THE INFLUENCE OF THE HYDROGEN IN THE ...air values of 400K, 600K, 800K, excess air 5 and primary...
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THE INFLUENCE OF THE HYDROGEN IN THE COMPOSITION OF NATURAL GAS UPON THE ATMOSFERIC COMBUSTION WITH LARGE EXCESS AIR Ștefan GRIGOREAN 1 , Gheorghe DUMITRAŞCU 1 , Michel FEIDT 2 , Bogdan HORBANIUC 1 1 „Gheorghe ASACHI” Technical University of Iaşi, Mechanical Engineering Faculty, Str. Profesor Docent Dr. Ing. Dimitrie Mangeron, Nr.43, Iaşi, Romania 2 University of Lorraine, LEMTA ENSEM - 2 Avenue de la Forèt de Haye, BP 90161, 54505 VANDOEUVRE CEDEX, Nancy, France * Author correspondent: [email protected] Abstract The paper presents simulation of the atmospheric combustion of natural gas enriched with hydrogen. This combustion of the natural gas enriched with hydrogen is intended to be used in closed cycle solar hybrid gas turbine engines. The combustion considered adaptability both to the variable input solar energy and to a variable useful heat output and a constant engine power, from full cogeneration to full power. This engine operation can be assured by an external combustion with an adjustable air pre-heating. The combustion simulation, performed in ANSYS numerical codes, considered the following assumptions: - air pre-heating above 800 K, - excess air value from 3 to 5, to ensure a temperature of flame near the combustion chamber wall below 1800K, - different air primary, secondary and dilution ratios. The simulation returned results regarding: the combustion temperature field, the flame OH concentration field, the exhaust gases composition fields, the flue gases velocity field, the pressure gases pressure field. The simulation showed the influence of the air pre-heating temperature upon the atmospheric combustion spatial parameters. Keywords: simulation, atmospheric combustion, natural gas enriched with hydrogen, air high pre- heating, combustion parameters Introduction Due to the continous decreasing level of fossil fuel, and the restrictions regarding emissions, appeared an interest regarding the closed cycle solar hybrid gas turbines for power generation, since, this type of systems will also provide electrical energy at a lower price. Base load energy can be generated by hybrid solar closed cycle power plants, even with the intermittent solar radiation, using a combustion system as a back-up of solar power plant.[1] At this moment, most of the CSP plants, use fossil fuel to generate energy for start-up operation, and for back-up in the case of low solar radiation. With this concept, the overall consumption of fossil fuel over one year is low, and the contribution of fossil fuel to generate electrical energy is less than 15%. With modern combined-cycles, a power plant using can achieve thermal cycle efficiency more than 55%.[2]
Transcript of THE INFLUENCE OF THE HYDROGEN IN THE ...air values of 400K, 600K, 800K, excess air 5 and primary...
THE INFLUENCE OF THE HYDROGEN IN THE COMPOSITION OF NATURAL GAS UPON THE ATMOSFERIC COMBUSTION WITH LARGE
EXCESS AIR Ștefan GRIGOREAN1, Gheorghe DUMITRAŞCU1, Michel FEIDT2, Bogdan HORBANIUC1
1 „Gheorghe ASACHI” Technical University of Iaşi, Mechanical Engineering Faculty, Str. Profesor Docent Dr. Ing. Dimitrie Mangeron, Nr.43, Iaşi, Romania
2 University of Lorraine, LEMTA ENSEM - 2 Avenue de la Forèt de Haye, BP 90161, 54505 VANDOEUVRE CEDEX, Nancy, France
* Author correspondent: [email protected] Abstract
The paper presents simulation of the atmospheric combustion of natural gas enriched with hydrogen. This combustion of the natural gas enriched with hydrogen is intended to be used in closed cycle solar hybrid gas turbine engines. The combustion considered adaptability both to the variable input solar energy and to a variable useful heat output and a constant engine power, from full cogeneration to full power. This engine operation can be assured by an external combustion with an adjustable air pre-heating. The combustion simulation, performed in ANSYS numerical codes, considered the following assumptions:
- air pre-heating above 800 K, - excess air value from 3 to 5, to ensure a temperature of flame near the combustion chamber
wall below 1800K, - different air primary, secondary and dilution ratios.
The simulation returned results regarding: the combustion temperature field, the flame OH concentration field, the exhaust gases composition fields, the flue gases velocity field, the pressure gases pressure field. The simulation showed the influence of the air pre-heating temperature upon the atmospheric combustion spatial parameters. Keywords: simulation, atmospheric combustion, natural gas enriched with hydrogen, air high pre-heating, combustion parameters Introduction
Due to the continous decreasing level of fossil fuel, and the restrictions regarding emissions, appeared an interest regarding the closed cycle solar hybrid gas turbines for power generation, since, this type of systems will also provide electrical energy at a lower price. Base load energy can be generated by hybrid solar closed cycle power plants, even with the intermittent solar radiation, using a combustion system as a back-up of solar power plant.[1] At this moment, most of the CSP plants, use fossil fuel to generate energy for start-up operation, and for back-up in the case of low solar radiation. With this concept, the overall consumption of fossil fuel over one year is low, and the contribution of fossil fuel to generate electrical energy is less than 15%. With modern combined-cycles, a power plant using can achieve thermal cycle efficiency more than 55%.[2]
Referring to some studies, up to year 2020, worldwide natural gas consumption will increase
by 12%. This is one of main reasons regarding emission reduction, from stationary combustion plants, using natural gas. [3] Also, due to this fact, there is interest to switch to alternative fuel where is possible. An alternative to natural gas is represented by producer gas, which is based on biomass obtained from gasification process. This is a mixture of CH 4 , H 2 ,CO 2 , CO, N 2 . Some articles show that producer gas have different combustion characteristics compared to natural gas. [4,5]
Natural gas is available in many spots worldwide. The composition of natural gas varies from gas field to gas field, and is relative to source, nature and level of treatment. Main component on natural gas is CH 4 , but also exist other constituents which affect properties, like: ethane, propane, butane, water, carbon dioxide, nitrogen. [6] These variables can produce significant changes to the flame temperature and combustion characteristics, like thermodynamic properties of burned gases.
Related to other studies, when the combustion temperature exceeds 1800K, the NO can decrease by half, which is inversely proportional to CO emissions [7]. So, based on the flame temperature, can identify thermal efficiency, and also CO and NO x . 1 – Design of combustion chamber The combustion chamber which is modeled and will be used in Ansys simulation, was designed as part of an demonstrator, capable to recreate all the conditions for analysis of combustion process for gaseous and liquid fuels. The demonstrator has some variables to recreate with high accuracy the simulation conditions used in software modeling. That includes the variable air fuel ratio, variable temperature of preheated air, variable ratio between primary air and secondary air. The system includes a mass spectrometer, and an PLIF. In this case, the combustion chamber is cylindrical, disposed horizontal. It has 12 radial holes, to permit the secondary air to enter in the combustion process, and the cool the combustion chamber wall.
Fig.1. Combustor assembly
In Ansys is recreated the fluid area inside the combustion chamber, and then is defined the areas for fuel inlet, primary air inlet, secondary air inlet, and exhaust. The fuel inlet, primary air and secondary air are defined as mass flow inlet, using a constant flow, that allows the total pressure to vary in consistent to the reactions inside the combustion chamber. For the air inlet faces, there is utilized mass fraction 0, and the flow direction is set to normal to boundary. Turbulence intensity is set to 5%. Outlet area is defined using pressure outlet condition. For this, must be specified a value for the static pressure in the exhaust area. The value is relative to the operational pressure, and is set to 0. The mesh contains 1600000 elements with 294000 nodes, in consistent to other simulations analyzed.
Fig.2. Mesh
2 – Results
Using the Ansys model described in previous chapter, a number of simulations were carried on. From all the simulations, in this article will be mentioned and explained the most significant of them. For a simple understanding of these results, it is represented a schematic which will identify the measuring points for all parameters, referring to the point of fuel injection in combustion chamber. The injection point have the coordinates x=0, y=0, z=0. Results will be show in a plane located in the middle of combustion chamber, so all the points will have 2 coordinates.
In table and in pictures below, will be shown results regarding simulations with preheated air values of 400K, 600K, 800K, excess air 5 and primary air/secondary air ratio 0.2 . Represented points are in the upper side of combustion chamber, gravity influence is neglected.
Fig.3. Measuring points
The points are defined using coordinates, in order to cover entire surface of the mid plane,
where the values for mass species, temperature field, and velocity field are registered. From these values it is more accurate to identify the differences between combustion processes, for 3 values of preheated air.
Table 1: Velocity field, Temperature field, Mass fractions for T=400K
Preheattemperature400K,Excessairratio5,primaryair/secondaryair0.2
Measuringpoint
Xcoord
Ycoord
Tempfield
Speedfield
CO2Massfraction
COMassfraction
NOMassfraction
OMassfraction
OHMassfraction
1 0 10 725.465 5.08112 0.055424 0.0244881 1.88E-06 3.90E-058.54E-052 0 40 1016.82 1.18247 0.0889961 0.0272994 2.47E-06 1.66E-068.40E-063 0 70 1308.7 0.22265 0.10758 0.0265297 2.64E-06 3.49E-050.0002001564 0 100 1364.47 0.0644730.0861361 0.00996712 2.19E-06 5.96E-050.0004881175 0 130 1186.67 0.2216370.0599231 0.00309684 1.50E-06 3.61E-050.0003575286 0 160 968.834 0.3679280.0393457 0.0006306061.10E-06 1.72E-050.0001733797 0 190 800.178 0.4683910.025966 5.64E-05 8.65E-07 4.08E-064.46E-058 30 10 1114.94 0.3700120.0970775 0.0281713 2.87E-06 2.30E-051.04E-049 30 40 1197.48 0.2729250.101452 0.0277848 2.74E-06 9.97E-065.33E-0510 30 70 1421 0.1345990.103393 0.202016 2.68E-06 8.80E-530.00051941411 30 100 1327.35 0.1424870.0763897 0.00688788 1.99E-06 5.46E-050.00047164612 30 130 1100.89 0.2728460.0503894 0.00177064 1.38E-06 2.85E-050.00028345913 30 160 890.84 0.3680810.0327712 0.0002704981.04E-06 1.05E-050.00010775914 30 190 746.577 0.4427160.0214842 1.83E-05 8.15E-07 1.89E-062.18467E-0515 60 10 1388.41 0.0830480.110667 0.0221353 3.57E-06 6.17E-053.57E-0616 60 40 1439.24 0.3100290.103538 0.0178894 3.00E-06 8.59E-053.00E-0617 60 70 1294.64 0.4550030.0718083 0.0061921 2.07E-06 6.43E-052.07E-0618 60 100 1016.18 0.5883580.0457546 0.0010917 1.46E-06 2.34E-051.46E-0619 60 130 843.351 0.50509 0.0295925 8.14E-05 1.10E-06 5.62E-061.10E-0620 60 160 723.575 0.4523050.0192397 4.46E-06 8.44E-07 7.01E-078.44E-0721 60 190 629.03 0.4522030.0122448 7.94E-07 6.42E-07 9.02E-086.42E-0722 90 10 1276.57 0.3125380.0789425 7.19E-03 3.40E-06 4.84E-054.50E-0423 90 40 1328.11 0.1150680.085534 7.09E-03 2.80E-06 6.90E-056.02E-0424 90 70 987.844 1.18128 0.0465075 3.94E-04 1.63E-06 1.80E-051.85E-0425 90 100 829.059 1.02706 0.0295823 5.17E-06 1.21E-06 1.24E-061.74E-0526 90 130 712.891 0.8680390.0187587 1.13E-06 8.85E-07 1.48E-072.18E-0627 90 160 632.534 0.6136180.0122964 6.73E-07 6.74E-07 4.01E-033.71E-0728 90 190 556.93 0.7134270.007210244.12E-07 4.82E-07 1.94E-082.15E-0129 120 10 976.094 0.2408510.0485659 0.00150872 2.24E-06 2.68E-050.00026619730 120 40 1106.13 0.6090130.0628184 0.00141487 2.44E-06 3.88E-050.00038524631 120 70 811.426 3.03184 0.0294721 3.51E-05 1.22E-06 3.70E-064.24E-0532 120 100 756.638 0.8344140.023195 1.66E-06 1.03E-06 3.20E-074.98E-0633 120 130 632.152 2.23913 0.0126733 7.23E-07 6.39E-07 6.23E-087.62E-0734 120 160 595 0.44497 0.009596175.33E-07 5.62E-07 2.61E-081.49E-0735 120 190 520.796 1.5761 0.004999972.99E-07 3.64E-07 1.26E-083.97E-08
Table 2: Velocity field, Temperature field, Mass fractions for T=600K
Preheattemperature600K,Excessairratio5,primaryair/secondaryair0.2
Measuringpoint
Xcoord
Ycoord
Tempfield
Speedfield
CO2Massfraction
COMassfraction
NOMassfraction
OMassfraction
OHMassfraction
1 0 10 773.179 5.39912 0.0543259 0.0232487 9.64E-07 3.52E-05 7.96E-052 0 40 1197.21 0.6765 0.0931013 2.83E-02 1.35E-06 5.82E-05 2.11E-043 0 70 1414.56 0.566 0.0799145 0.0095934 1.19E-06 9.21E-05 0.0006154 0 100 1281.91 0.15997 0.066876 0.001715 1.01E-06 4.42E-05 0.0004365 0 130 1196.5 0.4176 0.0554652 8.85E-05 9.08E-07 1.35E-05 1.55E-046 0 160 1124.72 0.7755 0.0462696 1.02E-05 8.14E-07 3.47E-06 5.06E-057 0 190 1069.53 0.9858 0.038727 3.70E-06 7.28E-07 1.18E-06 1.97E-058 30 10 1289.48 0.426769 0.0990186 2.64E-02 1.63E-06 7.93E-05 3.34E-049 30 40 1417.35 0.802 0.0913505 1.90E-02 1.40E-06 1.29E-04 5.97E-0410 30 70 1342.59 0.70377 0.06832 5.10E-03 1.01E-06 5.82E-05 4.75E-0411 30 100 1212.17 0.47846 0.0556188 3.41E-04 8.46E-07 2.24E-05 0.00023296712 30 130 1125.25 0.5384 0.0451381 1.30E-05 7.57E-07 3.84E-06 5.37E-0513 30 160 1066.39 0.72068 0.0376842 3.68E-06 6.83E-07 1.18E-06 1.94E-0514 30 190 1019.04 0.86566440.0314138 2.11E-06 6.12E-07 4.75E-07 8.21E-0615 60 10 1480.56 0.415165 0.160307 1.89E-02 1.74E-06 8.61E-05 5.67E-0416 60 40 1445.39 0.497247 0.08825 1.02E-02 1.31E-06 9.26E-05 6.67E-0417 60 70 1286.17 1.23742 0.0655168 7.23E-04 9.27E-07 3.68E-05 3.71E-0418 60 100 1136.17 1.47426 0.0462416 9.36E-06 7.34E-07 3.23E-06 4.79E-0519 60 130 1048.32 1.00378 0.0345246 2.50E-06 6.03E-07 6.45E-07 1.13E-0520 60 160 988.682 0.775655 0.026774 1.54E-06 5.14E-07 2.23E-07 3.77E-0621 60 190 939.646 0.780567 0.0206282 1.11E-06 4.39E-07 9.75E-08 1.38E-0622 90 10 1421.62 0.58303 0.0855805 7.84E-03 1.41E-06 5.83E-05 5.30E-0423 90 40 1485.49 0.406916 0.0954697 6.72E-03 1.44E-06 8.73E-05 7.94E-0424 90 70 1228.24 2.71329 0.597594 1.65E-04 8.91E-07 1.96E-05 2.15E-0425 90 100 1090.67 2.3206 0.0408459 5.19E-06 6.62E-07 1.80E-06 2.84E-0526 90 130 990.841 1.74245 0.0271216 1.59E-06 4.91E-07 2.35E-07 4.31E-0627 90 160 935.303 1.05415 0.0199215 1.06E-06 4.04E-07 8.16E-08 1.05E-0628 90 190 884.671 1.43052 0.0139369 7.49E-07 3.25E-07 4.15E-08 3.31E-0729 120 10 1283.86 0.419905 0.0712204 2.84E-03 1.11E-06 4.96E-05 4.89E-0430 120 40 1394.73 1.18758 0.0872338 2.87E-03 1.32E-06 7.73E-05 7.50E-0431 120 70 1109.44 6.17086 0.0448461 2.11E-04 6.95E-07 1.49E-05 1.51E-0432 120 100 1044.22 1.43142 0.0354729 5.36E-06 5.88E-07 1.55E-06 2.29E-0533 120 130 926.614 4.25239 0.0197631 1.35E-06 3.69E-07 2.27E-07 3.42E-0634 120 160 906.845 0.578576 0.0166769 8.85E-07 3.50E-07 5.51E-08 5.53E-0735 120 190 851.119 2.99093 0.0105969 5.83E-07 2.58E-07 2.95E-08 1.86E-07
Table 3: Velocity field, Temperature field, Mass fractions for T=800K
Preheattemperature800K,Excessairratio5,primaryair/secondaryair0.2
Measuringpoint
Xcoord
Ycoord
Tempfield
Speedfield
CO2Massfraction
COMassfraction
NOMassfraction
OMassfraction
OHMassfraction
1 0 10 843.6426.29498 0.05800560.0271932 3.30E-06 5.85E-05 0.0001204612 0 40 1212.2 1.17022 0.09511830.0292758 4.14E-06 8.47E-06 3.99E-053 0 70 1542.940.1170750.09931140.0180398 3.83E-06 0.000109117 0.0006279394 0 100 1465.190.1273560.07394520.00517344 2.67E-06 4.98E-05 0.0004703765 0 130 1357.840.2062480.05588820.0009029622.06E-06 3.00E-05 0.0003007036 0 160 1253.720.4983730.04161734.96E-05 1.70E-06 6.64E-06 7.75E-057 0 190 1183.4 0.7552920.03246143.88E-01 1.46E-06 1.07E-06 1.62E-058 30 10 1276.730.4142580.992038 0.0288169 4.73E-06 4.10E-05 0.0001751469 30 40 1418.6 0.4390190.105785 0.027672 4.56E-06 4.81E-05 0.00024299910 30 70 1558.070.3384850.09168020.0132662 3.72E-06 9.90E-05 0.00064397611 30 100 1449.190.2187930.06926560.00360524 2.60E-06 4.69E-05 0.00045430812 30 130 1324.780.3180570.05088230.0004016932.02E-06 2.07E-05 0.00021320113 30 160 1225.4 0.5273660.03772871.72E-05 1.67E-06 3.35E-06 4.30E-0514 30 190 1159.770.73886 0.02926312.84E-06 1.41E-06 5.39E-07 8.78E-0615 60 10 1543.610.1943410.111457 0.220726 5.45E-06 7.20E-05 0.00047110616 60 40 1602.160.4672340.103508 0.0165381 4.88E-06 1.05E-04 0.00069236217 60 70 1509.160.6870050.07760020.00488693 3.26E-06 7.60E-05 0.00062069118 60 100 1350.090.9137710.05478370.00034838 2.38E-06 2.19E-05 0.00022785119 60 130 1233.140.8272410.03906771.08E-05 1.87E-06 2.77E-06 3.79E-0520 60 160 1158.580.7810330.02901151.89E-06 1.50E-06 3.85E-07 6.56E-0621 60 190 1104.190.8455650.217192 1.17E-06 1.21E-06 1.11E-07 1.64E-0622 90 10 1531.360.4884280.08808878.54E-03 4.44E-06 6.43E-05 5.62E-0423 90 40 1584.180.2145310.09569517.58E-03 4.53E-06 9.83E-05 8.25E-0424 90 70 1365.341.95005 0.06090083.04E-04 2.80E-06 2.55E-05 2.67E-0425 90 100 1246.371.76891 0.04297576.76E-06 2.13E-06 2.41E-06 3.68E-0526 90 130 1162.021.59596 0.03030141.90E-06 1.61E-06 3.76E-07 6.54E-0627 90 160 1107.351.16103 0.02248371.20E-06 1.27E-06 1.05E-07 1.51E-0628 90 190 1058.141.435 0.01582778.41E-07 9.65E-07 4.92E-08 4.38E-0729 120 10 1380.980.4203420.06950952.46E-03 3.46E-06 4.79E-05 4.72E-0430 120 40 1455.481.05809 0.08083141.79E-03 3.84E-06 6.50E-05 6.35E-0431 120 70 1239.865.33072 0.04366148.43E-05 2.16E-06 9.27E-06 1.03E-0432 120 100 1190.631.50329 0.03599174.33E-06 1.85E-06 1.30E-06 2.02E-0533 120 130 1099.254.2933 0.02205241.41E-06 1.21E-06 2.32E-07 3.65E-0634 120 160 1076.130.8555990.01869129.96E-07 1.09E-06 7.45E-08 9.23E-0735 120 190 1024.473.25627 0.119055 6.50E-07 7.52E-07 3.55E-08 2.70E-07
The below set of images are representing the results for one simulation, with air preheat
temperature of 300K, primary air/secondary air ratio 0.2, and excess air in value of 5.
3 – Conclusions After conducted simulations, it is noticeable that mass fractions for CO, CO 2 , OH, O are increasingly proportional to the excess air ratio, while the lowest value for NO mass fraction is achieved at air fuel ratio 4. Also, for same air fuel ratio, the mass fractions are more concentrated in the flame area, while for other values for air fuel ratio the mass fractions are disposed more to the direction of exhaust gases flow. In addition to this work, all simulations will be reevaluated and validated using combustion demonstrator.
In this article are presented only some results with higher impact, in the background of this work, there are completed simulations for a variety of air preheat temperatures, from 300K up to 1100K. In conclusion, after all these simulations, there are some issues to be mentioned like: - for air excess ratio 4 and 5, the high temperature area and the flame path, are more concentrated to the area of fuel injection; - related to the primary air/secondary air ratio, it is noticeable a lower temperature near the combustion chamber wall, for the value 0.4; - for same value of primary air/secondary air ratio, mass fraction CO is more concentrated in the burning area, for all temperature domains, and mass fraction NO have lowest values; - as preheat temperature is increased, the values for O and OH mass fraction are higher. As in other researches, the mass fraction NO have lower values for a preheating temperature lower than 600K, after this value, the mass fraction NO have higher values.
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[2] C.S. Turchi, Zhiwen Ma, Co-located gas turbine/solar thermal hybrid designs for power production, Renewable Energy 64 (2014) 172-179 [3] R. Navakas, A. Saliamonas, N. Striugas, A. Dziugys, R. Paulauskas, K. Zakarauskas, Effecof producer gas addition and air excess ratio on natural gas flame luminescence, Fuel 21(2018) 478-489 [4] G. Richards, M. McMillian, R. Gemmen, W. Rogers, S.Cully, Issues for low-emission, fuel- flexible power systems. Prog Energy Combust Sci 2001;27(2):141-69 [5] S. Candel, Combustion dynamics and control: progress and challenges. Proc Combust Inst 2002;29(1):1-28 [6] G. A. Karim, 2015. Dual-fuel Diesel Engines. CRC Press Taylor&Francis, Boca Raton London New York [7] S. McAllister, Chen J., Y. Pello, A.C.F., 2011. Fundamentals of Combustion Process. Springer. New York. USA
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