Diesel engines have a high thermal efficiency, but 20-30% of the input heat quantity is lost as the cooling loss. It is important to investigate the mechanism of wall heat transfer with impinging flame on the wall in improving the thermal efficiency. Therefore, in order to investigate the correlation of diesel flame and the wall heat loss, chemiluminescence photography, luminous flame photography and measurement of heat flux were carried out by using a wall insertion type constant volume vessel.

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Diesel engines have a high thermal efficiency, but 20-30% of the input heat quantity is lost as the cooling loss. It is important to investigate the mechanism of wall heat transfer with impinging flame on the wall in improving the thermal efficiency. Therefore, in order to investigate the correlation of diesel flame and the wall heat loss, chemiluminescence photography, luminous flame photography and measurement of heat flux were carried out by using a wall insertion type constant volume vessel.

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In this study, we focused on fuel reforming and investigated the effects of fuel reforming on thermal efficiency of a compression ignition engine by numerical simulation. As a result of fuel reforming simulation, it became clear that EGR dividing was effective in order to obtain energy gain with small quantity of fuel, but generating a large amount of soot would become a problem. Moreover, the simulation results of combustion with reformate gas showed that higher efficiency was obtained in the case of combustion with low unburned reformate gas emissions. However, NOx emission was increased due to higher combustion temperature.

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The purpose of this research is to improve engine thermal efficiency, by reducing cooling loss through combustion chamber walls, with a new concept heat insulation methodology called "TSWIN (Thermo-Swing Wall Insulation Technology)". In the former report (3^rd report), "SiRPA (Silica Reinforced Porous Anodized Aluminum)" was developed and applied on the top surface of the Diesel piston. A series of cycle simulation revealed the mechanism of thermal efficiency improvement by SiRPA. Then the influence of engine operating condition for fuel efficiency improvement was confirmed by 1-dimensional heat transfer simulation and surface temperature measurement.

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For the improvement of the calibration process in CI engine, it is required to optimize both fuel injection timing and its rate by using the model based control (MBC) on ECU (on-board) during cycle-by-cycle calculation. The on-board MBC is consisted of 6 calculation models, such as a gas flow, a spray, a formation of mixture, combustion, an ignition delay, and a heat loss. The present study developed the on-board gas flow model, and our successive study discussed the on-board heat loss model that could estimate the wall temperature of cylinders, because the heat loss is significantly related to the turbulence of in-cylinder gas flow. Since gas flows are changed with each position in an in-cylinder, it was modeled by varying the combination of four kinds of flows, such as a swirl flow, a squish flow, an axial direction flow and an injection flow. For the calculation of the on-board gas flow, we improved the new model to discretize the calculation points and to reduce the calculation load, referred to as the discretized gas flow model. Furthermore, the wall temperatures of cylinders were estimated by using the discretized gas flow model, whose root mean square error was 0.9 %, compared with the results from the 3-D CFD simulation. In addition, the calculation time for the model was less than 40 μs, which corresponded to the time within 1 cycle.

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For the improvement of the calibration process in CI engine, it is required to optimize both fuel injection timing and its rate by using the model based control (MBC) on ECU (on-board) during cycle-by-cycle calculation. The on-board MBC is consisted of 6 calculation models, such as a gas flow, a splay, a formation of mixture, combustion, an ignition delay, and a heat loss. The present study developed the on-board heat loss model, which needs to calculate the on-board gas flow model developed in our successive study. This model enables to predict the following five parameters, such as a wall heat flux, a wall heat loss, a polytropic index, an in-cylinder gas temperature, and auto-ignition timing. For the calculation of the on-board heat loss, we improved the new model to discretize the calculation points and to reduce the calculation load, referred to as the discretized heat loss model. Furthermore, the polytropic index and the auto-ignition timing were estimated by using the discretized heat loss model, whose RMS error was 0.1% and the estimation error was less than 1 deg., respectively, compared with the results from the 1-D engine simulation. In addition, the calculation time for the model was less than 40 μs, which corresponded to the time within 1 cycle.

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Post-injection has been attracted attention as the Diesel Particulate filter regeneration method. However oil dilution that occurs when fuel spray impinges lubricating oil film on cylinder liner is an issue which cannot be ignored. Because oil dilution is leading to deterioration of sliding properties of piston and thermal efficiency, there is need to clarify spray impingement behavior on lubricating oil film. Therefore, in this research, we focus on the fuel dilution phenomenon by post injection and aim for modeling. Then, the critical weber number was measured to make it possible to judge whether or not the fuel droplet impinges on lubricating oil film splash or deposition. As a result, it was found that the fuel droplet impingement behavior on lubricating oil film is classified into three behaviors by two critical weber numbers. First, W_crP = (272 + 11600 δ_non^1.29)La^0.01, second, We_crS = (211 + 2255 δ_non^1.05) La^0.05, La = ρ_ο σ_ο d_in / μ ο², Here, ρ_ο is density of Lubricating Oil, σ_ο is surface tension of Lubricating Oil, μ_ο is viscosity coefficient of engine oil, and La is Laplace number.

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For environmental protection, it is necessary to further reduce harmful emission of the internal combustion engines. In this research, in order to reduce the PN (particle number), the flow inside of the injector was analyzed. As a result, we got guidelines to reduce tip wetting. The guidelines are as follows. 1) Reduction of the fuel flow velocity in the vertical direction to the hole axis around upstream of the injection hole. 2) Selection of hole arrangement and hole angle so as to suppress separation of flow inside the injection hole. 3) Improvement of radial air flow velocity on the tip surface to reduce tip wetting. We confirmed the reduction of PN with the optimized injector samples by the actual engine test.

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A phenomenological diesel combustion model has been developed. This model is able to predict a heat release rate in a good accuracy for various operating conditions. The combustion model is implemented into one dimensional fluid dynamics simulation to predict the diesel engine transient performance taking turbochager response into account. The combustion control and designing turbocharger concept for improving a transient performance are studied using engine and turbocharger simulation.

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Super lean burn is conceived as a method for improving the thermal efficiency of SI engine. Also, to improve the thermal efficiency, the ignition timing is advanced to advance the combustion phase. However, when the combustion phase is excessively advanced, knocking occurs, which hinders the improvement of thermal efficiency. It is necessary to avoid knocking because the amplitude of the large pressure wave may cause noise and damage to the engine. In this study, SIP surrogate fuels (S5H, S5R) were used to investigate the effect of differences in fuel compositions on knocking characteristics in lean burn SI engine. It was found that toluene suppresses knocking and n-heptane promotes in five fuel components.

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Seizure resistance of these surface modification methods for the engine sliding parts have not been not sufficiently evaluated. In this study, the specimens with a new surface modification methods were investigated to evaluate the friction properties, running-in and seizure behaviour. As a result, an aluminum alloy with a new surface modification shows low friction properties and good running-in behaviour, seizure resistance was also improved. It was found that the bonding strength of MoS₂ to the Al alloy matrix was improved when shot peening with a tin ball was treated to the matrix.

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The distribution of fuel sprays and mixture in a combustion chamber with twin shaped semi-premixed diesel combustion were analyzed with CFD code. Combustion is realized with a combination of the premixed combustion with the first injection and the spray combustion with the second injection during or just after the premixed diesel combustion. The CFD code suggested that in a combustion chamber dividing the first and the second fuel sprays to upper and lower zones of the chamber, effected with a projection provided in the combustion chamber, the second injection spray injected into the burned zone of the first injection was significantly reduced compared with that in an ordinary re-entrant combustion chamber.

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To reduce smoke formation in twin shaped semi-premixed diesel combustion from the second injection fuel spray entering the low oxygen and high temperature region caused by the first combustion, a combustion chamber dividing the first and the second fuel sprays into upper and lower zones in the cavity by a projection was newly designed. In the first report, the distribution of fuel spray and mixture in the newly designed combustion chamber were analyzed with CFD code. In this report, the characteristics of the twin shaped semi-premixed diesel combustion with the new combustion chamber were investigated in a diesel engine. The combustion efficiency improves and the smoke emissions reduce significantly in comparison with an ordinary re-entrant shaped chamber.

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As a breakthrough technology to achieve improvement in thermal efficiency and reduction in various energy losses simultaneously, multiple-injector combustion control concept has been investigated by means a single-cylinder heavy-duty diesel engine. In this study, the effect of newly designed fuel injection nozzle specification for further improvement in brake thermal efficiency by reducing both combustion duration and wall heat loss was numerically and experimentally confirmed.

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In combustion control system of diesel engines, a multiple injection is commonly used, and the fuel quantity and the timing of each injection should be properly controlled. Therefore, the combustion control is essentially a multi-input and multi-output (MIMO) control problem. In this paper, we apply an 𝐻_∞ control theory, which can design a controller for MIMO system systematically, to the combustion control. Further, the selection of weighting functions are discussed. The effectiveness of the proposed method is evaluated by conducting simulations.

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The combustion process of the latest Diesel Engine became able to use multistage fuel injection time and quantity of jet as a control input, and the possibility of the control performance enhancement increased markedly. However, under the present conditions, the static maps are made using DOE (Design of experiments) design which needs time, cost, and, hands, and it is mainstream to perform the feedforward control by the static map. By the control by such a static map, it is difficult to realize the most suitable engine control depending on a driver and environment. In this study feedback error learning (FEL), and let indicate online using a technique of AI (artificial intelligence), and adapt and/or learn a feedforward controller, the control system which can learn to a driver and environment positively. In order to confirm the effectiveness of designed control algorithm, we make the numerical simulation based on the Tokyo University discrete-time model and the experiment with the Tokyo University engine bench.

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In order to elucidate the urea decomposition process for constructing the SCR catalyst model, an accurate quantitative measurement method for isocyanic acid, which is an intermediate product of urea, is required. In this study, the development of standard gas generation method of isocyanic acid and the measurement of isocyanic acid with Fourier Transform Infrared Spectrometer（FT-IR）in synthetic exhaust gases consisting of CO, CO₂, NO, NO₂, NH₃, N₂O, and H₂O, were carried out. As a result, it is possible to measure the HNCO concentration up to 150 ppm by FT-IR. The measurement accuracy (defined as twice the standard deviation) was obtained to be ± 2.0 to 2.9 ppm.

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To correspond to the issues of climate change and energy security, the engine thermal efficiency has been enhanced by expanding combustion limit. The current main technology to enhance combustion is high tumble which strengthens turbulence intensity in the combustion chamber. However, the existence of combustion limit still remains even though the combustion limit is expanded. Therefore, the chemical reaction of fuel molecules is focused on in this research and it is clarified that some fuel molecules contribute to enhance combustion. This paper describes the effect of the difference of fuel molecules on combustion characteristic.

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The purpose of this research is to improve the thermal efficiency of a fuel reforming engine system using low concentration hydrous ethanol that can be produced with lower cost compared to pure ethanol. In this study, we investigated improvement in thermal efficiency of the system by three effects (1) lean burn, (2) high compression ratio, and (3) exhaust heat recovery by fuel reforming. The improvement in thermal efficiency was confirmed in the system with a fuel reformer installed in the exhaust pipe of the engine

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Though it is necessary to evaluate the emission emitted by vehicles under real driving to grasp local vehicle emission pollution, it is impossible to measure the real world emissions for all vehicles. In this study, the simulation model based on the engine emission test and/or the vehicle emission test has been constructed for the purpose of an evaluation of vehicle emission characteristics under real driving conditions. This paper reports the prediction accuracy of this simulation model.

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We developed a real-time measurement technique for the amount of PM accumulated on DPF using a narrow-band microwave of 2.4 to 2.5 GHz. We modeled the PM accumulation amount, the temperature values measured inlet and outlet of the DPF and microwave absorption in a transient test using the actual device. When the PM accumulation amount was estimated in the other transient test, it was confirmed that the amount of the PM accumulated on DPF can be estimated with a high accuracy. The output of the model followed the PM amount in real time by the difference of 0.5g/L or less.

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The purpose of this work is to develop an after-treatment system for removing particulate matters (PM) using non-thermal plasma. This plasma after-treatment system has the advantage of low pressure drop because of its flow-through structure, different from wall-flow particulate filters. It can continuously remove PM at the low temperature and is suitable for compact cars. In this study, we have developed a plasma reactor with high durability, a pulse power supply with high power efficiency and a power saving control method for the plasma system. The developed system achieved high PM removal performance and high durability with low supply power.

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Diesel Particulate Filter (DPF) is widely used to trap Particulate Matter (PM), which is one of the atmospheric pollutants. PM oxidation catalyst increases the efficiency to oxidize PM. The catalyst can keep the efficiency in contact with PM layer. So, when PM layer is detached from the catalyst surface or ash prevents contact between catalyst and PM, the efficiency deteriorates. In this report the movement of PM layer and ash layer was visualized in Ag₂SO₄/Al₂O₃ coated DPF during the regeneration. The authors showed the regeneration method to remove both detached PM and ash to keep PM oxidation efficiency.

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The process of particulate matter oxidation in hexagonal diesel particulate filters (HEX DPF) was numerically analyzed by one dimensional calculation model. The numerical results show that the distribution of a mass flow rate among Inlet/Outlet wall-through flows and bypass flows cause the change of the relationship between heat release rate and convective heat transport on the Inlet/Outlet walls and Inlet/Inlet walls. The maximum temperature of HEX DPF during regeneration process is suppressed by this change of relationship.

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Importance of the reduction of oil consumption in developing the internal combustion engine is increasing for the protection of global environment. Oil pressure under the oil control ring could affect the oil consumption, so estimation of the oil pressure is required in order to analyze mechanism of oil rising through the piston ring. In this study, the factors of oil pressure generation are investigated by the numerical analysis model, and also knowledge of piston design for the purpose of reducing the oil consumption is shown.

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The relation between distribution of belt friction force and belt slip velocity was simulated by FE model. It was found that when pulley thrust was gradually reducing, sliding slip between the pulley and all elements occurred before belt friction coefficient reached the maximum point. When sliding slip occurred, the friction force in the radial direction of pulley existed. As sliding progressed, the direction of friction force accorded with the tangential direction of pulley, and the belt friction coefficient reached the maximum point. This characteristics simulated by FE model corresponded well with measurement results, verifying the slip mechanism.

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One of the topics for the phase 2 of GTR13(HFCV) activity is the study of an appropriate burst pressure of tanks. For this study, we evaluated any degradation and variability of the burst pressure due to hydraulic sequential tests on 70MPa compressed-hydrogen tanks. When the burst pressure after the hydraulic sequential testing was compared with the initial burst pressure, the pressure proved to have dropped by a few percent while the variation increased, and the main factor for the increase in the burst pressure variation was considered to be the drop test comprising the sequential tests.

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To reduce CO₂ emissions of garbage truck, we developed a fuel cell garbage truck. It was designed based on the analysis result of the garbage collection route of the target route, Shunan city of Yamaguchi prefecture. We performed chassis dynamo test for quantitatively comparing environmental performances with conventional diesel garbage truck. We analyzed possibility of further reduction of running energy of fuel cell garbage truck by self-developed vehicle simulator. We evaluated reduction of CO₂ emissions by introduction of Shunan city by self-developed CO₂ emissions estimation method based on energy consumption measured by chassis dynamo test.

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Thermal management technology to improve fuel economy is required for Hybrid vehicle during warm-up in winter. A predictive thermal management control method was developed in this study. Based on predicted long term parking location by vehicle usage, this study developed a method to manage simultaneous vehicle warm-up and battery charging. Tested winter fuel economy was improved and long term parking locations could be predicted with high accuracy with this control.

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We have developed an efficient driving force distribution algorithm capable of minimizing tire slip dissipation power on contact patches during acceleration and deceleration while turning. Although the power dissipation mechanism was also validated from the viewpoint of “macro” input power to wheels, how the power is consumed on tire contact patch has not been clarified. Therefore, we studied “micro” tire slip power dissipation mechanism using tire brush model that is widely used to calculate tire generation force. The analysis result shows the power is dissipated only in the slip region and the amount is equal to the “macro” input power. The consistency between energy source and sink of vehicle-tire dynamics was proved theoretically.

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The torsion beam suspension in which the left and right wheels are connected by a beam has a characteristic that the wheel alignment varies according to the mutual relationship of the inputs to the left and right wheels. In order to calculate wheel alignment for different inputs between left and right wheel in vehicle simulation, we developed a method that can estimate wheel alignment accurately by approximating the suspension characteristics.

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Electric vehicles (EVs) are attracting attention due to growing awareness of environmental issues such as fossil fuel depletion and global warming. Consequently, this report examines a control method to minimize energy consumption for vehicles with different motor-based drive systems. The driving force distribution control laws to minimize energy consumption in a vehicle with two or three motors were calculated and compared to a vehicle with four motors. This paper also compares the energy consumption when turning while accelerating or decelerating, and discusses the vehicle behavior in these scenarios. The derived control laws can be applied to vehicles with any motor-based drive system.

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Multiphase topology optimization using two materials and void with modulated design area are discussed. The optimization considers two-phase design area where not all kind of materials are allowed. Minimum compliance optimizations under constant individual volumes are performed under solid isotropic material with penalization with linear finite element method. The optimized topology and final compliance are compared between the case for all-mixed design and the one with limited mixed and unmixed areas design

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A passenger seated on a 6-axis motion base is exposed to vehicle sway that simulate lane-changing with the seat varied its side support and insert part's deflection. Motion data of the passenger have been measured by a motion capture system from which the motion amounts of the physical parts has been calculated. The side support conditions of seat, which tend to be highly evaluated, are discussed by considering the angular velocity of head as a main factor of motion amount and the subjective evaluation (acceptable vibration or not acceptable vibration) results.

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In recent years, many Advanced Driver Assistance Systems, or ADAS have been put on the market and automated driving technologies are developed. Many of them utilize laser scanner. Although laser scanner has the advantage of high resolution, its performance will not be certified in adverse weather conditions. In this study, a four layer laser scanner is employed to detect roadside structure. From the reflection data, location of snow-covered road edge is estimated.

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A total of eighty-one side collision simulations were conducted with four THUMS Version 4 adult female occupant models seated. The collision conditions were determined based on actual vehicle side collisions. Occupant kinematics and head injury were predicted and compared. The simulation results indicated that serious head injury (AIS3+) was likely to occur when the far side occupant head contacted the near side occupant. It was also shown that the kinematics of the far side occupant was different from that of the near side occupant.

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Advanced driver assistance systems and autonomous driving systems are being enhanced to deal with various types of collision use-cases. To handle those complicated scenarios, the rational and understandable control algorithm on a 2D plane is required. The 2D control methodology assuming virtual repulsive force from obstacles is introduced. As an example, the formulation on the path for collision avoidance against both obstacles on the right and left sides of ego-vehicle is shown. The simulation is conducted not only for lateral parallel shift but also arbitrary approach angle against obstacles. Assuming virtual repulsive force field, the collision avoidance paths can be calculated as the combination of two parabola curves and the control activation points also can be calculated geometrically.

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Reduced model based on Proper Orthogonal Decomposition (POD) was established from FE sampled results in IIHS SUV side impact, and displacement modes of center pillar were reconstructed. Displacement reconstructed by the reduced model showed good correlations with results by FE models in case of changing length or thickness of center pillar parts, and the max displacements of center pillar were predicted within 6.2% errors of FE results in a few seconds. Variations of displacements mode of center pillar also were investigated by reduced model based on POD.

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In this study, we aim to design a thermal environment that improves both the arousal level and the thermal comfort of the drivers. We conducted experiments using driving simulator, in order to investigate the effects of changes in indoor temperature on the arousal level and the thermal comfort of the drivers, and the driving performance due to the changes in the arousal level. As a result, the arousal level increased and maintained at an alert state, corresponding to the fall in indoor temperature, and then it was maintained at a high state, although the indoor temperature rose and the drivers felt comfortable after the temperature fell and the arousal level rose. These results showed that it is possible to improve both the arousal level and thermal comfort of the drivers by periodic changes in indoor temperature.

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Towards prevention of traffic accidents involving pedestrians, the objective of this study is to construct a pedestrian collision risk assessment method of right-turns at intersections based on driving behavior indices related to drivers’ risk anticipation for driver-assistance systems. In this paper, first, environmental elements that affect driving behavior was selected based on naturalistic driving data. Next, the influence of the environmental elements was examined by a risk-scene reproducing experiment. Results showed that road width affects collision risk assessment and collision risk of different road width conditions could possibly be evaluated by additional consideration of vehicle position and direction.

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The optimal display distance for a head up display showing augmented reality (AR-HUD) was investigated, based on visual cognition time and subjective assessment values of visibility. The tendency was that the further the display distance, the shorter the cognition time and the better the subjective assessment value. For display ranges of some length or further, improvements in both indices levelled off (reached saturation). We propose that the optimal display distance for AR-HUD systems is 15 m or more, the distance at which both indices reach saturation. .

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Recently, traffic accidents caused by elderly drivers have been increasing. It is thought that the reason of accidents is decline of driving skill caused by aging. In order to assist driving according to driving skill of elderly drivers, it is necessary to evaluate senior driver’s driving behavior. In this paper, using driving school instructor's driving as safe driving, the safe driving ability including elderly driver was evaluated by driving behavior at stop sign intersection measured by drive recorder. Using the evaluation method and criteria, relationship of elderly driver’s cognition, physical strength and driving behavior was studied.

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Traffic accidents caused by elderly drivers have been increasing in Japan. This research aims to investigate the relationships between unsafe driving behavior and simple battery of cognitive tests, which are the Speed Anticipation Reaction Test (SART) and the Trail Making Test Part B (TMT-B). Total 68 elderly drivers' naturalistic driving behavior were surveyed using driving recorders with 4 cameras and GPS. We aggregated unsafe behaviors using the data. The study categorized elderly drivers based on the score of SART and TMT-B, into nine types. The result indicated specific categories are associated with a high frequency of unsafe driving behavior.

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This driving simulator study investigated drivers' ability to resume manual control from a level 3 automated vehicle. Volunteers were asked to engage in different types of non-driving related tasks including watching videos or texting. During the tasks, a take-over request (TOR) was provided to the drivers in two conditions with and without the TOR display on the task screen. The results showed that, compared to video watching, texting tasks tended to cause delayed driver's responses to the TOR. Further, it was suggested that adding a TOR display on the task screen contributed to reduce collision risk by suppressing continued concentration on the distractive tasks.

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This study focuses on the effect of gradual transition from automated driving to manual driving on driving behavior. In the experiment using a driving simulator, participants were instructed to perform based on gradual transition consisted of the combination of the speed control and direction control with the time difference between them. The time difference was designed as 30 seconds, 5 seconds and 0 seconds. Their driving performances for the transition were measured and evaluated in terms of driving performance and vehicle behavior. Based on the experimental results, the effect of gradual transition on driver performance was discussed.

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This study describes the depth perception in a moving vehicle when using an automotive 3D Head-Up Display which places virtual images in the appropriate 3D position. In the experiment, we compared the 3D-HUD with a conventional augmented reality HUD, which has fixed focal depth, in terms of visibility. The visual contents were displayed in various distances. Participants were instructed to answer how deep the displayed content indicated while performing the visual task. Judgement time and error were measured during the experiment. Based on the results, we discussed how the driver's depth perception was influenced by image position and vehicle traveling.

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The importance of information sounds is increasing with spread of driver assistance systems. In this paper, the characteristics of information sound that can provide not only urgent/critical feel but also luxury feel were studied. Wave type, fundamental frequency, envelope, harmonic composition and blowing period were decided with subjective evaluations. Luxury feel has only odd harmonic, low fundamental frequency and release envelope. Luxury and urgent/serious feel has non-harmonic only in the frequency band of 2000 to 4000 Hz and intermittent blowing pattern.

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At Levels Two and Three systems of automated driving, it is important that how to keep drive's arousal level high. This study focused on methods which provides awakening stimuli for the driver constantly. In this study, the authors examined three conventional workloads to the driver during automated driving, and proposed two new workloads which were named “Information Provision” and “Single Light”. For the effect comparison among these methods, the authors did experiment by using driving simulator with 16 general drivers. In this paper, we describes the details of this study, experiment, and some trends according to the result.

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Motion by a passenger seated on a 6-axis motion base has been measured with a motion capture system while the passenger is exposed to motion that simulates lateral sway of a vehicle. The relationship between the motion index calculated from the motion of the physical parts of the passenger and the subjective evaluation (acceptable or unacceptable) has been analyzed statistically using logistic regression. The result suggests that the angular velocity of skull is a major factor that influences subjective evaluation of acceptability.

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Recently, aerodynamic development for production car is performed with CFD and wind tunnel with moving ground to reproduce the real world conditions. However, it is very hard to clarify the effect of vehicle dynamic motions on aerodynamic performance. In this study, simplified subscale car model was used to understand these effects on aerodynamic drag lift and flow characteristics. Less than 1% increase in drag was clarified under heave and pitch motions due to ones of main factors: pseudo change in angle of attack, Venturi effect under floor and change in lift induced drag by stronger negative pressure.

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