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Acoustic standing waves are excited in internal combustion chambers by both normal combustion and autoignition. The energy in these acoustic modes can be transmitted through the engine block and radiated as high-frequency engine noise. Using finite-element models of two different (four-valve and two-valve) production engine combustion chambers, the mode shapes and relative frequencies of the in-cylinder volume acoustic modes are calculated as a function of crank angle. The model is validated by comparison to spectrograms of experimental time-sampled waveforms (from flush-mounted cylinder pressure sensors and accelerometers) from these two typical production spark-ignited engines.

An innovative design that meets both Shuttle and Space Station requirements for a user-friendly, volume-efficient, portable glovebox system has been developed at Ames Research Center (ARC). The Standard Interface Glovebox (SIGB) has been designed as a two Middeck locker-sized system that mounts in a Middeck Rack Structure (MRS) or in any rack using the Standard Interface Rack (SIR) rail spacing. The MRS provides structural support for the SIGB during all aspects of the mission and is an interface consistent with NASA's desire for commonality of mechanical interfaces, allowing the SIGB to be flown on essentially any manned space platform. The SIGB provides an enclosed work volume which operates at negative pressure relative to ambient, as well as excellent lighting and ample work volume for anticipated life sciences-related experiment operations inflight.

A three country effort (U.S., Russia, and Bulgaria) has upgraded the plant growth facilities on the Mir Space Station and used the new facility to grow wheat for 90 days. The Svet plant-growth facility was reactivated and used in an initial experiment as part of the Shuttle/Mir program, August to November, 1995. The Svet system, used first to grow cabbage and radish during a 1990 experiment, was augmented by the addition of a U.S. developed Gas Exchange Measurement System (GEMS) that measures a range of environmental parameters plus transpiration, photosynthesis, and possibly respiration. Environmental parameters include cabin, chamber, root-zones, and leaf temperatures. Light levels, relative humidity, oxygen, and atmospheric pressure are also measured. High-accuracy water-vapor and carbon-dioxide concentrations and differences are measured using specially developed IRGA systems.

During 1995, we tested instruments and attempted a seed-to-seed experiment with Super-Dwarf wheat in the Russian Space Station Mir. Utah instrumentation included four IR gas analyzers (CO2 and H2O vapor, calculate photosynthesis, respiration, and transpiration) and sensors for air and leaf (IR) temperatures, O2, pressure, and substrate moisture (16 probes). Shortly after planting on August 14, three of six fluorescent lamp sets failed; another failed later. Plastic bags, necessary to measure gas exchange, were removed. Hence, gases were measured only in the cabin atmosphere. Other failures led to manual watering, control of lights, and data transmission. The 57 plants were sampled five times plus final harvest at 90 d. Samples and some equipment (including hard drives) were returned to earth on STS-74 (Nov. 20). Plants were disoriented and completely vegetative. Maintaining substrate moisture was challenging, but the moisture probes functioned well.

The three-dimensional non-reacting flow field inside a typical dual-monolith automotive catalytic converter was simulated using finite difference analysis. The monolithic brick resistance was formulated from the pressure gradient of fully developed laminar duct-flow and corrected for the entrance effect. This correlation was found to agree with experimental pressure drop data, and was introduced as an additional source term into the non-dimensional momentum governing equation within the brick. Flow distribution within the monolith was found to depend strongly on the diffuser performance, which is a complex function of flow Reynolds number, brick resistance, and inlet pipe length and bending angles. A distribution index was formulated to quantify the degree of non-uniformity at selected test cases covering ranges of flow conditions, brick types, and inlet conditions.

A series of tests has been completed in which suckdown and fountain forces and pressures were measured on circular plates and twin-tandem-jet generic STOVL (short takeoff and vertical landing) configurations. The tests were conducted using a small-scale hover rig, for jet pressure ratios up to 6 and jet temperatures up to 700°F. The measured suckdown force on a circular plate with a central jet was greater than that found with a commonly used empirical prediction method. The present data showed better agreement with other sets of data. The tests of the generic STOVL configurations were conducted to provide force and pressure data with a parametric variation of parameters so that an empirical prediction method could be developed. The effects of jet pressure ratio and temperature were found to be small. Lift improvement devices were shown to substantially reduce the net suckdown forces. Paper to be presented at SAE Aerospace Meeting, Dayton, Ohio, April 24-27, 1990

A fundamental thermodynamic model of the complete spark-ignited, homogeneous charge engine cycle has been used in several parametric analyses to predict the effects of engine design and operating alternatives on fuel consumption and emissions of NOx and unburned hydrocarbons (HC). The simulation includes sub-models for wall heat transfer, NOx and HC emissions, and the engine breathing processes. This work demonstrates the power and utility of a comprehensive engine simulation by presenting several independent parametric studies that were carried out in response to genuine engine design and/or operating strategy questions. Included in this compilation are the effects of cycle heat loss, exhaust port heat loss, combustion duration, and charge dilution (EGR and/or lean air-fuel ratio). In addition, the influence of the design variables associated with bore-stroke ratio, intake and exhaust valve lift, and cam timing are considered.

Propulsion system sizing for mechanical flap and externally blown flap aircraft is demonstrated. Included in this study is the effect of various levels of noise suppression on the aircraft final design characteristics. Both aircraft are sized to operate from a 3000 ft runway and perform the same mission. For each aircraft concept, propulsion system sizing is demonstrated for two different engine cycles-one having a fan pressure ratio of 1.5 and a bypass ratio of 9 and the other having a fan pressure ratio of 1.25 and a bypass ratio of 17.8. The results presented include the required thrust to weight ratio, wing loading, resulting gross weight and direct operating costs as functions of the engine noise level for each combination of engine cycle and aircraft concept.