Modeling of a High Energy Density Propulsion System Based on the Combustion of Aluminum and Steam

This thesis presents a thermodynamic analysis of a novel Rankine cycle aluminum/steam combustion power system being developed for use in Unmanned Underwater Vehicles (UUVs). The analysis is performed using a system modeling tool developed by the NASA Glenn Research Center called Numerical Propulsion System Solver (NPSS). Thermodynamic models of the individual components are created and linked together in NPSS, which then solves the system by enforcing mass and energy conservation. Design and off-design conditions are simulated and predicted performance is compared with predictions made by two other research groups. The simulations predict that this power system could provide at least five-fold increases in range and endurance for the US Navy's 'Sea Horse' UUV. A rudimentary sensitivity analysis is used to identify the factors which most strongly influence the performance of the design. Lastly, recommendations for future work and possible model improvements are discussed

The Erosion Prediction Impact on Current Hall Thruster Model Development

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76124/1/AIAA-2008-5087-712.pd

Flow Separation Associated with 3-D Shock-Boundary Layer Interaction (SBLI)

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140423/1/6.2014-1138.pd

Relationship Between Intermittent Separation and Vortex Structure in a Three-Dimensional Shock/Boundary-Layer Interaction

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140686/1/1.J053905.pd

An Experimental Study of Three-Dimensional Inlet Shock-Boundary Layer Interactions.

New experimental results are presented of a three dimensional inlet shock-boundary layer interaction (3DI-SBLI) generated by a six-degree full-span wedge installed in the 57 $times$ 70 -mm Michigan 'Glass Inlet' wind tunnel at Mach 2.75. Images from two traditional techniques, oil flow and Schlieren are compared. Oil flow lines, coincident with the local skin friction, show a complex three dimensional picture despite the two-dimensionality of the density gradient visualization. Analytical complexity regarding three dimensional flow has prevented many previous investigations from investigating these regions. However, significant discrepancy occurs when using insight gained in two-dimensional interactions on three dimensional problems. Rather than rely on amalgamated two-dimensional explanations for the oil flow, Legendre's critical point theory is recalled to describe local skin friction topologies in the 3DI-SBLI. Extending this framework from a local interaction structure towards the far field, the `secondary flow separation concept' is proposed to couple the global flow topology to the skin friction lines. Using the concept, the influence of adding the third dimension becomes clear. Arranging points of `primary separation' in the flow, and the vortex structures produced by them, we can predict the locations of secondary separation and the global flow character downstream. To investigate the link between skin friction and the flow field, the 3DI-SBLI is quantified using stereo particle image velocimetry (SPIV). Data have been obtained in three streamwise horizontal, three streamwise vertical, and ten spanwise image planes. These measurements are used to evaluate the secondary flow separation concept. Verification of the concept is crystalized by the measurement of streamwise vortical structures. For this case, one large vortex structure is carried along each sidewall under the swept-shock foot, while the two from in each corner region. The hypothesis predicts the interaction of two opposing vortical structures produce a secondary separation, and one appears on each sidewall and another along the tunnel centerline. The proposed theory is therefore useful as a simple physical model to describe complex 3DI-SBLIs as the sum of vortex interactions.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/93834/1/eeagle_2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/93834/2/eeagle_3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/93834/3/eeagle_1.pd

An improved entrainment rate measurement method for transient jets from 10 KHZ particle image velocimetry.

International audienceOne strategy to reduce soot formation in compression–ignition engines is extending the ignition delay to provide more time for mixing. However, vapor–fuel concentration measurements have shown that near-injector mixtures become too lean to achieve complete combustion, leading to a relative increase in unburned hydrocarbon emissions. One potential contributor to over-leaning is an "entrainment wave," which is a transient increase in local entrainment after the end of injection. Although an entrainment wave can be predicted by a one-dimensional (1D) free-jet model, no previous measurements at diesel injection conditions have demonstrated conclusively its existence, nor has its magnitude been verified. Using particle image velocimetry (PIV) in the ambient gases, we measure entrained gas velocity through a diesel jet boundary before, during, and after the injection. The entrainment calculation depends on the definition of the jet boundary, here newly proposed based on the minimum of the radial coordinate and the radial velocity (rνr). Unlike previous formulations, the method is robust even in the presence of axial flow gradients in the ambient gases. Prior to the end of injection, the measured entrainment rates that agree well with non-reacting steady gas-jet behavior, as well as with the 1D free-jet model. After end of injection, the local entrainment rate temporarily increases by a factor of 2, which is similar to the factor 2.5 increase predicted by the 1D model. However, the entrainment wave is more broadly distributed in the experimental data, likely due to confinement and/or other real-jet processes absent in the 1D model

Parametric Comparison of Well-Mixed and Flamelet n-dodecane Spray Combustion with Engine Experiments at Well Controlled Boundary Conditions

Extensive prior art within the Engine Combustion Network (ECN) using a Bosch single axial-hole injector called 'Spray A' in constant-volume vessels has provided a solid foundation from which to evaluate modeling tools relevant to spray combustion. In this paper, a new experiment using a Bosch three-hole nozzle called 'Spray B' mounted in a 2.34 L heavy-duty optical engine is compared to sector-mesh engine simulations. Two different approaches are employed to model combustion: the 'well-mixed model' considers every cell as a homogeneous reactor and employs multi-zone chemistry to reduce the computational time. The 'flamelet' approach represents combustion by an ensemble of laminar diffusion flames evolving in the mixture fraction space and can resolve the influence of mixing, or 'turbulence-chemistry interactions,' through the influence of the scalar dissipation rate on combustion. Both combustion methodologies are implemented in the Lib-ICE code which is an unsteady Reynolds-averaged Navier-Stokes solver with k-ϵ turbulence closure based on OpenFOAM® technology. Liquid length and vapor penetration predictions generally fall within the experimental measurement uncertainty at 7.5% O2, 900 K, and 15.2 kg/m3. Flame liftoff length, cylinder pressure, apparent heat release rate, and ignition delay time from the two computations are compared to experiments under single parametric variation of ambient density 15.2 kg/m3 and 22.8 kg/m3, temperatures of 800, 900, and 1000 K, at 13, 15 and 21% Oxygen and injection pressure of 500, 1000, and 1500 bar. Both models generally provide apparent heat release rate maxima to within the uncertainty. The flamelet model better predicts the sensitivity of lift-off length while the well-mixed model better predicts ignition delay