天然气掺氢发动机的性能研究

以台架试验的方法,对不同负荷与点火提前角下天然气掺氢发动机的经济性和排放特性进行了研究,试验中使用了掺氢比为0%～40%的天然气掺氢混合燃料。试验结果表明,随着掺氢比的增加,燃气消耗率呈降低趋势,发动机的经济性得到明显的改善;在不同负荷下,随着掺氢比的增加,NOx与CO的排放都呈增加趋势,CH4的排放呈降低趋势。掺氢比一定时,随着点火提前角和掺氢比的增加,NOx、CH4与CO排放都呈增加趋势,优化点火提前角可以改善天然气发动机的排放。     

引燃柴油量对甲醇/柴油双燃料发动机性能和排放的影响

在一台TY1100型直喷柴油机上,开展了引燃柴油量对柴油引燃甲醇双燃料发动机性能和排放影响的研究。试验结果表明:引燃柴油比例为28.9%~48.2%时,发动机可获得较好的动力性,甲醇质量掺比可达73.3%~83.2%。与原柴油机相比,双燃料发动机的碳烟排放大幅度下降,NOx排放降低,而HC和CO排放增加。高负荷时发动机有效热效率增加而CO排放基本相当。在同一引燃柴油量下,HC排放呈先增加后减少的趋势,增加引燃柴油量,可以提高发动机低负荷时的有效热效率和降低HC排放,但在全负荷时,会导致NOx排放增加。     

火花点火发动机燃用CNG/H_2混合燃料配合EGR的性能和排放研究

在一台火花点火天然气发动机上开展了不同掺氢比和EGR率下发动机性能和排放的试验研究。研究结果表明:引入EGR后发动机输出功率下降,但掺氢可以提高大EGR工况下发动机的输出功率。有效热效率随EGR率的增大呈现先升高后降低的趋势;小EGR率下,有效热效率随掺氢比的增加而降低,而大EGR率下,有效热效率随掺氢比的增大而升高。天然气掺氢后NOx排放增加,EGR引入使NOx排放降低,这种降低作用在大掺氢比下更显著。因此,相对于小EGR率工况,大EGR率工况下天然气掺氢表现出更好的性能和排放效果。HC排放随EGR率的增大而增加,随掺氢比的增加而降低。CO和CO2都随EGR率的增加变化不大,随掺氢比的增加而降低。研究表明,天然气掺氢结合EGR可实现火花点火发动机高效低污染燃烧,并能满足欧Ⅳ排放标准。     

乙醇汽油摩托车排放控制技术研究

以一款FY100-10A汽油摩托车为样机,进行排放控制技术实验研究.研究了乙醇掺烧、化油器调节、排气催化净化技术.结果表明掺烧22%的乙醇,CO排放减少8%～38%,HC减少10～30%,NOx排放在中低速时减少,在高速却有所增加.进行化油器主量孔、油针尺寸与摩托车发动机的匹配调节,得出了该摩托车最佳化油器量孔与油针的匹配参数.通过匹配排气催化净化技术,进一步降低了发动机的CO、HC和NOx的排放.综合以上净化技术的FY0100-10A摩托车排放达到了国Ⅲ标准.     

不同点火时刻下天然气掺氢缸内直喷发动机燃烧与排放特性

在缸内直喷火花点火发动机上开展了天然气掺混0％-18％氢气的混合燃料不同点火时刻下的试验研究。结果表明：对于给定的喷射时刻和喷射持续期,点火时刻对发动机性能、燃烧和排放有较大影响,喷射结束时刻与点火时刻的间隔对直喷天然气发动机极为重要,喷射结束时刻与点火时刻的间隔缩短时,混合气分层程度高,燃烧速率快,热效率高。最大放热率等燃烧特征参数随点火时刻的提前而增加。HC排放随点火时刻的提前而下降,CO2和NOx排放随点火时刻的提前而增加,NOx排放的增加在大点火提前角下更明显。掺氢可降低HC排放,对CO和CO2排放影响不大。掺氢量大于10％时可提高天然气发动机热效率。     

汽油机掺烧CO2对NOx排放影响的实验研究

本文进行EGR的基础研究,单纯从CO2的加入入手,主要以进气掺烧CO2减排汽油机NOx的特性为研究对象,在HODNA G200单缸四冲程发动机上进行系列实验.并通过理论和实验分析了进气掺烧不同流量CO2对NOx、HC、CO和CO2的排放以及燃烧过程的影响.研究结果表明,汽油机进气掺烧适量CO2减排NOx效果明显,对HC排放影响不大,CO排放略有增加,发动机输出功率有所下降.     

甲醇柴油对增压中冷柴油机燃烧与排放性能的影响

针对在增压中冷柴油机上燃用不同比例甲醇柴油对发动机燃烧和排放性能的影响进行了研究。结果表明：随着混合燃料中甲醇含量的增加,发动机动力性略有降低,使用经济性提高,缸内最大压力和温度降低,NOx和碳烟排放降低,HC排放增加;CO排放小负荷下大幅增加而在大负荷下略有降低。     

直喷式柴油机燃用二甲基醚(DME)试验研究

介绍了在1100单缸直喷式柴油机上燃用DME的发动机试验研究结果。研究表明：通过增加循环供油量可使柴油机燃用DME后恢复到原机略低，同时缸内最大爆发压力降低，发动机碳烟排放为零，HC和CO排放比原机略高，NOx排放比原柴油机降低约50%以上，供油提前角减少，缺内最大爆发压力降低，NOx排放可进一步大幅度降低，但HC排放略有升高；加大喷孔直径，缸内爆发压力升高，NOx排放升高，HC和CO排放在中低负荷相差不大，但在大负荷工况有所升高。     

直喷式轿车柴油机燃用生物柴油的排放特性

在直喷式柴油机和装有该型号柴油机的轿车上燃用柴油/生物柴油混合燃料,未对原机作任何调整,研究了不同生物柴油掺混比例的混合燃料对烟度、CO、THC、NOx和CO2排放的影响.结果表明,直喷式柴油机和轿车燃用生物柴油后,烟度大幅下降,THC排放明显减少;烟度和THC的变化均与生物柴油掺混比例呈线性关系.柴油机CO排放在小于20%负荷下,随着生物柴油的比例增高逐渐增加;在大于20%负荷时,CO排放随着混合燃料中生物柴油的比例增高而减少;在轿车上,只有低比例掺烧(10%)的CO排放有所下降.柴油机上的NOx排放在低比例掺烧(10%)时下降,而在较高比例掺烧(30%)时,NOx排放升高;在轿车上,NOx排放都有所升高.在柴油机上,燃用生物柴油混合燃料后,CO2排放的总体趋势在减少,但减少比例随生物柴油掺混比例的不同而不同;在整车上,只有低比例掺烧(10%)时CO2排放降低,而较高比例掺烧(30%)时CO2排放升高.     

沼气掺氢发动机燃烧稳定性试验

在一台单缸火花点火发动机上开展了燃用不同组分配比的沼气模拟气体的掺氢混合气的燃烧稳定性试验研究.研究结果表明:在15%～35%的掺氢比范嗣内,随着混合气中掺氢比的增加,发动机循环变动变小,燃烧稳定性提高.掺氢导致平均指示压力的循环变动系数减小,燃烧放热率加快,火焰发展期缩短.其中35%掺氢比的混合气比15%掺氢比的混合...     

氢混天然气燃气轮机加湿低氮燃烧性能研究

为了解贫预混燃烧室天然气掺氢加湿燃烧时的性能变化和容许加湿范围,解决氢混燃气轮机NO_x排放超标问题,以某燃气轮机燃烧室为研究对象,数值研究了掺氢比和加湿比对燃烧性能及污染物排放特性的影响。结果表明：燃料无加湿条件下,燃烧室出口CO和CO₂排放值随着掺氢比的增加而减小,较高燃烧温度将导致热力型NO_x排放值增加,掺氢比达到0.2以上时,NO_x排放已超出环保限值;燃料加湿条件下,随着加湿程度增加,燃气出口平均流速及水蒸气组分含量均增加,燃烧筒内全局温度、CO₂和NO_x排放值均降低,CO排放值先降低后增加;掺氢天然气加湿可实现低氮燃烧,考虑到低掺氢工况燃气轮机功率输出效能和高掺氢工况燃烧性能恶化问题,水蒸气加湿量不宜过多,当掺氢比为0.3时,推荐燃料加湿比为0.463。     

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%.     

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.     

Experimental study of the combustion of natural gas and high-hydrogen content syngases in a radiant porous media burner

The primary objective of this work is to study the blending of natural gas in equimolar proportions with three high hydrogen content syngases in a radiant porous media burner. We examined the effects of the composition of the syngases, the fuel-to-air ratio and the thermal input on the flame stability, the radiation efficiency and the pollutant emissions (CO and NOx). In this study, we emulated the syngases with H₂–CO mixtures, in which the H₂ to CO ratio was varied between 1.5 and 3. Additionally, pure natural gas was also used as a base fuel for comparison. The thermal inputs evaluated in this study correspond to two values (300 and 500 kW/m2) found in practical applications. The results indicate that the thermal input and the fuel-to-air ratio significantly influenced the temperature profile in the radiant porous media burner, the radiation efficiency, and the pollutant emissions. On the other hand, contrary to what was observed in other studies for lower hydrogen concentrations, we found that substituting natural gas with high hydrogen content syngases (up to 50%) affected the flame stability limits. Significant differences were also observed for the radiation efficiencies and pollutant emissions.     

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.     

Experimental research on a blended hydrogen-fuel engine

An experimental study on the performance of a single cylinder engine fueled with hydrogen/gas fule blends was carried out. The performance of engine with different fuel components under the load characteristics of the engine was analyzed. The experimental results showed that with the increase of hydrogen blending ratio, the combustion speed was accelerated, and the maximum torque and maximum pressure in the cylinder were increased; The maximum torque of blended fuel with 40% CO₂ was 68.3% of that without CO₂; The maximum pressure in cylinder of blended fuel with 40% H₂ was 1.6 times higher than that without hydrogen; When the proportion of hydrogen was more than 30%, the torque decreased; When the mixture was blended with 30% N₂, the engine torque reached the maximum at the hydrogen ratio of 15%; With the increase of hydrogen blending ratio, the emission of CO increased and the emission of HC and NOx decreased; When the hydrogen blending ratio remained unchanged, the CO emission was the largest at medium load, the HC emission was the largest at small load, and the NOx emission was the largest at high load; When the mixture was blended with 15% H₂, with the increase of the proportion of nitrogen, emission of CO decreased, emissions of HC and NOx increased. The research of this paper provided an experimental basis for the design and development of gas fuel engines.     

NOX emissions of compression ignition engines fueled with various biodiesel blends: A review

There are some challenges about NO_X emissions exhausted from diesel engines fueled with biodiesel. Due to increasingly stringent emission regulations, the different methods such as varying the engine operating parameters, treatment with antioxidant additive and blending fuels have been adapted to reduce emissions of biodiesel combustion. One of the effective methods is the combustion of dual or blending fuels. Various fuels such as gasoline, hydrogen, natural gas, biogas, different types of alcohols and also fuel additives have been used to reduce biodiesel disadvantages. This study reviews the potential of the different fuels as an additive in biodiesel fuel in correspond to reduce NO_X emissions. The general reduction of NO_X has been observed with the presence of gasoline, biogas and alcohols in biodiesel blends. The reduction of NO_X in biodiesel-hydrogen, biodiesel-diesel or biodiesel–CNG combustion has not been observed through all engine conditions. Moreover the retarding injection timing, the lower injection pressure, EGR higher than 30% can result in the reduced NO_X emissions. However it seems the decrease in NO_X emissions can be achieved by the use of most fuels in blending with biodiesel under all engine operating conditions, if only the proper injection parameters and blending proportions of fuels are set.     

Experimental analysis of the effects of hydrogen addition on methane combustion

This paper presents gas emissions from turbulent chemical flow inside a model combustor, for different blending ratios of hydrogen–methane composite fuels. Gas emissions such as CO and O₂ from the combustion reaction were obtained using a gas analyzer. NOx emissions were measured with a NOx analyzer. The previously obtained flame temperature distributions were also presented. As the amount of hydrogen in the mixture increases, more hydrogen is involved in the combustion reaction, and more heat is released, and the higher temperature levels are resulted. The results have shown that the combustion efficiency increases and CO emission decreases when the hydrogen content is increased in blending fuel. It is also shown that the hydrogen–methane blending fuels are efficiently used without any important modification in the natural gas burner. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulation of a hydrogen/natural gas engine and modelling of engine operating parameters

At the present work for improving the engine performance and decrease of emissions, a port injection gasoline engine is converted into direct injection. Engine performance behavior was investigated by AVL Fire software with adding hydrogen to natural gas from 0% up to 30%. Validation of the simulated model and experimental results show good confirmation. To determine the relationship between independent variables engine speed, ignition timing, injection timing and H₂% versus the dependent variables including engine performance parameters, specific fuel consumption, CO and statistical analysis models were used. Comparison between different errors models shows that Radial basis function model with training algorithm Bayesian regularization back propagation can estimate better engine performance variables. The results showed that adding hydrogen to natural gas cause the output power, torque, fuel consumption efficiency increase and specific fuel consumption drop. Also, CO decreases when ignition and injection timing be advanced and engine speed reaches to its largest.