UVM Theses and Dissertations
Format:
Print
Author:
Barlett, Brent
Dept./Program:
Mechanical Engineering
Year:
2005
Degree:
MS
Abstract:
Hydrogen peroxide in concentrations of 70-98%, or high-test peroxide (HTP), has been successfully used as a monopropellant for many applications, such as torpedo propulsion, attitude control for missiles, and precision satellite positioning. The current study is on the aerodynamic' design of an 80 W net electrical power microturbine using the products of decomposed HTP as the working fluid. A meanline, or 1-D, analysis is used to determine the basic geometries of the turbine. Parametric studies performed with computational fluid dynamics (CFD) are then used to refine the design. The CFD analyses are essential for this miniature turbine since loss models typically used for turbine designs are based on empirical data taken from conventional turbines where boundary layer effects are much less pronounced.
Current and future applications of a minaturized HTP system include: portable electrical power, micro-propulsion, and shaft power for small devices. A microturbine of this scale could be used in place of batteries for electronic devices. This technology would be useful for today's foot soldiers that carry many electronic devices. It would also be useful for power generation on small satellites or other aerospace systems. This may be the more attractive use for an HTP driven microturbine. This is because the energy density of HTP is less than that of hydrocarbon fuels, which have oxygen readily available for combustion on earth, but need an oxidizer carried on-board for space applications, increasing the payload.
The work contained herein indicates that isentropic efficiencies as high as 88% are possible for a microturbine operating at subsonic conditions. The diameter of the turbine rotor is about 6 mm, and the passage height is approximately 0.45 mm. After considering losses due to bearings and a microgenerator, the gross power required by the turbine is 105 W to produce 80W of electrical power. Tip-clearance is included in the CFD model, and minimum clearances and blade thicknesses are based on current manufacturing capabilities using silicon to fabricate the miniature components. The CFD results indicate that viscous effects are important at the micro scale. Fluid dynamic blockage due to boundary layers at the rotor inlet is on the order of 20% for the microturbine, while this blockage value for conventional turbines is typically on the order of 5%.
The results of this study can be used to help turbine designers estimate the blockage on future microturbine designs at the meanline level. With additional CFD analyses, loss models can start to be examined for losses due to tip-clearance and disk windage on the rear of the turbine rotor. This work provides the foundation for the development of correlations that can be used by designers to make accurate predictions of microturbine performance in the preliminary design phase.
Current and future applications of a minaturized HTP system include: portable electrical power, micro-propulsion, and shaft power for small devices. A microturbine of this scale could be used in place of batteries for electronic devices. This technology would be useful for today's foot soldiers that carry many electronic devices. It would also be useful for power generation on small satellites or other aerospace systems. This may be the more attractive use for an HTP driven microturbine. This is because the energy density of HTP is less than that of hydrocarbon fuels, which have oxygen readily available for combustion on earth, but need an oxidizer carried on-board for space applications, increasing the payload.
The work contained herein indicates that isentropic efficiencies as high as 88% are possible for a microturbine operating at subsonic conditions. The diameter of the turbine rotor is about 6 mm, and the passage height is approximately 0.45 mm. After considering losses due to bearings and a microgenerator, the gross power required by the turbine is 105 W to produce 80W of electrical power. Tip-clearance is included in the CFD model, and minimum clearances and blade thicknesses are based on current manufacturing capabilities using silicon to fabricate the miniature components. The CFD results indicate that viscous effects are important at the micro scale. Fluid dynamic blockage due to boundary layers at the rotor inlet is on the order of 20% for the microturbine, while this blockage value for conventional turbines is typically on the order of 5%.
The results of this study can be used to help turbine designers estimate the blockage on future microturbine designs at the meanline level. With additional CFD analyses, loss models can start to be examined for losses due to tip-clearance and disk windage on the rear of the turbine rotor. This work provides the foundation for the development of correlations that can be used by designers to make accurate predictions of microturbine performance in the preliminary design phase.