scholarly journals Hydrogen Addition to Natural Gas in Cogeneration Engines: Optimization of Performances Through Numerical Modeling

2021 ◽  
Vol 7 ◽  
Author(s):  
Michela Costa ◽  
Daniele Piazzullo ◽  
Alessandro Dolce
Keyword(s):  
Natural Gas ◽  
Numerical Study ◽  
Pressure Rise ◽  
Pollutant Emissions ◽  
Lower Amount ◽  
Combustion Model ◽  
Exhaust Gases ◽  
Hydrogen Addition ◽  
Mixture Density ◽  
Brake Power

A numerical study of the energy conversion process occurring in a lean-charge cogenerative engine, designed to be powered by natural gas, is here conducted to analyze its performances when fueled with mixtures of natural gas and several percentages of hydrogen. The suitability of these blends to ensure engine operations is proven through a zero–one-dimensional engine schematization, where an original combustion model is employed to account for the different laminar propagation speeds deriving from the hydrogen addition. Guidelines for engine recalibration are traced thanks to the achieved numerical results. Increasing hydrogen fractions in the blend speeds up the combustion propagation, achieving the highest brake power when a 20% of hydrogen fraction is considered. Further increase of this last would reduce the volumetric efficiency by virtue of the lower mixture density. The formation of the NOx pollutants also grows exponentially with the hydrogen fraction. Oppositely, the efficiency related to the exploitation of the exhaust gases’ enthalpy reduces with the hydrogen fraction as shorter combustion durations lead to lower temperatures at the exhaust. If the operative conditions are shifted towards leaner air-to-fuel ratios, the in-cylinder flame propagation speed decreases because of the lower amount of fuel trapped in the mixture, reducing the conversion efficiencies and the emitted nitrogen oxides at the exhaust. The link between brake power and spark timing is also highlighted: a maximum is reached at an ignition timing of 21° before top dead center for hydrogen fractions between 10 and 20%. However, the exhaust gases’ temperature also diminishes for retarded spark timings. Lastly, an optimization algorithm is implemented to individuate the optimal condition in which the engine is characterized by the highest power production with the minimum fuel consumption and related environmental impact. As a main result, hydrogen addition up to 15% in volume to natural gas in real cogeneration systems is proven as a viable route only if engine operations are shifted towards leaner air-to-fuel ratios, to avoid rapid pressure rise and excessive production of pollutant emissions.

scholarly journals Laminar Burning Velocities of Hydrogen-Blended Methane–Air and Natural Gas–Air Mixtures, Calculated from the Early Stage of p(t) Records in a Spherical Vessel

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7556
Author(s):  
Maria Mitu ◽  
Domnina Razus ◽  
Volkmar Schroeder
Keyword(s):  
Natural Gas ◽  
Initial Conditions ◽  
Numerical Study ◽  
Early Stage ◽  
Linear Trend ◽  
Burning Velocity ◽  
Pressure Rise ◽  
Spherical Vessel ◽  
Practical Applications ◽  
Hydrogen Addition

The flammable hydrogen-blended methane–air and natural gas–air mixtures raise specific safety and environmental issues in the industry and transportation; therefore, their explosion characteristics such as the explosion limits, explosion pressures, and rates of pressure rise have significant importance from a safety point of view. At the same time, the laminar burning velocities are the most useful parameters for practical applications and in basic studies for the validation of reaction mechanisms and modeling turbulent combustion. In the present study, an experimental and numerical study of the effect of hydrogen addition on the laminar burning velocity (LBV) of methane–air and natural gas–air mixtures was conducted, using mixtures with equivalence ratios within 0.90 and 1.30 and various hydrogen fractions rH within 0.0 and 0.5. The experiments were performed in a 14 L spherical vessel with central ignition at ambient initial conditions. The LBVs were calculated from p(t) data, determined in accordance with EN 15967, by using only the early stage of flame propagation. The results show that hydrogen addition determines an increase in LBV for all examined binary flammable mixtures. The LBV variation versus the fraction of added hydrogen, rH, follows a linear trend only at moderate hydrogen fractions. The further increase in rH results in a stronger variation in LBV, as shown by both experimental and computed LBVs. Hydrogen addition significantly changes the thermal diffusivity of flammable CH4–air or NG–air mixtures, the rate of heat release, and the concentration of active radical species in the flame front and contribute, thus, to LBV variation.

Prediction of Pressure Rise in a Gas Turbine Exhaust Duct Under Flameout Scenarios While Operating On Hydrogen and Natural Gas Blends

2021 ◽  
Author(s):  
Orlando Ugarte ◽  
Suresh Menon ◽  
Wayne Rattigan ◽  
Paul Winstanley ◽  
Priyank Saxena ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Combustion Model ◽  
Computational Domain ◽  
Cfd Model ◽  
Exhaust Duct ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Abstract In recent years, there is a growing interest in blending hydrogen with natural gas fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity CFD model provide a cost-effective way of assessing the safety risk. In this study, a computational model is implemented to perform three dimensional, compressible and unsteady simulations of reacting flows in a gas turbine exhaust duct. Computational results were validated against data obtained at the simulated conditions in a representative geometry. Due to the enormous size of the geometry, special attention was given to the discretization of the computational domain and the combustion model. Results show that CFD model predicts main features of the pressure rise driven by the combustion process. The peak pressures obtained computationally and experimentally differed in 20%. This difference increased up to 45% by reducing the preheated inflow conditions. The effects of rig geometry and flow conditions on the accuracy of the CFD model are discussed.

Computational Studies of Glow Plug Ignition of Injected High Pressure Gas Jets

2015 ◽  
Author(s):  
Kang Pan ◽  
James S. Wallace
Keyword(s):  
Natural Gas ◽  
Combustion Chamber ◽  
Ignition Delay ◽  
Numerical Study ◽  
Pressure Rise ◽  
Air Gap ◽  
Time Difference ◽  
Glow Plug ◽  
Gas Ignition ◽  
Ignition And Combustion

A numerical study of ignition and combustion in a glow plug (GP) assisted direct-injection natural gas (DING) engine is presented in this paper. The glow plug is shielded and the shield design is an important part of the combustion system development. The results simulated by KIVA-3V indicated that the ignition delay (ID) predicted by an in-cylinder pressure rise was different from that based on a temperature rise, attributed to the additional time required to burn more fuel to obtain a detectable pressure rise in the combustion chamber. This time difference for the ignition delay estimation can be 0.5 ms, which is significant relative to an ignition delay value of less than 2 ms. To further evaluate the time difference between the two different methods of ignition delay determination, sensitivity studies were conducted by changing the glow plug temperature, and rotating the glow plug shield opening angle towards the fuel jets. The results indicated that the ID method time difference varied from 0.3 to 0.8 ms for different combustion chamber configurations. In addition, this study also investigated the influences of different glow plug shield parameters on the natural gas ignition and combustion characteristics, by modifying the air gap between the glow plug and its shield, and by changing the shield opening size. The computational results indicated that a bigger air gap inside the shield can delay gas ignition, and a smaller shield opening can block the flame propagation for some specific fuel injection angles.

Analysis of Pollutant Emissions of Diesel Engine Operating with Mixture of Diesel, Biodiesel and Natural Gas

2015 ◽  
Vol 365 ◽  
pp. 100-105
Author(s):  
Fernando José da Silva ◽  
Antônio Gilson Barbosa de Lima ◽  
Yoge Jerônimo Ramos da Costa ◽  
Celso Rosendo Bezerra Filho
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Experimental Test ◽  
Liquid Fuel ◽  
Air Pressure ◽  
Pollutant Emissions ◽  
Flow Rates ◽  
Exhaust Gases ◽  
Lubricant Oil

The aim of this research is to study the pollutant emissions of the commercial diesel engine, operating with B5 (commercial diesel), B70, B80, B90 and natural gas. The fuel used in the engine consists of a mixture of 15% diesel and biodiesel (liquid fuel) and 85% natural gas. Experiments were made using 40, 60 and 80 kW load. The engine was instrumented to obtain the temperature, air, gas and diesel (plus biodiesel) flow rates, the air pressure at the entrance of the engine, the lubricant oil temperature, and the concentration of exhaust gases during each experimental test. It was verified that the emission of NOx, NO and CO2 had decreased while the emissions of CO and SO2 had increased, when compared to the conditions using standard diesel (B5) alone.

scholarly journals Potential of hydrogen addition to natural gas or ammonia as a solution towards low- or zero-carbon fuel for the supply of a small turbocharged SI engine

2021 ◽  
Vol 312 ◽  
pp. 07022
Author(s):  
Alfredo Lanotte ◽  
Vincenzo De Bellis ◽  
Enrica Malfi
Keyword(s):  
Alternative Fuels ◽  
Laminar Flame ◽  
Combustion Engine ◽  
Numerical Study ◽  
Combustion Process ◽  
Pollutant Emissions ◽  
Si Engine ◽  
Hydrogen Addition ◽  
Emission Regulations ◽  
Zero Carbon

Nowadays there is an increasing interest in carbon-free fuels such as ammonia and hydrogen. Those fuels, on one hand, allow to drastically reduce CO2 emissions, helping to comply with the increasingly stringent emission regulations, and, on the other hand, could lead to possible advantages in performances if blended with conventional fuels. In this regard, this work focuses on the 1D numerical study of an internal combustion engine supplied with different fuels: pure gasoline, and blends of methane-hydrogen and ammonia-hydrogen. The analyses are carried out with reference to a downsized turbocharged two-cylinder engine working in an operating point representative of engine operations along WLTC, namely 1800 rpm and 9.4 bar of BMEP. To evaluate the potential of methane-hydrogen and ammonia-hydrogen blends, a parametric study is performed. The varied parameters are air/fuel proportions (from 1 up to 2) and the hydrogen fraction over the total fuel. Hydrogen volume percentages up to 60% are considered both in the case of methane-hydrogen and ammonia-hydrogen blends. Model predictive capabilities are enhanced through a refined treatment of the laminar flame speed and chemistry of the end gas to improve the description of the combustion process and knock phenomenon, respectively. After the model validation under pure gasoline supply, numerical analyses allowed to estimate the benefits and drawbacks of considered alternative fuels in terms of efficiency, carbon monoxide, and pollutant emissions.

scholarly journals A Numerical Study on the Pilot Injection Conditions of a Marine 2-Stroke Lean-Burn Dual Fuel Engine

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1396
Author(s):  
Hao Guo ◽  
Song Zhou ◽  
Jiaxuan Zou ◽  
Majed Shreka
Keyword(s):  
Natural Gas ◽  
Fuel Injection ◽  
Numerical Study ◽  
Pollutant Emissions ◽  
Dual Fuel ◽  
Injection Timing ◽  
Pilot Injection ◽  
Lean Burn ◽  
Injection Duration ◽  
Pilot Fuel

The global demand for clean fuels is increasing in order to meet the requirements of the International Maritime Organization (IMO) of 0.5% global Sulphur cap and Tier III emission limits. Natural gas has begun to be popularized on liquefied natural gas (LNG) ships because of its low cost and environment friendly. In large-bore marine engines, ignition with pilot fuel in the prechamber is a good way to reduce combustion variability and extend the lean-burn limit. However, the occurrence of knock limits the increase in power. Therefore, this paper investigates the effect of pilot fuel injection conditions on performance and knocking of a marine 2-stroke low-pressure dual-fuel (LP-DF) engine. The engine simulations were performed under different pilot fuel parameters. The results showed that the average in-cylinder temperature, the average in-cylinder pressure, and the NOx emissions gradually decreased with the delay of the pilot injection timing. Furthermore, the combustion situation gradually deteriorated as the pilot injection duration increased. A shorter pilot injection duration was beneficial to reduce NOx pollutant emissions. Moreover, the number of pilot injector orifices affected the ignition of pilot fuel and the flame propagation speed inside the combustion chamber.

Prediction of Pressure Rise in a Gas Turbine Exhaust Duct Under Flameout Scenarios While Operating on Hydrogen and Natural Gas Blends

2021 ◽  
Author(s):  
Orlando Ugarte ◽  
Suresh Menon ◽  
Wayne Rattigan ◽  
Paul Winstanley ◽  
Priyank Saxena ◽  
...  
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Combustion Process ◽  
Pressure Rise ◽  
Combustion Model ◽  
Computational Domain ◽  
Cfd Model ◽  
Exhaust Duct ◽  
Gas Turbine Exhaust ◽  
Turbine Exhaust

Abstract In recent years, there is a growing interest in blending hydrogen with natural gas fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity CFD model provide a cost-effective way of assessing the safety risk. In this study, a computational model is implemented to perform three dimensional, compressible and unsteady simulations of reacting flows in a gas turbine exhaust duct. Computational results were validated against data obtained at the simulated conditions in a representative geometry. Due to the enormous size of the geometry, special attention was given to the discretization of the computational domain and the combustion model. Results show that CFD model predicts main features of the pressure rise driven by the combustion process. The peak pressures obtained computationally and experimentally differed in 20%. This difference increased up to 45% by reducing the preheated inflow conditions. The effects of rig geometry and flow conditions on the accuracy of the CFD model are discussed.

SFGP 2007 - Natural Gas/Hydrogen Mixture Combustion in a Porous Radiant Burner

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Ségolène Gauthier ◽  
Etienne Lebas ◽  
Dominique Baillis
Keyword(s):  
Natural Gas ◽  
Experimental Tests ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Metallic Foam ◽  
Combustion Mode ◽  
Hydrogen Addition ◽  
Porous Burner ◽  
Hydrogen Mixtures ◽  
Radiant Burners

Within the context of reducing the green house gas emissions, substituting hydrogen for natural gas could have a great environmental impact, but hydrogen has different combustion characteristics than natural gas. This paper reports results of experimental tests of premixed combustion of natural gas-hydrogen mixtures in a porous burner made of open cell metallic foam. The technology of porous radiant burners shows environmental and economical advantages compared to traditional diffusion flame burners. The tests showed that substituting natural gas for hydrogen in a porous burner reduces the pollutant emissions of CO and NOx and the quantity of CO2 produced. For specific powers below 500 kW/m2, the emissions were below the "Blue Angel" label values. But working conditions are limited by hydrogen addition and the equivalence ratio has to be lowered to prevent flashback. The radiant combustion mode is more difficult to obtain with mixtures containing hydrogen and it disappears completely for mixtures with more than 80% vol. hydrogen.

Effects of Biogas Combustion on the Operation Characteristics and Pollutant Emissions of a Micro Gas Turbine

2003 ◽  
Author(s):  
Dieter Bohn ◽  
Joachim Lepers
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Biomass Conversion ◽  
Ceramic Materials ◽  
Pollutant Emissions ◽  
Combustion Model ◽  
Generation Process ◽  
Micro Gas Turbine ◽  
Operation Characteristics

The capability of gas turbines to burn low-BTU biogenic fuels besides natural gas becomes an increasingly important feature for small sized plants. This is particularly the case for micro gas turbines targeting decentralized applications. The energy conversion of biomass to electricity can be improved by integration of a micro gas turbine with the biogas generation process. Such an integrated plant concept is presented in this paper after a general overview of low-BTU fuels suitable for utilization in gas turbines has been given. The advantages are a more efficient biomass conversion and an extension of biomass digestion to biomass with reduced biochemical availability such as mildly lignocellulosic biomass. The effects of biogas utilization on the characteristics of operation of a representatively modeled microturbine are investigated in this paper. Particularly, contributions to the efficiency decrease occuring when biogas is burnt instead of natural gas are analyzed. Further, an overview of the effects of low-BTU fuels on gas turbine materials and pollutant emissions is given. The change of emissions of nitrogen oxide and carbon monoxide is analyzed with a combustion model based on a systematically reduced 6-step reaction mechanism. This study was conducted for an advanced combustor design applying ceramic materials and a transpiration cooling technology.

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