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Technical Paper

Simulors, An Innovative Tool for Molds Development

1996-04-01
91A117
Mold designers and foundrymen spend a lot of time in developing molds without knowing exactly the phenomena which take place inside. Simulor, which has been used in an industrial environment for two years, offers the solution to make foundrymen understand what happens during the filling of the mold and the solidification of the part. Based on navier-stokes and heat transfer equations, simulor provides speed distribution and metal front evolution in the cavity and thermal map in the mold and the part. Some examples with different metals (cast iron, aluminum alloy) cast with various processes (sand or die casting, low pressure or gravity casting) will be given. This new tool will given foundrymen the opportunity to test the mold before having it machined and will also allow reduction in development delays.
Technical Paper

A Multidimensional Model Prediction of Heat Transfer in Non-Fired Engines

1986-03-01
860467
An axisymmetric three-dimensional model for in-cylinder processes has been applied to the predictions of wall heat transfer in a non-fired engine cylinder. Computed heat fluxes are shown for combustion chambers with a flat piston and a deep-bowl piston for swirl and no-swirl cases. The predictions compare well with existing experimental heat fluxes at several different radii on a cylinder head except in a central part. It is also shown that the predictions of surface-averaged heat flux are consistent with those obtained from empirical correlations. The effect of compression-expansion work is indicated by predicted temperature profiles and typically demonstrated by phase difference between the heat flux and the bulk-mean gas temperature. Computational discussions are given on local heat fluxes in the deep-bowl-piston combustion chamber and suggest that local heat fluxes are greatly increased by squish motion, squish-induced vortex, and swirling motion spun-up in the bowl.
Technical Paper

Silicate Gelation in Heavy-Duty Diesel Engine Cooling Systems

1985-12-01
852327
Silica gel formation in heavy duty diesel cooling systems has increased with the increased usage of antifreeze with high levels of silicate. Gelation can occur when this type of antifreeze is mixed with supplemental coolant additives which are required to protect heavy duty diesel engine cooling systems, or when the undiluted antifreeze is stored for long periods. Gel in the cooling system can decrease coolant flow and heat transfer causing engine overheating. Gel formation is shown to be a chemical problem, not a problem of newer engine and cooling system design. Recommendations for avoiding the problem are included.
Technical Paper

An Overview of the DOE Advanced Automotive Gas Turbine Program

1985-04-01
851189
In order to determine a viable alternative to the contemporary gasoline engine the Federal Government has sponsored and continues to conduct extensive R&D under contractual arrangements on an Advanced Automotive Gas Turbine Engine. Ceramic materials have been introduced as components of the high temperature regions of the engine so as to increase the thermodynamic and hence the overall efficiency of the gas turbine engine.
Technical Paper

A Heat Pipe Quick Disconnect

1985-07-01
851323
This paper reports the proof of concept demonstration of a heat pipe quick disconnect being developed for the space constructible radiator system. The disconnect provides a maintainable coupling between the heat pipe evaporator, which is brazed to a mating heat exchanger, and the replaceable condenser section of a monogroove heat pipe radiator element. Test results, with pressurized nitrogen gas, confirm low leakage rates in both demated and mated configurations. Comparative thermal tests in a working 3 m (10 ft) test bed heat pipe using ammonia fluid revealed a 30% decrease in heat transport due to the additional minor pressure losses from the quick disconnect. The bulk of this loss is attributed to the transition section that joins the two adjacent heat pipe flow channels to the separated liquid and vapor passages within the disconnect coupling. It would be possible to decrease this overall loss in heat transport to under 10% with a redesigned transition section.
Technical Paper

Heat Pipe Cooled Electronic Circuit Card as Applied to SEM FORMAT B Standard

1985-07-01
851317
Grumman developed, patented, and tested a heat pipe concept to increase the power dissipation capability of the SEM FORMAT B Standard Module. The systems integration concept approach in the development of the design was to: Provide a heat pipe module within the existing SEM FORMAT B form factor that would be interchangeable with the existing conduction module Utilize the short conduction path of the module Maintain the existing component mounting area Maintain thermal compatibility between the module and heat sink interface. Within the restraints of these objectives, the Grumman concept was shown to be feasible and proven to be capable of providing a power dissipation capability twice that of the existing conduction module.
Technical Paper

Development, Fabrication and Application of a Primary Surface Gas Turbine Recuperator

1985-06-01
851254
Design and manufacturing technology for primary surface gas turbine recuperators has been under development at Caterpillar Tractor Co. for the past 16 years. The key element in the success of this program has been the development of an optimal heat transfer surface which was amenable to low cost fabrication techniques. This paper describes the design and application criteria which guided the development of the primary surface gas turbine recuperator, including heat transfer and pressure drop characteristics, mechanical and thermal loading mechanisms, design life, and materials selection. A review of the recuperator's development history is presented, from early rig tests on handmade heat exchangers to the present commercial fleet of recuperators which were produced in a highly automated manufacturing facility and have compiled over 240,000 total hours of operation as of 02/01/85.
Technical Paper

A Time-Dependent Spatial Model for Radiant Heat Transfer in Diesel Engines

1983-10-31
831725
We have developed a fully three-dimensional spatial model of the instantaneous radiation heat transfer in direct ignition diesel engines. The model is based on the assumption that the primary source of radiation is from the soot formed on the fuel-rich side of the combusting spray plumes. The model then calculates view-factors to the various regions from the evolving plume using a spray correlation model. The soot is assumed to be a grey body radiating through an optically thin medium to the relatively cool components of the combustion chamber. Preliminary calculations using the model indicate that there are significant spatial and temporal variations in the incident radiation on various regions in the combustion chamber. These calculations were performed for a geometry and operating conditions of a production turbocharged medium speed engine at full load conditions.
Technical Paper

Prediction of Contained Air Temperature from SAE Standard Rolling Resistance Test Data

1983-11-07
831796
Truck tire rolling resistance, when determined through the SAE J 1379 test matrix, can be shown to predict cavity air temperature at test equilibrium. Cavity temperatures are determined with the SAE Standard test data, heat transfer relationships, and equations of state. When this method is compared to road test data, the SAE J 1379 test procedure is shown to be more precise, equally accurate, and many times faster to perform than the same test conducted on the road.
Technical Paper

A One Thousand Car Assessment of the U.S. Car Population Cooling Systems

1983-12-05
831821
For the first time a statistically valid survey and sampling of the engine coolant has been taken of the United States passenger car population covering model years 1980 through 1968 and older. The purpose of the survey was to assess the coolant inhibitor condition, glycol concentration, coolant level, and performance history in passenger cars as they prevail in all parts of the United States. A circulated warm coolant sample was taken from 1004 engine cooling systems. The samples were evaluated for rust and/or sediment, and analyzed for pH, reserve alkalinity, percent glycol, and iron concentration. The car operator was interviewed for a history of coolant maintenance and engine cooling performance problems. The information from this unique survey clearly indicates the current quality of engine coolant condition and how it relates to the major geographic segments of the country.
Technical Paper

Hot Film Type Fuel Flow Sensor

1984-02-01
840135
A NEW TYPE FUEL FLOW SENSOR which is based upon heat transfer principle has been developed for automotive applications. The fuel flow sensor presented in this paper utilizes temperature sensitive resistors made of extremely thin platinum films, and is located in the main passage of a conduit opposite to a nozzle. An extraordinarily wide dynamic range and a quick response have been obtained in comparison with conventional methods. The hot film type fuel flow sensor could allow a new microprocessor to control the engine functions, as well as a fuel consumption or a fuel rate meter.
Technical Paper

Measurements of Air Flow Velocity Distributions Inside a Rolling Pneumatic Tire

1984-02-01
840066
The research reported on here is concerned with the subject of air flow and temperature buildup in a pneumatic tire. Its ultimate objectives are to understand the basic mechanisms by which energy delivered to the tire is converted to heat, and to quantify the contribution to rolling resistance that is made by this energy-conversion path. Direct measurement of the heat-transfer rate is very difficult, because the tire surface undergoes such large deformations. The approach being taken here is to make measurements of the velocity distributions, and to relate these to the heat-transfer rate by numerical modeling of the flow field. This paper contains experimental results for the velocity distributions. The numerical modeling effort is not yet complete; however, a crude estimate of the heat-transfer rate can be made on the basis of the measured mass flow rates.
Technical Paper

Computation of Radiation Heat Transfer in Diesel Combustion

1983-09-12
831332
A theoretical model of radiation heat transfer has been developed. A computation of radiation heat flux at a particular location in the combustion chamber by using the present model requires in-cylinder time- and space-resolved species data and cylinder pressure. From the species data, the burned fuel/air ratio distribution is inferred to compute space-resolved adiabatic flame temperature. For the computation of the spectral emissivity of an isothermal volume of adiabatic temperature containing soot, the Rayleigh-limit expression is used. The refraction indices in the expression are obtained by using the dispersion equations based on the electronic theory encompassing both free and bound electrons. For the spectral emissivity from the gaseous component in the volume, the semi-empirical band model is used.
Technical Paper

Finite Element Modeling Programs for a Two Dimensional CAD Package

1983-09-12
831364
Eight 2-D finite element program modules are integrated into an effective analysis tool for improving the productivity in the design cycle. Three preprocessing modules can generate a finite element mesh, display the mesh, and file the finite element model into an inventory of models. Two-dimensional stress analysis, heat transfer analysis, and torsion analysis of the part can be performed. Deformed geometry and contour plots can be used to summarize the analysis results. The usefulness of this integrated approach and the cost effectiveness are illustrated by three examples.
Technical Paper

Solid Amine CO2 Removal System for Submarine Application

1983-07-11
831131
Maintaining the ambient CO2 partial pressure as low as practical within available space and power limitations is desirable for the extended submerged operations of modern nuclear submarines. Existing liquid amine systems are designed to control CO2 partial pressure to a minimum of 0.5 percent. Advanced technology utilizing commercially available solid amine resin is being developed for an improved CO2 removal system capable of 0.2% CO2 partial pressure. The solid amine is regenerated by heating it with atmospheric pressure steam. Amine bed dynamics during the regeneration process allow the CO2 to be highly concentrated. The major components in this system's conceptual design include four beds of solid amine resin, a process air fan, a steam generator for amine regeneration, a condensing heat exchanger, and a CO2 compressor. A sequencing controller provides continuous system operation by cycling the solid amine beds between CO2 absorption and regeneration.
Technical Paper

Electronic Cooling Design and Test Validation

1983-07-11
831119
An electronic cooling design and test approach utilizing a counter flow air-cooled heat exchanger is presented. The design is particularly applicable to military (i.e., Navy) weapon systems where extended reliability in harsh thermal and dynamic environments and simplicity of design are of paramount importance. Analytical modeling techniques were utilized to perform design tradeoffs, define heat exchanger air flow rates and predict steady-state semiconductor operating temperatures for worst-case duty cycles and ambient conditions. Environmental testing was conducted on an instrumented development unit to prove-out the cooling design and validate high reliability performance. This paper encompasses the cooling system selection and design and the environmental test results. Heat exchanger performance ratings as well as measured component temperatures are presented.
Technical Paper

A Contact Conductance Interface for a Space Constructable Heat Pipe Radiator

1983-07-11
831101
A connectable/disconectable thermal interface has been developed for the constructable radiator system under development at NASA-Johnson Space Center. A contact heat exchanger approach which involves pressurized clamping of a segmented cylindrical heat exchanger on the outside of a round heat pipe evaporator section was designed, fabricated, and tested. Dry metal-to-metal contact conductance heat transfer is utilized. Test results have indicated excellent contact conductances of up to 8500 w/m2°c (1500 Btu/ft2°F) at 2000 kPa (300 psi) clamping force. The feasibility and fabricability of the design have been demonstrated.
Technical Paper

Thermal Management System Technology Development for Space Station Applications

1983-07-11
831097
Advanced planning within NASA is currently being focused on a manned Space Station as the next major step in the U.S. space program. Capabilities such as evolutionary growth on-orbit, indefinite life through maintenance, and flexibility to accommodate a time-varying complement of users constitute requirements for the Space Station thermal management system that are radically different from those of previous or current missions. Anticipating the need to identify the technology required for long-life, high-power orbital platforms/stations, NASA began a multicenter thermal management system technology development program in 1979. This program, sponsored by the Office of Aeronautics and Space Technology, has continued to evolve in parallel with the increasingly detailed planning for a Space Station program.
Technical Paper

Cylinder Head Gasketing Problems in Bi-Metallic Engines

1984-02-01
840189
There has been and continues to be a growing trend in world engines towards the use of ‘Bi-Metallic’ constructions, ie. engines which feature head and block castings of different materials. The use of aluminium cylinder heads with cast iron cylinder blocks is a typical arrangement. Figure 1 indicates some of the significant differences in the physical properties of cast iron and aluminium. As can be seen, aluminium offers a number of advantages from an engine design viewpoint, notably weight saving and heat transfer efficiency. The use of aluminium can, however, result in a number of potential difficulties in terms of its effect on cylinder head gasket performance. This paper considers these difficulties with particular reference to ‘fluid sealing’.
Technical Paper

Assessment of the Ability of a Multidimensional Computer Code to Model Combustion in a Homogeneous-Charge Engine

1984-02-01
840230
Computations were performed Co evaluate and, if necessary, improve a combustion submodel and to assess the current ability of the multidimensional code to model combustion, wall heat transfer and nitric oxide emissions in the homogeneous-charge spark-ignition engine. As opposed to a conventional one-step global combustion rate expression, a modified form gave a better match with measurements. This modified expression required case-to-case tuning when the volumetric efficiency or fuel-air equivalence ratio changed. However, the pre-exponential factor required for such tuning correlated with residual fraction and equivalence ratio. Computed wall heat-transfer and emission results compared well with measurements.
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