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Technical Paper

Large Eddy Simulation of Spray Injection to Turbulent Duct Flow from a Slit Injector

The behavior of spray injections to turbulent duct flows from a slit injector for direct-injection gasoline engines was investigated using a combination of large eddy simulation (LES) and Lagrangian discrete droplet model (DDM). As a result, diffusion of droplets in stronger turbulent flows was observed at a later stage of the injection. Moreover, we compared calculation and experimental results by generating a pseudo-particle image from the calculation result.
Technical Paper

Development of New Hybrid System for Compact Class Vehicles

Toyota has been evolving a hybrid system since introducing the first mass-production hybrid vehicle in 1997 in response to the increasing automotive-related issues of CO2 emissions, energy security, and urban air pollution. This paper describes a newly developed hybrid system design and its performance. This system was developed with the main purpose to improve fuel consumption, especially for better real world fuel consumption; and to enhance its compatibility with multiple vehicle adoption by downsizing and reducing the weight of its components. At the same time, the hybrid system achieved improved power performance while satisfying stringent emission regulations in the world.
Technical Paper

Development of Shape Optimization Technique Based on The Basis Vector Method

A practical shape optimization technique is presented. We employed the basis vector method to parameterize the shape of the structural domain that is usually discretized by the finite element method. VMA/GENESIS software, the optimization system with finite element analysis, sensitivity analysis, and numerical optimization capabilities, was used for this study. Various design problems such as body, chassis, and engine parts design are solved to demonstrate the effectiveness and the robustness of the present approach for automotive applications.
Technical Paper

Structural Design Technology for Brake Squeal Reduction Using Sensitivity Analysis

The finite element method (FEM) is effective for analyzing brake squeal phenomena. Although FEM analysis can be used to easily obtain squeal frequencies and complex vibration modes, it is difficult to identify how to modify brake structure design or contact conditions between components. Therefore, this study deals with a practical design method using sensitivity analysis to reduce brake squeal, which is capable of optimizing both the structure of components and contact conditions. A series of analysis processes that consist of modal reduction, complex eigenvalue analysis, sensitivity analysis and optimization analysis is shown and some application results are described using disk brake systems.
Journal Article

High Concentration Ethanol Effect on SI Engine Emission

From the energy security and CO2 reduction point of view, much attention has been paid to the usage of bio-fuel. Recently, highly concentrated ethanol is used in some areas (“E85”; 85% ethanol and 15% gasoline in North America and Sweden, and “ethanol”; 93% ethanol and 7% water in Brazil). In these regions, Flexible Fuel Vehicles FFVs are being introduced that are capable of using fuels with a wide range of ethanol concentrations. Advantages of highly concentrated ethanol in internal combustion engine applications are higher thermal efficiency obtained due to higher octane number, and a reduction of nitrogen oxides due to lower combustion temperatures On the other hand, the latent heat of vaporization for ethanol is greater than gasoline, causing poor cold startability and high NMOG emissions. This paper examines the effect of highly concentrated ethanol on exhaust emissions at cold start in a SI- engine.
Technical Paper

Development of High-Strength Aluminum Piston Material

Mass reduction of parts is growing in importance as a means for reducing CO2 emissions from vehicles.The aim of the present research was to contribute to further mass reduction of pistons by developing a new aluminum casting material with highest level of fatigue strength. This goal was achieved using a development concept of creating a homogeneous structure in which Ti was added to create a fine structure and appropriate quantities of Fe and Mn were added to form a compound that is stable at high temperatures. Stand-alone tests of prototype pistons fabricated using the developed material show that the material is 14% stronger than the conventional material, thereby enabling increases in power and mass reduction.
Technical Paper

The Color Specification of Surrogate Roadside Objects for the Performance Evaluation of Roadway Departure Mitigation Systems

Roadway departure mitigation systems for helping to avoid and/or mitigate roadway departure collisions have been introduced by several vehicle manufactures in recent years. To support the development and performance evaluation of the roadway departure mitigation systems, a set of commonly seen roadside surrogate objects need to be developed. These objects include grass, curbs, metal guardrail, concrete divider, and traffic barrel/cones. This paper describes how to determine the representative color of these roadside surrogates. 24,762 locations with Google street view images were selected for the color determination of roadside objects. To mitigate the effect of the brightness to the color determination, the images not in good weather, not in bright daylight and under shade were manually eliminated. Then, the RGB values of the roadside objects in the remaining images were extracted.
Technical Paper

Has Electronic Stability Control Reduced Rollover Crashes?

Vehicle rollovers are one of the more severe crash modes in the US - accounting for 32% of all passenger vehicle occupant fatalities annually. One design enhancement to help prevent rollovers is Electronic Stability Control (ESC) which can reduce loss of control and thus has great promise to enhance vehicle safety. The objectives of this research were (1) to estimate the effectiveness of ESC in reducing the number of rollover crashes and (2) to identify cases in which ESC did not prevent the rollover to potentially advance additional ESC development. All passenger vehicles and light trucks and vans that experienced a rollover from 2006 to 2015 in the National Automotive Sampling System Crashworthiness Database System (NASS/CDS) were analyzed. Each rollover was assigned a crash scenario based on the crash type, pre-crash maneuver, and pre-crash events.
Technical Paper

Long-Term Evolution of Straight Crossing Path Crash Occurrence in the U.S. Fleet: The Potential of Intersection Active Safety Systems

Intersection collisions currently account for approximately one-fifth of all crashes and one-sixth of all fatal crashes in the United States. One promising method of mitigating these crashes and fatalities is to develop and install Intersection Advanced Driver Assistance Systems (I-ADAS) on vehicles. When an intersection crash is imminent, the I-ADAS system can either warn the driver or apply automated braking. The potential safety benefit of I-ADAS has been previously examined based on real-world cases drawn from the National Motor Vehicle Crash Causation Survey (NMVCCS). However, these studies made the idealized assumption of full installation in all vehicles of a future fleet. The objective of this work was to predict the reduction in Straight Crossing Path (SCP) crashes due to I-ADAS systems in the United States over time. The proportion of new vehicles with I-ADAS was modeled using Highway Loss Data Institute (HLDI) fleet penetration predictions.
Technical Paper

Color and Height Characteristics of Surrogate Grass for the Evaluation of Vehicle Road Departure Mitigation Systems

In recent years Road Departure Mitigation Systems (RDMS) is introduced to the market for avoiding roadway departure collisions. To support the performance testing of the RDMS, the most commonly seen road edge, grass, is studied in this paper for the development of standard surrogate grass. This paper proposes a method for defining the resembling grass color and height features due to significant variations of grass appearances in different seasons, temperatures and environments. Randomly selected Google Street View images with grass road edges are gathered and analyzed. Image processing techniques are deployed to obtain the grass color distributions. The height of the grass is determined by referencing the gathered images with measured grass heights. The representative colors and heights of grass are derived as the specifications of surrogate grass for the standard evaluation of RDMS.
Technical Paper

Determine 24 GHz and 77 GHz Radar Characteristics of Surrogate Grass

Road Departure Mitigation System (RDMS) is a new feature in vehicle active safety systems. It may not rely only on the lane marking for road edge detection, but other roadside objects This paper discusses the radar aspect of the RDMS testing on roads with grass road edges. Since the grass color may be different at different test sites and in different seasons, testing of RDMS with real grass road edge has the repeatability issue over time and locations. A solution is to develop surrogate grass that has the same characteristics of the representative real grass. Radar can be used in RDMS to identify road edges. The surrogate grass should be similar to representative real grass in color, LIDAR characteristics, and Radar characteristics. This paper provides the 24 GHz and 77 GHz radar characteristic specifications of surrogate grass.
Technical Paper

Development of High Accuracy NOx Sensor

This paper presents an improvement in the accuracy of NOx sensors at high NOx concentration regions by optimizing the manufacturing process, sensor electrode materials and structure, in order to suppress the deterioration mechanism of sensor electrodes. Though NOx sensors generally consist of Pt/Au alloy based oxygen pump electrodes and Pt/Rh alloy based sensor electrodes, detailed experimental analysis of aged NOx sensors showed changes in the surface composition and morphology of the sensor electrode. The surface of the sensor electrode was covered with Au, which is not originally contained in the electrode, resulting in a diminished active site for NOx detection on the sensor electrode and a decrease in sensor output. Theoretical analysis using CAE with molecular dynamics supported that Au tends to be concentrated on the surface of the sensor electrode.
Technical Paper

Application of Dynamic Mode Decomposition to Influence the Driving Stability of Road Vehicles

The recent growth of available computational resources has enabled the automotive industry to utilize unsteady Computational Fluid Dynamics (CFD) for their product development on a regular basis. Over the past years, it has been confirmed that unsteady CFD can accurately simulate the transient flow field around complex geometries. Concerning the aerodynamic properties of road vehicles, the detailed analysis of the transient flow field can help to improve the driving stability. Until now, however, there haven’t been many investigations that successfully identified a specific transient phenomenon from a simulated flow field corresponding to driving stability. This is because the unsteady flow field around a vehicle consists of various time and length scales and is therefore too complex to be analyzed with the same strategies as for steady state results.
Technical Paper

Variable Induction Systems to Improve Volumetric Efficiency at Low and/or Medium Engine Speeds

A new method of estimating volumetric efficiency has been developed to facilitate parameter studies necessary for designing a Variable Induction System (VIS). The proposed method is based on the application of frequency domain to solve linearized one-dimensional hydrodynamic equations. This method enabled CPU time to be reduced to 1/200 of that required for non-linear calculation in the time domain. Various VISs having sufficient flexibility to ensure practical uses are introduced. Finally, VISs are classified into four groups depending on the pulsation mode. Two examples of VISs are described and tested. Both are found capable of considerably increasing volumetric efficiency at low and medium engine speeds without loss of maximum power.
Technical Paper

Regenration Process of Ceramic Foam Diesel-Particulate Traps

Periodic regeneration of the diesel particulate trap is essential to maintain the collection efficiency and exhaust gas hack pressure at acceptable levels. The objectives of this study are to describe the phenomenology of ceramic foam filter regeneration process and to present its mathematical model. Further simulation study is carried out to estimate the effects of various factors including fuel additive on the ignition and the filter bed temperature and to investigate conditions of excessive temperature which could result in filter destruction. The model is based on the assumption that the regeneration process is composed of two steps. The first step is the additional heat supply from the external energy source, and the second step is the spontaneous combustion propagation. The results from the analytical model agreed very well with the experimental results.
Technical Paper

In-Cylinder Gas Motion of Multivalve Engine-Three Dimensional Numerical Simulation

The characteristic of In-Cylinder gas motion of a multivalve engine is compared with a single intake valve engine, which have been predicted by a three-dimensional numerical simulation and flow visualization. The measured intake valve outlet velocity from helical and straight port was adopted as the boundary conditions. The computer graphics technique has been utilized to express the predicted numerical results as moving picture like visualized flow. This flow pattern was compared with the actual flow pattern visualized with metaldehyde as the tracer using the bottom viewed engine, which showed good agreement. The prediction for the multivalve engine showed that the swirl velocity is rapidly reduced by interaction between the flows from the two port, but the turbulence kinetic energy is similar to that in the engines with a single intake valve with helical port.
Technical Paper

Silicon Nitride Swirl Lower-Chamber for High Power Turbocharged Diesel Engines

This paper describes application of sintered silicon nitride to the swirl lower-chamber in order to improve performance of turbocharged diesel engines. Various stress analyses by finite element method and stress measurements have been applied to determine the design specifications for the component, which compromise brittleness of ceramic materials. Material development was conducted to evaluate strength, fracture toughness, and thermal properties for the sintered bodies. Ceramic injection molding has been employed to fabricate components with large quantities in the present work. Quality assurance for the components can be made by reliability evaluation methods as well as non-destructive and stress loading inspections. It is found that the engine performance with ceramic component has been increased in the power out put of 9PS as compared to that of conventional engines.
Technical Paper

Effects of Fuel Properties and Engine Design Features on the Performance of a Light-Duty Diesel Truck - A Cooperative Study

A cooperative research program has been completed evaluating the relative impact of fuel composition and engine design features on the emissions and fuel economy of a Toyota light-duty diesel truck. The fuel set was blended from commercially available refinery stocks and consisted of eight fuels with independently varying 10% and 90% distillation temperatures and aromatic content. The engine design variables included two compression ratios and three injector types with different fuel flow characteristics, and three injection timings. The main fuel effects observed were increasing hydrocarbon and particulate emissions with increasing aromatic content and, to a much lesser degree, increasing emissions with increasing 10% and 90% point. Changing from the standard fuel injectors to the reference injectors, which had both a higher nozzle opening pressure and a higher initial fuel flow rate, resulted in a substantial reduction in all emissions and improvements in fuel economy.
Technical Paper

The Development of Integrated CAD/CAM System on Engineering Workstation

This paper describes an integrated CAD/CAM system on an EWS. This system is based on the CAD and CAM systems on large scale computers which have been developed and put into practical use in Toyota Motor Corporation. All the functions of these systems are compactly integrated into this system. We have established the following technologies through its development. (1) A method for construction of data structure common to CAD and CAM (2) A database structure that enables efficient data retrievals Owing to these technologies, a non-expensive integrated CAD/CAM system on an EWS has been developed, which can be introduced in small-sized parts suppliers. This system has already been put into practical use since early 1988, and used by more than ten suppliers. Much more suppliers are also planning to introduce this system in near future.
Technical Paper

Development of “Aero Slit” - Improvement of Aerodynamic Yaw Characteristics for Commercial Vehicles

To reduse crosswind sensitivity, the yaw moment should be decreased under both transient and steady conditions. The transient condition is when a vehicle comes out immediately from a tunnel into a crosswind while the steady condition is when driving straight along the coastline. After studying the pressure distribution and the flow pattern around the body, we have reached the ideal air flow at the front-side corner that reduces the yaw moment under both conditions. And we have devised an entirely new method to achieve this better air flow. The method uses an internal flow generated by a pressure difference in the flow feeld to create a jet effect and by using only a duct for internal flow to control the outside air flow. It is done without any change to the exterior styling, except at the flow exit. We call it “Aero Slit”. This “Aero Slit” is effective only under crosswind conditions, and does not increase aerodynamic drag when a crosswind is not blowing.