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Technical Paper

A Computer Model for Thermofluid Analysis of Engine Warm-up Process

1993-04-01
931157
A general purpose computer model has been developed for analyzing the thermal performance of thermofluid systems. The system thermal behaviour is governed by heat convection and conduction. The model represents a thermofluid system as a thermal network, consisting of several different fluid circuits which are separated by solid walls. The solid walls are represented by hexahedral elements with lumped heat capacitance. The model has the capability to set up and link an equivalent thermal network from input data, using two types of junctions: wall-to-wall and fluid-to-wall. The flow calculations are based on the one-dimensional incompressible flow equation and the heat transfer calculations are based on either forced or natural heat convection for internal and external flows. The heat convection formulae used in the model are in the non-dimensional form which simplifies the program structure.
Technical Paper

Concurrent Control of Multiple Calorimetry Facilities Using a Single-Tasking Computer

1993-04-01
931150
Thermal testing of vehicle heat exchangers used to be (and in some cases still is) a matter of manually adjusting fluid conditions to the device under test, waiting for stability and writing to a clip board measured physical values. Heat rejection figures were then calculated based on the temperature change of one fluid and results were often plotted on squared paper as they were derived. The validity of each test point was assessed by the Test Engineer on the basis of his/her experience, expectation and fit on the curve, bad points being repeated at once. The contemporary need to value-engineer products together with the advent of low cost computing power has influenced these practices.
Technical Paper

A Model for the Investigation of Temperature, Heat Flow and Friction Characteristics During Engine Warm-Up

1993-04-01
931153
A computational model has been developed to support investigations of temperature, heat flow and friction characteristics, particularly in connection with warm-up behaviour. A lumped capacity model of the engine block and head, empirically derived correlations for local heat transfer and friction losses, and oil and coolant circuit descriptions form the core of the model. Validation of the model and illustrative results are reported.
Technical Paper

An Automobile Air Conditioning Design Model

1993-04-01
931137
A computer program has been developed to predict the steady-state performance of vapor compression automobile air conditioners and heat pumps. The code is based on the residential heat pump model developed at the Oak Ridge National Laboratory (ORNL). Most calculations are based on fundamental physical principles, in conjunction with generalized correlations available in the research literature. Automobile air conditioning components that can be specified as input to the program include open and hermetic compressors; finned tube condensers; finned tube and plate-fin style evaporators; thermostatic expansion valves (TXV), capillary tube, and short tube expansion devices; refrigerant mass; and evaporator pressure regulator and all interconnecting tubing. Pressure drop, heat transfer rates, and latent capacity ratio for the new plate-fin evaporator submodel are shown to agree well with laboratory data. The program can be used with a variety of refrigerants, including R-134a.
Technical Paper

Use of Infra-Red Thermography for Automotive Climate Control Analysis

1993-04-01
931136
In this paper, several automotive climate control applications for IR thermography are described. Some of these applications can be performed using conventional IR techniques. Others, such as visualizing the air temperature distribution within the cabin, at duct exits, and at heater and evaporator faces, require new experimental methods. In order to capture the temperature distribution within an airstream, a 0.25-mm-thick (0.01 inch) fiberglass screen is used. This screen can be positioned perpendicular or parallel to the flow to obtain three-dimensional spatial measurements. In many cases, the air flow pattern can be inferred from the resulting temperature distribution, allowing improved air distribution designs. In all cases, significant improvement in the speed, ease, and quantity of temperature distribution information can be realized with thermography as compared to conventional thermocouple array techniques.
Technical Paper

Determination of the Heat Transfer Performance of Finned Surfaces Using a Transient Lumped-Capacity Method

1993-04-01
931134
This paper presents an analysis and critical appraisal of a ‘lumped-capacity’ method for the determination of the average air-side heat transfer coefficient of a finned-tube heat exchanger geometry. A simple transient heat transfer experiment is described in which a small finned heat exchanger sample was tested in a wind tunnel. The heat exchanger sample consisted of three rows of staggered flat copper rods within an array of continuous fins of the same material. Analysis and supporting experimental results, demonstrate the validity of an assumed pseudo-constant fin efficiency thereby justifying the employment of a modified lumped-capacity approach for finned geometries.
Technical Paper

Heat Transfer Augmentation of Mechanically Assembled Heat Exchanger by Internally Finned Tubes

1993-04-01
931135
Mechanically Assembled Heat Exchangers (MAHE) find wide applications in Automotive field, specially for Air Conditioning and Engine Cooling Systems. To improve the performance of MAHE with round tubes, new types of tubes with straight internal fins have been designed and realized, along with a new expansion tooling which allows to expand these types of tubes without destroying the internal fins. The purpose of this paper is to present a MAHE, developed for automotive use, with aluminum round tube internally finned, the technique of assembling tube-fin, the effects of the finned tube on the performances and its possible applications.
Technical Paper

Standardized Method for Vibration Testing of Engine Cooling Systems

1993-04-01
931142
The purpose of this paper is to demonstrate practical applications of a standardized method for vibration testing of vehicle engine cooling modules and components based on the developed data collection scheme, the test data calibration and editing. In addition, some examples of collected road data analysis and simulated test creation will be discussed. Moving vehicle vibrations are an important part of the dynamic environment of an engine cooling module which affects system durability. Several methods of vibration testing and real road condition simulation were developed to evaluate the cooling module durability and to assure the system long life in customer hands. The goal of simulated vibration testing is to recreate the dynamic load on the system which the vehicle ECM might see in real road conditions and which could produce cooling module failures during the vehicle life cycle.
Technical Paper

Use of Infrared Imaging Technology in Heat Exchanger Development and Evaluation

1993-04-01
931144
Since it's inception, infrared (IR) imaging technology has demonstrated nearly limitless applications in situations where surface temperature data are required. IR imaging systems offer numerous advantages over conventional surface temperature measurement techniques at the expense of a relatively large financial investment. Nevertheless, IR imaging systems are valuable engineering tools and are well suited for use in the development and evaluation of vehicular heat exchangers. The purpose of this paper is to provide background and fundamental information on IR imaging technology and to discuss it's application to heat exchanger development. Finally, several basic application examples on the use of IR imaging technology in heat exchanger development will be presented.
Technical Paper

A New Method for Monitoring Thermal Energy Utilisation of Vehicle Engines

1993-04-01
931140
Proposals for a new method for measuring the fuel efficiency of engines in situ in vehicles are based on a new electronic instrument, the Ergometer, which measures the cumulative work energy delivered by an engine over a complex journey. Engine thermal efficiency varies widely with load, speed, steady and transient operations. Measurement of EJATE, or Elapsed Journey Average Thermal Efficiency, derived from work and fuel measurements, gives clearer information on the state of development of a given vehicle's power train to meet economical driving conditions. Such information is considerably more revealing than conventional vehicle fuel consumption measurements. The Ergometer can be fitted to individual vehicles, or to engine test beds. Most attractively it can be fitted to rolling road dynamometers where the EJATE of any vehicle can be easily measured.
Technical Paper

Quality Assurance for Combustion Chamber Thermal Boundary Conditions - A Combined Experimental and Analytical Approach

1993-04-01
931139
The increasing cost of prototype engine design and development has placed new emphasis on the importance of accurate analysis of combustion chamber components. A method to assess and improve the quality of thermal boundary conditions is described. The integration of analytical approaches and experimental techniques to validate and improve thermal boundary conditions is dependent on continuous improvement of theoretical models and correlation with measured results. To monitor and improve quality, it is important to operate a closed loop of prediction, measurement and feedback to the analysis system. The development of advanced computational methods, particularly the Finite Element Method (FEM) has increased the opportunities to include detailed component thermal analysis in combustion chamber design studies. In using FEM, much emphasis is traditionally placed on “accurate” mesh generation in order to minimise element distortion and optimise element polynomial order.
Technical Paper

FIND: Framework for Intelligent Design

1993-04-01
931180
A novel framework for intelligent design of engine systems is introduced. Existing models of engine components and processes are integrated into a multi-purpose, flexible configuration framework. Fundamental thermodynamic elements, including zero-dimensional control volumes, one-dimensional pulsating fluid lines, and continuous flow machines are identified as the constituting components of engine systems. Models of the behavior of these elements, with various degrees of thermodynamic resolution, have been implemented into the framework. The task of the engine designer is, thus, reduced into selecting appropriate thermodynamic elements to model his engine system based on his design objectives. The applicability of the present framework to a wide range of simulation problems is demonstrated.
Technical Paper

Modeling of the Complete Vehicle Powertrain Using ENTERPRISE

1993-04-01
931179
ENTERPRISE is a computer simulation tool to model both the thermodynamic processes in the engine and the mechanical components of the powertrain. It can model the effects of turbocharger selection, timing control, air-fuel ratio control, torque converter characteristics, gear ratio, rotating inertias, vehicle weight, hydraulic demands, etc. on a vehicle over a desired course or load cycle. There is good agreement between the model and vehicle data. Enterprise has been used to design engines and powertrains to improve response and reduce driveline failures.
Technical Paper

Propylene Glycol Coolant: A Safer Alternative for Heavy Duty Vehicles

1993-04-01
931166
Propylene Glycol (PG) and ethylene glycol (EG) are similar in physical properties and therefore both are good base materials for coolant/antifreeze for heavy duty diesel engines. Propylene glycol and ethylene glycol are different chemically and have much different toxicological profiles. These differences result in the two products having greatly different safety characteristics which affect product labelling, use, and disposal. The differences in regulation for these two types of engine coolants as well as the comparisons of performance in heavy duty fleet on-highway service will be addressed. Results of bench-scale and fleet testing will be shown.
Technical Paper

Toward Quieter Cooling Systems for Earthmoving Machines

1993-04-01
931165
Customer and regulatory forces are demanding quieter earthmoving and construction machines in many market segments -- a trend which is expected to intensify in the decade of the 90's. In many cases, the cooling system is a major contributor to the spectator sound power. Therefore, cost-effective means are required for reducing cooling system noise emissions. This paper reviews strategies for cooling system noise reduction of earthmoving machines. Sources of cooling system noise and general noise reduction principles are outlined. Then, the impact of specific design countermeasures are discussed, including system size, ambient capability, heat loads, air system restriction, quieter components, and noise cover-up. Use of nondimensional parameters for fan selection are discussed. Finally, future design trends and areas for further investigation are identified.
Technical Paper

Optimization of Inlet Port Design in a Uniflow-Scavenged Engine Using a 3-D Turbulent Flow Code

1993-04-01
931181
The finite volume, three-dimensional, turbulent flow code ARIS-3D is applied to the study of the complex flow field through the inlet port and within the cylinder of a uniflow-scavenged engine. The multiblock domain decomposition technique is used to accommodate this complex geometry. In this technique, the domain is decomposed into two blocks, one block being the cylinder and the other being the inlet duct. The effects of inlet duct length, geometric port swirl angle, and number of ports on swirl generating capability are explored. Trade-offs between swirl level and inherent pressure drop can thus be identified, and inlet port design can be optimized.
Technical Paper

Development of a Miniaturized, Dilution-Based Diesel Engine Particulate Sampling System for Gravimetric Measurement of Particulates

1993-04-01
931190
Abstract: Diesel engine particulate certification, heretofore limited to on-highway truck engines, will be expanded in scope beginning in 1996 to eventually include all diesel engines. Legislation in Europe, Japan and California will extend certification efforts to engines powering generator sets, construction/agricultural vehicles, locomotive and marine engines, using “steady-state” test guidelines proposed in ISO 8178, Parts 1 - 7. “Mini-dilution” tunnels have been the European and Japanese systems of choice for dilute particulate emissions certification for non-U.S. truck diesel engines. However, repeatability, steady-state test correlation vs. full dilution systems, portability, sampling time, size and system cost have precluded universal industry and regulatory acceptance of existing “mini-system” designs. To address corporate particulate measurement needs, Caterpillar Inc. developed a device known internally as a “Micro-Dilution Particulate Measurement System”.
Technical Paper

Nucleate Boiling Engine Cooling System - Vehicle Study

1993-04-01
931132
A fundamental vehicle study for a new engine cooling system, the so called NUCLEATE BOILING ENGINE COOLING SYSTEM, has been tested under real and critical conditions in a climate controlled wind-tunnel. Using this cooling system requires a profound knowledge of the cooling circuit and all cooling components such as: condenser, waterpump, liquid/vapor-separator, expansion tank, fan control unit. After preliminary experimental and theoretical studies, two types of cooling circuits were realized and tested in a car: Completely filled nucleate boiling cooling system Partially filled nucleate boiling cooling system Both types of circuits were sealed systems. This meant there was no evaporation or loss of liquid into the environment. By using the nucleate boiling cooling system, the heat of the cylinder head was dissipated while the boiling process change of liquid phase to vapor at constant boiling temperature.
Technical Paper

Combustion and Performance Characteristics of a Low Heat Rejection Engine

1993-03-01
930988
The purpose of this paper is to investigate combustion and performance characteristics for an advanced class of diesel engines which support future Army ground propulsion requirements of improved thermal efficiency, reduced system size and weight, and enhanced mobility. Advanced ground vehicle engine research represents a critical building block for future Army vehicles. Unique technology driven engines are essential to the development of compact, high-power density ground propulsion systems. Through an in-house analysis of technical opportunities in the vehicle ground propulsion area, a number of dramatic payoffs have been identified as being achievable. These payoffs require significant advances in various areas such as: optimized combustion, heat release phasing, and fluid flow/fuel spray interaction. These areas have been analyzed in a fundamental manner relative to conventional and low heat rejection “adiabatic” engines.
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