共查询到20条相似文献,搜索用时 15 毫秒
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在考虑进气涡流比的情况下,对某490增压直喷柴油机不同喷油提前角下的缸内喷雾及燃烧过程进行了三维CFD模拟,给出了4种不同喷油提前角时的缸内火焰、NOx和Soot的时空分布.计算和分析了不同的喷油提前角下,上止点前后喷入缸内的油量比例、着火时刻、上止点温度、最高燃烧温度等对燃烧与排放物的影响.结果表明上止点前后的油量比例对排放有较大影响,对于该机型在喷油提前角较小的情况下,应考虑适当减小喷油锥角以充分利用燃烧室底部的空气.仅靠喷油提前角的变化并不能同时降低NOx和Soot的排量,并通过性能与排放试验进行了验证. 相似文献
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《International Journal of Hydrogen Energy》2019,44(21):11194-11204
In this paper, a new kind of injection mode, split hydrogen direct injection, was presented for a dual fuel SI engine. Six different first injection proportions (IP1) and five different second injection timings were applied at the condition of excess air ratio of 1, first injection timing of 300°CA BTDC, low speed, low load conditions and the Minimum spark advance for Best Torque (MBT) on a dual fuel SI engine with hydrogen direct injection (HDI) plus port fuel injection (PFI). The result showed that, split hydrogen direct injection can achieve a higher brake thermal efficiency and lower emissions compared with single HDI. In comparison with single HDI, the split hydrogen direct injection can form a controlled stratified condition of hydrogen which could make the combustion more complete and faster. By adding an early spray to form a more homogeneous mixture, the split hydrogen direct injection not only can help to form a flame kernel to make the combustion stable, but also can speed up the combustion rate through the whole combustion process, which can improve the brake thermal efficiency. By split hydrogen direct injection, the torque reaches the highest when the first injection proportion is 33%, which improves by 1.13% on average than that of single HDI. With the delay of second injection timing, the torque increases first and then decreases. With the increase of first injection proportion, the best second injection timing is advanced. Furthermore, by forming a more homogeneous mixture, the split hydrogen direct injection can reduce the quenching distance to reduce the HC emission and reduce the maximum temperature to reduce the NOX. The split hydrogen direct injection can reduce the HC emission by 35.8%, the NOX emissions by 7.3% than that of single HDI. 相似文献
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在一台YTR3105直喷式柴油机上进行了小比例甲醇-柴油混合燃料发动机的燃烧及排放特性试验研究。结果表明:在相同的平均有效压力和转速下,随着甲醇含量的增加,燃料着火延迟相应增大,使得燃烧过程向上止点后移动。混合燃料的滞燃期比柴油长,预混燃烧放热率峰值增大,燃烧持续期缩短,缸内最大爆发压力和压力升高率增加。与纯柴油相比,甲醇-柴油混合燃料HC排放有所升高,但NOx和碳烟排放降低。大负荷时,CO排放显著下降。 相似文献
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喷射参数对柴油机燃烧与排放特性的影响 总被引:2,自引:0,他引:2
在一台共轨柴油机上进行了喷射压力、喷射定时、后喷量及后/主间隔角等喷射参数影响作用的试验研究,利用FIRE软件数值模拟获取微观场变化信息,综合分析了喷射参数对缸内燃烧与有害排放物生成的影响机理及规律.结果表明,提高喷射压力和提前喷射定时有利于改善燃油经济性及碳烟排放,但在喷射压力较高(120~130,MPa),喷射定时提前到上止点前2°CA时,再提前喷射定时对碳烟的影响不大,而NOx的生成量显著增加,同时会引起燃烧粗暴.当后/主间隔角一定(15°CA),后喷量为1.5~2.0,mg时,烟度值达到最低,降幅为28%左右;后喷量为1.5,mg时,后/主间隔角在25,oCA附近,烟度达到最低,降幅达到20%.因此,引入后喷时需要选取适当的后/主间隔角和后喷油量,既要增强后喷燃油对缸内流场的扰动效果,使得更多的氧气进入主喷的燃烧产物区,加速碳烟的氧化又要避免进入高温缺氧区域内的后喷燃油量过多以及燃烧过于拖后等负面影响. 相似文献
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The objective of this paper was to study the effects of the injection pressure and injection timing on the combustion and emission characteristics in a single-cylinder common-rail direct injection (CRDI) diesel engine fueled with waste cooking oil (WCO) biodiesel and commercial diesel fuel. The fuel property including fatty acid composition for the biodiesel were measured and compared with those of the conventional diesel fuel. The engine tests were conducted at two injection pressures (80 and 160 MPa) and different injection timings from −25 to 0 crank angle degree (CAD) after top dead center (aTDC) under two different engine loads. The results showed that the indicated specific fuel consumption (ISFC) with respect to the injection timings of the biodiesel was higher than that of the diesel fuel under all experimental conditions. The peak cylinder pressure and the peak heat release rate of the biodiesel were slightly lower, while the ignition delay was slightly longer under all operating conditions. In terms of emissions, the biodiesel had benefits in reduction of smoke, carbon monoxide (CO), hydrocarbon (HC) emissions especially with high fuel injection pressure. The nitrogen oxide (NOx) emissions of the biodiesel were relatively higher than those of the diesel under all experimental conditions. 相似文献
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Combustion studies on both diesel fuel and vegetable oil fuels, with the standard and advanced injection timing, were carried out using the same engine and test procedures so that comparative assessments may be made. The diesel engine principle demands self-ignition of the fuel as it is injected at some degrees before top dead centre (BTDC) into the hot compressed cylinder gas. Longer delays between injection and ignition lead to unacceptable rates of pressure rise with the result of diesel knock because too much fuel is ready to take part in premixed combustion. Alternative fuels have been noted to exhibit longer delay periods and slower burning rate especially at low load operating conditions hence resulting in late combustion in the expansion stroke. Advanced injection timing is expected to compensate these effects. The engine has standard injection timing of 30°C BTDC. The injection was first advanced by 5.5°C given injection timing of 35.5°C BTDC. The engine performance was very erratic on this timing. The injection was then advanced by 3.5°C and the effects are presented in this paper. The engine performance was smooth especially at low load levels. The ignition delay was reduced through advanced injection but tended to incur a slight increase in fuel consumption. Moderate advanced injection timing is recommended for low speed operations. 相似文献
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《International Journal of Hydrogen Energy》2021,46(56):28789-28800
Fuel opening injection pressure and injection timing are important injection parameters, and they have a significant influence on engine combustion, performance, and emissions. The focus of this work is to improve the performance and emissions of single-cylinder diesel engines by using injection parameters in engines running with rice bran biodiesel 10% blend (RB10+H₂) and 20% blend (RB20+H₂) with a fixed hydrogen flow rate of 7 lpm. In addition, hydrogen and biodiesel are excellent alternatives to conventional fuels, which can reduce energy consumption and strict emission standards. The investigation is conducted for three different opening injection pressure of 220, 240, 260 bar, and four different injection timings of 20°, 22°, 24°, and 26° bTDC. Results indicate that the sample ‘RB10+H₂’ provides 3.32% higher BTE and reduces the fuel consumption by 13% as diesel fuel. The blend RB10+H₂ attributes a maximum cylinder pressure of 68.7 bar and a peak HRR value of 49 J/ºCA. Further, compared to diesel, RB10+H₂ blend emits lower CO, HC, and smoke opacity by 17%, 22%, and 16%, respectively. However, an almost 12% increase of nitrogen oxides for the RB10+H₂ blend is observed. However, with advanced injection timing and higher opening injection pressure, NOx emissions is slightly increased. 相似文献
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Ethanol has been considered as an alternative fuel for diesel engines. On the other hand, injection timing is a major parameter that sensitively affects the engine performance and emissions. Therefore, in this study, the influence of advanced injection timing on the engine performance and exhaust emissions of a single cylinder, naturally aspirated, four stroke, direct injection diesel engine has been experimentally investigated when using ethanol‐blended diesel fuel from 0 to 15% with an increment of 5%. The original injection timing of the engine is 27° crank angle (CA) before top dead center (BTDC). The tests were conducted at three different injection timings (27, 30 and 33° CA BTDC) for 30 Nm constant load at 1800 rpm. The experimental results showed that brake‐specific energy consumption (BSEC), brake‐specific fuel consumption (BSFC), NOx and CO2 emissions increased as brake‐thermal efficiency (BTE), smoke, CO and HC emissions decreased with increasing amount of ethanol in the fuel mixture. Comparing the results with those of original injection timing, NOx emissions increased and smoke, HC and CO emissions decreased for all test fuels at the advanced injection timings. For BSEC, BSFC and BTE, advanced injection timings gave negative results for all test conditions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Stringent emission norms and rapid depletion of petroleum resources have resulted in a continuous effort to search for alternative fuels. Hydrogen is one of the best alternatives for conventional fuels. Hydrogen has both the benefits and limitation to be used as a fuel in an automotive engine system. In the present investigation, hydrogen was injected into the intake manifold by using a hydrogen gas injector and diesel was introduced in the conventional, mode which also acts as an ignition source for hydrogen combustion. The flow rate of hydrogen was set at 5.5 l min?1 at all the load conditions. The injection timing was kept constant at top dead center (TDC) and injection duration was adjusted to find the optimized injection condition. Experiments were conducted on a single cylinder, four stroke, water‐cooled, direct injection diesel engine coupled to an electrical generator. At 75% load the maximum brake thermal efficiency for hydrogen operation at injection timing of TDC and with injection duration of 30°CA is 25.66% compared with 21.59% for diesel. The oxides of nitrogen (NOX) emission are 21.7 g kWh?1 for hydrogen compared with diesel of 17.9 g k Wh?1. Smoke emissions reduced to 1 Bosch smoke number (BSN) in hydrogen compared with diesel of 2.2 BSN. Hydrogen operation in the dual fuel mode with diesel exhibits a better performance and reduction in emissions compared with diesel in the entire load spectra. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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O.M.I. Nwafor 《Renewable Energy》2007,32(14):2361-2368
There has been a growing concern on the emission of greenhouse gases into the atmosphere, whose consequence is global warming. The sources of greenhouse gases have been identified, of which the major contributor is the combustion of fossil fuel. Researchers have intensified efforts towards identifying greener alternative fuel substitutes for the present fossil fuel. Natural gas is now being investigated as potential alternative fuel for diesel engines. Natural gas appears more attractive due to its high octane number and perhaps, due to its environmental friendly nature. The test results showed that alternative fuels exhibit longer ignition delay, with slow burning rates. Longer delays will lead to unacceptable rates of pressure rise with the result of diesel knock. This work examines the effect of advanced injection timing on the emission characteristics of dual-fuel engine. The engine has standard injection timing of 30° BTDC. The injection was first advanced by 5.5° and given injection timing of 35.5° BTDC. The engine performance was erratic on this timing. The injection was then advanced by 3.5°. The engine performance was smooth on this timing especially at low loading conditions. The ignition delay was reduced through advanced injection timing but tended to incur a slight increase in fuel consumption. The CO and CO2 emissions were reduced through advanced injection timing. 相似文献
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《International Journal of Hydrogen Energy》2022,47(75):32330-32344
Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy. 相似文献
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从形成均匀预混合气及着火后具有良好化学反应动力学效应的角度出发,在单缸135直喷式柴油机上采用双收口型燃烧室、P型喷油泵、预喷射、伞喷油嘴、乳化柴油及乙醇柴油等方法,对实现均质充量压缩着火(homogeneous charge compression ignition,HCCI)燃烧的多种途径进行了对比试验。结果表明:应用伞喷油嘴有效促进了着火前缸内均质预混合气的形成,具有进一步在小排量增压中冷、高压电喷柴油机上推广的潜力;通过燃料设计可控制着火在上止点附近并提高燃烧速率,有利于实现高效、低排放的近似等压预混合燃烧方式。 相似文献
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非直喷式柴油机气态污染物形成历程研究 总被引:5,自引:2,他引:3
本文应用新研制的全气缸取样系统测量了一台S195型涡流室式柴油机气缸内NO_x、CO浓度随曲轴转角的变化历程。考查了负荷、转速和喷油提前角对NO_x、CO浓度变化历程的影响。实验结果同计算机模拟结果作了对比,两者基本吻合。 相似文献
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This paper investigated the impact of injection angle and advance injection timing on combustion, emission, and performance characteristics in a dimethyl ether (DME) fueled compression ignition engine through experimentation on spray behaviors and the use of numerical methods. To achieve this aim, a visualization system and two injectors with different injection angles were used to analyze spray characteristics. The combustion, emission, and performance characteristics were analyzed by numerical methods using a detailed chemical kinetic DME oxidation model. Each of five injection angles and timings were selected to examine the effect of injection angle and timing. It was revealed that the injected spray with narrow injection angles was impinged on the bottom wall after the SOI of BTDC 60°, and most of the fuel spray and evaporation with the wide injection angles had a distribution at the crevice region when the injection timing was advanced. In addition, NOx emissions at the SOI of BTDC 20° and TDC had higher values, and the soot emission quantities were extremely small. The narrow injection angles had good performance at the advanced injection timing, and the injection timing over a range of BTDC 40-20° showed superiority in performance characteristics. 相似文献