Effect of the front and rear weight distribution ratio of a Formula car during maximum-speed cornering on a circuit

Because Formula cars are lighter than ordinary cars, the optimal settings for this type of car are thought to be different from those of a ordinary car. The front and rear weight distribution ratio of a vehicle is an important parameter that exerts a significant influence on critical cornering. The tendency of a ordinary car to under-steer during critical cornering is determined by the front and rear weight distribution ratio of the vehicle. Specifically, when the front of an ordinary FR (front-engine, rear wheel drive) vehicle is slightly heavier than the rear, the car tends to understeer during critical cornering. However, the optimal weight distribution ratio for critical cornering is not obvious for a formula car because of its lightness. This observation was investigated using a driving course similar to a real driving course to perform a maximum speed cornering simulations. It was found that a front to rear weight distribution ratio of 40:60 resulted in the fastest lap time. This ratio also gave the best results in the maximum-speed driving experiment performed using a driving simulator. Moreover, the maximum lateral acceleration during turning, the driving force, and the load movement of the inside and outside wheels was calculated using experimental driving force data and the concept of a tire friction circle. As a result, driving mechanics have been determined for a vehicle having a front/rear weight distribution ratio of 40:60 while traveling at maximum speed.     

Measurement of hydrocarbon and carbon monoxide emissions during the starting of automotive DI Diesel engines

Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions. Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly unfavorable for the combustion progress. Additionally, the catalytic converter is ineffective due to the low engine temperature. In conjunction with adequate engine settings (fuel injection and fresh air control), either the glow plugs or the intake air heater are activated during a portion of the engine warm-up period, so that a nominal engine temperatures is reached faster, and the impact of these difficulties is minimized. Measurement of gaseous pollutants during engine warm-up is currently possible with detectors used in standard exhaust gas analyzers (EGA), which have response times well-suited for sampling at such transient conditions. However, these devices are not suitable for the measurement of exhaust emissions produced during extremely short time intervals, such as engine starting. Herein, we present a methodology for the measurement of the cumulative pollutant emissions during the starting phase of passenger car DI Diesel engines, with the goal of overcoming this limitation by taking advantage of standard detectors. In the proposed method, a warm canister is filled with an exhaust gas sample at constant volumetric flow, during a time period that depends on the engine starting time; the gas concentration in the canister is later evaluated with a standard EGA. When compared with direct pollutant measurements performed with a state-of-art EGA, the proposed procedure was found to be more sensitive to combustion changes and provided more reliable data.     

Analysis of disc brake instability due to friction-induced vibration using a distributed parameter model

This paper deals with friction-induced vibration of a disc brake system with a constant friction coefficient. A linear, lumped, and distributed parameter model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are used to investigate the dynamic stability, and, in order to verify simulations which are based on the theoretical model, an experimental modal test and dynamometer test are performed. The comparison of experimental and theoretical results shows good agreement, and the analysis indicates that modal coupling due to friction forces is responsible for disc brake squeal. Also, squeal type instability is investigated, using a parametric analysis. This indicates which parameters have influence on the propensity of brake squealing. This is helpful for validating the analysis model and establishing confidence in the experimental results of the modified system. These results may also be useful during system development or diagnostic analysis.     

Fatigue design approach for the spot-welded T-type member using a simulated single spot-welded joint

In order to develop a fatigue design method for actual railroad car and commercial vehicle body structures using the fatigue data of simulated single spot-welded lap joints, we first analyzed the stress distribution and evaluated fatigue strength of spot-welded T-type members that are the components of actual railroad car and commercial vehicle body structures. Next, fatigue design approach of these members using the fatigue data of single spot-welded lap joints was investigated. From our results, we found that, even though there was a quantitative difference of fatigue strength between the single spot-welded joint and the actual members over the same number of fatigue cycles, through the use of appropriate correction, the fatigue design criterion of actual spot-welded members, such as those used in railroad car and commercial vehicle body, can be predicted using the fatigue strength of single spot-welded joint.     

Excitation force analysis of a powertrain based on CAE technology

The excitation force of a powertrain is one of major sources of interior noise in a vehicle. This paper presents a novel approach to predict the interior noise caused by the vibration of the powertrain by using the hybrid TPA (transfer path analysis) method. Although the traditional transfer path analysis (TPA) is useful for the identification of powertrain noise sources, it is difficult to modify the structure of a powertrain by using experiments for the reduction of vibration and noise. In order to solve this problem, the vibration of the powertrain in a vehicle is numerically analyzed by using the finite element method (FEM). The vibration of the other parts of the vehicle is investigated by using experiments based on vibrato-acoustic transfer function (VATF) analysis. These two methods are combined for the prediction of interior noise caused by a powertrain. Throughout this research, two papers are presented. This paper presents a simulation of the excitation force of the powertrain exciting the vehicle body based on numerical simulation. The other paper presents a prediction of interior noise based on the hybrid TPA, which uses the VATF of the car body and the excitation force predicted in this paper.     

Effect of intake valve swirl on fuel-gas mixing and subsequent combustion in a CAI engine

A fully three-dimensional model was used to investigate the optimal value for intake valve lift in a CAI engine. Uniform mixing in the engine is a key parameter that affects the auto-ignition reliability and thermal efficiency. The method of intake of the air supply often determines the uniformity (or quality) of the fuel-air mixture. In this paper, four strategies were applied for controlling the swirl intensity of intake air. The variation of the intake valve lift induces different swirling and tumbling intensities. Both experimental data and 1D WAVE software (Ricardo, Co.) were coupled with the 3D model to provide pressure and temperature boundary conditions. The initial condition of the EGR mass fraction was also provided by the 1D model. The benchmark scenario (Case 1) was considered as a valve lift with 2 mm for all intake valves. We found that an intake valve lift of 6 mm with the other intake valve closed (i.e., Case 5) yielded the largest swirling (helical motion in the axial direction) and tumbling, which in turn rendered optimal fuel-gas mixing. We also found that fuel distribution affected the auto-ignition sites (or spot). The better the mixing, the greater the gas temperature and combustion efficiency achieved, as seen in Case 5. The NOx level, however, was increased due to the gas temperature. The optimal operating condition is selected from the viewpoints of environmental protection and combustion efficiency.     

Vehicle stability control system for enhancing steerabilty,lateral stability,and roll stability

The Vehicle stability control system is an active safety system designed to prevent accidents from occurring and to stabilize dynamic maneuvers of a vehicle by generating an artificial yaw moment using differential brakes. In this paper, in order to enhance vehicle steerability, lateral stability, and roll stability, each reference yaw rate is designed and combined into a target yaw rate depending on the driving situation. A yaw rate controller is designed to track the target yaw rate based on sliding mode control theory. To generate the total yaw moment required from the proposed yaw rate controller, each brake pressure is properly distributed with effective control wheel decision. Estimators are developed to identify the roll angle and body sideslip angle of a vehicle based on the simplified roll dynamics model and parameter adaptation approach. The performance of the proposed vehicle stability control system and estimation algorithms is verified with simulation results and experimental results.     

桥梁施工中混凝土裂缝的成因及防治

混凝土的抗拉强度只有抗压强度的十分之一,混凝土的质量受施工影响非常大,混凝土构件很容易产生各种裂缝,严重影响混凝土的内在质量和外观质量。文中介绍了桥梁施工过程中混凝土裂缝的成因及其防治措施。     

“麦莎”台风影响期间黄浦江上游潮位变化特点及分析计算

该文系统分析了“麦莎”台风期间黄浦江上游潮位变化规律,针对黄浦江上游出现历史最高潮位,而下游水位并不高的特点,从水利工程建设、水闸运行、上游来水、潮汐作用和降水等方面运用水文学和水力模型进行原因分析及计算。结果表明,是多种因素综合作用造成黄浦江干流米市渡江段水位超历史记录,其中,大范围强降雨是潮位抬升的主要原因。同时,用水力模型初步模拟计算了各种因素所产生的作用。     

沥青路面平整度的施工控制

平整度是沥青路面施工的重要控制指标之一。从原材料、混合料级配、基层施工质量、现场摊铺碾压方法等方面,结合连(云港)徐(州)高速公路的路面施工及多年的路面施工管理经验,提出了沥青路面平整度的施工控制方法,有效地提高了沥青路面的平整度,对于沥青路面施工中平整度的控制,也具有一定的指导价值。