Experimental investigation on biogas enrichment with hydrogen for improving the combustion in diesel engine operating under dual fuel mode

Biogas valorization as fuel for internal combustion engines is one of the alternative fuels, which could be an interesting way to cope the fossil fuel depletion and the current environmental degradation. In this circumstance, an experimental investigation is achieved on a single cylinder DI diesel engine running under dual fuel mode with a focus on the improvement of biogas/diesel fuel combustion by hydrogen enrichment. In the present investigation, the mixture of biogas, containing 70% CH₄ and 30% CO₂, is blended with the desired amount of H₂ (up to 10, 15 and 20% by volume) by using MTI 200 analytical instrument gas chromatograph, which flow thereafter towards the engine intake manifold and mix with the intake air. Depending on engine load conditions, the volumetric composition of the inducted gaseous fraction is 20–50% biogas, 2–10% H₂ and 45–78% air. Near the end of the compression stroke, a small amount of diesel pilot fuel is injected to initiate the combustion of the gas–air mixture. Firstly, the engine was tested on conventional diesel mode (baseline case) and then under dual fuel mode using the biogas. Consequently, hydrogen has partially enriched the biogas. Combustion characteristics, performance parameters and pollutant emissions were investigated in-depth and compared. The results have shown that biogas enriched with 20% H₂ leads to 20% decrease of methane content in the overall exhaust emissions, associated with an improvement in engine performance. The emission levels of unburned hydrocarbon (UHC) and carbon monoxide (CO) are decreased up to 25% and 30% respectively. When the equivalence ratio is increased, a supplement decrease in UHC and CO emissions is achieved up to 28% and 30% respectively when loading the engine at 60%.     

Effect of addition of di-tert butyl peroxide (DTBP) on performance and exhaust emissions of dual fuel diesel engine with hydrogen as a secondary fuel

Today, the world faces a number of challenges on global level. The optimum replacement for fossil fuels is one of these challenges. Hydrogen in the past has been and continues to be used by numerous researchers in diesel engines. However, high NO_x emissions and low replacement of hydrogen fuel are the concern with many researchers. In the present study, di-tert butyl peroxide (DTBP) has been used as an additive in diesel fuel, to investigate the performance and exhaust emissions of the diesel engine working on dual fuel mode by using hydrogen as secondary fuel. At low, medium and high load conditions, the maximum increase in brake thermal efficiency was observed to be 87.50%, 14.68% and 5.89% respectively for 1%, 3% and 5% of additive (DTBP) by 40% of hydrogen fuel substitution, as compared to diesel fuel operation. Moreover, by addition of 4% di-tert butyl peroxide (DTBP) in diesel engine working on dual fuel mode showed 33.82%, 10.27% and 29.27% reduction in NO_x emission at low, medium and high load conditions respectively at 40% hydrogen substitution, as compared to dual fuel operation using hydrogen as secondary fuel without additives. By addition of 5% additive (DTBP) at 69% load condition and 40% hydrogen substitution, reduces CO emissions by 38.66% as compared to dual fuel operation, using hydrogen as secondary fuel.     

Experimental and computational study on the enhancement of engine characteristics by hydrogen enrichment in a biogas fuelled spark ignition engine

Limitations on the upgradation of biogas to biomethane in terms of cost effectiveness and technology maturity levels for stationary power generation purpose in rural applications have redirected the research focus towards possibilities for enhancement of biogas fuel quality by blending with superior quality fuels. In this work, the effect of hydrogen enrichment on performance, combustion and emission characteristics of a single-cylinder, four-stroke, water-cooled, biogas fuelled spark-ignition engine operated at the compression ratio of 10:1 and 1500 rpm has been evaluated using experimental and computational (CFD) studies. The percentage share of hydrogen in the inducted biogas fuel mixture was increased from 0 to 30%, and engine characteristics with pure methane fuel was considered as a baseline for comparative analysis. The CFD model is developed in Converge CFD software for a better understanding on combustion phenomenon and is validated with experimental data. In addition, the percentage share of hydrogen enrichment which would serve as a compromise between biogas upgradation cost and engine characteristics is also identified. The results of study indicated an enhancement in combustion characteristics (peak in-cylinder pressure increased; COV_IMEP reduced from 9.87% to 1.66%; flame initiation and combustion durations reduced) and emission characteristics (hydrocarbon emissions reduced, and NOx emissions increased but still lower than pure methane) with increase in hydrogen share from 0 to 30% in biogas fuelled SI engine. Flame propagation speed increased and combustion duration reduced with hydrogen supplementation and the same was evident from the results of the CFD model. Performance of the engine increased with increase in hydrogen share up to 20% and further increment in hydrogen share degraded the performance, owing to heat losses and the enhancement in combustion characteristics were relatively small. Overall, it was found that 20% blending of hydrogen in the inducted biogas fuel mixture will be effective in enhancing the engine characteristics of biogas fuelled engines for stationary power generation applications and it holds a good compromise between biogas upgradation cost and engine performance.     

The utilization of hydrogen in hydrogen/diesel dual fuel engine

A hydrogen fueled internal combustion engine has great advantages on exhaust emissions including carbon dioxide (CO₂) emission in comparison with a conventional engine fueling fossil fuel. In addition, if it is compared with a hydrogen fuel cell, the hydrogen engine has some advantages on price, power density, and required purity of hydrogen. Therefore, they expect that hydrogen will be utilized for several applications, especially for a combined heat and power (CHP) system which currently uses diesel or natural gas as a fuel.A final goal of this study is to develop combustion technologies of hydrogen in an internal combustion engine with high efficiency and clean emission. This study especially focuses on a diesel dual fuel (DDF) combustion technology. The DDF combustion technology uses two different fuels. One of them is diesel fuel, and the other one is hydrogen in this study. Because the DDF engine is not customized for hydrogen which has significant flammability, it is concerned that serious problems occur in the hydrogen DDF engine such as abnormal combustion, worse emission and thermal efficiency.In this study, a single cylinder diesel engine is used with gas injectors at an intake port to evaluate performance swung the hydrogen DDF engine with changing conditions of amount of hydrogen injected, engine speed, and engine loads. The engine experiments show that the hydrogen DDF operation could achieve higher thermal efficiency than a conventional diesel operation at relatively high engine load conditions. However, it is also shown that pre-ignition with relatively high input energy fraction of hydrogen occurred before diesel fuel injection and its ignition. Therefore, such abnormal combustion limited amount of hydrogen injected. Fire-deck temperature was measured to investigate causal relationship between fire-deck temperature and occurrence of pre-ignition with changing operative conditions of the hydrogen DDF engine.     

A numerical study on the effects of constant volume combustion phase on performance and emissions characteristics of a diesel-hydrogen dual-fuel engine

A detailed numerical study is carried out to investigate the performance of a diesel-hydrogen dual fuel (DF) compression ignition engine operating under a novel combustion strategy in which diesel injection and most of the combustion occur at a constant volume. A detailed validation of the numerical model for diesel-hydrogen DF engine operation has been carried out. Then a parametric study has been performed to investigate the effects of the constant volume combustion phase (CVCP) at up to 90% hydrogen energy share (HES) on engine performance and emissions at low and high load with comparisons to the conventional engine. The results demonstrate that the CVCP strategy can improve thermal efficiency at all HESs and load conditions with far lower carbon-based emissions. Conventional DF engines struggle at low load high HESs due to the reduced diesel injection failing to ignite the leaner premixed charge. Through use of a CVCP thermal efficiency at low load 90% HES increased from 11% to 38% with considerably reduced hydrogen emission due to the increased temperatures and pressures allowing for the wholesale ignition of the hydrogen-air mix. It was also found that increasing the time allowed for combustion within the CVCP, by advancing the diesel injection, can lead to even further thermal efficiency gains while not negatively impacting emissions.     

Combustion,performance and emission analysis of dual fuel engine using tsrb biogas

In this work, an experimental investigation has been carried out to reduce the emission and improve the performance and combustion characteristics of direct injection compression ignition (DICI) engine fuelled with diesel and biogas in dual fuel mode. The anaerobic digestion method was used to produce biogas from tamarind seed and rice bran (TSRB). The diesel is injected by conventional injector setup and the biogas is inducted through the intake manifold with air in different flow rates such as 0.25, 0.50, 0.75, and 1.0 kg/hr. The emission, combustion, and performance test is conducted with a different flow rate of biogas with diesel and compared with diesel. Results show that the smoke and Nox emissions are lowered by 7.1and 23.27%, respectively compared to diesel mode.     

Dual fuel mode operation in diesel engines using renewable fuels: Rubber seed oil and coir-pith producer gas

Partial combustion of biomass in the gasifier generates producer gas that can be used as supplementary or sole fuel for internal combustion engines. Dual fuel mode operation using coir-pith derived producer gas and rubber seed oil as pilot fuel was analyzed for various producer gas–air flow ratios and at different load conditions. The engine is experimentally optimized with respect to maximum pilot fuel savings in the dual fuel mode operation. The performance and emission characteristics of the dual fuel engine are compared with that of diesel engine at different load conditions. Specific energy consumption in the dual-fuel mode of operation with oil-coir-pith operation is found to be in the higher side at all load conditions. Exhaust emission was found to be higher in the case of dual fuel mode of operation as compared to neat diesel/oil operation. Engine performance characteristics are inferior in fully renewable fueled engine operation but it suitable for stationary engine application, particularly power generation.     

Combustion,performance and emissions of a diesel engine with H2, CH4 and H2–CH4 addition

Experiments were conducted to investigate the combustion and emission characteristics of a diesel engine with addition of hydrogen or methane for dual-fuel operation, and mixtures of hydrogen–methane for tri-fuel operation. The in-cylinder pressure and heat release rate change slightly at low to medium loads but increase dramatically at high load owing to the high combustion temperature and high quantity of pilot diesel fuel which contribute to better combustion of the gaseous fuels. The performance of the engine with tri-fuel operation at 30% load improves with the increase of hydrogen fraction in methane and is always higher than that with dual-fuel operations. Compared with ULSD–CH₄ operation, hydrogen addition in methane contributes to a reduction of CO/CO₂/HC emissions without penalty on NO_x emission. Dual-fuel and tri-fuel operations suppress particle emission to the similar extent. All the gaseous fuels reduce the geometry mean diameter and total number concentration of diesel particulate. Tri-fuel operation with 30% hydrogen addition in methane is observed to be the best fuel in reducing particulate and NO_x emissions at 70 and 90% loads.     

Studies on the effect of hydrogen induction on performance,emission and combustion behaviour of a WCO emulsion based dual fuel engine

This paper aims at studying the effect of hydrogen induction on engine performance, emission and combustion behaviour of a diesel engine fuelled with the emulsion of used palm oil (called as WCO-waste cooking oil) as pilot fuel and hydrogen as primary fuel. A single cylinder water-cooled direct injection diesel engine was tested at 100% and 40% loads. Results were compared with neat diesel, neat WCO and WCO emulsion at both loads in single fuel operation. WCO emulsion in single fuel mode indicated improvement in performance and reduction in all emissions as compared to neat WCO. Dual fuel operation with hydrogen induction further reduced the emissions of smoke HC and CO with WCO as pilot fuel at all power outputs. However, hydrogen induction resulted in reduced thermal efficiency at 40% load. WCO emulsion showed higher ignition delay as compared to neat WCO. Dual fuel operation with hydrogen induction increased the ignition delay further. Heat release pattern showed higher premixed combustion rate with hydrogen induction mainly at high power outputs. Premixed combustion rate became very high at higher rates of hydrogen admission mainly at high power output. In general, hydrogen induction showed superior performance at high power output and inferior performance at low power output with WCO emulsion as injected fuel.     

Effect of natural gas enrichment with hydrogen on combustion characteristics of a dual fuel diesel engine

Environmental benefits are one of the main motivations encouraging the use of natural gas as fuel for internal combustion engines. In addition to the better impact on pollution, natural gas is available in many areas. In this context, the present work investigates the effect of hydrogen addition to natural gas in dual fuel mode, on combustion characteristics improvement, in relation with engine performance. Various hydrogen fractions (10, 20 and 30 by v%) are examined. Results showed that natural gas enrichment with hydrogen leads in general to an improved gaseous fuel combustion, which corresponds to an enhanced heat release rate during gaseous fuel premixed phase, resulting in an increase in the in-cylinder peak pressure, especially at high engine load (4.1 bar at 70% load). The highest cumulative and rate of heat release correspond to 10% Hydrogen addition. The combustion duration of gaseous fuel combustion phase is reduced for all hydrogen blends. Moreover, this technique resulted in better combustion stability. For all hydrogen test blends, COV_IMEP does not exceed 10%. However, no major effect on combustion noise was noticed and the ignition delay was not affected significantly. Regarding performance, an important improvement in energy conversion was obtained with almost all hydrogen blends as a result of improved gaseous fuel combustion. A maximum thermal efficiency of 32.5%, almost similar to the one under diesel operation, and a minimum fuel consumption of 236 g/kWh, are achieved with 10% hydrogen enrichment at 70% engine load.     

Assessing the effects of partially decarbonising a diesel engine by co-fuelling with dissociated ammonia

The proven feasibility of ammonia combustion in compression-ignition engines has led to it being considered as a carbon-free replacement for diesel fuel. Due to its high auto-ignition temperature, however, a more realistic strategy would be to aim for a step-change reduction in carbon emissions by co-fuelling a diesel engine with ammonia. In assessing this strategy, ammonia gas was introduced into the air-intake manifold of a compression-ignition engine, while diesel fuel was injected directly into the cylinder to ignite the mixture. By substituting only 3% of the air intake by ammonia, the diesel consumption and the CO₂ emissions decreased by 15%. The combustion and emission characteristics were then compared when the same percentage of air intake (by mass) was substituted by either dissociated ammonia (a mixture of H₂, N₂ with small percentages of NH₃) or pure hydrogen, to mimic the other possible forms in which the co-fuel can be delivered to the engine. The addition of pure hydrogen resulted in the best engine performance, both in terms of combustion efficiency and regulated emission quality. The thermal combustion efficiency declined by only ∼0.5% when the H₂ was replaced by undissociated ammonia at low load, but N₂O now appeared in the emissions. Co-fuelling the engine with dissociated ammonia may provide the ideal compromise in terms of thermal combustion efficiency and emission quality, while also providing a waste-heat recovery mechanism.     

生物制气-柴油双燃料发动机燃烧及排放分析

采用气化炉热解气化各种农林废弃的生物质,得到可燃生物制气。将柴油机改制成双燃料发动机,用生物制气作为主要燃料,由柴油引燃。测量生物制气-柴油双燃料发动机在最大扭矩转速时的气缸压力及废气排放,分析燃烧特性及对排放物生成的影响,并对比分析柴油机与双燃料发动机的差别。     

A renewable pathway towards increased utilization of hydrogen in diesel engines

In the present work, dual fuel operation of a diesel engine has been experimentally investigated using biodiesel and hydrogen as the test fuels. Jatropha Curcas biodiesel is used as the pilot fuel, which is directly injected in the combustion chamber using conventional diesel injector. The main fuel (hydrogen) is injected in the intake manifold using a hydrogen injector and electronic control unit. In dual fuel mode, engine operations are studied at varying engine loads at the maximum pilot fuel substitution conditions. The engine performance parameters such as maximum pilot fuel substitution, brake thermal efficiency and brake specific energy consumption are investigated. On emission side, oxides of nitrogen, hydrocarbon, carbon monoxide and smoke emissions are analysed. Based on the results, it is found that biodiesel-hydrogen dual fuel engine could utilize up to 80.7% and 24.5% hydrogen (by energy share) at low and high loads respectively along with improved brake thermal efficiency. Furthermore, hydrocarbon, carbon monoxide and smoke emissions are significantly reduced compared to single fuel diesel engine operation. Exhaust gas recirculation (EGR) has also been studied with biodiesel-hydrogen dual fuel engine operations. It is found that EGR could improve the utilization of hydrogen in dual fuel engine, especially at the high loads. The effect of EGR is also found to reduce high nitrogen oxide emissions from the dual fuel engine and brake thermal efficiency is not significantly affected.     

生物制气-柴油双燃料发动机NOx计算模型

采用气化炉热解气化各种农林废弃的生物质,产生可燃生物制气,作为双燃料发动机的主要燃料。双燃料发动机由单缸、四冲程、水冷、直喷式柴油机改装,生物制气通入发动机进气管,在进气过程中吸入气缸。在油滴蒸发准维燃烧模型的基础上,结合单区模型和详细化学反应动力学机理,建立生物制气-柴油双燃料发动机的NOx生成模型,计算结果与试验结果吻合较好。供油提前角提前,生物制气-柴油双燃料发动机NOx排放量增加;引燃柴油量减小时,NOx排放量减小。     

植物油发动机在JS6608汽车上应用的试验研究

柴油机直接燃用植物油燃料,存在启动困难、在怠速、低转速和小负荷等工况时燃烧排放性能差等问题。本文对原车柴油机燃料供给系统进行改进设计,应用控制单元对燃油供给系统进行控制,在启动、怠速、低转速和小负荷时给发动机供柴油,中高负荷时给发动机供植物油,实现柴油和植物油燃料的双供给。改装后整车道路试验表明,燃用植物油汽车运行可靠,动力性、经济性与原车相当,在中高负荷时燃烧和排放特性优于柴油车。     

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.     

Synergistic effect of hydrogen induction with biofuel obtained from winery waste (grapeseed oil) for CI engine application

The purpose of this study is to experimentally investigate the use of grapeseed oil as a fuel substitute obtained from biomass waste from winery industry and the synergic effect of hydrogen addition for compression ignition engine application. The experiments were carried out in a single cylinder, four stroke diesel engine for various loads and energy share of hydrogen. Combustion, performance and emission characteristics of grapeseed biodiesel, neat grapeseed oil and diesel have been analysed and compared with the results obtained with hydrogen induction in the intake manifold in dual fuel mode. At full load, maximum brake thermal efficiency of the engine with diesel, grapeseed biodiesel and neat grapeseed oil has increased from 32.34%, 30.28% and 25.94% to 36.04%, 33.97% and 30.95% for a maximum hydrogen energy share of 14.46%, 14.1% and 12.8% respectively. Although there is an increasing trend in Nitric Oxide emission with hydrogen induction, smoke, brake specific hydrocarbon, carbon monoxide, and carbon dioxide emissions respectively, reduces. Nitric oxide emission of Grapeseed biodiesel with maximum hydrogen share at full load is higher by 43.61% and smoke emission lower by 19.73% compared to biodiesel operation without hydrogen induction.     

机电联合控制LPG-柴油双燃料增压发动机的研究

对增压柴油机燃用 L PG-柴油双燃料、采用 2种机电联合控制方案进行了较为深入的研究 ,对比分析了原柴油机和机电联合控制 L PG-柴油双燃料发动机的动力性、燃料经济性和碳烟、NOx、CO、HC排放。机电联合控制方案 1的试验研究表明 :掺烧 L PG后 ,可以显著地降低柴油机的碳烟排放 ;但在小负荷范围内 ,燃料消耗率略有增加 ,HC、CO排放增加较多。机电联合控制方案 2的试验研究表明 :双燃料发动机和原柴油机外特性相比 ,转矩几乎不降低 ,燃料消耗率略有下降 ,碳烟排放显著降低 ,NOx、CO排放变化不大 ,HC排放增加 ;双燃料发动机和原柴油机负荷特性相比 ,燃料消耗率在小负荷范围内持平而在中等以上负荷略有下降 ,碳烟排放显著降低 ,NOx 排放变化不大 ,HC、CO排放在小负荷范围内基本相同而在中等以上负荷略有增加。     

An experimental investigation of the combustion process of a heavy-duty diesel engine enriched with H2

This paper investigated the effect of hydrogen (H₂) addition on the combustion process of a heavy-duty diesel engine. The addition of a small amount of H₂ was shown to have a mild effect on the cylinder pressure and combustion process. When operated at high load, the addition of a relatively large amount of H₂ substantially increased the peak cylinder pressure and the peak heat release rate. Compared to the two-stage combustion process of diesel engines, a featured three-stage combustion process of the H₂–diesel dual fuel engine was observed. The extremely high peak heat release rate represented a combination of diesel diffusion combustion and the premixed combustion of H₂ consumed by multiple turbulent flames, which substantially enhanced the combustion process of H₂–diesel dual fuel engine. However, the addition of a relatively large amount of H₂ at low load did not change the two-stage heat release process pattern. The premixed combustion was dramatically inhibited while the diffusion combustion was slightly enhanced and elongated. The substantially reduced peak cylinder pressure at low load was due to the deteriorated premixed combustion.     

氢气／柴油发动机NOx和微粒排放特性的数值模拟

在柴油引燃氢气／柴油发动机中,氢气的引入会对氢气／空气混合气氛围中的柴油雾化特性和燃烧特性产生直接的影响,进而对发动机的排放产生影响．应用改进的KIVA．3V程序,对氢气／柴油发动机的N0x和微粒排放特性进行了模拟研究,分析了氢气的引入对氢气／柴油发动机N0。和微粒排放的影响．结果表明：低负荷时,氢气替代部分柴油后,发...