气体燃料燃烧特性分析计算与软件开发及应用

气体燃料是发动机的燃料之一,燃料种类繁多、组分不同,没有统一标准.用于燃气机必定对燃气机各项经济技术指标、结构设计有不同的要求,如何对各种气体燃料燃烧特性进行分析及评价,是燃气机设计首先要解决的问题.本文对各种气体燃料的燃烧特性进行了分析、计算,并开发了计算机分析计算软件,作为燃气机设计时参考.     

气体发动机燃料特性参数计算软件开发及应用

不同气体燃料物理、化学性质不同,直接关系到气体发动机的结构设计及各项性能指标;对各种气体燃料特性进行分析及评价是气体发动机设计首先要解决的问题。开发了气体燃料特性参数计算软件,对各种气体燃料的物理、化学特性进行了分析、计算,并就这些参数对气体机性能的影响进行了分析,供气体发动机设计做参考。     

气体燃料及燃气机的技术研究与应用

介绍了各种典型气体燃料特性及燃气机的特点和主要机型,对燃气机的应用进行了探讨。指出由于气体燃料不同,其性质也不同,燃用不同气体燃料的燃气机在结构和性能上差异也较大,不同的气体燃料决定了燃气的甲烷值、混合气热值、空燃比等气体特性,也决定了燃气机进气方式、压缩比、点火时间、控制方式等结构形式和性能参数等指标。     

燃气特性对发动机性能参数的影响

燃气发动机使用天然气、瓦斯、焦炉煤气等燃料,其动力性、经济性、可靠性很大程度取决于所用气体燃料的成分及特性。各种燃气成分的差异,导致混合气低热值、甲烷值、沃泊指数和燃烧势不同,从而影响燃气发动机的工作过程,导致输出功率、爆震、压缩比、燃烧速度以及点火正时的差异。本文介绍了常见可燃气体的组成成分,分析可燃气体的特性及对发动机性能参数的影响,并为气体发动机的工程运用提供依据。     

燃气-蒸汽联合循环的低热值燃料热经济性分析

由于低热值气体燃料中含有大量惰性气体,可燃成分少,发热量低,燃料的体积流量大,因而在燃用低热值气体燃料时,燃气-蒸汽联合循环的特性也发生了变化.分析了压缩比、燃气初温、不同燃料成分对联合循环发电装置热效率的影响;阐述了不同燃料成分时压缩燃料耗功的变化,以及对燃气-蒸汽联合循环装置热效率的影响.对比分析了燃气-蒸汽联合循环与蒸汽循环装置的经济性.     

低氮燃气燃烧技术及燃烧器设计进展

NO_x是目前燃气燃烧的主要污染物。设计和开发新型低NO_x燃气燃烧器是当前燃气燃烧污染物减排改造的关键。但是,目前我国低NO_x燃烧器的设计开发尚未形成一套完整的理论体系和技术路线。详细介绍了气体燃料燃烧的特点,简述了各种气体燃料燃烧过程中NO_x的生成机理和控制因素,分析了不同运行工况对燃气燃烧器火焰中NO_x生成的影响,总结了目前燃气燃烧器设计中运用到的主要技术手段和实施方法;讨论了计算机仿真技术用于低NO_x燃烧器设计的研究进展。分析表明,燃气燃烧过程中NO_x的生成机理已经较为清晰,但目前燃烧器设计过程中控制NO_x生成的技术手段有限,缺少精准的设计方法和经济可靠的验证方案。未来,计算机仿真技术(CFD)将成为燃烧器设计的重要工具,并将大幅降低实验成本,缩短开发时间。     

中低热值燃料对燃气轮机运行特性的影响分析

中低热值燃料燃气轮机对经济发展和节能减排具有重要的意义,对其燃烧特性和运行工况的研究是本项技术的关键问题。本文根据燃气轮机压气机特性曲线、涡轮特性曲线和热力循环过程,分析计算中低热值燃料燃气的热力性质,提出了适用于不同组分的中低热值燃料的膨胀做功计算方法。通过对燃用天然气和合成气进行模拟计算,得到燃料热值对燃料系数、涡轮出口温度、燃料流量及膨胀功的影响规律,为燃气轮机的设计和工况调整提供理论依据。     

Stirling 发动机燃烧及换热分析

基于碳氢燃料燃烧化学平衡反应计算,得到燃烧产物温度及组分成份,在此基础上计算燃气物性,从而计算了热气机外燃系统加热管的对流换热系数、辐射换热系数及后排换热管的肋片换热,对燃用空气和液氧两种燃烧情形进行了对比计算,并计算了各种因素对燃烧的影响,对计算结果进行了分析和讨论,得到了很有价值的结论,为热气机外燃系统结构设计提供了借鉴。     

生物质气微型燃气轮机燃烧室污染物生成特性的实验研究

在为中低热值气体燃料设计的低排放微型燃气轮机燃烧室单头部实验件上进行了燃烧污染物生成特性实验,对比分析不同热值气体燃料、不同喷射孔位置和射流深度以及不同值班级与主燃级燃料分配比例时的污染物排放特性。结果表明:燃烧室在50%～100%负荷范围内表现出较好的燃料适应性,NO_x排放质量浓度最高达到76.9 mg/m~3,满足环保要求;喷嘴位置、混合距离、主燃级燃料压力会影响燃料与空气的混合均匀性,进而影响污染物的生成;燃料分配比例会影响燃烧室温度分布的均匀性,随着值班级燃烧区燃料占比的降低,污染物排放量降低。     

新型燃气低氮燃烧机设计理念及结构研究

与燃煤燃烧主要以燃料型NOx不同的是,燃气燃烧产生的氮氧化物主要为热力型NOx,因此燃气低氮燃烧技术与燃煤有很大不同。热力型NOx的关键控制参数是炉膛温度,故合理优化燃料与助燃空气的混合过程,使得炉膛温度更加均匀,避免局部高温的出现是燃气低氮燃烧的关键技术。另外,要求燃烧机除了有比较好的低氮特性以外,还要有极强的燃料适应性和负荷适应性。目前现有的燃气燃烧机在燃烧其设计燃料的情况下,燃烧效率和污染物排放都很不错,但如果燃料有一定的偏差,其稳燃特性不好,燃烧效率和污染物排放性能都急剧恶化。因此,一个好的超低氮燃烧机除了可以在燃烧设计燃料时达到非常好的燃烧效率和污染物排放标准,同时还应对燃料的变动具有比较宽的适应性,依然具有好的稳燃特性。     

Effect of engine parameters and type of gaseous fuel on the performance of dual-fuel gas diesel engines—A critical review

Petroleum resources are finite and, therefore, search for their alternative non-petroleum fuels for internal combustion engines is continuing all over the world. Moreover gases emitted by petroleum fuel driven vehicles have an adverse effect on the environment and human health. There is universal acceptance of the need to reduce such emissions. Towards this, scientists have proposed various solutions for diesel engines, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines, which use conventional diesel fuel and gaseous fuel, are referred to as ‘dual-fuel engines’. Natural gas and bio-derived gas appear more attractive alternative fuels for dual-fuel engines in view of their friendly environmental nature. In the gas-fumigated dual-fuel engine, the primary fuel is mixed outside the cylinder before it is inducted into the cylinder. A pilot quantity of liquid fuel is injected towards the end of the compression stroke to initiate combustion. When considering a gaseous fuel for use in existing diesel engines, a number of issues which include, the effects of engine operating and design parameters, and type of gaseous fuel, on the performance of the dual-fuel engines, are important. This paper reviews the research on above issues carried out by various scientists in different diesel engines. This paper touches upon performance, combustion and emission characteristics of dual-fuel engines which use natural gas, biogas, producer gas, methane, liquefied petroleum gas, propane, etc. as gaseous fuel. It reveals that ‘dual-fuel concept’ is a promising technique for controlling both NO_x and soot emissions even on existing diesel engine. But, HC, CO emissions and ‘bsfc’ are higher for part load gas diesel engine operations. Thermal efficiency of dual-fuel engines improve either with increased engine speed, or with advanced injection timings, or with increased amount of pilot fuel. The ignition characteristics of the gaseous fuels need more research for a long-term use in a dual-fuel engine. It is found that, the selection of engine operating and design parameters play a vital role in minimizing the performance divergences between an existing diesel engine and a ‘gas diesel engine’.     

Comparative energies of alternative fuels

In order to provide additional design data on candidate alternative fuels, a broad comparison is made of the net calorific values of a wide variety of gaseous, liquid and solid fuels, including a number of alternatives of current interest, against a background of conventional fuels, some of which may have alternative applications.In general, higher gravimetric calorific values are shown by the lighter of the gaseous and liquid fuels and the heavier of the solid fuels. Volumetric calorific values rise with fuel density, with the exception of the fuel gases. Despite a wide overall range in calorific values, the gravimetric energy content of a stoichiometric fuel-air mixture is seen to be virtually independent of fuel type. In such applications as the spark-ignition piston engine and the rocket, additional combustion parameters arise which tend to overshadow calorific value and are therefore adopted for performance assessment.     

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.     

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.     

逼近最佳空燃比

空燃比是影响气体燃料发动机的一个重要参数,当发动机燃用不同的气体燃料时最佳空燃比是不同的。考虑到各种气体燃料品质的不同,本文讨论了逼近最佳空燃比的方法和步骤以及空燃比对混合器结构的影响,并同试验结果进行了比较。     

Particulate emissions from laser ignited and spark ignited hydrogen fueled engines

Exponentially increasing energy demand and stricter emission legislations have motivated researchers to explore alternative fuels and advanced engine technologies, which are more efficient and environment friendly. In last two decades, hydrogen has emerged as promising alternative fuel for internal combustion (IC) engines and vehicles. For gaseous fuels, laser ignition (LI) has emerged as a novel ignition technique due to its superior characteristics, leading to improved combustion, engine performance and emission characteristics. Numerous advantages of LI system such as flexibility of plasma location, lower NO_x emissions and capability of igniting ultra-lean fuel–air mixture makes LI system superior compared to conventional spark ignition (SI) system. This study experimentally compares particulate emissions from hydrogen fueled engine ignited by LI and SI systems. Experiments were performed in a constant speed engine prototype, which was suitably modified to operate on gaseous fuels using both LI as well as SI systems. Particulate were characterized using engine exhaust particle sizer (EEPS) spectrometer. Results showed that LI engine resulted in relatively higher particulate number concentration as well as particulate mass compared to SI engine. In both ignition systems, particulate emissions increased with increasing engine load however rate of increase was relatively higher in LI system. Relatively larger count mean diameter (CMD) of particulate emitted from SI engine compared to LI engine was another important observation. This showed emission of relatively smaller particles in larger numbers from LI engine, compared to baseline SI engine.     

Analysis of ignition delay period of a dual fuel diesel engine with hydrogen and LPG as secondary fuels

In this study, experiments were performed on 4 cylinder turbocharged, intercooled with 62.5 kW gen-set diesel engine by using hydrogen, liquefied petroleum gas (LPG) and mixture of LPG and hydrogen as secondary fuels. The experiments were performed to measure ignition delay period at different load conditions and various diesel substitutions. The experimental results have been compared with ignition delay correlation laid down by other researchers for diesel and dual fuel diesel engine. It is found that ignition delay equation based on pressure, temperature and oxygen concentration for a dual fuel diesel engine run on diesel-biogas gives variation up to 6.56% and 14.6% from the present experimental results, while ignition delay equation for a pure diesel engine gives 7.55% and 33.3% variation at lower and higher gaseous fuel concentrations, respectively. It is observed that the ignition delay of dual fuel engine depends not only on the type of gaseous fuels and their concentrations but also on charge temperature, pressure and oxygen concentration.     

Experimental investigation concerning the effect of natural gas percentage on performance and emissions of a DI dual fuel diesel engine

During the last years a great effort has been made to reduce pollutant emissions from direct injection (DI) diesel engines. Towards this, engineers have proposed various solutions, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines, which use conventional diesel fuel and gaseous fuel, are referred to as dual fuel engines. The main aspiration from the usage of dual fuel (liquid and gaseous one) combustion systems is mainly to reduce particulate emissions and nitrogen oxides.One of the gaseous fuels used is natural gas, which has a relatively high auto ignition temperature and moreover is an economical and clean burning fuel. The high auto ignition temperature of natural gas is a serious advantage against other gaseous fuels since the compression ratio of most conventional DI diesel engines can be maintained. Moreover the combustion of natural gas produces practically no particulates since natural gas contains less dissolved impurities (e.g. sulfur compounds).The present contribution is mainly concerned, with an experimental investigation of the characteristics of dual fuel operation when liquid diesel is partially replaced with natural gas under ambient intake temperature in a DI diesel engine. Results are given revealing the effect of liquid fuel percentage replacement by natural gas on engine performance and emissions.     

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.     

The autoignition in air of some binary fuel mixtures containing hydrogen

A predictive model for the autoignition and combustion of fuel–air mixtures employing detailed full chemical schemes was used to examine the autoignition and combustion characteristics in air of hydrogen in the presence of a range of common fuels. These included the gaseous fuels: methane, carbon monoxide and the higher hydrocarbon fuel n-heptane. A wide range of relative concentrations of the fuel components in the binary mixtures with hydrogen for different values of initial mixture temperature and pressure were considered under constant volume adiabatic conditions. It is shown that the presence of hydrogen in turn with these fuels can bring about complex changes to the autoignition behaviour of the fuel mixtures that show hydrogen may behave as an accelerant or retardant depending on the fuel, initial temperature, pressure and equivalence ratio considered.