Search Results

An operational scheme with fuel-lean and exhaust gas dilution in spark-ignited engines increases thermal efficiency and decreases NOx emission, while these operations inherently induce combustion instability and thus large cycle-to-cycle variation in engine. In order to stabilize combustion variations, the development of an advanced ignition system is becoming critical. To quantify the impact of spark-ignition discharge, ignitability tests were conducted in an optically accessible combustion vessel to characterize the flame kernel development of lean methane-air mixture with CO₂ simulating exhaust diluent. A shrouded fan was used to generate turbulence in the vicinity of J-gap spark plug and a Variable Output Ignition System (VOIS) capable of producing a varied set of spark discharge patterns was developed and used as an ignition source. The main feature of the VOIS is to vary the secondary current during glow discharge including naturally decaying and truncated with multiple strikes.

One of the world's largest unsteady turbulence simulations of flow around a formula car was conducted using Large Eddy Simulation (LES) on the Earth Simulator in Japan. The main objective of our study is to investigate the validity of LES for the assessment of vehicle aerodynamics, as an alternative to a conventional wind tunnel measurement or the Reynolds Averaged Navier-Stokes (RANS) simulation. The aerodynamic forces estimated by LES show good agreement with the wind tunnel data (within several percent!) and various unsteady flow features around the car is visualized, which clearly indicate the effectiveness of large-scale LES in the very near future for the computation of flow around vehicles with complex configurations.

A benchmark study was conducted to assess the capability of an open source CFD based process to accurately simulate the physics of the flow field around various vehicle types. The ICON FOAMpro process was used to simulate the flow field of four baseline geometries of a Truck, CD-Car, B-Car and an SUV. Further studies were carried out to assess the effects of geometry variations on the predicted aerodynamic lift and drag. A Detached-Eddy Simulation (DES) approach was chosen for the benchmarks. In addition to aerodynamic lift and drag values, the results for surface pressure data, surface and wake flow fields were calculated. These results were compared with values obtained using Ford's existing CFD processes.

Multidimensional computations were carried out to simulate the in-cylinder fuel/air mixing process of a direct-injection spark-ignition engine using a modified version of the KIVA-3 code. A hollow cone spray was modeled using a Lagrangian stochastic approach with an empirical initial atomization treatment which is based on experimental data. Improved Spalding-type evaporation and drag models were used to calculate drop vaporization and drop dynamic drag. Spray/wall impingement hydrodynamics was accounted for by using a phenomenological model. Intake flows were computed using a simple approach in which a prescribed velocity profile is specified at the two intake valve openings. This allowed three intake flow patterns, namely, swirl, tumble and non-tumble, to be considered. It was shown that fuel vaporization was completed at the end of compression stroke with early injection timing under the chosen engine operating conditions.

In 1999, some Japanese fuel suppliers sold highly concentrated alcohol fuels, which are mixtures of gasoline and oxygenates, such as alcohol or ether, in amounts of 50% or more. In August 2001, it was reported that some vehicle models using the highly concentrated alcohol fuels encountered fuel leakage and vehicle fires due to corrosion of the aluminum used for the fuel-system parts. The Ministry of Economy, Trade and Industry (METI) and the Ministry of Land, Infrastructure and Transport Government of Japan (MLIT) jointly established the committee on safety for highly concentrated alcohol fuels in September 2001. The committee consisted of automotive technology and metal corrosion experts knowledgeable about preventing such accidents and ensuring user safety. Immersion tests were conducted on metals and other materials used for the fuel-supply system parts to determine the corrosion resistance to each alcohol component contained in the highly concentrated alcohol fuels.

Some problems, what values of aerodynamic characteristics are appropriate for ensuring or increasing stability and controllability at high speed running, specially in view of both lane-keeping at the running condition and cross-wind characteristics, are discussed at this paper, based on some hypotheses and experimental data. Through the discussion, some fundamental items or facts are proved to be made clear for considering the problems.

One of the passive methods to reduce drag on the unshielded underbody of a passenger road vehicle is to use a vertical deflectors commonly called air dams or chin spoilers. These deflectors reduce the flow rate through the non-streamlined underbody and thus reduce the drag caused by underbody components protruding in to the high speed underbody flow. Air dams or chin spoilers have traditionally been manufactured from hard plastics which could break upon impact with a curb or any solid object on the road. To alleviate this failure mode vehicle manufacturers are resorting to using soft plastics which deflect and deform under aerodynamic loading or when hit against a solid object without breaking in most cases. This report is on predicting the deflection of soft chin spoiler under aerodynamic loads. The aerodynamic loads deflect the chin spoiler and the deflected chin spoiler changes the fluid pressure field resulting in a drag change.

A twofold improvement in penetration resistance of laminated safety glass for use in vehicle windshields has been achieved. A new test procedure has been established which will provide better correlation of test conditions to accident conditions than present tests do. Present windshield material and the new safety glazings are compared.

It is becoming more and more necessary to achieve a sustainable low-carbon society by mobility not depending on oil. Electric vehicles are appropriate for such a society, but expensive battery cost and long charging time prohibit the promotion of EVs. One of the solutions is minimizing battery usage by ultra-low fuel efficiency, so we developed an ultrahigh-efficient electric commuter concept car “C-ta”, which requires as small a battery as possible. We assumed that drivers would use the car as a second car for short-distance daily use, such as commuting, shopping, transportation of family, etc. In order to improve fuel efficiency, we mainly considered an ultra-light weight body and chassis, to which CFRP (carbon fiber reinforced plastic) greatly contributes, ultra-low rolling resistance tires, and highly accurate vehicle control technology with four in-wheel motors.

A numerical method specially designed to predict unsteady aerodynamics of road vehicle was developed based on unstructured Large-Eddy Simulation (LES) technique. The code was intensively optimized for the Earth Simulator in Japan to deal with the excessive computational resources required for LES, and could treat numerical meshes of up to around 120 million elements. Moving boundary methods such as the Arbitrary Lagrangian-Eulerian (ALE) or the sliding method were implemented to handle dynamic motion of a vehicle body during aerodynamic assessment. The method can also model a gusty crosswind condition. The method was applied to three cases in which unsteady aerodynamics are expected to be crucial.