Natural Gas Blends Research Articles

Hydrogen underground storage for grid electricity storage: An optimization study on techno-economic analysis

This study performs a techno-economic analysis of hydrogen underground storage systems for grid electricity storage, evaluating their economic viability at the plant scale using dynamic optimization. It explores the feasibility of various system configurations and revenue models in the context of volatile electricity prices and the necessity for multiple revenue streams. The hypothesis tested is that large-scale hydrogen storage, despite its low round-trip efficiency, can be economically viable with the right mix of revenue streams. This study uses scenario-based analysis to assess the impacts of different system configurations, including engaging in time-shifting arbitrage, ancillary service markets and blending hydrogen with natural gas. Results indicate potential annual net cash flows of up to $1.5 million from ancillary services integration and $5.2 million from natural gas blending, contingent on specific system sizes. The study concludes that hydrogen underground storage for grid electricity storage can be profitable, and emphasizes that proper system design and precise electricity price forecasting are crucial for optimizing system performance and economic returns. This research sets the stage for further investigations into the scalability of hydrogen storage systems and their broader implications for grid electricity storage and energy market dynamics.

Techno economic analysis and performance based ranking of 3–200 kW fuel flexible micro gas turbines running on 100% hydrogen, hydrogen fuel blends, and natural gas

Micro gas turbines ranging from 3 to 200 kW are vital for decentralized power generation due to their reliability, rapid load response, and adaptability to 100% hydrogen and hydrogen fuel blends. This paper conducts a techno-economic assessment of MGTs powered by hydrogen, focusing on their environmental, economic, and technical viability. Key factors include the transition from natural gas to hydrogen to achieve net-zero emissions and enhance grid stability. Despite hydrogen's higher initial costs, its declining production costs and cleaner combustion make it a promising alternative. The study utilizes five micro gas turbine models (3, 30, 65, 100, and 200 kW) to evaluate a techno-economic analysis using 100% hydrogen, a 30% hydrogen and 70% natural gas blend, and 100% natural gas as fuels. Technical results are supported by experimental data from the world's first 100% hydrogen-fired micro gas turbine unit in Stavanger, Norway. Standard cost estimations for capital, operation and maintenance, and fuel costs are provided. The study introduces a novel technique for cost estimation and assesses econometric indicators such as net present value, internal rate of return, return on investment, payback period, and cost-benefit analysis. It compares economic scenarios for 2024, 2030, and 2040, highlighting the impact of fuel price volatility and regulatory changes on micro gas turbine techno-economics. Micro gas turbines are ranked using the Technique for Order Preference by Similarity to Ideal Solution-Multi-Criteria Decision Making (TOPSIS-MCDM) method based on their techno-economic performance. The ranking of microturbines based on techno-economic analysis performance is a novel contribution of this paper. Finally, a sensitivity analysis on the five micro gas turbines is carried out by changing the hydrogen fuel price. This research provides a comprehensive framework for stakeholders to make informed investment decisions, ensuring a smooth transition to 100% hydrogen-based power generation. The findings support the adoption of hydrogen and natural gas blends as an interim solution towards achieving a hydrogen economy.

Towards hydrogen gas turbine engines aviation: A review of production, infrastructure, storage, aircraft design and combustion technologies

This study explores the potential of hydrogen gas turbine engines for sustainable aviation, with a particular focus on their development for low subsonic to transonic flight regimes. Hydrogen offers notable advantages, including zero CO2 emissions and high energy density. However, its widespread adoption is prevented by significant challenges in production, infrastructure, storage, aircraft design, and combustion technology. The limited availability of green hydrogen – the global production totaled only 127 kt in 2023, with 76% produced in China - raises concerns about the feasibility of a rapid shift to hydrogen-powered general aviation. Despite numerous pledges for hydrogen adoption in the Western world, major aircraft manufacturers have primarily engaged in marketing activities rather than substantial product innovation. To date, the only hydrogen aircraft demonstrator from this century is the 2012 Boeing Phantom Eye, which utilized modified hydrogen internal combustion engines rather than a gas turbine engine. The only hydrogen aircraft demonstrator with a gas turbine engine was the 1988 hybrid Tupolev Tu-155 which coupled one hydrogen gas turbine engine to other two jet fuel engines. This paper evaluates the current state of hydrogen gas turbine technology, comparing its combustion characteristics with traditional jet fuels and examining various NOx emission control techniques. It also investigates the potential of micro-mix lean combustion and staged combustion to achieve efficient and low-emission hydrogen combustion in gas turbines. Given the more extensive experience with terrestrial gas turbines compared to their aeronautical counterparts, the review includes insights from terrestrial power generation applications. Additionally, it considers hythane - a blend of hydrogen and natural gas - as a transitional solution for significantly reducing CO2 emissions while progressing towards net-zero targets. The review underscores the urgent need for advancements in green hydrogen production, technology, and infrastructure to overcome existing barriers and enable a more sustainable aviation future powered by hydrogen. Importantly, the review emphasizes the need to move beyond mere virtue signaling and make tangible progress toward a hydrogen economy.

Impact of Diluents on Flame Stability With Blends of Natural Gas and Hydrogen

Abstract Two potential decarbonization pathways for natural gas (NG)-fueled gas turbine engines include blending hydrogen (H2) into NG and postcombustion carbon capture. H2 blending changes several combustion properties, including flame speed and stretch sensitivity. The use of post-combustion carbon capture systems is typically facilitated by the implementation of exhaust gas recirculation (EGR), where exhaust gases are injected into the inlet of the engine, increasing carbon dioxide (CO2) concentration at the outlet and, hence, increasing the efficiency of carbon capture technologies. In this work, we explore the impact of H2 blending and EGR on the stability of a swirl-stabilized, central-piloted flame. Mixtures of NG and H2 are tested at a range of different diluent compositions, with oxygen varied from 21% to 15% by volume in the oxidizer. In all cases, a constant adiabatic flame temperature is maintained to mimic the operation of a gas turbine at a given turbine inlet temperature. A variable-length combustor is used for testing, where combustor length is varied to understand the dynamic stability characteristics of the system. Results show that EGR and H2 work in opposition to each other, where higher levels of EGR result in poor flame holding and higher levels of H2 result in better flame holding. Increasing H2 generally increases the amplitude of thermoacoustic instability at each condition, a result of the change in flame position in this particular combustor. Importantly, H2 can be added to NG to improve flame holding without significantly decreasing CO2 levels in the products, showing that H2 blending can be a method for counteracting combustor operability issues that arise from high levels of EGR necessary to improve the efficiency of typical carbon capture systems.

Experimental simulation of H2 coinjection via a high-pressure reactor with natural gas in a low-salinity deep aquifer used for current underground gas storage.

If dihydrogen (H2) becomes a major part of the energy mix, massive storage in underground gas storage (UGS), such as in deep aquifers, will be needed. The development of H2 requires a growing share of H2 in natural gas (and its current infrastructure), which is expected to reach approximately 2% in Europe. The impact of H2 in aquifers is uncertain, mainly because its behavior is site dependent. The main concern is the consequences of its consumption by autochthonous microorganisms, which, in addition to energy loss, could lead to reservoir souring and alter the petrological properties of the aquifer. In this work, the coinjection of 2% H2 in a natural gas blend in a low-salinity deep aquifer was simulated in a three-phase (aquifer rock, formation water, and natural gas/H2 mix) high-pressure reactor for 3 months with autochthonous microorganisms using a protocol described in a previous study. This protocol was improved by the addition of protocol coupling experimental measures and modeling to calculate the pH and redox potential of the reactor. Modeling was performed to better analyze the experimental data. As in previous experiments, sulfate reduction was the first reaction to occur, and sulfate was quickly consumed. Then, formate production, acetogenesis, and methanogenesis occurred. Overall, H2 consumption was mainly caused by methanogenesis. Contrary to previous experiments simulating H2 injection in aquifers of higher salinity using the same protocol, microbial H2 consumption remained limited, probably because of nutrient depletion. Although calcite dissolution and iron sulfide mineral precipitation likely occurred, no notable evolution of the rock phase was observed after the experiment. Overall, our results suggested that H2 can be stable in this aquifer after an initial loss. More generally, aquifers with low salinity and especially low electron acceptor availability should be favored for H2 costorage with natural gas.

Hydrogen Blending in Natural Gas Grid: Energy, Environmental, and Economic Implications in the Residential Sector

The forthcoming implementation of national policies towards hydrogen blending into the natural gas grid will affect the technical and economic parameters that must be taken into account in the design of building heating systems. This study evaluates the implications of using hydrogen-enriched natural gas (H2NG) blends in condensing boilers and Gas Adsorption Heat Pumps (GAHPs) in a residential building in Rome, Italy. The analysis considers several parameters, including non-renewable primary energy consumption, CO2 emissions, Levelized Cost of Heat (LCOH), and Carbon Abatement Cost (CAC). The results show that a 30% hydrogen blend achieves a primary energy consumption reduction of 12.05% and 11.19% in boilers and GAHPs, respectively. The presence of hydrogen in the mixture exerts a more pronounced influence on the reduction in fossil primary energy and CO2 emissions in condensing boilers, as it enhances combustion efficiency. The GAHP system turns out to be more cost-effective due to its higher efficiency. At current hydrogen costs, the LCOH of both technologies increases as the volume fraction of hydrogen increases. The forthcoming cost reduction in hydrogen will reduce the LCOH and the decarbonization cost for both technologies. At low hydrogen prices, the CAC for boilers is lower than for GAHPs; therefore, replacing boilers with other gas technologies rather than electric heat pumps increases the risk of creating stranded assets. In conclusion, blending hydrogen into the gas grid can be a useful policy to reduce emissions from the overall natural gas consumption during the process of end-use electrification, while stimulating the development of a hydrogen economy.

Nox Emissions Assessment of a Multi Jet Burner Operated with Premixed High Hydrogen Natural Gas Blends

Abstract Decarbonization of gas turbine combustion creates a pressing demand for new technical solutions for the combustion process. While switching to hydrogen fuels may solve the problem of carbon emissions and associated pollutants it can also lead to stability issues for swirl-stabilized combustors due to its increased reactivity. However, with jet flame burner systems, the required flashback safety can be achieved with high axial flow velocities even for premixed combustion of 100% hydrogen fuel. The development of such an engineering solution, however, requires significant effort to reach the maturity of today's swirl burners. This study examines the capacity of a premixed multi-tube jet burner to manage the chemical reactivity change over a range of volumetric blends from pure natural gas to pure hydrogen fuel. NOx emissions are measured and analyzed for atmospheric tests. The changes in emissions originate not only from altered combustion chemistry but also from changes in flame shape and turbulence intensity. To get a deeper understanding of the NOx formation process, a low-order model is designed and compared to the experimental data of technically and perfectly premixed combustion tests. Parameter variations of the low-order model are conducted to assess the influences on the NOx emission production of the multi jet burner. The information on the combustion process required for the model is obtained computationally and experimentally. Therefore, flame images are recorded and analyzed.

Laser ignition versus conventional spark ignition system performance for hydrogen-enriched natural gas-air mixtures in a constant volume combustion chamber

This study compares the performance of a laser ignition system vis-à-vis a conventional electrical spark ignition system in a constant volume combustion chamber. A custom-built constant-volume combustion chamber was used to compare the performance of the laser and spark ignition systems. A combination of three lenses in the optical path was used to create laser plasma in the constant volume combustion chamber. Initial chamber pressure and temperature were maintained constant at 4 bar and 150 °C during the experiments. The effect of hydrogen enrichment of compressed natural gas on combustion was assessed for three relative air–fuel mixture strengths (λ: 1.0, 1.2 and 1.4) to compare the performance of both ignition systems. The laser ignition system exhibited superior combustion characteristics to the spark ignition system. The combustion duration of laser ignition was considerably lower than spark ignition. Three hydrogen-enriched natural gas blends (10HCNG, 20HCNG and 40HCNG) were assessed and compared with baseline compressed natural gas. Hydrogen enrichment improved the combustion characteristics, increasing the excess chamber pressure and reducing the combustion duration. Two locations were taken for assessing the performance of the laser ignition system in this study. The first location was the same as the spark from a conventional electrical spark ignition system, and the second was at the centre of the constant volume combustion chamber. The central location of laser ignition showed a higher reduction in the combustion duration than baseline spark ignition and its corresponding laser ignition, indicating its superiority. The ability to choose an ignition location centrally in the engine combustion chamber emerged to be a main advantage of laser ignition systems.

Technical evaluation of electrochemical separation of hydrogen from a natural gas/hydrogen mixture

In this work, we investigate the electrochemical separation of hydrogen from a 10% H2/methane natural gas blend using a single cell experimental setup for electrochemical hydrogen pumping (EHP). Results show that the overall efficiency for hydrogen separation is high, ranging from about 87% at 0.2 A/cm2 to 75% at 0.6 A/cm2. In addition, we develop a zero-dimensional model for the hydrogen separation process including the membrane permeation of H2 as well as CH4, N2, and CO2 as the main components in natural gas. We derive analytical expressions for the permeability of these gases as a function of temperature and membrane humidity using available permeability data. Although the presence of dilutive inert gases poses a challenge, the modelled data indicate that it should be possible to produce fuel cell quality hydrogen using a single hydrogen separation stage. Importantly, this indicates technological feasibility of distributing hydrogen for use in fuel cells through existing natural gas infrastructure. Extension of this research to combined hydrogen separation and compression within the same EHP unit is recommended as future work.

Geochemical impact of biomethane and natural gas blend injection in deep aquifer storage

Biomethane is one of the main renewable gases available today to offset fossil gas and decarbonize the energy system. The EU is seeking to rapidly replace part of the natural gas usually stored in deep saline aquifers by biomethane which contains up to 10000 ppm of O2. This study presents for the first-time assessment of deep aquifers’ resilience to biomethane and natural gas blend injection into two sandstone reservoirs with different mineral paragenesis from the Paris Basin (France). Multiphase reactive transport modeling allowed to evaluate changes in gas and water quality, mineralogy and moreover, to identify major resilience properties of storage facilities necessary to buffer the oxygen reactivity and induced acidification coming from gas–water–rock interactions. In the presence of pyrite, the injected oxygen is consumed during pyrite oxidation and contributes to the acidification of the formation water close to the injection point. However, the injection of 1% mole fraction of CO2(g) contained in the gas blend is found to be the main acidification factor. The analysis of reservoir resilience showed three protection levels of pH buffering capacity, which can effectively mitigate an increase in oxygen content up to 1000 ppm: (i) calcite dissolution, (ii) plagioclase and clay dissolution and (iii) clay sorption capacity. Models predict that the gas blend injection could induce minimal but long-term change in the mineralogy without significantly impacting the global porosity. Overall, both sandstones can preserve the quality of the gas plume despite partial CO2(g) exsolution induced by the geochemical perturbation of the formations. The developed models will be used as a basis for assessment of renewable natural gas storage facilities in the long-term.

Effect of Water Injection on Combustion and Emissions Parameters of SI Engine Fuelled by Hydrogen–Natural Gas Blends

Technologies used in the transport sector have a substantial impact on air pollution and global warming. Due to the immense impact of air pollution on Earth, it is crucial to investigate novel ways to reduce emissions. One way to reduce pollution from ICE is to use alternative fuels. However, blends of alternative fuels in different proportions are known to improve some emissions’ parameters, while others remain unchanged or even worsen. It is therefore necessary to find ways of reducing all the main pollutants. For SI engines, mixtures of hydrogen and natural gas can be used as alternative fuels. The use of such fuel mixtures makes it possible to reduce CO, HC, and CO2 emissions from the engine, but the unique properties of hydrogen tend to increase NOx emissions. One way to address this challenge is to use port water injection (PWI). This paper describes studies carried out under laboratory conditions on an SI engine fuelled with CNG and CNG + H2 mixtures (H2 = 5, 10, 15% by volume) and injected with 60 and 120 mL/min of water into the engine. The tests showed that the additional water injection reduced CO and NOx emissions by about 20% and 4–5 times, respectively. But, the results also show that water injection at the rate of 120 mL/min increases fuel consumption by between 2.5% and 7% in all cases.

Thermodynamic phase equilibria study of Hythane (methane + hydrogen) gas hydrates for enhanced energy storage applications

Hydrogen blending with natural gas has become an effective technique for incorporating the characteristics of natural gas and facilitating the storage and transportation of hydrogen gas. The transportation of hydrogen and natural gas (methane) blend, also referred to as Hythane, presents numerous challenges, advantages, and disadvantages that differ based on the technology employed. The current research showcased a thorough examination of the thermodynamics involved in studying the three phase equilibrium analysis of gas hydrate technology for storing Hythane gas mixtures. Three different Hythane compositions varying in hydrogen percentage were selected, and the isochoric gas hydrate phase equilibria study was performed. The experimental results of phase equilibria and thermodynamic modelling using CPA EOS in software were compared. A similar study was also conducted in the presence of a 5.56 mol % THF solution to understand the reduction in the pressure requirement for the phase equilibria. Results from the mixed Hythane+THF gas hydrate findings suggested stable gas hydrate formation at much lower pressure requirements, increasing the credibility of storing Hythane mixtures in gas hydrates at moderate conditions. The gas compositions for each experiment were analyzed using gas chromatography to evaluate the presence of the desired gas in the hydrate phase. Heat exchange during the gas hydrate dissociation was analyzed using a high pressure differential scanning calorimeter (DSC). The change in the heat release temperature also indicates the stability of the gas hydrate, and with increasing hydrogen gas in the blend, the gas hydrate stability decreased. The Clausius-Clapeyron equation was employed to compute the heat of gas hydrate dissociation, and a comparison was made with the heat of dissociation obtained from the DSC study. The experimental investigations on Hythane gas hydrates were performed to find the hydrogen storage inside the gas hydrate phase and compare it with the previous studies of pure hydrogen hydrates. To demonstrate the Hythane gas transportation, Hythane gas hydrate pellets were formed, followed by their storage in a controlled environment to observeany changes in pressure and temperature. The Hythane gas hydrate pellets demonstrated exceptional stability of Hythane gas presenting an intriguing prospect for utilizing gas hydrate technology in Hythane gas transportation.

Effect of hydrogen blending on the accuracy of smart gas meters

The exploitation of green hydrogen blending with natural gas (NG) is expected to contribute in lowering greenhouse gas emissions and fostering the share of renewable energy sources (RES). The NG infrastructure, in fact, can act as a storage facility for green hydrogen produced from excess RES, also providing flexibility to the electric system. However, the unbalance of the networks and the raise of protection issues for consumers may occur as a consequence of the potential decay of the metrological performance of gas meters operating with natural gas and hydrogen blends. In this paper, the authors present the results of an experimental campaign aimed at analysing the effect of hydrogen blending on the accuracy of smart domestic gas meters. Experimental tests were performed in the laboratory using air, natural gas and gas-hydrogen blends up to 23%vol. The results show no criticalities occur for diaphragm and ultrasonic gas meters, regardless of the hydrogen content. On the other hand, thermal mass gas meters show good reliability when hydrogen blends are within 2%vol, whereas for higher hydrogen contents, reliability is demonstrated only when they are equipped with a specific new design routine capable to address the gas quality changes.

An approach to coupling the gas flow dynamics and thermodynamics of hydrogen solubility in L485ME steel grade for estimation of fracture toughness

The paper presents the problem of coupling the gas flow dynamics in pipelines with the thermodynamics of hydrogen solubility in steel for the estimation of the fracture toughness. In particular, the influence of hydrogen blended natural gas transmission on hydrogen solubility and, consequently, on fracture toughness is investigated with a focus on the L485ME low-alloy steel grade. Hydraulic simulations are conducted to obtain the pressure and temperature conditions in the pipeline. The hydrogen content is calculated from Sievert’s law and, as a consequence, the fracture toughness of the base metal and heat-affected zone is estimated. Experimental data is used to define hydrogen-assisted crack size propagation in steel as well as to a plane strain fracture toughness. The simulations are conducted for a real natural gas transmission system and compared against the threshold stress intensity factor. The results showed that the computed fracture toughness for the heat-affected zone significantly decreases for all natural gas and hydrogen blends. The applied methodology allows for identification of the hydrogen-induced embrittlement susceptibility of pipelines constructed from thermomechanically rolled tubes worldwide most commonly used for gas transmission networks in the last few decades.

Hydrogen separation from hydrogen-compressed natural gas blends through successive hydrate formations

With hydrogen gaining prominence as a future decarbonization tool, the practice of “Hydrogen Blending” – the integration of hydrogen into natural gas pipelines – has swiftly emerged to curb carbon emissions. However, before hydrogen pipelines become widespread, in-depth research into “Hydrogen Deblending” – the separation of hydrogen from HCNG (Hydrogen-Compressed Natural Gas) – is essential to ensure the availability of pure hydrogen when required. In this context, our study introduces an innovative gas separation technique based on clathrate hydrates. Clathrate hydrates are crystalline inclusion compounds in which guest molecules are accommodated within the cage of water-framework constructed by hydrogen bonding. The water-based nature of clathrate hydrates enables a scalable and sustainable process for gas storage and separation. We propose an innovative gas separation system that utilizes successive hydrate formations to store natural gas within hydrates, while enhancing the purity of hydrogen in the vapor phase. Employing in-situ gas chromatography, we analyzed gas compositions at stage 1 of hydrate formation and quantified gas storage capacities (mmol/mol of water) for individual guest species. Our study confirmed that the designed successive hydrate formation could achieve around 79.32% of hydrogen recovery with a purity of 98.73%, demonstrating the viability of hydrate-based separation process.

Promoting the valorization of blast furnace gas in the steel industry with the visual monitoring of combustion and artificial intelligence

The sustainability and decarbonization of processes in the steel industry are enhanced with the valorization of the gas generated during the chemical reactions produced in blast furnaces. However, the combustion of blast furnace gas (BFG) faces the drawback of lower flame stability, which increases the chance of operation shifts towards abnormal conditions and even the flashback or extinction of the flame. Thus, early detection and correction of regime deviations are needed to increase combustion efficiency, for which image-based systems have a high potential. This work focuses on monitoring an industrial furnace for steelmaking processes based on estimating O2 concentration in flue gases using color images captured inside the combustion chamber. An experimental campaign was performed in a 1.2-MW burner to develop the supervision system, using three fuel blends of BFG and natural gas. Images were processed to extract intensity and textural features, which were used to train predictive models based on machine learning algorithms: logistic regression, support vector machines, and artificial neural networks (multilayer perceptron). O2 concentration in flue gases was correctly estimated for at least 97 % of all the test samples and fuel blends. This study shows the potential of image-based systems for the automated control of BFG combustion at the industrial scale.

Ignition Delay Times and Chemical Reaction Kinetic Analysis for the Ammonia–Natural Gas Blends

Ignition Delay Times and Chemical Reaction Kinetic Analysis for the Ammonia–Natural Gas Blends

Effect of NO2 addition on the oxidation kinetics of n-pentane and natural gas blends with C1–C5n-alkanes

This study presents new ignition delay time (IDT) data for NO2 blended multi-component natural gas mixtures with methane as the major component including C2–C5 primary n-alkanes in different concentrations. The data are measured using a high-pressure shock tube and a rapid compression machine at compression pressures of 20 and 30 bar in the temperature range of 715–1480 K for stoichiometric mixtures. This paper builds upon our previous work on the development of a C1–C3/NOx kinetic mechanism and focusses on understanding the interaction chemistry of heavier n-alkane/NOx mixtures by determining the IDT characteristics of various NO2 blended n-C5H12/air combinations with 200, 400 and 1000 ppm concentrations of NO2 present at compression pressures of 10, 20 and 30 bar. The newly measured IDT results and existing experimental data from the literature are used to improve model predictions for the oxidation of n-C4H10/NOx, n-C5H12/NOx, NG2/NOx, and NG3/NOx by updating NUIGMech1.2. The improvement in the performance of GalwayMech1.0 is attributed to updated rate constants for the n-C5H12 + NO2 ↔ Ċ5H11–1, -2, -3 + HONO reactions as well as the inclusion of Ṙ + NO2 ↔ RONO reaction channels. The IDT decreased slightly when 1000 ppm of NO2 is added to n-pentane, which contrasts with propane (C3H8), where there was a significant decrease in the mixture reactivity as reported previously (A. A. E. S. Mohamed, A. B. Sahu, S. Panigrahy, M. Baigmohammadi, G. Bourque, H.J. Curran, The effect of the addition of nitrogen oxides on the oxidation of propane: An experimental and modeling study. Combust. Flame 245 (2022) 112306). This is because the competition between NO2 and O2 for 1-propyl radicals formed by H-atom abstraction from C3H8 decreases mixture reactivity, while in the case of n-C5H12, although NO2 and O2 compete for 1-pentyl radicals, the increase in reactivity is facilitated by the availability of 2-pentyl radicals in the system which also leads to chain branching when they add to O2, unlike 2-propyl (iso-propyl) radicals which ultimately do not lead to chain branching in the oxidation of propane.

Experimental Investigation into the Impact of Natural Gas-Diesel Mixture on Exhaust Emissions and Engine Performance in a Heavy-Duty Diesel Engine with Six Cylinders

In this study, experiments were conducted with a mixture of pure diesel and natural gas. In the experiments, a 6-cylinder heavy-duty diesel engine with an engine displacement of 11,670 cc was used and the engine speed was kept constant at 660 rpm. At 660 rpm engine speed, the maximum torque value reached was 386 Nm. The 386 Nm torque value was accepted as 100% and experiments were carried out at torque ratios of 25, 50, 75 and 100%. In all experiments with natural gas mixture, natural gas was delivered to the combustion chamber at a pressure of 1.5 bar and a flow rate of 1.29 g/sec, pre-mixed with air from the intake manifold. The aim of this study is to investigate the combustion characteristics of pure diesel and natural gas mixtures in a heavy-duty diesel engine. According to the test results, the BTE value of natural gas - diesel blended fuel decreased by 157, 89, 53, 53 and 28% at 25, 50, 75, 100 torque values, respectively, compared to pure diesel. It was observed that at low torque values, natural gas - diesel blended fuel was very inefficient, but as the torque value increased, there were improvements in the BTE value of natural gas - diesel blended fuel, although it could not reach the BTE value of pure diesel. In the experiments with pure diesel, it was determined that the fuel consumption was 127, 68, 38, 17% less than the natural gas - diesel blended fuel at torque values of 25, 50, 75, 100%, respectively. The most significant change in exhaust emissions was observed in CO and UHC emissions. At maximum load, CO and UHC emissions were found to be 4.42 and 4.5 g/kWh for pure diesel and 19.9 and 11.9 g/kWh for natural gas blend, respectively.

Experimental investigation of various burner heads in residential gas stoves tested with hydrogen and natural gas blends

The current study is designed to investigate the effect of five different burner head geometries of gas stoves. The amounts of heat required for boiling 380 grams of water in a pot for a stove for these several burner heads are measured. The flow rates are set to be 3 L/min and 6 L/min for experimental tests. These experimental results show that the burner head with three lateral sets of holes and two circular sets of holes at the top gives the minimum heating time when burning natural gas alone. Once the hydrogen-natural gas mixture is used, the burner head with one lateral and three top circular sets of holes shows the best performance among others regarding heating time. The effect of the flow rate increase is also investigated. Once the flow rate doubles, the burner head with three lateral sets of holes offers the best performance. Based on the findings of the experiments, it can be said that burner heads with lateral sets of holes operate better than other geometries. When natural gas is utilized as fuel, it is observed that the burner head with three lateral sets of holes and two circular sets of holes at the top provided a 12% reduction in heating time compared to the conventional burner head. For the natural gas and hydrogen blends, the conventional burner head achieves the best in terms of heating time.