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Technical Paper

Application of Models of Short Circuits and Blow-Outs of Spark Channels under High-Velocity Flow Conditions to Spark Ignition Simulation

2018-09-10
2018-01-1727
This report describes the implementation of the spark channel short circuit and blow-out submodels, which were described in the previous report, into a spark ignition model. The spark channel which is modeled by a particle series is elongated by moving individual spark particles along local gas flows. The equation of the spark channel resistance developed by Kim et al. is modified in order to describe the behavior of the current and the voltage in high flow velocity conditions and implemented into the electrical circuit model of the electrical inductive system of the spark plug. Input parameters of the circuit model are the following: initial discharge energy, inductance, internal resistance and capacitance of the spark plug, and the spark channel length obtained by the spark channel model. The instantaneous discharge current and the voltage are obtained as outputs of the circuit model.
Technical Paper

Quantitative Optical Analysis and Modelling of Short Circuits and Blow-Outs of Spark Channels under High-Velocity Flow Conditions

2018-09-10
2018-01-1728
This study models short circuits and blow-outs of spark channels. The short circuit model assumes that a spark channel is short-circuited between two arbitrary locations when the electric potential difference between the two locations exceeds the voltage which enables electrical insulation breakage in-between. The threshold voltage can be raised by increasing the distance between the two locations and decreasing the discharge current. Discharge current, in this model, represents the influence of both the spread and the number of electrically charged particles, i.e., electrons and positive ions, distributed near the two locations. Meanwhile, the blow-out model assumes that a strong flow diffuses electrons and positive ions in the spark channel, and consequently the discharge blows out.
Technical Paper

Development of Three-Way Catalysts Enhanced NOx Purifying Activity

2018-04-03
2018-01-0942
Growing concerns about the depletion of raw materials as vehicle ownership continues to increase is prompting automakers to look for ways of decreasing the use of platinum-group metals (PGMs) in the exhaust systems. This research has developed a new catalyst with strong robustness against fluctuations in the exhaust gas and excellent nitrogen oxide (NOx) conversion performance. One of the key technologies is a new OSC material that has low surface area (SA) and high OSC performance. We enhanced the pyrochlore- ceria/zirconia (CZ) which has a very small SA. In order to enhance the heat resistance and promote the OSC reaction, we selected and optimized the additive element. This material showed high OSC performance especially in the temperature range of 400 degrees or less. Another key technology is washcoat structure that has high gas diffusivity by making connected pore in the washcoat (New pore forming technology).
Technical Paper

Spatio-Temporal Frequency Characteristics Measurement of Contrast Sensitivity for Smart Lighting

2016-04-05
2016-01-1420
This study aims at the development of a projection pattern that is capable of shortening the time required by a driver to perceive a pedestrian at night when a vehicle’s high beams are utilized. Our approach is based on the spatio-temporal frequency characteristics of human vision. Visual contrast sensitivity is dependent on spatiotemporal frequency, and maximum contrast sensitivity frequency varies depending on environmental luminance. Conventionally, there are several applications that utilize the spatio-temporal frequency characteristics of human vision. For example, the National Television System Committee (NTSC) television format takes into consideration low-sensitivity visual characteristics. In contrast, our approach utilizes high-sensitivity visual characteristics based on the assumption that the higher contrast sensitivity of spatio-temporal frequencies will correlate more effectively with shorter perception times.
Technical Paper

Constitutive Modeling of Brain Parenchyma Taking Account of Strain Rate Dependency with Anisotropy and Application to Brain Injury Analyses

2016-04-05
2016-01-1485
A reduction in brain disorders owing to traumatic brain injury (TBI) caused by head impacts in traffic accidents is needed. However, the details of the injury mechanism still remain unclear. In past analyses, brain parenchyma of a head finite element (FE) model has generally been modeled using simple isotropic viscoelastic materials. For further understanding of TBI mechanism, in this study we developed a new constitutive model that describes most of the mechanical properties in brain parenchyma such as anisotropy, strain rate dependency, and the characteristic features of the unloading process. Validation of the model was performed against several material test data from the literature with a simple one-element model. The model was also introduced into the human head FE model of THUMS v4.02 and validated against post-mortem human subject (PMHS) test data about brain displacements and intracranial pressures during head impacts.
Technical Paper

Analysis of Friction Coefficient Variation with Moisture between Friction Surfaces

2016-04-05
2016-01-0411
If a vehicle is left in a humid environment, the coefficient of friction between the brake pads and discs increases, generating a discomforting noise during braking called brake squeal. It is assumed that this increase in the coefficient of friction in a humid environment is the effect of moisture penetrating between the brake friction surfaces. Therefore, this paper analyzes the factors causing coefficient of friction variation with moisture between the friction surfaces by dynamic observation of these surfaces. The observation was achieved by changing the disc materials from cast iron to borosilicate glass. One side of the glass brake disc was pushed onto the brake pad and the sliding surface was observed from the opposite side by a charge coupled device (CCD) camera. First, a preliminary test was carried out in a dry state using two pad materials with different wear properties to select the appropriate pad for observing the friction surfaces.
Technical Paper

Development of a Compact Adsorption Heat Pump System for Automotive Air Conditioning System

2016-04-05
2016-01-0181
In order to reduce the energy consumption of the automotive air conditioning system, adsorption heat pump (AHP) system is one of the key technologies. We have been developing compact AHP system utilizing the exhaust heat from the engine coolant system (80-100 °C), which can meet the requirements in the automotive application. However, AHP systems have not been practically used in automotive applications because of its low volumetric power density of the adsorber. The volumetric power density of the adsorber is proportional to sorption rate, packing density and latent heat. In general, the sorption rate is determined by mass transfer resistance in primary particle of an adsorbent and heat and mass transfer resistance in packed bed. In order to improve the volumetric power density of the adsorber, it is necessary to increase the production of the sorption rate and the packing density.
Journal Article

Clarification of Transient Characteristics by Coupled Analysis of Powertrains and Vehicles

2016-04-05
2016-01-1314
With the goal of improving drivability, this research aimed to clarify the mechanism of vehicle longitudinal acceleration, focusing on tip-in acceleration. Conventional typical analysis methods include experimental modal and model-based analysis. However, since the former requires the measurement of impulses and other input forces while the vehicle is stopped, measurement under actual driving conditions is difficult. The latter requires characteristic values such as the stiffness and damping coefficients to be identified in advance, which cannot be achieved either easily or precisely. Therefore, this paper proposes a new experiment-based analysis method. This method enables the acquisition of engine torque and transmission torque/force by measuring only the acceleration values of some components under driving conditions.
Journal Article

Smart Lighting for Enhancing Perception of Pedestrians based on Visual Properties

2016-04-05
2016-01-1414
We investigated a lighting method that supports pedestrian perception by vehicle drivers. This lighting method makes active use of visual characteristics such as the spatio-temporal frequency of contrast sensitivity. Using reasonable parameter values derived from preliminary experiments using a Campbell-Robson chart, we determined a suitable lighting pattern that improves the driver's pedestrian perception. In order to assess the influence of visual characteristics on a reaction-time-dependent task, such as pedestrian perception in nighttime, tests were performed in the target environment, the results of which validated the proposed method.
Journal Article

Typical Velocity Fields and Vortical Structures around a Formula One Car, based on Experimental Investigations using Particle Image Velocimetry

2016-04-05
2016-01-1611
This paper presents typical flow structures around a 60%-scale wind-tunnel model of a Formula One (F1) car, using planar particle image velocimetry (PIV). The customized PIV system is permanently installed in a wind tunnel to help aerodynamicists in the development loop. The PIV results enhance the understanding of the mean velocity field in the two-dimensional plane in some important areas of the car, such as the front-wheel wake and the underfloor flow. These real phenomena obtained in the wind tunnel also help maintain the accuracy of simulations using computational fluid dynamics (CFD) by allowing regular checking of the correlation with the real-world counterpart. This paper first surveys recent literature on unique flow structures around the rotating exposed wheel, mostly that on the isolated wheel, and then gives the background to F1 aerodynamics in the late 2000s.
Technical Paper

Development and Validation of the Total HUman Model for Safety (THUMS) Version 5 Containing Multiple 1D Muscles for Estimating Occupant Motions with Muscle Activation During Side Impacts

2015-11-09
2015-22-0003
Accurate prediction of occupant head kinematics is critical for better understanding of head/face injury mechanisms in side impacts, especially far-side occupants. In light of the fact that researchers have demonstrated that muscle activations, especially in neck muscles, can affect occupant head kinematics, a human body finite element (FE) model that considers muscle activation is useful for predicting occupant head kinematics in real-world automotive accidents. In this study, we developed a human body FE model called the THUMS (Total HUman Model for Safety) Version 5 that contains 262 one-dimensional (1D) Hill-type muscle models over the entire body. The THUMS was validated against 36 series of PMHS (Post Mortem Human Surrogate) and volunteer test data in this study, and 16 series of PMHS and volunteer test data on side impacts are presented. Validation results with force-time curves were also evaluated quantitatively using the CORA (CORrelation and Analysis) method.
Journal Article

Backward Flow of Hot Burned Gas Surrounding High-Pressure Diesel Spray Flame from Multi-hole Nozzle

2015-09-01
2015-01-1837
The backward flow of the hot burned gas surrounding a diesel flame was found to be one of the factors dominating the set-off length (also called the lift-off length), that is, the distance from a nozzle exit into which a diffusion flame cannot intrude. In the combustion chamber of an actual diesel engine, the entrainment of the surrounding gas into a spray jet from a multi-hole nozzle is restricted by the walls and adjacent spray jets, which induces the backward flow of the surrounding gas. A new momentum theory to calculate the backward flow velocity was established by extending Wakuri's momentum theory. Shadowgraph imaging in an optical engine successfully visualized the backward flow of the hot burned gas.
Technical Paper

Development of Advanced Three-Way Catalyst with Improved NOx Conversion

2015-04-14
2015-01-1005
Countries and regions around the world are tightening emissions regulations in reaction to the increasing awareness of environmental conservation. At the same time, growing concerns about the depletion of raw materials as vehicle ownership continues to increase is prompting automakers to look for ways of decreasing the use of platinum-group metals (PGMs) in the exhaust systems. This research has developed a new catalyst with strong robustness against fluctuations in the exhaust gas and excellent nitrogen oxide (NOx) conversion performance. This catalyst incorporates rhodium (Rh) clusters with a particle size of several nanometers, and stabilized CeO2-ZrO2 solid-solution (CZ) with a pyrochlore crystal structure as a high-volume oxygen storage capacity (OSC) material with a slow O2 storage rate.
Journal Article

Improvement in Vehicle Motion Performance by Suppression of Aerodynamic Load Fluctuations

2015-04-14
2015-01-1537
This study focuses on fluctuations in the aerodynamic load acting on a hatchback car model under steady-state conditions, which can lead to degeneration of vehicle motion performance due to excitation of vehicle vibrations. Large eddy simulations were first conducted on a vehicle model based on a production hatchback car with and without additional aerodynamic devices that had received good subjective assessments by drivers. The numerical results showed that the magnitudes of the lateral load fluctuations were larger without the devices at Strouhal numbers less than approximately 0.1, where surface pressure fluctuations indicated a negative correlation between the two sides of the rear end, which could give rise to yawing and rolling vibrations. Based on the numerical results, wind-tunnel tests were performed with a 28%-scale hatchback car model.
Technical Paper

Reduction of the BPF Noise Radiated from an Engine Cooling Fan

2014-04-01
2014-01-0631
This study investigates the reduction of the Blade Passing Frequency (BPF) noise radiated from an automotive engine cooling fans, especially in case of the fan with an eccentric shroud. In recent years, with the increase of HV and EV, noise reduction demand been increased. Therefore it is necessary to reduce engine cooling fan noise. In addition, as a vehicle trend, engine rooms have diminished due to expansion of passenger rooms. As a result, since the space for engine cooling fans need to be small. In this situation, shroud shapes have become complicated and non-axial symmetric (eccentric). Generally, the noise of fan with an eccentric shroud becomes worse especially for BPF noise. So it is necessary to reduce the fan BPF noise. The purposes of this paper is to find sound sources of the BPF noise by measuring sound intensity and to analyze the flow structure around the blade by Computational Fluid Dynamics (CFD).
Technical Paper

Universal Diesel Engine Simulator (UniDES) 2nd Report: Prediction of Engine Performance in Transient Driving Cycle Using One Dimensional Engine Model

2013-04-08
2013-01-0881
The aim of this research is to develop the diesel combustion simulation (UniDES: Universal Diesel Engine Simulator) that incorporates multiple-injection strategies and in-cylinder composition changes due to exhaust gas recirculation (EGR), and that is capable of high speed calculation. The model is based on a zero-dimensional (0D) cycle simulation, and represents a multiple-injection strategy using a multi-zone model and inhomogeneity using a probability density function (PDF) model. Therefore, the 0D cycle simulation also enables both high accuracy and high speed. This research considers application to actual development. To expand the applicability of the simulation, a model that accurately estimates nozzle sac pressure with various injection quantities and common rail pressures, a model that accounts for the effects of adjacent spray interaction, and a model that considers the NOx reduction phenomenon under high load conditions were added.
Technical Paper

Study on the Prediction of VOC Concentration in Vehicle Cabins (1) Investigation of Relationship between Toluene Concentrations and Evaluation Conditions using Interior Parts

2013-04-08
2013-01-0490
The Japan Automobile Manufacturers Association (JAMA) has recommended the voluntary regulation of the levels of volatile organic compound (VOC) emissions from vehicles. However, initiatives to reduce these emissions further are being implemented in Japan to create a healthier and more comfortable environment within vehicles. In this study, it was attempted to estimate the observable amounts of VOC emitted from products used in vehicles based on the actual emission of VOC from the products components. The VOC we focused on was toluene. The amounts of toluene volatilizing from the components of a disassembled vehicular product were measured and tested whether a simple sum of these values could be used to predict the amount of toluene emitted from the whole product. However, it was found this predicted value deviated significantly from the actual amount of toluene emitted from the product.
Technical Paper

Study on the Prediction of VOC Concentration in Vehicle Cabins (2) Development of Labeled Compound Addition Method

2013-04-08
2013-01-0491
The purpose of this study is to construct a method to predict vehicle cabin VOC (volatile organic compounds) concentration. Several methods have been used previously to evaluate VOC emission from interior parts and materials (e.g., sampling bag method, 1 m3 chamber method). However, measurement conditions vary depending on the method used, making it difficult to predict vehicle cabin VOC concentration from the VOC values evaluated for component parts. In this paper, we focused on measurement of toluene concentration using the bag method and investigated the relationship between VOC emissions and measurement conditions. We assumed that the amount of VOC contained in the parts (RA) and the adsorptive capacity of the parts (K) can describe the VOC amount obtained (RG) when the VOC concentration in the bag reaches equilibrium. We developed a novel method incorporating a labeled compound to predict RA and K.
Journal Article

Verification of ASSTREET Driver-Agent Model by Collaborating with the Driving Simulator

2012-04-16
2012-01-1161
This paper proposes a novel method of verifying comprehensive driver model used for the evaluation of driving safety systems, which is achieved by coupling the traffic simulation and the driving simulator (DS). The method consists of three-step procedure. In the first step, an actual driver operates a DS vehicle in the traffic flow controlled by the traffic simulation. Then in the next step, the actual driver is replaced by a driver model and the surrounding vehicle maneuvers are replayed using the recorded data from the first step. Then, the maneuver by the driver model is compared directly with the actual driver's maneuver along the simulation time steps.
Journal Article

Cooling Loss Reduction of Highly Dispersed Spray Combustion with Restricted In-Cylinder Swirl and Squish Flow in Diesel Engine

2012-04-16
2012-01-0689
In diesel engines with a straight intake port and a lipless cavity to restrict in-cylinder flow, an injector with numerous small-diameter orifices with a narrow angle can be used to create a highly homogeneous air-fuel mixture that, during PCCI combustion, dramatically reduces the NOX and soot without the addition of expensive new devices. To further improve this new combustion concept, this research focused on cooling losses, which are generally thought to account for 16 to 35% of the total energy of the fuel, and approaches to reducing fuel consumption were explored. First, to clarify the proportions of convective heat transfer and radiation in the cooling losses, a Rapid Compression Machine (RCM) was used to measure the local heat flux and radiation to the combustion chamber wall. The results showed that though larger amounts of injected fuel increased the proportion of heat losses from radiation, the primary factor in cooling losses is convective heat transfer.
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