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The concepts of residual gas and admission (or volumetric efficiency) coefficients are used exclusively by specialists in the field of piston Internal Combustion Engines. However, it is preferable to apply the concepts of volume fractions of components of the working mixture consisting of air, fuel, residual, and recirculating gases, for the evaluation of filling. This simplifies and makes it more easy-to-grasp the influence of individual factors on the results of gas exchange processes. The proposed approach makes it possible to take into account the impact on the engine indicators of the molecular weight of the fuel used and the degree of external recirculation, as well as to reduce the number of independent variables. At the same time, the displacement coefficient A proposed by the author characterizes a decrease in filling when an engine with external mixing is switched to a gaseous fuel with a lower molecular weight. A change in the valve timing made it possible to produce an effect on the composition of the working mixture and, thereby, the environmental characteristics of the engine. In the case of external recirculation, it becomes necessary to estimate the summary fraction of neutral combustion products in the working mixture, on which all engine operation depended. This ”overall degree of recirculation” can also be determined using the proposed approach. [ABSTRACT FROM AUTHOR]

Public transport can play a central role in representing a viable and sustainable mobility solution, especially in urban areas. Average energy consumption and emissions per passenger are much lower than for private cars. At the same time, current buses often mostly rely on diesel, and there are different solutions that can contribute to public transport decarbonization. Biomethane is among the options to exploit local low-carbon resources to decrease the emissions of public transport in urban environments. This paper presents the analysis of a real case study considering real data on the fuel consumption and mileage of the existing bus fleet in the city of Turin, Italy, composed by diesel and natural gas buses. The aim of this study is to estimate the effect of different penetration levels of biomethane in substitution of the current fuels. The results show that the use of biomethane in urban buses could save to up to 71% of emissions compared to the current situation, and savings would increase to 75% when deploying biomethane and electric buses together. Average emissions per pkm could decrease from a current level of 85.5 gCO2/pkm to 21.3–63.4 gCO2/pkm depending on the penetration of biomethane and electric buses. The sensitivity analysis shows even higher savings when accounting for the future decrease of the electricity carbon intensity in Italy and for the additional benefits related to avoided emissions from manure disposal. The results of the analysis demonstrate the potential contribution of biomethane in decarbonizing urban buses, and the findings presented for this case study can be of use for policy makers and researchers that deal with a similar situation in other cities and countries. [ABSTRACT FROM AUTHOR]

The use of hydrogen can be a potential solution to reduce high CO and unburnt HC emissions, which is one of the most critical challenges, from Reactivity Controlled Compression Ignition (RCCI) engines at low loads as it is a very clean and carbon-free fuel candidate for internal combustion engines. Therefore, the aim of this study is designed to investigate numerically the effect of the hydrogen share on combustion characteristics in a diesel research engine operated in RCCI mode. The engine is fueled with conventional diesel and iso-octane enriched with hydrogen and is operated at 20% of the maximum torque (low load) and 2400 rpm. A 40% of conventional diesel (in the case of conventional diesel mode (CDM), its share was 100%) is injected per cycle into cylinder of the engine, while varying proportions of iso-octane (60% to 12%) and hydrogen (0% to 48%) are sprayed into the air from the intake manifold. Both CDM and RCCI combustion models built by 3D scanning of the existing engine using reverse engineering to computational fluid dynamic (CFD) was simulated through ANSYS-Forte coupled with a chemical kinetics solver (Chemkin-Pro). The simulation results showed that by adding hydrogen to iso-octane in RCCI mode, the proportion of hydrogen could be increased up to 48% while improving thermal efficiency by 33.3% in comparison with 24.9% with RCCI without hydrogen addition. Therefore, the overall hydrocarbon fuel consumption per cycle was reduced by up to 47.52%. Hydrogen addition resulted in a higher concentration of OH species in the flame front, and higher pressure and temperature in the cylinder, in turn, contributed to an increase in NOx emissions considerably but led to decrease in CO/HC emissions of RCCI operation. The decrease in the emissions of CO, HC, and C2H2 of up to 64.6, 81.8, and 76.6%, respectively, was observed by using 48% of H2 in RCCI mode compared to RCCI mode without hydrogen addition. It was concluded that high CO and unburned HC emissions from RCCI combustion. This research provides promising contributions to the literature for using hydrogen in substitution of hydrocarbon fuels and reducing emissions from RCCI engines. [ABSTRACT FROM AUTHOR]

This research demonstrates a palm kernel shell gasification system for producing fuel gas, also known as producer gas. Using air as an oxidant, the gasification process converts palm kernel shells into fuel gas which contains combustible gases, such as hydrogen, carbon monoxide, and methane with nitrogen dominating the composition of the gas. This fuel gas can supply heat via direct combustion or generate electricity for fossil fuel substitution of an internal combustion engine. As a biomass-derived gas, the fuel gas is characterized as carbon-neutral inherently. During the conversion process, the system needs electricity to power the screw feeder, air blowers, and cooling-water pumps, and to rotate the gasifier's bottom plate to take the char out. Based on the experiments, mass balance, and energy balance calculations, this study examines the global warming, acidification, and eutrophication potential using the openLCA v1.10.3 software and Environmental Footprint (MID-Point indicator) database for impacts assessment when the system is operated in Indonesia and Malaysia with various electricity sources. It is found that the feedstock contributed most of the global warming potential and eutrophication potential, while the electricity dominated the acidification potential. This study recommends operation at a lower equivalent ratio to reduce environmental impacts. • Air gasification of palm kernel shells to produce fuel gas was conducted at a 25 kg/h gasifier capacity. • This study assessed the Global Warming, Eutrophication, and Acidification Potentials of the gasification process. • The effects of equivalent ratios on the environmental impacts were evaluated using a life cycle approach. • Palm kernel shells acquisition showed significant environmental impacts. • The scenarios to improve the process included variations of feedstock sources and electricity generation methods. [ABSTRACT FROM AUTHOR]

Supporting policies to achieve a green revolution and ecological transition is a global trend. Although the maritime transport of goods and people can rightly be counted among the least polluting sectors, much can be done to further reduce its environmental footprint. Moreover, to boost the ecological transition of vessels, a whole series of international regulations and national laws have been promulgated. Among these, the most impactful on both design and operational management of ships concern the containment of air-polluting emissions in terms of GHG, NOx, SOx and PM. To address this challenge, it might seem that many technologies already successfully used in other transport sectors could be applied. However, the peculiar characteristics of ships make this statement not entirely true. In fact, technological solutions recently adopted, for example, in the automotive sector must deal with the large size of vessels and the consequent large amount of energy necessary for their operation. In this paper, with reference to the case study of a medium/large-sized passenger cruise ship, the use of different fuels (LNG, ammonia, hydrogen) and technologies (internal combustion engines, fuel cells) for propulsion and energy generation on board will be compared. By imposing the design constraint of not modifying the payload and the speed of the ship, the criticalities linked to the use of one fuel rather than another will be highlighted. The current limits of application of some fuels will be made evident, with reference to the state of maturity of the relevant technologies. Furthermore, the operational consequences in terms of autonomy reduction will be presented. The obtained results underline the necessity for shipowners and shipbuilders to reflect on the compromises required by the challenges of the ecological transition, which will force them to choose between reducing payload or reducing performance. [ABSTRACT FROM AUTHOR]

The electric vehicle (EV) transition is underway in the UK and many other countries worldwide, switching from fossil fuel powered internal combustion engine (ICE) road transport to EVs that can be powered by renewable electricity. Whilst the projected energy and carbon reduction impacts are well understood, we have only a partial view of the potential socio-macroeconomic effects of the EV transition, i.e. the impacts on GDP and jobs. Common energy-economy models feature only limited energy-economy integration, and only assign a small role for energy in economic growth. Thus whilst economic changes such as increases to investment can feed into macroeconomic impact assessment, the impacts of the energy system changes are potentially underestimated. In response, we use a novel macro-econometric model – MARCO-UK – to conduct a whole system analysis with two main scenarios: an ICE baseline (with no EV transition) and 100% EV transition scenario to 2050. We investigate the effects of the scenarios on the UK's energy system (efficiency, energy services, rebound) and economic system (employment, GDP, debt), under different conditions of investment, rebound and electricity prices. We find the most significant impacts stem from energy system changes, with annual economic growth rising from 1.71%/year (baseline) to 2.25%/year in the main EV scenario. In contrast, the impacts from economic investment changes are much lower in scale. Therefore, the socio-macroeconomic benefits of the EV transition may be underestimated. We also find that overall long-term economy-wide rebound in our central EV scenario is 76%, which means the energy savings from the EV transition may be less than hoped. Overall, our analysis identifies potential trade-offs regarding the labour market, levels of indebtedness, energy rebound and associated carbon emissions that should be taken into consideration. • The energy and socioeconomic impacts of the UK's EV transition are not well known. • We model energy changes to efficiency and fuel switch to electricity. • Most significant impacts stem from energy system change not investment stimulus. • The EV transition could realise an extra 0.5%/yr of GDP growth. • But economy-wide rebound effects reduce energy savings from the EV transition. [ABSTRACT FROM AUTHOR]

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Summary Hydrogen is one of the most promising alternative fuels for the transportation industry. The use of hydrogen to enable lean burn in internal combustion engines is an attractive solution for reducing CO2 emissions from two points of views: the substitution of carbon‐based fuels and the increased thermal efficiency due to lean operation. Combining this strategy with the passive pre‐chamber ignition system with gasoline/hydrogen blends is even more interesting. The main limitations of the passive pre‐chamber concept in a high compression ratio spark‐ignition engine were shown through engine experiments. A numerical study was then performed to evaluate the chance of extending the dilution limit by using hydrogen along with this technology. Results show how the use of hydrogen provides considerable benefits in the main chamber combustion process by enhancing the thermo‐chemical properties of the mixture, increasing the flame speed, and improving the flame structure. Using an adequate gasoline‐hydrogen blend proved to enable optimum burning rates at lean conditions, leading to a relevant thermal efficiency gain. [ABSTRACT FROM AUTHOR]

The approach of fossil fuel substitution requires alternative strategies in the progressing sector coupling of energy storage, distribution and conversion. Promising solutions are flexibly supply chain models of green and blue hydrogen which is fed into the natural gas network (HNG). Prerequisite for a successful implementation is the functional capability of end-use applications for which different volumetric hydrogen thresholds are documented in literature. A clear research gap is thereby evident for HNG fired medium-speed large-bore gas engines typical used for stationary power generation. For solving this problem, generic single cylinder tests with focus on operating window, NO x formation and hydro-carbon emissions have been carried out. The results are analysed and compared to available publications of HNG fired high-speed gas engines to derive general insights of the combustion characteristics. Under rising blending share, an in literature described, general shifting of the possible operating window and an increase of NO x formation are detected. In terms of unburned hydrocarbons, a NO x -neutral reduction potential through hydrogen blending is only visible under very lean operating conditions. This result deviates from expected literature values of high-speed engine setups. The experimental study demonstrates the NO x neutral combustion capability of medium-speed large-bore gas engines under 20% hydrogen admixture. • Hydrogen blending in future power generation has rising importance in island modes. • Detailed literature review in the field of H 2 -blended gas engines is presented. • H 2 /NG shifts the operating area and reduces THC emissions at very lean conditions. • NO x neutral 20% H 2 /NG combustion is experimental validated. [ABSTRACT FROM AUTHOR]

This paper employs a review of the technical literature to estimate the potential decrease in greenhouse gas (GHG) emissions that could be achieved by increasing the application of gas engines in China in three sectors: urban public transport vehicle; shipping; and thermal power plants. China's gas engine development strategies and three types of gas resource are discussed in the study, which indicates that gas engines could decrease GHG emissions by 520 megatonnes (Mt) of carbon dioxide equivalent (CO) by 2020. This would account for 9.7 % of the government's target for decreasing GHG emissions and is dominated by methane recovery from the use of coal mine gas (CMG) and landfill gas (LFG) for power generation. In the public urban transport vehicle and shipping sectors the low price of natural gas and the increasing demand for the control of harmful emissions could spur the rapid uptake of gas engine vehicles. However, the development of CMG- and LFG-fuelled power plants has been limited by the unwillingness of local enterprises to invest in high-performance gas engine generators and the associated infrastructure. Therefore, further compulsory policies that promote CMG use and LFG recovery should be implemented. Moreover, strict regulations on limiting methane leakage during the production and distribution of gas fuels are urgently needed in China to prevent leakage causing GHG emissions and largely negating the climate benefits of fuel substitution. Strategies for increasing the application of gas engines, promoting gas resources and recovering methane in China are instrumental in global GHG mitigation strategies. [ABSTRACT FROM AUTHOR]

This work aims to elucidate notions concerning the ideal operation and greenhouse gas (GHG) emissions benefits of combined heat and power (CHP) systems by investigating how various metrics change as a function of the GHG emissions from the underlying electricity source, building use type and climate. Additionally, a new term entitled “CHP Attributable” reductions is introduced to quantify the benefits from the simultaneous use of thermal and electric energy, removing benefits achieved solely from fuel switching and generating electricity more efficiently. The GHG emission benefits from implementing internal combustion engine, microturbines, and phosphoric acid (PA) fuel cell based CHP systems were evaluated through an optimization approach considering energy demands of prototypical hospital, office, and residential buildings in varied climates. To explore the effect of electric GHG emissions rates, the ideal operation of the CHP systems was evaluated under three scenarios: “High” GHG emissions rates, “Low” GHG emissions rates, and “Current” GHG emissions rate for a specific location. The analysis finds that PA fuel cells achieve the highest GHG emission reductions in most cases considered, though there are exceptions. Common heuristics, such as electric load following and thermal load following, are the optimal operating strategy under specific conditions. The optimal CHP capacity and operating hours both vary as a function of building type, climate and GHG emissions rates from grid electricity. GHG emissions reductions can be as high as 49% considering a PA fuel cell for a prototypical hospital in Boulder, Colorado however, the “CHP attributable reductions are less than 10%. [ABSTRACT FROM AUTHOR]

Well-established examples of biofuel utilization, such as ethanol and biodiesel, prove that it is possible to establish sustainable ways to progressively reduce the market dependence on fossil fuels, maintain the use of internal combustion engines (ICEs), and mitigate some negative aspects of their utilization. Biomass-to-liquid route (BtL), especially the Fischer-Tropsch (FT) process, represents a pathway for achieving the conversion of biomass into liquid biofuels (i.e., gasoline, diesel, and kerosene). Synthetic fuels obtained from municipal solid waste (MSW) via the FT process have already been studied as a partial substitution for jet fuels, encouraged by tax credits and feedstock availability. The use of biofuels by the aviation market represents an increasing trend, with future projections pointing to a significant insertion of those renewable fuels in commercial products. However, the net cost of the BtL route is still prohibitive for commercial applications due to many technical challenges, for example, the gas cleaning and conditioning process to meet FT process gas quality requirements. The desired gas quality can be achieved by knowing all the key parameters involved, from the feedstock selection, gasification process, and finally, the cleaning system. This work synthesized relevant information on impurities generation and related removal techniques considering the gasification integrated into the Fischer-Tropsch process (G-FT). The review process provides complementary information about the influence of feedstock selection, gasification parameters, measuring techniques, and related issues. Finally, a flexible gas cleaning sequence is proposed by comparing the existing gas cleaning techniques and pathways, observing Fischer-Tropsch synthesis (FTS) gas quality requirements. [Display omitted] • The formation, measurement, and mitigation of major BG impurities are covered. • Available gas cleaning routes for integrated G-FT are discussed. • A theoretical gas cleaning route is proposed to achieve FTS gas quality criteria. [ABSTRACT FROM AUTHOR]

Hydrogen and Compressed Natural Gas are great alternatives to the pure fossil fuels. Many researches confirm the advantages of using hydrogen and natural gas blended together for the internal combustion engine in both areas of improving performances and reducing emission levels. In a short to medium range terms, the air pollution throughout the globe could be significantly reduced by using HCNG in the internal combustion engine and in many other applications with the substitution of using HCNG as a main source of fuel or as a secondary source of fuel such as the dual fuel operation system in the diesel vehicle. This paper investigates the emission characteristics of using HCNG as a secondary source of fuels on a EURO 4 diesel vehicle with four cylinders of 2494 cc displacement D4D commonrail direct injection diesel engine comparing to the original diesel operation with diesel and HCNG blended dual fuel operation. The experiments were conducted with minimum pilot diesel injection into the engine and maximum additional HCNG into the engine with using H2 electrolyzer for hydrogen supplies. In this experiment, the pilot diesel and HCNG blended were operated with special designed closed loop stepping motor diesel to CNG dual fuel system and hydrogen electrolyzer for the internal combustion engine. The results indicated that the average CO emission decreased by 12.97%, HC emission decreased by 15.84%, NOx emission decreased by 1.16% and PM emission decreased by 9.14% with the diesel HCNG dual fuel mode comparing to the pure diesel operation from low RPM (800) to highest RPM (4000). [ABSTRACT FROM AUTHOR]

Due to the shortage of petroleum products and its increasing cost, efforts are on to develop alternate fuels, especially diesel oil, for partial or full replacement. Also, internal combustion engines generate undesirable emissions during combustion process. The emissions exhausted in to the surroundings pollute the atmosphere and causes several problems. The emissions of concern are: unburnt hydrocarbons, oxides of carbon, and oxides of nitrogen (NO X). Advanced diesel fuel formulations offer significant emission reductions to new and older in-use engines every time the fuel tank is filled. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation. The incorporation of water also reduces NO X emissions by lowering the peak combustion temperatures through high heat of vaporization. When using water blend diesel, the engine fuel system recognizes the liquid as diesel fuel because the water droplet is encapsulated within a diesel fuel. In this experiment, we have used single cylinder four-stroke engine and the water-blend diesel emulsion is used and the diesel emission test, emulsion emission test, and various gases has been analyzed; smoke meter test is also conducted for various rate of loads. The test results from the engine fuelled with water-blend diesel showed reduction in emissions as compared to that of engine fuelled with conventional diesel. The better emissions in the CI engine using water-blend diesel is due to the incorporation of water which reduces NO X emissions by lowering the peak combustion temperatures. Water-blend fuel enhances fuel atomization by micro-explosion. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation [ABSTRACT FROM AUTHOR]

Abstract: The multi sources gas supply situation will exist for a long time in China''s city gas supply. The natural gas engine interchangeability problem and its possible impact on engine operation were analyzed, the index and the method of determining interchangeability for gas engine were introduced, three response measures for natural gas interchangeability in the terms of the domestic and international standards, engine manufacturers and end users were given in this paper: the relevant industry standards should be detailed, to increase the requirement of methane number (MN) range, the interchangeability between different gas source and the possible impact of end user should put into evaluation at the beginning of gas procurement; the natural gas component should be strictly defined in the engine design and manufacturing phase of engine manufacturers, and ensure that the engine and control system design meets changes of the gas composition; mixing inert gas such as N2 and CO2 in the end user side to increase the gas MN, thereby increasing its antiknock tendency, furthermore, the measures such as the installation of closed-loop control engine with oxygen sensor in the exhaust and adjust air-fuel ratio accurately and adjusting engine ignition timing, to adapt the changes in gas composition to ensure that the engine working conditions are not significantly affected, to meet the requirements of natural gas interchangeability. [Copyright &y& Elsevier]

Abstract: Environmental concern and availability of petroleum fuels have caused interests in the search for alternate fuels for internal combustion engines. Waste plastics are indispensable materials in the modern world and application in the industrial field is continually increasing. In this context, waste plastics are currently receiving renewed interest. As an alternative, non-biodegradable, and renewable fuel, waste plastic oil is receiving increasing attention. The waste plastic oil was compared with the petroleum products and found that it can also be used as fuel in compression ignition engines. In the present work, the influence of injection timing on the performance, emission and combustion characteristics of a single cylinder, four stroke, direct injection diesel engine has been experimentally investigated using waste plastic oil as a fuel. Tests were performed at four injection timings (23°,20°,17° and 14° bTDC). When compared to the standard injection timing of 23° BTDC the retarded injection timing of 14° bTDC resulted in decreased oxides of nitrogen, carbon monoxide and unburned hydrocarbon while the brake thermal efficiency, carbon dioxide and smoke increased under all the test conditions. [Copyright &y& Elsevier]

For further optimization of the combustion process, the information about the actually injected fuel quantity is desirable, especially in diesel engines equipped with direct injection technology. A miniaturized hot-film anemometer with a titanium/platinum metallization on a low-temperature co-fired ceramics substrate was developed and integrated into a Common Rail injection nozzle. The micro-flow sensor proved its high performance and its capability over the complete fuel quantity map of a high pressure hydraulic injection system where drive pulses for the operation of the injector range between 0.3 ms and 1.5 ms at injection pressures up to 135 MPa (1350 bar). In correspondence with measurements of an injection amount indicator integrated into the hydraulic test bench, the injected fuel quantity and the opening behaviour of the orifice were derived from the sensor signals as a function of injection parameters. Assuming a power law dependence on the fluid velocity for the flow-sensitive portion of the heat-transfer coefficient, a value of 0.5 for the exponent was determined experimentally, in excellent agreement with theoretical predictions. [ABSTRACT FROM AUTHOR]