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A fast time-scale 1-D dynamic diesel particulate filter model capable of resolving the pressure pulsations due to individual cylinder firing events is presented. The purpose of this model is to investigate changes in the firing frequency component of the pulsating exhaust flow at different particulate loadings. Experimental validation data and simulation results clearly show that the magnitude and phase of the firing frequency components are directly correlated to the mass of particulate stored in a diesel particulate filter. This dynamic pressure signal information may prove particularly useful for monitoring particulate load during vehicle operation.

This paper presents the Statistical Energy Approach (SEA) method for estimating the gross response in complex interconnected structural systems. The method is intended to compensate for the difficulties present in evaluating parameters and excitation needed when attempting to use traditional methods of linear vibration analysis. The amount of information needed to apply the method is modest and the formulas are easy to use. Some limitation on application is demonstrated by a detailed example.

Near-Field Acoustical Holography (NAH) is an inverse process in which sound pressure measurements made in the near-field of an unknown sound source are used to reconstruct the sound field so that source distributions can be clearly identified. NAH was originally based on performing spatial transforms of arrays of measured pressures and then processing the data in the wavenumber domain, a procedure that entailed the use of very large microphone arrays to avoid spatial truncation effects. Over the last twenty years, a number of different NAH methods have been proposed that can reduce or avoid spatial truncation issues: for example, Statistically Optimized Near-Field Acoustical Holography (SONAH), various Equivalent Source Methods (ESM), etc.

Driveline and suspension notched components of off-road ground vehicles often experience multiaxial fatigue failures along notch locations. Large nominal load histories may induce local elasto-plastic stress and strain responses at the critical notch locations. Fatigue life prediction of such notched components requires detailed knowledge of local stresses and strains at notch regions. The notched components that are often subject to multiaxial loadings in services, experience complex stress and strain responses. Fatigue life assessment of the components utilizing non-linear Finite Element Analysis (FEA) require unfeasibly inefficient computation times and large data. The lack of more efficient and effective methods of elasto-plastic stress-strain calculation may lead to the overdesign or earlier failures of the components or costly experiments and inefficient non-linear FEA.

Ames Research Center’s Life Sciences Division has developed and flown an extensive array of spaceflight experiment unique equipment (EUE) during the last decade of the twentieth century. Over this ten year span, the EUE developed at ARC supported a vital gravitational biology flight research program executed on several different platforms, including the Space Shuttle, Spacelab, and Space Station Mir. This paper highlights some of the key EUE elements developed at ARC and flown during the period 1990-1999. Resulting lessons learned will be presented that can be applied to the development of similar equipment for the International Space Station.

Multidimensional models are increasingly employed to predict NO and soot emissions from Diesel engines. In the traditional approach, the ensemble-averaged values of variables are employed in the expressions for NO and soot formation and oxidation. In the mixture fraction averaged approach, the values of state variables and species concentrations are obtained from the structure of laminar diffusion flames. The source terms for NO and soot are then obtained by averaging across the mixture fraction coordinate with a probability density function. The clipped-Gaussian probability density function and profiles obtained by employing the OPPDIF code (part of the CHEMKIN package) for the laminar flame structure are employed in this work. The Zeldovich mechanism for NO formation and the Moss et al. formation and Nagle-Strickland-Constable oxidation model for soot have been employed to study the qualitative trends of pollutants in transient combusting Diesel jets.

Bioregenerative systems for removal of gaseous contaminants are desired for long-term space missions to reduce the equivalent system mass of the air cleaning system. This paper describes an innovative design of a new biofiltration test lab for investigating the capability of biofiltration process for removal of ersatz multi-component gaseous streams representative of spacecraft contaminants released during long-term space travel. The lab setup allows a total of 24 bioreactors to receive identical inlet waste streams at stable contaminant concentrations via use of permeations ovens, needle valves, precision orifices, etc. A unique set of hardware including a Fourier Transform Infrared (FTIR) spectrometer, and a data acquisition and control system using LabVIEW™ software allows automatic, continuous, and real-time gas monitoring and data collection for the 24 bioreactors. This lab setup allows powerful factorial experimental design.

Gas engines often utilize a small-volume pre-chamber in which fuel is injected at near stoichiometric condition to produce a hot turbulent jet which then ignites the lean mixture in the main chamber. Hot jet ignition has several advantages over traditional spark ignition, e.g., more reliable ignition of extra-lean mixtures and more surface area for ignition resulting in faster burning and improved combustion burn time. Our previous experimental results show that supersonic jets could extend the lean flammability limit of fuel/air mixtures in the main chamber in comparison to subsonic jets. The present paper investigated the characteristics of supersonic hot jets generated by combustion of stoichiometric H2/air in a pre-chamber to understand the ignition mechanism of ultra-lean mixtures by supersonic hot jets.

An experimental-analytic method of determining the stress distribution in narrow faced spur gear teeth is presented. The successful application of photostress to this contact problem is reported. It utilizes a digital computer routine developed for separating stresses in any general two-dimensional region. Results for two pairs of gears are presented. Comparison is made with values predicted by the modified Lewis formula, the Kelley and Pedersen equation, and by the Belajef solution of the Hertz contact problem for two cylinders.

In February 2004 NASA released “The Vision for Space Exploration.” The goals outlined in this document include extending the human presence in the solar system, culminating in the exploration of Mars. A key requirement for this effort is to identify a safe and effective method to process waste. Methods currently under consideration include incineration, microbial oxidation, pyrolysis, drying, and compaction. Although each has advantages, no single method has yet been developed that is safe, recovers valuable resources including oxygen and water, and has low energy and space requirements. Thus, the objective of this work was to develop a low temperature oxidation process to convert waste cleanly and rapidly to carbon dioxide and water. TDA and NASA Ames Research Center have developed a pilot scale low temperature ozone oxidation system to convert organic waste to CO2 and H2O.

This paper reviews some applications of lattice Boltzmann methods (LBM) to compute multiphase flows. The method is based on the solution of a kinetic equation which describes the evolution of the distribution of the population of particles whose collective behavior reproduces fluid behavior. The distribution is modified by particle streaming and collisions on a lattice. Modeling of physics at a mesoscopic level enables LBM to naturally incorporate physical properties needed to compute complex flows. In multiphase flows, the surface tension and phase segregation are incorporated by considering intermolecular attraction forces. Furthermore, the solution of the kinetic equations representing linear advection and collision, in which non-linearity is lumped locally, makes it parallelizable with relative ease. In this paper, a brief review of the lattice Boltzmann method relevant to engine sprays will be presented.

This work presents a simple and useful project process model. The project model directly shows how a few basic parameters determine project duration and cost and how changes in these parameters can improve them. Project cost and duration can be traded-off by adjusting the work rate and staffing level. A project's duration and cost can be computed on the back of an envelope, with an engineering calculator, or in a computer spreadsheet. The project model can be simulated dynamically for further insight. The project model shows how and why projects can greatly exceed their expected duration and cost. Delays and rework requirements may create work feedback loops that increase cost and schedule in non-proportional and non-intuitive ways.

This paper describes a simulation approach for the modeling of tandem external gear pumps. A tandem gear pump is the combination of two pumps with a common drive shaft. Such design architecture finds application in certain automotive transmission systems. The model presented in this work is applicable for pumps with both helical and spur gears. The simulation model is built on the HYGESim (HYdraulic GEars machines Simulator) previously developed by the authors for external spur gear units. In this work, the model formulation is properly extended to the capabilities of simulating helical gears. Starting directly from the CAD drawings of the unit, the fluid-dynamic model solves the internal instantaneous tooth space volume pressures and the internal flows following a lumped parameter approach. The simulation tool considers also the radial micro-motion of the gears, which influences the internal leakages and the features of the meshing process.

Samples of Mars surface material will return to Earth in 2014. Prior to curation and distribution to the scientific community the returned samples will be isolated in a special facility until their biological safety has been assessed following protocols established by NASA’s Planetary Protection Office. The primary requirements for the pre-release handling of the Martian samples include protecting the samples from the Earth and protecting the Earth from the sample. A testbed will be established to support the design of such a facility and to test the planetary protection protocols. One design option that is being compared to the conventional Biological Safety Level 4 facility is a double walled differential pressure chamber with airlocks and automated equipment for analyzing samples and transferring them from one instrument to another.

In this paper, a wall-modified interactive flamelet model is developed for improving the modeling of Diesel combustion. The objective is to include the effects of wall heat loss on the transient flame structure. The essential idea is to compute several flamelets with several representative enthalpy defects which account for wall heat loss. Then, the averaged flamelet profile can be obtained through a linear fit between the flamelets according to the enthalpy defect of the local gas which results from the wall heat loss. The enthalpy defect is estimated as the difference between the enthalpy in a flamelet without wall heat loss, which would correspond to the enthalpy in the gas without wall heat loss, and the gas with wall heat loss. The improved model is applied to model combustion in a Diesel engine. In the application, two flamelets, one without wall heat loss and one with wall heat loss, are considered.

Early experience with precision farming technology suggests that some hardware and software may follow a rapid S curve adoption path, but that the use of integrated precision farming systems may take longer to develop and be subject to false starts and periods of stagnation. Yield monitors appear to be following a classic S curve adoption path. Precision farming adoption is like that of hybrid corn because changes in organizations will be required to use it effectively. It is like motorized mechanization because it is coming on the market in an immature form and lends itself to farmer tinkering.

Direct osmotic concentration (DOC) is an integrated membrane treatment process designed for the reclamation of spacecraft wastewater. The system includes forward osmosis (FO), membrane evaporation, reverse osmosis (RO) and an aqueous phase catalytic oxidation (APCO) post-treatment unit. This document describes progress in the third year of a four year project to advance hardware maturity of this technology to a level appropriate for human rated testing. The current status of construction and testing of the final deliverable is covered and preliminary calculations of equivalent system mass are funished.

The Elytron 2S is a prototype aircraft concept to allow VTOL capabilities together with fixed wing aircraft performance. It has a box wing design with a centrally mounted tilt-wing supporting two rotors. This paper explores the aerodynamic characteristics of the aircraft using computational fluid dynamics in hover and low speed forward flight, as well as analyzing the unique control system in place for hover. The results are then used to build an input set for NASA Design and Analysis if Rotorcraft software allowing trim and flight stability and control estimations to be made with SIMPLI-FLYD.

Experimental measurements of a 1:20-scale tractor-trailer configuration were obtained in the 48- by 32-Inch Subsonic Wind Tunnel at NASA Ames Research Center. The model included significant details of the underbody geometries of both the tractor and trailer. In addition, the tractor included a flow-through grill and a simplified engine block to provide an approximation of the flow through the engine compartment. The experiment was conducted at a Reynolds Number of 430,000 for yaw angles between ±14 deg. The measurements included forces and moments and static surface pressures for various underbody configurations. Simple fairings on the underbodies of the tractor and trailer both yielded a reduction in the wind-averaged drag coefficient of 0.018 (2.7%) when tested separately. A horizontal plate designed to block vertical flow in the tractor-trailer gap provided marginally higher drag reduction (0.021, or 3.2%).

This paper describes research and development for reducing the aerodynamic drag of heavy vehicles by demonstrating new approaches for the numerical simulation and analysis of aerodynamic flow. Experimental validation of new computational fluid dynamics methods are also an important part of this approach. Experiments on a model of an integrated tractor-trailer are underway at NASA Ames Research Center and the University of Southern California (USC). Companion computer simulations are being performed by Sandia National Laboratories (SNL), Lawrence Livermore National Laboratory (LLNL), and California Institute of Technology (Caltech) using state-of-the-art techniques.