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.     

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 of addition of hydrogen and exhaust gas recirculation on characteristics of hydrogen gasoline engine

The effects of exhaust gas recirculation (EGR) on combustion and emissions under different hydrogen ratios were studied based on an engine with a gasoline intake port injection and hydrogen direct injection. The peak cylinder pressure increases by 9.8% in the presence of a small amount of hydrogen. The heat release from combustion is more concentrated, and the engine torque can increase by 11% with a small amount of hydrogen addition. Nitrogen oxide (NOx) emissions can be reduced by EGR dilution. Hydrogen addition offsets the blocking effect of EGR on combustion partially, therefore, hydrogen addition permits a higher original engine EGR rate, and yields a larger throttle opening, which improves the mechanical efficiency and decreases NOx emissions by 54.8% compared with the original engine. The effects of EGR on carbon monoxide (CO) and hydrocarbon (HC) emissions are not obvious and CO and HC emissions can be reduced sharply with hydrogen addition. CO, HC, and NOx emissions can be controlled at a lower level, engine output torque can be increased, and fuel consumption can be reduced significantly with the co-control of hydrogen addition and EGR in a hydrogen gasoline engine.     

废气再循环在柴油机中的应用

本文回顾了废气再循环（EGR）在减少排放，特别是减少NOx排放上的潜力以及限定这一技术的应用范围。详细分析了RGR装置对柴油机的排放和性能的影响，通过深入分析，发现在柴油机进气中引入废气再循环（EGR），相当如置换了部分吸入的空气，这种方式能充分减少NOx的排放。因此，废气再循环的使用是最有效改善尾气排放的技术措施之一。     

Hydrogen supplemented natural gas effect on a DI diesel engine operating under dual fuel mode with a biodiesel pilot fuel

In order to slow down the continuing environmental deterioration, regulations for pollutant emissions limitations are increasingly rigorous. The development of new alternative fuels for internal combustion engines is a very interesting solution not only to overcome the pollution problem but also because of the petroleum shortage. In this context, the present work investigates the improvement of a DI diesel engine operating at constant speed (1500 rpm) and under dual fuel mode with eucalyptus biodiesel and natural gas (NG) enriched by various H₂ quantities (15, 25 and 30 by v%). The eucalyptus biodiesel quantity injected into the engine cylinder is kept constant, to supply around 10% of the engine nominal power, for all examined engine loads. The engine load is further increased using only the gaseous fuel (NG+H₂), which is introduced with the intake air. The effect of H₂/NG blending ratio on the combustion parameters, performance and pollutant emissions of the engine is investigated and compared with those of pure NG case. An important benefit in terms of brake specific fuel consumption, reaching a decrease of 4–10% with the 25% H₂ blend compared to the pure NG case, is achieved. Concerning the pollutant emissions, NG enrichment with H₂ is an efficient solution to enhance the combustion process and hence reduce carbon monoxide, unburned hydrocarbon and soot emissions at high loads where they are important for pure NG. However for the nitrogen oxide emissions, NG blending with H₂ is attractive only at low and medium loads where their levels are lower than pure NG.     

Influence of injection timing on the exhaust emissions of a dual-fuel CI engine

Environmental concerns and limited amount of petroleum fuels have caused interests in the development of alternative fuels for internal combustion (IC) engines. As an alternative, biodegradable, and renewable fuel, ethanol is receiving increasing attention. Therefore, in this study, influence of injection timing on the exhaust emission of a single cylinder, four stroke, direct injection, naturally aspirated diesel engine has been experimentally investigated using ethanol blended diesel fuel from 0% to 15% with an increment of 5%. The engine has an original injection timing 27° CA BTDC. The tests were performed at five different injection timings (21°, 24°, 27°, 30°, and 33° CA BTDC) by changing the thickness of advance shim. The experimental test results showed that NO_x and CO₂ emissions increased as CO and HC emissions decreased with increasing amount of ethanol in the fuel mixture. When compared to the results of original injection timing, at the retarded injection timings (21° and 24° CA BTDC), NO_x and CO₂ emissions increased, and unburned HC and CO emissions decreased for all test conditions. On the other hand, with the advanced injection timings (30° and 33° CA BTDC), HC and CO emissions diminished, and NO_x and CO₂ emissions boosted for all test conditions.     

Performance and combustion characteristic of CI engine fueled with hydrogen enriched diesel

The combustion of hydrogen–diesel blend fuel was investigated under simulated direct injection (DI) diesel engine conditions. The investigation presented in this paper concerns numerical analysis of neat diesel combustion mode and hydrogen enriched diesel combustion in a compression ignition (CI) engine. The parameters varied in this simulation included: H₂/diesel blend fuel ratio, engine speed, and air/fuel ratio. The study on the simultaneous combustion of hydrogen and diesel fuel was conducted with various hydrogen doses in the range from 0.05% to 50% (by volume) for different engine speed from 1000 – 4000 rpm and air/fuel ratios (A/F) varies from 10 – 80. The results show that, applying hydrogen as an extra fuel, which can be added to diesel fuel in the (CI) engine results in improved engine performance and reduce emissions compared to the case of neat diesel operation because this measure approaches the combustion process to constant volume. Moreover, small amounts of hydrogen when added to a diesel engine shorten the diesel ignition lag and, in this way, decrease the rate of pressure rise which provides better conditions for soft run of the engine. Comparative results are given for various hydrogen/diesel ratio, engine speeds and loads for conventional Diesel and dual fuel operation, revealing the effect of dual fuel combustion on engine performance and exhaust emissions.     

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

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

Effect of addition of hydrogen and TiO2 in gasoline engine in various exhaust gas recirculation ratio

The effects of hydrogen ratios on combustion and emission characteristics of gasoline engine were studied under different exhaust gas recirculation (EGR), ignition timing and ignition pressure. The test performed in a modified gasoline direct ignition engine at different hydrogen ratios of 0%, 5%, 10% and 25%. In addition, the EGR rate set to 0%, 5%, 10% and 20% to study the combustion and emission characteristics. Addition to the different hydrogen fractions, 5% of TiO₂ is added to increase the combustion characteristics with reduced emission. Regarding the results of the current study, the engine torque increases by 15% due to the addition of hydrogen in gasoline, while mechanical efficiency is improved by achieving a large throttle opening. At the same time, NOx emission decreased by 62% compared to the unmodified engine due to the influence of EGR, hydrogen ratio and high oxygen concentration TiO₂. Moreover, the emission of CO and HC also reduced due to the influence of hydrogen fuel. Additionally, few more tests are taken to monitor the effect of the injection pressure for the hydrogen fuel. Higher injection reports higher effective thermal efficiency at 4 MPa and lower NOx. Reasonable injection pressure results in shorten flame development period.     

Effect of hydrogen addition to intake gas on combustion and exhaust emission characteristics of a diesel engine

The present study experimentally investigated the performance and emission characteristics of the diesel engine with hydrogen added to the intake air at late diesel-fuel injection timings. The diesel-fuel injection timing and the hydrogen fraction in the intake mixture were varied while the available heat produced by diesel-fuel and hydrogen per second of diesel fuel and hydrogen was kept constant at a certain value. NO showed minimum at specific hydrogen fraction. The maximum rate of incylinder pressure rise also showed minimum at 10 vol. % hydrogen fraction. However, it is desirable to set the maximum rate of incylinder pressure rise less than 0.5 MPa/deg. to realize low level of combustion noise and NO emission. We attempt to reduce further NO and smoke emissions by EGR. As the result, in the case of the diesel-fuel injection timing of −2 °. ATDC with 3.9 vol. % hydrogen addition, the smoke emission value was 0%, NO emission was low, the cyclic variation was low, and the maximum rate of incylinder pressure rise was acceptable under a nearly stoichiometric condition without sacrificing indicated thermal efficiency.     

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.     

Effect of fuel opening injection pressure and injection timing of hydrogen enriched rice bran biodiesel fuelled in CI engine

Fuel opening injection pressure and injection timing are important injection parameters, and they have a significant influence on engine combustion, performance, and emissions. The focus of this work is to improve the performance and emissions of single-cylinder diesel engines by using injection parameters in engines running with rice bran biodiesel 10% blend (RB10+H₂) and 20% blend (RB20+H₂) with a fixed hydrogen flow rate of 7 lpm. In addition, hydrogen and biodiesel are excellent alternatives to conventional fuels, which can reduce energy consumption and strict emission standards. The investigation is conducted for three different opening injection pressure of 220, 240, 260 bar, and four different injection timings of 20°, 22°, 24°, and 26° bTDC. Results indicate that the sample ‘RB10+H₂’ provides 3.32% higher BTE and reduces the fuel consumption by 13% as diesel fuel. The blend RB10+H₂ attributes a maximum cylinder pressure of 68.7 bar and a peak HRR value of 49 J/ºCA. Further, compared to diesel, RB10+H₂ blend emits lower CO, HC, and smoke opacity by 17%, 22%, and 16%, respectively. However, an almost 12% increase of nitrogen oxides for the RB10+H₂ blend is observed. However, with advanced injection timing and higher opening injection pressure, NOx emissions is slightly increased.     

Effect of hydrogen addition on criteria and greenhouse gas emissions for a marine diesel engine

Hydrogen remains an attractive alternative fuel to petroleum and a number of investigators claim that adding hydrogen to the air intake manifold of a diesel engine will reduce criteria emissions and diesel fuel consumption. Such claims are appealing when trying to simultaneously reduce petroleum consumption, greenhouse gases and criteria pollutants. The goal of this research was to measure the change in criteria emissions (CO, NO_x, and PM_2.5) and greenhouse gases such as carbon dioxide (CO₂), using standard test methods for a wide range of hydrogen addition rates. A two-stroke Detroit Diesel Corporation 12V-71TI marine diesel engine was mounted on an engine dynamometer and tested at three out of the four loads specified in the ISO 8178-4 E3 emission test cycle and at idle. The engine operated on CARB ultra-low sulfur #2 diesel with hydrogen added at flow rates of 0, 22 and 220 SLPM.     

Effect of manifold and port injection of hydrogen and exhaust gas recirculation (EGR) in dairy scum biodiesel - low energy content gas-fueled CI engine operated on dual fuel mode

In this current work, exhaustive research work is conducted in three phases, in the initial phase, WFO was used for producing WFO treated biomass and in the second phase, influence of PFIP and PFIT has been examined. Further in the successive phase, effect of hydrogen HMI, HPI and EGR on the combustion and emission characteristics of CRDI diesel engine operated on dual-fuel mode using DiSOME and PG combination is evaluated. In the current study, in a CRDI engine, PFIT was employed ranging from 0 to 15°CA bTDC and changed in steps of 5 and PFIP was used from 600 to 1000 bar and varied in successive steps of 200 bar. Further flow rate of hydrogen was kept 8 L/min constant and HMIT was employed in the range from TDC to 15°aTDC and changed in stages of 5. Correspondingly, HID was varied from 30 to 90°CA with 30°CA dwell and EGR was used in the range from 0 to 15% by vol. and varied in steps of 5. Outcome of the work showed that, DiSOME-PG operation with 10°bTDC PFIT, 800 bar PFIP, 10°aTDC of HMI, 60°CAHID and 5% EGR rate showed lower BTE by 5.8% and increased smoke levels by 10.8%, HC by 8.6%, CO by 6.5% and marginally decreased NOx by 6.4% was observed in comparison to the same fuel blend with zero EGR at 80% load. Further, marginally amplifiedID and CD with loweredCP and HRR has been noticed. Study revealed thatH₂addition to low calorific value gas (PG), method of pilot fuel addition and EGR is affected dual fuel engine performance, but provided drastic reductions in smoke and NOx emissions.     

Direct injection of hydrogen main fuel and diesel pilot fuel in a retrofitted single-cylinder compression ignition engine

Up to 90% hydrogen energy fraction was achieved in a hydrogen diesel dual-fuel direct injection (H2DDI) light-duty single-cylinder compression ignition engine. An automotive-size inline single-cylinder diesel engine was modified to install an additional hydrogen direct injector. The engine was operated at a constant speed of 2000 revolutions per minute and fixed combustion phasing of ?10 crank angle degrees before top dead centre (°CA bTDC) while evaluating the power output, efficiency, combustion and engine-out emissions. A parametric study was conducted at an intermediate load with 20–90% hydrogen energy fraction and 180-0 °CA bTDC injection timing. High indicated mean effective pressure (IMEP) of up to 943 kPa and 57.2% indicated efficiency was achieved at 90% hydrogen energy fraction, at the expense of NO_x emissions. The hydrogen injection timing directly controls the mixture condition and combustion mode. Early hydrogen injection timings exhibited premixed combustion behaviour while late injection timings produced mixing-controlled combustion, with an intermediate point reached at 40 °CA bTDC hydrogen injection timing. At 90% hydrogen energy fraction, the earlier injection timing leads to higher IMEP/efficiency but the NO_x increase is inevitable due to enhanced premixed combustion. To keep the NO_x increase minimal and achieve the same combustion phasing of a diesel baseline, the 40 °CA bTDC hydrogen injection timing shows the best performance at which 85.9% CO₂ reduction and 13.3% IMEP/efficiency increase are achieved.     

Studies on the effect of hydrogen induction on performance,emission and combustion behaviour of a WCO emulsion based dual fuel engine

This paper aims at studying the effect of hydrogen induction on engine performance, emission and combustion behaviour of a diesel engine fuelled with the emulsion of used palm oil (called as WCO-waste cooking oil) as pilot fuel and hydrogen as primary fuel. A single cylinder water-cooled direct injection diesel engine was tested at 100% and 40% loads. Results were compared with neat diesel, neat WCO and WCO emulsion at both loads in single fuel operation. WCO emulsion in single fuel mode indicated improvement in performance and reduction in all emissions as compared to neat WCO. Dual fuel operation with hydrogen induction further reduced the emissions of smoke HC and CO with WCO as pilot fuel at all power outputs. However, hydrogen induction resulted in reduced thermal efficiency at 40% load. WCO emulsion showed higher ignition delay as compared to neat WCO. Dual fuel operation with hydrogen induction increased the ignition delay further. Heat release pattern showed higher premixed combustion rate with hydrogen induction mainly at high power outputs. Premixed combustion rate became very high at higher rates of hydrogen admission mainly at high power output. In general, hydrogen induction showed superior performance at high power output and inferior performance at low power output with WCO emulsion as injected fuel.     

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.     

Experimental investigations on a hydrogen diesel homogeneous charge compression ignition engine with exhaust gas recirculation

In this experimental study, hydrogen was inducted along with air and diesel was injected into the cylinder using a high pressure common rail system, in a single cylinder homogeneous charge compression ignition engine. An electronic controller was used to set the required injection timing of diesel for best thermal efficiency. The influences of hydrogen to diesel energy ratio, output of the engine and exhaust gas recirculation (EGR) on performance, emissions and combustion were studied in detail. An increase in the amount of hydrogen improved the thermal efficiency by retarding the combustion process. It also lowered the exhaust emissions. Large amounts of hydrogen and EGR were needed at high outputs for suppressing knock. The range of operation was brake mean effective pressures of 2–4 bar. The levels of HC and CO emitted were not significantly influenced by the amount of hydrogen that was used.     

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.