Search Results

In this study, we determined the detailed reaction mechanism of CO/NO/O2 for automotive three way catalysts. The N2O formation process obtained from measurements of the reaction properties and the formation process of adsorbed NCO species obtained from surface analysis of platinum group metals were added to a previous detailed surface reaction mechanism. The computational accuracy of the developed reaction mechanism was verified by the one-dimensional simulation software BOOST, and it was found to be sufficient for any combination of platinum group metals and gas concentrations.

To achieve carbon-neutrality, internal combustion engines need to further improve their thermal efficiency to reduce CO2 emissions. To accomplish this, it is necessary to quantify and enhance five factors that control indicated thermal efficiency: compression ratio, specific heat ratio, combustion duration, combustion timing, and heat transfer to wall. In this work, quantitative targets for each factor were defined, which were derived from a simulation that considered the influence of heterogeneity of diesel combustion on thermal efficiency. The simulation utilized a two-zone combustion model. In particular, the targets for the combustion duration, combustion timing and heat transfer to wall were increased significantly compared to those for a conventional engine, in anticipation of an expansion of the load range of premixed charge compression ignition (PCI) combustion to higher loads.

Automobiles will have to be applied strict regulations such as Euro7 against PM, HC, CO. The generation of these components are related to fuel deposition to the wall surface of the combustion chamber. Therefore, the fuel injection model of engine combustion CFD requires accurate prediction about the deposition and vaporization of fuel on the combustion chamber. In this study, multiphase flow numerical analysis that simulates fuel behavior on the wall surface was conducted first. Then, two model formulae about the contact area and the heat flux of a liquid film was constructed based on the result of multiphase flow numerical analysis method. Finally, the new film heat transfer model was constructed from these model formulae. In addition, it was confirmed that new heat transfer model can predict the liquid film temperature obtained by multiphase flow numerical analysis method accurately.

As a technology to reduce the heat loss of engines, heat insulation coating to the surface of combustion chamber has been received a lot of attention. In order to maximize the thermal efficiency improvements by the technology, it is important to clarify the location where heat insulation coating can reduce heat loss more effectively, considering the impact on abnormal combustion etc. In this study, transient behavior of wall heat flux distribution on the piston was analyzed using 3D Computational Fluid Dynamics (CFD) for three combustion modes (spark ignition combustion (SI), homogenous charge compression Ignition (HCCI) and spark controlled compression ignition (SPCCI)).

To get a better understanding of the characteristics of the high pressure gasoline sprays impinging on a wall, a fundamental study was conducted in a high-temperature high-pressure constant volume vessel under the simulated engine conditions of in-cylinder pressures, temperatures, and wall temperatures. The injection pressure was varied from 20 to 120 MPa. The spray tip penetration, vapor mass distribution, and vaporization rate were quantitatively measured with the laser absorption-scattering (LAS) technique. The velocity fields of the wall-impinging sprays under vaporizing conditions were measured with the particle image velocimetry (PIV) technique using silicone oil droplets as tracers. The effects of injection pressure and spray/wall interactions on spray characteristics were investigated. The results showed that the increased injection pressure improved penetration, vaporization, and turbulence of the sprays.

It was important for predicting wall heat flux to apply wall heat transfer model by taking into account of the behavior of turbulent kinetic energy and density change in wall boundary layer. Although energy equation base wall heat transfer model satisfied above requirements, local physical amounts such as turbulent kinetic energy in near wall region should be applied. In this study, in order to predict wall heat transfer by zero dimensional analysis, how to express wall heat transfer by using mean physical amounts in engine combustion chamber was considered by experimental and numerical approaches.

Control of self-ignition timing in a HCCI engine is still a major technical issue. Recently, the application of a non-equilibrium plasma using repetitively discharge has been proposed as the promising technology. However, non-equilibrium plasma reaction in higher hydrocarbon fuel mixture is very complicated. Hence, there have been few calculation reports considering a series of reactions from non-equilibrium plasma production to high temperature oxidation process. In this study, 0-dimensional numerical simulation model was developed in which both reactions of plasma chemistry and high temperature oxidation combustion was taken into account simultaneously. In addition, an ODEs solver has been applied for the reduction of calculation time in the simulation. By comparing calculation results with experiment such as self-ignition timing, the validity of the developed numerical model has been evaluated.

In the development of fuel tank systems, it is important to maintain fuel system integrity even if a car accident occurs. When a fuel tank undergoes a sudden change in velocity, the fuel starts to move and deforms the tank walls and baffle plates, and then the deformation changes the flow pattern of fuel. Because interaction of fuel with tank components is the main cause of fuel spillage upon crash, it is important to predict complex fluid-structure interaction responses at an early stage of crash safety development with a multiphysics simulation. Development of the multiphysics simulation technique was conducted stepwise by examining “fluid motion” and “tank deformation.” First, a sled test of a rigid-wall tank with observation window was conducted to evaluate the fluid motion inside the tank. A numerical model was developed based on an ALE (Arbitrary Lagrangian Eulerian) algorithm for the fluid and a Lagrangian algorithm for the structure.

On-road turbulences caused by sources such as atmospheric wind and other vehicles influence the flow field and increases the drag in a vehicle. In this study, we focused on a scenario involving a passing vehicle and investigated its effect on the physical mechanism of the drag increase in order to establish a technique for reducing this drag. Firstly, we conducted on-road measurements of two sedan-type vehicles passed by a truck. Their aerodynamic drag estimated from the base pressure measurements showed different increment when passed by the truck. This result raised the possibility of reducing the drag increase by a modification of the local geometry. Then, we conducted wind tunnel measurements of a simplified one-fifth scale vehicle model in quasi-steady state, in order to understand the flow mechanism of the drag increase systematically.

For higher mileage vehicles, noise from contaminant ingress is one of the largest durability issues for wheel bearings. The mileage that wheel bearing sealing issues increase can vary due to multiple factors, such as the level of corrosion for the vehicle and the mating components around the wheel bearing. In general, sealing issues increase after 20,000 to 30,000 km. Protecting the seals from splash is a key step in extending bearing life. Benchmarking has shown a variety of different brake corner designs to protect the bearing from splash. This report examines the effect of factors from different designs, such as the radial gap between constant velocity joint (CVJ) slinger and the knuckle, knuckle labyrinth height and varying slinger designs to minimize the amount of splash to the bearing inboard seal. This report reviews some of the bearing seal failure modes caused by splash.

The strong focus on reducing brake drag, driven by a historic ramp-up in global fuel economy and carbon emissions standards, has led to renewed research on brake caliper drag behaviors and how to measure them. However, with the increased knowledge of the range of drag behaviors that a caliper can exhibit comes a particularly vexing problem - how should this complex range of behaviors be represented in the overall road load of the vehicle? What conditions are encountered during coastdown and fuel economy testing, and how should brake drag be measured and represented in these conditions? With the Environmental Protection Agency (amongst other regulating agencies around the world) conducting audit testing, and the requirement that published road load values be repeatable within a specified range during these audits, the importance of answering these questions accurately is elevated. This paper studies these questions, and even offers methodology for addressing them.

A road vehicle’s cornering motion is known to be a compound motion composed mainly of forward, sideslip and yaw motions. But little is known about the aerodynamics of cornering because little study has been conducted in this field. By clarifying and understanding a vehicle’s aerodynamic characteristics during cornering, a vehicle’s maneuvering stability during high-speed driving can be aerodynamically improved. Therefore, in this study, the aerodynamic characteristics of a vehicle’s cornering motion, i.e. the compound motion of forward, sideslip and yaw motions, were investigated. We also considered proposing an aerodynamics evaluation method for vehicles in dynamic maneuvering. Firstly, we decomposed cornering motion into yaw and sideslip motions. Then, we assumed that the aerodynamic side force and yaw moment of a cornering motion could be expressed by superposing linear expressions of yaw motion parameters and those of sideslip motion parameters, respectively.

A mixed time-scale subgrid large eddy simulation was used to simulate mixture formation, combustion and soot formation under the influence of turbulence during diesel engine combustion. To account for the effects of engine wall heat transfer on combustion, the KIVA code's standard wall model was replaced to accommodate more realistic boundary conditions. This were carried out by implementing the non-isothermal wall model of Angelberger et al. with modifications and incorporating the log law from Pope's method to account for the wall surface roughness. Soot and NOx emissions predicted with the new model are compared to experimental data acquired under various EGR conditions.

The human thermal comfort, which has been a subject of extensive research, is a principal objective of the automotive climate control system. Applying the results of research studies to the practical problems require quantitative information of the thermal environment in the passenger compartment of a vehicle. The exposure to solar radiation is known to alter the thermal environment in the passenger compartment. A photovoltaic-cell based sensor is commonly used in the automotive climate control system to measure the solar radiation exposure of the passenger compartment of a vehicle. The erroneous information from a sensor however can cause thermal discomfort to the occupants. The erroneous measurement can be due to physical or environmental parameters. Shading of a solar sensor due to the opaque vehicle body elements is one such environmental parameter that is known to give incorrect measurement.

The vehicle air-conditioning system has significant impact on fuel economy and range of electric vehicles. Improving the fuel economy of vehicles therefore demand for energy efficient climate control systems. Also the emissions regulations motivate the reduced use of fuel for vehicle's cabin climate control. Solar heat gain of the passenger compartment by greenhouse effect is generally treated as the peak thermal load of the climate control system. Although the use of advanced glazing is considered first to reduce solar heat gain other means such as ventilation of parked car and recirculation of cabin air also have impetus for reducing the climate control loads.

The present study investigated the aerodynamic pitching stability of sedan-type vehicles under the influence of A- and C-pillar geometrical configurations. The numerical method used for the investigation is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was employed to realize the prescribed pitching oscillation of vehicles during dynamic pitching and fluid flow coupled simulations. The trailing vortices that shed from the A-pillar and C-pillar edges produced the opposite tendencies on how they affect the aerodynamic pitching stability of vehicles. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation of vehicle, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A- and C-pillars configurations.

Global environmental and economic concerns regarding increasing fuel consumption and greenhouse gas emission are driving changes to legislative regulations and consumer demand. As regulations become more stringent, advanced engine technologies must be developed and implemented to realize desired benefits. Discrete variable valve lift technology is a targeted means to achieve improved fuel economy in gasoline engines. By limiting intake air flow with an engine valve, as opposed to standard throttling, road-load pumping losses are reduced resulting in improved fuel economy. This paper focuses on the design and development of a switching roller finger follower system which enables two mode discrete variable valve lift on end pivot roller finger follower valvetrains. The system configuration presented includes a four-cylinder passenger car engine with an electro-hydraulic oil control valve, dual feed hydraulic lash adjuster, and switching roller finger follower.

An advanced variable valve actuation (VVA) system is characterized following end-of-life testing to enable fuel economy solutions for passenger car applications. The system consists of a switching roller finger follower (SRFF) combined with a dual feed hydraulic lash adjuster and an oil control valve that are integrated into a four cylinder gasoline engine. The SRFF provides discrete valve lift capability on the intake valves. The motivation for designing this type of VVA system is targeted to improve fuel economy by reducing the air pumping losses during part load engine operation. This paper addresses the durability of a SRFF for meeting passenger car durability requirements. Extensive durability tests were conducted for high speed, low speed, switching, and cold start operation. High engine speed test results show stable valvetrain dynamics above 7000 engine rpm. System wear requirements met end-of-life criteria for the switching, sliding, rolling and torsion spring interfaces.

In the present study, numerical simulation coupling convection and radiation in vehicle was done to analyze the formation of the temperature field under the non-uniform thermal condition. The scaled cabin model of simplified compact car was used and the thermal condition was determined. The fore floor, the top side of the inst. panel, the front window and the ceiling were heat source. The lateral side walls were cooled by the outdoor air and the other surfaces were adiabatic. It is same with the experimental condition presented in Part 5. In order to analyze the individual influence of each heat source, Contribution Ratio of Indoor climate (CRI) index was used. CRI is defined as the ratio of the temperature rise at a point from one individual heat source to the temperature rise under the perfect mixing conditions for the same heat source.

The US Environmental Protection Agency (EPA)’s heavy duty diesel emission standard was tightened beginning from 2007 with the introduction of ultra-low-sulfur diesel fuel. Most heavy duty diesel applications were required to equip Particulate Matter (PM) after-treatment systems to meet the new tighter, emission standard. Systems utilizing Diesel Oxidation Catalyst (DOC) and Catalyzed-Diesel Particulate Filter (DPF) are a mainstream of modern diesel PM after-treatment systems. To ensure appropriate performance of the system, periodic cleaning of the PM trapped in DPF by its oxidation (a process called “regeneration”) is necessary. As a result, of this regeneration, DOC’s and DPF’s can be exposed to hundreds of thermal cycles during their lifetime. Therefore, to understand the thermo-mechanical performance of the DOC and DPF is an essential issue to evaluate the durability of the system.