Analysis of ignition delay by taking Di-tertiary-butyl peroxide as an additive in a dual fuel diesel engine using hydrogen as a secondary fuel

Ignition delay (ID) is one of the important parameters that make influenced on the combustion process inside the cylinder. This ignition delay affects not only the performances but also the noise and emissions of the engine. In this regards the experiments were conducted on single cylinder 4–stroke compression ignition research diesel engine, power 3.50 kW at constant speed 1500 rpm Kirloskar model TV1 with base fuel as diesel and hydrogen as secondary fuel with and without Di-tertiary-butyl-peroxide (DTBP). Experiments were conducted to measure the ignition delay of the dual fuel diesel (DFD) engine at different load conditions and substitution of diesel by hydrogen with or without DTBP and then it was compared with predicted ID given by Hardenberg-Hase equation and modified Hardenberg-Hase equation.The experimental values of ignition delay were compared with theoretical ignition delay which was predicted on the basis of Hardenberg-Hase equation by considering mean cylinder temperature, pressure, activation energy and cetane number and variations are found in between 6.60% and 21.22%. While, the Hardenberg-Hase equation was modified (by considering variation in activation energy) for DFD engine working on diesel as primary fuel and hydrogen as secondary fuel shows variations 1.20%–11.96%. Furthermore, with DTBP it gives variation up to 18.01%. It was found that ID decreases with increase in percentage of DTBP and hydrogen in air-fuel mixture. This might be due to the cetane improver nature of DTBP, pre-ignition reaction rate and energy release rate of hydrogen fuel. The polytropic index get increased by addition of (Di-tert butyl peroxide) DTBP. Similarly, 5% Di tertiary butyl peroxide reduces Ignition delay.     

Effect of hydrogen and LPG addition on the efficiency and emissions of a dual fuel diesel engine

This paper presents some experimental investigations on dual fuel operation of a 4 cylinder (turbocharged and intercooled) 62.5 kW gen-set diesel engine with hydrogen, liquefied petroleum gas (LPG) and mixture of LPG and hydrogen as secondary fuels. Results on brake thermal efficiency and emissions, namely, un-burnt hydrocarbon (HC), carbon monoxide (CO), NO_x and smoke are presented here. The paper also includes vital information regarding performances of the engine at a wide range of load conditions with different gaseous fuel substitutions. When only hydrogen is used as secondary fuel, maximum enhancement in the brake thermal efficiency is 17% which is obtained with 30% of secondary fuel. When only LPG is used as secondary fuel, maximum enhancement in the brake thermal efficiency (of 6%) is obtained with 40% of secondary fuel. Compared to the pure diesel operation, proportion of un-burnt HC and CO increases, while, emission of NO_x and smoke reduces in both cases. On the other hand, when 40% of mixture of LPG and hydrogen is used (in the ratio 70:30) as secondary fuel, brake thermal efficiency enhances by 27% and HC emission reduces by 68%. Further, shortcoming of low efficiency at lower load condition in a dual fuel operation is removed when a mixture of hydrogen and LPG is used as the secondary fuel at higher than 10% load condition.     

Effect on performance and emissions of a dual fuel diesel engine using hydrogen and producer gas as secondary fuels

Energy is an essential prerequisite for economical and social growth of any country. Skyrocketing of petroleum fuel cost s in present day has led to growing interest in alternative fuels like CNG, LPG, Producer gas, Biogas in order to provide suitable substitute to diesel for a compression ignition engine. This paper discusses some experimental investigations on dual fuel operation of a 4 cylinder (turbocharged and intercooled) 62.5 kW gen-set diesel engine with hydrogen, producer gas (PG) and mixture of producer gas and hydrogen as secondary fuels. Results on brake thermal efficiency and emissions, namely, un-burnt hydrocarbon (HC), carbon monoxide (CO), and NO_x are presented here. The paper also contains vital information relating to the performances of an engine at a wide range of load conditions with different gaseous fuel substitutions. When only hydrogen is used as secondary fuel, maximum increase in the brake thermal efficiency is 7% which is obtained with 20% of secondary fuel. When only producer gas is used as secondary fuel, maximum decrease in the brake thermal efficiency of 8% is obtained with 30% of secondary fuel. Compared to the neat diesel operation, proportion of un-burnt HC and CO increases, while, emission of NO_x reduces in all Cases. On the other hand, when 40% of mixture of producer gas and hydrogen is used (in the ratio (60:40) as secondary fuel, brake thermal efficiency reduces marginally by 3%. Further, shortcoming of low efficiency at lower load condition in a dual fuel operation is removed when a mixture of hydrogen and producer gas is used as the secondary fuel at higher than 13% load condition. Based on the performance studied, a mixture of producer gas and hydrogen in the proportion of 60:40 may be used as a supplementary fuel for diesel conservation.     

活性添加剂对高辛烷值燃料HCCI着火时刻与燃烧速率的影响

为研讨活性添加剂过氧化二叔丁基(DTBP)对高辛烷值燃料以HCCI燃烧模式运行时的放热率特征、着火时刻、燃烧持续期和排放特性的影响,在一台单缸发动机上,在辛烷值为90(RON90)(90％的异辛烷和10％的正庚烷)的混合燃料中加入不同比例(0～4％)的DTBP,考察5种燃料在1800r／min下不同负荷时的燃烧特性和排放特性．实验结果表明：RON90中没有添加剂时,只能在高温、高负荷下才能以HCCI燃烧模式运行;在其中加入少量的DTBP后,RON90实现HCCI燃烧的工况范围向低温低负荷下大幅度拓展．各种燃料的HCCI燃烧冷焰反应发生在850K左右,到950K结束,进入负温度系数区(NTC),在1125K左右突破NTC区而发生热着火．随DTBP含量增加,系统温度达到冷焰反应和热焰反应的化学时间尺度缩短,因此着火时刻提前,燃烧持续期缩短,特别是提高了低负荷下的燃烧速率．添加剂使各种当量比下未燃碳氢(UHC)和一氧化碳(CO)排放显著改善,NOx排放也保持在很低的水平．     

An experimental investigation of NO2 emission characteristics of a heavy-duty H2-diesel dual fuel engine

This paper investigated the nitrogen dioxide (NO₂) emissions of a heavy-duty diesel engine operated in hydrogen (H₂)-diesel dual fuel combustion mode with H₂ supplemented into the intake air. Preliminary measurements using the 13-mode European Stationary Cycle (ESC) demonstrated the significant effect of H₂ addition on the emissions of NO₂. The detailed effects of H₂ addition and engine load on NO₂ emissions were examined at 1200 RPM. The addition of a small amount of H₂ increased substantially the emissions of NO₂ and the NO₂/NO_x ratio, especially at low load. Increasing the engine load was found to inhibit the enhancing effect of H₂ on the conversion of NO to NO₂ with the maximum NO₂/NO_x ratio observed at lower H₂ concentration. The maximum NO₂ emissions of the H₂-diesel dual fuel operation were three (at 70% load) to five (at 10% load) times that of diesel operation. Further increasing the addition of H₂ beyond the point with maximum NO₂ emissions still produced more NO₂ than for diesel-only operation. Based on the experimental data obtained, the engine load and maximum averaged bulk mixture temperature were not the main factors dominating the formation of NO₂ in the H₂-diesel dual fuel engine. A preliminary analysis demonstrated the significant effect of the unburned H₂ on NO₂ emissions. When mixed with the hot combustion product, the unburned H₂ that survived the main combustion process might further oxidize to raise the HO₂ levels and enhance the conversion of NO to NO₂. In comparison, the changes in the combustion process including the start of combustion, combustion duration and maximum heat release rate may not contribute substantially to the increased NO₂ emissions observed.     

An insight on hydrogen fuel injection techniques with SCR system for NOX reduction in a hydrogen–diesel dual fuel engine

Internal combustion engines continue to dominate in many fields like transportation, agriculture and power generation. Among the various alternative fuels, hydrogen is a long-term renewable and less polluting fuel (Produced from renewable energy sources). In the present experimental investigation, the performance and emission characteristics were studied on a direct injection diesel engine in dual fuel mode with hydrogen inducted along with air adopting carburetion, timed port and manifold injection techniques. Results showed that in timed port injection, the specific energy consumption reduces by 15% and smoke level by 18%. The brake thermal efficiency and NO_X increases by 17% and 34% respectively compared to baseline diesel. The variation in performance between port and manifold injection is not significant. The unburnt hydrocarbons and carbon monoxide emissions are lesser in port injection. The oxides of nitrogen are higher in hydrogen operation (both port and manifold injection) compared to diesel engine. In order to reduce the NO_X emissions, a selective catalytic converter was used in hydrogen port fuel injection. The NO_X emission reduced upto a maximum of 74% for ANR (ratio of flow rate of ammonia to the flow rate of NO) of 1.1 with a marginal reduction in efficiency. Selective catalytic reduction technique has been found to be effective in reducing the NO_X emission from hydrogen fueled diesel engines.     

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.     

Effect of induction on exhaust gas recirculation and hydrogen gas in compression ignition engine with simarouba oil in dual fuel mode

Biofuels extracted from non-edible oil is sustainable and can be used as an alternative fuel for internal combustion engines. This study presents the performance, emission and combustion characteristic analysis by using simarouba oil (obtained from Simarouba seed) as an alternative fuel along with hydrogen and exhaust gas recirculation (EGR) in a compression ignition (CI) engine operating on dual fuel mode. Simarouba biofuel blend (B20) was prepared on volumetric basis by mixing simarouba oil and diesel in the proportion of 20% and 80% (v/v), respectively. Hydrogen gas was introduced at the flow rate of 2.67 kg/min, and EGR concentration was maintained at 30% of total air introduction. Performance, combustion and emission characteristics analysis were examined with biodiesel (B20), biodiesel with hydrogen substitution and biodiesel, hydrogen with EGR and were compared with neat diesel operation. Results indicate that BTE of the engine operating with biodiesel B20 was decreased when compared to neat diesel operation. However, introducing hydrogen along with B20 blend into the combustion chamber shows a slight increase in the BTE by 1%. NO_x emission was increased to 18.13% with the introduction of hydrogen than that of base fuel (diesel) operation. With the introduction of EGR, there is a significant reduction in NO_x emission due to decrease in in-cylinder temperature by 19.07%. A significant reduction in CO, CO_2, and smoke emissions were also noted with the introduction of both hydrogen and EGR. The ignition delay and combustion duration were increased with the introduction of hydrogen, EGR with biodiesel than neat diesel operation. Hence, the proposed biodiesel B20 with H₂ and EGR combination can be applied as an alternative fuel in CI engines.     

Effect of pilot fuel injection pressure and injection timing on combustion,performance and emission of hydrogen-biodiesel dual fuel engine

The present study highlights the influence of fuel injection pressure (FIP) and fuel injection timing (FIT) of Jatropha biodiesel as pilot fuel on the performance, combustion and emission of a hydrogen dual fuel engine. The hydrogen flow rates used in this study are 5lit/min, 7lit/min, and 9lit/min. The pilot fuel is injected at three FIPs (500, 1000, and 1500 bar) and at three FITs (5°, 11°, and 17?bTDC). The results showed an increase in brake thermal efficiency (B_th)from 25.02% for base diesel operation to 32.15% for hydrogen-biodiesel dual fuel operation with 9lit/min flow rate at a FIP of 1500 bar and a FITof17?bTDC. The cylinder pressure and heat release rate (HRR) are also found to be higher for higher FIPs. Advancement in FIT is found to promote superior HRR for hydrogen dual fuel operations. The unburned hydrocarbon (UHC) and soot emissions are found to reduce by 59.52% and 46.15%, respectively, for hydrogen dual fuel operation with 9lit/min flow rate at a FIP of 1500 bar and a FIT of 11?bTDC. However, it is also observed that the oxides of nitrogen (NO_X) emissions are increased by 20.61% with 9lit/min hydrogen flow rate at a FIP of 1500 bar and a FIT of 17?bTDC. Thus, this study has shown the potential of higher FIP and FIT in improving the performance, combustion and emission of a hydrogen dual fuel engine with Jatropha biodiesel as pilot fuel.     

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.     

An experimental investigation on manifold‐injected hydrogen as a dual fuel for diesel engine system with different injection duration

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 (NO_X) 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.     

Combining GTL fuel,reformed EGR and HC-SCR aftertreatment system to reduce diesel NOx emissions. A statistical approach

An ultra-low sulphur diesel (ULSD) fuel and a synthetic gas-to-liquid (GTL) fuel, besides different types of standard and reformed EGR, were evaluated in a single-cylinder, direct injection, diesel engine equipped with hydrocarbon-selective catalytic reduction (HC-SCR) aftertreatment system. The results obtained were statistically analysed (at 95% statistical significance) to identify the most significant factors that affect NO_x emissions and to search for the optimum operation conditions in order to minimize these emissions. For that purpose, a fully crossed factorial experimental design was used, including two different engine speeds (1200 and 1500 rpm), two engine loads (25% and 50%), and four EGR/REGR ratios (0%, 10%, 20% and 30%) resulting in almost one hundred tests. An optimal combination of fuel type, REGR type and REGR ratio was proved to reduce around 89–95% of the reference NO_x emissions. In general, at 25% engine load GTL fuelling combined with the reformed EGR with the highest hydrogen content was found the most desirable, as the hydrogen sharply increased the NO_x conversion in the SCR catalyst. Differently, at 50% load standard EGR was sufficient to reach high NO_x reductions. These findings may be used for the implementation of a system on-board capable to switch from EGR to REGR, which will help engine manufacturers to meet the future emission regulations.     

Experimental investigation of the combustion characteristics,emissions and performance of hydrogen port fuel injection in a diesel engine

Diesel engines are indispensable in daily life. However, the limited supply of petroleum fuels and the stringent regulations on such fuels are forcing researchers to study the use of hydrogen as a fuel. In this study, a diesel engine is operated using hydrogen–diesel dual fuel, where hydrogen is introduced into the intake manifold using an LPG-CNG injector and pilot diesel is injected using diesel injectors. The energy contents of the total fuel, 0%, 16%, 36% and 46% hydrogen (the 0% hydrogen energy fraction represents neat diesel fuel), were tested at 1300 rpm of constant engine speed and 5.1 kW of constant indicated power. According to test results, the indicated thermal efficiency of the engine decreases and the isfc increases with an increasing hydrogen energy fraction. Additionally, indicated specific CO, CO₂ and smoke emissions decrease with an increasing percentage of hydrogen fuel. However, indicated specific NO_x emissions do not change at the 16% hydrogen energy fraction, in other words, with an increase in the hydrogen amount (36% and 46% hydrogen energy fraction of total fuel), a dramatic increase (58.8% and 159.7%, respectively) is observed. Additionally, the peak in-cylinder pressure and the peak heat release rate values increase with the increasing hydrogen rate.     

Effect of hydrogen supplementation on engine performance and emissions

Vehicular Pollution and environmental degradation are on the rise with increasing vehicles and to stop this strict regulation have been put on vehicular emissions. Also, the depleting fossil fuels are of great concern for energy security. This has motivated the researchers to invest considerable resources in finding cleaner burning, sustainable and renewable fuels. However renewable fuels independently are not sufficient to deal with the problem at hand due to supply constraints. Hence, advanced combustion technologies such as homogeneous charge compression ignition (HCCI), low-temperature combustion (LTC), and dual fuel engines are extensively researched upon. In this context, this work investigates dual fuel mode combustion using a constant speed diesel engine, operated using hydrogen and diesel. The engine is operated at 25, 50 and 75% loads and substitution of diesel energy with hydrogen energy is done as 0, 5, 10 and 20%. The effect of hydrogen energy share (HES) enhancement on engine performance and emissions is investigated. In the tested range, slightly detrimental effect of HES on brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) is observed. Comparision of NO and NO₂ emissions is done to understand the non-thermal influence of H₂ on the NO_x emissions. Hence, HES is found beneficial in reducing harmful emissions at low and mid loads.     

An experimental investigation on engine performance and emissions of a single cylinder diesel engine using hydrogen as inducted fuel and diesel as injected fuel with exhaust gas recirculation

Fast depletion of fossil fuels is demanding an urgent need to carry out research work to find out the viable alternative fuels for meeting sustainable energy demand with minimum environmental impact. In the future, our energy systems will need to be renewable and sustainable, efficient and cost-effective, convenient and safe. The technology for producing hydrogen from a variety of resources, including renewable, is evolving and that will make hydrogen energy system as cost-effective. Hydrogen safety concerns are not the cause for fear but they simply are different than those we are accustomed to with gasoline, diesel and other fossil fuels. For the time being full substitution of diesel with hydrogen is not convenient but use of hydrogen in a diesel engine in dual fuel mode is possible. So Hydrogen has been proposed as the perfect fuel for this future energy system. The experiment is conducted using diesel–hydrogen blend. A timed manifold induction system which is electronically controlled has been developed to deliver hydrogen on to the intake manifold. The solenoid valve is activated by the new technique of taking signal from the rocker arm of the engine instead of cam actuation mechanism. In the present investigation hydrogen-enriched air has been used in a diesel engine with hydrogen flow rate at 0.15 kg/h. As diesel is substituted and hydrogen is inducted, the NO_x emission is increased. In order to reduce NO_x emission an EGR system has been developed. In the EGR system a lightweight EGR cooler has been used instead of bulky heat exchanger. In this experiment performance parameters such as brake thermal efficiency, volumetric efficiency, BSEC are determined and emissions such as oxides of nitrogen, carbon dioxide, carbon monoxide, hydrocarbon, smoke and exhaust gas temperature are measured. Dual fuel operation with hydrogen induction coupled with exhaust gas recirculation results in lowered emission level and improved performance level compared to the case of neat diesel operation.     

Experimental investigation on a DI dual fuel engine with hydrogen injection

Over the past two decades considerable efforts have been undertaken to develop and introduce new alternative fuels for the conventional gasoline and diesel. Many alternative fuels, both liquid and gaseous, have been experimented and some have even been commercialized such as ethanol, natural gas, etc. Hydrogen has been considered as an excellent fuel to replace the petroleum‐based fuels due to its clean burning characteristics. In the present experimental investigation, hydrogen was injected in the intake manifold and diesel fuel was injected inside the engine cylinder in the conventional manner. Hydrogen injection parameters such as injection timing, injection duration and quantity of hydrogen injected were optimized based on the performance and emission characteristics. Exhaust gas recirculation (EGR) technique was adopted to reduce the oxides of nitrogen emission. From the results it was observed that for hydrogen diesel dual fuel (DF) engine, the optimal operating parameters for hydrogen injection were start of injection at gas exchange top dead centre with injection duration of 30° crank angle with the hydrogen flow rate of 7.5 litres per minute (lpm). With EGR the optimized condition was found to be 20% for the entire load. The brake thermal efficiency with 20% EGR increases by 16% at 75% load as compared with diesel, while at full load it reduces by 8% due to the recirculation of exhaust gases that results in a reduction of intake oxygen concentration compared with part load. NO_X emission decreases by five and half times, while other emissions increase by 1.4 times as compared with DF engine. Copyright © 2008 John Wiley & Sons, Ltd.     

A renewable pathway towards increased utilization of hydrogen in diesel engines

In the present work, dual fuel operation of a diesel engine has been experimentally investigated using biodiesel and hydrogen as the test fuels. Jatropha Curcas biodiesel is used as the pilot fuel, which is directly injected in the combustion chamber using conventional diesel injector. The main fuel (hydrogen) is injected in the intake manifold using a hydrogen injector and electronic control unit. In dual fuel mode, engine operations are studied at varying engine loads at the maximum pilot fuel substitution conditions. The engine performance parameters such as maximum pilot fuel substitution, brake thermal efficiency and brake specific energy consumption are investigated. On emission side, oxides of nitrogen, hydrocarbon, carbon monoxide and smoke emissions are analysed. Based on the results, it is found that biodiesel-hydrogen dual fuel engine could utilize up to 80.7% and 24.5% hydrogen (by energy share) at low and high loads respectively along with improved brake thermal efficiency. Furthermore, hydrocarbon, carbon monoxide and smoke emissions are significantly reduced compared to single fuel diesel engine operation. Exhaust gas recirculation (EGR) has also been studied with biodiesel-hydrogen dual fuel engine operations. It is found that EGR could improve the utilization of hydrogen in dual fuel engine, especially at the high loads. The effect of EGR is also found to reduce high nitrogen oxide emissions from the dual fuel engine and brake thermal efficiency is not significantly affected.     

The utilization of hydrogen in hydrogen/diesel dual fuel engine

A hydrogen fueled internal combustion engine has great advantages on exhaust emissions including carbon dioxide (CO₂) emission in comparison with a conventional engine fueling fossil fuel. In addition, if it is compared with a hydrogen fuel cell, the hydrogen engine has some advantages on price, power density, and required purity of hydrogen. Therefore, they expect that hydrogen will be utilized for several applications, especially for a combined heat and power (CHP) system which currently uses diesel or natural gas as a fuel.A final goal of this study is to develop combustion technologies of hydrogen in an internal combustion engine with high efficiency and clean emission. This study especially focuses on a diesel dual fuel (DDF) combustion technology. The DDF combustion technology uses two different fuels. One of them is diesel fuel, and the other one is hydrogen in this study. Because the DDF engine is not customized for hydrogen which has significant flammability, it is concerned that serious problems occur in the hydrogen DDF engine such as abnormal combustion, worse emission and thermal efficiency.In this study, a single cylinder diesel engine is used with gas injectors at an intake port to evaluate performance swung the hydrogen DDF engine with changing conditions of amount of hydrogen injected, engine speed, and engine loads. The engine experiments show that the hydrogen DDF operation could achieve higher thermal efficiency than a conventional diesel operation at relatively high engine load conditions. However, it is also shown that pre-ignition with relatively high input energy fraction of hydrogen occurred before diesel fuel injection and its ignition. Therefore, such abnormal combustion limited amount of hydrogen injected. Fire-deck temperature was measured to investigate causal relationship between fire-deck temperature and occurrence of pre-ignition with changing operative conditions of the hydrogen DDF engine.     

Effect of natural gas enrichment with hydrogen on combustion process and emission characteristic of a dual fuel diesel engine

The paper presents results of experimental research on a dual-fuel engine powered by diesel fuel and natural gas enriched with hydrogen. The authors attempted to replace CNG with hydrogen fuel as much as possible with a constant dose of diesel fuel of 10% of energy fraction. The tests were carried out for constant engine load of IMEP = 0.7 MPa and a rotational speed of n = 1500 rpm. The effect of hydrogen on combustion, heat release, combustion stability and exhaust emissions was analyzed. In the test engine, the limit of hydrogen energy fraction was 19%. The increase in the fraction caused an increase in the cycle-by-cycle variation and the occurrence of engine knocking. It was shown that the enrichment of CNG with hydrogen allows for the improvement in the combustion process compared to the co-combustion of diesel fuel with non-enriched CNG, where the reduction in the duration of combustion by 30% and shortening the time of achieving 50% of MFB by 50% were obtained. The evaluation of the spread of the end of combustion is also presented. For H₂ energetic share over 20%, the spread of end of combustion was 48° of crank angle. Measurement of exhaust emissions during the tests revealed an increase in THC and NO_x emissions.     

Performance and emission studies on port injection of hydrogen with varied flow rates with Diesel as an ignition source

Automobiles are one of the major sources of air pollution in the environment. In addition CO₂ emission, a product of complete combustion also has become a serious issue due to global warming effect. Hence the search for cleaner alternative fuels has become mandatory. Hydrogen is expected to be one of the most important fuels in the near future for solving the problems of air pollution and greenhouse gas problems (carbon dioxide), thereby protecting the environment. Hence in the present work, an experimental investigation has been carried out using hydrogen in the dual fuel mode in a Diesel engine system. In the study, a Diesel engine was converted into a dual fuel engine and hydrogen fuel was injected into the intake port while Diesel was injected directly inside the combustion chamber during the compression stroke. Diesel injected inside the combustion chamber will undergo combustion first which in-turn would ignite the hydrogen that will also assist the Diesel combustion. Using electronic control unit (ECU), the injection timings and injection durations were varied for hydrogen injection while for Diesel the injection timing was 23° crank angle (CA) before injection top dead centre (BITDC). Based on the performance, combustion and emission characteristics, the optimized injection timing was found to be 5° CA before gas exchange top dead centre (BGTDC) with injection duration of 30° CA for hydrogen Diesel dual fuel operation. The optimum hydrogen flow rate was found to be 7.5 lpm. Results indicate that the brake thermal efficiency in hydrogen Diesel dual fuel operation increases by 15% compared to Diesel fuel at 75% load. The NO_X emissions were higher by 1–2% in dual fuel operation at full load compared to Diesel. Smoke emissions are lower in the entire load spectra due to the absence of carbon in hydrogen fuel. The carbon monoxide (CO), carbon dioxide (CO₂) emissions were lesser in hydrogen Diesel dual fuel operation compared to Diesel. The use of hydrogen in the dual fuel mode in a Diesel engine improves the performance and reduces the exhaust emissions from the engine except for HC and NO_X emissions.