A 2-stroke gasoline engine may have an opportunity as a high efficiency engine in series hybrid with avoiding the low-load operation. Therefore, for the 2-stroke opposed piston engine that uses both SI operation and HCCI operation, we optimized the parameters that maximize the thermal efficiency using 1D-CFD and optimization software. Since the miller cycle is realized by using the EX crank delay and the dynamic effect of exhaust, knocking can be avoided even with a very high volume ratio (geometric compression ratio). Combined with the low cooling loss of the opposed piston engine, high thermal efficiency may be realized.
To achieve variable compression ratio, the multi-link system which has secondary merit as silence performance and low friction loss was selected. The multi-link system has the lever system which can amplify not only the load but also piston stroke. By using this characteristic, the main bearing load capacity was improved by the high rigidity crankshaft in spite of the amplified load. Simultaneously, by the arrangement of control shaft which is unique parts of multi-link system, the torque fluctuation was reduced. As a result, the size of multi-link system or engine was designed compactly.
We predicted the oil behavior around the piston ring in an automobile engine based on gas-liquid two-phase flow analysis and investigated the mechanism of oil consumption. The calculation results quantitatively revealed the pressure and the flow rate at various positions around the ring. The inflow oil increases the pressure at the bottom of the side rails and flows into the groove through the side clearance. The results are not affected by the grid size even when the inflow oil film thickness from the skirt is thin due to the level set method, which resolves the interface sharply. The maximum oil film thickness is similar to the case where the oil velocity is the maximum by inertia force due to increased oil volume.
The authors were studying micro groove bearing using the copper-lead alloy that was used at the time of development, so report the results of the study. Ｗear test on engine test bench reveals optimal ratio of width to groove depth for micro groove bearing. The friction loss torque of properly designed micro groove bearings is slightly reduced compared to natural plain bearings. Authors thought that the upper limit of oil clearance could be reduced by that amount. Properly designed micro groove bearing endurance test showed no seizure or fatigue, and good wear results were obtained. The optimum groove size for micro groove bearings are groove depth of 2.5-4.5μｍ and groove width of 0.15-0.25mm.
In this study, we developed a technology that can detect multi-hydrocarbon component in a wide range of 100nm with 3μm high-speed scanning laser system based on difference frequency generation method lasers and tunable diode laser absorption spectroscopy (TDLAS). The applicability of simultaneous multi-hydrocarbon components measurement technology in the engine process was evaluated. TDLAS with 3μm high-speed scanning laser system is capable of mixture measuring and has the potential for practical application.
The knocking phenomenon at the time of auto-ignition can be examined in detail using the pressure transport equation. In particular, it has been clarified that the expansion effect suppresses the pressure increasing. In this study, effective applications of the expansion effect based on the acoustic energy equation derived from transport equations is discussed. And the knock suppression theory is verified using numerical simulations and the results show that knock intensity can be reduced. Finally, it is shown that the knock intensity has a similarity rule to acoustic Damkohler Number.
In this study, the compact PAH growth model previously presented by authors was combined with a reduced gas-phase reaction model for toluene reference fuel and ethanol proposed by Sakai and Miyoshi. The present model, PS3SMr2, consists of 107 chemical species and 473 elemental reactions. This model well reproduces the ignition delay time and the laminar flame speed of iso-octane, n-heptane, toluene and ethanol air mixtures as well as the base model. Verifications of soot formation characteristics were first performed for the experimental results for a gasoline surrogate fuel measured by shock tube. As a result, it was shown that the model can well reproduce sooting characteristics regardless of the pressure and the amount of oxygen. The ethanol blend effect to the test fuel on the soot emissions was verified on the simulated in-cylinder pool combustion experiments for iso-octane/toluene/ethanol blended fuels. As a result, we showed that the present model shows a good reproducibility of the qualitative trend of soot emissions with the change in the equivalence ratio for a gasoline surrogate fuel as well as existing model results. As for the effect of ethanol blend, it was shown that the experiments were well reproduced when toluene was replaced and that there was room for improvement when iso-octane was substituted.
In this study, we considered a method for clarifying main factors increasing vehicle interior noise using operational transfer path analysis (TPA) principal component model (PCCA: principal component contribution analysis). Through an experiment using simple vehicle physical scale model at an operational condition, the main factors (acoustic resonance in cabin, vibration resonance of body or vibration resonance of flame) were estimated by evaluating the elements of repeated PCCA results and the verification was carried out through the countermeasure for the reduction of the interior noise.
It is necessary to consider driver’s behavioral change in an integrated method to detect abnormal physical condition while driving because various symptoms occur due to the disease. In this paper, we analyzed the characteristics of gaze behavior with respect to driving scenery for higher brain dysfunction, and clarified differences in gaze behavior between attention-impaired patients and controls. In addition, we evaluated the robustness of the method of detecting abnormal signs from gaze behavior in actual vehicles and environments.
An available path planning is required for a vehicle turning control to pass through any target point. It is well known that a vehicle driving trajectory is well coincided with a clothoid curve when the steering wheel was turned with constant speed. However, a real-time planning without trial and error of a clothoid curve that pass through the target point has not been much reported. This paper investigated a real-time path planning using the characteristics of both a clothoid curve and turning trajectory. The experimental results showed that the vehicle well passed through any target point.
In this study, the authors have newly developed a droplet evaporation model for multi-component fuels, which uses the distillation curve, density and type of hydrocarbons as input data. The model is well validated against evaporation rates measured at various ambient temperatures and pressures. Distillation curve and density are known as variables for calculating cetane index. Using the proposed model, we investigated the effect of distillation curves and densities on evaporation characteristics. The results show that the evaporation rate coefficients and droplet life times of liquid fuels, which have a close correlation with the distillation curves, correlate poorly with the cetane indices.
Increasing the thermal efficiency of internal combustion engines is critical to reducing CO2 emissions from the transportation sector. Using particular engine technologies in combination with special fuel technology, we have been able to increase thermal efficiency substantially. In previous studies, we reported that the use of a super lean burn (combustion with an excess air ratio of 2.0 or higher) and certain fuel compositions, formulated with oxygen- and nitrogen-containing compounds such as furans and nitromethane, extended the combustion limit (lean limit) and improved thermal efficiency. In this current study, we report on our finding that the lean limit can be extended substantially through use of certain hydrocarbon fuels whose compositions include no oxygen or nitrogen.
In order to achieve ultra-highly boosted downsizing concept, 2 stage turbocharging system was studied to obtain a positive pumping work for better brake efficiency from low to high engine speed at ultra-highly boosted range. The prototype system was made and tested. The concept of this study and experimental results are described.
In order to make clear the oil consumption mechanism of automobile engines, theoretical calculation formulae were proposed for the oil and gas flow in the narrow clearance just under the lower rail of an oil control ring (OCR). Formulae were also proposed for the vertical oil flow on piston lands or on wall in an OCR groove, and for the inflow from the bottom of the OCR groove into drain holes, both of which are induced under the inertia force. Most of them were verified by flow visualization using a test rig, an operating engine, or by the CFD analysis.
A high-accuracy knocking prediction model with low computation loads is necessary for the efficient development of SI engines using engine performance simulators. In the first report, the scientific nature of autoignition prediction using the Livengood-Wu integral was investigated. In the second report, ignition delay time equations for a premium-gasoline surrogate fuel were developed, which can reproduce the temperature-, pressure-, and equivalence ratio-dependences of ignition delay time produced using a detailed reaction mechanism. In the third report, error factors in in-cylinder autoignition prediction using the Livengood-Wu integral with the ignition delay time equations were investigated. In the fourth report, an error correction equation was developed, which can cancel the errors of timing predicted using the Livengood-Wu integral from ignition timing. An autoignition prediction model using “reverse Livengood-Wu integral” with the ignition delay time and error correction equations was proposed. In the present report, the ignition delay time equations have been improved to reproduce the EGR-dependence of ignition delay time.
To correspond to system voltage 800 V for electric vehicle which is higher than conventional 400 V, with high power density, we developed inverter with components which had high voltage insulation design and with stable parallel operation of power modules for high powering. Especially, double-sided direct water cooling power module as a key component of inverter was developed with techniques of the low inductance terminal structure and the conductor laminated insulation sheet which achieved insulation performance for 800 V system without increasing thermal resistance. The inverter including these technologies achieved maximum power density 94 kVA / L and corresponded to system voltage 800 V.
We propose the RT-Mover PType WA Mk-II(P-WA), which is a personal mobility vehicle that can be transformed mutually between front/rear steering mode and differential wheeled mode. The advantage of P-WA in front/rear steering mode is that it can move on rough terrain stably. However, when we consider the issue of “limited steering angle”, the turning performance in this mode will be unsatisfactory. Therefore, we developed a switching algorithm of P-WA. It can optimize the steering performance by changing between front/rear steering mode and differential wheel mode. We have evaluated the developed switching algorithm and differential wheel mode through experiments.
In order to reduce weight of steel doors, lightweight steel doors with FRP stiffening member was developed. The FRP stiffening member was designed by topology optimization. The FRP stiffening member was fabricated and installed inside the outer panel. Panel stiffness tests were carried out. As a results, when the thickness of the outer panel was 0.5mm, the panel stiffness were remarkably reduced compared with the thickness of 0.6mm. On the other hand, the outer panel in the thickness of 0.5mm with FRP stiffening member achieved 12% reduction in weight and 244% improvement in panel stiffness at the weakest point.
This report describes a road projection lamp in conjunction with a turn signal lamp (color: amber, blinking frequency: 1Hz) to reduce traffic accidents involving collisions with cyclists and pedestrians. Specifically, we highlight the required luminance contrast that is necessary for; 1) pedestrians in the vicinity of a car; 2) cyclists ability to detect the road projection on the road. Experiments were conducted from low-level daylight to nighttime. In addition, we also carried out glare evaluation of the road projection lamp that can be detected in the dark condition of night. When the irradiation distance from the lamp is 3 m, at a mounted height of 0.7 m and the lamp luminous intensity is 6,350 cd or more, road projection can be detected at an ambient illuminance of 800 lx or less. Also glare light at a lamp intensity of 10,300 cd is not a problem.
The proposition of this research is to understand whether it is possible to estimate the CE of the statistical model from the surrounding sensor data. The viewpoint of verification is used by time difference of time series data. For using engine data, it was according to the speed of the vehicle and an auto correlation function calculated with shifting the time difference and making a statistical model. This modeling is based on engine running data with WLTC (Worldwide-harmonized Light vehicles Test Cycle). However, no previous research would give us the detail information about type of data. This type had training data which might contribute to make accuracy better. Accordingly, we tried to improve the estimation accuracy, it depends on the choice of Max Time Lag in order to establish. Moreover, Gibbs phenomenon might be happen by Lag settings. In this study, GP which is widely way as a statistical model for the estimation of in-cylinder intake air.