Investigation on Spray Behavior and NOx Conversion Characteristic of a Secondary Injector for a Lean NOx Trap Catalyst

Lean NOx trap (LNT) catalyst has been used to reduce NOx emissions from diesel engines. The LNT absorbs NOx in lean condition and discharges N2 by reducing NOx in rich conditions. Thus, it is necessary to make exhaust gas lean or rich conditions for controlling LNT system. For making a rich condition, a secondary injector was adopted to inject a diesel fuel into the exhaust pipe. In the case of secondary injector, the behavior of spray is easily affected by high temperature (i.e., 250 ～ 350 °C) occurred in the exhaust manifold. Therefore, it is needed to investigate the spray behavior of diesel fuel injected into an exhaust manifold, as well as the conversion characteristics for a lean NOx trap of a diesel engine with LNT catalyst. The characteristics of exhaust emissions in NEDC (New European Driving Cycle) mode were analyzed and spray behaviors were visualized in various exhaust gas conditions. The results show that as the exhaust gas mass flow increases, the spray cone angle becomes broad and the fuel is directed to the flow field. Besides, the cone angle of spray is decreased by centrifugal force caused in exhaust gas flow field. In addition, the effects of nozzle installation degree, injection quantity, and exhaust gas flow on NOx conversion performance were clarified.     

System power loss optimization of electric vehicle driven by front and rear induction motors

Power loss optimization aiming at the high-efficiency drive of front-and-rear-induction-motor-drive electric vehicle (FRIMDEV) as an effective way to improve energy efficiency and extend driving range is of high importance. Different from the traditional look-up table method of motor efficiency, power loss optimization of the dual- motor system based on the loss mechanism of induction motor (IM) is proposed. First of all, based on the power loss characteristic of FRIMDEV from battery to wheels, the torque distribution optimization model aiming at the minimum system power loss is put forward. Secondly, referring to d-q axis equivalent model of IM, the power loss functions of the dual-IM system are modeled. Then, the optimal torque distribution coefficient (β _o) between the two IMs is derived, and the theoretical switching condition (T _sw) between the single- and dual-motor-drive mode (SMDM and DMDM) is confirmed. Finally, a dual-motor test platform is developed. The derived torque distribution strategy is verified. The influence of motor temperature on β _o and T _sw are tested, and the correction models based on temperature difference are proposed. Based on the system power loss analysis, it can be confirmed that, under low load conditions, the SMDM takes priority over the DMDM, and the controller of the idling motor should be shut down to avoid the additional excitation loss. While under middle to high load conditions, even torque distribution (β _o = 0.5) is preferred if the temperature difference between the two IMs is small; otherwise, β _o should be corrected based on dual-motor temperatures. The theoretical T _sw derived without dealing with temperature difference is a function only of motor speed, while temperature difference correction of it should be conducted in actual operations based on motor resistance changing with temperature.     

Design Optimization of the Cowl Cross Bar - Light Cowl Cross Bar Satisfying 5 Performances -

Nowadays, more lightweight designs is the key goal of all major automotive industries. One of the main sections for more lightweight automotive area is the Cowl cross bar (CCB) assemblies. A cowl cross bar supports a steering system, airbag module, audio, instrument panel and air conditioning system. The CCB integrates these components into the cockpit module and connects to the body. So the CCB must meet the 5 performance requirements, ① NVH requirement to minimize the vibration, ② Crash performance for less deflection, ③ Steering response requirement for steer predictability, ④ Durability performance like the fatigue life and ⑤ Supporting rigidity for the components. In this study, a new methodology for the optimum CCB design is proposed to obtain a more lightweight design considering 5 targeted requirements. At first, for NVH and Steering response performance, 3-steps of optimization was fulfilled in sequence of (1) Size optimization and mounting position, (2) Case studies about the various types of brackets and (3) Shape optimization using the topology. The proposed design and optimization framework was verified whether it could meet the crash, durability and stiffness requirements. The final optimal CCB would be applied to the new platforms of the Hyundai-Kia motors.     

Spatter rate estimation of GMAW-S based on partial least square regression

This paper analyzes the drop transfer process in gas metal arc welding in short-circuit transfer mode （GMAW-S） in order to develop an optimized spatter rate model that can be used on line. According to thermodynamic characters and practical behavior, a complete arcing process is divided into three sub-processes： arc re-ignition, energy output and shorting preparation. Shorting process is then divided as drop spread, bridge sustention and bridge destabilization. Nine process variables and their distribution are analyzed based on welding experiments with high-speed photos and synchronous current and voltage signals. Method of variation coefficient is used to reflect process consistency and to design characteristic parameters. Partial least square regression （PLSR） is utilized to set up spatter rate model because of severe correlativity among the above characteristic parameters. PLSR is a new multivariate statistical analysis method, in which regression modeling, data simplification and relativity analysis are included in a single algorithm. Experiment results show that the regression equation based on PLSR is effective for on-line predicting spatter rate of its corresponding welding condition.     

Relationship between quality and attributes of elliptical spot welds of high strength steel

More high strength steel(HSS) sheets are being applied in the automobile industry to improve safety and fuel efficiency.When HSS is spot welded, the strength of the welded-joint is usually determined by the attributes of the weld nugget.However, it is diffcult to obtain the circular nugget and to establish the relationship between the weld attributes and welding quality because of a large number of variables and experimental uncertainty.In the paper, the numerical analysis model of tensile-shear strength test for HSS spot welds was established.And the critical ellipticity of the elliptical spot weld was determined through finite element analysis.Quantitative relationship between elliptical weld attributes and weld strength was investigated statistically using the Latin hypercube and regression analysis method.The sheet thickness, nugget ellipticity, hardness radio and yield strength have the most influential attributes in affecting welding quality.The research results can be used as a guideline for HSS resistance spot welding design.     

A new black box analysis of hash functions based on block ciphers

For the 64 most basic ways to construct a hash function H:{0,1} → {0,1}n from a block cipher E:{0,1}n × {0,1}n → {0,1}n, Black et al.provided a formal and quantitative treatment of the 64 constructions, and proved that 20 schemes are collision resistant.This paper improves the upper and lower bounds and make contrast with a hash constructed from a random oracle.These 20 schemes have only one kind of collision resistance upper and lower bounds.In addition, we present new advantages for finding second preimages.     

Simulation of Chaos in Asymmetric Nonlinear Chua＇s Circuit

In order to describe practical chaotic systems exactly, we presented a simple modified Chua's circuit,which contains an asymmetric nonlinear resistive element. Mathematical analysis was made, and simulation study was performed by MATLAB. By varying the value of linear resistor in the circuit, rich variety dynamical behaviors were observed, such as DC equilibrium point, Hopf bifurcation, period-doubling bifurcation,single-scroll strange attractor, periodic windows, and asymmetric double-scroll strange attractor. The extreme sensitivity in the state trajectory with respect to the initial conditions was exhibited; the special characteristic of asymmetric nonlinear Chua's circuit was found also.     

A new method of transmission network flexible planning using the connection number

Because connection number can express and process synthetic uncertainties caused by various uncertainties in the transmission network planning, a connection number model (CNM) was presented to compare the values of connection number logically. This paper proposed a novel model for transmission network flexible planning with uncertainty. In the proposed planning model both certainty and uncertainty information were included, and the cost-benefit analysis method was used to evaluate the candidate schemes in the objective function. Its good adaptability and flexibility were illustrated through two examples.     

Distribution system optimization planning based on plant growth simulation algorithm

An approach for the integrated optimization of the construction/expansion capacity of high-voltage/medium-voltage (HV/MV) substations and the configuration of MV radial distribution network was presented using plant growth simulation algorithm (PGSA). In the optimization process, fixed costs correspondent to the investment in lines and substations and the variable costs associated to the operation of the system were considered under the constraints of branch capacity, substation capacity and bus voltage. The optimization variables considerably reduce the dimension of variables and speed up the process of optimizing. The effectiveness of the proposed approach was tested by a distribution system planning.     

A modified genetic algorithm for product family optimization with platform specified by information theoretical approach

Many existing product family design methods assume a given platform, However, it is not an in-tuitive task to select the platform and unique variable within a product family. Meanwhile, most approachesare single-platform methods, in which design variables are either shared across all product variants or not atall. While in multiple-platform design, platform variables can have special value with regard to a subset ofproduct variants within the product family, and offer opportunities for superior overall design. An informationtheoretical approach incorporating fuzzy clustering and Shannon's entropy was proposed for platform variablesselection in multiple-platform product family. A 2-level chromosome genetic algorithm (2LCGA) was proposedand developed for optimizing the corresponding product family in a single stage, simultaneously determiningthe optimal settings for the product platform and unique variables. The single-stage approach can yield im-provements in the overall performance of the product family compared with two-stage approaches, in which thefirst stage involves determining the best settings for the platform and values of unique variables are found foreach product in the second stage. An example of design of a family of universal motors was used to verify theproposed method.