RP Poster March 11
1
The Effect of Dual Injection on Combustor Emissions Introduction Combustion is a series of chemical reactions that involves the burning of fuel inside an engine to provide power to a system. In the process, combustion also emits harmful gases into the environment such as CO and NO. Engineers and researchers are always looking for ways to make the combustion process more efficient and less harmful to the environment. In a combustor, fuel and air are mixed to allow for the combustion reaction to take place. However, the mixing of fuel and air that takes place in a combustor is inadequate and it results in hotspots (local spot of high temperature). This increases the amount of pollutants formed, especially NO x, which is a strong function of the temperature. The standard combustor geometry is a cylinder with one air inlet and one fuel inlet. Altering the combustor design to allow for two sets of air and fuel inlets has the potential to enhance mixing, reduce the frequency of these hotspots, and ultimately reduce harmful emissions. The dual injection combustor has air inlets on the top and bottom and fuel inlets on each side. Methodology The combustor was secured into the test rig and all air and fuel lines were sealed in order to prevent leakage of any air or fuel. The combustor was ignited with a propane torch and air and fuel rates were increased to desired values. The air-fuel flow rate was set to 0.8 using the flow controllers. The combustor was allowed to run at this ratio for about three to four minutes to allow for the reading on the gas analyzer to stabilize. Emissions of NO, CO, CO 2 , and O 2 were measured using the gas analyzer. Steps 4 and 5 were repeated for pressure ratios of 0.7, 0.6, 0.5, and 0.4. Prior to experimentation, preliminary data was collected to determine the performance of a standard, single-injection combustor. Combustor emissions were measured and compared against this preliminary data. Emissions were measured at different air temperatures and fuel-air pressure ratios. Conclusion In this study the effect of dual injection on combustor emissions was tested. The purpose of this experimentation was to potentially enhance the combustion process, making it more efficient and environmentally- friendly. Any positive findings could be applied to gas turbines specifically in aircrafts. Enhanced combustion could result in better fuel efficiency for such vehicles and even in automobiles as well. According to the data, the dual injection system was unsuccessful in enhancing the mixing of air and fuel inside a combustor. The carbon oxide emissions of dual injection were generally the same as demonstrated with single injection, but the emissions of nitrogen oxides increased significantly. The results of tests with dual injection can be taken into account when testing other methods of improving combustion. It is important to note the negative interaction between the two air-fuel injection points. The addition of even more inlets in the combustor design can now be eliminated since this method proved to negatively impact the system. To avoid such unequal distribution, fuel flow rate distribution can be modified. Instead of air and fuel being split evenly between both injection points, the amount of fuel for each injector can be manipulated to control the strength of each reaction zone. Such fuel variation has the potential to change the local equivalence ratio of the jet affecting different flame characteristics such as flame speed. Varying the fuel amount can impact the resulting emissions and the strength of the reaction zone. Consequently, fuel variation can be used as means to control flame characteristics and emissions to produce enhanced performance and lower emissions than those demonstrated through single injection. This is of extreme importance for combustion research as multiple injectors will be required to maintain adequate residence time and injection velocities within the combustor. Findings Dual injection produced significantly higher emissions of nitrogen oxides than single injection at all equivalence ratios except for 0.5. The dual injection system recorded its lowest emissions at an air-fuel equivalence ratio of 0.6: about 5ppm NO and 30ppm CO. Nitrogen oxide emissions decreased proportionally to the equivalence ratio while carbon oxides decreased to a minimum at an equivalence ratio of 0.6 and then began to increase again. Experiments with dual injection demonstrated higher emissions than those demonstrated with single injection. For the same equivalence ratio, NO emissions increased by about 20%, with minimal change in CO emissions. Dual injection combustor in the process of burning methane. Miles Robinson Acknowledgments I would like to thank Dr. Ashwani K. Gupta for allowing me to work in the lab and Ahmed E. E. Khalil for working alongside me on my research.
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Transcript of RP Poster March 11
The Effect of Dual Injection on Combustor Emissions
Introduction Combustion is a series of chemical reactions that involves the burning of fuel inside an engine to provide power to a system. In the process, combustion also emits harmful gases into the environment such as CO
and NO. Engineers and researchers are always looking for ways to make the combustion process more efficient and less harmful to the environment. In a combustor, fuel and air are mixed to allow for the combustion reaction to take place. However, the mixing of fuel and air that takes place in a combustor is inadequate and it results in hotspots (local spot of high temperature). This increases the amount of pollutants formed, especially NOx, which is a strong function of the temperature. The standard combustor geometry is a cylinder with one air inlet and one fuel inlet. Altering the combustor design to allow for two sets of air and fuel inlets has the potential to enhance mixing, reduce the frequency of these hotspots, and ultimately reduce harmful emissions.
The dual injection combustor has air inlets on the top and bottom and fuel inlets on each side.
Methodology
The combustor was secured into the test rig and all air and fuel lines were sealed in order to prevent leakage of any air or fuel.
The combustor was ignited with a propane torch and air and fuel rates were increased to desired values.
The air-fuel flow rate was set to 0.8 using the flow controllers. The combustor was allowed to run at this ratio for about three to four minutes to allow for the reading on the gas analyzer to stabilize.
Emissions of NO, CO, CO2, and O2 were measured using the gas analyzer. Steps 4 and 5 were repeated for pressure ratios of 0.7, 0.6, 0.5, and 0.4.
Prior to experimentation, preliminary data was collected to determine the performance of a standard, single-injection combustor. Combustor emissions were measured and compared against this preliminary data. Emissions were measured at different air temperatures and fuel-air pressure ratios.
Conclusion In this study the effect of dual injection on combustor emissions was tested. The purpose of this experimentation was to potentially enhance the combustion process, making it more efficient and environmentally-friendly. Any positive findings could be applied to gas turbines specifically in aircrafts. Enhanced combustion could result in better fuel efficiency for such vehicles and even in automobiles as well. According to the data, the dual injection system was unsuccessful in enhancing the mixing of air and fuel inside a combustor. The carbon oxide emissions of dual injection were generally the same as demonstrated with single injection, but the emissions of nitrogen oxides increased significantly. The results of tests with dual injection can be taken into account when testing other methods of improving combustion. It is important to note the negative interaction between the two air-fuel injection points. The addition of even more inlets in the combustor design can now be eliminated since this method proved to negatively impact the system. To avoid such unequal distribution, fuel flow rate distribution can be modified. Instead of air and fuel being split evenly between both injection points, the amount of fuel for each injector can be manipulated to control the strength of each reaction zone. Such fuel variation has the potential to change the local equivalence ratio of the jet affecting different flame characteristics such as flame speed. Varying the fuel amount can impact the resulting emissions and the strength of the reaction zone. Consequently, fuel variation can be used as means to control flame characteristics and emissions to produce enhanced performance and lower emissions than those demonstrated through single injection. This is of extreme importance for combustion research as multiple injectors will be required to maintain adequate residence time and injection velocities within the combustor.
Findings Dual injection produced significantly higher emissions of nitrogen oxides than single injection at all equivalence ratios except for 0.5. The dual injection system recorded its lowest emissions at an air-fuel equivalence ratio of 0.6: about 5ppm NO and 30ppm CO. Nitrogen oxide emissions decreased proportionally to the equivalence ratio while carbon oxides decreased to a minimum at an equivalence ratio of 0.6 and then began to increase again. Experiments with dual injection demonstrated higher emissions than those demonstrated with single injection. For the same equivalence ratio, NO emissions increased by about 20%, with minimal change in CO emissions.
Dual injection combustor in the process of burning methane.
Miles Robinson
Acknowledgments I would like to thank Dr. Ashwani K. Gupta for allowing me to work in the lab and Ahmed E. E. Khalil for working alongside me on my research.
