Research on combustion and emission characteristics of a hydrous ethanol/hydrogen combined injection spark ignition engine under lean-burn conditions

Ethanol, as one of the carbon-neutral fuels for spark ignition (SI) engine, has been widely used. Dehydration and purification of ethanol during production process will lead to high energy consumption. If hydrous ethanol can be directly applied to the engine, the cost of use will be greatly reduced. Due to the high latent heat of vaporization of ethanol and water, it is necessary to consider the performance of atomization, evaporation and combustion stability when hydrous ethanol is used in engine. As a zero-carbon fuel, hydrogen has excellent characteristics such as low ignition energy, fast flame propagation speed and wide combustion limit. The combination of hydrous ethanol and hydrogen can reduce the use cost and ensure better combustion performance. Therefore, this study explores the performance of hydrous ethanol/hydrogen in SI combined injection engine. The hydrous ethanol is injected into the intake port and the hydrogen is directly injected into the cylinder during the compression stroke. In this study, we firstly analyze the optimal water blending ratio (ω) of hydrous ethanol, which including 0, 3%, 6%, 9% and 12%. The experimental results show that the hydrous ethanol with 9% water ratio has the best performance without hydrogen addition. Based on the 9% water ratio, the effects of hydrogen blending ratio (0, 5%, 10%, 15% and 20%) on the combustion and emission under different excess air ratio (λ) (1, 1.1, 1.2, 1.3, 1.4). Hydrogen addition can increase the degree of constant volume combustion, so that the maximum cylinder pressure and temperature increase with the increase of the hydrogen blending ratio (HBR). When λ = 1.3 and HBR = 20%, the maximum in-cylinder pressure can be increased by 108.64% compared to pure hydrous ethanol. Hydrogen effectively increases the indicated mean effective pressure (IMEP) and reduces the coefficient of variation of IMEP (COV_IMEP). Adding hydrogen can reduce CO and HC emissions, while NO_x emissions will increase. When λ = 1.2 and HBR increasing from 0 to 20%, the NOx emissions increase by 106.75%, but it is still less than the NOx emissions of pure hydrous ethanol at λ = 1. On the whole, hydrogen direct injection can improve the combustion performance of hydrous ethanol and achieve stable combustion under lean-burn conditions.     

Energy and exergy analysis of a combined injection engine using gasoline port injection coupled with gasoline or hydrogen direct injection under lean-burn conditions

Hydrogen is considered to be a suitable supplementary fuel for Spark Ignition (SI) engines. The energy and exergy analysis of engines is important to provide theoretical fundaments for the improvement of energy and exergy efficiency. However, few studies on the energy and exergy balance of the engine working under Hydrogen Direct Injection (HDI) plus Gasoline Port Injection (GPI) mode under lean-burn conditions are reported. In this paper, the effects of two different modes on the energy and exergy balance of a SI engine working under lean-burn conditions are presented. Two different modes (GPI + GDI and GPI + HDI), five gasoline and hydrogen direct injection fractions (0, 5%, 10%, 15%, 20%), and five excess air ratios (1, 1.1, 1.2, 1.3, 1.4) are studied. The results show that the cooling water takes the 39.40% of the fuel energy on average under GPI + GDI mode under lean-burn conditions, and the value is 40.70% for GPI + HDI mode. The exergy destruction occupies the 56.12% of the fuel exergy on average under GPI + GDI mode under lean-burn conditions, and the value is 54.89% for GPI + HDI mode. The brake thermal efficiency and exergy efficiency of the engine can be improved by 0.29% and 0.31% at the excess air ratio of 1.1 under GPI + GDI mode on average, and the average values are 0.56% and 0.71% for GPI + HDI mode.     

An experimental investigation of the impact of added HHO gas on automotive emissions under idle conditions

The paper describes an experiment aimed at specifying the effects of adding Brown's gas (HHO gas) in automotive engines operating at idle speed. HHO gas was obtained from the author's parallel plate generator with a single central anode and two side cathodes separated by six neutral plates. The generator was powered by an external power source (power supply unit) and produced a constant HHO gas flow rate in the experiment. The so obtained HHO gas was added to the engine intake systems of 5 passenger cars – three SI engines, i.e. Fiat Cinquecento, Renault Twingo, and Opel Corsa and two CI engines, i.e. Skoda Octavia and Opel Combo. The engines operated in idling conditions. The MAHA MGT5 analyzer measured the concentrations of CO, HC, NOx in the exhaust gases of those cars first fueled by stock fuel (SF) only and then with added HHO gas, i.e. SF + HHO. The ambient conditions remained constant.The results show that fueling with an HHO gas additive has an impact on emissions: CO and HC concentrations in the exhaust gases were reduced in the most of the cases; NOx concentration was reduced in the SI engines but increased in the Diesel ones. Adding HHO gas to the engine intake system of the Fiat Cinquecento operating at idle slightly deteriorated the combustion process there (the impact of carburetor-based supply without feedback). Although HC concentration was lower by 24%, the amount of CO increased by 34% and nitrogen oxides hardly changed. CO concentration if any decreased in the other vehicles.The concentration of HC in the exhaust gases of each of the vehicles show that adding HHO gas to the original fuel, regardless of fueling methods and techniques, reduces the concentration of unburned hydrocarbons: by more than 20% in the Fiat and by about 40% in the others. The NOx concentration in the exhaust gases of each of the vehicles show that after adding HHO to the original fuel, the amount of NOx depends on a fueling method. In the SI engines with indirect injection, adding HHO gas to the intake system reduced the NOx concentration. In the Fiat with a carburetor without feedback, the NOx concentration remained practically unchanged but it increased in the CI engines if HHO gas was added to their intake systems.     

Experimental investigation of tetrahydrofuran combustion in homogeneous charge compression ignition (HCCI) engine: Effects of excess air coefficient,engine speed and inlet air temperature

In this study, the effects of tetrahydrofuran (THF) which is nontoxic and generated from renewable environmentally friendly lignocelluloses, and n-heptane/THF blends on combustion, performance and emission characteristics were investigated at various lambda, engine speed and inlet air temperatures. Wide ranges of lambda value and engine speed were investigated and the results were presented in comparison to n-heptane as reference fuel. The combustion parameters such as cylinder pressure, heat release rate, in-cylinder gas temperature, CA10, CA50, thermal efficiency, ringing intensity, maximum pressure rise rate and imep, the performance parameters such as brake torque, power output, specific fuel consumption and HC and CO emissions were determined. Operating range of the HCCI engine was also determined. The results showed that, increasing the lambda value decreased both the in-cylinder pressure and the heat release rate for all test fuels. The addition of tetrahydrofuran led to retard combustion phasing. Thermal efficiency increased about 54% for F60N40 compared to n-heptane at 60 °C inlet air temperature, 1200 rpm engine speed and λ = 2.2. The results also showed that HC and CO emissions increased with the increase of tetrahydrofuran. Furthermore, tetrahydrofuran caused to expand HCCI operating range towards to knocking and misfiring boundaries.     

汽油机怠速工况下HC和CO排放机理的实验研究

本文系统地研究了汽油机怠速工况下排气中ＨＣ和ＣＯ生成的基本规律，重点探讨了燃烧过程与ＨＣ、ＣＯ排放的内在关系。燃烧过程所考虑的因素主要有燃烧完善程度（用累积放热百分比表示），燃烧速率和着火时刻。试验发现燃烧速率对排放的影响较小。在空燃比较高（大于１３）的情况下，采用适当的废气再循环可显著降低排气中ＨＣ的生成量，这为改善现代汽油机怠速工况下的排放水平提供了有效的途径。     

Starting a spark-ignited engine with the gasoline-hydrogen mixture

Because of the increased fuel-film effect and dropped combustion temperature, spark-ignited (SI) gasoline engines always expel large amounts of HC and CO emissions during the cold start period. This paper experimentally investigated the effect of hydrogen addition on improving the cold start performance of a gasoline engine. The test was carried out on a 1.6-L, four-cylinder, SI engine equipped with an electronically controlled hydrogen injection system. A hybrid electronic control unit (HECU) was applied to control the opening and closing of hydrogen and gasoline injectors. Under the same environmental condition, the engine was started with the pure gasoline and gasoline-hydrogen mixture, respectively. After the addition of hydrogen, gasoline injection duration was adjusted to ensure the engine to be started successfully. All cold start experiments were performed at the same ambient, coolant and oil temperatures of 17 °C. The test results showed that cylinder and indicated mean effective pressures in the first cycle were effectively improved with the increase of hydrogen addition fraction. Engine speed in the first 20 start cycles increased with hydrogen blending ratio. However, in later cycles, engine speed varied only a little with and without hydrogen addition due to the adoption of close loop control on engine speed. Because of the low ignition energy and high flame speed of hydrogen, both flame development and propagation durations were shortened after hydrogen addition. HC and CO emissions were dropped markedly after hydrogen addition due to the enhanced combustion process. When the hydrogen flow rate increased from 0 to 2.5 and 4.3 L/min, the instantaneous peak HC emissions were sharply reduced from 57083 to 17850 and 15738 ppm, respectively. NOx emissions were increased in the first 5 s and then reduced later after hydrogen addition.     

Experimental study on lean-burn characteristics of an SI engine with hydrogen/gasoline combined injection and EGR

Hydrogen has shown potential for improving the combustion and emission characteristics of the spark ignition (SI) dual-fuel engine. To reduce the additional NO_x emissions caused by hydrogen direct injection, in this research, the cooperative control of the addition of hydrogen with exhaust gas recirculation (EGR) in the hydrogen/gasoline combined injection engine was investigated. The results indicate that both the addition of hydrogen and the use of EGR can increase the brake mean effective pressure (BMEP). As the α_H2 value increases from 0% to 25%, the maximum BMEP increases by 9%, 12.70%, 16.50%, 11.30%, and 8.20%, respectively, compared with the value without EGR at λ = 1.2. The CA0-10 tends to increase with increases in the EGR rate. However, the effect of EGR in increasing the CA0-10 can be offset by the addition of 15% hydrogen at λ = 1.2. Measurements of the coefficient of variation of the indicated mean effective pressure (COV_IMEP) indicate that the addition of hydrogen can effectively extend the EGR limit. Regarding gaseous emissions, NO_x emissions, after the introduction of EGR and the addition of hydrogen, are lower than those of pure gasoline without EGR. An 18% EGR rate yields a significant reduction in NO_x, reaching maximum decreases of about 82.7%, 77.8%, and 60% compared to values without EGR at λ = 1.0, 1.2, and 1.4, respectively. As the EGR rate increases, the hydrocarbon (HC) emissions continuously increase, whereas a blend of 5% hydrogen can significantly reduce the HC emissions at high EGR rates at λ = 1.4. Finally, according to combustion and emissions, the coupling of a 25% addition of hydrogen with 30% EGR at λ = 1.2, and the coupling of a 20% addition of hydrogen with an 18% EGR rate at λ = 1.4 yield the best results.     

Effect of anodes-cathodes inter-distances of HHO fuel cell on gasoline engine performance operating by a blend of HHO

Control emission pollution associated with oil combustion is a major concern of researchers worldwide. A blend of HHO has been introduced to the combustion elements to reduce emission and drive the combustion reaction toward stoichiometric condition. HHO fuel production unit based on an electrolysis process has been designed and built with an ability to alter Anode-Cathode plate's inter-distances and integrated to Honda G 200 (197 cc single cylinder engine). The gap between the plates was adjusted to 3, 5, 7 and 10 mm. Tests reveal that mixing HHO, air, and gasoline cause an enhancement in engine performance and emissions. The emission tests have been done with varying the engine speed and preserve the electrolyte concentration and temperature. The results show that enhancement in combustion characteristics is strongly affected by the gap between cell plates. The maximum produced power and minimum fuel consumption were associated with the case of 10 mm cathode-anode plates distance where hydrocarbons (HCs) and carbon monoxide emissions have been reduced to about 40% at different operating speeds. Whereas, 5 mm gap case has the highest impact on emission reduction.     

Effect of hydroxy (HHO) gas addition on performance and exhaust emissions in compression ignition engines

In this study, hydroxy gas (HHO) was produced by the electrolysis process of different electrolytes (KOH_(aq), NaOH_(aq), NaCl_(aq)) with various electrode designs in a leak proof plexiglass reactor (hydrogen generator). Hydroxy gas was used as a supplementary fuel in a four cylinder, four stroke, compression ignition (CI) engine without any modification and without need for storage tanks. Its effects on exhaust emissions and engine performance characteristics were investigated. Experiments showed that constant HHO flow rate at low engine speeds (under the critical speed of 1750 rpm for this experimental study), turned advantages of HHO system into disadvantages for engine torque, carbon monoxide (CO), hydrocarbon (HC) emissions and specific fuel consumption (SFC). Investigations demonstrated that HHO flow rate had to be diminished in relation to engine speed below 1750 rpm due to the long opening time of intake manifolds at low speeds. This caused excessive volume occupation of hydroxy in cylinders which prevented correct air to be taken into the combustion chambers and consequently, decreased volumetric efficiency was inevitable. Decreased volumetric efficiency influenced combustion efficiency which had negative effects on engine torque and exhaust emissions. Therefore, a hydroxy electronic control unit (HECU) was designed and manufactured to decrease HHO flow rate by decreasing voltage and current automatically by programming the data logger to compensate disadvantages of HHO gas on SFC, engine torque and exhaust emissions under engine speed of 1750 rpm. The flow rate of HHO gas was measured by using various amounts of KOH, NaOH, NaCl (catalysts). These catalysts were added into the water to diminish hydrogen and oxygen bonds and NaOH was specified as the most appropriate catalyst. It was observed that if the molality of NaOH in solution exceeded 1% by mass, electrical current supplied from the battery increased dramatically due to the too much reduction of electrical resistance. HHO system addition to the engine without any modification resulted in increasing engine torque output by an average of 19.1%, reducing CO emissions by an average of 13.5%, HC emissions by an average of 5% and SFC by an average of 14%.     

Experimental study of the effect of HHO gas injection on pollutants produced by a diesel engine at idle speed

In this study, with the aim of reducing the energy consumption in the production of HHO gas for use in the combustion process of diesel fuel, different modes of gas production were investigated using electrolyzers. According to previous studies, the energy consumption rate of the electrolyzer to produce a high volumetric flow of HHO gas is very high. This high rate will restrict the use of equipment such as high-capacity batteries. The effects of HHO gas injection at the idle speed of the engine at a low temperature were evaluated. Because in this situation, the engine makes high air pollution. The results showed that the percentage of CO, CO2, HC, and NOX gases decreased by 66%, 33%, 38%, and 11%, respectively. On the other hand, the amount of O2 gas in the exhaust increased by 18%. These results were reported for HHO gas injection from 10 to 45 ml/s. The performance of Group Method of Data Handling (GMDH) neural network was desirable in modeling diesel engine pollutants. Because the Root-Mean-Square Error (RMSE) criterion for all evaluated gases is less than 0.32. The GMDH neural network was used for modeling the operation of the diesel engine with HHO supplemental fuel. The GMDH results showed that this artificial network can measure all engine exhaust gases. It can be used as a sensor and virtual simulator for this diesel engine with HHO supplemental fuel.     

Impact of HHO produced from dry and wet cell electrolyzers on diesel engine performance,emissions and combustion characteristics

Water electrolysis produces HHO gas by using sodium hydroxide catalyst. Dry and wet cells designs are applied producing the gas flow rates at 0.5 and 0.75 LPM, respectively. Tests are done in a diesel engine at engine speed variation and full load. Performance, combustion characteristics and emissions investigations of diesel engines using HHO gas from dry and wet cells are performed. HHO gas addition enhances the brake thermal efficiency by 2 and 2.5% but the exhaust gas temperature highest decreases for dry and wet cells are 8 and 10%, respectively about diesel oil. The maximum decreases are evaluated as for CO (15, 22%), HC (31, 39%), NO_x (35, 42%) and smoke emissions (25, 35%), respectively for dry and wet cells about diesel fuel. The improvements in cylinder pressures are 5 and 10%, respectively and the heat release rate enhancements are 4.5 and 6.5%, respectively about pure diesel for dry and wet configurations.     

Effects of second hydrogen direct injection proportion and injection timing on combustion and emission characteristics of hydrogen/n-butanol combined injection engine

Hydrogen and n-butanol are superior alternative fuels for SI engines, which show high potential in improving the combustion and emission characteristics of internal combustion engines. However, both still have disadvantages when applied individually. N-butanol fuel has poor evaporative atomization properties and high latent heat of vaporization. Burning n-butanol fuel alone can lead to incomplete combustion and lower temperature in the cylinder. Hydrogen is not easily stored and transported, and the engine is prone to backfire or detonation only using hydrogen. Therefore, this paper investigates the effects of hydrogen direct injection strategies on the combustion and emission characteristics of n-butanol/hydrogen dual-fuel engines based on n-butanol port injection/split hydrogen direct injection mode and the synergistic optimization of their characteristics. The energy of hydrogen is 20% of the total energy of the fuel in the cylinder. The experimental results show that a balance between dynamics and emission characteristics can be found using split hydrogen direct injection. Compared with the second hydrogen injection proportion (IP2) = 0, the split hydrogen direct injection can promote the formation of a stable flame kernel, shorten the flame development period and rapid combustion period, and reduce the cyclic variation. When the IP2 is 25%, 50% and 75%, the engine torque increases by 0.14%, 1.50% and 3.00% and the maximum in-cylinder pressure increases by 1.9%, 2.3% and 0.6% respectively. Compared with IP2 = 100%, HC emissions are reduced by 7.8%, 15.4% and 24.7% and NOx emissions are reduced by 16.4%, 13.8% and 7.9% respectively, when the IP2 is 25%, 50% and 75%. As second hydrogen injection timing (IT2) is advanced, CA0-10 and CA10-90 show a decreasing and then increasing trend. The maximum in-cylinder pressure rises and falls, and the engine torque gradually decreases. The CO emissions show a trend of decreasing and remaining constant. However, the trends of HC emissions and NOx emissions with IT2 are not consistent at different IP2. Considering the engine's dynamics and emission characteristics, the first hydrogen injection proportion (IP1) = 25% plus first hydrogen injection timing (IT1) = 240°CA BTDC combined with IP2 = 75% plus IT2 = 105°CA BTDC is the superior split hydrogen direct injection strategy.     

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.     

Characterization of the hydroxy fueled compression ignition engine under dual fuel mode: Experimental and numerical simulation

This study investigates the characterization of the hydroxy-diesel fueled compression ignition engine under dual fuel (DF) mode on a stationary modified engine. Hydroxy gas (HHO) is supplied along with diesel at three different flow rates of 0.25, 0.50, and 0.75 lpm. A significant reduction in emission parameters was obtained in carbon monoxide, unburnt hydrocarbon and smoke emission as ~58%, ~60%, and ~49%, respectively under the DF mode (at 0.75 lpm HHO and 10 kg load). However, a slight increment in nitrogen oxides (NO_X) emission is observed due to the O₂ contents in HHO gas. It increases the reaction temperature and results in increasing the NO_X emission. The brake thermal efficiency and brake specific energy consumption also improved and found to be ~6.5% and ~6% at the optimized condition. Combustion analysis shows the rate of pressure rise increased due to quicker combustion and decreased combustion duration. A numerical simulation has been performed to optimize the engine load and HHO flow rate using the Hybrid Entropy-VIKOR technique. In addition, a good agreement has been found between simulation and experimental values for performance and emission parameters. The results can be further improved by optimizing the engine operating parameters, i.e., injection pressure, compression ratio, and injection timing in the near future. Overall it can be concluded the HHO can be considered as a prominent alternative fuel for the CI engine with increased efficiency and lower emissions.     

辛烷值对均质压燃发动机燃烧特性和性能的影响

通过不同比例的正庚烷和异辛烷混合得到不同辛烷值的混合燃料，在一台单缸直喷式柴油机上研究燃料辛烷值对均质压燃发动机燃烧特性、性能和排放特性的影响．研究结果表明，燃料辛烷值增加，着火始点推迟，燃烧反应速率降低，缸内爆发压力降低．燃料辛烷值增高，均质压燃向大负荷工况拓宽，燃料辛烷值较高时，存在极限转速，辛烷值增加，极限转速降低．对于每一工况，存在一个最佳经济性的燃料辛烷值，负荷增大，最佳辛烷值增高；随着燃料辛烷值增高，发动机NO、HC和CO排放增加，尤其是HC排放增加更为明显．对于均质压燃发动机，低负荷工况适合燃用低辛烷值燃料，高负荷工况适合燃用高辛烷值燃料。     

Analysis of onsite HHO gas generation system

Petroleum (Hydrocarbon – HC) based fuels are used for powering automotive and local power generation systems. Hydrocarbons on combustion produce gases such as CO₂, CO, HC and NOx which affect human health as well as environment. Introduction of Hydrogen in Internal Combustion (IC) engine reduces emission and increases the performance. HHO gas which is produced through electrolysis of water can be used instead of hydrocarbon based fuels as the gas contains both Hydrogen as well as oxygen. Due to the challenges in storing Hydrogen, HHO gas is produced onsite through electrolysis process. This article presents the investigation on producing HHO gas through electrolysis onsite. A numerical calculation was done using empirical formula to predict the production of HHO gas. The electrolyser's performance analysis showed that maximum of 0.75 LPM of HHO gas was produced at 80 °C and by supplying 40 A-h. The numerical calculation showed that at the similar working condition the HHO gas produced was 1.3 LPM. The trend of both experiments and model was same for varying the current and rate of generation of HHO gas. This article also presents the effect of parameters such as concentration of electrolyte solution on potential, effect of time and the effect of temperature on production rate. The energy required and the number of modules or units of HHO gas production for real time engine application has been analysed and reported.     

Study of spark ignition engine fueled with methanol/gasoline fuel blends

A 3-cylinder port fuel injection engine was adopted to study engine power, torque, fuel economy, emissions including regulated and non-regulated pollutants and cold start performance with the fuel of low fraction methanol in gasoline. Without any retrofit of the engine, experiments show that the engine power and torque will decrease with the increase fraction of methanol in the fuel blends under wide open throttle (WOT) conditions. However, if spark ignition timing is advanced, the engine power and torque can be improved under WOT operating conditions. Engine thermal efficiency is thus improved in almost all operating conditions. Engine combustion analyses show that the fast burning phase becomes shorter, however, the flame development phase is a little delay.When methanol/gasoline fuel blends being used, the engine emissions of carbon monoxide (CO) and hydrocarbon (HC) decrease, nitrogen oxides (NO_x) changes little prior to three-way catalytic converter (TWC). After TWC, the conversion efficiencies of HC, CO and NO_x are better. The non-regulated emissions, unburned methanol and formaldehyde, increase with the fraction of methanol, engine speed and load, and generally the maximum concentrations are less than 200 ppm. Experimental tests further prove that methanol and formaldehyde can be oxidized effectively by TWC. During the cold start and warming-up process at 5 °C, with methanol addition into gasoline, HC and CO emissions decrease obviously. HC emission reduces more than 50% in the first few seconds (cold start period) and nearly 30% in the following warming-up period, CO reduces nearly 25% when the engine is fueled with M30. Meanwhile, the temperature of exhaust increases, which is good to activate TWC.     

Synergetic effect OF CI engine characteristics when fuelled with neem oil methyl ester enriched with a oxy-hydrogen gas

The Neem-oil methyl ester (NME) produced from transesterification of Neem-oil was mixed with diesel fuel in the share of 10%(N10) and 20%(N20) were used with varying flow rate of oxy-hydrogen gas (HHO) gas at 5%,10% and 15% energy share along with exhaust gas recirculation (EGR) in a 3.7 kW CI engine. Presence of fuel-borne oxygen in NME, facilitates increase in brake thermal efficiency (BTE) at high load related to neat diesel operation. Further the BTE was improved by introducing varying flow rate of HHO gas in order to maintain energy share of 5, 10 and 15% at all loads. The BTE was found as 33.80% and 35.40% for N20 + 10%HHO and N20 + 15%HHO compared to 31.5%, 30.4% and 29.4% for N20, N10 and Neat diesel fuel respectively. Significant emission reduction of CO, CO₂, uHC and smoke opacity were observed during NME + HHO gas operation, but NOx emission was augmented which was controlled using EGR along with further improvement in the engine characteristics.     

An experimental investigation on hydroxy (HHO) enriched ammonia as alternative fuel in gas turbine

Today, the important challenges with the utilization of hydrogen in power-producing applications (internal combustion engines and fuel cells) are its delivery and storage and these create a big hesitation regarding the application safety. Ammonia, which can be regarded as the most promising alternative fuel to hydrogen, provides the possibility of storage in liquid form at low pressures and high temperatures. This study was carried out to investigate how to compensate the drawbacks of using ammonia as the main fuel in a gas turbine by hydrogen and hydroxy-gas enrichment. During the experiments, propane that is standard working fuel of the gas turbine, neat ammonia, as well as a 10 L/min ammonia fuel enriched with 3 L/min, 5 L/min, and 7 L/min hydroxy gas, were utilized. The results show that hydroxy enrichments cause improvements in the performance data as well as emission values due to the absence of any carbon emissions. When the performance outputs are examined, it has been shown that the power values of NH₃ + 3 HHO and NH₃ + 5 HHO fuels are 10.98% and 3.65% lower than propane, whereas NH₃ + 7 HHO fuel produces 4.12% more power, and the desired performance values are reached. It has been also fund that NO_x emissions should be kept under control in addition to the increase in the performance and elimination of the carbon emissions.     

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO_X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO_X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.