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This paper presents a free-form optimization method for achieving a desired stiffness in the shape design of automotive sheet metal structures. A squared error norm of displacements at loaded points is introduced as an objective functional in the formulation of a distributed-parameter shape identification problem. The shape gradient function theoretically derived for this problem is applied to the non-parametric free-form optimization method for shells that was developed by one of the authors. With this method, an optimal arbitrarily formed shell, or a shell with optimal curvature distribution can be obtained without any shape parameterization. The calculated results show the effectiveness and the practical utility of the proposed method for controlling stiffness when designing sheet metal structures.

In this paper, we present a parameter-free, or a node-based optimization method for finding the smooth optimal free-form of automotive shell structures, including global and local curvature distributions such as beads or embossed ribs. The design problems dealt with in this paper involve a stiffness problem. Stiffness is maximized using the compliance as an objective functional. The optimum design problem is formulated as a distributed-parameter, or non-parametric, shape optimization problem under the assumptions that the shell is varied in the normal direction to the surface and the thickness is constant. The shape gradient function and the optimality conditions are then theoretically derived. The optimum free-form, or optimal curvature distribution, is determined by applying the derived shape gradient function in the normal direction to the shell surface as pseudo external forces to vary the surface and to minimize the objective functional.

In this paper, we present a numerical solution to shape optimization problems in automotive shell structural designs subject to a strength constraint. Using the proposed method, the optimal shape can be obtained without any parameterization of design variables. With the aim of reducing the weight, a volume minimization problem subject to a von Mises stress constraint is formulated as a distributed-parameter shape optimization problem, or a non-parametric shape optimization problem. It is assumed that the design domain is varied in the tangential direction to the surface to maintain the curvatures of the initial shape. The shape gradient function and the optimality conditions are theoretically derived for this problem using the material derivative method, Lagrange multiplier method and the adjoint variable method. The traction method we have proposed earlier is applied to determine the smooth domain variation that minimizes the objective functional.

To reduce NOx and Particulate Matter (PM) emissions from a heavy-duty diesel engine, the effects of urea selective catalytic reduction (SCR) systems were studied. Proto type urea SCR system was composed of NO oxidation catalyst, SCR catalyst and ammonia (NH3) reduction catalyst. The NOx reduction performance of urea SCR system was improved by a new zeolite type catalyst and mixer for urea distribution at the steady state operating conditions. NOx and PM reduction performance of the urea SCR system with DPF was evaluated over JE05 mode of Japan. The NOx reduction efficiency of the urea SCR catalyst system was 72% at JE05 mode. The PM reduction efficiency of the urea SCR catalyst system with DPF was 93% at JE05 mode. Several kinds of un-regulated matters were detected including NH3 and N2O leak from the exhaust gas. It is necessary to have further study for detailed measurements for un-regulated emissions from urea solution.

A 2-LEG NOx Storage-Reduction (NSR) catalyst system is one of potential after-treatment technology to meet stringent NOx and PM emissions standards as Post New Long Term (Japanese 2009 regulation) and US'10. Concerning NOx reduction using NSR catalyst, a secondary fuel injection is necessary to make fuel-rich exhaust condition during the NOx reduction, and causes its fuel penalty. Since fuel injected in the high-temperature (∼250 degrees Celsius) exhaust instantly reacts with oxygen in common diesel exhaust, the proportion of fuel consumption to reduce the NOx stored on NSR catalyst is relatively small. A 2-LEG NSR catalyst system has the decreasing exhaust flow mechanism during NOx reduction, and the potential to improve the NOx reduction and fuel penalty. Therefore, this paper studies the 2-LEG NSR catalyst system. The after-treatment system consists of NSR catalysts, a secondary fuel injection system, flow controlled valves and a Catalyzed Diesel Particulate Filter (CDPF).

This paper presents a shape optimization method for the rigidity design of sheet metal structures under multiple loading conditions with the aim of weight reduction. In order to maintain the curvatures of the given initial shape, it is assumed that the design domain is varied in the in-plane direction. Using compliance as an index of the rigidity, a volume minimization problem subjected to multiple rigidity constraints is formulated as a non-parametric shape optimization problem. The shape gradient function and the optimality conditions are theoretically derived for this problem. The traction method is applied to determine the smooth in-plane domain variation that minimizes the objective functional. The calculated results of fundamental design examples and actual automotive chassis components will show the effectiveness and practical utility of the proposed method in solving shape optimization problems of sheet metal structures.

To reduce ultra fine particle number concentration from a heavy-duty diesel engine, the effects of diesel fuel property and after-treatment systems were studied. The reduction of ultra fine particle number concentration over steady state mode using an 8 liter turbocharged and after-cooled diesel engine was evaluated. PM size distribution was measured by a scanning mobility particle sizer (SMPS). The evaluation used a commercially available current diesel fuel (Sulfur Content: 0.0036 wt%), high sulfur diesel fuel (Sulfur Content: 0.046 wt%) and low sulfur diesel fuel (Sulfur Content: 0.007 wt%). The after-treatment systems were an oxidation catalyst, a wire-mesh type DPF (Diesel Particle Filter) and a wall-flow type catalyzed DPF. The results show that fine particle number concentration is reduced with a low sulfur fuel, an oxidation catalyst, a wire-mesh type DPF (Diesel Particulate Filter) and wall flow type catalyzed DPF, respectively.

To reduce emissions from diesel engines, the effects of oxidation catalysts on the emissions reductions were studied. The effectiveness of several oxidation catalysts on both the regulated and unregulated emissions was evaluated. The oxidation activity of the catalysts was varied by changing Pt loading. The regulated emissions include particulate (PM), hydrocarbon (HC), and carbon monoxide (CO), and the unregulated emissions include benzene, formaldehyde, acetaldehyde, and benzo[a]pyrene (B[a]P). An 8 litter, turbocharged and aftercooled diesel engine was operated under the Japan Diesel 13 (D13) mode cycle for the evaluations. As the first step, evaluations were conducted with a commercially available JIS #2 diesel fuel (0.046 wt% sulfur). All the regulated and unregulated emissions except PM were reduced as the Pt loading (i.e. oxidation activity) increased. However, PM emissions were increased by the generation of sulfate when the Pt loading exceeded 0.2 g/l.

This paper describes the combustion optimizations of heavy-duty diesel engines for the anticipated future emissions regulations by means of an electronically controlled common rail injection system. Tests were conducted on a turbocharged and aftercooled (TCA) prototype heavy-duty diesel engine. To improve both NOx-fuel consumption and NOx-PM trade-offs, fuel injection characteristics including injection timing, injection pressure, pilot injection quantity, and injection interval on emissions and engine performances were explored. Then intake swirl ratio and combustion chamber geometry were modified to optimize air-fuel mixing and to emphasize the pilot injection effects. Finally, for further NOx reductions, the potentials of the combined use of EGR and pilot injection were experimentally examined. The results showed that the NOx-fuel consumption trade-off is improved by an optimum swirl ratio and combustion chamber geometry as well as by a new pilot concept.

In this paper we present a numerical shape optimization method of continua for solving min-max problems and identification problems. The min-max shape optimization problems involve minimization of maximum stress or maximum displacement; the shape identification problems involve the determination of shapes that achieve a given desired stress distribution or displacement distribution. Each problem is formulated and sensitivity functions are derived using the Lagrangian multiplier method and the material derivative method. The traction method, which is a shape optimization method, is employed to find the optimal domain variation that reduces the objective functional. The proposed numerical analysis method makes it possible to design optimal structures for maximizing strength and rigidity and for controlling stress and displacement distributions. Examples of computed results are presented to show the validity and practical utility of the proposed method.

This paper presents a numerical analysis technique for application to shape optimization problems of linear elastic structures subject to multiple loading conditions. The problems dealt with here are a mean compliance minimization problem in relation to individual load cases and a fully stressed design problem. The proposed technique is based on the traction method which analyzes the domain variation. A shape optimization system was developed and applied to fundamental problems in two and three dimensions. The computed results confirmed the validity and usefulness of the proposed technique.

This paper describes the shape optimization analysis of solid structures such as chassis components of a car, where the shape optimization problems of linearly elastic structures are treated to improve strength or to reduce weight of solid structures. The optimization method used here is the growth-strain method, and the shape optimization system is developed based on this method. The growth-strain method, which modifies a shape by generating bulk strain, was previously proposed for analysis of the uniform-strength shape. The generation law of the bulk strain is given as a function of a distributed parameter to be uniformed, such as von Mises stress. Two improved generation laws are presented. The first law makes the distributed parameter uniform while controlling the structural volume to a target value. The second law makes the distributed parameter uniform while controlling the maximum value of the distributed parameter to a target value.

Diesel particulate trap systems are one of the effective means for the control of particulate emission from diesel vehicles. Hino has been researching and developing various diesel particulate trap systems for city buses. This paper describes two of the systems. One uses a wall flow filter equipped with an electric heater and a sensing device for particulate loading for the purpose of filter regeneration. Another makes use of a special filter named “Cross Flow Filter” with an epoch-making regeneration method called “Reverse Jet Cleaning”, by which it becomes possible to separate the part for particulate burning from the filter. Both systems roughly have come to satisfy the functions of trap systems for city buses, but their durability and reliability for city buses are not yet sufficient.

Future emission standards for heavy duty diesel engines will require extensive development using an integrated approach. This paper describes the latest results from HINO heavy duty diesel engine combustion research program. Improvement of the NOx/particulate/fuel economy trade off requires fuel injection equipment of Pump Line Nozzle (PLN) System and unit injector with high pressure capability, injection rate control and timing control, and a combustion system matched with high pressure injection. Combustion characteristics (ignition delay, combustion period, heat release curve), fuel consumption, particulate, and exhaust gas emission of each injection system are compared and discussed. The unit injector system has an advantage of lower particulate level, especially dry soot, than the Pump Line Nozzle system. The potential for further improvement through engine modification and aftertreatment is also discussed.

For the 1990's diesel engines, particulate control has been an important problem. The purpose of this paper is to discuss emission control needs for heavy duty diesel truck engines for the 1990's. This paper will focus on the factors such as fuel injection pressure and fuel properties which most affect particulate emission. The characteristics of diesel spray in the atmosphere and also actual combustion of a turbocharged and charge-cooled H.D. D.I diesel engine were studied as a function of injection pressure ranging from 50 to 150 MPa. Experimental results show that high pressure injection improves the atomization and air entrainment. Though Bosch smoke level, fuel consumption and combustion period decreased with the rise of injection pressure, particulate emission in EPA transient test cycle did not decrease dut to an increase of SOF.

The results of a systematic study on sources of particulate from direct injection diesel engine are presented. Particulates, divided between dry soot and soluble organic fraction were measured under a variety of steady state operating conditions from a D.I. diesel Engine. It was found that SOF (soluble organic fraction) was produced under light engine operation and dry soot was a function of engine load (increased with fuel flow rate). The soot formation and oxidation processes were studied by two methods: Direct photography and laser shadow-graphy.

A new combustion system for a light duty D. I. diesel engine was developed and introduced (1)*. The combustion chamber, which was used in the combustion system, has 4 concaves on the periphery of the inner wall and was calld HMMS-III. This combustion chamber realized better fuel consumption and lower smoke level over a wide speed range. However, the effects of HMMS-III combustion chamber on in-cylinder air motion and combustion characteristics were not yet clarified in the previous paper. In this study, in order to clarify the effects of HMMS-III combustion chamber on in-cylinder air motion and characteristics, analysis of flow direction and streak line via oil film method was carried out in comparison with flat dish and re-entrant type combustion chambers. Further, measurement of in-cylinder air motion by L.D.V. and observation of mixture formation and burning process via high speed schlieren photography were carried out.

A new combustion system for a light duty D.I. diesel engine was developed, and a 3.5 ton payload truck (6.5 ton G.V.W.) equipped with this D.I. diesel engine and this combustion system realized good fuel economy and lower exhaust gas emission. Generally, light duty vehicles have to operate over a wide engine speed range. Therefore application of a D.I. diesel engine to light duty vehicles is difficult because of combustion tuning requirements over a wide engine speed range. Up to now, most of the diesel engines for light vehicles have been of the I.D.I. type. But the D.I. diesel engine has an evident advantage of lower fuel consumption. In these circumstances the authors developed a new combustion chamber shape for a small D.I. diesel engine with turbulence induced intake port and optimum fuel injection equipment. Various combustion chamber geometries were tested and evaluated.

In a diesel engine, the mixing of the fuel spray and in-cylinder air controls rate of beat release during combustion, namely it will determine the thermal efficiency, maximum output and gas or noise emission, etc. Therefore, it is important to measure the droplet size and its volume density distribution in diesel fuel sprays. The optical measuring method, which includes a light scattering and holographic technique, seems the only feasible method for analysing these unsteady characteristics of fuel sprays. The light scattering technique described herein was based upon Mie scattering theory, and the droplet size and volume density distribution of fuel sprays were calculated from the combination of the light extinction and the forward-to-backscattering ratio of Mie scattering intensity. The volume density and droplet size distribution of fuel sprays were obtained from the light intensity distribution on a photograph of fuel sprays.