Engineering Commons^™

Branch Detonation Of A Pulse Detonation Engine With Flash Vaporized Jp-8, John David Slack

Theses and Dissertations

Pulse Detonation Engines (PDE) operating on liquid hydrocarbon fuels are limited to operating frequencies of 35 Hz due to long ignition times from a low energy ignition sources. This study shows ignition time of JP-8 can be nearly eliminated by igniting a thrust tube using a secondary detonation. A counter flow heat exchanger attached to a thrust tube utilized waste heat from the detonation process to heat JP-8 to supercritical conditions. The fuel flash vaporized when injected into the air stream of the engine. A detonation was produced by a spark in a 5 cm diameter, 1.37 m long tube. …

High Temperature Heat Exchanger Project: Quarterly Progress Report July 1, 2006 Through September 30, 2006, Anthony Hechanova

Publications (NSTD)

Hydrodynamics and thermal numerical modeling coupled with sulfur trioxide decomposition for the one channel geometry with three different channel configurations were performed. The results obtained from the numerical modeling were compared with the baseline design under the same boundary and operation conditions. The case with diamond shaped channels has the highest percentage of sulfuric acid decomposition. The baseline channel geometry has the lowest pressure drop compared with other cases.

Design And Numerical Simulation Of Two Dimensional Ultra Compact Combustor Model Sections For Experimental Observation Of Cavity-Vane Flow Interactions, David S. Moenter

Theses and Dissertations

An improved computational fluid dynamics (CFD) model was developed for numerical simulation of the Ultra Compact Combustor (UCC) concept to enhance turbulent flow characterization of the circumferentially traveling, centrifugal-force enhanced combustion, cavity flow into the engine main flow passage via a radial cavity in the turbine axial guide vanes. The CFD model uses a dense grid on a 60° periodic, axisymmetric combustor section, with the RNG κ-ε turbulence model to resolve turbulent flow details. An overall analysis and performance evaluation of the experimentally tested UCC configuration and an axially shortened cavity baseline configuration was conducted at various experimentally documented operating …

High Temperature Heat Exchanger Project: Quarterly Progress Report April 1, 2006 Through June 30, 2006, Anthony Hechanova

Publications (NSTD)

Numerical Analyses of the Ceramatec Sulfuric Acid Decomposer. Comparisons with experiments for the Ceramatec sulfuric acid decomposer coupon with eight straight channels for four different geometries and four different flow rates were performed. All of the operation and boundary conditions for the calculations were the same as in the Ceramatec experiments. Good agreement was found. The overall pressure drop difference between calculations and experiments for most of the cases is within 10%.

1 - طراحی مناسب نما و پوسته خارجی ساختمان، روشی موثر برای جلوگيری از رخداد ميعان در سيستمهای سرمايشی تابشی سقفی, Alireza Zolfaghari, Mehdi Maerefat, Amir Omidvar

Dr Alireza Zolfaghari

No abstract provided.

Non-Isothermal Reaction-Diffusion Systems With Thermodynamically Coupled Heat And Mass Transfer, Yaşar Demirel

Papers in Analytical Chemistry

Non-isothermal reaction-diffusion (RD) systems control the behavior of many transport and rate processes in physical, chemical, and biological systems. A considerable work has been published on mathematically coupled nonlinear differential equations of RD systems by neglecting the possible thermodynamic couplings among heat and mass fluxes, and reaction velocities. Here, the thermodynamic coupling refers that a flux occurs without its primary thermodynamic driving force, which may be gradient of temperature, or chemical potential, or reaction affinity. This study presents the modeling equations of non-isothermal RD systems with coupled heat and mass fluxes excluding the coupling of chemical reactions using the linear …

High Temperature Heat Exchanger Project: Quarterly Progress Report January 1, 2006 Through March 31, 2006, Anthony Hechanova

Publications (NSTD)

Quarterly Collaboration Meeting. The UNLVRF HTHX Project quarterly meeting was held in Albuquerque, NM, March 16 and 17, 2006. The purpose of the meeting was to promote collaboration and communication among the UNLV Research Foundation partners. A tour of Sandia National Laboratory was also provided that included a visit to their sulfuric acid decomposition test apparatus. There were 24 attendees from universities, national laboratories, and private industry. Collaborators discussed their research progress. The next meeting will be in July in Salt Lake City, UT.

Unlv Research Foundation High Temperature Heat Exchanger Development, Anthony Hechanova

Publications (NSTD)

Barriers addressed:

Nuclear Hydrogen Initiative R&D Plan – Material performance and component design and testing for: intermediate heat exchanger and high-temperature thermochemical water splitting (H2SO4 decomposition and HI decomposition). Improved materials for High Temperature Electrolysis.

Retrofit Of Distillation Columns Using Thermodynamic Analysis, Yaşar Demirel

Papers in Physical Properties

Thermodynamic analysis provides the column grand composite curves and exergy loss profiles, which are becoming readily available for a converged distillation column simulation. For example, the Aspen Plus simulator performs the thermodynamic analysis through its Column–Targeting tool for rigorous column calculations. This study uses the column grand composite curves and the exergy loss profiles obtained from Aspen Plus to assess the performance of the existing distillation columns, and reduce the costs of operation by appropriate retrofits in a methanol plant. Effectiveness of the retrofits is also assessed by means of thermodynamics and economics. The methanol plant utilizes two distillation columns …

Numerical Investigation Of Cavity-Vane Interactions Within The Ultra Compact Combustor, Jonathan F. Anisko

Theses and Dissertations

A numerical analysis and design optimization of the Ultra Compact Combustor (UCC) has been conducted. The UCC is a combustor designed to incorporate high-g loadings to increase flame propagation speed while reducing flame length, thereby helping to significantly reduce the size of a combustor. A commercial CFD package with a k-Ⲉ turbulence model has been used to develop design rules for the construction of future UCCs. There have been several versions of UCC that have been designed, built and tested by AFRL/PRTC. Since real experimental tests are expensive and construction time is prohibitive to test many different design configurations, CFD …

Raghavan, V., Gogos, G., Babu, V. And Sundararajan, T., “Effect Of Gravity On Methanol Diffusion Flames Burning Within A Forced Convective Environment”, Accepted For Publication In International Communications In Heat And Mass Transfer (2006)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson

Theses and Dissertations

Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the …

Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman

Theses and Dissertations

This study investigated the design parameters necessary for the construction and use of a testing facility built to test the combustor section of engines. User inputs were acquired by interview and used in the decisions made in arrangement of pieces of machinery and how different systems were to interact. The design was then carried out as the various parts of the facility were built and installed. Software was designed which controlled the different parts of the combustion process and monitored the different products of combustion as well as the properties of the air and fuel used in the combustion. These …

Pope, D. And Gogos, G. "Numerical Simulation Of Fuel Droplet Extinction Due To Forced Convection," Combustion And Flame, 142:89-106 (2005)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Pope, D.N. And Gogos G. “A New Multicomponent Diffusion Formulation For The Finite-Volume Method: Application To Convective Droplet Combustion,” Numerical Heat Transfer, Part B Fundamentals, Part B, 48, 3:213-234, (2005)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Raghavan, V., Pope, D.N., Howard, D. And Gogos, G. “Surface Tension Effects During Low Reynolds Number Methanol Droplet Combustion,” Combustion And Flame, Accepted (2006)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Raghavan, V., Pope, D.N. And Gogos, G. “Effects Of Forced Convection And Surface Tension During Methanol Droplet Convection,” Aiaa Journal Of Thermophysics And Heat Transfer, Accepted (2006)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Pope, D.N., Howard, D., Lu, K. And Gogos, G. “Combustion Of Moving Droplets And Suspended Droplets: Transient Numerical Results,” Aiaa Journal Of Thermophysics And Heat Transfer, 19:273-281 (2005)

Combustion Research at University of Nebraska-Lincoln

No abstract provided.

Thermally Developing Flow And Heat Transfer In Rectangular Microchannels Of Different Aspect Ratios, Poh-Seng Lee, S V. Garimella

CTRC Research Publications

Laminar convective heat transfer in the entrance region of microchannels of rectangular cross-section is investigated under circumferentially uniform wall temperature and axially uniform wall heat flux thermal boundary conditions. Three-dimensional numerical simulations were performed for laminar thermally developing flow in microchannels of different aspect ratios. Based on the temperature and heat flux distributions obtained, both the local and average Nusselt numbers are presented graphically as a function of the dimensionless axial distance and channel aspect ratio. Generalized correlations, useful for the design and optimization of microchannel heat sinks and other microfluidic devices, are proposed for predicting Nusselt numbers. The proposed …

High Temperature Heat Exchanger Project: Quarterly Progress Report October 1, 2005 Through December 31, 2005, Anthony Hechanova

Publications (NSTD)

• Liquid Salt Technical Working Group Meeting. The first meeting of the Liquid Salt Technical Working Group was held on October 28, 2005 at the Pratt Whitney Rocketdyne facility in Canoga Park, CA. 20 experts from academia, industry, and national laboratories participated to discuss current state of knowledge and research needs for high temperature liquid salt applications.
• Nuclear Hydrogen Initiative Semi-annual Review. Several participants from the UNLVRF University Consortium gave technical presentations at the NHI Semi-annual Review meeting in Rockville, MD, November 9-10, 2005.
• Quarterly Collaboration Meeting. The University of Nevada, Las Vegas hosted a UNLVRF HTHX Project quarterly meeting December …

Application Of An Hp-Adaptive Finite Element Method For Thermal Flow Problems, Xiuling Wang, Darrell Pepper

Mechanical Engineering Faculty Research

Numerical results are presented for a set of convective thermal flow problems using an hp-adaptive finite element technique. The hp-adaptive model is based on mesh refinement and spectral order incensement to produce enhanced accuracy while attempting to minimize computational requirements. An a-posteriori error estimator based on the L₂ norm is employed to guide the adaptation procedure. Example test cases consisting of natural convection in a differentially heated enclosure, flow with forced convection heat transfer over a backward facing step and natural convection within an enclosed partition are presented. Numerical results are compared with published data in the …

Heat And Mass Transfer (Baehr And Stephan), Dr Alireza Zolfaghari

Dr Alireza Zolfaghari

No abstract provided.

A Heat Transfer Textbook (Lienhard), Dr Alireza Zolfaghari

Dr Alireza Zolfaghari

No abstract provided.

Magnetohydrodynamic Simulation Of Electromagnetic Pump In Tc-1, Lillian J. Ratliff

Reactor Campaign (TRP)

The pilot molten lead-bismuth target circuit (TC-1) in university of Nevada Las Vegas (UNLV) was designed for beam power of 1 MW accelerator driven system (ADS). The TC-1 is a liquid lead-bismuth eutectic (LBE) circulation loop. Circulation of the liquid alloy is driven by an annular linear induction pump (ALIP). Experimental measurements of system parameters have yielded a surprisingly low pump efficiency of less than 1%. A numerical study of the pump efficiency is being conducted to determine which operational parameters are responsible for this low efficiency and to give insight into future EM pump design. The numerical study will …

Cool Flames At Terrestrial, Partial, And Near-Zero Gravity, Michael R. Foster, Howard Pearlman

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Natural convection plays an important role in all terrestrial, Lunar, and Martian-based, unstirred, static reactor cool flame and low-temperature autoignitions, since the Rayleigh number (Ra) associated with the self-heating of the reaction exceeds the critical Ra (approximately 600) for onset of convection. At near-zero gravity, Ra < 600 can be achieved and the effects of convection suppressed. To systematically vary the Ra without varying the mixture stoichiometry, reactor pressure, or vessel size, cool flames are studied experimentally in a closed, unstirred, static reactor subject to different gravitational accelerations (terrestrial, 1g; Martian, 0.38g; Lunar, 0.16g; a n dr e - duced gravity, ∼10−2g). Representative results show the evolution of the visible light emission using an equimolar n-butane:oxygen premixture at temperatures ranging from 320 to 350 ◦C (593–623 K) at subatmospheric pressures. For representative reduced-gravity, spherically propagating cool flames, the flame radius based on the peak light intensity is plotted as a function of time and the flame radius (and speed) is calculated from a polynomial fit to data. A skeletal chemical kinetic Gray-Yang model developed previously for a one-dimensional, reactive– diffusive system by Fairlie and co-workers is extended to a two-dimensional axisymmetric, spherical geometry. The coupled species, energy, and momentum equations are solved numerically and the spatio-temporal variations in the temperature profiles are presented. A qualitative comparison is made with the experimental results.

Transient Heat Partition Factor For A Sliding Railcar Wheel, T C. Kennedy, C Plengsaard, Robert F. Harder

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

During a wheel slide the frictional heat generated at the contact interface causes intense heating of the adjacent wheel material. If this material exceeds the austenitising temperature and then cools quickly enough, it can transform into martensite, which may ultimately crack and cause wheel failure. A knowledge of the distribution of the heat partitioned into the wheel and the rail and the resulting temperature fields is critical to developing designs to minimize these deleterious effects. A number of theoretical solutions have appeared in the literature to model the thermal aspects of this phenomenon. The objective of this investigation was to …

Including Embodied Energy Considerations At The Conceptual Stage Of Building Design, Y. Yohanis, Brian Norton

Articles

Elevated operating temperatures reduce the solar to electrical conversion efficiency of building integrated photovoltaic devices (BIPV). Phase change materials (PCM) can be used to passively limit this temperature rise although their effectiveness is limited by their low thermal conductivities and by crystallization segregation during solidification. This paper presents an experimental evaluation of the effects of convection and crystalline segregation in a PCM as a function of efficiency of heat transfer within the finned PV/PCM system. The thermal performances of bulk PCM with crystallization segregation for different internal fin arrangements are presented. It is noted that the addition of internal fins …