Refine Your Search




Search Results

Technical Paper

10 KWe Dual-Mode Space Nuclear Power System for Military and Scientific Applications

A 10 KWe dual-mode space power system concept has been identified which is based on INEL's Small Externally-fueled Heat Pipe Thermionic Reactor (SEHPTR) concept. This power system will enhance user capabilities by providing reliable electric power and by providing two propulsion systems; electric power for an arc-jet electric propulsion system and direct thrust by heating hydrogen propellant inside the reactor. The low thrust electric thrusters allow efficient station keeping and long-term maneuvering. The direct thrust capability can provide tens of pounds of thrust at a specific impulse of around 730 seconds for maneuvers that must be performed more rapidly. The direct thrust allows the nuclear power system to move a payload from Low Earth Orbit (LEO) to Geosynchronous Earth Orbit (GEO) in less than one month using approximately half the propellant of a cryogenic chemical stage.
Technical Paper

1970s Development of 21st Century Mobile Dispersed Power

A mobile and dispersed power system is necessary for an advanced technological-industrial society. Today's petroleum-based system discharges waste products and heat and is growing exponentially. Energy resource commitment has already intersected “ultimate” low-cost petroleum supplies in the United States and will do so for the world before 2000; this portends major changes and cost increases. The twenty-first century system for mobile-dispersed power will reflect the energy source selected to replace petroleum-for example, coal, solar insolation, or uranium. It will incorporate a fuel intermediate such as methanol, ammonia, or hydrogen, and a suitably matched “engine.” The complete change will require more than 25 years because of the magnitude, fragmentation, structural gaps, complexity, and variety of the mobile-dispersed power system.
Technical Paper

90 Ah Dependent Pressure Vessel (DPV) Nickel Hydrogen Battery Qualification Test Results

In 1995, the Naval Research Laboratory (NRL) began a program to investigate whether a 90 Ah dependent pressure vessel (DPV) NiH2 battery pack could be a lower volume replacement for a 90 Ah NiH2 IPV spacecraft battery. Nickel Hydrogen (NiH2) dependent pressure vessel (DPV) battery cells are presumed to offer all the features of the NiH2 IPV battery cell with considerably less volume. To achieve this reduction in volume, the DPV cell utilizes a canteen shaped pressure vessel with reduced thickness wall, flat sides and curved ends. The cells can be packaged similar to prismatic nickel cadmium battery cells. Moreover, like NiCd cells, a fully charged DPV cell must rely upon an adjacent battery cell or structure for support and to maintain pressure vessel integrity. Seventeen 90 Ah NiH2 DPV cells were delivered to NR in 1998 for qualification tests. An eleven-cell half battery pack was manufactured and tested to validate the advantages of the DPV design.
Technical Paper

A 3D-Simulation with Detailed Chemical Kinetics of Combustion and Quenching in an HCCI Engine

A 3D-CFD model with detailed chemical kinetics was developed to investigate the combustion characteristics of HCCI engines, especially those fueled with hydrogen and n-heptane. The effects of changes in some of the key important variables that included compression ratio and chamber surface temperature on the combustion processes were investigated. Particular attention was given, while using a finer 3-D mesh, to the development of combustion within the chamber crevices between the piston top-land and cylinder wall. It is shown that changes in the combustion chamber wall surface temperature values influence greatly the autoignition timing and location of its first occurrence within the chamber. With high chamber wall temperatures, autoignition takes place first at regions near the cylinder wall while with low surface temperatures; autoignition takes place closer to the central region of the mixture charge.
Technical Paper

A Before Treatment Method for Reduction of Emissions in Diesel Engines

Through an addition of a small amount of hydrogen to the main fuel, combustion process can be considerably enhanced in internal combustion engines producing significantly lower levels of exhaust emissions. This improvement in combustion can be mainly attributed to the faster and cleaner burning characteristics of hydrogen in comparison to conventional liquid and gaseous fuels. An oxygen-enrichment of a fuel-air mixture also improves thermal efficiency and reduces especially particulate, carbon monoxide and unburned hydrocarbon emissions in exhaust. This contribution describes the results of experimental investigation where a small amount of hydrogen and oxygen is produced by Hydrogen Generating System through the electrical dissociation of water and are added to the intake of a compression ignition engine operating on a commercial diesel fuel. It is shown that level of exhaust emissions including NOx can be moderately reduced using such a pre-treatment method in diesel engines.
Technical Paper


For fuelling road transportation in the future, particularly light-duty vehicles, there has been much speculation about the use of hydrogen and fuel cells to provide electrical power to an all-electric drive train. An alternative powertrain would use a simple battery to store electricity directly, using power from the electrical grid to charge the battery when the vehicle is not in use. The energy efficiency of these two different approaches has been compared, using a complete “energy conversion chain analysis”. The successful development and introduction into the marketplace of grid-connected hybrid vehicles could eliminate the need for road vehicles to use petroleum fuels, at least for the majority of miles traveled. If electricity were to be generated primarily from sustainable primary energy sources, then road transportation would also become sustainable, resulting in an “Electricity Economy”, rather than a “Hydrogen Economy.
Technical Paper

A Characterization of Exhaust Emissions from Lean Burn, Rotary, and Stratified Charge Engines

This paper reports the results of an exhaust emissions characterization from the non-catalyst control systems employed on the Mazda RX-4 rotary, the Honda CVCC, and the Chrysler electronic lean burn. Throughout the paper, exhaust emissions from these vehicles are compared to those from a Chrysler equipped with an oxidation catalyst and an air pump. The emissions characterized are carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, sulfates, hydrogen sulfide, carbonyl sulfide, hydrogen cyanide, aldehydes, particulate matter, and detailed hydrocarbons. A brief description of the sampling and analysis procedures used is included within the discussion.
Technical Paper

A Combustion Products Analyzer for Contingency Use During Thermodegradation Events on Spacecraft

As mission length and the number and complexity of payload experiments increase, so does the probability of thermodegradation contingencies (e.g. fire, chemical release and/or smoke from overheated components or burning materials), which could affect mission success. When a thermodegradation event occurs on board a spacecraft, potentially hazardous levels of toxic gases could be released into the internal atmosphere. Experiences on board the Space Shuttle have clearly demonstrated the possibility of small thermodegradation events occurring during even relatively short missions. This paper will describe the Combustion Products Analyzer (CPA), which is being developed under the direction of the Toxicology Laboratory at Johnson Space Center to provide necessary data on air quality in the Shuttle following a thermodegradation incident.
Journal Article

A Comparative Assessment of Electric Propulsion Systems in the 2030 US Light-Duty Vehicle Fleet

This paper quantifies the potential of electric propulsion systems to reduce petroleum use and greenhouse gas (GHG) emissions in the 2030 U.S. light-duty vehicle fleet. The propulsion systems under consideration include gasoline hybrid-electric vehicles (HEVs), plug-in hybrid vehicles (PHEVs), fuel-cell hybrid vehicles (FCVs), and battery-electric vehicles (BEVs). The performance and cost of key enabling technologies were extrapolated over a 25-30 year time horizon. These results were integrated with software simulations to model vehicle performance and tank-to-wheel energy consumption. Well-to-wheel energy and GHG emissions of future vehicle technologies were estimated by integrating the vehicle technology evaluation with assessments of different fuel pathways. The results show that, if vehicle size and performance remain constant at present-day levels, these electric propulsion systems can reduce or eliminate the transport sector's reliance on petroleum.
Technical Paper

A Comparative Review of Fuel Cell Vehicles (FCVs) and Hybrid Electric Vehicles (HEVs) Part II: Control Strategies, Power Train, Total Cost, Infrastructure, New Developments, and Manufacturing & Commercialization

In this paper, a number of issues of concern in relation to hybrid electric vehicles (HEVs) and fuel cell vehicles (FCVs) are discussed and comparatively reviewed. Currently, almost all the activities in the development of new generation of vehicles are focused on FCVs and HEVs. However, there are still uncertainties as to which provides the maximum benefits in terms of performance, energy savings, impact on environment etc. In particular, potential control strategies for FCVs and HEVs will be discussed and compared. For FCVs, these include power-averaging control as well as control based on maximum conversion efficiency, among others. HEV control strategies include electrically peaking hybrid propulsion, and parameter optimization approaches such as battery SOC maximization, emissions minimization, and optimal power management.
Technical Paper

A Comparative Study on Different Methods of Using Waste Cooking Oil as Fuel in a Compression Ignition Engine

Different methods to improve the performance of a WCO (waste cooking oil of sunflower) based mono cylinder compression ignition (CI) engine were investigated. Initially WCO was converted into its emulsion by emulsification process and tested as fuel. In the second phase, the engine intake system was modified to admit excess oxygen along with air to test the engine with WCO and WCO emulsion as fuels under oxygen enriched environment. In the third phase, the engine was modified to work in the dual fuel mode with hydrogen being used as the inducted fuel and either WCO or WCO emulsion used as the pilot fuel. All the tests were carried out at 100% and 40% of the maximum load (3.7 kW power output) at the rated speed of 1500 rpm. Engine data with neat diesel and neat WCO were used for comparison. WCO emulsion indicated considerable improvement in performance. The smoke and NOx values were noted to be less than neat WCO.
Technical Paper

A Comparison of Hydrogen and Propane Fueling of an Internal Combustion Engine

An LP-gas industrial engine was adapted operation on hydrogen or LP-gas so that a comparative analysis of the two fuels could be made. Several alterations were made to the engine to allow operation on hydrogen without backfiring. Performance and cylinder pressures of the engine on the two separate fuels was evaluated under various conditions. The effect on engine performance of water induction for controlling backfiring was also studied. The basic intent of the research program was to evaluate the use of hydrogen for an agricultural engine application.
Technical Paper

A Comparison of Methanol and Dissociated Methanol Illustrating Effects of Fuel Properties on Engine Efficiency—Experiments and Thermodynamic Analyses

Methanol, a popular alternative fuel candidate, can theoretically be dissociated on-board a vehicle into a 2/1 molar mixture of hydrogen (H2) and carbon monoxide (CO) having a 14 percent greater heating value than that of methanol vapor. In this study, engine efficiency and fuel consumption with methanol vapor and dissociated methanol (simulated by a 2/1 mixture of Ha and CO) were compared in a single-cylinder engine at equivalence ratios (Φ’s) ranging from 0.5 to 0.9 and compression ratios (CR’s) from 11 to 14. Whan compared at the same Φ and CR, the reduction in fuel consumption for dissociated methanol compared to methanol (3-7 percent) was smaller than would be expected based on heating value alone. Indicated thermal efficiency with dissociated methanol was only 0.89-0.55 times that with methanol. Thermodynamic analyses were conducted to isolate the factors responsible for lower efficiency with dissociated methanol.
Technical Paper

A Comparison of Olefin and Paraffin Autoignition chemistries: A Motored-Engine Study

The autoignition chemistries of the olefins 1-butene, 2-butene, isobutene, 2-methyl-2-butene, and 1-hexene and their corresponding paraffins were examined in a motored, single-cylinder engine by measuring stable intermediate species and performing heat-release analyses. The same engine conditions were used for each olefin-paraffin pair, and compression ratio was varied to affect different levels of chemical activity. Paraffin autoignition chemistry is dominated by hydrogen abstraction from the fuel, followed by the intramolecular alkylperoxy isomerization mechanism. Olefin autoignition chemistry differs markedly being controlled by radical addition to the double bond. Hydroxyl radical addition is followed by oxygen addition to the adjacent radical site, followed by scission forming two carbonyls. Hydroperoxyl radical addition yields an epoxy directly. Experimental measurements for each olefin-paraffin pair are compared with each other and with literature values.
Technical Paper

A Comparison of the Magnetic Properties of Hot Repressed and 7.4 g/cm3 Iron and 0.45% Phosphorus Iron Cores

Atomized iron powder was screened to narrow fractions and annealed. Intermetallic Fe3P powder was blended with the fractions to provide an alloy containing 0.45% phosphorus after sintering. Cores were pressed to a density of 7.4 g/cm3 and sintered at temperatures ranging from 1600°F (870°C) to 2600°F (1430°C) in hydrogen. Magnetic properties were determined from the sintered cores and compared with previous properties measured for iron and hot repressed 0.45% phosphorus iron. It was found that the induction at any density level was approximately 500 gausses (0.05 teslas) lower than for iron. Remanent magnetization was influenced by the size of the pores. If pores were large, remanent magnetization was 8 K gausses (0.8 teslas) and increased to 12 K gausses (1.2 teslas) as the pores become finer. Both maximum permeability and the coercive force were improved when 0.45% phosphorus was added.
Technical Paper

A Comparison of the Radiation Environments in Deep Space

Both humans and onboard radiosensitive systems (electronics, materials, payloads and experiments) are exposed to the deleterious effects of the harsh space radiations found in the space environment. The purpose of this paper is to present the space radiation environment extended to deep space based on environment models for the moon, Mars, Jupiter, and Saturn and compare these radiation environments with the earth's radiation environment, which is used as a comparative baseline. The space radiation environment consists of high-energy protons and electrons that are magnetically “trapped” in planetary bodies that have an intrinsic magnetic field; this is the case for earth, Jupiter, and Saturn (the moon and Mars do not have a magnetic field). For the earth this region is called the “Van Allen belts,” and models of both the trapped protons (AP-8 model) and electrons (AE-8 model) have been developed.
Technical Paper

A Critical Review of Experimental Research on Hydrogen Fueled SI Engines

The literature on hydrogen fueled internal combustion engines is surprisingly extensive and papers have been published continuously from the 1930's up to the present day. Ghent University has been working on hydrogen engines for more than a decade. A summary of the most important findings, resulting from a literature study and the experimental work at Ghent University, is given in the present paper, to clarify some contradictory claims and ultimately to provide a comprehensive overview of the design features in which a dedicated hydrogen engine differs from traditionally fueled engines. Topics that are discussed include abnormal combustion (backfire, pre-ignition and knock), mixture formation techniques (carbureted, port injected, direct injection) and load control strategies (power output versus NOx trade-off).
Technical Paper

A Dual Fuel Hydrogen - Diesel Compression Ignition Engine and Its Potential Application in Road Transport

In this paper investigations of hydrogen use as a main fuel for a compression ignition engine with pilot injection of diesel fuel will be presented. The experiments were performed in steady state conditions on a single cylinder research compression ignition engine with a bore of 85 mm and piston stroke of 90 mm, coupled with an electric dynamometer. The diesel engine with optimized compression ratio was equipped with a diesel fuel direct injection common rail system. A homogeneous mixture of air and hydrogen was formed using a port fuel injection. The influence of hydrogen share on total fuel energy was systematically investigated between limits given by the pure diesel operation and up to a maximum hydrogen share, reaching 98% by energy. The tested hydrogen share was constrained by practical limits at various loads between 4 and 16 bar of IMEP with simulation of the real turbocharger performance and at three engine speeds.
Technical Paper

A Fast Start-Up On-Board Diesel Fuel Reformer for NOx Trap Regeneration and Desulfation

This paper describes recent progress in our program to develop an emissions technology allowing diesel engines to meet the upcoming 2007/2010 regulations for NOx. At the heart of this technology is the ArvinMeritor Diesel Fuel Reformer that reforms the fuel, on-demand, on-board a vehicle. The fuel reformer uses plasma to partially oxidize a mixture of diesel fuel and air creating a highly reducing mixture of Hydrogen and Carbon monoxide. In a previous publication, we have demonstrated that using a reformate rich in H2 and CO to regenerate a NOx trap is highly advantageous compared to vaporized diesel fuel used conventionally. In this paper we present results and a strategy for performing desulfation of the traps using the fuel reformer. In contrast to vaporized diesel, which requires very high temperatures that fall outside the normal exhaust operating temperatures for diesel engines, desulfation was achieved at temperatures lower by more than 100 °C using the Plasma Fuel Reformer.
Technical Paper

A Fast-Response Flame Ionization Detector for Exhaust Hydrocarbons

A hydrogen flame ionization detector with a specially designed sample inlet system has been developed which makes it possible to monitor continuously and accurately the total hydrocarbon content of exhaust gases from a cyclically operating engine. The apparatus has a sample delay time (that is, the time required for the exhaust sample to travel from the sampling point to the detector) of about 1 sec, enabling it to follow rapidly changing engine operating conditions. Hydrocarbon emission (HCE) measurements with the fast-response detector are shown to be substantially higher and more indicative of absolute hydrocarbon concentration than values obtained using nondispersive infrared equipment according to the California test procedure. In addition, sample delay time is shown to affect apparent HCE values.