Use of a 3D compartment model for simplified full ship FE model. Part II: validation of the simplified FE model

This is Part II in a series of papers. Part I (J Mar Sci Technol 13:154–163) deals with an approach employed to construct a simplified FE model using a 3D compartment model available from the beginning of the ship design process. This paper begins by describing the limitations of an analytical approach based on shear warping beam theory for assessing torsional strength. Next, the structural parts of a container ship that have a negligible effect on hull girder bending strength and torsional strength are determined. This is verified by removing these parts from a conventional FE model and comparing the results obtained using this modified model with those yielded by the original model. The fore end part, the aft end part and the deck house are examined. Since these parts have complicated structures and relevant drawings for them are issued later than cargo structure drawings, modeling them exactly can result in a delay in the completion of the full ship FE model. This paper also verifies the validity of the simplified FE model built by applying the method proposed in Part I and comparing the results obtained with it with those given by a conventional full ship FE model. The stresses on hatch coaming top, the maximum diagonal elongations of the hatch coaming, and the maximum hatch corner movements are evaluated to check the validity of the simplified model.     

Numerical Study for Brake Squeal by Machining Patterns on Frictional Surface

Automotive brake noise has become a stubborn problem as automotive cars achieve higher driving torques, since that the increased torque induces the generation of severe noise dissipation during brake operation. Moreover, the global brake tuning market for achieving higher performance of the vehicle has expanded recently. The need to control the noise grows more in this connection. The tuning brake kits have employed cross-drilled and slotted machining pattern on the surface of the rotor. These designs have advantages to improve air ventilation, temperature control, and surface cleaning of brake pad. However, the effects of modal frequency by patterned rotor surfaces are rarely discussed, even if it is highly related with brake squeal phenomenon. Therefore, this study deals with the relationship between patterned surfaces and brake squeal through the numerical methods. The commercial software of a finite element analysis is employed for calculation by varying geometric design factors of each rotor pattern. As a result, the cross-drilled machining patterns are concluded to be an influential factor for in-plane mode frequency while the slotted patterns have more leverage for out-of-plane mode frequency.     

Measurement of soot oxidation with No<Subscript>2</Subscript>-O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO₂-O₂-H₂O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO₂-O₂ oxidation, which was 60±3 kJ/mol. When NO₂ exists with O₂ and H₂O, the reaction rate increases in proportion to NO₂. It increases nonlinearly with O₂ or H₂O concentration when the other two oxidants are fixed.     

Adaptation Strategy for Exhaust Gas Recirculation and Common Rail Pressure to Improve Transient Torque Response in Diesel Engines

Fuel injection limitation algorithms are widely used to reduce particulate matter (PM) emissions under transient states in diesel engines. However, the limited injection quantity leads to a decrease in the engine torque response under transient states. To overcome this issue, this study proposes an adaptation strategy for exhaust gas recirculation (EGR) and common rail pressure combined with a fuel injection limitation algorithm. The proposed control algorithm consists of three parts: fuel injection limitation, EGR adaptation, and rail pressure adaptation. The fuel injection quantity is limited by adjusting the exhaust burned gas rate, which is predicted based on various intake air states like air mass flow and EGR mass flow. The control algorithm for EGR and rail pressure was designed to manipulate the set-points of the EGR and rail pressure when the fuel injection limitation is activated. The EGR controller decreases the EGR gas flow rate to rapidly supply fresh air under transient states. The rail pressure controller increases the rail pressure set-point to generate a well-mixed air-fuel mixture, resulting in an enhancement in engine torque under transient states. The proposed adaptation strategy was validated through engine experiments. These experiments showed that PM emissions were reduced by up to 11.2 %, and the engine torque was enhanced by 5.4 % under transient states compared to the injection limitation strategy without adaptation.     

Accumulated tolerance analysis of suspension by geometric tolerances based on multibody elasto-kinematic analysis

Tolerance design of vehicle suspension is an important factor that affects the ride and handling quality and cost of the vehicle. Also, applying geometric tolerance to an analysis model is found to be a difficult process. This paper presents a method for tolerance analysis of wheel alignment of vehicle suspension. Monte-Carlo simulation method is applied to multibody elasto-kinematic model to analyze the accumulated geometric tolerances. As an example, Macpherson Strut Type front half car model is used, and wheel alignment dispersion and contribution ratio to the dispersion by accumulated geometric tolerances is computed. This paper also presents an efficient modeling and analysis method for elasto-kinematic model of vehicle suspensions by computing the stiffness matrix analytically. The simulation results of a Macpherson Strut Type demonstrates the validity and accuracy of the proposed method.     

Development of a backflow simulation program for automotive body assemblies

Most car body parts are manufactured using thin plates to reduce their weight, and completed assemblies typically have numerous spaces. Because cars are not designed to be completely watertight, rain or wash water may leak into the interior spaces of the assembly through gaps or inlets. When water enters a space and is not drained sufficiently, it can fill the space and overflow into unexpected channels, causing severe problems such as part corrosion and electric shock. In our research, based on a decomposition model representation, we have developed a program to graphically simulate all possible flows within the interior spaces between car parts. Our program can simulate the locations of outlets and overflow channels into unexpected regions, and thus help designers verify the effectiveness of their designs before manufacturing, which can therefore reduce the development time and costs. In particular, since the program can simulate overflow when a car in both horizontal and inclined positions, it can prevent possible design errors by engineers who are accustomed to designing cars only in a horizontal orientation. Our developed method can also be applied to aircraft and ship designs.     

Experimental investigation of wing-in-ground effect with a NACA6409 section

The aerodynamic characteristics of NACA6409 in the vicinity of the ground were experimentally studied in a wind tunnel. Lift and drag forces, the pitching moment, and the center of pressure were measured with respect to various major aerodynamic parameters, such as the ground clearance, the angle of attack, the aspect ratio (AR), and the endplate type, which resulted in a total number of 420 conditions. In addition, a smoke trace test was conducted to visualize the flow pattern around NACA6409 in the vicinity of the ground. As a result of the ground effect and the influence of the endplate, the lift-to-drag ratio increased at low ground clearance and the center of pressure moved forward to the leading edge; that is, the endplate and ground effects were equivalent to the aerodynamic advantage that results from increasing the AR of the wing. Extended experimental results are useful for understanding the aerodynamic characteristics influenced by each aerodynamic parameter during ground effect as well as for verifying numerical simulation.     

Simulation Study on Thermal Management Strategy to Achieve 99 % SCR Efficiency of a Heavy-Duty Diesel Engine over a Transient Cycle

In this study, NOx conversion characteristics of a urea selective catalytic reduction (SCR) system equipped on a heavy-duty diesel engine were evaluated through engine dynamometer bench tests over a scheduled world harmonized transient cycle (WHTC). Also, based on transient SCR simulations, the thermal management strategy to improve SCR NOx conversion efficiency was investigated. As a result, it was found that a selective increase in exhaust temperature at low temperature period would be a useful measure to increase SCR efficiency on WHTC mode. From the baseline SCR efficiency of around 98 % on WHTC mode, the current simulation results have shown that around 99 % level of SCR efficiency would be achievable by increasing exhaust temperatures with modifying diesel exhaust fluid (DEF) dosage. Another valuable contribution of this study is that the design guidelines for controlling exhaust temperature and DEF injection to obtain a target NOx conversion efficiency are presented for SCR systems of heavy-duty diesel engines on transient operating conditions.     

Enhancement of NOx-PM trade-off in a diesel engine adopting bio-ethanol and EGR

For realizing a premixed charge compression ignition (PCCI) engine, the effects of bio-ethanol blend oil and exhaust gas recirculation (EGR) on PM-NOx trade-off have been investigated in a single cylinder direct injection diesel engine with the compression ratio of 17.8. In the present experiment, the ethanol blend ratio and the EGR ratio were varied focusing on ignition delay, premixed combustion, diffusive combustion, smoke, NOx and the thermal efficiency. Very low levels of 1.5 [g/kWh] NOx and 0.02 [g/kWh] PM, which is close to the 2009 emission standards imposed on heavy duty diesel engines in Japan, were achieved without deterioration of the thermal efficiency in the PCCI engine operated with the 50% ethanol blend fuel and the EGR ratio of 0.2. It is found that this improvement can be achieved by formation of the premixed charge condition resulting from a longer ignition delay. A marked increase in ignition delay is due to blending ethanol with low cetane number and large latent heat, and due to lowering in-cylinder gas temperature on compression stroke based on the EGR. It is noticed that smoke can be reduced even by increasing the EGR ratio under a highly premixed condition.     

Operating strategy for gasoline/diesel dual-fuel premixed compression ignition in a light-duty diesel engine

Environmental problems have become a major issue for diesel engine development. Although emission aftertreatment systems such as DPFs (diesel particulate filters), LNTs (lean NOx traps) and SCR (selective catalytic reduction) have been used in diesel vehicles, the manufacturing cost increase caused by this equipment can be hard to be control. Thus, it is better for engine emissions to be reduced by improving the combustion system. A dual-fuel combustion concept is a recommended method to improve a combustion system and effectively reduce emissions. Low reactivity fuel including gasoline and natural gas, which was supplied to the intake port by the FPI (port fuel injector), improved the premixed air-fuel mixture conditions before ignition. Additionally, a small amount of high reactivity fuel, in this case diesel, was injected into the cylinder directly as an ignition source. This dual-fuel combustion promises lower levels of NOx (nitrogen oxide) and PM (particulate matter) emissions due to the elimination of local rich regions in the cylinder. However, it is challenging to control the dual-fuel combustion because the combustion stability and efficiency deteriorate due to the lack of ignition source and reactivity. Thus, it is important to establish an appropriate dual-fuel operating strategy to achieve stable, high efficiency and low emission operation. As a result of this research, a detailed operating method of dual-fuel PCI (premixed compression ignition) was introduced in detail at a low speed and low load condition by using a single cylinder diesel engine. Engine operating parameters including the gasoline ratio, a diesel injection strategy consisting of multiple injectors and timing, the EGR (exhaust gas recirculation) rate and the intake pressure were controlled to satisfy the low ISNOx (indicated specific NOx) and PM emissions levels (0.21 g/kWh and 0.1 FSN, 0.040 g/kWh, respectively) as per the EURO-6 regulation without any after-treatment systems. The results emphasized that a well-constructed dual-fuel PCI operating strategy showed low NOx and PM emissions and high GIE (gross indicated fuel conversion efficiency) with excellent combustion stability.