/10.1016/j.ijhydene.2020.10.110 The accepted version of the publication may differ from the final published version.Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen.Published versio

Numerical simulation of the effect of Ch4, H2 and diesel fuel mixture on four stroke engine

Gaseous fuels have been investigated to be a helpful substitute in compression-ignition engine by researchers. There was extension in the ignition delay of diesel-CH4 dual-fuel mode as compared with usual diesel fuel mode. Methane has a low flame propagation speed as well as slight flammability whereas hydrogen has the extreme opposite characteristics. As such adding hydrogen can enhance methane’s combustion process making it extra convenient in diesel engine application. H2-Diesel produced many of the unwanted effects such as rapid burning rate and increased diffusivity and reduced ignition energy of hydrogen that may lead to knocking, an impact that is harmful to engine’s mechanical durability as well as safety. Methane addition has the ability to make hydrogen combustion stable and smoother which can prevent imperfect combustion. Methane can also lower the combustion temperature of hydrogen so as to repress NOx emission. In the present study, the author proposes that by adding hydrogen into methane and diesel, it can improve the combustion process. The usage of GAMBIT software was chosen to create the entire computational domain of the engine and for Computational Fluid Dynamics (CFD) the FLUENT code was used. The engine was operated under dual-fuel and tri-fuel modes with different values of excess air (λ) including 1.2, 1.4, 1.6, 1.8, 2, 2.2 and 2.4. Moreover, torque (20.18 N.M),intake temperature (330 K), and engine speed (2000 rpm) were taken constantly at an atmospheric pressure. Diesel-CH4, diesel-H2 dual-fuel operation, and diesel-CH4-H2 tri-fuel operation were employed in this work. H30-M70, H50-M50 and H70-M30 were designed for the mixtures percent of hydrogen to methane which are 30:70, 50:50 and 70:30 %, respectively, and then used them in the simulations. Due to knocking, the maximum quantity of substitution by hydrogen was limited to 50%. Therefore, the quantity of diesel was employed 50 percent by mass from the total fuel at diesel mode and the other 50 percent was substituted by the methane and hydrogen as mentioned above. The addition of gaseous fuels increases the peak in-cylinder pressure and peak temperature at both the low and medium values of the exceed air. Meanwhile, at high value of exceeds air, no effects on the peak temperature were noted between Diesel-H70-M30 for tri mode and Diesel-H2 for dual mode. Compared with CH4-Diesel at 2.4 exceed air, the peak pressure increases by 28.57% and 33.414% by way of adding the limit value of hydrogen to methane,such as H30-M70 and H50-M50, respectively. Compared with H50-M50, it begins to decrease by 0.726% and 3.81% with H70-M30 and H2-Diesel operations, respectively, that may be because of the low value of fuels in air compared with other cases. The addition of methane in hydrogen produces a smoother combustion of hydrogen and ascertains that the engine is safe and it has mechanical durability. Tri-fuel and dual-fuel modes have a similar suppression effect on CO2 emission but with hydrogen there is more reduction in CO2 emission compared with methane. However, Diesel-H2-CH4 operations decrease the CO emission compared with the Diesel-CH4 operation and decrease the NO emission compared with the Diesel-H2 operation at every exceed air. High hydrogen fraction in methane (H70-M30) is suggested at all exceeds air in order to reduce CO/CO2 emissions, whereas low hydrogen fraction in methane (H30-M70) can suppress the uncontrolled hydrogen combustion and limit the increment of the NO emission

A review study on diesel and natural gas and its impact on CI engine emissions

Diesel engines produce high emissions of nitrogen oxide, smoke and particulate matter. The challenge is to reduce exhaust emissions but without making changing their mechanical configuration. This paper is an overview of the effect of natural gas on the diesel engine emissions. Literature review suggests that engine load, air-fuel ratio, and engine speed play a key role in reducing the pollutants in the diesel engine emissions with natural gas enrichment. It is found that increasing the percentage of natural gas (CNG) will affect emissions. Nitrogen oxide (NOx) is decreased and increased at part loads and high loads respectively when adding CNG. The reduction in carbon dioxide (CO2), particulate matter (PM) and smoke are observed when adding CNG. However, carbon monoxide (CO) and unburned hydrocarbon (HC) are increased when CNG is added

HCNG fueled spark-ignition (SI) engine with its effects on performance and emissions

The usage of natural gas in internal combustion engines involves various difficulties, like weak lean-burn ability, low flame speed and ignitability, which demand deep studies for its usage in IC engines. For compressed natural gas (CNG) in SI engines, there is an engine efficiency sacrifice at low loads and high levels of hydrocarbon (HC) and carbon monoxide (CO) emissions which cannot be solved without using after-treatment equipment. This equipment, however, is very expensive. Therefore, an additional fuel can enhance the characteristics of the combustion of natural gas, which can be added in the intake charge. Hydrogen is an effective gas for enhancing the flame rate regarding combustion in an SI-CNG engine, in addition to increasing engine stability. Small amounts of hydrogen improve performance and reduce exhaust emissions. Thus, a number of investigators have carried out research studies on SI engines with different ratios of HCNG. This paper is comprehensive overview of CNG, H-2 and HCNG blends. The main topics discussed consist of the combustion fundamentals of natural gas, hydrogen and hydrogen-natural gas mixture. Natural gas and hydrogen usage as fuels and their characteristics have been analysed. The storage of hydrogen and HCNG is still challenging researchers and, therefore, their storage has been taken into consideration. Moreover, a comprehensive review has been performed of HCNG blends in order to understand the effect of hydrogen enriched CNG on performance and the emissions of SI engines. The combustion characteristics of HCNG engines are strongly dependent on the conditions of the engine. The air-fuel ratio, the time of injection, the compression ratio and speed play a major role in blending HCNG in an SI engine and have been discussed in this article

HCNG fueled Compression-Ignition (CI) engine with its effect on performance and emissions

Because of the high energy consumption rates as well as creating a clean environment, we need a fuel which can be substituted for fossil fuels. Natural Gas (CNG) and Hydrogen (H) are the best among the 2 alternative fuels and possess specific characteristics such as sustainability, renewability and clean burning capacity. This review study is presented of contemporary research and given a comprehensive overview on the HCNG fueled diesel engine. Major subjects that have discussed here include introduction and fundamentals of dual fuel diesel engine with using natural gas and hydrogen and details on the different mixture formation strategies of HCNG fueled and their effects on engine performance and emissions characteristics

A review study on diesel and natural gas and its impact on CI engine emissions

Diesel engines produce high emissions of nitrogen oxide, smoke and particulate matter. The challenge is to reduce exhaust emissions but without making changing their mechanical configuration. This paper is an overview of the effect of natural gas on the diesel engine emissions. Literature review suggests that engine load, air-fuel ratio, and engine speed play a key role in reducing the pollutants in the diesel engine emissions with natural gas enrichment. It is found that increasing the percentage of natural gas (CNG) will affect emissions. Nitrogen oxide (NOx) is decreased and increased at part loads and high loads respectively when adding CNG. The reduction in carbon dioxide (CO2), particulate matter (PM) and smoke are observed when adding CNG. However, carbon monoxide (CO) and unburned hydrocarbon (HC) are increased when CNG is added

Influence of natural gas and hydrogen properties on internal combustion engine performance, combustion, and emissions: A review

This paper provides a comprehensive overview of the physical properties and applications of natural gas (NG) and hydrogen as fuels in internal combustion (IC) engines. The paper also meticulously examines the use of both NG and hydrogen as a fuel in vehicles, their production, physical characteristics, and combustion properties. It reviews the current experimental studies in the literature and investigates the results of using both fuels. It further covers the challenges associated with injectors, needle valves, lubrication, spark plugs, and safety requirements for both fuels. Finally, the challenges related to the storage, production, and safety of both fuels are also discussed. The literature review reveals that NG in spark ignition (SI) engines has a clear and direct positive impact on fuel economy and certain emissions, notably reducing CO2 and non-methane hydrocarbons. However, its effect on other emissions, such as unburnt hydrocarbons (UHC), nitrogen oxides (NOx), and carbon monoxide (CO), is less clear. NG, which is primarily methane, has a lower carbon-to-hydrogen ratio than diesel fuel, resulting in lower CO2 emissions per unit of energy released. In contrast, hydrogen is particularly well-suited for use in gasoline engines due to its high self-ignition temperature. While increasing the hydrogen content of NG engines reduces torque and power output, higher hydrogen input results in reduced fuel consumption and the mitigation of toxic exhaust emissions. Due to its high ignition temperature, hydrogen is not inherently suitable for direct use in diesel engines, necessitating the exploration of alternative methods for hydrogen introduction into the cylinder. The literature review suggests that hydrogen in diesel engines has shown a reduction in specific exhaust emissions and fuel consumption and an increase in NOx emissions. Overall, the paper provides a valuable and informative overview of the challenges and opportunities associated with using hydrogen and NG as fuels in IC engines. It highlights the need for further research and development to address the remaining challenges, such as the development of more efficient combustion chambers and the reduction of NOx emissions