Dual-injection: The flexible,bi-fuel concept for spark-ignition engines fuelled with various gasoline and biofuel blends

Dual-injection strategies in spark-ignition engines allow the in-cylinder blending of two different fuels at any blend ratio, when simultaneously combining port fuel injection (PFI) and direct-injection (DI). Either fuel can be used as the main fuel, depending on the engine demand and the fuel availability. This paper presents the preliminary investigation of such a flexible, bi-fuel concept using a single cylinder spark-ignition research engine. Gasoline has been used as the PFI fuel, while various mass fractions of gasoline, ethanol and 2,5-dimethylfuran (DMF) have been used in DI. The control of the excess air ratio during the in-cylinder mixing of two different fuels was realized using the cross-over theory of the carbon monoxide and oxygen emissions concentrations. The dual-injection results showed how the volumetric air flow rate, total input energy and indicated mean effective pressure (IMEP) increases with deceasing PFI mass fraction, regardless of the DI fuel. The indicated efficiency increases when using any ethanol fraction in DI and results in higher combustion and fuel conversion efficiencies compared to gasoline. Increasing the DMF mass fraction in DI reduces the combustion duration more significantly than with increased fractions of ethanol or gasoline in DI. The hydrocarbon (HC), oxides of nitrogen (NO_x) and carbon dioxide (CO₂) emissions mostly reduce when using any gasoline or ethanol fraction in DI. When using DMF, the HC emissions reduce, but the NO_x and CO₂ emissions increase.     

Performance of a common rail diesel engine using biodiesel of waste cooking oil and gasoline blend

High viscosity, high pour point and low volatility are the major application blocks for biodiesel. In this study gasoline is mixed with biodiesel and they can be soluble with each other at any proportion. Combustion and emission characteristics are investigated on a turbocharged, in-line 6-cylinder, common rail diesel engine. Results showed that pour points, viscosities and distillation temperatures obviously decrease with gasoline ratio. Peak combustion pressures of biodiesel/gasoline blend fuels increase slightly. Ignition delays, peak heat release rates and combustion temperatures increase at partial and medium loads. HC and CO emissions increase at partial and medium loads and drop at high loads. NO_X emissions of blend fuels grow by 4.2% and 6.7% compared with biodiesel averagely at 1400r/min, while soot emissions decline by 31.6% and 38.6%. For ultrafine particles (<220 nm), diameters to peak number concentration of blend fuels are smaller than that of biodiesel. Number concentrations decrease by 30% and 49% averagely compared to biodiesel. Especially, gasoline plays a significant reduction role on ultrafine particles at low and medium loads and soot emissions at high loads.     

Combustion and emission characteristics of an off-road diesel engine fuelled with biodiesel–diesel blends

In this work, the combustion and emission characteristics were studied in a 186FA diesel engine fuelled with biodiesel–diesel to examine the effect of the percentage of biodiesel in the blends, and the experimental investigation was conducted with various blending ratios of biodiesel under different operating conditions. In addition, the combustion noise of the diesel engine fuelled with biodiesel–diesel was analysed, and then the emission characteristics of NO_x and soot were studied through simulation analysis where the formation rate and distribution of NO_x and soot for pure diesel and B20 fuel were described. Based on the simulation data of the original diesel engine fuelled with B20 fuel, the swirl ratio and fuel injection timing were optimised and the technical measures were suggested to reduce the two different emissions simultaneously. The simulation results showed the emission characteristics were optimal when the swirl ratio was 2.7 and fuel injection timing was 7.5° degree of crank angle before top dead centre respectively.     

Combined impact of varying biogas mass flow rate and rice bran methyl esters blended with diesel on a dual-fuel engine

ABSTRACT

For fetching day-to-day energy needs, current energy requirement majorly depends on fossil fuels. But ambiguous matter like abating petroleum products and expanding air pollution has enforced the experts to strive for another fuel which can be used as an alternative or reduce the applications of fossil fuels. Considering the issues, the main objective of the present study is to find the feasibility by using blends of rice bran oil biodiesel and diesel which are used as pilot fuels by blending 10% and 20% biodiesel in fossil diesel and biogas, introduced as gaseous fuel by varying its mass flow rate in a dual-fuel engine mode. An experimentation study was carried out to find the performance and emission parameters of the engine relative to pure diesel. The results were very much similar to the majority of researchers who used biodiesel and gaseous fuels in a dual-fuel engine. Brake specific fuel consumption (BSFC) of the engine was noticed to have increased, while brake thermal efficiency was on the lower side in dual fuel mode in comparison with regular diesel. In relation with conventional diesel, it was noticed that combined effect of rice bran methyl esters and varying mass flow rate of biogas showed a decrement in NO _x and smoke emissions, whereas HC and CO exhalations were on higher side when biogas and biodiesel were utilized collectively in dual-fuel engine. Hence, it was concluded that combination of blends of biodiesel and diesel and introduction of biogas in the engine can be a promising combination which can be used as a substitute fuel for addressing future energy needs.     

Hydrogen dual-fuelling of compression ignition engines with emulsified biodiesel as pilot fuel

Dual-fuel compression ignition (CI) engine operation with hydrogen is a promising method of using hydrogen gas in CI engines via high-cetane pilot fuel ignition. However, hydrogen dual-fuel operation with neat pilot fuels typically produce: high NO_x emissions; and high combustion chamber pressure rise rates (leading to increased “Diesel knock” tendencies). While water-in-fuel emulsions have been used during normal CI engine operation to cool the charge and slow combustion rates in an effort to reduce NO_x emissions, these water-in-fuel emulsions have not been tested as pilot fuels during hydrogen dual-fuel combustion. In this work two water-in-biodiesel emulsions are tested as pilot fuels during hydrogen dual-fuel operation. Hydrogen dual-fuel operation generally produces at best comparable thermal efficiencies compared with normal CI engine operation, while the emulsified biodiesel pilot fuels generally increase thermal efficiencies when compared with the neat biodiesel pilot fuel during dual-fuel operation. There is also a clear reduction in NO_x emissions with emulsified pilot fuel use compared with the neat pilot fuel. The thermal efficiency increase is more apparent at higher engine speeds, while the NO_x reduction is more apparent at lower speeds. This is due to two conflicting effects (exclusive to emulsified pilot fuel) that occur in tandem. The first is the cooling effect of water vapourisation on the charge, while the second is the microexplosion phenomenon which enhances fuel-air mixing. The NO_x emission reduction is due to the emulsified pilot fuel lowering pressure rise rates compared with the neat pilot fuel, while the efficiency increase is due to a more homogeneous charge resulting from the violent microexplosion of the emulsified pilot fuel. Smoke, CO, HC and CO₂ emissions remain comparable to neat pilot fuel tests. Overall, emulsified pilot fuels can reduce NO_x emissions and increase thermal efficiencies, however not at the same instance and under different operating conditions. The general trends of reduced power output, reduced CO₂ and increased water vapour emission during hydrogen dual-fuel operation (with neat pilot fuels) are also maintained.     

Determination of ecological efficiency in internal combustion engines: The use of biodiesel

This paper evaluates and quantifies the environmental impact from the use of some renewable fuels and fossils fuels in internal combustion engines. The following fuels are evaluated: gasoline blended with anhydrous ethyl alcohol (anhydrous ethanol), conventional diesel fuel, biodiesel in pure form and blended with diesel fuel, and natural gas. For the case of biodiesel, its complete life cycle and the closed carbon cycle (photosynthesis) were considered. The ecological efficiency concept depends on the environmental impact caused by CO₂, SO₂, NO_x and particulate material (PM) emissions. The exhaust gases from internal combustion engines, in the case of the gasoline (blended with alcohol), biodiesel and biodiesel blended with conventional diesel, are the less polluting; on the other hand, the most polluting are those related to conventional diesel. They can cause serious problems to the environment because of their dangerous components for the human, animal and vegetable life. The resultant pollution of each one of the mentioned fuels are analyzed, considering separately CO₂, SO₂, NO_x and particulate material (PM) emissions. As conclusion, it is possible to calculate an environmental factor that represents, qualitatively and quantitative, the emissions in internal combustion engines that are mostly used in urban transport. Biodiesel in pure form (B100) and blended with conventional diesel as fuel for engines pollute less than conventional diesel fuel. The ecological efficiency for pure biodiesel (B100) is 86.75%; for biodiesel blended with conventional diesel fuel (B20, 20% biodiesel and 80% diesel), it is 78.79%. Finally, the ecological efficiency for conventional diesel, when used in engines, is 77.34%; for gasoline, it is 82.52%, and for natural gas, it is 91.95%. All these figures considered a thermal efficiency of 30% for the internal combustion engine.     

Assessment of the combustion performance of a room furnace operating on pipeline natural gas mixed with simulated biogas or hydrogen

With the inexorable depletion of fossil fuel and the increasing need to reduce greenhouse gas emissions, blending renewable fuels like biogas or renewable hydrogen into natural gas is of great interest. Due to various potential sources and low-carbon or even carbon-free properties, biogas and hydrogen are competitive energy carriers and promising gaseous fuels to replace pipeline natural gas in the future. From the perspective of end users and combustion device manufacturers, one of the major concerns is the influence of the renewable content on the combustion device performance. In addition, the upper limit of renewable gas content percentage in pipeline also interests policy makers and gas utility companies. Therefore, the present study is conducted to investigate the influence of renewable gas content on the operating performance of a residential room furnace. Evaluated combustion performance characteristics include ignition performance, blow-off/flashback limits, burner temperature and emissions (NO, NO₂, N₂O, CO, UHC, NH₃). The results show that 5% carbon dioxide and 15% (by volume) hydrogen can be added to natural gas separately without significant impacts. Above this amount, the risk of blow-off and flashback is the limiting factor. Generally speaking, carbon dioxide addition helps decrease NO_X emission but increases CO emission. However, hydrogen addition up to the amounts studied here in has minimal impact on NO_X and CO emissions.     

Combustion performance and emission reduction characteristics of automotive DME engine system

This article is a condensed overview of a dimethyl ether (DME) fuel application for a compression ignition diesel engine. In this review article, the spray, atomization, combustion and exhaust emissions characteristics from a DME-fueled engine are described, as well as the fundamental fuel properties including the vapor pressure, kinematic viscosity, cetane number, and the bulk modulus. DME fuel exists as gas phase at atmospheric state and it must be pressurized to supply the liquid DME to fuel injection system. In addition, DME-fueled engine needs the modification of fuel supply and injection system because the low viscosity of DME caused the leakage. Different fuel properties such as low density, viscosity and higher vapor pressure compared to diesel fuel induced the shorter spray tip penetration, wider cone angle, and smaller droplet size than diesel fuel. The ignition of DME fuel in combustion chamber starts in advance compared to diesel or biodiesel fueled compression ignition engine due to higher cetane number than diesel and biodiesel fuels. In addition, DME combustion is soot-free since it has no carbon–carbon bonds, and has lower HC and CO emissions than that of diesel combustion. The NO_x emission from DME-fueled combustion can be reduced by the application of EGR (exhaust gas recirculation). This article also describes various technologies to reduce NO_x emission from DME-fueled engines, such as the multiple injection strategy and premixed combustion. Finally, the development trends of DME-fueled vehicle are described with various experimental results and discussion for fuel properties, spray atomization characteristics, combustion performance, and exhaust emissions characteristics of DME fuel.     

Effects of hydrogenation of fossil fuels with hydrogen and hydroxy gas on performance and emissions of internal combustion engines

Energy security is an important consideration for development of future transport fuels. Among the all gaseous fuels hydrogen or hydroxy (HHO) gas is considered to be one of the clean alternative fuels. Hydrogen is very flammable gas and storing and transporting of hydrogen gas safely is very difficult. Today, vehicles using pure hydrogen as fuel require stations with compressed or liquefied hydrogen stocks at high pressures from hydrogen production centres established with large investments.Different electrode design and different electrolytes have been tested to find the best electrode design and electrolyte for higher amount of HHO production using same electric energy. HHO is used as an additional fuel without storage tanks in the four strokes, 4-cylinder compression ignition engine and two-stroke, one-cylinder spark ignition engine without any structural changes. Later, previously developed commercially available dry cell HHO reactor used as a fuel additive to neat diesel fuel and biodiesel fuel mixtures. HHO gas is used to hydrogenate the compressed natural gas (CNG) and different amounts of HHO-CNG fuel mixtures are used in a pilot injection CI engine. Pure diesel fuel and diesel fuel + biodiesel mixtures with different volumetric flow rates are also used as pilot injection fuel in the test engine. The effects of HHO enrichment on engine performance and emissions in compression-ignition and spark-ignition engines have been examined in detail. It is found from the experiments that plate type reactor with NaOH produced more HHO gas with the same amount of catalyst and electric energy. All experimental results from Gasoline and Diesel Engines show that performance and exhaust emission values have improved with hydroxy gas addition to the fossil fuels except NO_x exhaust emissions. The maximum average improvements in terms of performance and emissions of the gasoline and the diesel engine are both graphically and numerically expressed in results and discussions. The maximum average improvements obtained for brake power, brake torque and BSFC values of the gasoline engine were 27%, 32.4% and 16.3%, respectively. Furthermore, maximum improvements in performance data obtained with the use of HHO enriched biodiesel fuel mixture in diesel engine were 8.31% for brake power, 7.1% for brake torque and 10% for BSFC.     

Influence of biodiesel on engine combustion and emission characteristics

This paper discusses the influence of biodiesel on the engine combustion characteristics. The considered fuel is neat biodiesel from rapeseed oil. The considered engine is a bus diesel engine with injection M system. The engine characteristics are obtained by experiments and numerical simulation. The results obtained with biodiesel are compared to those obtained with mineral diesel under various operating regimes. In this way, the influences of biodiesel usage on the injection pressure, injection timing, ignition delay, in-cylinder gas pressure and temperature, heat release rate, exhaust gas temperatures, harmful emissions, specific fuel consumption, and on engine power are analyzed. Furthermore, the relationships among fuel properties, injection and combustion characteristics, harmful emissions, and other engine performance are determined. Special attention is given to possible explanations of higher NO_x emission in spite of lower in-cylinder gas temperature.     

The effect of adding dimethyl carbonate (DMC) and ethanol to unleaded gasoline on exhaust emission

Oxygen containing additives are usually used to improve gasoline’s performance and reduce exhaust emissions. In this study, the effect of oxygen containing additives on gasoline blended fuels on exhaust emissions was investigated for different engine speeds in a single cylinder, four-stroke, spark-ignition engine. The results indicate that CO and HC exhaust emissions are lower with the use of ethanol–gasoline and DMC–gasoline blended fuels as compared to the use of unleaded gasoline. On the other hand, the effect of ethanol–gasoline and DMC–gasoline blended fuels on NO_X exhaust emission is insignificant. Using oxygen containing additives can increase fuel consumption as a result of the heating value of the blended fuels being lower than that of unleaded gasoline.     

An insight on hydrogen fuel injection techniques with SCR system for NOX reduction in a hydrogen–diesel dual fuel engine

Internal combustion engines continue to dominate in many fields like transportation, agriculture and power generation. Among the various alternative fuels, hydrogen is a long-term renewable and less polluting fuel (Produced from renewable energy sources). In the present experimental investigation, the performance and emission characteristics were studied on a direct injection diesel engine in dual fuel mode with hydrogen inducted along with air adopting carburetion, timed port and manifold injection techniques. Results showed that in timed port injection, the specific energy consumption reduces by 15% and smoke level by 18%. The brake thermal efficiency and NO_X increases by 17% and 34% respectively compared to baseline diesel. The variation in performance between port and manifold injection is not significant. The unburnt hydrocarbons and carbon monoxide emissions are lesser in port injection. The oxides of nitrogen are higher in hydrogen operation (both port and manifold injection) compared to diesel engine. In order to reduce the NO_X emissions, a selective catalytic converter was used in hydrogen port fuel injection. The NO_X emission reduced upto a maximum of 74% for ANR (ratio of flow rate of ammonia to the flow rate of NO) of 1.1 with a marginal reduction in efficiency. Selective catalytic reduction technique has been found to be effective in reducing the NO_X emission from hydrogen fueled diesel engines.     

Effect of manifold injection of hydrogen gas in producer gas and neem biodiesel fueled CRDI dual fuel engine

The high flammability of hydrogen gas gives it a steady flow without throttling in engines while operating. Such engines also include different induction/injection methods. Hydrogen fuels are encouraging fuel for applications of diesel engines in dual fuel mode operation. Engines operating with dual fuel can replace pilot injection of liquid fuel with gaseous fuels, significantly being eco-friendly. Lower particulate matter (PM) and nitrogen oxides (NO_x) emissions are the significant advantages of operating with dual fuel.Consequently, fuels used in the present work are renewable and can generate power for different applications. Hydrogen being gaseous fuel acts as an alternative and shows fascinating use along with diesel to operate the engines with lower emissions. Such engines can also be operated either by injection or induction on compression of gaseous fuels for combustion by initiating with the pilot amount of biodiesel. Present work highlights the experimental investigation conducted on dual fuel mode operation of diesel engine using Neem Oil Methyl Ester (NeOME) and producer gas with enriched hydrogen gas combination. Experiments were performed at four different manifold hydrogen gas injection timings of TDC, 5°aTDC, 10°aTDC and 15°aTDC and three injection durations of 30°CA, 60°CA, and 90°CA. Compared to baseline operation, improvement in engine performance was evaluated in combustion and its emission characteristics. Current experimental investigations revealed that the 10°aTDC hydrogen manifold injection with 60°CA injection duration showed better performance. The BTE of diesel + PG and NeOME + PG operation was found to be 28% and 23%, respectively, and the emissions level were reduced to 25.4%, 14.6%, 54.6%, and 26.8% for CO, HC, smoke, and NO_x, respectively.     

汽油机燃用含氧混合燃料时燃烧特性和碳氢排放的研究

开展了汽油机燃用含氧混合燃料时燃烧特性和碳氢排放的研究 ,分析了质量燃烧率和发动机碳氢排放。基于实测示功图的计算结果表明 ,与汽油相比 ,燃用汽油 乙醚混合燃料可明显缩短火焰发展角和快速燃烧角。当汽油中加入的醇类燃料比例较小时 ,与燃用汽油相比 ,可缩短火焰发展角和明显缩短快速燃烧角 ;而当汽油中加入的醇类燃料比例较大时 ,反而会增加火焰发展角和快速燃烧角。试验结果表明 ,与燃用汽油相比 ,燃用含氧混合燃料可降低发动机碳氢排放量 ,燃用汽油 乙醚混合燃料比燃用汽油 醇类混合燃料具有更低的碳氢排放。     

Hydrogen supplemented natural gas effect on a DI diesel engine operating under dual fuel mode with a biodiesel pilot fuel

In order to slow down the continuing environmental deterioration, regulations for pollutant emissions limitations are increasingly rigorous. The development of new alternative fuels for internal combustion engines is a very interesting solution not only to overcome the pollution problem but also because of the petroleum shortage. In this context, the present work investigates the improvement of a DI diesel engine operating at constant speed (1500 rpm) and under dual fuel mode with eucalyptus biodiesel and natural gas (NG) enriched by various H₂ quantities (15, 25 and 30 by v%). The eucalyptus biodiesel quantity injected into the engine cylinder is kept constant, to supply around 10% of the engine nominal power, for all examined engine loads. The engine load is further increased using only the gaseous fuel (NG+H₂), which is introduced with the intake air. The effect of H₂/NG blending ratio on the combustion parameters, performance and pollutant emissions of the engine is investigated and compared with those of pure NG case. An important benefit in terms of brake specific fuel consumption, reaching a decrease of 4–10% with the 25% H₂ blend compared to the pure NG case, is achieved. Concerning the pollutant emissions, NG enrichment with H₂ is an efficient solution to enhance the combustion process and hence reduce carbon monoxide, unburned hydrocarbon and soot emissions at high loads where they are important for pure NG. However for the nitrogen oxide emissions, NG blending with H₂ is attractive only at low and medium loads where their levels are lower than pure NG.     

Review of NOx reduction technologies in CI engines fuelled with oxygenated biomass fuels

Oxygenated fuels like biodiesel and alcohols have the potential to provide a reliable and a cost effective alternative to India's increasing future energy demands. They have a prospective future since they are renewable and can be produced easily in India's rural areas. Due to rapid industrialization and the increased number of vehicles on the road, the energy needs of the country are increasing rapidly. Oxygenated fuels can substantially replace the large demand for diesel to generate power for the industries and to fuel diesel engines of the vehicles. In spite of the many advantages of using them, most of the researchers have reported higher NO_x emissions, which is a deterrent to the market expansion of these fuels. The present program aims to review the NO_x emissions from the CI engines fuelled with oxygenated fuels. To meet the stringent emission norms, the various NO_x reduction technologies like use of additives, retarded fuel injection timing, biodiesel emulsion with water, and exhaust gas recirculation are reviewed. The results of the most effective and low cost technique of EGR in DI diesel engine fuelled with biodiesel–diesel blends and tri-compound oxygenated diesel fuel blends (ethanol–biodiesel–diesel fuel blends and methanol–biodiesel–diesel fuel blends) are presented.     

Experimental investigations on combustion, performance and emissions characteristics of neat karanji biodiesel and its methanol blend in a diesel engine

The increased focus on alternative fuels research in the recent years are mainly driven by escalating crude oil prices, stringent emission norms and the concern on clean environment. The processed form of vegetable oil (biodiesel) has emerged as a potential substitute for diesel fuel on account of its renewable source and lesser emissions. The experimental work reported here has been carried out on a turbocharged, direct injection, multi-cylinder truck diesel engine fitted with mechanical distributor type fuel injection pump using biodiesel-methanol blend and neat karanji oil derived biodiesel under constant speed and varying load conditions without altering injection timings. The results of the experimental investigation indicate that the ignition delay for biodiesel-methanol blend is slightly higher as compared to neat biodiesel and the maximum increase is limited to 1 deg. CA. The maximum rate of pressure rise follow a trend of the ignition delay variations at these operating conditions. However, the peak cylinder pressure and peak energy release rate decreases for biodiesel-methanol blend. In general, a delayed start of combustion and lower combustion duration are observed for biodiesel-methanol blend compared to neat biodiesel fuel. A maximum thermal efficiency increase of 4.2% due to 10% methanol addition in the biodiesel is seen at 80% load and 16.67 s⁻¹ engine speed. The unburnt hydrocarbon and carbon monoxide emissions are slightly higher for the methanol blend compared to neat biodiesel at low load conditions whereas at higher load conditions unburnt hydrocarbon emissions are comparable for the two fuels and carbon monoxide emissions decrease significantly for the methanol blend. A significant reduction in nitric oxide and smoke emissions are observed with the biodiesel-methanol blend investigated.     

Performance and emission studies on port injection of hydrogen with varied flow rates with Diesel as an ignition source

Automobiles are one of the major sources of air pollution in the environment. In addition CO₂ emission, a product of complete combustion also has become a serious issue due to global warming effect. Hence the search for cleaner alternative fuels has become mandatory. Hydrogen is expected to be one of the most important fuels in the near future for solving the problems of air pollution and greenhouse gas problems (carbon dioxide), thereby protecting the environment. Hence in the present work, an experimental investigation has been carried out using hydrogen in the dual fuel mode in a Diesel engine system. In the study, a Diesel engine was converted into a dual fuel engine and hydrogen fuel was injected into the intake port while Diesel was injected directly inside the combustion chamber during the compression stroke. Diesel injected inside the combustion chamber will undergo combustion first which in-turn would ignite the hydrogen that will also assist the Diesel combustion. Using electronic control unit (ECU), the injection timings and injection durations were varied for hydrogen injection while for Diesel the injection timing was 23° crank angle (CA) before injection top dead centre (BITDC). Based on the performance, combustion and emission characteristics, the optimized injection timing was found to be 5° CA before gas exchange top dead centre (BGTDC) with injection duration of 30° CA for hydrogen Diesel dual fuel operation. The optimum hydrogen flow rate was found to be 7.5 lpm. Results indicate that the brake thermal efficiency in hydrogen Diesel dual fuel operation increases by 15% compared to Diesel fuel at 75% load. The NO_X emissions were higher by 1–2% in dual fuel operation at full load compared to Diesel. Smoke emissions are lower in the entire load spectra due to the absence of carbon in hydrogen fuel. The carbon monoxide (CO), carbon dioxide (CO₂) emissions were lesser in hydrogen Diesel dual fuel operation compared to Diesel. The use of hydrogen in the dual fuel mode in a Diesel engine improves the performance and reduces the exhaust emissions from the engine except for HC and NO_X emissions.     

Evaluation of hydrogen-containing NaBH4 and oxygen-containing alcohols (CH3OH,C2H5OH) as fuel additives in a gasoline engine

The aim of this study is to obtain alternative fuels with hydrogen-containing (NaBH₄) and oxygen-containing (ethanol, methanol) fuel additives and to test these fuels in a gasoline engine. For this purpose, each of the NaBH₄ added ethanol and methanol solutions was added to pure gasoline at a volume of 10% and mixed fuels named SE10 and SM10 were obtained, respectively. The obtained SE10 and SM10 mixed fuels were tested in a spark ignition engine and the performance and emission effects of the fuels were compared with the pure gasoline fueled engine test data. When the test results of the mixture fuel engine were compared with the test results of the engine running with pure gasoline, the torque of the SE10 fuel engine decreased compared to the pure gasoline engine, while the torque of the SM10 blended engine increased. In addition, while the exhaust gas temperatures of both blended fuels decreased, their specific fuel consumption and thermal efficiency increased. On the other hand, adding NaBH₄ doped ethanol and methanol solutions to pure gasoline resulted in better combustion, reductions in CO emissions of SE10 and SM10 blended fuels by 31.04% and 53.7%, but CO₂ emissions increased by 11.20% and 19.51% respectively. In addition, NO_x emissions of SE10 and SM10 blended fuels decreased by 15.17% and 8.73%, respectively.     

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO_X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO_X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.