Investigations on the combustion parameters of a dual fuel diesel engine with hydrogen and LPG as secondary fuels

This paper presents a detailed experimental investigations on the combustion parameters of a 4 cylinder (turbocharged and intercooled) 62.5 kW gen-set duel fuel diesel engine (with hydrogen and LPG as secondary fuels). A detailed account on maximum rate of pressure rise, peak cylinder pressure, heat release rate in first phase of combustion and combustion duration at a wide range of load conditions with different gaseous fuel substitutions has been presented in the paper. When 30% of hydrogen alone is used as secondary fuel, maximum rate of pressure rise increases by 0.82 bar/deg CA as compared to pure diesel operation, while, peak cylinder pressure and combustion duration increase by 8.44 bar and 5 deg CA respectively. When 30% of LPG alone is used as secondary fuel, the enhancements in maximum rate of pressure rise, peak cylinder pressure and combustion duration are found to be 1.37 bar/deg CA, 6.95 bar and 5 deg CA respectively. It is also found that heat release rate in first phase of combustion reduces at all load conditions as compared to the pure diesel operation in both types of fuel substitutions.One important finding of the present work is significant enhancement in performances of dual fuel engine when hydrogen-LPG mixture is used as the secondary fuel. The highlight of this case is that when the mixture of LPG and hydrogen (40% in the ratio LPG: hydrogen = 70:30) is used as secondary fuel, maximum rate of pressure rise (by 0.88 bar/deg CA) and combustion duration reduces (by 4 deg CA), while, peak cylinder pressure and heat release rate in first phase of combustion increase by 5.25 bar and 35.24 J/deg CA respectively.     

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。     

Theoretical and experimental investigations on the performance of dual fuel diesel engine with hydrogen and LPG as secondary fuels

The mathematical models to predict pressure, net heat release rate, mean gas temperature, and brake thermal efficiency for dual fuel diesel engine operated on hydrogen, LPG and mixture of LPG and hydrogen as secondary fuels are developed. In these models emphasis have been given on spray mixing characteristics, flame propagation, equilibrium combustion products and in-cylinder processes, which were computed using empirical equations and compared with experimental results. This combustion model predicts results which are in close agreement with the results of experiments conducted on a multi cylinder turbocharged, intercooled gen-set diesel engine. The predictions are also in close agreement with the results on single cylinder diesel engine obtained by other researchers. A reasonable agreement between the predicted and experimental results reveals that the presented model gives quantitatively and qualitatively realistic prediction of in-cylinder processes and engine performances during combustion.     

Production of waste tyre oil and experimental investigation on combustion,engine performance and exhaust emissions

In this study, waste tyre was pyrolyzed at different conditions such as temperature, heating rate and inert purging gas (N₂) flow rate. Pyrolysis parameters were optimized. Optimum parameters were determined. The main objective of this study was to investigate combustion, performance and emissions of diesel and waste tyre oil fuel blend. Experimental investigation was performed in a single cylinder, direct injection, air cooled diesel engine at maximum engine torque speed of 2200 rpm and four different engine load including 3.75, 7.5, 11.25 and 15 Nm. The effects of waste tyre oil on combustion characteristics such as cylinder pressure, heat release rate, ignition delay (ID), combustion duration, engine performance were investigated. In-cylinder pressure and heat release rate increased with waste tyre oil fuel blend (W10) with the increase of engine load. In addition, ID was shortened with the increase of engine load for test fuels but it increased with the addition of waste tyre oil. Lower imep values were obtained because of the lower calorific value of waste tyre oil fuels. Maximum thermal efficiencies were determined as 28.27% and %25.12 with diesel and W10 respectively at 11.25 Nm engine load. When test results were examined, it was seen that waste tyre oil highly affected combustion characteristics, performance and emissions.     

双燃料发动机燃烧放热规律分析及燃烧特性研究

从热力学和内燃机燃烧的基本理论入手 ,推导了计算分析双燃料发动机缸内工质成分和热力学参数的计算关系式以及求解双燃料发动机燃烧放热规律的微分方程式 ,基于面向对象技术开发了双燃料发动机燃烧放热规律计算软件。研究结果表明 :用传统柴油机分析方法计算双燃料发动机的放热率峰值偏小 ,所计算的缸内工质平均温度偏高 ,新模型计算的结果与实际情况更为吻合。该分析软件可以适用于多种燃料发动机 ,是内燃机燃烧放热规律的通用计算软件。双燃料发动机燃烧特性研究表明 :双燃料发动机初始放热率比纯柴油大 ,若着火始点在上止点后 ,双燃料缸内最大爆发压力比纯柴油低 ,否则比纯柴油高 ;控制双燃料发动机着火始点是控制缸内最大爆发压力和 NOx 排放的关键 ,双燃料发动机着火始点应在上止点后 ,可以使发动机爆发压力和 NOx 排放比纯柴油低。     

LPG点燃式发动机冷起动首循环进气富氧试验研究

基于循环控制,详细研究了LPG点燃式发动机冷起动首循环进气富氧的燃烧及排放特性。试验在一台电控LPG进气喷射单缸风冷四冲程125 mL发动机上进行,采用膜式富氧方法实现富氧进气燃烧。研究表明:当过量空气系数大于0．7时,富氧进气燃烧缸压峰值与空气相比增加不显著,此后随混合气加浓,富氧进气燃烧缸压峰值开始明显大于常规空气进气燃烧;过量空气系数在0．4～0．876时,富氧进气燃烧与常规空气进气燃烧相比,HC排放没有较大降低,在此范围之外,富氧显著降低HC排放;过量空气系数在0．4～0．7,富氧与空气相比CO显著降低;富氧进气燃烧,使得首循环NO排放大幅增加;计算放热率发现,富氧燃烧速度比常规空气进气燃烧更快,放热更集中。     

S.I. engine fuelled with gasoline,methane and methane/hydrogen blends: Heat release and loss analysis

Experiments were carried out to investigate the performance of different fuels used in a internal combustion engine: gasoline, methane and fuel blends containing methane with 5%, 10% and 15% hydrogen by volume, respectively. A two-litre naturally aspirated bi-fuel engine with port fuel injection was used. The engine was operated stoichiometrically. For each fuel the spark advance for best efficiency was determined. Experiments were conducted at 2000 rpm and 2 bar brake mean effective pressure. A heat release analysis and a loss analysis were performed for all fuels. The main findings are that increasing the hydrogen fraction of the methane hydrogen fuel blend decreases the overall burn duration. This decrease is predominantly achieved by a shortened duration of the fist stage of combustion (ignition to 5% mass fraction burned). The faster combustion comes along with an increase in fuel conversion efficiency. The different losses for gasoline and pure methane operation interact such that equal fuel conversion efficiencies result. However, care has to be taken when comparing fuel conversion efficiencies among the different fuels as the relative error in fuel conversion efficiency for the gaseous fuels is 0.2% at most, whereas it is about 1% for gasoline.     

Preparation,characterization, engine combustion and emission characteristics of rapeseed oil based hybrid fuels

In this study, hybrid fuels consisting of rapeseed oil/diesel blend, 1% aqueous ethanol and a surfactant (oleic acid/1-butanol mixture) were prepared and tested as a fuel in a direct injection (DI) diesel engine. The main fuel properties such as the density, viscosity and lower heating value (LHV) of these fuels were measured, and the engine performance, combustion and exhaust emissions were investigated and compared with that of diesel fuel. The experimental results showed that the viscosity and density of the hybrid fuels were decreased and close to that of diesel fuel with the increase of ethanol volume fraction up to 30%. The start of combustion was later than that of diesel fuel and the peak cylinder pressure, peak pressure rise rate and peak heat release rate were higher than those of diesel fuel. The brake specific fuel consumption (BSFC) of hybrid fuels was increased with the volume fraction of ethanol and higher than that of diesel. The brake specific energy consumption (BSEC) was almost identical for all test fuels. The smoke emissions were lower than those for diesel fuel at high engine loads, the NO_x emissions were almost similar to those of diesel fuel, but CO and HC emissions were higher, especially at low engine loads.     

Dual-injection: The flexible,bi-fuel concept for spark-ignition engines fuelled with various gasoline and biofuel blends

Dual-injection strategies in spark-ignition engines allow the in-cylinder blending of two different fuels at any blend ratio, when simultaneously combining port fuel injection (PFI) and direct-injection (DI). Either fuel can be used as the main fuel, depending on the engine demand and the fuel availability. This paper presents the preliminary investigation of such a flexible, bi-fuel concept using a single cylinder spark-ignition research engine. Gasoline has been used as the PFI fuel, while various mass fractions of gasoline, ethanol and 2,5-dimethylfuran (DMF) have been used in DI. The control of the excess air ratio during the in-cylinder mixing of two different fuels was realized using the cross-over theory of the carbon monoxide and oxygen emissions concentrations. The dual-injection results showed how the volumetric air flow rate, total input energy and indicated mean effective pressure (IMEP) increases with deceasing PFI mass fraction, regardless of the DI fuel. The indicated efficiency increases when using any ethanol fraction in DI and results in higher combustion and fuel conversion efficiencies compared to gasoline. Increasing the DMF mass fraction in DI reduces the combustion duration more significantly than with increased fractions of ethanol or gasoline in DI. The hydrocarbon (HC), oxides of nitrogen (NO_x) and carbon dioxide (CO₂) emissions mostly reduce when using any gasoline or ethanol fraction in DI. When using DMF, the HC emissions reduce, but the NO_x and CO₂ emissions increase.     

Second-law analyses applied to a spark ignition engine under surrogate fuels for gasoline

Availability analysis is applied to cylinder of a spark ignition engine during the combustion process under surrogate fuels (iso-octane, n-heptane, toluene, and methyl-cyclohexane) for gasoline using a two-zone combustion model. Special attention is given to identification and quantification of irreversibility of combustion process basing on the surrogate fuels. This is particularly important since the identification and quantification of irreversibility are not identified in traditional first-law analysis. In identifying these processes, the main differences between second- and first-law analyses are also highlighted. During the combustion process, the availability destroyed by combustion is about 18.9%, and the availability destroyed by the heat transfer is about 12.0%. The survey also reveals that during the whole combustion process shortened combustion duration and postponed ignition are both helpful to reduce availability destruction.     

富氧条件下汽油机燃烧反应参数及动力性能研究

从燃烧化学角度,对汽油发动机的燃烧过程进行分析,利用化学平衡原理,对富氧燃烧状态下的空燃比、燃油燃烧热值及燃烧温度进行分析计算,进行不同氧气浓度空气助燃下发动机系列试验,对富氧状态下发动机的动力性能及气缸压力进行对比分析。结果表明,富氧燃烧能够提高燃油燃烧的的理论热值,提高发动机气缸压力,进而使发动机输出转矩增加。     

燃料敏感性对部分预混燃烧影响的试验研究

配制辛烷值相同而敏感性不同的高辛烷值燃料,在一台改造的单缸试验发动机上进行了燃料敏感性对部分预混燃烧的燃烧和排放特性影响的研究。采用的不同敏感性的燃料为配制的甲苯参比燃料和市售92#汽油。研究结果表明:燃料敏感性越高,滞燃期越长,油气混合越充分,预混燃烧比例越大,NOx排放越高。燃烧重心(CA50)随着敏感性的增高先推迟后提前,敏感性为2的燃料CA50最迟。燃料敏感性越低,压升率越低,而市售92#汽油挥发性较强,预混比例较大,最大压升率最高;敏感性为2的燃料在上止点附近放热较多,指示热效率较高;汽油及敏感性为5和8的燃料的碳烟排放比其他燃料低。     

Investigation of hydrogen usage on combustion characteristics and emissions of a spark ignition engine

In this study, initially, a single cylinder, naturally aspirated, spark ignition engine was loaded with AC engine dynamometer and a spark plug type engine transducer was used to obtain in-cylinder pressure. The test engine was operated with gasoline fuel at full load and different engine speeds (3100, 3200, 3300, 3400 and 3450 rpm). Secondly, using obtained engine performance, emission values and in-cylinder pressure, a one dimensional engine model was built and validated by an engine performance and emission analysis software (AVL-Boost). After the validation of single dimensional theoretical engine model, a comparison was made between the emission, performance and combustion (in-cylinder pressure, rate of heat release) values of operations with pure hydrogen fuel and such values of the operations with unleaded gasoline. The emissions of CO and total hydrocarbons (THC) were negligible with using hydrogen as fuel in SI engine. A dramatic increase in NO_x emissions was obtained with using hydrogen as fuel. However, by using hydrogen in lean conditions, NO_x emissions were taken under control by means of wide flammability limits of hydrogen.     

Reduction of smoke and nitrogen oxides of a partial HCCI engine using premixed gasoline and ethanol with air

This paper investigates the combustion and emissions characteristics for a partial homogeneous charge compression ignition (HCCI) engine by injecting gasoline and ethanol into the intake port of a diesel engine with diesel fuel injected in cylinder. The experiments were conducted on a diesel engine at premixed ratio (0, 10, 20, and 30) with injection timings (0–65° BTDC), under engine speeds (1200, 1500, and 1800 rpm) and loads (10 and 20 N m). The experimental results are compared with the numerical results and found to be reasonable. The results show that the injection timing of auxiliary fuels obtains less smoke concentration at 25° BTDC than at other crank angles. The diesel engine with premixed gasoline and ethanol can reduce emissions effectively; in particular, premixed ethanol affects the emissions reduction more than premixed gasoline does. The temperature contours and velocity fields in engine cylinder from the numerical calculation are also varied with engine load for various auxiliary fuels.     

汽油机非稳定加速工况燃烧放热率计算模型的修正

要对发动机非稳定工况实施最优控制,就应对其在非稳定工况下的工作过程做深入的研究。求取燃烧放热率是进行燃烧过程优化研究的基本手段,但在迄今为止的各种燃烧分析仪中,给出的多为稳定工况分析结果。作依据４９２Ｑ汽油机加速过程的试验结果,修正了汽油机燃烧放热率计算的热力学模型,使之适用于非稳定工况最后,通过实测示功图分析了４９２Ｑ汽油机沿外特性加速过程的放热特性和指示效率。     

Validation of a ternary gasoline surrogate in a CAI engine

This experimental study validated in a piston engine the European gasoline surrogate from [Pera and Knop, Fuel 96 (2012) 59–69], consisting of a ternary mixture of n-heptane, iso-octane, and toluene. Because only the gas phase properties of gasoline were emulated with the selected mixture, this validation was deliberately limited to port fuel injection operating points. By considering engine operation under controlled autoignition (CAI) combustion mode, the validation focused on fuel autoignition characteristics (autoignition delay and rate of heat release). A direct comparison of gasoline and its surrogate over the entire CAI operating range permitted a comprehensive evaluation of the surrogate adequacy under purely kinetically controlled combustion mode. The acquired data include autoignition timings, rate of heat release, exhaust gas temperatures, pollutant emissions, operating point stability, and operating ranges under CAI combustion mode. Good agreement between gasoline and its surrogate was obtained for all quantities, indicating similar behavior for the two fuels. Experimental results showed that a mixture of 13.7 mol% n-heptane, 42.9 mol% iso-octane, and 43.4 mol% toluene is a satisfactory surrogate for a European unleaded gasoline with a research octane number of 95, conforming to the EN 228 specification.     

柴油/汽油反应活性控制压燃发动机喷油协调控制与排放特性研究

对某4缸高压共轨柴油机进气道进行改造,搭建了柴油/汽油双燃料反应活性控制压燃(reactivity controlled compression ignition,RCCI)发动机专用试验台架,设计了柴油/汽油双燃料RCCI燃烧汽油喷射控制策略,实现了全工况下汽油与柴油的协调喷射控制,系统地研究了不同运行工况下,不同汽油替代率对柴油机燃烧与排放性能的影响规律。结果表明:采用柴油/汽油双燃料RCCI燃烧控制策略,发动机可在其运行工况范围内实现高效清洁燃烧,随着汽油替代率的增加,发动机缸内最高压力逐渐增大,缸压峰值出现时刻推迟,放热率峰值降低,燃烧持续期延长,燃油消耗率降低,有效热效率升高,全碳氢、CO排放增加,NOx和碳烟排放降低。     

基于高压直喷航空煤油点燃式发动机燃烧性能优化的试验研究

为提高航空煤油在点然式发动机中的燃烧热效率,改善发动机爆震及拓宽发动机负荷范围,以3号航空煤油(RP-3)为基础燃料,基于一台单缸水冷、压缩比可调、4冲程点燃式发动机结合高压共轨缸内直喷技术,开展了单双点火、不同负荷、压缩比、喷射压力、喷射时刻和两次喷射策略下航空煤油燃烧特性的试验研究。结果表明,在原机压缩比为10的条件下,将直喷汽油改为直喷航空煤油后,由于航空煤油的抗爆性差、雾化困难、燃烧速率慢等理化特性,发动机的动力性损失约50.0%,油耗增加约60.0%,循环波动也大幅增加;相比于单点火,双点火可使缸内平均有效压力提高,燃烧相位提前,循环波动降低;为了抑制高压缩比下的爆震倾向,可通过降低压缩比来拓宽负荷范围,恢复原机功率。随着压缩比的降低,有效平均压力(BMEP)持续增大,当压缩比为6时,最大转矩可达39.5N·m,功率恢复至原机的88.0%。同时耦合高压及两次喷射策略,随着喷射压力的增大,有效燃油消耗率(BSFC)减小约30.0%,经济性有所提高。相比于单次喷射,采用两次喷射策略可降低油耗,提升缸内有效平均压力,提升燃烧效率,最终可实现发动机燃用航空煤油的性能接近原机水平,最大负荷达原机的90.0%且油耗增加量不超过15.0%。     

Performance and combustion characteristics of biodiesel–diesel–methanol blend fuelled engine

An experimental investigation was conducted to evaluate the effects of using methanol as additive to biodiesel–diesel blends on the engine performance, emissions and combustion characteristics of a direct injection diesel engine under variable operating conditions. BD50 (50% biodiesel and 50% diesel in vol.) was prepared as the baseline fuel. Methanol was added to BD50 as an additive by volume percent of 5% and 10% (denoted as BDM5 and BDM10). The results indicate that the combustion starts later for BDM5 and BDM10 than for BD50 at low engine load, but is almost identical at high engine load. At low engine load of 1500 r/min, BDM5 and BDM10 show the similar peak cylinder pressure and peak of pressure rise rate to BD50, and higher peak of heat release rate than that of BD50. At low engine load of 1800 r/min, the peak cylinder pressure and the peak of pressure rise rate of BDM5 and BDM10 are lower than those of BD50, and the peak of heat release rate is similar to that of BD50. The crank angles at which the peak values occur are later for BDM5 and BDM10 than for BD50. At high engine load, the peak cylinder pressure, the peak of pressure rise rate and peak of heat release rate of BDM5 and BDM10 are higher than those of BD50, and the crank angle of peak values for all tested fuels are almost same. The power and torque outputs of BDM5 and BDM10 are slightly lower than those of BD50. BDM5 and BDM10 show dramatic reduction of smoke emissions. CO emissions are slightly lower, and NO_x and HC emissions are almost similar to those of BD50 at speed characteristic of full engine load.     

The effect of adding dimethyl carbonate (DMC) and ethanol to unleaded gasoline on exhaust emission

Oxygen containing additives are usually used to improve gasoline’s performance and reduce exhaust emissions. In this study, the effect of oxygen containing additives on gasoline blended fuels on exhaust emissions was investigated for different engine speeds in a single cylinder, four-stroke, spark-ignition engine. The results indicate that CO and HC exhaust emissions are lower with the use of ethanol–gasoline and DMC–gasoline blended fuels as compared to the use of unleaded gasoline. On the other hand, the effect of ethanol–gasoline and DMC–gasoline blended fuels on NO_X exhaust emission is insignificant. Using oxygen containing additives can increase fuel consumption as a result of the heating value of the blended fuels being lower than that of unleaded gasoline.