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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

From Idle to 7.5 bar IMEPg – Using Fuel Stratification to Control LTGC with Next-Cycle Capability

2024-04-09
2024-01-2821
Low-temperature gasoline combustion (LTGC) engines can provide high efficiencies with very low NOx and soot emissions, but rapid control of the combustion timing remains a challenge. Partial Fuel Stratification (PFS) was demonstrated to be an effective approach to control combustion in LTGC engines. PFS is produced by a double direct injection strategy with most of the fuel injected early in the cycle and the remainder of the fuel supplied by a second injection at a variable time during the compression stroke to vary the amount of stratification. Adjusting the stratification changes the combustion phasing, and this can be done on cycle-to-cycle basis by adjusting the injection timing. In this paper, the ability of PFS to control the combustion during wide engine load sweeps is assessed for regular gasoline and gasoline doped with 2-ethylhexyl nitrate (EHN). For PFS, the load control range is limited by combustion instability and poor combustion efficiency at low loads.
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

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

Evolution of Light-duty Gasoline Compression Ignition (LD-GCI) for High Efficiency and US Tier3- Bin30 Emissions

2024-04-09
2024-01-2092
It is widely recognized that internal combustion engines (ICE) are needed for global transport for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieving demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco's PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing. The fuel injection system was a modified diesel system with high injection rate and 2000 bar pressure rating.
Technical Paper

Light Duty engine performance characteristics with Dimethyl Ether and Propane

2024-04-09
2024-01-2126
Paper documents the performance characteristics of a compression ignition HYUNDAI 2.2L engine operating with Dimethyl Ether (DME) and Propane mixtures. The engine features a high-pressure common rail fuel injection system designed to operate with DME and Propane. The main component of the fuel system is a high-pressure pump that incorporates an electronic inlet metering valve commanded on a crank angled base to control the rail pressure. The pump, which requires no pressure regulator, provides the flow needed to the injectors without flow returning to the inlet. Tests are carried out at injection pressures from 300bar to 1000bar, and the engine ECU is aided with the use of an Engine Controller High speed Oversight unit (ECHO) to provide combustion phasing control and improved cylinder-to-cylinder uniformity, providing improved optimization over the testing effort.
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.
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