Speed Disturbance in the Diesel Engine Electronic Control System

In order to sample the speed signal of electronic diesel engine in real time and make the engine work reliable, the diesel engine control system's speed acquisition was studied and the problem of speed disturbance was solved. The control system was based on the 8?bit electronic control unit(ECU) system and the assembly language was used to design the software for controlling the engine fuel quantity and the turbocharger of the variable geometry turbine for the heavy duty diesel engine. By changing the timing method for speed acquisition, the problem of speed disturbance was solved and the reliability of the ECU was improved.

Influence of Oil Film Inertia on Piston Skirt Lubrication in High Speed Engine

By an iteration method, the influence of oil film inertia on piston skirt lubrication in a high speed engine is investigated. By alternately solving the Navier-Stocks equations and the Reynolds equation, the new iteration method can trace the variations of velocity field and pressure field with time. Based on this, the mixed-lubrication model suitable for the piston skirt of high engines is proposed. By introducing the inertia coefficient, the new lubrication model includes the inertia term in oil film. The model can be also used to solve for the lubrication performances of a piston skirt in low or medium speed engines and for lubrication problem in general excluding the inertia term of oil film , when the inertia coefficient is put equal to zero. The calculation results show that the influence of oil film inertia on the friction force increases with the ratio of the piston skirt's length to its diameter, the inertia coefficient and the eccentricities of the lower and the upper piston skirt, with other conditions kept constant, while the influence of it on the load capacity of oil film is small.

Research on H_2 speed governor for diesel engine of marine power station

The frequency stability of a marine power system is determined by the dynamic characteristic of the diesel engine speed regulation system in a marine power station. In order to reduce the effect of load disturbances and improve the dynamic precision of a diesel engine speed governor, a controller was designed for a diesel engine speed regulation system using H2 control theory. This transforms the specifications of the system into a standard H2 control problem. Firstly, the mathematical model of a diesel engine speed regulation system using an H2 speed governor is presented. To counter external disturbances and model uncertainty, the design of an H, speed governor rests on the problem of mixed sensitivity. Computer simulation verified that the H2 speed governor improves the dynamic precision of a system and the ability to adapt to load disturbances, thus enhancing the frequency stability of marine power systems.

EFFECTS OF INJECTION STRATEGY ON D.I. DIESEL ENGINE COMBUSTION

Experiments are conducted to develop an understanding of how split injections can affect the combustion and emission characteristics of a D.I. diesel engine with a common-rail injection system. The ratio of the amount of fuel injected between two injection pulses and the injection interval is varied keeping the injected fuel quantity constant. Results show that under the 70D90-10 injection pattern, the engine achieves the lower NOx-smoke emissions and BSFC compared with the single injection pattern. The heat release rate and the temperature show that the split injections increase the initial premixed burn and retards the diffusion burn. With the balance of these two effects, the maximum in-cylinder temperature decreases while the 50% heat release point is held at almost the same crank angle. Therefore, both NOx emission and BSFC are improved while keeping the smoke emission at the same level.

Current situation and development trend of design methods for subgrade structure of high speed railways

Purpose–This method will become a new development trend in subgrade structure design for high speed railways.Design/methodology/approach–This paper summarizes the structural types and design methods of subgrade bed for high speed railways in China,Japan,France,Germany,the United States and other countries based on the study and analysis of existing literature and combined with the research results and practices of high speed railway subgrade engineering at home and abroad.Findings–It is found that in foreign countries,the layered reinforced structure is generally adopted for the subgrade bed of high speed railways,and the unified double-layer or multi-layer structure is adopted for the surface layer of subgrade bed,while the simple structure is adopted in China;in foreign countries,different inspection parameters are adopted to evaluate the compaction state of fillers according to their respective understanding and practice,while in China,compaction coefficient,subsoil coefficient and dynamic deformation modulus are adopted for such evaluation;in foreign countries,the subgrade top deformation control method,the subgrade bottom deformation control method,the subsurface fill strength control method are mainly adopted in subgrade bed structure design of high speed railways,while in China,dynamic deformation control of subgrade surface and dynamic strain control of subgrade bed bottom layer is adopted in the design.However,the cumulative deformation of subgrade caused by train cyclic vibration load is not considered in the existing design methods.Originality/value–This paper introduces a new subgrade structure design method based on whole-process dynamics analysis that meets subgrade functional requirements and is established on the basis of the existing research at home and abroad on prediction methods for cumulative deformation of subgrade soil.

New technologies for high-risk tunnel construction in GuiyangGuangzhou high-speed railway

Based on the construction of high risk tunnels in Guiguang-Guangzhou high-speed railway, several new technologies were developed for high-risk tunnel con- struction. First, an integrated advanced geological predic- tion was developed for tunneling in karst area. Then, a new system of ventilation by involving the dedusting technol- ogy was proposed and used in the field, which received a good air quality. Finally, a method to minimize the dis- tance between the working face and the invert installation was proposed by optimizing the invert installation and adopting the micro bench method. Applying the method to the project obtained an excellent result. The achievement obtained for this study would be able to provide a valuable reference to similar projects in the future.

Asymptotic Analysis Soot Model and Experiment for a Directed Injection Engine

The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP （temperature phases） model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T〈 1 500 K and excess air factor Ф〉0.6, only the soot precursors-- polycyclic aromatic hydrocarbons（PAH） is created and there is no soot emission. When zone temperature T ≥ 1 500 K and excess air factor Ф〈0.6, PAHs and soot source terms （particle inception, surface growth, oxidation, coagulation） are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. KIVA standard model and experimental data are analyzed for the results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.

米勒循环对柴油机燃用生物柴油的性能研究

借助GT-Power软件实现某机车柴油机仿真模型的搭建,采用试验对仿真模型的准确性进行分析验证。研究在75%负载1000r/min工况燃用5种生物柴油B0、B10、B20、B50和B100,分析采用两种米勒循环对柴油机油耗、功率以及排放功能的影响。试验结果表明:柴油机功率发生变化拐点在30℃A米勒度处,油耗变化拐点在30℃A米勒度,碳烟排放发生变化拐点在20℃A米勒度,在该工况条件下NOx排放降低的效果较为显著。综合分析可知,在75%负载1000r/min工况条件下燃用B10生物柴油,米勒度为30℃A且变气阀重叠角米勒循环下柴油机表现最为佳。

盐渍土既有高速铁路路基压实质量检测

高速铁路路基填料压实标准主要通过压实系数、地基系数、动态变形模量等指标进行控制。对于既有路基,在不破坏路基的条件下,路基内部的控制指标难以有效测试。为评价某海外项目既有路基内部填料压实情况,最大程度减少对既有路基工程的扰动破坏,通过试验段建立了动力触探试验(DPT)锤击数与实测压实系数、地基系数、动态变形模量的拟合关系式,并将其应用于该项目全线路基内部压实质量检测。结果表明:应用该拟合关系式能够避免对既有路基的破坏,节约工期,取得了较好的经济效益。

常导高速磁浮工程试验线初期建设长度研究

研究目的:我国常导高速磁浮已具备推进工程化试验和示范运营线建设的条件,需要建设工程试验线对高速磁浮关键技术进行验证。本文从常导高速磁浮工程试验线初期试验需求入手,工程试验线建设初期不考虑乘坐舒适性,尽量采用较大的加减速度,在满足初期达速试验需求的前提下减少初期试验线建设长度,节省试验线初期工程投资。研究结论:(1)高速磁浮工程试验线主要是确认时速600 km时的各种性能及实用化目标的有关试验;(2)工程试验线初期建设长度需满足列车加减速运行最小距离及一定匀速运行距离要求,在国产时速600 km常导高速磁浮列车参数一定的情况下,加减速度主要取决于牵引变流器的额定电压及最大电流,通过供电系统匹配性仿真计算,车辆越轻,定子分段长度越短,可提供的车辆加速度越大,工程试验线初期建设长度越短;(3)本研究结论可为常导高速磁浮工程试验线的建设提供参考。

高压共轨柴油机国产芯片控制系统研究

针对现有高压共轨柴油机电控单元高度依赖进口芯片、自主不足的问题,提出了基于全国产芯片的高压共轨柴油机电控单元方案。所设计的国产控制单元选用兆易创新的GD32F450芯片为控制核心,承担发动机数据采样、处理、存储与控制任务。首先,采用Boost升压电路提供喷油器峰值电流,利用分立器件设计双边驱动与电流反馈电路,在不依赖进口专用芯片的条件下,对喷油器驱动电流进行闭环控制;然后,基于FreeRTOS操作系统,开发高压共轨柴油机底层驱动软件,实现对不同任务调度周期的精准控制;最后,对所设计的电控单元进行了实验验证。结果表明,所设计的国产高压共轨柴油机电控单元功能齐全、工作稳定,双边驱动电路典型峰值电流为22 A,维持电流为10 A,最小喷射间隔时间为200μs,多次喷射性能与Bosch系统相当。发动机不同转速条件下任务调度周期精准、实时性好,研究证实了高压共轨柴油机电控单元全国产化方案的可行性,对推动发动机电控技术自主可控提供了有益参考。

基于强化学习的柴油机调速算法研究

为了更好地调节柴油机转速,提出一种强化学习–比例积分微分(proportional integral derivative, PID)控制器,并应用到了柴油机转速控制中。基于连续动作空间的柔性动作–评价(soft actor-critic, SAC)算法,结合连续型PID控制器,设计了一种强化学习–PID控制器,可代替传统PID控制的转速环。优化设计了基于演员–评论家(actor-critic)框架的输入输出和奖励函数以匹配柴油机特性,采用随机动作增加寻优效率,形成SAC-PID控制柴油机转速的网络交互结构,达到快速调整转速,减小稳定时间的效果。构建了以柴油机D6114为原型机的MATLAB/Simulink平均值模型,并利用试验数据验证了仿真模型的有效性。利用平均值模型,仿真验证了该控制算法效果。经过仿真验证本算法使柴油机转速响应曲线超调量更小,响应时间更快,鲁棒性更强,SAC-PID控制负载瞬态调速率和稳定时间均已达到1级精度指标。仿真对比验证了SAC算法的联合控制效果,结果表明其较其他算法更佳。

TDI发动机润滑油挤压高频噪声影响因素试验研究

针对涡轮增压柴油机的运行特点,在半消声试验室进行了发动机加速工况主轴承处润滑油挤压高频噪声的影响因素测试。研究过程基于发动机主轴承座振动测试和曲轴运动轨迹测试,重点分析了润滑系统特征和主轴承结构特征以及曲轴轴承支撑方式对高频挤压噪声的影响。结果表明:润滑油黏度、润滑油含气量、主轴承间隙、主轴颈形状和轴承支撑方式等均对主轴承座异常振动产生影响;当轴承载荷小,轴心偏心距较大,曲轴自转方向与公转方向相反时,主轴承润滑油压力升高,润滑油内的气泡被挤压产生高频的气泡破裂噪声,并伴随主轴承座异常振动;当曲轴运转稳定且轴心轨迹平顺时,主轴承座异常振动对应转速升高,高频噪声不易识别。

基于WPES与MEEMD的船用主机振动研究

为揭示船用长冲程低速柴油机健康状态下的振动特征,采用小波包能量谱(Wavelet Packet Energy Spectrum, WPES)和改进的总体平均经验模态分解(Modified Ensemble Empirical Mode Decomposition, MEEMD)结合的特征提取方法,对典型推进工况下低速机的表面振动信号进行3层小波包分解和重构。通过对能量占比较大的节点采用MEEMD方法进行分解,获得IMF1分量频谱。研究结果表明,在40%以下的较低发动机负荷时,各单次燃烧循环的振动波动较小,振动幅值基本一致。提升至50%以上发动机负荷时,燃烧引起振动波动明显增强。50%工况下,中高频能量占总能量的41.51%,为主要振动源。

面向车次取消的票额分配与停站方案组合优化研究

当列车因严重干扰而取消时,大量旅客将在车站滞留,同时铁路公司收益也会受到一定影响,合理的票额分配是解决此类问题的有效方法。在差异化设置换乘旅客优先权基础上,构建了以铁路公司收益最大化和偏离原时刻表最小化为目标的票额分配和停站方案组合优化模型,并通过增加不等式组约束条件将其线性化;利用求解器GUROBI对上述模型进行求解并分析算例。研究结果表明:当列车因干扰而取消时,与不采用任何措施相比,灵活停站策略能有效地减少滞留旅客数量19.7%以上;铁路公司收益增加21.8%以上。

基于MEEMD算法的二冲程柴油发动机机体振动分析

二冲程低速柴油机具有复杂的振动特性,传统的经验模态分解(Empirical Mode Decomposition,EMD)算法对其振动信号处理效果不理想。为此,采用修正多元集合经验模态分解(Modified Ensemble Empirical Mode Decomposition,MEEMD)算法对低速柴油机机体振动信号进行分解。首先,采用三轴加速度计测量发动机机体振动。然后利用均方根(Root Mean Square,RMS)对三轴振动强度进行分析。最后,对x轴上的信号进行MEEMD分析。结果表明:砌块在x轴方向的振动强度最大;与EMD算法相比,MEEMD算法可以抑制模态混合,有助于更好地识别块振动激励。

高速铁路工程智能建造领域虚拟仿真实训教学改革研究与实践

针对服务高速铁路工程智能建造领域的高速铁道工程专业教学实训过程中存在的高难度、高投入、高风险、难再现、难实施、难观摩的教学实训难题,研究与虚拟仿真相适应的实训教学课程体系,将信息技术和专业群现有实训设施深度融合,着力开展虚拟仿真技术在实训项目中的应用。

基于IWOA的高速列车运行曲线节能优化研究

为降低高速列车运行能耗,使列车经过变坡点和变曲率点的附加阻力计算更精确、更贴近实际,提出了一种改进的鲸鱼优化算法(improved whale optimization algorithm,IWOA),对高速列车的运行曲线进行节能优化。首先,建立高速列车多质点附加阻力模型;其次,考虑满载率对列车运行能耗的影响,以准时、准点、限速为约束条件,构建新的能耗模型;然后,用IWOA对中间线路牵引-惰性工况转换点的最优位置进行搜索,IWOA引入混沌映射策略、自适应收敛因子和哈里斯鹰围攻机制,能有效提高算法的收敛速度和寻优精度,全局搜索能力显著增强,从而实现高速列车进一步节能运行的目的。最后,以合肥站—蚌埠站线路参数与CRH3型高速列车参数为实例,基于MATLAB平台进行仿真。仿真结果表明:采用PSO算法、GA算法和IWOA对高速列车运行曲线进行节能优化,优化后的曲线使列车运行能耗分别降低了7.81%,10.16%和15.95%。因此,IWOA对列车节能优化效果更加明显。

船舶柴油机主轴承温度过高问题的处置及预防工作方案

船舶柴油机在使用过程中,主轴承突发故障时有发生,主要表现现象为主轴承温度过高。如未能及时有效处理,将严重影响柴油机的正常运行。本文从故障机理的角度出发,研究主轴承温度过高的各项成因,并分析故障的各种表现形式。基于滑油温度过高、滑油压力过低或无压力、曲轴箱中出现异常敲击声等主要的附加故障特征,本文分析故障发生后的主要危害,重点探讨故障的处置流程和排除方法,进而提出故障预防方案,为船舶柴油机的安全使用与维护提供理论依据。

超高速激光熔覆技术及其耐磨蚀涂层材料研究进展

超高速激光熔覆技术是一种新型的表面涂层制备技术,可用于制备具有冶金结合的致密金属防护涂层。与传统熔覆工艺相比,超高速激光熔覆的加工效率高、涂层稀释率低,且涂层内部晶粒组织明显细化,可表现出更加优异的防护性能,在工业生产中具有广阔的应用前景。介绍了超高速激光熔覆技术的原理与加工特点,分析了国内外超高速激光熔覆设备的发展现状,综述了超高速激光熔覆涂层材料的研究进展,讨论了当前超高速激光熔覆涂层发展的主要问题,并展望了超高速激光熔覆技术及其涂层材料的发展趋势。