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Technical Paper

Using Analytical Techniques to Understand the Impacts Intelligent Thermal Management Has on Piston NVH

2022-06-15
2022-01-0930
In order to align with net-zero CO2 ambitions, automotive OEMs have been developing increasingly sophisticated strategies to minimise the impact that combustion engines have on the environment. Intelligent thermal management systems have a positive impact on friction generated in the power cylinder by improving the warmup rate of cylinder liners and heads. This increase in temperature results in an improved frictional performance and cycle averaged fuel consumption, but also increases the dynamic piston to liner clearance and therefore the propensity for piston slap. In low temperatures this piston slap can substantially decrease the NVH quality to unacceptable levels. Using analytical techniques, it is possible to model the thermo-structural and NVH response of the power cylinder with different warm up strategies.
Technical Paper

Measurements and Modeling of the Temperature of a Li-polymer Battery Provided with Different Coatings for Heat Dissipation

2022-06-14
2022-37-0012
The battery efficiency is strongly affected by the operating temperature, granting the best performance in a limited range. Great attention is given to the design and the testing of materials for the battery heat dissipation. In the present study, the thermal behavior of a Li-polymer pouch-type cell, which is part of a battery pack for electric vehicles, is investigated. The cell is provided with different coatings of carbon, graphene, and silicone, used in turn, to dissipate the heat generated during the operation in natural convection. The coating is placed on only one side of the battery while the other one is inspected via thermal imaging. Optical diagnostics in the infrared band are used to evaluate the bi-dimensional distribution of the battery surface temperature and the effect of the coating. Different operating conditions are tested by varying the current demand.
Technical Paper

Model based design, prototyping and testing of a very small size electrically driven centrifugal pump

2022-06-14
2022-37-0024
Within automotive sector, there are several high-performance applications, like, for instance, those referred to racing and motorsport, where cooling needs are usually fulfilled by simple circuits with conventional low-efficiency pumps. The cooling needs in these applications are represented by low flow rates delivered and pressure ratios which depends on the permeability of the circuits. The operating conditions of these pumps are usually characterized by very high revolution speeds which intrinsically causes a low efficiency and critical intake phenomena (cavitation). The high speed of revolution requested by the reduced space available on board invites to consider an electrical actuation which avoids mechanical connections with the engine and produces very integrated and compact solutions guaranteeing interesting cooling performances useful also for more conventional engines (thermal management due to the electrical actuation of the pump).
Technical Paper

Development of a High-Voltage Battery Pack Thermal Model at Vehicle Level for Plug-in Hybrid Applications

2022-06-14
2022-37-0023
The ongoing global demand for greater energy efficiency plays an essential role in the automotive industry, as the focus is moving from ICEs to hybrid (HEVs) and electric (EVs) vehicles. New virtual methodologies are necessary to reduce the development effort of this technologies. In this context, the thermal management of the vehicle high voltage battery pack is becoming increasingly important, with significant impact on the vehicle’s range in different environmental scenarios. In this paper, an advanced method is proposed to compute 3D temperature distribution of the cells of a high voltage battery pack for Plug-in Hybrid (PHEV) or full electric (EV) applications. The thermal FE model of a complete PHEV vehicle was integrated with an electrical NTG equivalent circuit model of the HV battery to compute the heat loads of the cells.
Technical Paper

Measurements and Modeling of the Temperature of a Li-polymer Battery Provided with Different Coatings for Heat Dissipation

2022-06-14
2022-37-0013
The battery efficiency is strongly affected by the operating temperature, granting the best performance in a limited range. Great attention is given to the design and the testing of materials for the battery heat dissipation. In the present study, the thermal behavior of a Li-polymer pouch-type cell, which is part of a battery pack for electric vehicles, is investigated. The cell is provided with different coatings of carbon, graphene, and silicone, used in turn, to dissipate the heat generated during the operation in natural convection. The coating is placed on only one side of the battery while the other one is inspected via thermal imaging. Optical diagnostics in the infrared band are used to evaluate the bi-dimensional distribution of the battery surface temperature and the effect of the coating. Different operating conditions are tested by varying the current demand.
Technical Paper

Non-Parametric Optimization of Heat Sinks for Power Dense Motor Controllers

2022-05-26
2022-26-0008
With the future of mobility moving towards electrification, there is an ever-increasing demand in both aerospace and automotive industry for achieving higher power density in inverters, controllers, etc. This has made thermal management a challenging task and warrants a need for exploring innovative cooling techniques to manage the dissipated heat. This paper focuses on a liquid cooled thermal management system for power dense applications. The heatsink design presented here is a pin fin arrangement staggered to induce swirling flow, which has been proven to enhance heat transfer. The traditional heatsink optimization involves creating a design of experiments (DoE) with parameters like fin diameter, spacing and height and performing thermal simulations to arrive at a design with enhanced heat transfer characteristics.
Technical Paper

Mathematical Modeling & Simulation of Thermal Heat Load for Cabin & Cockpit of Aerial Vehicle

2022-05-26
2022-26-0015
The thermal heat load requirement for the cabin and the cockpit of aerial vehicle varies with various conditions comprises of altitudes and different weather conditions. The mapping of the heat load w.r.t. the above conditions is a complex phenomenon, which involves difficult mathematical modeling. The aerodynamic design of the aerial vehicle allows the flow of ambient air to contribute in the cabin and cockpit heat load along with passengers, pilots & co-pilots heat load at various weather conditions. The current study considers the mathematical modeling of the cabin and cockpit of aerial vehicle w.r.t. various weather conditions and altitudes and simulate the heat load requirements. The estimation of the heat load plays a key role in thermal management systems of the aerial vehicle for both the cabin and cockpit. The objective of this study is to highlight the importance of heat load requirement of the aerial vehicle and methods to simulate it.
Journal Article

Thermal Management Optimization of Prismatic Lithium-Ion Battery Using Phase Change Material

2022-04-21
Abstract High technology expertise and strong advancement in electric vehicles and Lithium (Li)-ion battery devices and systems have increased the speed of development and application of new equipment. It is reported that Li-ion battery life reduces almost by 60 days per degree temperature rise in an operational temperature of 30°C to 40°C, which makes cooling a high priority. The current study focuses on cooling the battery system using Phase Change Material (PCM) placed as bands of different dimensions around the prismatic battery. Eight novel designs of varying dimensions were constructed for three-volume scenarios. The heat generations considered in this study are 6,855 W/m3, 12,978 W/m3, 19,100 W/m3, and 63,970 W/m3. The data obtained was trained using an artificial neural network (ANN), and an equation was attained to fit the data. The optimum placement of PCM with respect to the number of bands and dimensions was achieved through a Genetic Algorithm.
Journal Article

Research on Transient Thermal-Structural Coupling Characteristics and Thermal Error Prediction of Ball Screw Feed System

2022-04-21
Abstract The thermal error of ball screw is the main factor affecting the accuracy of machine tool. Establishing an accurate thermal error model of ball screw is the key to compensate the error of machine tool. The ultimate goal of the research work in this article is to develop a comprehensive modeling method that can predict the temperature rise and thermal error of ball screw. In view of the problem that the reciprocating motion of ball screw nut was ignored in the traditional thermal error model, a transient thermal-structural coupling model considering the actual working conditions was proposed. ANSYS parametric design language (APDL) was used to set the ball screw nut as the moving heat source load, and the displacement-time relationship between the ball screw nut and the ball screw was defined. The temperature and thermal deformation distribution of the ball screw under the action of the bearing and the heat source of the ball screw nut were simulated.
Journal Article

Analysis of Infrared Signature from Aircraft Frontal Aspect due to Skin Friction Heating

2022-04-20
Abstract At supersonic aircraft speeds, aerodynamically heated surfaces, e.g., nose, wing leading edges, are infrared (IR) signature sources from the tactically crucial frontal aspect. This study numerically predicts and then illustrates the minimization of IR contrast between the nose and background sky radiance by the emissivity optimization (εw,opt) technique, which has the least performance penalties. The IR contrast between the aircraft nose and its replaced background in 1.9-2.9 μm short-wave IR (SW-IR), 3-5 μm medium-wave IR (MW-IR), and 8-12 μm long-wave IR (LW-IR) bands are obtained. The IR contrast especially in LW-IR (i) increases with flight Mach number (M ∞) for a given flight altitude (H) and εw (ii) decreases with increasing H for a given M ∞ and εw. The εw,opt for a flight altitude of 5 km is found to decrease from 0.99 at M ∞ = 0.001 (low subsonic) in all three bands to 2 × 10−4 in MW-IR and 0.0213 in LW-IR bands at M ∞ = 3 (high supersonic).
Journal Article

Study of Statistical Narrow-Band Models for Infrared Signature of an Aeroengine Exhaust Plume in Mid-wave Infrared and Short-Wave Infrared Band

2022-04-20
Abstract An aeroengine exhaust plume is one of the important sources of infrared (IR) signature in the 3-5 μm and the 2-3 μm bands. Analysis, characterization, and modeling of the exhaust plume IR emission are needed for insight into its role in aircraft survivability against IR-guided missiles. The IR signature estimation of aeroengine exhaust needs estimation of radiative properties of absorbing-emitting exhaust gases, e.g., carbon dioxide (CO2) and water vapor (H2O). The radiative properties of the gases can be estimated by a mathematical model with a spectroscopic database of these gases. Low-Resolution Transmission (LOWTRAN), Moderate-Resolution Transmission (MODTRAN), High-Resolution Transmission (HITRAN), and High-Temperature Transmission (HITEMP) are some commonly used spectroscopic databases. This study compares Statistical Narrowband (SNB) models with the various other mathematical models used for the estimation of radiative properties of exhaust gases.
Technical Paper

Prediction of Electric Vehicle Transmission Efficiency Using a New Thermally Coupled Lubrication Model

2022-04-13
2022-01-5026
We present a new method to predict the power losses in electric vehicle (EV) transmission systems using a thermally coupled gearbox efficiency model. Friction losses in gear teeth contacts are predicted using an iterative procedure to account for the thermal coupling between the tooth temperature, oil viscosity, film thickness, friction, and oil rheology during a gear mesh cycle. Crucially, the prediction of the evolution of the coefficient of friction (COF) along the path of contact incorporates measured lubricant rheological parameters as well as measured boundary friction. This allows the model to differentiate between nominally similar lubricants in terms of their impact on EV transmission efficiency. Bearing and gear churning losses are predicted using existing empirical relationships. The effects of EV motor cooling and heat transfers in the heat exchanger on oil temperature are considered.
Journal Article

Temperature and Consumed Energy Predictions for Air-Cooled Interior Permanent Magnet Motors Driving Aviation Fans—Part 1: Mathematical Analytical Solutions for Incompressible Air Cases

2022-04-13
Abstract The increase in worldwide awareness of environmental issues has necessitated the air transport industry to drastically reduce carbon dioxide emissions. To meet this goal, one solution is the electrification of aircraft propulsion systems. In particular, single-aisle aircraft with partial turboelectric propulsion with approximately 150 passenger seats in the 2030s are the focus. To develop a single-aisle aircraft with partial turboelectric propulsion, an air-cooled interior permanent magnet (IPM) motor with an output of 2 MW is desired. In this article, mathematical system equations that describe heat transfer inside the target air-cooled IPM motor are formulated, and their mathematical analytical solutions are obtained.
Journal Article

Thermal Design and Analysis of a Prismatic Lithium-Ion Battery Cooled by Mini-channels

2022-04-08
Abstract Batteries have profound importance in today’s world as they are useful in powering the future without fossil fuels because of their properties, such as high energy density and durability. Volumetric and packing efficiency is better for a prismatic cell when compared with a cylindrical cell, whereas heat will be higher for a prismatic cell. This makes them a hot topic of research and development (R&D), with researchers finding ever more ways to improve. In this work, an attempt is made to study the effect of various mini-channel configurations on prismatic cell thermal management including the effect of C-rate, coolant flow rate, and coolant inlet temperature on temperature gradient and maximum cell temperature using ANSYS-Fluent by using an equivalent circuit model (ECM) in multi-scale multidimensional (MSMD) add-on module.
Journal Article

Subcooled Flow Boiling in High Power Density Internal Combustion Engines II: Numerical Modeling

2022-04-05
Abstract Results from a thermal survey measurement campaign on a four-cylinder Volvo engine was presented in Part I of this article. The focus was predominantly on heat transfer in the engine coolant jacket. This part presents numerical modeling focused specifically on the coolant flow and associated heat transfer in the coolant jacket using computational fluid dynamics (CFD), as a part of a high-resolution complete engine 3D conjugate heat transfer (CHT) model. With local nucleate boiling being an indispensable phenomenon in high power density engines, a dedicated boiling model is essential and is to be used in conjunction with CFD while analyzing heat transfer in the coolant jacket. This article validates a new boiling model with data obtained from the extensive thermal survey measurements, presented in Part I.
Journal Article

Performance Prediction of a Practical Low-Pressure-Ratio Highly Efficient Split-Cycle Recuperated Engine

2022-04-04
Abstract Split-cycle recuperated engines are promising candidates to compete with hydrogen-based fuel cells for high-duty cycles. They can potentially achieve similar, or even higher, efficiencies at the cost of historically cheap piston engines. However, existing approaches are either limited in efficiency or difficult to develop, mainly because of the challenges around the high-temperature expansion piston. This article presents a practical architecture of a low-pressure-ratio, recuperated split-cycle engine with a contact-free expansion piston using labyrinth seals supported by thermodynamics and numerical modeling. The engine operates under a regenerative dual Brayton cycle to combine the benefits of constant pressure heat recuperation and near-constant volume combustion. Thermodynamics results reveal pre-compressing the residual mass in the expansion cylinder before intake is crucial.
Technical Paper

Simulation and Control of Battery Thermal Management System for Electric Vehicle

2022-03-31
2022-01-7016
GT-POWER and Simulink software are used to explore the influence of factors such as external temperature and radiator layout on the battery thermal management system, and prepare for the subsequent exploration of the joint simulation of the battery thermal management system under low temperature radiator threshold control and fuzzy control. The cooling and energy-saving effects of the fan and compressor using fuzzy control are analyzed. The results show that cooling the power battery with refrigerant is not affected by the external temperature. Under the condition of good temperature consistency of battery pack, compared with the threshold control, the fuzzy control strategy for fan and compressor speed can save about 23.1% and 14% of energy consumption respectively, which helps to improve the driving range of the vehicle.
Journal Article

Subcooled Flow Boiling in High Power Density Internal Combustion Engines I: Thermal Survey Measurement Campaign

2022-03-31
Abstract Nucleate boiling occurs inadvertently in the coolant jacket of high power density internal combustion engines, especially in vicinity of regions experiencing high thermal loads. Occurrence of boiling can be beneficial and be an efficient way to improve heat transfer locally near hot spots, but excessive boiling can be detrimental to structural integrity of the engine. While most of the efforts to understand boiling have been focused on experiments in simplified geometries, this article presents results from thermal survey measurement on a production engine. The purpose of the measurement campaign is to understand the intensity and extent of nucleate boiling occurring in different parts of the engine coolant jacket. This is achieved by sweeping across different input parameters, such as engine operating load point, cooling system operating pressure, coolant flow rate, and coolant inlet temperature.
Technical Paper

Cross-Flow Radiator Design Using CFD for FSAE Car Cooling System and Its Experimental Validation Using the GEMS Data Acquisition System

2022-03-29
2022-01-0374
The cross flow design of a radiator and its heat transfer and temperature drop was simulated then validated by using a data acquisition system during both static and dynamic running conditions of a Formula SAE car. The data acquisition system simulated and validated the radiator's cross flow design and heat transfer, as well as the temperature drop, under static and dynamic conditions in a car. The optimal radiator design determines the engine's operating temperature and the desired temperature drop gain through proper design of the inner core, number of fins and tubes, and radiator material. The purpose of a properly designed radiator is to prevent the combustion engine from heating up above its operating temperature [1]. The radiator's design is based on the operating temperature of the CBR 600RR engine. The highest temperature recorded was around 105°C, and in the worst case scenario, it can reach 110°C.
Technical Paper

Experimental and Analytical Study of Temperature Swing Piston Coatings in a Medium-Duty Diesel Engine

2022-03-29
2022-01-0442
The use of Thermal Barrier Coatings (TBCs) has been shown to be a promising technology to improve internal combustion engine efficiencies by reducing heat rejection to the coolant and oil. In recent studies, temperature swing coatings that have simultaneously low volumetric heat capacity and low thermal conductivity have been shown to be particularly promising in this regard. In this study, a traditional and a newer swing coating are applied to the piston of an on-road medium-duty diesel engine to assess the benefits of their use. An analytical wall temperature model is coupled to the 1-D engine simulation software GT-POWER and predictions of wall temperature, heat transfer and chemical heat release rate are presented. The swing coating is found to yield an ~1.2% efficiency benefit at the highest load condition studied alongside an 80°C improvement in exhaust temperature at the lowest load condition studied compared to a reference uncoated piston.
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