Emissions reductions using hydrogen from plasmatron fuel converters

Improvements in internal combustion engine and aftertreatment technologies are needed to meet future environmental quality goals. Systems using recently developed compact plasmatron fuel converters in conjunction with state-of-the-art engines and aftertreatment catalysts could provide new opportunities for obtaining substantial emissions reductions. Plasmatron fuel converters provide a rapid response, compact means to transform a wide range of hydrocarbon fuels (including gasoline, natural gas and diesel fuel) into hydrogen-rich gas. Hydrogen-rich gas can be used as an additive to provide NO_x reductions of more than 80% in spark ignition gasoline engine vehicles by enabling very lean operation or heavy exhaust engine recirculation. It may also be employed for cold start hydrocarbon reduction. If certain requirements are met, it may also be possible to achieve higher spark ignition engine efficiencies (e.g., up to 95% of those of diesel engines). These requirements include the attainment of ultra lean, high compression ratio, open throttle operation using only a modest amount of hydrogen addition. For diesel engines, use of compact plasmatron reformers to produce hydrogen-rich gas for the regeneration of NO_x absorber/adsorbers and particulate traps for diesel engine exhaust aftertreatment could provide significant advantages. Recent tests of conversion of diesel fuel to hydrogen-rich gas using a low current plasmatron fuel converter with non-equilibrium plasma features are described.     

Investigating the effects of LPG on spark ignition engine combustion and performance

A quasi-dimensional spark ignition (SI) engine cycle model is used to predict the cycle, performance and exhaust emissions of an automotive engine for the cases of using gasoline and LPG. Governing equations of the mathematical model mainly consist of first order ordinary differential equations derived for cylinder pressure and temperature. Combustion is simulated as a turbulent flame propagation process and during this process, two different thermodynamic regions consisting of unburned gases and burned gases that are separated by the flame front are considered. A computer code for the cycle model has been prepared to perform numerical calculations over a range of engine speeds and fuel–air equivalence ratios. In the computations performed at different engine speeds, the same fuel–air equivalence ratios are selected for each fuel to make realistic comparisons from the fuel economy and fuel consumption points of view. Comparisons show that if LPG fueled SI engines are operated at the same conditions with those of gasoline fueled SI engines, significant improvements in exhaust emissions can be achieved. However, variations in various engine performance parameters and the effects on the engine structural elements are not promising.     

Experimental study of combustion performances and emissions of a spark ignition cogeneration engine operating in lean conditions using different fuels

This work presents an experimental study describing a six-cylinder spark ignition engine running with a lean equivalence ratio, high compression ratio, ignition delay and used in a cogeneration system (heat and electricity production). Three types of fuels; natural gas, pure methane and methane/hydrogen blend (85% CH₄ and 15% H₂ by volume), were used for comparison purposes. Each fuel has been investigated at 1500 rpm and for various engine loads fixed by electrical power output conditions. CO, CO₂, HC, and NOx emissions values, and exhaust gas temperature were measured. The effect of fuel composition on engine characteristics has been studied. The results show, that the hydrogen addition increased HC emissions (around 18%), as well as performance, whilst it reduced NO_x (around 31%), exhaust gas temperature, CO and CO₂.     

稀燃天然气发动机燃烧循环变动影响因素研究

通过对一台点燃式多点电喷稀燃天然气发动机进行试验,获得了不同工况下的平均指示压力循环变动系数,以此为基础研究了燃空当量比、节气门开度、转速及点火时刻对稀燃天然气发动机燃烧循环变动的影响趋势。结果表明:混合气燃空当量比越小,燃烧循环变动越明显,当燃空当量比降低到一定值时,平均指示压力循环变动系数的增长会突然加大;节气门开度越小燃烧循环变动越明显,节气门开度小于30%后,其对燃烧循环变动影响更加明显;燃烧循环变动量随转速上升有增加的趋势,在高转速工况下燃烧循环变动的加强尤其明显;在工况一定的条件下存在一个最优的点火时刻可使稀燃天然气发动机的燃烧循环变动最小。     

Comparison between direct and indirect (prechamber) spark ignition in the case of a cogeneration natural gas engine,part I: engine geometrical parameters

The operation of a cogeneration internal combustion engine with unscavenged prechamber ignition was investigated. The objective was to evaluate the potential to reduce the exhaust gas emissions, particularly the CO emissions without exhaust gas after treatment. The investigation was carried out on a small size gas engine (150 kW) and required the development of cooled prechambers and the modification of the engine cylinder heads. The limit of the conventional lean burn operating mode with direct ignition is discussed and the prechamber geometrical configuration is presented. Through the generation of gas jets in the main chamber, the use of a prechamber strongly intensifies and accelerates the combustion process. The prechamber operation reduces significantly the emissions of CO and total hydrocarbon (THC) for same NO_x emissions. The use of a piston generating significantly more turbulence leads to a somewhat higher fuel conversion efficiency without affecting significantly the CO and THC emissions at low NO_x emissions. Further improvement associated with the adjustment of the engine operating parameters and the turbocharger characteristics, as well as a comparison between direct and prechamber ignition operation are presented in the second part (II) of this publication.     

LPG/柴油混合燃料发动机性能与排放的研究

研究了直喷柴油机燃用不同掺混比的LPG／柴油混合燃料时的动力性、经济性及排放特性。结果表明，掺入一定比例的LPG可以改善缸内燃烧过程，随着掺混比的增大，碳烟和NOx的排放大幅度降低，CO和HC的排放略有升高，动力性和经济性基本维持不变。     

增压稀燃天然气掺氢发动机排放特性

为了研究20%掺氢比的增压稀燃天然气掺氢(HCNG)发动机的排放特性,通过对发动机进行了空燃比和点火提前角调整试验、ETC循环测试试验和加装氧化型催化器试验,获得了20%HCNG发动机的排放规律.CH4排放随着空燃比的增大先减少后增加;CO排放在高于理论空燃比后骤减;Nox排放随着空燃比的增大先增加后减少,在空燃比19～21 左右达到最大值,1600～1800r/min时最低.CO、Nox随着点火提前角的增大而增加;CH4随着点火提前角的增大略有增加,并且点火提前角越大,对CH4排放的影响越小.加装催化器后,CO、CH4的转化效率均＞90%.试验结果表明:增压稀燃和氧化型催化器相结合是天然气掺氢发动机节能减排的有效方案.     

A review of hydrogen usage in internal combustion engines (gasoline-Lpg-diesel) from combustion performance aspect

Demand for fossil fuels is increasing day by day with the increase in industrialization and energy demand in the world. For this reason, many countries are looking for alternative energy sources against this increasing energy demand. Hydrogen is an alternative fuel with high efficiency and superior properties. The development of hydrogen-powered vehicles in the transport sector is expected to reduce fuel consumption and air pollution from exhaust emissions. In this study, the use of hydrogen as a fuel in vehicles and the current experimental studies in the literature are examined and the results of using hydrogen as an additional fuel are investigated. The effects of hydrogen usage on engine performance and exhaust emissions as an additional fuel to internal combustion gasoline, diesel and LPG engines are explained. Depending on the amount of hydrogen added to the fuel system, the engine power and torque are increased at most on petrol engines, while they are decreased on LPG and diesel engines. In terms of chemical products, the emissions of harmful exhaust gases in gasoline and LPG engines are reduced, while some diesel engines increase nitrogen oxide levels. In addition, it is understood that there will be a positive effect on the environment, due to hydrogen usage in all engine types.     

直喷式LPG/柴油混合燃料压燃发动机的研究

基于液态LPG／柴油混合燃料在油泵前按一定比例混合和缸内直喷压燃的构想,开发了液态LPG／柴油比例混合电子控制系统。对该控制系统进行的一系列性能测试结果表明,它能根据发动机不同工况的需要,任意调节液态LPG／柴油的混合比,且调整精度较高。应用该系统,进行了直喷式LPC／柴油混合燃料压燃发动机的性能试验。试验结果表明：直喷式LPG／柴油混合燃料压燃发动机具有与柴油机相同的动力性与燃料经济性,而其烟度、NOx和HC排放均优于原柴油机。     

甲醇-汽油混合燃料电喷汽油机性能的试验研究

在一台多点电喷汽油机上,系统开展了燃用高比例的甲醇汽油混合燃料(甲醇的体积比为85%)M85时发动机的动力性,经济性和排放特性。研究结果表明:电喷汽油机燃用M85时,动力性明显改善,经济性明显提高,有效热效率明显提高;CO和NOx的排放有明显改善,但HC排放明显恶化。     

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.     

液化石油气与汽油燃烧特性的对比试验研究

在点燃式发动机上分别燃用液化石油气和汽油,通过采集示功图并进行放热规律计算,对两种燃料在相似工况、相同过量空气系数下的燃烧特性进行对比分析。结果表明,在不改变样机结构和点火提前角的情况下,燃用液化石油气造成样机最大输出功率下降了7.64%。标定工况下,过量空气系数的变化对样机燃用汽油时的功率影响较大。两种燃料标定工况下的比热耗均随过量空气系数的增大而降低,但液化石油气降低的幅度较小。相似工况、相同过量空气系数下,相对于汽油,液化石油气的滞燃期短,燃烧持续期短,燃烧速度快。     

Evaluation of acetylene as a spark ignition engine fuel

In spite of its known shortcomings as a fuel for spark ignition engines, acetylene has been suggested as a possible alternative to petroleum-based fuels since it can be produced from non-petroleum resources (coal, limestone and water). Therefore, acetylene was evaluated in a single-cylinder engine to investigate performance and emission characteristics with special emphasis on lean operation for NO_x control. Testing was carried out at constant speed, constant airflow and MBT spark timing. Equivalence ratio and compression ratio were the primary variables. The engine operated much leaner when fuelled with acetylene than with gasoline. With acetylene, the engine operated at equivalence ratios as lean as 0·53 and 0·43 for compression ratios of 4 and 6, respectively. However, the operating range was very limited. Knock-induced preignition occurred either with compression ratios above 6 or with mixtures richer than 0·69 equivalence ratio. Both the indicated thermal efficiency and power output were less for acetylene fuelling than for gasoline. Acetylene combustion occurred at sufficiently lean equivalence ratios to produce very low NO_x and CO emissions. However, when the low NO_x levels were achieved hydrocarbon control was not improved over that with gasoline. Despite the potential for NO_x control demonstrated in this study of acetylene fuelling, difficulties encountered with engine knock and preignition plus well-known safety problems (wide flammability limits and explosive decomposition) associated with acetylene render this fuel impractical for spark ignition engines.     

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.     

Experimental studies on homogeneous charge CI engine fueled with LPG using DEE as an ignition enhancer

Producing and using renewable fuels for transportation is one approach for sustainable energy future for the world. A renewable fuel contributes lesser global climate change. The present work reports on the utilization of liquified petroleum gas (LPG) as a primary fuel with diethyl ether (DEE) as an ignition enhancer in a direct injection diesel engine. LPG has a simpler hydrocarbon structure than conventional fuels. DEE is recently reported as a renewable fuel and to be a low-emission high-quality diesel fuel replacement. A single cylinder, four-stroke, water-cooled naturally aspirated DI diesel engine having rated output of 3.7 kW at 1500 rpm was used for the experiments. Measurements were made to study the performance, combustion and emissions characteristics. From the results, it is observed that, the brake thermal efficiency lower by about 23% at full load with a reduction of about 65% NO emission than the diesel operation. The maximum reduction in smoke and particulate emissions is observed to be about 85% and 89%, respectively, when compared to that of diesel operation, however an increase in CO and HC emissions was observed.     

Comparison between direct and indirect (prechamber) spark ignition in the case of a cogeneration natural gas engine,: part II: engine operating parameters and turbocharger characteristics

In the first paper (part I), prechamber ignition in cogeneration natural gas engines has been shown to significantly intensify and accelerate the combustion process, offering a further potential to reduce the exhaust gas emissions while keeping efficiency at a high level. This second part discusses the influence of the engine operating parameters (spark timing and load) and the turbocharger characteristics with the objective of evaluating the potential to reduce the exhaust gas emissions, particularly the CO emissions, below the Swiss limits (NO_X and CO emissions: 250 and 650 mg/m_N³, 5% O₂, respectively), without exhaust gas after treatment. The advantage of using an unscavenged prechamber is conditioned by a significant delay of the spark timing in order to generate substantial gas jets. This results in a large decrease in peak cylinder pressure and in an important reduction of NO_X, CO and THC emissions. Minimum emissions are achieved at a spark timing of about 8° CA_BTDC. In comparison with the direct ignition, the prechamber ignition yields approximately 40% and 55% less CO and THC emissions, respectively. However, this also leads to about 2%-point lower fuel conversion efficiency. The optimisation of the turbocharger results in a recovery of about 1%-point in fuel conversion efficiency, but a consequent change in the exhaust manifold gas dynamics attenuates the reduction in THC emissions. At the rated power output (150 kW), the prechamber ignition operation fulfils the Swiss requirements for exhaust gas emissions and still achieves a fuel conversion efficiency higher than 36.5%.     

Analysis of performance parameters of an ethanol fueled spark ignition engine operating with hydrogen enrichment

Concerns with the environment and energy security have increased interest in phasing out fossil fuels in the automotive industry, as it transitions from conventional internal combustion engines (ICE) to electric and fuel cell powertrains. During this transition, ethanol is of particular interest as a renewable fuel option in ICE, despite drawbacks compared to gasoline. Adding hydrogen to ethanol could remedy the disadvantages associated with ethanol, while maintaining the benefits of using renewable fuels. There is a gap in the literature of both experimental and numerical studies considering hydrogen addition in turbocharged ethanol engines. Therefore, this paper presents an experimental and numerical study of a turbocharged ethanol engine operating with hydrogen enrichment at stoichiometric conditions under boosted conditions. It was concluded that hydrogen addition allowed spark ignition engines to achieve lower brake specific energy consumption, better performance, and lower emissions. Thus, after proper calibration, a simulation model was created and shown to be a suitable tool to predict engine performance of a spark ignition engine operating with hydrogen enrichment and reduce the overall number of experimental tests needed to tune engines operating with this fuel blend. Finally, some operating strategies are recommended based on these findings.     

Experimental investigation of the performance and exhaust emissions of a swirl chamber diesel engine using JP-8 aviation fuel

An experimental study is conducted to evaluate the use of JP-8 aviation fuel as a full substitute for diesel fuel in a Ricardo E-6 high-speed naturally-aspirated four-stroke experimental engine having a swirl combustion chamber. The study covers a wide range of engine load and speed operating conditions, comprising measurements of cylinder pressure diagrams, high-pressure fuel pipe pressures, exhaust gas temperatures, fuel consumptions, exhaust smokiness and exhaust gas emissions (nitrogen oxides, unburned hydrocarbons and carbon monoxide). Processing of the measurements provides important performance parameters such as maximum combustion pressure, dynamic injection timing, ignition delay, combustion irregularity and knocking tendency. The differences in the measured performance and exhaust emission parameters are determined for engine operation with JP-8 fuel, against baseline engine operation using diesel fuel. The study shows that the exhaust emission levels are not much different for operation with the two fuels. On the contrary, operation with JP-8 fuel increases combustion pressures, combustion intensity and irregularity. This is caused mainly by high pressure fluctuations present in the fuel injection system due to the different physical properties of JP-8 fuel (compared to diesel fuel), which totally change the injection characteristics. Retardation of the static injection timing is one means of improving this situation, while using the same fuel injection equipment. © 1997 John Wiley & Sons, Ltd.