In Direct Injection Spark Ignition engines, it is important to understand the relationship between spray and in-cylinder flow and their effects on liquid film behavior, because fuel deposits in the cylinder wall cause harmful emissions and oil dilution. Therefore, in this study, we focused on spray wall impingement in a flow field and developed a simple wind tunnel apparatus to clarify the liquid film formation process applied with the Total Internal Reflection Laser Induced Fluorescence method. As a result, under the injection pressure of 20 MPa and cross flow velocities of 10 m/s and 20 m/s, the mass of the fuel liquid film increases compared to the stationary field condition due to the suppression of droplet splash on the wall. On the other hand, under the injection pressure of 20 MPa and cross flow velocities of 30 m/s and 40 m/s, the droplets are swept by the cross flow and do not reach the wall surface, and fuel liquid film mass decreases compared to that under the stationary field condition.

View full abstract

In a series of studies, we have proposed a combustion concept aimed at significantly reducing NOx emissions by stratifying water within the engine cylinder. In the first report, under conditions with an indicated mean effective pressure (IMEP) of 0.8 MPa, we demonstrated that when water injection was employed, NOx decreased to 1/4 level under equivalent soot concentration conditions compared to cases without water injection. In this second report, we evaluated engine performance under higher load conditions with an IMEP of 1.2 MPa. Utilizing 3D-CFD analysis, we found that stratifying water at the upper part of the piston cavity results in a 10-point higher reduction in NOx compared to homogeneously distributing water within the cylinder. While Exhaust Gas Recirculation (EGR) strategies pose challenges due to increased soot levels, our NOx reduction strategy using water injection showed a lesser increase in soot, leading to a higher reduction in NOx under equivalent soot concentration conditions. Subsequently, experiments were conducted using a multi-hole fan spray nozzle to achieve the layered distribution of water. The results demonstrated that, under conditions where the water injection quantity was 50% of the fuel amount, the optimization of timings and interval for split water injection led to approximately a 40% reduction in NOx under conditions of equivalent soot concentration. Furthermore, the impact on the heat release rate due to water injection was minimal, and the decrease in heat losses resulted in only a marginal decline of about 0.4 points in indicated thermal efficiency.

View full abstract

In order to chemically investigate the base fuel dependency of the ignition suppression effect of ethanol addition, shock-tube experiments and reaction simulation calculations were performed. Ignition delay measurements showed that the ignition suppression effect of ethanol was greatest for base fuels consisting only of paraffins, and this effect was weakened when 1-pentene and toluene were included. Computer simulations revealed that hydroperoxy radicals (HO₂) formed from ethanol abstracted hydrogen atoms at the allylic position of 1-pentene and at the benzylic position of toluene, resulting in an antagonistic effect on the ignition suppression of ethanol.

View full abstract

A diesel particulate filter (DPF) model that can be incorporated into a vehicle model developed with OpenModelica has been updated. In this report, A simplified turbocharger and diesel oxidation catalyst (DOC) model were developed and implemented into the exhaust system model of the vehicle model to predict the exhaust gas temperature behavior at the DPF inlet more accurately. By using the developed model, the effects of effective DPF regeneration methods on post injected fuel consumption were investigated.

View full abstract

Attempting to enhance lateral dynamics performance by integrated control of driving and braking forces might degrade the roll posture behavior. To overcome this issue, this study focuses on the response difference between On Board Motor System and Friction Brake System and proposes a frequency-separation based integrated driving and braking force control strategy. The proposed method achieves a 4 to 9 % reduction in the mean rear roll angle compared to the conventional control method.

View full abstract

We propose a method for measuring instantaneous structural intensity (SI) in flat structures using finite difference approximations. Based on flat plate theory, stress components associated with axial forces, bending moments, torsional moments, and shear forces are described in terms of vibration displacement. The derivation formulation is established by applying finite difference approximations to partial differential terms up to fourth order in both time and space. To achieve high temporal and spatial resolution, wave propagation after input is measured non-invasively using a Laser Doppler Vibrometer (LDV). This approach ensures precision and avoids contact-induced measurement errors. The proposed method demonstrated correlation with finite element method (FEM) simulations, confirming its validity and practicality for analyzing instantaneous SI.

View full abstract

The present study constitutes a preliminary investigation into the application of Dynamic Substructuring to the operation noise of Electric Power Steering. Experimental modelling of the gearbox, bushings, and the subframe has been conducted using several methods to predict the response of their assembly and to investigate the influence of measurement techniques on the modelling. The study has yielded successful predictions, thereby validating the approach. However, it has also exposed potential limitations, such as reproducibility of boundary conditions and spurious signals, particularly with regard to certain techniques.

View full abstract

This study conducted an experimental investigation of the actual range of use of mirrors to determine the range in which the view should be temporarily expanded in a CMS in UNR46. We conducted driving experiments for many situations in which head movement causes an expansion of the field of view. When checking surrounding vehicles, the range of the legal area of the Class Ⅲ mirrors in the left and right directions was about three times larger than that of the Class Ⅲ mirrors, which corresponds to about 1.5 times the range of the mirrors' field of view without head movement.

View full abstract

This study proposes a control system of vehicle trajectory tracking by calculating the steering angle using polynomial regression. To improve tracking stability, the evaluation function of the regression model incorporates suppression terms for steering angle velocity and acceleration, as well as an L2 regularization term. We compared our method with general model predictive control and demonstrated its effectiveness in reducing computation time and deriving practical tracking accuracy through computer simulations.

View full abstract