Refine Your Search

Topic

Author

Affiliation

Search Results

Training / Education

Introduction to Commercial and Off-Road Vehicle Cooling Airflow Systems

2024-09-12
Vehicle functional requirements, emission regulations, and thermal limits all have a direct impact on the design of a powertrain cooling airflow system. Given the expected increase in emission-related heat rejection, suppliers and vehicle manufacturers must work together as partners in the design, selection, and packaging of cooling system components. The goal of this two-day course is to introduce engineers and managers to the basic principles of cooling airflow systems for commercial and off-road vehicles.
Technical Paper

Knockdown Factor Estimation of Stiffened Cylinders under Combined Loads - A Numerical Study

2024-06-01
2024-26-0417
Airframe section of rockets, missiles and launch vehicles are typically cylindrical in shape. The cylindrical shell is subjected to high axial load and an external pressure during its operation. The design of cylinders subjected to such loads is generally found to be critical in buckling. To minimize the weight of cylinders, it is typically stiffened with rings and stringers on the inner diameter to increase the buckling load factor. Conventionally the buckling load estimated by analytical or numerical means is multiplied by an empirical factor generally called Knockdown factor (kdf) to get the critical buckling load. This factor is considered to account for the variation between theory and experiment and is specified by handbooks or codes. In aerospace industry, NASA SP 8007 is commonly followed and it specifies the kdf as a lower bound fit curve for experimental data .
Technical Paper

Thermal Analysis of Prismatic Core Sandwich Structural Panel for Hypersonic Application

2024-06-01
2024-26-0422
Hypersonic flight vehicles have potential applications in strategic defence, space missions, and future civilian high-speed transportation systems. However, structural integration has significant challenges due to extreme aero-thermo-mechanical coupled effects. Scramjet-powered air-breathing hypersonic vehicles experience extreme heat loads induced by combustion, shock waves and viscous heat dissipation. An active cooling thermal protection system for scramjet applications has the highest potential for thermal load management, especially for long-duration flights, considering the weight penalty associated with the heavier passive thermal insulation structures. We consider the case of active cooling of scramjet engine structural walls with endothermic hydrocarbon fuel. We have developed a semi-analytical one-dimensional heat transfer model considering a prismatic core single cooling channel segment as a representative volume element (RVE) to analyse larger scale problems.
Technical Paper

Simulation Analysis of the Dynamics Characteristics of Battery Electric Vehicle Transmission System under Impact Condition

2024-04-09
2024-01-2719
This paper analyzes the dynamic characteristics of transmission system of battery electric vehicle through simulations, the research method and conclusions can serve as a theoretical basis and reference for the design of vehicle system architecture.To accurately describe the torsional vibration characteristics of battery electric vehicle's transmission system, it is necessary to reasonably simplify the system, furthermore, when subjected to short-wave uneven road surface excitation, the connection between the rigid ring in the SWIFT model and the ground belongs to single-point contact and cannot represent the tire enveloping properties.Around the above issues, a method has been proposed to simplify the gearbox model into a force-coupled model with centralized damping, stiffness, and mass, along with an equivalent road surface model consisting of elliptical cams in series that can represent tire enveloping propertie, correspondongly,an evaluation criterion has been established, which utilizes the ratio of the peak torque of the impact force at the rear wheel hub after encountering a step to the maximum output torque of the gearbox as the impact coefficient.In four-wheel-drive vehicle models, the impact coefficient of the front axle is greater than that of the rear axle when going uphill, and when going downhill, the impact coefficient of the rear axle is greater than that of the front axle, for another, in both uphill and downhill scenarios, the impact coefficient of the four-wheel-drive vehicle model is greater than that of the front-wheel-drive and rear-wheel-drive models.
Technical Paper

Ducted Fuel Injection: Confirmed re-entrainment hypothesis

2024-04-09
2024-01-2885
Testing of ducted fuel injection (DFI) in a single-cylinder engine with production-like hardware previously showed that simply adding a duct structure increased soot emissions at the full load, rated speed operating point. In the authors’ 2021 SAE paper, which reported these findings, it was hypothesized that the DFI flame, which is faster than a conventional diesel combustion (CDC) flame, and has a shorter distance to travel, was being re-entrained into the on-going injection around the lift-off length, thus reducing air entrainment into the on-going injection. The engine operating condition and the engine combustion chamber geometry were duplicated in a constant pressure vessel. The experimental setup used a 3D piston section combined with a glass fire deck allowing for a comparison between a CDC flame and a DFI flame via high-speed imaging. Testing clearly confirmed the detrimental effect of the DFI flame re-entrainment hypothesis presented in the previous on-engine work.
Technical Paper

Combustion Chamber Development for Flat Firedeck Heavy-Duty Natural Gas Engines

2024-04-09
2024-01-2115
The widely accepted best practice for spark-ignition combustion is the four-valve pent-roof chamber using a central sparkplug and incorporating tumble flow during the intake event. The bulk tumble flow readily breaks up during the compression stroke to fine-scale turbulent kinetic energy desired for rapid, robust combustion. The natural gas engines used in medium- and heavy-truck applications would benefit from a similar, high-tumble pent-roof combustion chamber. However, these engines are invariably derived from their higher-volume diesel counterparts, and the production volumes are insufficient to justify the amount of modification required to incorporate a pent-roof system. The objective of this multi-dimensional computational study was to develop a combustion chamber addressing the objectives of a pent-roof chamber while maintaining the flat firedeck and vertical valve orientation of the diesel engine.
Technical Paper

Assessing the Effects of Computational Model Parameters on Aerodynamic Noise Characteristics of a Heavy-Duty Diesel Engine Turbocharger Compressor at Full Operating Conditions

2024-04-09
2024-01-2352
In recent years, with the development of computing infrastructure and methods, the potential of numerical methods to reasonably predict aerodynamic noise in compressors has increased. However, aerodynamic acoustic modeling of complex geometries and flow systems is currently immature, mainly due to the greater challenges in accurately characterizing turbulent viscous flows. Therefore, recent advances in aerodynamic noise calculations for automotive turbocharger compressors were reviewed and a quantitative study of the effects for turbulence modeling (Shear-Stress Transport (SST) and Detached Eddy Simulation (DES)) and time-steps (2°and 4°) in numerical simulations on the performance and acoustic prediction of a compressor under full operating conditions was investigated. The results showed that for the compressor performance, the turbulence models and time-step parameters selection were within 1.5% error of the simulated and measured values for pressure ratio and efficiency.
Technical Paper

Pre-chamber Combustion System Development for an Ultra-lean Gasoline Engine

2024-04-09
2024-01-2110
Amid rising demands for fuel efficiency and emissions reduction, enhancing the thermal efficiency of gasoline engines has become imperative, which requires higher efficiency combustion strategies and integrated optimized design to maximize the work output from fuel. In gasoline engines, both increasing the compression ratio and using lean burn mode improve the thermal efficiency effectively. Although there is limited scope for increasing the compression ratio due to the higher sensitivity to knocking, especially under stoichiometric conditions, reduced sensitivity could be got with leaner mixture fill into cylinder, which can further increase the specific heat ratio and thermal efficiency. However, realizing the efficiency benefits of lean burn in gasoline engines necessitates overcoming critical challenges like ensuring robust ignition process and accelerating burning rates to achieve short, stable combustion durations.
Technical Paper

An Improved AEB Control System Based on Risk Factors with Consideration of Vehicle Stability

2024-04-09
2024-01-2331
Intelligent vehicle-to-everything connectivity is an important development trend in the automotive industry. Among various active safety systems, Autonomous Emergency Braking (AEB) has garnered widespread attention due to its outstanding performance in reducing traffic accidents. AEB effectively avoids or mitigates vehicle collisions through automatic braking, making it a crucial technology in autonomous driving. However, the majority of current AEB safety models exhibit limitations in braking modes and fail to fully consider the overall vehicle stability during braking. To address these issues, this paper proposes an improved AEB control system based on risk factors (AERF). The upper-level controller introduces the risk factor (RF) and proposes a multi-stage warning/braking control strategy based on preceding vehicle dynamic characteristics, while also calculating the desired acceleration.
Technical Paper

Evaluating the effects of an Electrically Assisted Turbocharger on scavenging control for an Opposed Piston Two Stroke (OP2S) compression ignition engine

2024-04-09
2024-01-2388
Opposed piston two-stroke (OP2S) diesel engines have demonstrated a reduction in engine-out emissions and increased efficiency compared to conventional four-stroke diesel engines. Due to the higher thermal efficiency and absence of a cylinder head, the heat transfer loss to the coolant is lower near the ‘Top Dead Center’. The selection and design of the airpath are pivotal in realizing the benefits of the OP2S engine architecture. Like any two-stroke diesel engine, the scavenging process and the composition of the internal residuals are predominantly governed by the pressure differential between the intake and the exhaust ports. Moreover, a significant portion of the work involved in pumping air is carried out externally to the engine cylinder which needs to be accounted for when calculating brake efficiencies.
Technical Paper

3-Dimentional Numerical Transient Simulation and Research on Flow Distribution Unevenness in Intake Manifold for a Turbocharged Diesel Engine

2024-04-09
2024-01-2420
The design of engine intake system affects the intake uniformity of each cylinder of the engine, which in turn has an important impact on the engine performance, the uniform distribution of EGR exhaust gas and the combustion process of each cylinder. In this paper, the constant-pressure supercharged diesel engine intake pipe is used as the research model to study the intake air flow unevenness of the intake pipe of the supercharged diesel engine. The pressure boundary condition at the outlet of each intake manifold is set as the dynamic pressure change condition. The three-dimensional numerical simulation of the transient flow process in the intake manifold of diesel engine is simulated and analyzed by using numerical method, and the change of the internal flow field in the intake manifold under different working conditions during the intake overlapping period is discussed.
Technical Paper

A Preliminary Study on the Evaporative Cooling System for FCEV

2024-04-09
2024-01-2406
Recently, fuel cell stacks have been applied to various fields, and the importance of thermal energy management is increasing along with the increase in required power and heat dissipation. In particular, research and development is underway to improve various performance due to FCEV characteristics with a lower cooling temperature than ICE. Therefore, it is essential to develop a new cooling system to overcome these limitations. This study is a prior study to develop the evaporative cooling system by using water as a by-product of the stacks, and aims to identify the effects of variables affecting the performance. The commercial codes were used to simulate the quantitative sprayed area for actual evaluations. The sprayed area was chosen as a key indicator of cooling performance from the viewpoint of evaporation rate, which is well known to be proportional to the evaporation effect on the surface of the fin.
Technical Paper

Research on the Flow and Heat Exchange Performance of the Chiller for Electric Vehicles

2024-04-09
2024-01-2412
A two-particle lumped parameter model was developed for the chiller, and an experimental device was built to measure flow and heat exchange of the chiller. Empirical correlations for the convective heat transfer coefficients on both the coolant and refrigerant sides were obtained by fitting the experimental data. The influence of herringbone corrugated plate parameters, including angle, pitch, and depth, on performance of chillers at different Reynolds numbers (Re) was investigated. In modeling of a chiller two-phase and overheated zones of the refrigerant are considered simultaneously, and their respective areas were calculated to enhance the accuracy of the model. Using the Wilson plot method in experimental design, the convective thermal resistance of heat transfer on both sides was separated from the total thermal resistance to determine the actual coefficient of convective heat transfer.
Technical Paper

Control Strategy for Engine Silicone Oil Fan Clutch Based on Engine Cooling System

2024-04-09
2024-01-2234
In order to study the influence of engine silicone oil fan clutch on the performances of engine cooling system under different control strategies, a model of engine cooling system for commercial vehicle is established. The working characteristics of the silicone oil clutch and the measured performance parameters of the cooling system components are taken into account in our proposed model. Modeling methods for different silicone oil fan control strategies are also given. Using the established model, the performance parameters under different vehicle speeds, such as engine outlet coolant temperature and cooling fan power consumption, are calculated and analyzed. The in-suite measurement of the engine cooling system is carried out to get the temperatures of engine inlet and outlet from engine ECU. The model is validated by the comparison between the calculation and the measured results.
Technical Paper

1D Modeling Approach for Prediction of Heat Transfer in Aftertreatment System and Sensors Module

2024-04-09
2024-01-2739
The study of temperature distribution and heat transfer over non-uniform geometry is of great importance to engineers because of universal occurrence in many engineering applications such as diesel engine, boilers, heaters, radiators, dosers, etc. Performance of engine and its components (mechanical and electronic) is highly depending upon efficient thermal management. An accurate heat transfer analysis is necessary in automotive application and power plant. This study presents one dimensional model for prediction of conjugate heat transfer in Aftertreatment system and Sensors Module (Nox Sensor, PM Sensor, EGTS etc..) for diesel engine. Three-dimensional conductive, convective and radiative thermal analysis is computationally expensive as underhood models are of complex shape in nature and total turnaround time for product development project is also significantly high.
X