Work is reported on the use of quantitative structural property relationships to estimate the pro... more Work is reported on the use of quantitative structural property relationships to estimate the properties of ionic liquids for which no measured property data are available and to classify liquids a...
Experiments to explore the effect of the molecular structure of ionic liquid propellants on the e... more Experiments to explore the effect of the molecular structure of ionic liquid propellants on the emission mode from a colloid thruster are reported. The colloid thruster is an electrospray device th...
42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
Page 1. Simulation of an Electrostatically Driven Microinjector Pump Gopi C. Krishnan, John W. Da... more Page 1. Simulation of an Electrostatically Driven Microinjector Pump Gopi C. Krishnan, John W. Daily and James Nabity Center for Combustion and Environmental Research Department of Mechanical Engineering University of Colorado at Boulder Page 2. Acknowledgements ...
This paper presents results of analytical and numerical simulations of an electrostatically actua... more This paper presents results of analytical and numerical simulations of an electrostatically actuated microfuel injector. The electrostatic-structural coupling, efficiency of valves, and net flow rate of the pump are calculated using analytical relations and compared with numerical simulations. One way to increase flow rate is to increase the stroke volume, which may lead to large deflection of the diaphragm. Thus, the membrane load deflection relationship is no longer linear and when coupled to the inherently nonlinear fluid behavior leads to a complex problem. We used numerical methods to solve for the fluid-structure interaction and the large deflection of the membrane, and studied the effect of actuation frequency on the net flow rate.
Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitaliz... more Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (C. vulgaris, 9–27°C; Chlorophyta-Ant, 4–14°C) and included a constant temperature control (10°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (C. ...
: The objective of this research was to develop a microelectromechanical system (MEMS) atomizer w... more : The objective of this research was to develop a microelectromechanical system (MEMS) atomizer which could produce small (less than 50 micron) droplets in order to improve gas turbine flameholding and reduce emissions.
Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems... more Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems through self-regulation of heat rejection as some of the flow channels within the device become blocked with ice. This Phase Change Material (PCM) based heat exchanger approach also adds endothermic heat storage capacity to a thermal control system as the water freezes when the radiator rejects heat to cold thermal environments. It then reduces the net heat load to the radiator by melting the solid-phase coolant during periods of high cabin temperatures or when the spacecraft is in a hot thermal environment. Unfortunately, these heat exchangers are susceptible to catastrophic damage if the volumetric expansion during water freeze is not accommodated. Solving this design challenge is complicated when using ground-based experiments to predict the freeze-thaw behavior and performance of PCM heat exchangers in microgravity, since the fluid behaves differently in space than on Earth. Buoyanc...
Human exploration of deep space will require Environmental Control and Life Support Systems of in... more Human exploration of deep space will require Environmental Control and Life Support Systems of increasing robustness as mission duration and distance from Earth increase. As crews travel to distant unexplored environments, designers will need heightened confidence in life support availability under increasing levels of uncertainty and risk. Variation in system performance, environmental conditions, resource consumption, waste generation, and even mission characteristics will lead to unexpected responses, increased likelihood of failures, and even design obsolescence. The cost of system failures will also rise, due to launch mass and volume constraints, time and cost of resupply, and reduced ability to abort to Earth. If not accounted for early in design, the increased risk and cost of uncertainty might preclude human deep space exploration. This paper is the second in a series addressing the topic of robust ECLSS design. The first paper defined ECLSS robustness and discussed distinc...
: Particle size measurements were obtained at the grain exit and nozzle entrance in a solid fuel ... more : Particle size measurements were obtained at the grain exit and nozzle entrance in a solid fuel ramjet combustor using a boron based fuel. The particle size distributions at the aft end of the fuel grain were generally quadra-modal, with mode peaks at 2, 4,15, and 25 - 45 microns. At the nozzle entrance the distributions were tri-modal, due to the complete oxidation of the 2 micron particles. Sauter mean diameter and the size of the largest agglomerates increased with increasing equivalence ratio (or grain length), indicating that the longer grains result in more surface agglomeration. Combustion efficiency increased with equivalence ratio. A direct correlation of particle size alone with combustion efficiency was not obvious and may require an accurate measurement of particle concentration. Keywords: Integral rocket ramjet engines; Rocket propellant grains; Solid fuel ramjet engines; Combustion; Laser particle measurement; Metallized rocket fuels. Theses.
Work is reported on the use of quantitative structural property relationships to estimate the pro... more Work is reported on the use of quantitative structural property relationships to estimate the properties of ionic liquids for which no measured property data are available and to classify liquids a...
Experiments to explore the effect of the molecular structure of ionic liquid propellants on the e... more Experiments to explore the effect of the molecular structure of ionic liquid propellants on the emission mode from a colloid thruster are reported. The colloid thruster is an electrospray device th...
42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004
Page 1. Simulation of an Electrostatically Driven Microinjector Pump Gopi C. Krishnan, John W. Da... more Page 1. Simulation of an Electrostatically Driven Microinjector Pump Gopi C. Krishnan, John W. Daily and James Nabity Center for Combustion and Environmental Research Department of Mechanical Engineering University of Colorado at Boulder Page 2. Acknowledgements ...
This paper presents results of analytical and numerical simulations of an electrostatically actua... more This paper presents results of analytical and numerical simulations of an electrostatically actuated microfuel injector. The electrostatic-structural coupling, efficiency of valves, and net flow rate of the pump are calculated using analytical relations and compared with numerical simulations. One way to increase flow rate is to increase the stroke volume, which may lead to large deflection of the diaphragm. Thus, the membrane load deflection relationship is no longer linear and when coupled to the inherently nonlinear fluid behavior leads to a complex problem. We used numerical methods to solve for the fluid-structure interaction and the large deflection of the membrane, and studied the effect of actuation frequency on the net flow rate.
Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitaliz... more Including a multifunctional, bioregenerative algal photobioreactor for simultaneous air revitalization and thermal control may aid in carbon loop closure for long-duration surface habitats. However, using water-based algal media as a cabin heat sink may expose the contained culture to a dynamic, low temperature environment. Including psychrotolerant microalgae, native to these temperature regimes, in the photobioreactor may contribute to system stability. This paper assesses the impact of a cycled temperature environment, reflective of spacecraft thermal loops, to the oxygen provision capability of temperate Chlorella vulgaris and eurythermic Antarctic Chlorophyta. The tested 28-min temperature cycles reflected the internal thermal control loops of the International Space Station (C. vulgaris, 9–27°C; Chlorophyta-Ant, 4–14°C) and included a constant temperature control (10°C). Both sample types of the cycled temperature condition concluded with increased oxygen production rates (C. ...
: The objective of this research was to develop a microelectromechanical system (MEMS) atomizer w... more : The objective of this research was to develop a microelectromechanical system (MEMS) atomizer which could produce small (less than 50 micron) droplets in order to improve gas turbine flameholding and reduce emissions.
Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems... more Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems through self-regulation of heat rejection as some of the flow channels within the device become blocked with ice. This Phase Change Material (PCM) based heat exchanger approach also adds endothermic heat storage capacity to a thermal control system as the water freezes when the radiator rejects heat to cold thermal environments. It then reduces the net heat load to the radiator by melting the solid-phase coolant during periods of high cabin temperatures or when the spacecraft is in a hot thermal environment. Unfortunately, these heat exchangers are susceptible to catastrophic damage if the volumetric expansion during water freeze is not accommodated. Solving this design challenge is complicated when using ground-based experiments to predict the freeze-thaw behavior and performance of PCM heat exchangers in microgravity, since the fluid behaves differently in space than on Earth. Buoyanc...
Human exploration of deep space will require Environmental Control and Life Support Systems of in... more Human exploration of deep space will require Environmental Control and Life Support Systems of increasing robustness as mission duration and distance from Earth increase. As crews travel to distant unexplored environments, designers will need heightened confidence in life support availability under increasing levels of uncertainty and risk. Variation in system performance, environmental conditions, resource consumption, waste generation, and even mission characteristics will lead to unexpected responses, increased likelihood of failures, and even design obsolescence. The cost of system failures will also rise, due to launch mass and volume constraints, time and cost of resupply, and reduced ability to abort to Earth. If not accounted for early in design, the increased risk and cost of uncertainty might preclude human deep space exploration. This paper is the second in a series addressing the topic of robust ECLSS design. The first paper defined ECLSS robustness and discussed distinc...
: Particle size measurements were obtained at the grain exit and nozzle entrance in a solid fuel ... more : Particle size measurements were obtained at the grain exit and nozzle entrance in a solid fuel ramjet combustor using a boron based fuel. The particle size distributions at the aft end of the fuel grain were generally quadra-modal, with mode peaks at 2, 4,15, and 25 - 45 microns. At the nozzle entrance the distributions were tri-modal, due to the complete oxidation of the 2 micron particles. Sauter mean diameter and the size of the largest agglomerates increased with increasing equivalence ratio (or grain length), indicating that the longer grains result in more surface agglomeration. Combustion efficiency increased with equivalence ratio. A direct correlation of particle size alone with combustion efficiency was not obvious and may require an accurate measurement of particle concentration. Keywords: Integral rocket ramjet engines; Rocket propellant grains; Solid fuel ramjet engines; Combustion; Laser particle measurement; Metallized rocket fuels. Theses.
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