Experimental investigation of the effects of simultaneous hydrogen and nitrogen addition on the emissions and combustion of a diesel engine

Overcoming diesel engine emissions trade-off effects, especially NO_x and Bosch smoke number (BSN), requires investigation of novel systems which can potentially serve the automobile industry towards further emissions reduction. Enrichment of the intake charge with H₂ + N₂ containing gas mixture, obtained from diesel fuel reforming system, can lead to new generation low polluting diesel engines.     

Experimental investigation of the effects of separate hydrogen and nitrogen addition on the emissions and combustion of a diesel engine

An experimental investigation of the effects of separate hydrogen and nitrogen addition on the emissions and combustion of a diesel engine was performed and the results are presented in the current paper.     

Hydrogen effects on the diesel engine performance and emissions

In this research, effects of hydrogen addition on a diesel engine were investigated in terms of engine performance and emissions for four cylinders, water cooled diesel engine. Hydrogen was added through the intake port of the diesel engine. Hydrogen effects on the diesel engine were investigated with different amount (0.20, 0.40, 0.60 and 0.80 lpm) at different engine load (20%, 40%, 60%, 80% and 100% load) and the constant speed, 1800 rpm. When hydrogen amount is increased for all engine loads, it is observed an increase in brake specific fuel consumption and brake thermal efficiency due to mixture formation and higher flame speed of hydrogen gas according to the results. For the 0.80 lpm hydrogen addition, exhaust temperature and NOx increased at higher loads. CO, UHC and SOOT emissions significantly decreased for hydrogen gas as additional fuel at all loads. In this study, higher decrease on SOOT emissions (up to 0.80lpm) was obtained. In addition, for 0.80 lpm hydrogen addition, the dramatic increase in NOx emissions was observed.     

The effect of HRG gas addition on diesel engine combustion characteristics and exhaust emissions

Extensive studies have been dedicated in the last decade to the possibility to use hydrogen in the dual-fuel mode to improve combustion characteristics and emissions of a diesel engine. The results of these studies, using pure hydrogen or hydrogen containing gas produced through water electrolysis, are notably different.The present investigation was conducted on a tractor diesel engine running with small amounts of the gas—provided by a water electrolyzer—aspirated in the air stream inducted in the cylinder. The engine was operated at light and medium loads and various speeds.It was found that the addition of HRG gas has a slight negative impact, up to 2%, on the engine brake thermal efficiency. Smoke is significantly reduced, up to 30%, with HRG enrichment, while NO_x concentrations vary in both senses, up to 14%, depending on the engine operation mode. A relative small amount of HRG gas can be used with favorable effects on emissions and with a small penalty in thermal efficiency.     

Hydrogen energy share enhancement in a heavy duty diesel engine under RCCI combustion fueled with natural gas and diesel oil

The aim of this study is to enhance hydrogen energy share in a RCCI engine. The engine under consideration is fueled with diesel oil and natural gas enriched with hydrogen or syngas and is set to operate at 9.4 bar gross indicated mean effective pressure (Mid- Load). The syngas used in this study consists of hydrogen and carbon monoxide which are mixed together on a volumetric ratio of 80:20. A fixed amount of diesel oil is injected per cycle into the combustion chamber of the RCCI engine. Based on two different strategies, hydrogen or syngas mixed with exhaust gas recirculation are admitted gradually along with natural gas while ensuring that always the low temperature combustion concept is fulfilled. The RCCI engine operation is simulated through commercial software coupled with chemical kinetics solver. The simulation results show that without any engine diesel knock occurrence, by adding hydrogen to natural gas, the share of hydrogen energy could be increased up to 40.43% while the engine power output is reduced only by about 1%. Also, syngas addition to natural gas causes that the share of hydrogen energy could be increased up to 27.05% while improves the engine power more than 4%. At the same time, by considering two mentioned strategies, the overall hydrocarbon fuel consumption per cycle can be reduced by up to 46.60% and 33.86%, respectively. Moreover, having the gross indicated efficiency of well over 50% and significant reduction in the engine emissions compared to RCCI combustion fueled solely with natural gas and diesel oil are achievable.     

Theoretical study of the effects of engine parameters on performance and emissions of a pilot ignited natural gas diesel engine

With the increasing concern regarding diesel vehicle emissions and the rising cost of the liquid diesel fuel as well, more conventional diesel engines internationally are pursuing the option of converting to use natural gas as a supplement for the conventional diesel fuel (dual fuel natural gas/diesel engines). The most common natural gas/diesel operating mode is referred to as the pilot ignited natural gas diesel engine (PINGDE) where most of the engine power output is provided by the gaseous fuel while a pilot amount of the liquid diesel fuel injected near the end of the compression stroke is used only as an ignition source of the gaseous fuel–air mixture. The specific engine operating mode, in comparison with conventional diesel fuel operation, suffers from low brake engine efficiency and high carbon monoxide (CO) emissions. In order to be examined the effect of increased air inlet temperature combined with increased pilot fuel quantity on performance and exhaust emissions of a PINGD engine, a theoretical investigation has been conducted by applying a comprehensive two-zone phenomenological model on a high-speed, pilot ignited, natural gas diesel engine located at the authors' laboratory. The main objectives of the present work are to record the variation of the relative impact each one of the above mentioned parameters has on performance and exhaust emissions and also to reveal the advantages and disadvantages each one of the proposed method. It becomes more necessary at high engine load conditions where the simultaneous increase of the specific engine parameters may lead to undesirable results with nitric oxide emissions.     

Effect of exhaust gas recirculation (EGR) temperature for various EGR rates on heavy duty DI diesel engine performance and emissions

DI diesel engines are well established today as the main powertrain solution for trucks and other relevant heavy duty vehicles. At the same time emission legislation (mainly for NO_x and particulate matter) becomes stricter, reducing their limit to extremely low values. One efficient method to control NO_x in order to achieve future emissions limits is the use of rather high exhaust gas recirculation (EGR) rates accompanied by increased boost pressure to avoid the negative impact on soot emissions. The method is based on the reduction of gas temperature level and O₂ availability inside the combustion chamber, but unfortunately it has usually an adverse effect on soot emissions and brake specific fuel consumption (bsfc). The use of high EGR rates creates the need for EGR gas cooling in order to minimize its negative impact on soot emissions especially at high engine load were the EGR flow rate and exhaust temperature are high. For this reason in the present paper it is examined, using a multi-zone combustion model, the effect of cooled EGR gas temperature level for various EGR percentages on performance and emissions of a turbocharged DI heavy duty diesel engine operating at full load. Results reveal that the decrease of EGR gas temperature has a positive effect on bsfc, soot (lower values) while it has only a small positive effect on NO. As revealed, the effect of low EGR temperature is stronger at high EGR rates.     

The effect of biodiesel fuel obtained from waste frying oil on direct injection diesel engine performance and exhaust emissions

In this study, usage of methyl ester obtained from waste frying oil (WFO) is examined as an experimental material. A reactor was designed and installed for production of methyl ester from this kind of oil. Physical and chemical properties of methyl ester were determined in the laboratory. The methyl ester was tested in a diesel engine with turbocharged, four cylinders and direct injection. Gathered results were compared with No. 2 diesel fuel. Engine tests results obtained with the aim of comparison from the measures of torque, power; specific fuel consumptions are nearly the same. In addition, amount of emission such as CO, CO₂, NO_x, and smoke darkness of waste frying oils are less than No. 2 diesel fuel.     

Experimental heat release analysis and emissions of a HSDI diesel engine fueled with ethanol–diesel fuel blends

An experimental study is conducted to evaluate the effects of using blends of ethanol with conventional diesel fuel, with 5%, 10% and 15% (by vol.) ethanol, on the combustion and emissions of a standard, fully instrumented, four-stroke, high-speed, direct injection (HSDI), ‘Hydra’ diesel engine located at the authors’ laboratory. The tests are conducted using each of the above fuel blends or neat diesel fuel, with the engine working at a speed of 2000 rpm and at four different loads. In each test, combustion chamber and fuel injection pressure diagrams are obtained using a specially developed, high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams is developed and used, with the pertinent application of the energy and state equations. From the analysis results, plots of the history in the combustion chamber of the gross heat release rate and other related parameters reveal some very interesting features, which shed light on the combustion mechanism when using these blends. Moreover, for each test, volumetric fuel consumption, exhaust smokiness and exhaust regulated gas emissions are measured. The differences in the performance and exhaust emission parameters from the baseline operation of the diesel engine, i.e., when working with neat diesel fuel, are determined and compared. The heat release analysis results for the relevant combustion mechanism, combined with the widely differing physical and chemical properties of the ethanol against those for the diesel fuel, are used to aid the correct interpretation of the observed engine behavior.     

The effects of hydrogen enriched natural gas under different engine loads in a diesel engine

Natural gas, which is among the alternative fuels, has become widespread in the transportation as it is both economical and environmentally friendly. While the use of natural gas is at a significant level in spark ignition engines, it has not yet been implemented in compression ignition engines (CI) as it worsens combustion due to ignition delay. In CI engines, however, the combustion properties of natural gas (NG) can be improved by adding hydrogen (H₂) to NG. This is one of the methods applied to use natural gas in CI engines. In this experimental study, two different volumetric rates of NG and NG/H₂ mixtures were added to the combustion air in a CI engine, and engine performance and emissions were examined under different engine loads. The experiments were performed at two different engine speeds, four different engine loads and no-load condition. An engine cylinder pressure of 59.16 bar, which is the closest value to the 59.39 bar obtained in the use of diesel fuel, was obtained at 1500 rpm for “Diesel + NG(500 g/h)” and 59.9 bar (highest values) was obtained for “Diesel + (500 g/h) [80%NG+20%H₂]" at 1750 rpm. For “Diesel + NG(250 g/h)” (Mix1) and “Diesel + NG(500 g/h)” (Mix2), as the engine speed increases, at the point where the maximum in-cylinder pressure is obtained occurs further to the right from top dead center (TDC). With the addition of 500 g/h NG, an increase of 4.5% was achieved in the cylinder pressure at full load, while an increase of 6.5% was achieved in the case of using “Diesel + (500 g/h) [80%NG+20%H₂]". Although the effect of the NG and NG/H₂ mixtures on in-cylinder pressure was small, the fuel consumption and thermal efficiency improved. Substantial improvements in hydrocarbon (HC) emissions were observed with the use of “Diesel + (250 g/h)[80%NG+20%H₂]”. Carbon dioxide (CO₂) emissions decreased with speed increase, but no significant differences in terms of CO₂ emissions were observed between the mixtures. There was a maximum difference of 15% between the diesel and the mixtures in CO₂ emissions. Although there was a decrease in nitrogen oxide (NO_x) levels with the increase in engine speed, the lowest NO_x emissions of 447.6 ppmvol was observed in “Diesel + NG(250 g/h)” (Mix1) at 1750 rpm at maximum load.     

Research of performance and emission indicators of the compression-ignition engine powered by hydrogen - Diesel mixtures

The purpose of this study is to use the hydrogen – diesel mixture in Audi/VW 1.9 TDI turbocharged CI engine equipped with dynamometer and examine the performance and emission indicators by comparing it with sole diesel mode. The recent diesel emission scandals because of manufacturers cheating the laboratory tests, have initiated the discussions about the sustainable and environmentally friendly diesel engines. The CI engine without major engine modifications was set to operate at two speeds of 1900 rpm and 2500 rpm. At each of speed, the experiment was conducted at three BMEP: 0.4 MPa, 0.6 MPa, and 0.8 MPa. The test engine was operated using diesel fuel with amounts of 10 l/min, 20 l/min, and 30 l/min of hydrogen gas, supplied with air into intake manifold before the turbocharger. Relatively low hydrogen fraction (max. 15.74%) has effect on diesel combustion process and performance indicators at the all range of BMEP. The in-cylinder peak pressure at both speeds of 1900 rpm and 2500 rpm was lower than that with pure diesel fuel, as the small amount of hydrogen shortens the CI engine ignition delay period and decreases the rate of pressure rise. The decrease of BTE noticed, and increase of BSFC was registered with low hydrogen fraction (hydrogen amounts of 10 l/min, 20 l/min). However, with increase of hydrogen amount to 30 l/min, the BTE increased and BSFC decreased to the level, which was lower than that at the pure diesel test. The supply of hydrogen positively effects on engine emissions: the smokiness, NO_x, CO₂, CO decreased, the only hydrocarbon increased. The effect of hydrogen fraction on the combustion and emission characteristics of the diesel - hydrogen mixture was validated by AVL (Anstalt für Verbrennungskraftmaschinen List) BOOST and analysed with presentations of the main limitations and perspectives.     

Study of diesel engine performance and emissions during a Transient Cycle applying an engine mapping-based methodology

An engine mapping-based methodology was developed in order to be able to make a first approximation of the engine performance and emissions during a speed/torque vs. time Transient Cycle. The procedure is based on a previous steady-state experimental investigation of the engine for the formulation of polynomial expressions of all interesting engine properties with respect to engine speed and torque. Correction coefficients are then applied to account for transient discrepancies based on individual transient experiments. The developed algorithm was applied for the case of a heavy-duty diesel engine running on the European Transient Cycle. A comparative analysis was performed for each section of the Cycle, which revealed that the first part (urban driving) is responsible for the biggest amount of emissions (in g) owing to the most frequent and abrupt load changes involved. The obvious advantage of the proposed methodology is the fact that the effect of internal or external (after-treatment) measures can be easily incorporated in the code and quantified in terms of emissions improvement.     

Experimental study of various effects of exhaust gas recirculation (EGR) on combustion and emissions of an automotive direct injection diesel engine

Cooled exhaust gas recirculation (EGR) is a common way to control in-cylinder NO_x production and is used on most modern high-speed direct injection (HSDI) diesel engines. However EGR has different effects on combustion and emissions production that are difficult to distinguish (increase of intake temperature, delay of rate of heat release (ROHR), decrease of peak heat release, decrease in O₂ concentration (and thus of global air/fuel ratio (AFR)) and flame temperature, increase of lift-off length, etc.), and thus the influence of EGR on NO_x and particulate matter (PM) emissions is not perfectly understood, especially under high EGR rates. An experimental study has been conducted on a 2.0 l HSDI automotive diesel engine under low-load and part load conditions in order to distinguish and quantify some effects of EGR on combustion and NO_x/PM emissions. The increase of inlet temperature with EGR has contrary effects on combustion and emissions, thus sometimes giving opposite tendencies as traditionally observed, as, for example, the reduction of NO_x emissions with increased inlet temperature. For a purely diffusion combustion the ROHR is unchanged when the AFR is maintained when changing in-cylinder ambient gas properties (temperature or EGR rate). At low-load conditions, use of high EGR rates at constant boost pressure is a way to drastically reduce NO_x and PM emissions but with an increase of brake-specific fuel consumption (BSFC) and other emissions (CO and hydrocarbon), whereas EGR at constant AFR may drastically reduce NO_x emissions without important penalty on BSFC and soot emissions but is limited by the turbocharging system.     

Experimental study of engine performance and emissions for hydrogen diesel dual fuel engine with exhaust gas recirculation

With an alarming enlargement in vehicular density, there is a threat to the environment due to toxic emissions and depleting fossil fuel reserves across the globe. This has led to the perpetual exploration of clean energy resources to establish sustainable transportation. Researchers are continuously looking for the fuels with clean emission without compromising much on vehicular performance characteristics which has already been set by efficient diesel engines. Hydrogen seems to be a promising alternative fuel for its clean combustion, recyclability and enhanced engine performance. However, problems like high NOx emissions is seen as an exclusive threat to hydrogen fuelled engines. Exhaust gas recirculation (EGR), on the other hand, is known to overcome the aforementioned problem. Therefore, this study is conducted to study the combined effect of hydrogen addition and EGR on the dual fuelled compression ignition engine on a single cylinder diesel engine modified to incorporate manifold hydrogen injection and controlled EGR. The experiments are conducted for 25%, 50%, 75% and 100% loads with the hydrogen energy share (HES) of 0%, 10% and 30%. The EGR rate is controlled between 0%, 5% and 10%. With no substantial decrement in engine's brake thermal efficiency, high gains in terms of emissions are observed due to synergy between hydrogen addition and EGR. The cumulative reduction of 38.4%, 27.4%, 33.4%, 32.3% and 20% with 30% HES and 10% EGR is observed for NOx, CO2, CO, THC and PM, respectively. Hence, the combination of hydrogen addition and EGR is observed to be advantageous for overall emission reduction.     

Syngas production through gasification of coal water mixture and power generation on dual-fuel diesel engine

In the present study, a syngas was produced by preparing coal water mixtures of two different concentrations and gasifying the coal water mixtures. An entrained-flow gasifier of 1 ton/day scale was used and, after undergoing a purification process, the produced syngas was applied to a modified diesel engine for power generation. As the gasification temperature increased, the carbon conversion and the cold gas efficiency were found to increase. In the composition of the produced syngas, the content of H₂ remained constant, that of CO increased, and those of CO₂ and CH₄ decreased. The carbon conversion increased with equivalence ratio. A maximum cold gas efficiency of 66.1% was found at the equivalence ratio of 0.43. N₂ was additionally supplied to verify the gasification characteristics depending on the gas feed flow rate. The optimum feed flow rate was verified at different slurry concentrations and equivalence ratio. The produced syngas was supplied to a modified diesel engine and operated depending on the syngas feed flow rate and the engine operation conditions. The brake thermal efficiency of the engine was constant regardless of the syngas feed flow rate. The diesel engine showed high efficiency despite the mixing of the syngas.     

The comparison of engine performance and exhaust emission characteristics of sesame oil–diesel fuel mixture with diesel fuel in a direct injection diesel engine

The use of vegetable oils as a fuel in diesel engines causes some problems due to their high viscosity compared with conventional diesel fuel. Various techniques and methods are used to solve the problems resulting from high viscosity. One of these techniques is fuel blending. In this study, a blend of 50% sesame oil and 50% diesel fuel was used as an alternative fuel in a direct injection diesel engine. Engine performance and exhaust emissions were investigated and compared with the ordinary diesel fuel in a diesel engine. The experimental results show that the engine power and torque of the mixture of sesame oil–diesel fuel are close to the values obtained from diesel fuel and the amounts of exhaust emissions are lower than those of diesel fuel. Hence, it is seen that blend of sesame oil and diesel fuel can be used as an alternative fuel successfully in a diesel engine without any modification and also it is an environmental friendly fuel in terms of emission parameters.     

Performance, emissions and heat release characteristics of direct injection diesel engine operating on diesel oil emulsion

Emulsions of diesel and water are often promoted as being able to overcome the difficulty of simultaneously reducing emissions of both oxidises of nitrogen (NO_x) and particulate matter from diesel engines. In this paper we present measurements of the performance and NO_x and hydrocarbon emissions of a diesel engine operating on a typical diesel oil emulsion and examine through the use of heat release analysis differences found during its combustion relative to standard diesel in the same engine. While producing similar or greater thermal efficiency and improved NO_x and hydrocarbon emission outcomes, use of the emulsion also results in an increase in brake specific fuel consumption. Use of the emulsion is also shown to result in a retarded fuel injection, but smaller ignition delay for the same engine timing. As a result of these changes, cylinder pressures and temperatures are lower.     

The effect of biodiesel and bioethanol blended diesel fuel on nanoparticles and exhaust emissions from CRDI diesel engine

Biofuel (biodiesel, bioethanol) is considered one of the most promising alternative fuels to petrol fuels. The objective of the work is to study the characteristics of the particle size distribution, the reaction characteristics of nanoparticles on the catalyst, and the exhaust emission characteristics when a common rail direct injection (CRDI) diesel engine is run on biofuel-blended diesel fuels. In this study, the engine performance, emission characteristics, and particle size distribution of a CRDI diesel engine that was equipped with a warm-up catalytic converters (WCC) or a catalyzed particulate filter (CPF) were examined in an ECE (Economic Commission Europe) R49 test and a European stationary cycle (ESC) test. The engine performance under a biofuel-blended diesel fuel was similar to that under D100 fuel, and the high fuel consumption was due to the lowered calorific value that ensued from mixing with biofuels. The use of a biodiesel–diesel blend fuel reduced the total hydrocarbon (THC) and carbon monoxide (CO) emissions but increased nitrogen oxide (NO_x) emissions due to the increased oxygen content in the fuel. The smoke emission was reduced by 50% with the use of the bioethanol–diesel blend. Emission conversion efficiencies in the WCC and CPF under biofuel-blended diesel fuels were similar to those under D100 fuel. The use of biofuel-blended diesel fuel reduced the total number of particles emitted from the engine; however, the use of biodiesel–diesel blends resulted in more emissions of particles that were smaller than 50 nm, when compared with the use of D100. The use of a mixed fuel of biodiesel and bioethanol (BD15E5) was much more effective for the reduction of the particle number and particle mass, when compared to the use of BD20 fuel.     

Effect of hydrogen addition on RCCI combustion of a heavy duty diesel engine fueled with landfill gas and diesel oil

The aim of this study is to investigate the effects of hydrogen addition on RCCI combustion of an engine running on landfill gas and diesel oil. A single cylinder heavy– duty diesel engine is set in operation at 9.4 bar IMEP. A certain amount of diesel fuel per cycle is fed into the engine and hydrogen is added to landfill gas while keeping fixed fuel energy content. The developed simulation results confirm that hydrogen addition which is the most environmental friendly fuel causes the fuel consumption per any cycle to reduce. Also, the peak pressure is increased while the engine load is reduced up to 4%. Landfill gas which is enriched with hydrogen improves the rate of methane dissociation and reduces the combustion duration at the same time the engine operation would not be exposed to diesel knock. Moreover, hydrogen addition to landfill gas would reduce engine emissions considerably.     

The effect of boost pressure on the performance characteristics of a diesel engine: A neuro-fuzzy approach

This paper uses a neuro-fuzzy interface system (ANFIS) to study the effect of boost pressure on the efficiency, brake mean effective pressure (BMEP), and the brake specific fuel consumption (BSFC) of a single cylinder diesel engine. Experimental data were used as inputs to ANFIS to simulate the engine performance characteristics. The experimental as well as the model results emphasize the role of boost pressure in improving the different engine characteristics. The results show that the ANFIS technique can be used adequately to identify the effect of boost pressure on the different engine characteristics. In addition, different data points that were not used for ANFIS training were used to validate the developed models. The results suggest that ANFIS can be used accurately to predict the effect of boost pressure on the different engine characteristics.