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Results of visualization experiments are presented for the entry flow to circular tubes under oscillatory flow conditions. Geometries and conditions have been chosen to simulate the flow in a Stirling engine with straight heat exchanger tubes. Since oscillating flow in Stirling engines is unavoidably strongly influenced by the entry conditions, such documentation is useful when engine designs are being considered and is needed when test results are being interpreted. Two entry geometries are explored, one with unrestricted entry to a squared-edged tube and another with entry from one side. The visualization technique is by illumination of neutrally-buoyant, helium-filled soap bubbles with laser light, capturing with still photography. Each picture is an ensemble of exposures from 150 cycles. Each entry to the ensemble is taken at the same range in crank position, typically five degrees. Thus, one picture may visualize the flow from 75 to 80 degrees of crank rotation, for instance.

Particulate emissions from heavy-duty buses were measured in real time under conditions encountered during the standard Central Business District (CBD) driving cycle. The buses tested were equipped with 1994 Detroit Diesel Engine Corporation 6V92-TA engines, and some included after treatment devices on the exhaust. Instantaneous, time-resolved measurements of CO2 and amorphous carbon concentrations were obtained using an optical extinction technique and compared to simultaneous results obtained using conventional dilution tunnel sampling methods. Good agreement was obtained between the real-time extinction measurements and the diluted CO2 and cycle-integrated filter measurements. The instantaneous measurements revealed that acceleration transients accounted for roughly 80% of the particulate mass emitted during the cycle but only about 45% of the fuel consumption.

Effective thermal and micrometeoroid protection as afforded by the Thermal Micrometeoroid Garment (TMG) is critical in achieving safe and efficient missions. It is also critical that the TMG does not increase torque or decreased range of motion which can cause crewmember discomfort, fatigue, and reduced efficiency. For future exploration missions, removable and replaceable TMGs will allow the use of different pressure garment protective covers and TMG configurations for launch, re-entry, 0-G Extra Vehicular Activity (EVA), and lunar surface EVA. A study was conducted with the goal of developing high Technology Readiness Level (TRL), scalable, interface design concepts for TMG systems. The affects of TMG segmentation on mobility and donning were assessed. Closure mechanisms were investigated and tested to determine their operability after exposure to lunar dust. A TMG configuration with the optimum number of segments and location of interfaces was selected for the Mark III spacesuit.

A trade study was conducted with a goal to develop relatively high TRL design concepts for an Exploration Cooling Garment (ExCG) that can accommodate larger metabolic loads and maintain physiological limits of the crewmembers health and work efficiency during all phases of exploration missions without hindering mobility. Effective personal cooling through use of an ExCG is critical in achieving safe and efficient missions. Crew thermoregulation not only impacts comfort during suited operations but also directly affects human performance. Since the ExCG is intimately worn and interfaces with comfort items, it is also critical to overall crewmember physical comfort. Both thermal and physical comfort are essential for the long term, continuous wear expected of the ExCG.

Hydraulic systems, as power source and transmission, offer many advantages over electromechanical or purely mechanical counterparts in terms of power density, flexibility and portability. Many hydraulic systems require touching and contacting the physical environments; and many of these systems are directly controlled by human. If hydraulic systems are passive, they would be safer to interact with, and easier for human to control. In this paper, we describe our current research in developing bilateral passive teleoperated hydraulic machines which a human operator controls via a force feedback joystick. Two key developments are 1) methodologies to passify the electrohydraulic valves as a two-port device, and 2) the passive teleoperation controllers.

Results of comparisons of computed and measured soot and NO in a direct-injection Diesel engine are presented. The computations are carried out using a three-dimensional model for flows, sprays and combustion in Diesel engines. Autoignition of the Diesel spray is modeled using an equation for a progress variable which measures the local and instantaneous tendency of the fuel to autoignite. High temperature chemistry is modeled using a local chemical equilibrium model coupled to a combination of laminar kinetic and turbulent characteristic times. Soot formation is kinetically controlled and soot oxidation is represented by a model which has a combination of laminar kinetic and turbulent mixing times. Soot oxidation appears to be controlled near top-dead-center by mixing and by kinetics as the exhaust is approached. NO is modeled using the Zeldovich mechanism.

Results of three-dimensional computations of non-vaporizing and vaporizing Diesel sprays in a very high pressure (up to 18.4 MPa without combustion) environment are presented. These pressures and corresponding density ratios of ambient gas to injected liquid are about a factor of two greater than those in current Diesel engines. The spray model incorporates a line source for drops, heat, mass and momentum exchange between the gas and liquid phases, turbulent dispersion of drops, collisions and coalescences, and drop breakup. The accuracy of the model is assessed by making comparisons of computed and measured spray penetrations. Reasonable agreement is obtained for a broad range of conditions. A scaling for time and axial distance clarifies these results.

Earlier work [1] shows that kinetics of Diesel soot oxidation is different from that of ethylene diffusion flame soot oxidation [2], possibly due to metals from lube oil. This study investigates the influence of metals on soot oxidation and the exhaust particle emissions using lube oil dosed fuel (2 % by volume). This method does not simulate normal lube oil consumption, but is used as a means of adding metals to particles for oxidation studies. This study also provides insight into the effect of systems that mix lube oil with fuel to minimize oil change service. The HTO-TDMA (High Temperature Oxidation-Tandem Differential Mobility Analyzer) technique [1] was used to measure the surface specific oxidation rate of Diesel particles over the temperature range 500-750 °C. Diesel particles sampled from the exhaust stream of a Diesel engine were size segregated by differential mobility and oxidized in situ in air in a heated flow tube of known residence time and temperature profile.

Particle size distribution and number concentration measurements have been made in the diluted exhaust of a medium-duty, turbocharged, aftercooled, direct-injection Diesel engine using a unique variable residence time micro-dilution system that allows systematic variation of dilution and sampling conditions, and a scanning mobility particle sizer (SMPS). The measurements show that the number concentrations in the nanoparticle (Dp < 50 nm) and the ultrafine (Dp < 100 nm) ranges are very sensitive to dilution conditions and fuel sulfur content. Changes in concentration of up to two orders of magnitude have been observed when conditions are varied over the range that might be encountered in typical laboratory dilution systems. For example, at a dilution ratio of 12, dilution temperature of 32 °C, and a residence time of 1000 ms, the number concentrations reach 6 × 108 part.

Advanced water processors being developed for NASA's Exploration Initiative rely on phase change technologies and/or biological processes as the primary means of water reclamation. As a result of the phase change, volatile compounds will also be transported into the distillate product stream. The catalytic reactor assembly used in the International Space Station (ISS) water processor assembly, referred to as Volatile Removal Assembly (VRA), has demonstrated high efficiency oxidation of many of these volatile contaminants, such as low molecular weight alcohols and acetic acid, and is considered a viable post treatment system for all advanced water processors. To support this investigation, two ersatz solutions were defined to be used for further evaluation of the VRA. The first solution was developed as part of an internal research and development project at Hamilton Sundstrand (HS), and is based primarily on ISS experience related to the development of the VRA.

Hamilton Sundstrand has developed a scalable evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It was designed to support the Orion Crew Module and to support future Constellation missions. The MFE would be used from Earth sea level conditions to the vacuum of space. This system combines the functions of the Space Shuttle flash evaporator and ammonia boiler into a single compact package with improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing surface area to keep the back pressure low. The multiple layer construction of the core allows for efficient scale up to the desired heat rejection rate. A full-scale unit uses multiple core sections that, combined with a novel control scheme, manage the risk of freezing the heat exchanger cores. A four-core MFE prototype was built in 2007.

Hamilton Sundstrand is under contract with the NASA Johnson Space Center to develop a scalable, evaporative heat rejection system called the Multi-Fluid Evaporator (MFE). It is being designed to support the Orion Crew Module and to support future Constellation missions. A MFE would be used from Earth sea level conditions to the vacuum of space. The current Space Shuttle configuration utilizes an ammonia boiler and flash evaporator system to achieve cooling at all altitudes. With the MFE system, both functions are combined into a single compact package with significant weight reduction and improved freeze-up protection. The heat exchanger core is designed so that radial flow of the evaporant provides increasing cross-sectional area to keep the back pressure low. Its multiple layer construction allows for efficient scale up to the desired heat rejection rate.

A two-dimensional optimization process which simultaneously adjusts the spark timing and air-fuel ratio of a lean-burn natural gas fueled engine has been demonstrated. This has been done by first mapping the thermal efficiency against spark timing and equivalence ratio at a single speed and load combination to obtain the 3-D surface of efficiency versus the other two variables. Then the ability of the control system to find and hold the combination of timing and air-fuel ratio which gives the highest thermal efficiency was explored. The control system described in SAE Paper No. 940546 was used to map the thermal efficiency versus equivalence ratio and ignition timing. NOx, CO, and HC maps were also obtained to determine the tradeoffs between efficiency and emissions. A load corresponding to a brake mean effective pressure of 0.467 MPa was maintained by a water brake dynamometer. A speed of 2000 rpm was maintained by a fuel-controlled governor.

Two types of in-cylinder optical probes were applied to a single cylinder CFR engine to detect knocking combustion. The first probe was integrated directly into the engine spark plug to monitor the radiation from burned gas in the combustion process. The second was built into a steel body and installed near the end gas region of the combustion chamber. It measured the radiant emission from the end gas in which knock originates. The measurements were centered in the near infrared region because thermal radiation from the combustion products was believed to be the main source of radiation from a spark ignition engine. As a result, ordinary photo detectors can be applied to the system to reduce its cost and complexity. It was found that the measured luminous intensity was strongly dependent upon the location of the optical sensor.

In this work, engine-out particle mass (PM) and particle number (PN) emissions were experimentally examined from a gasoline direct injection (GDI) engine operating in two lean combustion modes and one stoichiometric mode with a fuel of known properties. Ten steady state operating points, two constant speed load steps, and an engine cold start were examined. Results showed that solid particles emitted from the engine under steady state stoichiometric conditions had a uniquely broad size distribution that was relatively flat between the diameters of 10 and 100 nm. In most operating conditions, lean homogenous modes can achieve lower particle emissions than stoichiometric modes while improving engine thermal efficiency. Alternatively, lean stratified operating modes resulted in significantly higher PN and PM emissions than both lean homogeneous and stoichiometric modes with increased efficiency only at low engine load.

The effects of fuel sulfur content and dilution conditions on diesel engine PM number emissions have been researched extensively through steady state testing. Most results show that the concentration of nuclei-mode particles emitted increases with fuel sulfur content. A few studies further observed that fuel sulfur content has little effect on the emissions of heavily-used engines. It has also been found that primary dilution conditions can have a large impact on the size and number distribution of the nuclei-mode particles. These effects, however, have not yet been fully understood through transient testing, the method used by governments worldwide to certify engines and regulate emissions, and a means of experimentation which generates realistic conditions of on-road vehicles by varying the load and speed of the engine.

A system has been developed that allows near real time measurements of total, volatile, and nonvolatile particle concentrations in engine exhaust. It consists of a short section of heated catalyst, a cooling coil, and an electrical aerosol analyzer. The performance of this catalytic stripper system has been characterized with nonvolatile (NaCl), volatile sulfate ((NH4)2 SO4), and volatile hydrocarbon (engine oil) particles with diameters ranging from 0.05-0.5 μm. The operating temperature of 300°C gives essentially complete removal of volatile sulfate and hydrocarbon particles, but also leads to removal of 15-25% of solid particles. This system has been used to determine total, volatile, and nonvolatile particle concentrations in the exhaust of a Diesel engine and a spark ignition engine. Volatile volume fractions measured in Diesel exhaust with the catalytic stripper system increased from 19-65% as the equivalence ratio (load) decreased from 0.64-0.13.

Future spacesuit systems for the exploration of Mars will need to be much lighter than current designs, while at the same time reducing the consumption of water for crew cooling. One of the technology paths NASA has identified to achieve these objectives is the replacement of current high pressure oxygen storage technology in extravehicular activity (EVA) systems with cryogenic technology that can simultaneously reduce the mass of tankage required for oxygen storage and enable the use of the stored oxygen as a means of cooling the EVA astronaut. During the past year NASA has funded production of a prototype system demonstrating this capability in a design that will allow the cryogenic oxygen to be used in any attitude and gravity environment. This paper describes the design and manufacture of the prototype system. The potential significance and application of the system is also discussed.

An EMU water processing kit (Airlock Coolant Loop Recovery – A/L CLR) was developed as a corrective action to Extravehicular Mobility Unit (EMU) coolant flow disruptions experienced on the International Space Station (ISS) in May of 2004 and thereafter. Conservative schedules for A/L CLR use and component life were initially developed and implemented based on prior analysis results and analytical modeling. The examination of post-flight samples and EMU hardware in November of 2006 indicated that the A/L CLR kits were functioning well and had excess capacity that would allow a relaxation of the initially conservative schedules of use and component life. A relaxed use schedule and list of component lives were implemented thereafter. Since the adoption of the relaxed A/L CLR schedules of use and component lives, several A/L CLR kit items, transport loop water samples and sensitive EMU transport loop components have been examined to gage the impact of the relaxed requirements.

Following the Columbia accident, the EMUs (Extravehicular Mobility Units) onboard the ISS (International Space Station) went unused for an extended period of time. Upon startup, the units experienced a failure in the coolant systems. The failure resulted in a loss of EVA (Extravehicular Activity) capability from the US segment of the ISS. A failure investigation determined that chemical and biological contaminants and byproducts from the ISS Airlock Heat Exchanger, and the EMU itself, fouled the magnetically coupled pump in the EMU Transport Loop Fan/Pump Separator leading to a lack of coolant flow. Remediation hardware (the Airlock Coolant Loop Remediation water processing kit) and a process to periodically clean the EMU coolant loops on orbit were devised and implemented. The intent of this paper is to report on the successful implementation of the resultant hardware and process, and to highlight the go-forward plan.