Combustion characteristics of SI engine fueled with methanol-gasoline blends during cold start

A 3-cylinder port fuel injection (PFI) engine fueled with methanol-gasoline blends was used to study combustion and emission characteristics. Cylinder pressure analysis indicates that engine combustion is improved when methanol is added to gasoline. With the increase of methanol, the flame developing period and the rapid combustion period are shortened, and the indicated mean effective pressure increases during the first 50 cycles. Meanwhile, a novel quasi-instantaneous sampling system was designed to measure engine emissions during cold start and warm-up. The results at 5°C show that unburned hydrocarbon (UHC) and carbon monoxide (CO) decrease remarkably. Hydrocarbon (HC) reduces by 40% and CO by 70% when fueled with M30 (30% methanol in volume). The exhaust gas temperature is about 140°C higher at 200 s after operation compared with that of gasoline. __________ Translated from Transactions of CSICE, 2007, 25(3): 235–240 [译自: 内燃机学报]     

Study of spark ignition engine fueled with methanol/gasoline fuel blends

A 3-cylinder port fuel injection engine was adopted to study engine power, torque, fuel economy, emissions including regulated and non-regulated pollutants and cold start performance with the fuel of low fraction methanol in gasoline. Without any retrofit of the engine, experiments show that the engine power and torque will decrease with the increase fraction of methanol in the fuel blends under wide open throttle (WOT) conditions. However, if spark ignition timing is advanced, the engine power and torque can be improved under WOT operating conditions. Engine thermal efficiency is thus improved in almost all operating conditions. Engine combustion analyses show that the fast burning phase becomes shorter, however, the flame development phase is a little delay.When methanol/gasoline fuel blends being used, the engine emissions of carbon monoxide (CO) and hydrocarbon (HC) decrease, nitrogen oxides (NO_x) changes little prior to three-way catalytic converter (TWC). After TWC, the conversion efficiencies of HC, CO and NO_x are better. The non-regulated emissions, unburned methanol and formaldehyde, increase with the fraction of methanol, engine speed and load, and generally the maximum concentrations are less than 200 ppm. Experimental tests further prove that methanol and formaldehyde can be oxidized effectively by TWC. During the cold start and warming-up process at 5 °C, with methanol addition into gasoline, HC and CO emissions decrease obviously. HC emission reduces more than 50% in the first few seconds (cold start period) and nearly 30% in the following warming-up period, CO reduces nearly 25% when the engine is fueled with M30. Meanwhile, the temperature of exhaust increases, which is good to activate TWC.     

稀燃条件下甲醇汽油发动机燃烧和排放特性的试验研究

在一台汽油缸内直喷(GDI)增压发动机上,研究了稀燃条件下燃用不同甲醇汽油混合燃料的燃烧特性和排放特性。试验结果表明:稀燃条件下,随混合气浓度逐渐变稀,当量燃油消耗率呈现出先降低后升高的趋势,并且随着甲醇比例的增加,当量燃油消耗率增加,但均低于原机。在混合气逐渐变稀的过程中,燃烧时缸压峰值和燃烧温度总的变化趋势是逐渐降低,而燃烧持续期和循环变动率逐渐升高。稀燃条件下,CO排放量逐渐降低,碳氢化合物排放呈先降低后增加的趋势。NO_x排放量总的变化趋势是先增大后逐渐降低,随着甲醇体积分数的增加,NO_x的排放量逐渐降低,且3种甲醇、汽油混合燃料的NO_x和CO排放量都低于汽油燃料。     

HCCI甲醇发动机的燃烧与排放特性

在Ricardo Hydra单缸四冲程发动机上利用内部废气再循环策略实现了甲醇燃料的HCCI燃烧.通过调整HCCI发动机的过量空气系数和转速,研究了HCCI甲醇发动机的燃烧和排放特性.结果表明,甲醇燃料的HCCI燃烧不同于普通汽油,其着火更早、燃烧更快,但在低转速时,平均指示压力相对较低.甲醇燃料可以在更稀的混合气条件下实现HCCI燃烧.在相同的转速和过量空气系数下,甲醇燃料的NOx和HC排放低于汽油.     

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。     

基于缸内直喷的甲醇汽油混合燃料HCCI燃烧排放特性研究

在缸内直喷发动机上研究甲醇汽油混合燃料的HCCI燃烧排放特性,分析了其非常规排放的性能。试验中选用汽油、M10(甲醇体积分数10%)、M20(甲醇体积分数20%)3种燃料,并通过FTIR方法测量甲醇及甲醛等非常规排放。研究结果表明:在汽油中添加甲醇可以有效拓展HCCI燃烧的高负荷范围,M20燃料的高负荷范围比汽油提高近9%,指示燃油消耗率比汽油高5%～10%,但指示能量消耗率比汽油低2%～6%。CO、THC、NOx等常规排放随甲醇添加比例的增加而降低,而甲醇和甲醛等非常规排放随甲醇添加比例的增加而增加,并随负荷增高呈先增加后减少的趋势。     

进气压力对汽油低温压燃的影响

在一台装有电液可变气门的单缸柴油机上,通过改变进气压力,研究了不同喷油正时和内部废气再循环(EGR)率下汽油压燃的燃烧特性和排放特性,并对实现汽油燃料高效清洁稳定低温燃烧(如平均指示压力循环波动系数5%,NOx排放低于0.4g/(kW·h),烟度低于0.1FSN,CO和HC排放尽可能低)的控制区间进行了探索研究。内部EGR通过排气门两次开启实现,发动机转速和循环喷油量分别固定为1 500r/min和28mg。研究结果表明,基于燃油早喷、较低内部EGR率和适量进气压力(0.12MPa)的协同控制可以使辛烷值为93的汽油在平均指示压力约为0.47MPa的工况下实现高效清洁燃烧。     

甲醇-汽油混合燃料对汽油机性能影响的试验研究

在一台多点电喷汽油机上,开展了燃用不同掺混比的甲醇-汽油混合燃料时发动机的经济性、排放特性研究。结果表明:电喷汽油机燃用低掺混比甲醇-汽油(小于30%)时,随着甲醇掺混比的增加,经济性有所改善,有效热效率明显提高;CO的排放有明显改善,中低负荷时HC排放有所改善,高负荷时HC排放增加,NOx排放相当,而怠速工况时,排放特性变差。     

BUTANOL—A SINGLE CYLINDER ENGINE STUDY: ENGINE PERFORMANCE

The effect of methanol and butanol addition to gasoline on brake specific fuel consumption (b.s.f.c.), exhaust gas temperature, and thermal efficiency has been experimentally investigated. A Hydra single cylinder, spark ignition, fuel injection engine was used over a wide range of fuel/air equivalence ratio (ϕ=0⋅8 to 1⋅3) for 30% volume alcohol–gasoline blends. The goal of this work is to study the engine performance when methanol and butanol–gasoline blends are used. The performance measurements show that there is an increase in b.s.f.c. when using alcohol–gasoline blends, and b.s.f.c. of a butanol–gasoline blend is less than for a methanol–gasoline blend. The experimental results show that the engine thermal efficiency was decreased when fueled with alcohol–gasoline blends. It was found that there was about a 4.5% reduction in engine thermal efficiency at ϕ=1⋅0 when 30% butanol was blended with gasoline compared to pure gasoline. The exhaust gas temperature measurements show that there is an increase in temperature in the case of using gasoline as compared to alcohol–gasoline blends, and that the temperature reaches a maximum at ϕ≈1⋅1 when using gasoline and alcohol–gasoline blends. © 1997 by John Wiley & Sons, Ltd.     

点燃式发动机掺烧甲醇裂解气的研究

摘要甲醇裂解气(D.M)是甲醇在一定温度下发生裂解反应的产物(2H_2+CO),而发动机排气余热提供甲醇蒸发和裂解所需热量.当发动机使用汽油和富氢的甲醇裂解气时,能在较稀混合气下运行;为了获得更稀的混合气,对发动机进行了补气实验.结果表明,燃用混合燃料时热效率有较大的改善,燃烧稳定性加强.通过对示功图和放热规律的分析,明确了发动机经济性提高的原因.     

Investigation of hydrogen addition to methanol-gasoline blends in an SI engine

In this study, effects of hydrogen-addition on the performance and emission characteristics of Methanol-Gasoline blends in a spark ignition (SI) engine were investigated. Experiments were conducted with a four-cylinder and four stroke spark ignition engine. Performance tests were performed via measuring brake thermal efficiency, brake specific fuel consumption, cylinder pressure and exhaust emissions (CO, CO₂, HC, NOx). These performance metrics were analyzed under three engine load conditions (no load, 50% and 100%) with a constant speed of 2000 rpm. Methanol was added to the gasoline up to 15% by volume (5%, 10% and 15%). Besides, hydrogen was added to methanol-gasoline mixtures up to 15% by volume (3%, 6%, 9% and 15%). Results of this study showed that methanol addition increases BSFC by 26% and decreases thermal efficiency by 10.5% compared to the gasoline. By adding hydrogen to the methanol - gasoline mixtures, the BSFC decreased by 4% and the thermal efficiency increased by 2% compared to the gasoline. Hydrogen addition to methanol – gasoline mixtures reduces exhaust emissions by about 16%, 75% and 15% of the mean average values of HC, CO and CO2 emissions, respectively. Lastly, ?t was concluded that hydrogen addition improves combustion process; CO and HC emissions reduce as a result of the leaning effect caused by the methanol addition; and CO2 and NOx emission increases because of the improved combustion.     

Statistical analysis of the cyclic variations of heat release parameters in HCCI combustion of methanol and gasoline

Combustion instability and cyclic variations lead to the requirement of closed loop control for use of homogeneous charge compression ignition (HCCI) engine technology for automotive applications. The closed loop control of HCCI combustion requires robust combustion timing parameters with a systematic and detailed study of its variations vis-à-vis engine operating conditions. An experimental study is conducted to provide insight into cyclic variations of HCCI combustion phasing for two fuels (gasoline and methanol) using statistical techniques. In this study, cycle-to-cycle variations of heat release parameters such as Maximum Rate of Heat Release (ROHR_max), 10% Mass Burn Fraction (MBF), 50% MBF, 90% MBF and Indicated Mean Effective Pressure (IMEP) of HCCI combustion engine fueled with methanol and gasoline were investigated using a modified two-cylinder, four-stroke engine. The experiments were conducted with different engine operating conditions at constant intake air temperature (140 °C) and different air-fuel ratios at constant engine speed (1500 rpm). To evaluate the cycle-to-cycle variations of combustion parameters at different test conditions, coefficient of variation (COV) and standard deviation of parameters were used. The results showed that CA₅₀ (crank angle position of 50% MBF) is a robust parameter for the closed loop control of HCCI combustion.     

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。     

电控汽油机燃用中低比例甲醇汽油的试验研究

因电控汽油机具有空燃比自适应控制功能,将中、低比例甲醇汽油用作汽油机的燃料时,电控系统可以将混合气的实际空燃比维持在理论空燃比附近,从而能够保持汽油机平稳运转。本文对电控发动机燃用M25和M50甲醇汽油的动力性、燃油经济性和排放进行了试验研究,结果表明发动机的动力性与燃用RON93汽油时基本相当,以比能耗为指标的燃料经济性有所提高,燃烧中的CO、HC和NOx生成量显著降低,三效催化转化器对燃用甲醇汽油时的CO和HC的转化效率较高,但因燃用甲醇汽油时排气温度较低导致对NOx的转化效率有所降低。     

Experimental study on combustion and emissions performance of a hybrid hydrogen–gasoline engine at lean burn limits

Lean combustion is an effective way for improving the spark-ignited (SI) engine performance. Unfortunately, due to the narrow flammability of gasoline, the pure gasoline-fueled engines sometimes suffer partial burning or misfire at very lean conditions. Hydrogen has many excellent combustion properties that can be used to extend the gasoline engine lean burn limit and improve the gasoline engine performance at lean conditions. In this paper, a 1.6 L port fuel injection gasoline engine was modified to be a hybrid hydrogen–gasoline engine (HHGE) fueled with the hydrogen–gasoline mixture by mounting an electronically controlled hydrogen injection system on the intake manifolds while keeping the original gasoline injection system unchanged. A self-developed hybrid electronic control unit (HECU) was used to flexibly adjust injection timings and durations of gasoline and hydrogen. Engine tests were conducted at 1400 rpm and a manifolds absolute pressure (MAP) of 61.5 kPa to investigate the performance of an HHGE at lean burn limits. Three hydrogen volume fractions in the total intake gas of 1%, 3% and 4.5% were adopted. For a specified hydrogen volume fraction, the gasoline flow rate was gradually reduced until the engine reached the lean burn limit at which the coefficient of variation in indicated mean effective pressure (COVimep) was 10%. The test results showed that COVimep at the same excess air ratio was obviously reduced with the increase of hydrogen enrichment level. The excess air ratio at the lean burn limit was extended from 1.45 of the original engine to 2.55 of the 4.5% HHGE. The engine brake thermal efficiency, CO, HC and NO_x emissions at lean burn limits were also improved for the HHGE.     

Performance,combustion and exhaust emissions characteristics investigation using Citrullus colocynthis L. biodiesel in DI diesel engine

The aims of this study is to investigate the performance, combustion and exhaust emissions of a single-cylinder, air cooled, direct injection (DI), compression ignition engine using biodiesel from non-edible feedstock. In this work, biodiesel (B100) used to lead this investigation is Citrullus colocynthis L. methyl ester (CCME) and its blends B30 with diesel fuel. The biodiesel is produced via alkaline-catalyzed transesterification process using methanol (6:1 M ratio), 1% of sodium hydroxide at the reaction temperature of 60 °C for 1 h. The important physical and chemical properties of CCME are close to those of diesel fuel. Fuels (diesel fuel, B100 and B30) were tested on a DI diesel engine at 1500 rpm for various power outputs. The results indicated that B100 and B30 exhibit the same combustion characteristics compared to diesel fuel. However, B100 and B30 display earlier start of combustion. At lower engine loads, the peaks of cylinder pressure and heat release rate (HRR) were higher for B30 than B100 and diesel fuel during premixed combustion period. At higher engine loads the peaks of cylinder pressure was higher for B100 than B30 and diesel fuel, but the HRR during diffusion combustion is more considerable than diesel fuel. The brake specific fuel consumption (BSFC) was higher for B100 than diesel fuel at all engine loads while B30 exhibited comparable trends. The thermal efficiency is slightly higher for B100 than B30 and diesel fuel at low loads and increase for B30 at full loads.B30 and B100 provided a higher reduction of hydrocarbons emissions up to 50% for B100. Nitrogen oxides and particulate matter emissions were also reduced.     

Evaluation of hydrogen-containing NaBH4 and oxygen-containing alcohols (CH3OH,C2H5OH) as fuel additives in a gasoline engine

The aim of this study is to obtain alternative fuels with hydrogen-containing (NaBH₄) and oxygen-containing (ethanol, methanol) fuel additives and to test these fuels in a gasoline engine. For this purpose, each of the NaBH₄ added ethanol and methanol solutions was added to pure gasoline at a volume of 10% and mixed fuels named SE10 and SM10 were obtained, respectively. The obtained SE10 and SM10 mixed fuels were tested in a spark ignition engine and the performance and emission effects of the fuels were compared with the pure gasoline fueled engine test data. When the test results of the mixture fuel engine were compared with the test results of the engine running with pure gasoline, the torque of the SE10 fuel engine decreased compared to the pure gasoline engine, while the torque of the SM10 blended engine increased. In addition, while the exhaust gas temperatures of both blended fuels decreased, their specific fuel consumption and thermal efficiency increased. On the other hand, adding NaBH₄ doped ethanol and methanol solutions to pure gasoline resulted in better combustion, reductions in CO emissions of SE10 and SM10 blended fuels by 31.04% and 53.7%, but CO₂ emissions increased by 11.20% and 19.51% respectively. In addition, NO_x emissions of SE10 and SM10 blended fuels decreased by 15.17% and 8.73%, respectively.     

Realizing low emissions on a hydrogen-fueled spark ignition engine at the cold start period under rich combustion through ignition timing control

This paper analyzed low emissions on a hydrogen-fueled spark ignition (SI) engine at the cold start period under rich combustion through ignition timing (IT) control. Cold start characteristics of hydrogen-fueled engine were investigated experimentally. The study was performed under different IT. The results demonstrated that when excess air ratio (λ) was 0.7 and IT varied from 25 °CA BTDC to 10 °CA ATDC, the peak cylinder pressure of the first cycle and the successful start time (SST) of hydrogen engine first increased and then decreased with the retard of IT. At 15 °CA BTDC, the hydrogen engine gained the shortest SST and the highest cylinder pressure in the first cycle. Flame development period (CA0-10) first shortened and then lengthened, and flame propagation period (CA10-90) prolonged when IT gradually retarded. The average NOx emissions efficiently reduced by 90.2%, HC and CO emissions caused by the evaporated lubricant oil reduced individually by 33.8% and 19.7% in the first 6 s during the cold start process with the retard of IT. Especially when IT delayed from 25 °CA BTDC to 15 °CA BTDC, the effect of IT on HC emissions was significant.     

甲醇裂解气发动机排放性能试验

以一台点火式电控发动机为研究对象,甲醇裂解装置安装在发动机排气管上回收废气余热,进行了甲醇裂解气在点燃式发动机上应用燃烧的排放性能试验研究.研究表明:通过甲醇裂解气在发动机上的稀燃,其动力性较之原机稍微有所下降,下降幅度仅为5%;甲醇裂解气发动机利用回收废气余热以及稀燃条件减少泵吸损失的优势,对比与原汽油机经济性有较大的提高.同时,稀燃可使NOx排放较原汽油机降低90%;与汽油机CO对比,降低了50%左右,而HC排放接近汽油;此外,甲醇裂解气发动机尾气中的非常规排放物甲醛的体积分数低于汽油机,经过尾气处理后,甲醛排放接近零排放,原机三效催化转化器对甲醛的消除有很好的效果.     

E30w含水乙醇汽油对电喷汽油机性能和排放的影响

在SQR481F电喷发动机上进行了E30w含水乙醇汽油与93#纯汽油的动力性、经济性与排放特性对比试验研究。试验结果表明：在电喷汽油机未做任何调整的情况下,燃用E30w含水乙醇汽油后,功率下降约3.4%～12.1%;有效燃油消耗率较93#纯汽油增加,当量燃油消耗率有所降低;CO和HC的排放量明显改善,最大下降幅度分别为12.6%和22.4%,NOx无明显改善。