The effect of excess air ratio and in-cylinder water injection on the relationship between in-cylinder pressure and wall heat flux measured at the engine head was investigated using a single cylinder SI engine at 2000 rpm. The obtained results were summarized as the relationship between Reynolds and Nusselt numbers using an average piston speed as representative value. At compression stroke in motoring and unburnt region of firing, exponent of Re in Re vs. Nu plot is close to 0.8 while the exponent in burnt region is higher than 0.8. In addition, the exponent is affected by both excess air ratio and water injection timing.
In this paper, the effect of in-cylinder water injection from intake and exhaust port side on combustion characteristics was compared in lean burn SI engine. The engine bench test at a compression ratio of 17 and excess air ratio of 2.0 shows that indicated thermal efficiency with intake side water injection is higher than that with exhaust side injection at water injection timing (SOIw) = -180 deg.ATDC. At SOIw = -90 deg.ATDC, on the other hand, indicated thermal efficiency in both injection cases is comparable and combustion duration with exhaust side injection is shortened than that with intake side injection.
The objective of this study is to investigate the morphological properties of Particulate Matter(PM) flowing into the post-processing devices of gasoline engines under various engine operating conditions and exhaust system configurations. The effects of conditions and settings including timings of fuel injection and ignition, load variation, Turbo/Charger(T/C), catalysts and Gasoline Particulate Filter(GPF) on the morphology of exhaust PM was examined. The results were obtained via thermophoretic direct sampling of exhaust PM using a water-cooled sampler and Transmission Electron Microscope (TEM) observation and analysis.
In order to improve TWC performance it is essential to prohibit the deactivation of PGM particles on catalyst. In this study we investigated the influence of air to fuel ratio (A/F) in engine-exhaust aging on TWC performance and deactivation property of Rh catalyst. The catalyst reduced at high temperature exhibited the improved thermal durability and superior TWC performance. XAFS spectroscopy indicated existence of the small diameter or the disordered structure of Rh metal particles on the catalyst reduced at high temperature.
This study examines how the enhanced entrainment affects the ignition processes of micro pilot spray using a onedimentional model. The calculation model could quantitatively simulate the increasing tendency of the measured ignition delay. In addition, the simulation result demonstrated that OH radical decreased prior to the onset of the hot flame under injection conditions leading to long ignition delays. Examining the change in the entrainment rate into the spray showed that the decrease in OH radical was related to an increase in enhanced entrainment after the end of injection.
The one dimensional density-based compressible thermal fluid solver was developed in order to clarify the knock phenomena. In this study, the knock phenomena observed during flame propagation in a constant volume vessel were investigated using it. Cool flame appeared in unburned gas compressed due to flame propagation and pressure wave was generated prior to auto-ignition occurrence. Then auto-ignition occurred from premixed flame side, and strong pressure oscillation was observed. These successive phenomena were investigated in detail.
We propose a new controller for a large EV drive system that combines two motors and planetary gears. In previous work, it was confirmed via the use of a test bench that the proposed controller can drive the system with less shock than the conventional controller. This paper presents the results of vibration evaluation on a proving ground using a prototype vehicle with a conventional controller and the proposed controller. A discussion of the experimental results is also provided. We used the evaluation methods used in trains to assess the experimental results because the prototype vehicle we developed is a fully electric vehicle. As a result of this study, it was confirmed that the proposed controller is more effective for actual vehicles than the conventional controller.
It is a matter of great importance to estimate vehicle side slip angle from the view of the vehicle motion control. Performance of vehicle motion control systems are dependent on estimation accuracy of vehicle side slip angle. There are two representive conventional methods to estimate vehicle side slip angle, direct integration method, linear observer method. Direct integration method causes integration error because it uses integrator which integrate sensor offset and noise with time. Another method uses linear observer estimates accurate values in linear region. In the other hand, it can’t estimate accurate values in non-linear region. In this research, we proposed better estimation method which can estimate by only algebraic operations.
The weight reduction and stiffness improvement of automobile body are required. It is necessary to identify the exact location where the modification increases body stiffness is required. A new searching method for stiffening measure locations using strain of space has been developed. Applying this method to a CAE model of automobile body, several stiffening measure locations are identified and stiffness improvement of the body is confirmed.
Deformations of structures consisting mainly of thin metal sheets, such as automobile bodies, comprise sheet stretch, shearing, and bending. The bending component largely reduces the stiffness by reducing the sheet thickness. In this paper, the exponent that should be used to approximate the change in stiffness with respect to the rate of increase in sheet thickness with a power law is introduced as the bending factor that evaluates the degree of bending deformation of the sheet in a structure under elastic deformation. Additionally, the part-bending factor is proposed to evaluate the amount of bending deformation that occurs in each component of the structure. These two factors are applied to simple models that represent the frame joints of an automobile body to evaluate the load transfer efficiency. Furthermore, in the vehicle body structure, parts which require structural improvement to increase stiffness are extracted from the part-bending factor and thickness sensitivity.
The purpose of this study is to establish a method for efficiently reducing interior rain noise. We measured excitation forces caused by rainfalls and found that the frequency characteristics of the forces do not have prominent peaks. Thus, it is concluded that rain noise performance is determined by noise transfer functions between ear position and various points on the roof panel. We proposed a simulation method of rain noise and investigated efficient countermeasures by the simulation. The effectiveness of the countermeasures was verified by comparison with actual measurements.
The buckling behavior of square tubes with ridgelines was studied by pure bending analysis. The increase in ridgeline radius R leads to the increase in maximum bending moment Mmax, which is resulted from the suppression of elastic buckling. This is because the increase in normalized maximum bending moment Mmax/My is large compared to the decrease in section modulus Z.
It is possible to evaluate the risk of side contact between vehicles by the all vehicle trajectory data generated from a certain point and adding vehicle shape and direction information to analyze and evaluate driving behavior. The driving environment information that can be acquired by the driver was digitized, and risk avoidance behavior was evaluated using these. This paper reports on a method of preparing additional information improved the applicability of the vehicle trajectory data for risk assessment.
The present work showed that steady-state flows around the Ahmed body exist at least for the range Re ⩽ 1350. All the obtained steady-state flows can be classified into six regimes depending upon the number of the reverse-flow regions and the occurrence of separation-reattachment. The reverse-flow regions are formed in the order of the wake flow region, near the front of the body, on the slant surface, on the top, and the side of the body as Re increases. Some parts of local-flow-structures which appear at high Re are also involved in the rather low Re flows.
Localization is one of the techniques for enabling autonomous vehicles. In previous studies, LiDAR based localization system has been proposed and tested. However, there is a problem that the system is weak to work with rain and snow conditions. Therefore, Millimeter Wave Radar (MWR) based localization system has been proposed. MWR is robust to weather changes and can sense objects through snow. Accordingly, this paper proposes a localization system based on integrating LiDAR and MWR to improve the accuracy of vehicle estimated position during autonomous driving.
We have proposed a detection technique using Time Domain Reflectometry (which is an instrument to determine the characteristics of electrical lines) to counter threats of physically unauthorized device connection to an in-vehicle network. In this paper, the proposed method was implemented on an in-vehicle evaluation board and evaluated, and has achieved detection success rate of 94.4% even when four or five ECUs were connected.
For the advancement of autonomous driving technology, it is expected to establish cooperative field technology between vehicles. Especially smooth traffic control at intersections is one of the important issues for reducing traffic accidents, however a lot of computing resources are required by the previous approach to calculate an appropriate approach timing to intersection based on a large amount of information, such as location and speed of vehicles, exchanged between the control side and the vehicle side. In this paper, we propose the mechanism to control traffic flow in a roundabout manner by exchanging only the electronic tokens with the virtual entry right of each area dividing intersection based on the concept of token block system used in railways for a long time. As a result of simulation, it is confirmed that traffic flow is controlled smoothly by the proposed mechanism.
A simple prediction method of a diesel spray angle was developed, considering internal nozzle flow characteristics which vary depending on nozzle specifications. Spray behavior near a nozzle was observed as an area to correlate internal and external nozzle flows. Therefore, the method predicts a spray angle directly from internal nozzle flow characteristics obtained by CFD (Computational Fluid Dynamics). The method also involves the effects of a needle lift on the spray angle as well as nozzle hole geometries (e.g. a diameter and a length) which have been used in conventional methods.
Prevention of engine knock is a challenge for the improvement of spark ignition engines. In the previous study, it was suggested that the compression due to flame propagation may alter the chemistry and results in preventing autoignition, that is, knock. In this study, a simplified pulsed compression was used for the detailed kinetic analyses of the relevant phenomena. It was found that the peak concentration of HO2 radical was significantly reduced by the application of the pulsed compression at around first-stage ignition (cool flame). The potential prevention of autoignition and knocking was investigated by zero-dimensional kinetic modeling.
Our turbulent combustion model, which has a method providing turbulence distribution in an engine cylinder using random digits, is able to simulate combustion cycle-by-cycle variations in gasoline engines. However, fluctuations of injected fuel amount and fuel distribution in cylinders were not considered. So a multi-zone combustion model had been developed, and how the fuel distribution in a cylinder effects the cycle-by-cycle variations was investigated using it. Eventually, it is able to be concluded with some calculation results that the fluctuations of fuel distribution in a cylinder and injected fuel amount show some characteristic effects on the cycle-by-cycle variations, but they don’t have any significant effects to induce fast combustion and knocking. The details of the multi-zone combustion model are also described in this paper.
To enhance the effect of downsizing concept, ultra-highly boosted low engine speed condition was performed to obtain wider load range. BMEP:3MPa was achieved at 1750rpm. Fuel economy of the extended load range was also improved. The concept of this research and experimental results are described.
Thermal efficiency of gasoline engines is quite important to prevent the global warming. One of the gasoline engine’s disadvantages is cycle-by-cycle variations, which induce trace-knock at the high speed combustion cycles. Our latest turbulence combustion calculation code already has cycle-by-cycle variation model and chemical reaction calculation for auto ignition prediction, and it was able to simulate trace-knock phenomena. The ignition timing of knock-limitation, however, was not able to be estimated. Therefore, the knock-limitation, which is judged by ears of the experimenters, has been expressed numerically through this study. And it can be used for judging the trace-knock in our calculation. The details of the trace-knock detection concept are described in this paper, and its validity is discussed here.
In this study, to clarify the relationship between fuel film formation and wall characteristics such as surface roughness and thermal conductivity, fuel films formed on various walls (aluminum and quartz glass plates) by wall spray impingement were investigated. Iso-octane was injected by GDI injector set above 30 mm from the wall. Film behavior captured by a high-speed camera was analyzed to obtain a film area on the wall. The fuel film behavior was investigated under different surface roughness (Ra = 0.45 μm-17.1 μm) and various surface temperature conditions (room temperature-200°C). As a result, the fuel film area decreased with an increasing of surface roughness. Evaporation lifetime of fuel film on the aluminum plate (high thermal conductivity) was shorter than that on the quartz glass plate (low thermal conductivity).
The particulate matter (PM) emitted from the diesel engine is collected and removed by the diesel particulate filter (DPF). When performing PM removal, it is necessary to raise the temperature of exhaust gas, so deterioration of fuel efficiency is a serious problem. Therefore, we aim to propose an optimal DPF structure. In this study, we confirmed the dependence of the shape of the DPF during PM deposition-regeneration process using a numerical calculation. The quick change of the pressure drop and the amount of combustion of PM is smaller when the length of the DPF becomes larger. When the DPF length is long, the residual of PM amount at the outlet of DPF decreases. And the PM on the whole surface burns. When the after 10－15 deposition combustion repetitions, the amount of change of PM shows the same pattern. This model can be used for the optimal design of catalytic DPFs by assuming some modes of operation of the DPF device before the experimental approach.
In this study, in-situ XAFS analysis was carried out under the condition of oxidizing and reducing gases at 773 K using a mass-produced catalyst that had deteriorated on an engine bench. As a results of the in-situ XAFS measurement, it is considered that the Rh particles of the Rh single-nano sized catalyst are likely to maintain the high activation state and return to the activation state quickly. Therefore, the NOx purification performance of the Rh single-nano sized catalyst during the acceleration and deceleration region is improved than that of the Rh loaded catalyst.
The piston top ring groove is required to be highly wear resistant because it is subject to load from the piton top ring under high temperature conditions. Although many reports have been made on the bottom side wear of the groove up to now, there was no knowledge on the top side. The present research involved extrapolating wear factors from the results of wear pattern observation. By conducting rig tests based on the design of experiments method, the sensitivity of each factor in wear on the top side of the ring groove was determined and wear due to impact was indicated as the determining factor in wear. In addition, simulation and testing indicated that changing the piston skirt form can reduce this piston behavior and so limit wear.
The viscosity of engine oil becomes lower because the reduction of CO2 emissions produced from automobiles is required in recent years. Antinomy due to low viscosity oil such as severe wear and scuffing at boundary lubrication must be dealt with by additives in the oil. Molybdenum dithiocarbamate (MoDTC) is widely used for friction modifier, but the effect depends on the materials and additives used in combination. We must clarify the reaction process and the ideal structure of tribo-film in order to obtain the effect of MoDTC more. For the purpose, we use Raman spectroscopy and transmission electron microscopy (TEM) to focus on the change in the orientation of MoS2. And we have a purpose to find the method to control the structure of tribo-film by materials, and achieve lower friction in actual engine systems.
In the case of evaluation for the electric power consumption of an electric vehicle, the electric consumption of an air conditioner is too noTable to be ignored. However, the test method about it has yet to be established. This paper aims to consider an evaluation method that can be used for different rates of temperature change and in multiple environments. We first developed the estimating model for electric consumption on an air conditioner using a cumulative temperature difference as an explanatory variable. We found that there were similarities to these parameters, therefore the method can be used to estimate multiple situation.
In this paper vehicle behavior due to road input and driver operation input is simulated for analysis of skyhook shock absorber control. Nonlinearity caused by the difference between target damping force and actual damping force increases vehicle behavior due to driver operation input in case of combination with road input. Countermeasure control logic with additional damping force calculated with vehicle model is proposed to decrease vehicle behavior due to driver input.
When a vehicle runs with driver and road inputs, it is difficult to reduce vibrations of ride comfort and driving stability configuring conventional skyhook damping control suspensions. In this paper, vehicle vibrations for the driver inputs were estimated using vehicle dynamic models. A new control algorithm was proposed using the summation of conventional skyhook damping forces and estimated vibration suppressing forces for the driver. The estimated state accuracy and the vehicle performance were confirmed in actual vehicle tests.
This paper deals with the possibility for construction of the database of the braking friction coefficient on the actual roads from the viewpoint of traffic safety. As the first step of this research, we carry out the measurement and estimation method for road friction characteristics. In this analysis, the magic formula is used to estimate the braking coefficient, the maximum friction coefficient, and the slip ratio that leads to that value. As a result, it is shown that road friction characteristics on actual road surface can be estimated accurately.
Personal Mobility Vehicle (PMV) which has an inward tilting angle according to the steering angle, turns mainly by the lateral force due to the tire camber angle. Although the steering torque characteristics are very different from those of automobiles, there are not many examples which studied the steering torque characteristics of PMV. In this study, the steering torque characteristics of PMV with inward tilting mechanism are organized and the characteristic requirements for the steering mechanism are discussed. Finally, additional centering torque proportional to provisional lateral acceleration is proposed to produce natural and controllable steering torque characteristics for PMV with inward tilting mechanism. Low road friction and oversteer conditions are also considered.
A lot of four-wheeled vehicle accidents were caused by lane departure in hilly and mountainous area. Therefore, it is considered that road alignment such as curvature of road and gradient of road etc. affects these accidents. This paper studied to make 3D model for accident location using SfM method with photos of the location, and analyzed the road alignment. Furthermore, authors extracted hazard factors of traffic accidents from the model, and considered the evaluation model for accident risk in hilly and mountainous area. The accident risk is calculated by the rate of vehicle velocity divided by the side slip limitation speed. Three actual accident locations were analyzed using this method. In results, it was found that these locations had 0.7 and more accident risk rate, and this method can evaluate the accident risk in hilly and mountainous area.
Our aim is to improve an HMI that reduces the workload by distributing the different resources (visual / auditory / verbal / spatial etc…) related with human’s recognition. In this study, the effect on the driver’s workload is clarified by comparing two types of operations: the current voice operation as single modal, and the operation uses gaze pointing and voice command as multi modal. Regarding to gaze and voice control, there are 2 use cases that are more effective than the current voice operation. It was confirmed by subjective evaluation (NASA-TLX) and objective evaluation (Prediction Error) at the driving simulator tests.
We propose a method to create failure-scenarios of an autonomous driving vehicle by training other surrounding vehicles by means of multiagent adversarial reinforcement learning. Failure in driving environments might lead to catastrophic results. Hence, when developing a software of autonomous driving cars, we must find as many failure-cases as possible and then improve the software. However, as the software becomes complicated, it is hard to find failure-scenarios that are useful for the software improvement. Hence, we propose a framework to create various failure-scenarios of an autonomous car by training other car(s) via reinforcement learning. We demonstrate the effectiveness of our proposed method with two kinds of experiments.