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Technical Paper

Sound Metric Balance of Engine Cooling Fan Noise to enable Delivery of Good Exterior Sound Quality

2011-05-17
2011-01-1530
The drive for lower CO₂ emissions places ever greater demand on cooling dissipation for a multi-cylinder internal combustion engine. This challenge has increased the requirements of the engine cooling system, particularly in countries where high ambient temperatures prevail and HVAC usage is high. Environmental necessity coupled with market demands have resulted in cars which emit a higher level of cooling fan noise which is intrusive in an urban environment and objectionable to customers. Conventional quantification of noise using traditional units and metrics was found to be insufficient for effective Sound Quality analysis. To assist Bentley Motors, a high performance luxury vehicle manufacturer, with its brand cachet and its commitment to the environment and customer, a new sound metric analysis has been devised to help the business deliver an ever-quieter exterior power unit cooling system.
Technical Paper

Halogen Free Synthetic Elastomer Blend to Meet Properties of Fuel Hose Outer Cover (Return Line) Application

2011-09-13
2011-01-2233
Diesel engine fuel hose return line is considered as a low pressure line and consists of two layers. The inner layer is used to carry the excess fuel, thereby hose material shall have resistance to fuel and its residues. The outer layer is used to protect inner layer from heat, ozone and oil spillage, thereby outer cover material shall have resistance against the heat, ozone and engine oil. Currently NBR PVC, NBR and FKM materials have been used as inner layer materials in diesel engine fuel hose outer cover application, according to service temperature. Halogen contained CSM material has been used for outer cover application and the production of CSM material was withdrawn by one of the major manufacturer recently. Current global challenge is to use environment friendly material in vehicle components to make hazardous free environment. To replace CSM material, which contains Halogen, the available options are CPE, CR, HNBR and AEM materials.
Technical Paper

Straight vegetable Oil Run Diesel Engine - A Compromise Solution

2009-12-13
2009-28-0033
The fuel crises of the 1970's and early 1980's focused attention on the desirability of developing alternative fuels and decreasing the dependency on petroleum-based fuels. Vegetable oils and derivatives are among the materials that were extensively investigated as alternative diesel fuels. Vegetable oils are a potential alternative to the partial or total substitution of diesel fuels. It was known that short-term engine tests have been successful with vegetable oils; however, long-term tests have revealed the fuel limitations regarding lubricating oil contamination, deposits on engine surfaces and performance problems. This study shows how the added advantages of air-cooled engine over the water-cooled engine become the preferred choice for the SVO run diesel engine. Based on the 100 hrs SVO run diesel engine, the modification has been carried out for the long run. Different emission measurements were carried out and studied in comparison with conventional diesel.
Technical Paper

Coolant Pipe Press Fit Study

2011-04-12
2011-01-0421
Coolant pipes are a prime connection units present in any engines that facilitates the flow of coolant and thereby keeping the engine under its optimum operating condition. Among the several influencing factors that deteriorate engines performance, the coolant leak is also one of the contributors. This could be caused primly due to leakage issues that arises from the pipe press fit zones. Henceforth it is very important to understand the root cause of this press-fit connection failure. The present study deals with press-fit between the pipe and housing in an engine which is subjected to extreme thermal loads (min of -40°C to a max temperature of +150°C) thereby causing the press-fit loosening effect.
Technical Paper

Axial Fan Performance Predictions in CFD, Comparison of MRF and Sliding Mesh with Experiments

2011-04-12
2011-01-0652
Underhood Thermal Management has become an important topic for the majority of automotive OEM's. To keep combustion engines cool and manage waste heat efficiently is an important part in the design of vehicles with low fuel consumption. To be able to predict cooling performance and underhood airflow with good precision within a virtual design process, it is of utmost importance to model and simulate the cooling fan efficiently and accurately, and this has turned out to be challenging. Simulating the cooling fan in a vehicle installation involves capturing complex fluid dynamic interaction between rotating blades and stationary objects in the vicinity of the fan. This interaction is a function of fan rotation rate, fan blade profile, upstream and downstream installation components. The flow is usually highly turbulent and small geometry details, like the distance between the blade tip and the fan shroud, have strong impact on the fan performance characteristics.
Journal Article

Nonuniform Heat Source Model for a Lithium-Ion Battery at Various Operating Conditions

2011-04-12
2011-01-0654
As battery temperature greatly affects performance, safety, and life of Li-ion batteries in plug-in and electric vehicles under various driving conditions, automakers and battery suppliers are paying increased attention to thermal management for Li-ion batteries in order to reduce the high temperature excursions that could decrease the life and reduce safety of Li-Ion batteries. Currently, the lack of fundamental understanding of the heat generation mechanism due to complex electrochemical phenomena prohibits accurate estimation of the heat generation within Li-ion cells under various operating conditions. Heat from Li-ion batteries can be generated from resistive dissipation, the entropy of the cell reaction, heat of mixing, and other side chemical reactions. Each of these can be a significant source of heat under a range of circumstances.
Technical Paper

Prediction of Transient Engine Compartment Temperature During After-Boil

2011-04-12
2011-01-0657
The performance of ground vehicles of all types is influenced by the cooling and ventilation of the engine compartment. An increased heat load into the engine compartment occurs after engine shut down. Heat is transferred from the hot components within the engine compartment by natural convection to the surrounding air and by radiation to the adjacent surfaces. The heat is then dissipated to the ambient mostly by convection from the exterior surfaces. The objective of this study is to develop a Computational Fluid Dynamics (CFD) simulation methodology to predict the airflow velocity and temperature distributions within the engine compartment, as well as the surface temperature of critical engine components during the after-boil condition. This study was conducted using a full-scale, simplified engine compartment of an armored combat vehicle. Steady-state simulation was performed first to predict the condition prior to engine shut down.
Technical Paper

Study of Influence of MRF Method on the Prediction of the Engine Cooling Fan Performance

2011-04-12
2011-01-0648
MRF method is commonly used for predicting cooling performance to design vehicle engine cooling systems. Especially, the practical prediction of the cooling fan performance is one of the important issues. In the design phase of the vehicle development, combinations of multiple parameters are generally examined. Therefore, the steady RANS coupled with MRF method is indispensable. However, unfortunately, the current method does not always give enough accuracy to practical vehicle design. Thus, this paper describes that the method to determine adequate MRF-region to predict the fan performance in practical accuracy.
Technical Paper

Road Map and Technology Trends for Vehicle Engine Cooling Fan Speed Control

2011-04-12
2011-01-1334
This paper describes the rationale for the technology selection and speed control methods for electric cooling fans used for typical automotive applications, including most passenger cars and even some light duty truck s. Previous selection criteria were based primarily around cost, simplicity of implementation and reliability. However, the more recent focus toward fuel economy and optimization of energy consumption at a vehicle level has given a greater priority to the minimization of electrical power draw. Specifically, that need is addressed through both efficiency of the electric motor at any operating condition as well as providing a control method that delivers only the minimum electrical power to meet engine cooling and air conditioning requirements. This paper will explore the various control methods available, their relative merits and shortcomings and how they influence both FTP and real world fuel economy.
Journal Article

Variable and Fixed Airflow for Vehicle Cooling

2011-04-12
2011-01-1340
This paper describes rationale for determining the apportionment of variable or ‘shuttered’ airflow and non-variable or static airflow through openings in the front of a vehicle as needed for vehicle cooling. Variable airflow can be achieved by means of a shutter system, which throttles airflow through the front end and into the Condenser, Radiator, and Fan Module, (CRFM). Shutters originated early in the history of the auto industry and acted as a thermostat [1]. They controlled airflow as opposed to coolant flow through the radiator. Two benefits that are realized today are aerodynamic and thermal gains, achieved by restricting unneeded cooling airflow. Other benefits exist and justify the use of shutters; however, there are also difficulties in both execution and practical use. This paper will focus on optimizing system performance and execution in terms of the two benefits of reduced aerodynamic drag and reduced mechanical drag through thermal control.
Journal Article

An Innovative Modeling Approach to Thermal Management using Variable Fidelity Flow Network Models Imbedded in a 3D Analysis

2011-04-12
2011-01-1048
Speed and accuracy are the critical needs in software for the modeling and simulation of vehicle cooling systems. Currently, there are two approaches used in commercially available thermal analysis software packages: 1) detailed modeling using complex and sophisticated three-dimensional (3D) heat transfer and computational fluid dynamics, and 2) rough modeling using one-dimensional (1D) simplistic network solvers (flow and thermal) for quick prediction of flow and thermal fields. The first approach offers accuracy at the cost of speed, while the second approach provides the simulation speed, sacrificing accuracy and can possibly lead to oversimplification. Therefore, the analyst is often forced to make a choice between the two approaches, or find a way to link or couple the two methods. The linking between one-dimensional and three-dimensional models using separate software packages has been attempted and successfully accomplished for a number of years.
Technical Paper

Compressor Body Temperature and Lubrication

2013-04-08
2013-01-1501
The paper addresses compressor body temperature (crankcase) importance to the vehicle AC system long-term durability. Majority of OEM vehicle test evaluation is to see if AC system can pass compressor discharge temperature and discharge pressure targets. Most OEMs adopt 130°C max compressor discharge temperature and 2350 kpag head pressure as the target. From the field, although some of the compressor failure results from a high compression ratio, and compressor discharge temperature that are caused by the poor front end airflow, etc., high percentage compressor failed systems exhibit not too high compression ratio and compressor discharge temperature, but having the trace of high temperature in the shaft area, gasket area, etc. With introducing more and more variable swash plate compressor applications, OEMs start to see more and more compressor failures that are not related to a high compressor discharge temperature but the trace of high compressor body temperature.
Journal Article

Refrigerant and Lubricant Distribution in MAC System

2013-04-08
2013-01-1496
This paper presents experimental results for refrigerant and lubricant mass distribution in a typical automotive A/C (MAC) system. Experiments were conducted by closing valves located at the inlet and outlet of each component after reaching steady state, isolating the refrigerant and lubricant in each component. Refrigerant mass is recovered in a separate vessel using liquid nitrogen to reduce refrigerant vapor pressure to near vacuum. The overall weight is determined within ±1% after the separation of refrigerant and lubricant. The mass of lubricant is determined by using three different techniques: Remove and Weigh, Mix and Sample, and Flushing. The total mass of lubricant in the system is determined with ±2.5% uncertainty on average. R134a and R1234yf are used with PAG 46 oil as working fluid at different Oil Circulation Ratio (OCR), ranging from 2% to 4%. Experiments are conducted in two standard testing conditions: I35 and L35 (SAE Standard J2765).
Technical Paper

Development of Free Piston Engine Linear Generator System Part 1 - Investigation of Fundamental Characteristics

2014-04-01
2014-01-1203
Abstract Free Piston Engine Linear Generator (FPEG) with features of thin and compact build, high efficiency and high fuel flexibility is developed. The FPEG consists of a two-stroke combustion chamber, a linear generator and a gas spring chamber. The key technologies to realize stable continuous operation are lubricating, cooling, and control logic. This paper proposes the original structure of the FPEG for enabling stable continuous operation. The main feature is a hollow circular step-shaped piston. The smaller-diameter side of the piston constitutes the combustion chamber, and the larger-diameter side constitutes the gas spring chamber. The larger cross-sectional area of the gas spring chamber leads to lower compression temperature of the gas spring chamber and consequently decreased heat loss. In addition, an oil cooling passage is built in the column stay, which ensures the enough cooling ability of the piston.
Technical Paper

Optimization of Front End Cooling Module for Commercial Vehicle Using CFD Approach

2013-01-09
2013-26-0044
Assessment of cooling performance in the design stage of vehicle allows a reduction in the number of needed prototypes and reduces the overall design cycle time. Frontend cooling and thermal management play an essential role in the early stages of commercial vehicle design. Sufficient airflow needs to be available for adequate cooling of the under-hood components. The amount of air mass flow depends on the under-hood geometry details, positioning and size of the grilles, fan operation and the positioning of the other components. Thermal performance depends on the selection of heat exchanger. This paper describes the effects of several design actions on engine cooling performance of a commercial vehicle with the help of Computational Fluid Dynamics (CFD) simulation tool Fluent™. Front of vehicle design is captured in detailed FE model, considering front bumper, grille, cabin, cargo and surrounding under-hood and underbody components.
Technical Paper

Improve Heat Dissipation Rate of the Vehicle Radiator by Using Carbon Foam Material for the Fin

2013-01-09
2013-26-0071
This paper will explore concepts of next-generation radiators that can adopt the high performance. The goal of this project is to design an advanced concept for a radiator for use in automobiles. Utilize the recently developed high conductivity carbon foam for thermal management in heat exchangers. The technique used to fabricate the foam produces mesosphere pitch-based carbon foam with extremely high thermal conductivity and an open-celled structure. An engineering model is formulated to account for the effects of porosity and pore diameter on the hydrodynamic and thermal performance of a carbon-foam finned tube heat exchanger. The thermal resistances are obtained from well-established correlations that are extended herein to account for the influence of the porous carbon foam.
Technical Paper

A Comparative Study on Map Based and Closed Loop Simulation Model of Coolant Circuit for a Two Wheeler Liquid Cooled Engine

2013-10-15
2013-32-9023
The basic requirement of a vehicle cooling system is to ensure that the components of the engine are adequately cooled under vehicle operating conditions. Engine life and effectiveness can be improved with effective cooling. In designing process, simulation plays a vital role. A clear understanding of the coolant flow and pressure developed within the cooling system is important in designing the coolant circuit. The efficiency of the cooling system depends on the flow delivered by the impeller. The work aims at the study of performance characteristics of a backward curved impeller in a two wheeler cooling system. The objective is to compare the operating points such as pressure drop, flow delivered and power consumed from mapped Computational Fluid Dynamics (CFD) simulation and closed loop CFD simulation. Moving Reference Frame (MRF) model was used to simulate the rotary motion of the impeller.
Technical Paper

Development of Strength Analysis Method for Off-Road Motorcycle Radiator Assembly

2013-10-15
2013-32-9043
The radiator assembly for a liquid-cooled off-road motorcycle is generally attached to the side of the frame. Therefore, if the motorcycle topples over, the radiator may strike the ground and receive an impact through the plastic side cover. This may deform the radiator, reducing its cooling performance or leading to a coolant leak. The strength of the radiator and plastic side cover was designed so that the radiator assembly will not deform easily if the motorcycle topples over at low speeds. However, due to the complex behavior of the radiator assembly in strength tests, a degree of trial-and-error may be necessary to incorporate strength countermeasures by tests alone. Therefore, a strength test simulation method was developed to help design the required strength of radiator assemblies.
Technical Paper

Development of Plastic Fuel Hose with Pressure Pulsation Reduction

2013-10-15
2013-32-9047
Recently, the electronic fuel injection systems have been widely applied to small motorcycles including scooters. In the high pressure fuel lines, plastic hoses have been increasingly used instead of conventional rubber hoses. As the plastic hose is less elastic than the rubber hose, the fuel pressure pulsates more in the plastic hose. To cope with this issue, we have conducted researches on how the fuel pressure pulsation in the plastic hose affects the accuracy of fuel injection. Keeping our eyes on the pulsation damping effects derived from the changes of volume due to the expansion and contraction of hose when the pressure changes, we have established the analysis method for optimization of the inner diameter and the thickness of the hose utilizing CAE analysis. The newly-developed plastic hose is applicable to motorcycles having a single cylinder 250 cm3 engine using an injector of a high static flow rate.
Technical Paper

An Initial Analysis on Sound Insulation Behavior of a Rubber Pipe between Turbocharger Compressor Outlet and Intercooler

2014-04-01
2014-01-0011
Abstract Subject to excitations from pressure pulsations in boost air, the rubber pipe connecting the turbo compressor outlet and the intercooler of an engine vibrates structurally and radiates noise. If the pipe is improperly selected, the resulted vibration may be strong enough to radiate noise which is sufficient to damage the sound quality of the vehicle. This paper presents an initial analysis on this issue. First, formulae are derived for predicting vibration and sound radiation of the pipe for a given pressure pulsation, resulting in sound transmission index for the pipe to quantify its sound insulation behavior. Then effects on the sound transmission index are investigated for pipe parameters such as pipe wall thickness, Young's modulus and density of pipe material.
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