Performance and emission studies of direct injection C.I. engine in duel fuel mode (hydrogen-diesel) with EGR

Presently majority of the world’s energy demand is met by fossil fuels. These fuels are depleting at an alarming rate. Thus in future, our energy systems will need to be renewable and sustainable, efficient and cost-effective, convenient and safe. Among the various alternative fuels, hydrogen is a long-term renewable and least polluting fuel (produced from renewable energy sources). Its clean burning characteristics help to meet the stringent emission norms. Majority of the work using hydrogen as a fuel is being done in spark ignition engine, however, in this experimental investigation efforts have been made to utilize it in compression ignition engine.     

Thermodynamic analysis of combustion and pollutants formation in a wood-gas spark-ignited heavy-duty engine

Awareness of limitations of petroleum based liquid fuels as for example used in spark-ignited heavy-duty engines for power generation, has led engineers to propose various solutions such as the use of alternative/renewable energy sources. Wood-gas is an alternative gaseous fuel generated from the gasification of wood, which could be used as a full supplement fuel in conventional heavy-duty spark-ignited engines fuelled with natural gas. Previous related research studies have shown that the main disadvantage of the wood-gas combustion is its negative impact on brake engine efficiency compared to the normal natural gas operation, while NO and CO emissions are also increased. Compression ratio and spark timing are some of the engine parameters, which influence significantly the combustion mechanism inside the combustion chamber of a wood-gas powered spark-ignited engine. In order to examine the effect of these parameters on the performance and exhaust emissions of a heavy-duty, turbocharged, spark-ignited engine fuelled with wood-gas, a theoretical investigation is conducted in this work by using a numerical simulation. The results concern engine performance characteristics, NO and CO emissions for various engine operating conditions (i.e. air to fuel excess ratios), by using a comprehensive two-zone phenomenological model. The predictive ability of the thermodynamic model was tested against experimental measurements, which were obtained from the operation of a multi-cylinder, four-stroke, turbocharged, spark-ignited engine fuelled with wood-gas fuel at various loads. The experimental results are found to be in good agreement with the respective computed ones obtained from the simulation model. The main objective of the comparative assessment shown in the present work is to record and comparatively evaluate the relative impact of each one of the above mentioned parameters (compression ratio and spark timing) on the engine performance characteristics and emitted pollutants. Furthermore, an effort is made to determine the optimum combinations between these parameters, since at high engine load conditions their simultaneous increase may lead in undesirable results concerning the engine performance characteristics. The conclusions from the present investigation are valuable for the use of wood-gas as a full supplement energy source in conventional, natural gas fuelled, heavy-duty, spark-ignited engines used for electric power generation.     

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.     

Parallel induction: a simple fuel control method for hydrogen engines

A simple, low-pressure fuel control system for hydrogen engines is explained. Data are provided showing the performance of the system on two hydrogen engines, a Mitsubishi 2.4-1, spark-ignition engine in a bus and a Caterpillar 7-l. diesel from a mining vehicle converted to spark ignition. Both engines were turbocharged with aftercooling and utilize excess combustion air to limit NO_x emissions.     

Modelling of combustion process in a spark ignited hydrogen engine

This paper reports the relative merits of the Eddy Entrainment model over the Reynolds Parameter model in describing the combustion process in a spark ignition engine using hydrogen as fuel. The relative performance of each model is analysed with reference to the experimental data obtained from a single-cylinder engine. From the present investigation and in comparison of the performance of these models with other fuels it is found that both the models are capable of satisfactorily predicting the performance of hydrogen fuel engines due to (a) higher laminar flame speeds and (b) small quench distance.     

Analysis of the effects of reformate (hydrogen/carbon monoxide) as an assistive fuel on the performance and emissions of used canola-oil biodiesel

Evolving technology and a reoccurring energy crisis creates a continued investigation into the search for sustainable and clean-burning renewable fuels. One possibility is hydrogen that has many desirable qualities such as a low flammability limit promoting ultra-lean combustion, high laminar flame speed for increased thermal efficiency and low emissions. However, past research discovered certain limiting factors in its use such as pre-ignition in spark ignition engines and inability to work as a singular fuel in compression ignition engines. To offset these issues, this work documents manifold injection of a hydrogen/carbon monoxide mixture in a dual-fuel methodology with biodiesel. While carbon monoxide does degrade some of the desirable properties of hydrogen, it acts partially like a diluent to restrict pre-ignition. The result of this mixture addition allows the engine to maintain power while reducing biodiesel fuel consumption with a minimal NO_x emissions increase.     

A review of hydrogen as a compression ignition engine fuel

Diesel fuelled engines emit higher levels of carbon dioxide and other harmful air pollutants (such as noxious gases and particulates) per litre of fuel than gasoline engines. This fact, combined with the recent diesel emission scandal and the rumours of more widespread cheating by automotive manufacturers have initiated a long discussion about the future and sustainability of diesel engines.Improving the compression ignition engine is a direct way of going green. Reducing the harmful emissions can be achieved by future developments in the engine technology but also the implementation of alternative fuels. Hydrogen is a renewable, high-efficient and clean fuel that can potentially save the future of diesel-type engines. The evolution of high-efficiency renewable hydrogen production methods is the most important path for the start of a new hydrogen era for the compression ignition engine that can improve its sustainability and maximum efficiency.This paper provides a detailed overview of hydrogen as a fuel for compression ignition engines. A comprehensive review of the past and recent research activities on the topic is documented. The review focuses on the in-cylinder combustion of hydrogen either as a primary fuel or in dual fuel operation. The effects of injection strategies, compression ratio and exhaust gas recirculation on the combustion and emission characteristics of the hydrogen fuelled engine are fully analysed. The main limitations, challenges and perspectives are presented.     

Experimental investigation of varying composition of HCNG on performance and combustion characteristics of a SI engine

With rapid depletion of petroleum resources, researchers are investigating alternate fuels to meet global transportation energy demand. Gaseous fuels such as compressed natural gas (CNG) and hydrogen are of special interest because of their cleaner combustion characteristics compared to liquid petroleum based fossil fuels. However both these gaseous fuels have some technical issues when they are used as stand-alone alternate fuel in conventional spark ignition (SI) engines. CNG suffers from lower energy density and narrow flammability range whereas backfiring tendency is highly pronounced in hydrogen fueled engines. Hydrogen enriched compressed natural gas (HCNG) mixtures are observed to be good alternative to these individual fuels since these mixtures do not pose the issues experienced by the constituent fuels i.e. CNG and hydrogen. In this study, experiments were conducted in a spark ignited gas engine using various compositions of HCNG mixtures having 0, 10, 20, 30, 50, 70 and 100% (v/v) hydrogen fraction. The performance and combustion characteristics of these test fuels were compared with that of baseline CNG, in order to find an optimum HCNG mixture composition for a single cylinder gas engine. Results obtained showed that 30HCNG mixture delivered superior engine performance compared to other HCNG mixtures and baseline CNG, which is in sharp contrast to 15HCNG being advocated globally.     

Experimental investigation of performance and emissions of the SICAI-hybrid engine systems

The use of hybrid electrical engines can provide more efficiency by reducing fuel consumption and emissions. In the research, the experimental studies on the created hybrid electric engine were presented. The hybrid engine combines an electric motor with the internal combustion engine (ICE) which is operated under spark assisted controlled auto-ignition (SICAI) combustion mode with the alternative fuels consisting of different ratios of methane–hydrogen blends. In order to establish the hybrid engine, firstly, efficiency graphs of the electrical motor were obtained experimentally. The battery charge status was also checked. The operating range of the SICAI engine in the hybrid system was identified considering performance and efficiency parameters. Based on these parameters, a hybrid algorithm was established to control the operating of the created hybrid engine system. Thus, the experimental studies were carried out for 100% methane, 90% methane-10% hydrogen, 80% methane-20% hydrogen and, 70% methane-30% hydrogen blends (by volume) at wide opening throttle (WOT) and, 50% WOT positions. Consequently, the results were discussed in terms of efficiency and emissions.     

Hydrogen addition to tea seed oil biodiesel: Performance and emission characteristics

Compression ignition engines are the dominant tools of the modern human life especially in the field of transportation. But, the increasing problematic issues such as decreasing reserves and environmental effects of diesel fuels which is the energy source of compression ignition engines forcing researchers to investigate alternative fuels for substitution or decreasing the dependency on fossil fuels. The mostly known alternative fuel is biodiesel fuel and many researchers are investigating the possible raw materials for biodiesel production. Also, hydrogen fuel is an alternative fuel which can be used in compression ignition engines for decreasing fuel consumption and hazardous exhaust emissions by enriching the fuel. In this study, influences of hydrogen enrichment to diesel and diesel tea seed oil biodiesel blends (B10 and B20) were investigated on an unmodified compression ignition engine experimentally. In consequence of the experiments, lower torque and higher brake specific fuel consumption data were measured when the engine was fuelled diesel biodiesel blends (B10 and B20) instead of diesel fuel. Also, diesel biodiesel blends increased CO₂ and NO_x emissions while decreasing the CO emissions. Hydrogen enrichment (5 l/m and 10 l/m) was improved the both torque and brake specific fuel consumption for all test fuels. Furthermore, hydrogen enrichment reduced CO and CO₂ emissions due to absence of carbon atoms in the chemical structure for all test fuels. Increasing flow rate of hydrogen fuel from 5 l/m to 10 l/m further improved performance measures and emitted harmful gases except NO_x. The most significant drawback of the hydrogen enrichment was the increased NO_x emissions.     

Effect of different volume fractions of ammonia on the combustion and emission characteristics of the hydrogen-fueled engine

Hydrogen internal combustion engines (ICE) will play an important role in reducing carbon emissions, but low power density and abnormal combustion problems are the main obstacles restricting the promotion of hydrogen ICE. Ammonia is a low-reactivity renewable fuel. The purpose of this study is to study the effect of different ammonia-added volume fractions on hydrogen ICE. In this experimental study, the combustion and emission characteristics of an engine fueled by a hydrogen/ammonia mixture were evaluated at part-load operating conditions. The experiment was carried out on a modified engine, the engine speed was 1300 rpm, the absolute pressure of the manifold was 61 kPa, and the volume fraction of ammonia added was 5.2%, 7.96%, and 10.68%, respectively. The test results show that the addition of ammonia changes the combustion characteristics of hydrogen. As the volume fraction of ammonia added increases, the flame development period and flame propagation period are both prolonged, and the peak heat release rate decreases. The addition of ammonia increases the power of the engine and reduces the indicated thermal efficiency. At the ignition timing of the maximum braking torque, as the volume fraction of ammonia added increases, the indicated mean effective pressure and indicated thermal efficiency increase. Adding ammonia volume fraction has little effect on Nitrogen oxides (NOx) emissions, and NOx emissions gradually increase with the delay of ignition timing.     

Analysis of ignition delay period of a dual fuel diesel engine with hydrogen and LPG as secondary fuels

In this study, experiments were performed on 4 cylinder turbocharged, intercooled with 62.5 kW gen-set diesel engine by using hydrogen, liquefied petroleum gas (LPG) and mixture of LPG and hydrogen as secondary fuels. The experiments were performed to measure ignition delay period at different load conditions and various diesel substitutions. The experimental results have been compared with ignition delay correlation laid down by other researchers for diesel and dual fuel diesel engine. It is found that ignition delay equation based on pressure, temperature and oxygen concentration for a dual fuel diesel engine run on diesel-biogas gives variation up to 6.56% and 14.6% from the present experimental results, while ignition delay equation for a pure diesel engine gives 7.55% and 33.3% variation at lower and higher gaseous fuel concentrations, respectively. It is observed that the ignition delay of dual fuel engine depends not only on the type of gaseous fuels and their concentrations but also on charge temperature, pressure and oxygen concentration.     

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 hydrogen addition on combustion and emissions performance of a spark-ignited ethanol engine at idle and stoichiometric conditions

Regarding the limited fossil fuel reserves, the renewable ethanol has been considered as one of the substitutional fuels for spark ignition (SI) engines. But due to its high latent heat, ethanol is usually hard to be well evaporated to form the homogeneous fuel–air mixture at low temperatures, e.g., at idle condition. Compared with ethanol, hydrogen possesses many unique combustion and physicochemical properties that help improve combustion process. In this paper, the performance of a hydrogen-enriched SI ethanol engine under idle and stoichiometric conditions was investigated. The experiment was performed on a modified 1.6 L SI engine equipped with a hydrogen port-injection system. The ethanol was injected into the intake ports using the original engine gasoline injection system. A self-developed hybrid electronic control unit (HECU) was adopted to govern the opening and closing of hydrogen and ethanol injectors. The spark timing and idle bypass valve opening were governed by the engine original electronic control unit (OECU), so that the engine could operate under its original target idle speed for each testing point. The engine was first fueled with the pure ethanol and then hydrogen volume fraction in the total intake gas was gradually increased through increasing hydrogen injection duration. For a specified hydrogen addition level, ethanol flow rate was reduced to keep the hydrogen–ethanol–air mixture at stoichiometric condition. The test results showed that hydrogen addition was effective on reducing cyclic variations and improving indicated thermal efficiency of an ethanol engine at idle. The fuel energy flow rate was reduced by 20% when hydrogen volume fraction in the intake rose from 0% to 6.38%. Both flame development and propagation periods were shortened with the increase of hydrogen blending ratio. The heat transfer to the coolant was decreased and the degree of constant volume combustion was enhanced after hydrogen addition. HC and CO emissions were first reduced and then increased with the increase of hydrogen blending fraction. The acetaldehyde emission from the hydrogen-enriched ethanol engine is lower than that from the pure ethanol engine. However, the addition of hydrogen tended to increase NO_x emissions from the ethanol engine at idle and stoichiometric conditions.     

Experimental study of the effect of fuel types on the performance of spark ignition engine

Different fuels are being used daily in the city of Kirkuk, Iraq for operating vehicles with spark-ignition internal combustion engines. Aiming to address the effects of these fuels on both engines and the environment, this work conducts an experimental study where a single-cylinder, four-stroke small spark ignition engine is employed. Three types of benzene with different octane ratings (low with an additive [85.8%], medium [89.2%], and high [95.6%]) are utilized in the study as they are the most consumed fuel in the area of the study. Moreover, the low-octane fuel will be addressed with a commercial additive. In addition to engine performance, the exhaust gases and sound levels are analyzed as well. Through the outcomes, it is observed that the fuel with higher octane numbers relatively produces better engine performance and pollution. At normal engine speed, the fuel with a medium octane rating, however, has close engine performance results but with worse pollution effects. On the other hand, the engine fails to start with low-octane fuel without the additive. The additive improves the engine performance with the low octane fuel and surprisingly produces fewer pollution gases than the fuel with medium octane number. However, the engine still behaves worse than with the other fuels at normal engine speed.     

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.     

Fuel conversion efficiency of a port injection engine fueled with gasoline–isobutanol blends

This paper describes the comparative advantages of using isobutanol as a fuel for SI (spark ignition) engines instead of ethanol. An experimental study of fuel conversion efficiency was performed on a port injection engine fueled with mixtures containing 10, 30 and 50% isobutanol blended with gasoline. Efficiency as well as performance levels were maintained within acceptable limits for all three types of fuel blends compared to running the engine on straight gasoline. These results show that isobutanol is an attractive drop-in fuel for SI engines, and can be blended with gasoline in much higher concentrations compared to ethanol, without any modifications to the fuel system or other engine components.     

Effect of water blending on bioethanol HCCI combustion with forced induction and residual gas trapping

There is increased interest worldwide in renewable engine fuels as well as in new combustion technologies. Bioethanol is one of the alternative fuels that have been used successfully in spark ignition engines. A combustion technology that currently attracts a lot of interest is the homogeneous charge compression ignition (HCCI) combustion, which has shown potential for low nitrogen oxides emissions with no particulate matter formation. The authors have shown previously that applying forced induction to bioethanol HCCI with residual gas trapping results in an extended load range compared to naturally aspirated operation. However, at high boost pressures, high cylinder pressure rise rates develop. Work by other researchers has shown that direct injection of water can be used as a combustion control method. The present work explores water blending as a way that might have an effect on combustion in order to lower the maximum pressure rise rates and further improve emissions. The obtained experimental results show that in contrast to variable rate direct injection of water, fixed rate water–ethanol blending is counterproductive for the reduction of pressure rise rates at higher loads. In addition, increasing the water content in ethanol results in reduction of the effective load range and increased emissions.     

Utilization of green ammonia as a hydrogen energy carrier for decarbonization in spark ignition engines

Rising concerns about the dependence of modern energy systems on fossil fuels have raised the requirement for green alternate fuels to pave the roadmap for a sustainable energy future with a carbon-free economy. Massive expectations of hydrogen as an enabler for decarbonization of the energy sector are limited by the lack of required infrastructure, whose implementation is affected by the issues related to the storage and distribution of hydrogen energy. Ammonia is an effective hydrogen energy carrier with a well-established and mature infrastructure for long-distance transportation and distribution. The possibility for green ammonia production from renewable energy sources has made it a suitable green alternate fuel for the decarbonization of the automotive and power generation sectors. In this work, engine characteristics for ammonia combustion in spark ignition engines have been reported with a detailed note on engines fuelled with pure ammonia as well as blends of ammonia with gasoline, hydrogen, and methane. Higher auto-ignition temperature, low flammability, and lower flame speed of ammonia have a detrimental effect on engine characteristics, and it could be addressed either by incorporating engine modifications or by enhancing the fuel quality. Literature shows that the increase in compression ratio from 9.4:1 to 11.5:1 improved the maximum power by 59% and the addition of 10% hydrogen in supercharged conditions improved the indicated efficiency by 37%. Challenges and strategies for the utilization of ammonia as combustible fuel in engines are discussed by considering the need for technical advancements as well as social acceptance. Energy efficiency for green ammonia production is also discussed with a due note on techniques for direct synthesis of ammonia from air and water.