Performance and emission comparison of a supercharged dual-fuel engine fueled by producer gases with varying hydrogen content

This study investigated the effect of hydrogen content in producer gas on the performance and exhaust emissions of a supercharged producer gas–diesel dual-fuel engine. Two types of producer gases were used in this study, one with low hydrogen content (H₂ = 13.7%) and the other with high hydrogen content (H₂ = 20%). The engine was tested for use as a co-generation engine, so power output while maintaining a reasonable thermal efficiency was important. Experiments were carried out at a constant injection pressure and injection quantity for different fuel–air equivalence ratios and at various injection timings. The experimental strategy was to optimize the injection timing to maximize engine power at different fuel–air equivalence ratios without knocking and within the limit of the maximum cylinder pressure. Two-stage combustion was obtained; this is an indicator of maximum power output conditions and a precursor of knocking combustion. Better combustion, engine performance, and exhaust emissions (except NO_x) were obtained with the high H₂-content producer gas than with the low H₂-content producer gas, especially under leaner conditions. Moreover, a broader window of fuel–air equivalence ratio was found with highest thermal efficiencies for the high H₂-content producer gas.     

An experimental investigation on engine performance and emissions of a supercharged H2-diesel dual-fuel engine

This study investigated the engine performance and emissions of a supercharged engine fueled by hydrogen and ignited by a pilot amount of diesel fuel in dual-fuel mode. The engine was tested for use as a cogeneration engine, so power output while maintaining a reasonable thermal efficiency was important. Experiments were carried out at a constant pilot injection pressure and pilot quantity for different fuel-air equivalence ratios and at various injection timings without and with charge dilution. The experimental strategy was to optimize the injection timing to maximize engine power at different fuel-air equivalence ratios without knocking and within the limit of the maximum cylinder pressure. The engine was tested first with hydrogen-operation condition up to the maximum possible fuel-air equivalence ratio of 0.3. A maximum IMEP of 908 kPa and a thermal efficiency of about 42% were obtained. Equivalence ratio could not be further increased due to knocking of the engine. The emission of CO was only about 5 ppm, and that of HC was about 15 ppm. However, the NOx emissions were high, 100–200 ppm or more. The charge dilution by N₂ was then performed to obtain lower NOx emissions. The 100% reduction of NOx was achieved. Due to the dilution by N₂ gas, higher amount of energy could be supplied from hydrogen without knocking, and about 13% higher IMEP was produced than without charge dilution.     

Performance and emissions of a supercharged dual-fuel engine fueled by hydrogen-rich coke oven gas

This study investigated the engine performance and emissions of a supercharged dual-fuel engine fueled by hydrogen-rich coke oven gas and ignited by a pilot amount of diesel fuel. The engine was tested for use as a cogeneration engine, so power output while maintaining a reasonable thermal efficiency was important. Experiments were carried out at a constant pilot injection pressure and pilot quantity for different fuel-air equivalence ratios and at various injection timings without and with exhaust gas recirculation (EGR). The experimental strategy was to optimize the injection timing to maximize engine power at different fuel-air equivalence ratios without knocking and within the limit of the maximum cylinder pressure. The engine was tested first without EGR condition up to the maximum possible fuel-air equivalence ratio of 0.65. A maximum indicated mean effective pressure (IMEP) of 1425 kPa and a thermal efficiency of 39% were obtained. However, the nitrogen oxides (NOx) emissions were high. A simulated EGR up to 50% was then performed to obtain lower NOx emissions. The maximum reduction of NOx was 60% or more maintaining the similar levels of IMEP and thermal efficiency. Two-stage combustion was obtained; this is an indicator of maximum power output conditions and a precursor of knocking combustion.     

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.     

Hydrogen dual-fuelling of compression ignition engines with emulsified biodiesel as pilot fuel

Dual-fuel compression ignition (CI) engine operation with hydrogen is a promising method of using hydrogen gas in CI engines via high-cetane pilot fuel ignition. However, hydrogen dual-fuel operation with neat pilot fuels typically produce: high NO_x emissions; and high combustion chamber pressure rise rates (leading to increased “Diesel knock” tendencies). While water-in-fuel emulsions have been used during normal CI engine operation to cool the charge and slow combustion rates in an effort to reduce NO_x emissions, these water-in-fuel emulsions have not been tested as pilot fuels during hydrogen dual-fuel combustion. In this work two water-in-biodiesel emulsions are tested as pilot fuels during hydrogen dual-fuel operation. Hydrogen dual-fuel operation generally produces at best comparable thermal efficiencies compared with normal CI engine operation, while the emulsified biodiesel pilot fuels generally increase thermal efficiencies when compared with the neat biodiesel pilot fuel during dual-fuel operation. There is also a clear reduction in NO_x emissions with emulsified pilot fuel use compared with the neat pilot fuel. The thermal efficiency increase is more apparent at higher engine speeds, while the NO_x reduction is more apparent at lower speeds. This is due to two conflicting effects (exclusive to emulsified pilot fuel) that occur in tandem. The first is the cooling effect of water vapourisation on the charge, while the second is the microexplosion phenomenon which enhances fuel-air mixing. The NO_x emission reduction is due to the emulsified pilot fuel lowering pressure rise rates compared with the neat pilot fuel, while the efficiency increase is due to a more homogeneous charge resulting from the violent microexplosion of the emulsified pilot fuel. Smoke, CO, HC and CO₂ emissions remain comparable to neat pilot fuel tests. Overall, emulsified pilot fuels can reduce NO_x emissions and increase thermal efficiencies, however not at the same instance and under different operating conditions. The general trends of reduced power output, reduced CO₂ and increased water vapour emission during hydrogen dual-fuel operation (with neat pilot fuels) are also maintained.     

Performance and emission characteristics of turpentine–diesel dual fuel engine and knock suppression using water diluents

In the present work, a normal diesel engine was modified to work in a dual fuel (DF) mode with turpentine and diesel as primary and pilot fuels, respectively. The resulting homogeneous mixture was compressed to a temperature below the self‐ignition point. The pilot fuel was injected through the standard injection system and initiated the combustion in the primary‐fuel air mixture. The primary fuel (turpentine) has supplied most of the heat energy. Usually, in all DF engines, low‐cetane fuels are preferred as a primary fuel. Therefore, at higher loads these fuels start knocking and deteriorating in performances. Usually, DF operators suppress the knock by adding more pilot‐fuel quantity. But in the present work, a minimum pilot‐fuel quantity was maintained constant throughout the test and a required quantity of diluent (water) was added into the combustion at the time of knocking. The advantages of this method of knock suppression are restoration of performance at full load, maintenance of the same pilot quantity through the load range and reduction in the fuel consumption at full load. From the results, it was found that all performance and emission parameters of turpentine, except volumetric efficiency, are better than those of diesel fuel. The emissions like CO, UBHC are higher than those of the diesel baseline (DBL) and around 40–45% reduction of smoke was observed at 100% of full load. The major pollutant of diesel engine, NO_x, was found to be equal to that of DBL. From the above experiment, it was proved that approximately 80% replacement of diesel with turpentine is quite possible. Copyright © 2006 John Wiley & Sons, Ltd.     

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.     

Effect of choice of pilot fuel on the performance of natural gas in diesel engines

Energy conversion alone is inadequate to satisfy long-term energy demands and to gain independence from petroleum-based fuels. It is, therefore, of great importance that all potential fuel alternatives be recognised and examined. Natural gas and bio-liquids may provide such alternatives and their potential has been examined (Nwafor and Rice, WREC 1994;2:841). Fossil fuel combustion is the main culprit in environmental pollution, whilst the impacts of vegetable oil fuel systems are on the whole less adverse and more localised than those of fossil fuels. This paper investigates the possibility of substituting a plant fuel pilot injection for diesel fuel for combustion of natural gas in a diesel engine. The pilot fuels used are rape methyl ester (RME) and neat rapeseed oil. The test results indicate that engine performance on these alternative pilot fuels was satisfactory and compared favourably with the baseline test result on diesel fuel.     

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.     

Experimental investigation on biogas enrichment with hydrogen for improving the combustion in diesel engine operating under dual fuel mode

Biogas valorization as fuel for internal combustion engines is one of the alternative fuels, which could be an interesting way to cope the fossil fuel depletion and the current environmental degradation. In this circumstance, an experimental investigation is achieved on a single cylinder DI diesel engine running under dual fuel mode with a focus on the improvement of biogas/diesel fuel combustion by hydrogen enrichment. In the present investigation, the mixture of biogas, containing 70% CH₄ and 30% CO₂, is blended with the desired amount of H₂ (up to 10, 15 and 20% by volume) by using MTI 200 analytical instrument gas chromatograph, which flow thereafter towards the engine intake manifold and mix with the intake air. Depending on engine load conditions, the volumetric composition of the inducted gaseous fraction is 20–50% biogas, 2–10% H₂ and 45–78% air. Near the end of the compression stroke, a small amount of diesel pilot fuel is injected to initiate the combustion of the gas–air mixture. Firstly, the engine was tested on conventional diesel mode (baseline case) and then under dual fuel mode using the biogas. Consequently, hydrogen has partially enriched the biogas. Combustion characteristics, performance parameters and pollutant emissions were investigated in-depth and compared. The results have shown that biogas enriched with 20% H₂ leads to 20% decrease of methane content in the overall exhaust emissions, associated with an improvement in engine performance. The emission levels of unburned hydrocarbon (UHC) and carbon monoxide (CO) are decreased up to 25% and 30% respectively. When the equivalence ratio is increased, a supplement decrease in UHC and CO emissions is achieved up to 28% and 30% respectively when loading the engine at 60%.     

Investigations on operation of CI engine using producer gas and rice bran oil in mixed fuel mode

A naturally aspirated multi cylinder diesel genset (DG) was operated successfully with mixed fuels (fossil-diesel (FD), refined rice bran oil (RRBO) and producer gas from a wood gasifier). Performance of DG set in FD, dual fuel mode (FD+RRBO in different proportion and FD+producer gas) and mixed fuels mode (with preheated blend of 75% RRBO+FD and producer gas) at different engine load conditions are presented in this paper. Performance of DG was evaluated in terms of specific energy consumption (SEC), brake thermal efficiency, exhaust gas temperature and exhaust gas composition. Study revealed that blends containing up to 75% RRBO with FD could be used as engine fuel without any adverse effect on the engine. The blend of RRBO and FD was preheated to 60 °C before use in the compression ignition (CI) engine. In general, exhaust gas temperature and SEC increased in all the three modes compared to FD. However, break thermal efficiency decreased. It may be due to lower calorific value of RRBO and producer gas.It was observed that at 84% engine load having 18.4:1 compression ratio (CR) and operating in dual fuel mode (FD+producer gas), the concentration of pollutants like carbon monoxide (CO), carbon dioxide (CO₂), nitric oxide (NO), nitrogen dioxide (NO₂) reduced by 55%, 19.7%, 82% and 83%, respectively, while hydrocarbon (HC) increased by 67.2% as compared to FD. Similarly at 84% engine load having 17:1 CR and operating in dual fuel mode (FD+RRBO), the concentration of pollutant like CO, CO₂ and HC reduced by 60%, 0.86% and 91%, respectively. However, NO_x increased by 23.48% as compared to FD.In mixed fuel mode (preheated blends of RRBO+FD in the proportion of 3:1 and producer gas) at 84% engine load having 18.4:1 CR, the concentration of pollutants like HC, NO and NO₂ reduced by 48.28%, 61.57% and 80.48%, respectively, while CO increased by 16.31% as compared to FD. In addition to the findings on environmental aspects, the study also proved that the diesel engine could be run safely in mixed fuel mode (53% producer gas, rest RRBO and FD at the ratio of 3:1 and heated at 60 °C).     

Combustion,performance and emission analyses of a CI engine operating with renewable diesel fuels (HVO/FARNESANE) under dual-fuel mode through hydrogen port injection

The use of hydrogen in internal combustion engines is pointed out as an alternative to reduce greenhouse gas emissions. In applications that require high levels of torque and low engine speeds, compression ignition (CI) engines are more appropriate. However, because of the high auto-ignition temperature of hydrogen, its use in these engine types is more suitable when the dual-fuel concept is applied. This study comprehensively investigates, through experimental techniques, the use of hydrogen port-injection in a four-stroke single-cylinder CI engine operating with the renewable diesel-like fuels hydrotreated vegetable oil (HVO) and farnesane, in comparison to fossil diesel dual-fuel operation. In this sense, the present work aims to fill a gap in the literature by performing a novel analysis of dual-fuel operation with hydrogen, considering different substitution fractions, and using groundbreaking biofuels, such as HVO and farnesane. The results showed that in-cylinder pressure and temperature were increased with H₂ enrichment for every pilot fuel, but green diesel fuels presented lower values than those for diesel operation. Furthermore, hydrogen port injection slightly delayed the start of combustion and increased the ignition delay, but a reduction in both premixed and diffusion combustion duration was observed. Reductions in PM, CO, and CO₂ emissions were reported during H₂ addition for every pilot fuel, while increased NO_x was observed. Despite this increase, both HVO and farnesane decreased the emissions of this pollutant in single and dual-fuel operations, compared with fossil diesel. In addition, both renewable diesel fuels presented higher BTE than diesel for every studied H₂ mass flow.     

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’.     

Use of hydrogen in dual-fuel diesel engines

Hydrogen is a promising future energy carrier due to its potential for production from renewable resources. It can be used in existing compression ignition diesel engines in a dual-fuel mode with little modification. Hydrogen's unique physiochemical properties, such as higher calorific value, flame speed, and diffusivity in air, can effectively improve the performance and combustion characteristics of diesel engines. As a carbon-free fuel, hydrogen can also mitigate harmful emissions from diesel engines, including carbon monoxide, unburned hydrocarbons, particulate matter, soot, and smoke. However, hydrogen-fueled diesel engines suffer from knocking combustion and higher nitrogen oxide emissions. This paper comprehensively reviews the effects of hydrogen or hydrogen-containing gaseous fuels (i.e., syngas and hydroxy gas) on the behavior of dual-fuel diesel engines. The opportunities and limitations of using hydrogen in diesel engines are discussed thoroughly. It is not possible for hydrogen to improve all the performance indicators and exhaust emissions of diesel engines simultaneously. However, reformulating pilot fuel by additives, blending hydrogen with other gaseous fuels, adjusting engine parameters, optimizing operating conditions, modifying engine structure, using hydroxy gas, and employing exhaust gas catalysts could pave the way for realizing safe, efficient, and economical hydrogen-fueled diesel engines. Future work should focus on preventing knocking combustion and nitrogen oxide emissions in hydrogen-fueled diesel engines by adjusting the hydrogen inclusion rate in real time.     

Effect of equivalence ratio on knocking tendency in spark ignition engines fueled with fuel blends of biogas,natural gas,propane and hydrogen

This research evaluates the effect of the equivalence ratio on knocking tendency in two Spark Ignition (SI) engines fueled with gaseous fuels. A Lister Petter TR2 Diesel engine (TR2) converted to SI was used to evaluate the equivalence ratio effect when the engine was fueled with fuel blends of biogas, natural gas, propane, and hydrogen. A Cooperative Fuel Research (CFR) engine was used to study the effect of equivalence ratio on the Critical Compression Ratio (CCR) which is a metric to evaluate the knocking tendency of gaseous fuels. In both engines, the tests were conducted using the knocking threshold as the engine limit operation to quantify the effect of the equivalence ratio on knocking tendency. Experimental results in the CFR engine revealed that a lean mixture reduces the knocking tendency allowing to operate the CFR engine at higher CCR. In contrast, the effect of the equivalence ratio on the knocking tendency in the TR2 engine was different since leaner mixtures increased the engine knocking tendency. This tendency was caused by the increase in the % throttle which increased the mixture pressure at the end of the compression stroke. The high knocking tendency to lean mixtures forces to reduce the output power to find the knocking threshold for all fuel blends.     

Emission from utilization of producer gas and mixes of jatropha biodiesel

This paper reports about the discharge characteristics of jatropha biodiesel blends along with producer gas from waste babul wood pieces in a dual-fuel direct injection diesel engine. The biodiesel blends were examined in both individual and dual-fuel modes at a constant gas flow rate of 21.69 kg/h at all loading conditions. From the results it may be concluded that oxides of nitrogen and smoke opacity reduce, whereas carbon dioxide (CO₂), carbon monoxide (CO), and hydrocarbon (HC) increase for all test fuels in dual-fuel operation compared with that of a single style at different loading conditions. The fuel blends show better emissions than that of diesel in both the ways.     

Insight into fuel reactivity effects on thermochemical fuel reforming (TFR)

This study uses a port-injection spark-ignition four-cylinder natural gas engine to achieve TFR (Thermochemical fuel reforming) mode. To study the effects of fuel reactivity on combustion, reforming process, emissions and fuel economy, chemicals including n-heptane, PRF50 and isooctane are respectively used as enriched fuel. The results show that the higher the reactivity of the enriched fuel, the better the combustion and cycle stability of the reforming cylinder. However, n-heptane enrichment with high reactivity has the problem of knocking at large equivalence ratio. The enrichment limit of PRF50 is the highest, which combines the properties of n-heptane and isooctane. The H₂ production abilities of three enriched fuels are similar, but that of isooctane is slightly lower under large equivalence ratios. In terms of fuel economy, the three perform similarly at small equivalence ratios. Whereas it’s lower with isooctane enrichment at large equivalence ratios, which is at the expense of increased NOx emission.     

Analysis of CRDI diesel engine characteristics operated on dual fuel mode fueled with biodiesel-hydrogen enriched producer gas under the single and multi-injection scheme

The present work aims to investigate the consequences of pilot fuel (PF) multiple injections and hydrogen manifold injection (HMI) on the combustion and tailpipe gas characteristics of a common rail direct injection (CRDI) compression ignition (CI) engine operated on dual fuel (DF) mode. The CI engine can perform on a wide variety of fuels and under high pilot fuel (PF) pressure. Pilot fuel injection (PFI) is achieved at TDC, 5, 10, and 15ºCA before the top dead center (bTDC), and divided injection consists of injecting fuel in three different magnitudes on a time basis and PF is injected into the engine cylinder at a pressure of 600 bar. In this work, the hydrogen flow rate (HFR) was fixed at 8 lpm constant and producer gas was inducted without any restriction. The investigational engine setup has the ability to deliver a PF and hydrogen (H₂) precisely in all operating circumstances using a separate electronic control unit (ECU). Results showed that diesel-hydrogen enriched producer gas (HPG) operation at maximum operating conditions provided amplified thermal efficiency by 4.01% with reduced emissions, except NOx levels, compared to biodiesel-HPG operation. Further, DiSOME with the multi-injection strategy of 60 + 20+20 and 50 + 25+25, lowered thermal efficiency by 4.8% and 9.12%, respectively compared to identical fuel combinations under a single injection scheme. However, reductions in NOx levels, cylinder pressure, and HRR were observed with a multi-injection scheme. It is concluded that multi-injection results in lower BTE, changes carbon-based emissions marginally, and decreases cylinder pressure and heat release rate than the traditional fuel injection method.     

Improving the performance of dual fuel engines running on natural gas/LPG by using pilot fuel derived from jojoba seeds

The use of jojoba methyl ester as a pilot fuel was investigated for almost the first time as a way to improve the performance of dual fuel engine running on natural gas or liquefied petroleum gas (LPG) at part load. The dual fuel engine used was Ricardo E6 variable compression diesel engine and it used either compressed natural gas (CNG) or LPG as the main fuel and jojoba methyl ester as a pilot fuel. Diesel fuel was used as a reference fuel for the dual fuel engine results. During the experimental tests, the following have been measured: engine efficiency in terms of specific fuel consumption, brake power output, combustion noise in terms of maximum pressure rise rate and maximum pressure, exhaust emissions in terms of carbon monoxide and hydrocarbons, knocking limits in terms of maximum torque at onset of knocking, and cyclic variability data of 100 engine cycles in terms of maximum pressure and its pressure rise rate average and standard deviation. The tests examined the following engine parameters: gaseous fuel type, engine speed and load, pilot fuel injection timing, pilot fuel mass and compression ratio. Results showed that using the jojoba fuel with its improved properties has improved the dual fuel engine performance, reduced the combustion noise, extended knocking limits and reduced the cyclic variability of the combustion.     

An experimental investigation of incomplete combustion of gaseous fuels of a heavy-duty diesel engine supplemented with hydrogen and natural gas

This paper investigates the emissions of the unburned gaseous fuels of a heavy-duty diesel engine converted to operate under natural gas (NG)-diesel and hydrogen (H₂)-diesel dual fuel combustion mode. The detailed effects of the addition of H₂, NG, engine load, and engine speed on the exhaust emissions of the unburned H₂, methane (CH₄), and carbon monoxide (CO) were experimentally investigated. The combustion efficiencies of CH₄ and H₂ supplemented were also examined and compared.