Search Results

A mixed time-scale subgrid large eddy simulation was used to simulate mixture formation, combustion and soot formation under the influence of turbulence during diesel engine combustion. To account for the effects of engine wall heat transfer on combustion, the KIVA code's standard wall model was replaced to accommodate more realistic boundary conditions. This were carried out by implementing the non-isothermal wall model of Angelberger et al. with modifications and incorporating the log law from Pope's method to account for the wall surface roughness. Soot and NOx emissions predicted with the new model are compared to experimental data acquired under various EGR conditions.

Reduction of transmission error by gear tooth profile optimization and tuning of gear resonance modes are known as effective methods for gear noise reduction. This paper concentrates on structuring a process for reducing gear noise using the latter method. The procedure comprises a study of gear noise mechanism from transmission error to radiation noise, an application of Steyer's method in gear frequency analysis and implementation of an invented device called “noise reduction ring”. This inexpensive and practical ring reduces gear noise drastically by 10dB, which is predicted by the simulation and verified by the experiment.

We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Atenza / Mazda6, Demio / Mazda2, RX-8 employs the module carriers using this material, resulting in dramatic weight and cost savings. (Fig. 1)

The newly developed rotary engine has achieved major progress in high performance, improved fuel economy and clean exhaust gas by innovative action. The engine of the next generation is named RENESIS, which stands for “The RE (Rotary Engine)'s GENESIS” or the rotary engine for the new millennium. The peripheral exhaust port of the previous rotary engine is replaced by a side exhaust port system in the RENESIS. This allows for an increase in the intake port area, thus producing higher power. Exhaust opening timing is retarded to improve thermal efficiency. The side exhaust port also allows reducing the internal EGR, stabilizing the combustion at idling. The improved thermal efficiency and the stabilized idle combustion result in higher fuel economy. In addition, the side exhaust port allows a reduction of the HC mass, realizing reduced exhaust gas emission.

We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Mazda 6 employ the module carriers using this material, resulting in dramatic weight and cost savings.

Thixomolding® produces net-shape parts from Magnesium alloys in a single step process involving high speed injection molding of semi-solid thixotropic alloys. A description of the process and status of commercial developments will be presented.. The mechanical properties and microstructures of Thixomolded® AZ-91D magnesium materials will be presented. Tensile strengths of semi-solid AZ-91D at both room temperature and elevated temperatures ( 373K, 423K) are compared with die cast AZ-91D. Data on enhanced creep properties of Thixomolded® AZ91-D alloy relative to die cast AZ-91D will be examined with respect to relative changes in microstructural features. Controlling the percent solids in the semi-solid state prior to injection molding can lead to improved creep performance for use in net-shape automotive components.

On-road turbulences caused by sources such as atmospheric wind and other vehicles influence the flow field and increases the drag in a vehicle. In this study, we focused on a scenario involving a passing vehicle and investigated its effect on the physical mechanism of the drag increase in order to establish a technique for reducing this drag. Firstly, we conducted on-road measurements of two sedan-type vehicles passed by a truck. Their aerodynamic drag estimated from the base pressure measurements showed different increment when passed by the truck. This result raised the possibility of reducing the drag increase by a modification of the local geometry. Then, we conducted wind tunnel measurements of a simplified one-fifth scale vehicle model in quasi-steady state, in order to understand the flow mechanism of the drag increase systematically.

The quest to simulate noise problems has led to the building of larger and more detailed finite element models in order to perform vibration solutions to higher frequencies. This leads to the building of solid finite element models of complex geometries, such as castings, which might previously have contained less detail or even been built with shell elements. Unfortunately, detailed geometric representations used to build models do not always agree with as built parts and lead to discrepancies between analysis results and test data. This paper presents an approach that reduces the time and cost necessary to identify these differences.

Driver fatality rate of a passenger vehicle is considerably high when struck on the side by an LTV (light truck and van). Aggressivity of LTVs, particularly in side crashes, needs to be reduced to improve this incompatible situation. Crash energy absorption share of a passenger car struck on the side by an LTV was measured through component tests. As a result, B-pillar of the struck passenger car was found to receive most of the crash energy intensively. This intensive energy triggered large B-pillar deformation. Computer simulation proved that B-pillar deformation was closely related to occupant injury. The key to mitigate the injury of side-struck car occupant, therefore, is to disperse crash energy to other structural parts than B-pillar. Front-end structures of LTVs that realize crash energy dispersion were designed and examined. The structures include (a) optimization of the vehicle height, and (b) adoption of a forward-extended sub-frame.

Conventionally, the effort of gear whine reduction has focused on minimizing the transmission error generated in automobile transmission. In mean time, as demands on gear whine reduction increased, the need of controlling noise transfer path was arisen because transmission error turns into interior noise in those paths [1-2]. In this paper, we provide experimental technologies to clarify the noise transfer path which dominants high frequency gear whine from experimental point of view.

Some of the frequencies of transmission gear whine noise reach up to several kHz. High-frequency gear whine noise is mostly transmitted by air (airborne); therefore, it is critical to reduce transmission radiation noise. This paper presents how to solve the problem of high-frequency noise in the range of 2.0 - 4.1kHz by experiment using Inverse Boundary Element Method (IBEM) and by computer simulation using Boundary Element Method (BEM).

The thermal efficiency of a three-rotor rotary engine (RE) was improved by a reduction in the pumping losses. These pumping losses were reduced by using a new port mechanism. The port mechanism utilized was an indirect recirculation type of late intake port closing. It was equipped with a recirculation chamber outside of the housings. This chamber interconnected the recirculation ports within each housing. This port mechanism yielded three main benefits 1. A Considerable reduction in the pumping losses. 2. A uniformly distributed air-fuel mixture in each housing. 3. A limited amount of residual gas in the housing. This residual gas was under specific pulsations by the recirculation chamber thus preventing deterioration in combustion under light loads. The above phenomena were clarified by experiments and simulations. The possibility of a reduction in exhaust emissions was also investigated.

In order to secure effective occupant protection at vehicle collisions, it is necessary to conduct close examination into vehicle crash characteristics as well as interior parts, etc. This paper analyzes the behavior of a HYBRID III dummy restrained by three point seatbelt using MVMA2D computer simulation program at a 35 mph vehicle frontal barrier crash. As a result, it is found for good agreement between experiment and simulation that the exact input data of successive toeboard intrusion play an important role. As for the parametric study on vehicle crashworthiness, the authors propose the convenient method to represent the actual crash pulse by two simplified trapezoids. Then using these trapezoids, the parametric study clarifies the influence of vehicle deformation characteristics as well as the interior parts on dummy injury.

The reduced chemical reaction scheme which can take the effect of major fuel components on auto ignition timing into account has been developed. This reaction scheme was based on the reduced reaction mechanism for the primary reference fuels (PRF) proposed by Tsurushima [1] with 33 species and 38 reactions. Some pre-exponential factors were modified by using Particle Swarm Optimization to match the ignition delay time versus reciprocal temperature which was calculated by the detailed scheme with 2,301 species and 11,116 elementary chemical reactions. The result using the present reaction scheme shows good agreements with that using the detailed scheme for the effects of EGR, fuel components, and radical species on the ignition timing under homogeneous charge compression ignition combustion (HCCI) conditions.

The combustion process, emission formation and the resulting engine performance in a diesel engine are well known to be governed mainly by spray behaviors and the consequent mixture formation quality. One of the most important factors that affect the spray development is the nozzle configuration. Originally, single-hole diesel injector is usually applied in fundamental research to provide insights into the spray characteristics. However, the spray emerging from a realistic multi-hole injector approaches the practical engine operation situation better. Meanwhile, previous research has shown that the reduced nozzle hole diameter is effective for preparing more uniform mixture. In the current paper, a study about the effects of nozzle configuration and hole diameter on the internal flow and spray properties was conducted in conjunction with a series of experimental and computational methods.