To improve the thermal efficiency of ICEs, effective control of in-cylinder temperature is important. Utilization of nucleate boiling phenomenon to model the heat transfer is one of the measures that can be used for this purpose. Surface heat flux and bubble departure frequency measurements were done under the different wall superheat, coolant flow-rate, and temperature conditions. Subsequently, dimensional analyses were done to investigate the necessary dimensionless numbers acting on the heat flux model. The addition of power and exponential function of Jakob number was found to be effective, resulting in an average and minimum errors of 11.2% and 6.5%, respectively.
A membrane filter was coated on conventional filter made of SiC. The first and second layers consisted of aluminaparticles with diameter of 0.5 and 1.5 micrometer, respectively; because small particles have higher filtration efficiency to prevent soot penetration into the membrane layer while large particles with a higher permeability can achieve lower pressure drop. Nanoscale silverpalladium particles were dispersedly deposited on the surface of the alumina particles layer as a top layer. The novel membrane filter demonstrated lower pressure drop while keeping high trapping efficiency during the soot trapping and presented lower soot oxidation temperature compared to the conventional filter.
The diesel engine commonly introduces high boost pressure to achieve high engine efficiency. This extra air is supposed to significantly influence liquid vaporization. In experiment, surrounding gas conditions of 7 – 46.8 kg/m3 were prepared by rapid compression and expansion machine RCEM. The nozzle hole length to diameter L/D ratio of 2.77, 3.73, 4.44 and 6.94 were used corresponding to orifice diameter of 0.072 – 0.180 mm. The close-up region from nozzle tip to 20 mm downstream was focused to simultaneously capture the vapor and liquid phases using shadowgraph and light scattering technique respectively. The information extracted from the images was then used for estimation of fuel mixture in the nearfield spray incorporated with a simple 1D jet model. The result showed that liquid length was dominated by both gas density including gas temperature and rate of fuel injection. The vapor cone angle showed tendency to increase with L/D ratio decreased. The widest vapor cone angle was found at L/D ratio of 2.77 which corresponded to achievement of the highest mass of fuel in vapor phase. It was an evidence that atomization is also one of the essential factors to improve vaporization. At the same gas temperature of 890 K, the fuel mass in liquid phase considerably reduced with increasing gas density. An increase in gas density resulted in substantially increase in entrainment. With identical orifice diameter of 0.180 mm, the smaller L/D=2.77 reported better atomization, shorten liquid length and enhanced entrainment compared with L/D=4.44.
The characteristic structure of the flow field in a torque converter is quantitatively evaluated using proper orthogonal decomposition (POD) under transient driving conditions assuming start-up acceleration and deceleration of a vehicle. The time-series velocity data inside the torque converter to be input to POD is measured using a particle image velocimetry (PIV) technique. At first, in the case of changing the rotational speed of the impeller or turbine, dynamic cascades with changing rotational speed were observed to induce fluid motion. The flow field structure was gradually reformed according to the speed ratio after transition. In addition, the region of structural changes of the flow field was found to be larger for the decelerating driving condition compared to the case of start-up acceleration.
Heavy-duty commercial vehicles (HDCVs) have specific characteristics different from passenger cars. This paper deals with one of the characteristics of HDCV, propagation delay by air of an air-brake system. It is related to the braking performance of the vehicle. Thus, it is necessary to reflect it appropriately in the control model. In this paper, we propose the model predictive braking controller with the model of HDCV, including the air-brake system. The effectiveness of the proposed method is demonstrated via numerical simulations with the full dynamics vehicle model and the realistic air-brake model.
To further reduce the aerodynamic drag of passenger vehicles, a deeper understanding of the flow field is required. Analysis methods like the dynamic mode decomposition (DMD) are useful to investigate unsteady flow phenomena around the vehicle. DMD results are only relevant for the aerodynamic development, if the used numerical data is able to predict the unsteady physical flow field. Therefore, in this study unsteady hot-wire data in the wake of a passenger vehicle is compared to a numerical dataset of an unsteady Spalart-Allmaras Delayed Detached Eddy simulation. Differences and wind tunnel effects are found and explained.
We developed an analytical method for the detection of nitric oxide (NO), nitrogen dioxides (NO2) and ozone (O3) simultaneously with high time resolution (1 s). The fast analytical method was applied for the observation at the Fuji mountain roadside at an altitude of 2300 m. We successfully observed the concentrations of NO and NO2 in emissions from each vehicle at a roadside, and the O3 concentration decreased due to the reaction with NO. Relative amounts of NOx emissions and primary NO2 emission ratios of each vehicle driven on the road were estimated by the concentrations observed with high time resolution.
Comparatively, this review is meant to focus on possible developments studies of the rotary engine design. The controversial engine produces a direct rotational motion. Felix Wankel derived the triangular rotor shape from complex geometry of the Reuleaux triangle. The Wankel engine simulation and prediction of its performance is still limited. The current work reviews rotary engine’s flow field inside the combustion chamber with different commercial software used. It studies different parameters effect on the performance of the engine, such as the effect of the recess sizes and the shape-factor. It is found that the engine chambers design is one of the aspects of improvement opportunities.