Hydrogen Mixing Ratio Research Articles

Investigation on the methane emissions from permeation of urban gas polyethylene pipes under the background of hydrogen-mixed natural gas transportation

Methane, a more potent greenhouse gas than carbon dioxide, aggravates the greenhouse effect of ecological environment through its emissions. When transporting hydrogen-mixed natural gas through urban polyethylene pipes, methane will be emitted due to the permeation characteristic of polyethylene pipe material. Therefore, it is crucial to pay attention to the methane emissions from permeation of polyethylene pipes for protecting the environment and climate. In this paper, the solubility and diffusion coefficients of methane within hydrogen-mixed natural gas in polyethylene pipe materials are calculated through the Monte Carlo method and molecular dynamics simulation to determine the permeation coefficient of methane. Simultaneously, the methane emissions and equivalent carbon dioxide emissions of the hydrogen-mixed natural gas in polyethylene pipes are investigated. Results indicate the methane solubility coefficient decreases with increasing temperature and hydrogen mixing ratio. The methane diffusion and permeation coefficients increase with the rising temperature and pressure, and decreasing hydrogen mixing ratio. The pressure exerts minor influence while the temperature and hydrogen mixing ratio have more significant impact. That is, the lower the temperature and the higher the hydrogen mixing ratio, the less methane emissions caused by permeation. Therefore, the effective reduction of methane emissions can be achieved by adding the insulation layer to mitigate the impact of high temperature and increasing the hydrogen mixing ratio. For example, for the polyethylene pipe with the operating pressure of 4 bar and the size specification of SDR11, when the temperature drops from 300 K to 260 K, the methane emissions of hydrogen-mixed natural gas with hydrogen mixing ratios of 0 vol%, 20 vol%, 50 vol% and 80 vol% will be drastically reduced by 73.3%, 74.4%, 77.2% and 78.5% respectively, and when 20 vol%∼80 vol% hydrogen are mixed in the natural gas at 260 K, 300 K and 310 K, the methane emissions will be effectively reduced by 26.7%∼85.6%, 23.3%∼82.1% and 23.9%∼82.4% respectively. The findings of this study can serve as guidance for reducing the methane emissions from permeation of polyethylene pipes transporting hydrogen-mixed natural gas.

9E heavy-duty gas turbine ammonia-hydrogen mixture combustion characteristics and NOx emission characteristics research

In this study, we used the numerical simulation tool FLUENT to numerically simulate the combustion of ammonia-hydrogen fuel in the combustion chamber of a 9E heavy-duty gas turbine, and analysed the effects of different hydrogen blending ratios on the stability of ammonia combustion and NOx emissions. We found that an increase in the hydrogen mixing ratio in the fuel during the ammonia-hydrogen mixture combustion process contributes to the reduction of NOx emissions and has a positive effect on combustion stability.

Combustion instability characteristics via fuel nozzle modification in a hydrogen and natural gas Co-firing gas turbine combustor

In this study, three premixed swirl gas turbine nozzles with different fuel injection hole sizes were designed to optimize combustion characteristics influenced by changes in the hydrogen mixing ratio. Experiments involved increasing the hydrogen volume fraction of the fuel from 0 to 60%. The amount of fuel supplied through the pilot flow was increased to suppress combustion instability. The OH* chemiluminescence technique was introduced to analyze flame structure. To understand combustion instability, time delay and time-delay distribution were derived from flame structure analysis and applied to the 1D thermoacoustic model. The results indicated that the amount of fuel required for pilot injection with increasing hydrogen ratio varied with fuel hole size. It was also observed that changes in fuel hole size significantly affected flame characteristic length. Findings from the 1D thermoacoustic analysis confirmed that fuel hole size variation altered combustion instability characteristics by influencing time delay and time-delay distribution variation.

Kinetic insights into ammonia-hydrogen doped ignition and emission assisted by nanosecond pulsed discharge

Non-equilibrium plasma is applied for the first time to ignite the ammonium-hydrogen mixture and reduce the NOx/N2O emission with effect in this work. Gas chromatography (GC) experiments as well as a detailed kinetic model, including neutral molecules, free radicals, charged particles, vibratory excited states, and electron excited states, are integrated to investigate the kinetic process of ammonia-hydrogen doped ignition and NOx/N2O emission facilitated by nanosecond pulsed discharge. The numerical model closely matches the GC-measured values of NH3 consumption, H2 increase, and N2O production. Pathway fluxes of important species and sensitivity analysis of ignition delay time reveal that the addition of non-equilibrium plasma has an obvious promotion effect on ammonia and hydrogen-doped oxidation and ignition. The initial ignition temperature significantly impacts the ignition delay time, with a more pronounced plasma-promotion effect observed at lower temperatures. Conversely, as the hydrogen mixing ratio increases, the ignition delay time decreases, yet the generation of NO and N2O increases. This is attributed to the heightened production of H and NH through elementary reactions such as NH3+HNH2+ H2, H + O2O + OH, and OH + H2H + H2O. Nevertheless, NO and N2O emissions are reduced by 1-2 orders of magnitude with plasma assistance compared to auto-ignition. The reduction in NO emissions can be attributed to increased consumption in the pathway of NO + NH2N2 + H2O and decreased formation in the pathways of HNO + O2HO2 + NO and NH + NON2O + H. Additionally, it was discovered that the electron attachment dissociation reaction e + N2O → O− + N2 predominantly contributes to the reduction of N2O. These research findings significantly contribute to advancing our understanding of the kinetics involved in ammonia-hydrogen doped ignition and emissions, particularly with plasma assistance, for potential engine applications.

Numerical investigation of CH4/H2/air micro-mixing combustion flow in a micro gas turbine combustor with different head-end structures

In order to investigate the premixed combustion characteristics of CH4/H2/air in a micro-mixing combustor, the effects of different micro-mixing head-ends (HE1, HE2, HE3) and hydrogen mixing ratios on the temperature distribution, heat transfer process, emission characteristic, flames shape are analyzed. The results show that compared with swirl head-end combustion, the micro-mixing combustion performance is better. Among the three head-ends, HE3 has the best combustion characteristics and stable flames. The temperature distribution in the high-temperature zone is uniform, and low-temperature zone is concentrated near the jet, which can suppress the flashback. The velocity and temperature gradient near the central axis of jet streams show a strong synergistic effect. The flames are plume shaped and flames stability is mainly influenced by the H2 combustion process. Increasing the jet diameter, decreasing the jet spacing and increasing the hydrogen mixing ratio all contribute to the flames stability, but these three methods can stabilize the flames by affecting fluid Reynolds number, interaction between small flames and combustion rate, respectively. Moreover, small jet diameter and high hydrogen mixing ratio can reduce OTDF, which contributes to improve outlet temperature uniformity.

Experimental and theoretical investigations into overpressure during confined space explosions of methane-hydrogen mixture

This study aimed to deeply explore combustion and explosion behaviors within confined spaces fueled by methane-hydrogen blends. By experimenting in a 55 m³ chamber, it examined how different hydrogen mixing ratios (5%, 10%, 15%, and 30%) affect flame spread and overpressure buildup at an equivalence ratio of 1.1. Results showed that two main flame patterns emerge during venting: mushroom clouds and jet flames. Higher hydrogen percentages cause mushroom clouds to form earlier and grow larger; notably, a 30% blend produces a cloud 12% quicker than a 10% blend, reaching a maximum radius of about 2.7 m. Three types of overpressure were identified: Popen (venting structure opening), Pext (external explosion), and Phel (Helmholtz oscillations). Both Pext and Phel rise with increasing hydrogen content. At each blend level, Pext peaks at 1.87–6.42 kPa, while Phel ranges from 5.86 to 20.65 kPa. Pext plays a crucial role in peak overpressure during venting, particularly relevant for ventilation design considerations. To predict Pext, the study tested three engineering models and found that Taylor's spherical piston theory provided the closest match to experimental data, with a maximum error under 30% compared to other models. In summary, this research offers essential theoretical knowledge and practical evidence for designing safer ventilation and explosion relief systems for facilities handling methane-hydrogen mixtures in the process industry.

A numerical study on hydrogen blending in natural gas pipeline by a T-Pipe

In order to study the flow blending and transporting process of hydrogen that injects into the natural gas pipelines, a three-dimensional T-pipe blending model is established and the flow characteristics are investigated systematically by the large eddy simulation (LES). Firstly, the mathematical formulation of hydrogen-methane blending process is provided and the LES method is introduced and validated by a benchmark gas blending model having experimental data. Subsequently, the T-pipe blending model is presented, and the effects of key parameters, such as the velocity of main pipe, hydrogen blending ratio, diameter of hydrogen injection pipeline, diameter of main pipe and operating pressure on the hydrogen-methane blending process, are studied systematically. The results show that, under certain conditions, the gas mixture will be stratified downstream of the blending point, with hydrogen at the top of the pipeline and methane at the bottom of the pipeline. In the no-stratified scenario, the mixing distance increases at lower hydrogen mixing ratio and larger diameter of the hydrogen injection pipe or the main pipe. Finally, based on the numerical results, the underlying physics of the stratification phenomenon during the blending process are explored and an indicator for stratification is proposed using the ratio between the Reynolds numbers of the natural gas and hydrogen.

Numerical investigation on knock intensity, combustion, and emissions of a heavy-duty natural gas engine with different hydrogen mixing strategies

With the continuous development of hydrogen energy technology, mixing hydrogen has become a potential method to enhance the performance of natural gas engines and reduce emissions. Aiming to offer guidance for optimizing strategies for mixing hydrogen from the perspectives of knock control and thermal efficiency enhancement, a three-dimensional model of a commercial heavy-duty natural gas engine is constructed based on the actual boundary conditions from a high load bench test. In this study, simulations were conducted under conditions where the hydrogen volume fraction ranged from 0% to 40%. The study explored the effects of two injection strategies, port fuel injection of hydrogen-enriched natural gas (PFI) and port fuel injection of natural gas combined with direct injection of hydrogen into the cylinder (PFI + DI), on engine knocking, performance, and emissions. Results indicate that for various injection strategies, there is an increasing trend in knock intensity (KI) with the higher hydrogen mixing ratio. When the hydrogen volume fraction exceeds 20%, the timing of direct hydrogen injection significantly affects KI. This effect is mainly caused by the distribution of unburned hydrogen at the knock onset crank angle (KOCA). Compared to other injection strategies, the PFI + DI strategy when the direct hydrogen injection time at 120°CA BTDC results in a high concentration of hydrogen near the spark plug at the ignition moment, combined with good mixture uniformity in the cylinder. This leads to the shortest CA0-10 and CA10-90, and achieves a maximum indicated thermal efficiency (ITE) of 44.68% under 20% hydrogen volume fraction. Compared to the original natural gas engine, the ITE increased by 2.9% and the NOx emissions increased by 166%, while the HC and CO emissions decreased by 88% and 53%.

Influence of hydrogen blending on the operation of natural gas pipeline network considering the compressor power optimization

Blending hydrogen into the existing natural gas pipeline network is regarded as the most potential transportation mode on the utility-scale. However, the impact of hydrogen on the operation performance of the pipeline remained unclear. This paper analyzes the economic and environmental performance of natural gas pipeline under different hydrogen blending ratios and different hydraulic boundary conditions. In order to reduce the operation costs and carbon emissions in each condition, this paper establish a non-linear optimization model to get the new operation plan of the pipeline system. Further, in order to characterize different boundary conditions of the system, four scenarios, namely, the baseline scenario (BS), the setpoint of flow rate scenario (SF), the setpoint of pressure (SP), and the setpoint of heat flow rate (SH) are proposed in this paper. Two studied cases demonstrated that: (1) the original compressor for natural gas can adapt to a hydrogen blending without change the type of compressor. (2) The optimization model has significant potential in reducing the economic cost and carbon emissions of the system with an average decrease of 11.48%. (3) For every 1% of hydrogen added, the annual operating cost of the system is reduced by $0.73 million (3.29%) in SF, 0.017 million (0.08%) in SP, or increased by $1.67 million (7.50%) in SH. Moreover, the annual carbon emission is reduced by 0.38 kt (3.53%) in SF, 0.047 kt (0.44%) in SP, or increased by 0.76 kt (7.14%) in SH. However, when the hydrogen mixing ratio is more than 8%, the contrary trend may occur. (4) The maximum blending ratio at different points of the multi-source pipeline network are physically interdependent. The paper proposed an optimization model for the 2-E analysis of the pipeline and can provide theoretical guidance for the further application of this transportation mode.

Numerical simulation of the transport and thermodynamic properties of imported natural gas injected with hydrogen in the manifold

Blending hydrogen with natural gas (NG) is an efficient method for transporting hydrogen on a large scale at a low cost. The manifold at the NG initial station is an important piece of equipment that enables the blending of hydrogen with NG. However, there are differences in the components and component contents of imported NG from different countries. The components of hydrogen-blended NG can affect the safety and efficiency of transportation through pipeline systems. Therefore, numerical simulations were performed to investigate the blending process and changes in the thermodynamic properties of four imported NGs and hydrogen in the manifold. The higher the heavy hydrocarbon content in the imported NG, the longer the distance required for the gas to mix uniformly with hydrogen in the pipeline. Hydrogen blending reduces the temperature and density of NG. The gas composition is the main factor affecting the molar calorific value of a gas mixture, and hydrogen blending reduces the molar calorific value of NG. The larger the content of high-molar calorific components in the imported NG, the higher the molar calorific value of the gas after hydrogen blending. Increasing both the temperature and hydrogen mixing ratio reduces the Joule-Thomson coefficient of the hydrogen-blended NG. The results of this study provide technical references for the transport of hydrogen-blended NG.

Ultrasonic gas flow metering in hydrogen-mixed natural gas using Lamb waves

Hydrogen mixing in existing natural gas pipelines efficiently achieves large-scale, long-distance, and low-cost hydrogen delivery. The physical properties of hydrogen and natural gas differ significantly. Hydrogen-mixed natural gas modifies the flow state and thermodynamic properties of the original natural gas in the pipeline. Hydrogen-mixed natural gas can lead to increased errors in ultrasonic flow metering because of the high sound speed and low density of hydrogen. Ultrasonic flowmeter installation distances need to be re-determined. In this study, a Lamb wave non-contact ultrasonic gas flow meter is used to measure the flow of hydrogen-mixed natural gas in a T-type pipeline. The greater the hydrogen mixing ratio, the higher the flow rate of the branch pipeline, and the shorter the installation distance of the ultrasonic flow meter, for example, 10% at 150D, 20% at 110D, and 30% at 20D. The time-difference method with high accuracy and broad applicability is used to calculate the flow rates of COMSOL simulated values. The errors between COMSOL simulation and theoretical flow rates at the shortest installation distance downstream do not exceed 3%. The errors at the position where the mixing uniformity is 80% are significantly higher than those at the shortest installation distance, and the maximum error is about 7.7%. The COMSOL simulation results show the feasibility and accuracy of ultrasonic gas flow metering of hydrogen-mixed natural gas.

Experimental and kinetic investigation of the explosive behavior and free radical spectroscopic characteristics of hydrogen/propane mixed gas

A detailed investigation of the explosion mechanism of hydrogen (H2) - propane (C3H8) mixture gas is the prerequisite for effective prevention of its explosion. This study delved into the explosion pressure and the spectral intensity of free radicals within the H2-C3H8 mixture, conducting a comprehensive investigation of reaction kinetics to elucidate reaction rates, elementary reaction sensitivity, and reaction path. Our findings unveiled a relationship between hydrogen augmentation and heightened explosion pressure, particularly when the hydrogen mixing ratio exceeded 80.0%, and the explosion index reached to St3 level, thereby indicating an exceeding safety risk. Moreover, a discernible augmentation was observed in the spectral intensities of H•, OH•, and O• radicals in tandem with an increased hydrogen mixing ratio. Notably, a linear correlation emerged between the explosion pressure and the spectral intensities of these free radicals. R1: H•+O2 =O•+OH• was the most important reaction step. As the ignition starts, H2 burns prior to C3H8, giving rise to the generation of H• radicals. These H• radicals, in turn, actively participate in the dehydrogenation of C3H8, effectively catalyzing the overall chemical reaction. These results can provide potent scientific support and guidance for the prevention and management of H2-C3H8 explosions.

High-frequency, continuous hydrogen observations at Mace Head, Ireland from 1994 to 2022: Baselines, pollution events and ‘missing’ sources

This study analysed just under three hundred thousand 40-min hydrogen observations taken at the Mace Head baseline station on the Atlantic Ocean coastline of Ireland between 1994 and 2022. Advection of European polluted air masses to Mace Head brought elevated hydrogen mixing ratios. Annual mean European excess mixing ratios were between 2 and 4 ppb above baseline in the 1990s but have steadily declined to about 0.2 ppb in 2021, with an e-folding time of 10 years. European excess carbon monoxide mixing ratios declined in an analogous manner, confirming the cause of the declines in both hydrogen and carbon monoxide as the fitting of exhaust gas catalysts to petrol-engined motor vehicles. The annual mean baseline hydrogen mixing ratios were constant over the 1994–2010 period, averaging about 513 ppb, before an upwards trend set in bringing the annual mean up to 532 ppb in 2021. Monthly baseline mixing ratios exhibited a seasonal cycle with an average spring maximum of 531 ppb and an autumn minimum of 497 ppb. Differences between the monthly means and the 1995–2010 averages were constant up to December 2015 when an anomalous growth trend of 2–4 ppb yr−1 set in. A two-hemisphere two-box model was used to describe the hydrogen budget over the 1995–2022 period. This model highlighted that a ‘missing’ source was required to explain the anomalous growth in the Mace Head observations from 2010 onwards. Six potential candidates for this ‘missing’ source were characterised. However, there is a dearth of hydrogen observations with which to identify the real ‘missing’ source with any certainty. The anomalous growth in hydrogen since 2010 reported here may feasibly be the first evidence of the widespread seepage of natural hydrogen into the atmosphere.

Experimental and machine learning studies of thermal impinging flow under ceiling induced by hydrogen-blended methane jet fire: Temperature distribution and flame extension characteristics

Hydrogen-blended natural gas has a winged used in such thermal and combustible systems, the ceiling thermal characteristics have important parameters of impinging jet configurations. In this paper, a series of experiments were carried out to study the ceiling flame extension characteristics and temperature profile in a thermal impinging flow of methane jet diffusion flame with hydrogen addition. It was found that: for the given volume flow rate of methane fuel, the ceiling temperature increases although ceiling flame extension area (length) decreases, with the volume flow of hydrogen mixing ratios increasing. Then, a physical and mathematical model, combined influence of flame shape hypothesis based on physically the unburnt fuel, hydrogen addition, heat release rate, the effects of source-ceiling height and nozzle diameter is estimated to predict the flame extension area of methane jet diffusion flames with different hydrogen mixing ratios. Moreover, the fire plume temperature between buoyant plume and intermittent flame increased with the increase in hydrogen addition due to the fire plume temperature increased. The temperature profile models of the ceiling jet are proposed for methane diffusion flames with different hydrogen mixing ratios. Furthermore, to perform the calculation quickly and facilitate rapid thermal engineering design, this paper used machine learning methods (GABP neural network) to derive the volume flow rate of gas leak from the temperature data of the ceiling detected by thermocouples. The results show that the AI prediction for the heat release rates has a good correlation with the verification experimental value. The results of this paper may demonstrate the potential for industrial combustion systems and fire safety engineering applications of methane jet diffusion flame with hydrogen addition.

Exploration of critical hydrogen-mixing ratio of quenching methane/hydrogen mixture deflagration under effect of porous materials in barrier tube

To improve the safety of the methane/hydrogen mixture pipeline network, The experimental deflagration quenching behavior of porous materials on hydrogen mixed methane in barrier tubes was studied, the influence of the hydrogen mixing ratio on the quenching results of porous materials and the transient change of overpressure was discussed, the critical quenching hydrogen mixing ratio of porous materials was explored. Results show that the hydrogen mixing ratio has a significant effect on the quenching results of porous materials. According to the different quenching results of porous materials under different hydrogen mixing ratios, the successful quenching zone (φ<19%) and the quenching failure zone (φ ≥ 19%) can be divided. It can be determined that the critical quenching hydrogen mixing ratio is φ = 19%. The critical quenching speed is 33.0 m/s. When the porous material is coupled with hydrogen mixing, the pressure curve appears as a “multi-peak” phenomenon, and the maximum pressure peak is generated by the “multi-peak” game. If the hydrogen mixing ratio is greater than the critical quenching hydrogen mixing ratio, it may bring about the uncertainty of the maximum pressure peak and increase the unpredictability of the explosion hazard to the gas pipeline network. Therefore, reasonable hydrogen mixing is conducive to improving the safety of methane/hydrogen mixture pipeline network transportation. The research results could provide an important reference for the engineering application of methane/hydrogen mixture flame arrester design and the selection of safe hydrogen concentration.

Accounting for non-ideal mixing effects in the hydrogen-helium equation of state

Context. The equation of state for hydrogen and helium is fundamental for studying stars and giant planets. It has been shown that because of interactions at atomic and molecular levels, the behaviour of a mixture of hydrogen and helium cannot be accurately represented by considering these elements separately. Aims. This paper aims at providing a simple method to account for interactions between hydrogen and helium in interior and evolution models of giant planets. Methods. Using on the one hand ab initio simulations that involve a system of interacting hydrogen and helium particles and pure equations of state for hydrogen and helium on the other, we derived the contributions in density and entropy of the interactions between hydrogen and helium particles. Results. We show that relative variations of up to 15% in density and entropy arise when non-ideal mixing is accounted for. These non-ideal mixing effects must be considered in interior models of giant planets based on accurate gravity field measurements, particularly in the context of variations in the helium-to-hydrogen ratio. They also affect the mass-radius relation of exoplanets. We provide a table that contains the volume and entropy of mixing as a function of pressure and temperature. This table is to be combined with pure hydrogen and pure helium equations of state to obtain an equation of state that self-consistently includes mixing effects for any hydrogen and helium mixing ratio and may be used to model the interior structure and evolution of giant planets to brown dwarfs. Conclusions. Non-linear mixing must be included in accurate calculations of the equations of state of hydrogen and helium. Uncertainties on the equation of state still exist, however. Ab initio calculations of the behaviour of the hydrogen-helium mixture in the megabar regime for various compositions should be performed in order to gain accuracy.

Adiabatic laminar burning velocities and NO generation paths of NH3/H2 premixed flames

NH3/H2 is an important hydrogen fuel without carbon emissions. In order to know the fundamental flame characteristics of NH3/H2, the adiabatic laminar burning velocity (SL,0) and overall activation energy (Ea) were measured simultaneously by the flat flame method. Four combustion mechanisms were evaluated to clarify the NO generation paths. It was found that SL,0 shows a monotonic nonlinear increase from 10.69 cm/s to 39.99 cm/s with the increasing of equivalent ratio (Φ = 0.6–1.0) and hydrogen mixing ratio (0.2–0.5 vol%). The four mechanisms have a good prediction for SL,0, but an unsatisfactory prediction for Ea. Among them, S-Mech has the best prediction for SL,0 and Ea. Detailed kinetic analysis shows that NNH-reaction (R700, R795, and R801 in S-Mech) simultaneously play an important role in SL,0 and NO generation. Under lean conditions, NO generation is mainly related to H2NO →OH HNO →HO2 NO, and NO reduction is mainly from NO converted to NNH, which is related to NHi generated by NH3 dehydrogenation. This work identified critical reactions of NO generation and systematically explained the path tendency of NH3 combustion at lean conditions.

Transportation of Mixed Hydrogen Gas in Buried Pipelines in Permafrost Areas

The application of existing gas transmission pipelines to deliver hydrogen-blended natural gas is the most operable method among many delivery methods. Hydrogen-blended natural gas with different hydrogen-blending ratios after passing through the throttling element is not the same. Using FLUENT to analyze the temperature variation after the Joule–Thomson effect for 0%, 5%, 10%, 20%, and 30% hydrogen mixing ratios. Workbench is used to analyze the soil temperature field around the pipeline and the stress displacement of the buried pipeline in the permafrost zone under different hydrogen mixing ratios. The analysis revealed that as the hydrogen mixing ratio increases, the temperature of the same point gradually increases after the Joule–Thomson effect, the low-temperature area around the buried pipe is gradually replaced by the high-temperature area, and the stress of the buried straight pipe also gradually decreases; while the maximum stress of the pipe initially decreases and then increases, and the displacement has no obvious change.

Effects of hydrogen mixing ratio on combustion and emissions of natural gas‐diesel dual fuel engine with high natural gas substitution rate

AbstractIn order to explore the feasibility of natural gas (NG)/diesel dual‐fuel engine with high NG substitution rate under medium and low load, the effects of hydrogen (H2) on the performance and emissions of the engine are studied numerically. The baseline engine is a four‐cylinder turbocharged diesel engine, which is modified into a diesel‐Natural Gas‐Hydrogen ternary fuels engine with port‐injected H2 and NG fuels and direct‐injected diesel fuel. The simulation is performed using GT‐Power software, and numerical results are validated with the experimental data. The percentage of diesel fuel is set at 10% and 20% (by energy). The engine speed decreases from high speed to medium speed and finally to low speed. The engine load decreases from medium load to low load. The H2 mixing ratio increases from 10% to 50%. The results show that, with the increase of H2 mixing ratio, the peak cylinder pressure (PCP), the peak cylinder temperature (PCT), the heat release rate (HRR) and the maximum pressure rise rate (MPRR) increase, while the indicated thermal efficiency (ITE) decreases under all working conditions. Among them, the MPRR increases by 4%~13% at medium load and 1%~2% at low load, but it does not exceed 0.6 MPa/ (°) CA. The indicated thermal efficiency decreases by 1%~4% at medium and low load. In terms of emissions, the carbon monoxide (CO) and the hydrocarbons (HC) decrease by 34%~43%, but the nitrogen oxide (NOX) increases by 58%~73%.

Numerical investigation of the hydrogen swirl combustion flow in a micro gas turbine burner

The influence of swirl angle and hydrogen mixing ratio on the performance of micro gas turbine combustor is discussed by numerical simulation based on computational fluid dynamics (CFD) method, the parameters such as combustion characteristics and pollutant emissions are analyzed. The realizable k-epsilon model is adopted for turbulence simulation, the combustion model is general finite rate model. The results indicated that increasing swirl number reduces the temperature and NO emission. As hydrogen content in the fuel increases, flame length is slightly shortened, temperature in the combustion chamber rises, and temperature distribution becomes more uniform, NO emission at central axis becomes highly, while CO2 and CO emissions decrease. When hydrogen mixing ratio is 50%, the maximum NO emission is about 3 times that of pure methane combustion, and CO2 mass fraction is reduced by 43.9%, moreover, outlet CO emission is reduced by nearly 70%. The hydrogen mixing ratio has a greater impact on pollutant emissions, the sensitivity level of NO and CO emissions to hydrogen mixing ratio reaches 0.25 and 0.39 respectively. As hydrogen mixing ratio and swirl number increases, pressure loss grows, and average turbulent kinetic energy on central plane gradually rises, mainly in outlet region and recirculation zone. Increasing swirl number makes the synergy better, but hydrogen mixing has little effect on the synergy distribution.