Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.     

船舶主柴油机燃油波尔滤器的改进方案设计

船舶主柴油机是船舶安全航行的心脏,而燃油波尔滤器担负着燃油过滤与净化的重要任务,是为主柴油机提供可靠、洁净燃油的重要设备。本文主要针对目前燃油波尔滤器工作存在的诸多问题,介绍了燃油波尔滤器的结构及工作原理,分析了设备存在的不足;并通过流体力学相关计算和设备工作性能要求,提出了系统改进设计方案,从而为下一步船舶修理提供改造依据,最终达到提高设备工作稳定性和保障主柴油机安全运行的目的。     

火箭车水平助飞方案仿真及分析

地面辅助起飞是大起降质量差飞行器的重要起飞方式之一.地面辅助起飞系统起飞过程工况复杂,对飞行器的俯仰角响应提出了更高的要求,传统研究通常采用数值计算的方法,计算量大,过程繁琐,结果不直观.针对以上问题,以大型飞行器"霍托尔"为背景,采用分段式建模的方法建立地面辅助起飞系统的动力学模型,运用LMS Virtual.Lab Motion和MATLAB/Simulink进行联合仿真,并设计了控制俯仰角的PID回路.仿真结果表明,采用该方法得到的动力学模型合理,俯仰角控制系统能对俯仰角实现有效控制,起飞系统工作过程稳定.     

Computer simulation of optimal functioning regimes with minimum fuel consumption for automotives

The paper deals with computer simulation that allows the calculus of operating regimes with minimum fuel consumption for road vehicles, using engine’s mechanical characteristics for power and consumption, characteristics which are known from experimental determinations and are indicated by engine manufacturer. For the case considered, are establish the minimum fuel consumption for different car speeds, speeds according to engine rotations for minimum fuel consumption regimes and transmission ratios that ensure the minimum fuel consumption for the automotive speeds.     

基于多目标遗传算法的混合动力电动汽车控制策略优化

混合动力电动汽车是一个高度复杂的非线性系统,并且影响其控制策略的参数较多,要对这样的系统进行优化,常规的优化算法显得无能为力,模型的精确程度也直接影响了选取参数的可靠性.应用汽车动力性、排放性高级模拟分析软件AVL CRUISE,联合Matlab/Simulink软件,建立合动力电动城市客车整车动态性能仿真分析模型,以百公里油耗和排放指标为优化目标,运用多目标遗传优化算法,针对欧洲、日本及中国的城市公交循环工况对混合动力系统工作模式的选择和能量流的分配进行全局优化,减少了运算时间,获得一组可靠的可行解,精确地确定出控制逻辑参数.该解集在很大程度上同时提高了原车的燃料经济性和排放性能,并且为混合电动车的设计和控制提供了一个适宜的选择范围,设计者可以按不同的要求进行不同的方案选择.     

船舶节能新技术开发与应用研究

随着船舶燃油价格的上涨,船舶节能技术得到了广泛的关注,本文主要介绍了国内外船舶节能新技术的研究和进展.本文重点介绍了主机动力系统、制冷系统、推进系统和油料系统等的综合节能技术措施.再借助管理系统的帮助,将能为国内的船舶节能的发展提供有利的推动.     

Optimization algorithm for diesel engine operating parameters based on a vehicle driving test cycle

For compliance with stringent exhaust emissions regulations, diesel engines have been equipped with electronically controlled components. Hence, there are various engine operating parameters that must be optimized, however optimization of these parameters is complicated. The objective of this research is to provide a new optimization algorithm for the diesel engine operating parameters with consideration of the vehicle control strategy. To optimize engine operating parameters, the concept of the vehicle-based optimization has been introduced. The engine response functions for performance and emissions were determined using the design of experiments, the response surface method and regression method with various engine operating parameters. Then, the engine operating points of the vehicle during the test cycles were analyzed, and the fuel consumption and emissions were estimated. Consequently, the engine operating parameters at each operating point were optimized to reduce the fuel consumption and the emissions such as NOx and PM by using the gradient method. Moreover, a new optimization algorithm enables to optimize engine operating parameters in various test cycle without additional engine experiment.     

水压人工肌肉驱动喷水矢量推进系统设计与试验

传统喷水矢量推进系统的驱动器存在密封困难、易腐蚀、使用寿命短、结构复杂等问题。为了解决这些问题,开发了水压人工肌肉驱动的喷水矢量推进系统。基于水压人工肌肉调节关节转角的驱动方式,对二自由度喷水矢量推进系统进行设计,并建立水压人工肌肉工作压力与喷嘴偏转角度的对应关系,先后进行了喷嘴矢量调节试验和水下自航试验。喷嘴矢量调节试验结果显示,当人工肌肉压差分别为0.310,0.614,0.898,1.158,1.386,1.584 MPa时,喷嘴实际偏转角度为13.56°,21.66°,33.24°,44.21°,52.80°,56.88°,试验结果与理论计算结果平均偏差为10.8%。水下自航试验表明,水压人工肌肉作为驱动器不仅能够满足喷嘴偏角矢量调节的要求,同时能够实现喷水矢量推进机器人的矢量运动,为研发能耗低、结构紧密的水下智能装备提供了新的思路。     

Novel Ship Propulsion System

As the development tends towards high-speed, large-scale and high-power, power of the ship main engine becomes larger and larger. This make the engine design and cabin arrangement become more and more difficult. Ship maneuverability becomes bad. A new ship propulsion system, integrated hydraulic propulsion (IHP), is put forward to meet the development of modem ship. Principle of IHP system is discussed. Working condition matching characteristic of IHP ship is studied based on its matching characteristic charts. According to their propulsion principle, dynamic mathematic models of IHP ship and direct propulsion (DP) ship are developed. These two models are verified by test sailing and test stand data. Based on the software Matlab/Simulink, comparison research between IHP ship and DP ship is conducted. The results show that cabin arrangement of IHP ship is very flexible, working condition matching characteristic of IHP ship is good, the ratio of power to weight of IHP ship is larger than DP ship, and maneuverability is excellent. IHP system is suitable for engineering ship, superpower ship and warship, etc.     

考虑产品运行大数据的装载机变速箱优化设计

准确获知产品运行大数据对于产品研发与创新具有重要意义。传感网、物联网和CPS等技术的发展使得越来越多的产品运行数据获取成为可能,在此基础上,提出基于运行大数据采集、分析和应用的装载机变速箱优化设计流程。首先选取原生土、铁矿石、细沙和煤渣四种作业对象的典型作业工况,设计采集方案并完成运行大数据采集;然后将获取的挡位信号转化为累积挡位利用率,液压泵压力信号转化为液压系统分流功率,并以此作为轮式装载机动力性和燃油经济性的建模优化因素;最后利用MOPSO和NSAG-Ⅱ两种优化算法权衡动力性、经济性及约束条件的多目标竞争与冲突关系,最终获得保证最优动力性基础上,实现最佳经济性的可行域解集。两种算法获得的最优解集相对于原始设计,在同等仿真条件下,分别使功率损失率降低8.83%、4.80%,工况油耗降低0.19%、0.34%。研究表明,将在役产品运行大数据反馈应用于产品研发前端的设计方法,是实现产品升级和创新设计的一个有效途径。     

船舶推进轴系扭振模拟实验系统研究

根据船舶扭振的特点,采用模块化设计,开发船舶推进装置的扭振模拟实验平台;以齿盘和光电开关为传感器,NI的信号调理箱、数据采集卡等为主要器件实现扭振信号的采集;基于LabVIEW软件构建扭振监测系统。该系统实时监测推进轴系的振动情况,同时对振动信号做时域分析、频域分析和相位分析等。实验还模拟了激振力、负载等原因引起的扭振情况。实验结果表明,该方案实现了设计的目标,较好地满足了教学及科研需求。     

A new nano-accuracy AFM system for minimizing Abbe errors and the evaluation of its measuring uncertainty

A new AFM system was designed for the establishment of a standard technique of nano-length measurement in a 2D plane. In a long range (about several tens of micrometers), measurement uncertainty is dominantly affected by the Abbe error of the XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motions. In this paper, an AFM system with minimum offsets of XY sensing is designed. Moreover, the XY scanning stage is designed to minimize the rotation angle, as Abbe errors occur through multiple combination of the offset and the rotation angle. To minimize the rotation angle, an optimal design is performed by maximizing the ratio of the stiffness of the parasitic direction to the motion direction of each stage. This paper describes a design scheme of a full AFM system, in particular, the XY scanner. The full range of a fabricated XY scanner is 100 microm x 100 microm. The tilting, pitch and yaw motions are measured by an autocollimator to evaluate the performance of the XY stage. The results show that the XY scanner have a 0.75 arcsec parasitic rotation about the maximum range, thus the uncertainty in terms of the Abbe errors are very small relative to other standard equipment. Using this AFM system, a 3mum pitch specimen was measured. The measurement uncertainty of the total system was evaluated especially about pitch length. For a 1D evaluation, Abbe errors are the most dominant factor, and the expanded combined uncertainty (k = 2) of system was square root (4.13)(2)+(5.07 x 10(-5)xp)(2)(nm). For a 2D evaluation, mirror non-orthogonality and Abbe errors are dominant factors, and expanded combined uncertainty (k = 2) of the system was square root (4.13)(2)+(1.228 x 10(-4)xp)(2) in the X direction, and square root (6.28)(2)+(1.266 x 10(-4)xp)(2) in the Y direction (the unit is nanometers), where p is the measured length in nm.     

Static and Dynamic Slider Air-Bearing Behavior in Heat-Assisted Magnetic Recording Under Thermal Flying Height Control and Laser System-Induced Protrusion

The air bearing’s response to regions of elevated temperature on its bounding surfaces (the slider and disk) may be an important consideration in the head–disk interface design of heat-assisted magnetic recording (HAMR) systems. We implement the general non-isothermal molecular gas lubrication equation into an iterative static solver and dynamic air-bearing solver to evaluate the effect of localized heating of the air-bearing surface (ABS) due to the near-field transducer (NFT). The heat-dissipating components in our simplified HAMR design are the NFT, laser diode, and thermal flying height control (TFC) heater. We investigate the effect of each HAMR slider component on ABS temperature and thermal deformation and the slider’s flying height. The NFT induces a localized thermal spot and protrusion on the larger TFC bulge, and it is the location of maximum temperature. This ABS temperature profile alters the air-bearing pressure distribution, increasing the pressure at the hot NFT location compared with predictions of an isothermal air-bearing solver, so that the center of the pressure acting on the ABS is slightly closer to the trailing edge, thereby decreasing the pitch angle and increasing the minimum flying height. Other researchers have shown that the NFT’s thermal response time may be much faster than its protrusion response time (Xu et al. in IEEE Trans Magn 48:3280–3283, 2012). The slider’s dynamic response to a time-varying NFT thermal spot on the ABS while the combined TFC and NFT induced thermal protrusion remains constant is investigated with our dynamic air-bearing solver. We simulate the slider’s step response to a suddenly applied ABS temperature profile and a pulsed temperature profile that represents laser-on over data zones and laser-off over servo zones. The sudden (step) or rapid (pulse) increase in ABS temperature induces a sudden or rapid increase in pressure at the NFT location, thereby exciting the air bearing’s first pitch mode. For the slider design and simulation conditions used here, the result of the pitch mode excitation is to alter the position of the center of pressure in the slider’s length direction, thereby changing the pitch moment. In response, the pitch angle and minimum flying height change. The step response decays after approximately 0.15 ms. Because the laser duty cycle is much shorter than this response time, a periodic disturbance is predicted for the center of pressure coordinate, pitch angle, and minimum flying height. The peak-to-peak minimum flying height modulations are relatively small (only up to 0.126 nm); more significantly, the time-averaged minimum flying height increases 0.5 nm for the NFT that reached 208 °C compared to simulations of the isothermal ABS at ambient temperature.     

An investigation of a cavitating venturi flow control feature in a cryogenic propellant delivery system

This study details the design and performance characterization for a cryogenic cavitating venturi. This flow control system is intended for mass flow regulation of cryogenic propellants, such as liquid oxygen and liquid methane, in reaction control propulsion systems. Through in situ flow tests, the discharge coefficient for the venturi was calculated and utilized to determine the mass flow rate for specified inlet pressures of the propellants. The test results revealed that the cavitating venturi indeed performed as a flow rate control feature in both liquid water and LCH₄ flow under a steady state operating within pressure ratios below 0.69.     

以高压CO2为介质的推力箔片轴承静特性分析

针对超临界二氧化碳布雷顿循环用压缩机中的推力箔片轴承开展了数值研究,通过MATLAB编程数值计算求解变密度、变黏度湍流雷诺方程和耦合弹性箔片变形方程,得到楔形间隙内气膜压力分布及推力箔片轴承承载力和摩擦功耗,并与空气润滑介质对比;进一步分析推力箔片轴承节距比、瓦张角、楔形高度及最小气膜厚度对轴承承载力和摩擦功耗的影响。计算结果表明:高压CO₂下弹性箔片变形比常压空气时更大,轴承承载力远高于常压空气轴承;瓦张角为45°和节距比为0.5的推力箔片轴承具有较高的承载力和较低的摩擦功耗;楔形高度设计过大会降低承载力,增大摩擦功耗,使载荷集中在水平区域;增大最小气膜厚度设计值虽能减小摩擦功耗,但却引起承载力的显著降低。     

基于HYDSIM的电控气缸注油器设计与仿真

电控喷油是现代柴油机气缸润滑系统的研究趋势,对于机械式注油器的改造也是旧船改造的一个重要方向.为了提高性能和减少燃油消耗率,设计了一种回流阀脉冲式电控气缸注油器,并通过HYDSIM软件的模拟验证,说明该注油器创新设计的可行性.     

基于模糊控制的风机电动变桨距系统仿真

在介绍风力发电机电动变桨距系统的基础上,以实现对桨距角变化的精确控制为目的,对电动变桨距系统进行设计并提出对变桨距系统控制器的设计.针对风力发电系统的非线性、时变和强耦合的特点,将模糊控制引入到变桨距控制中,在高于额定风速的情况下,根据主控制器由风速变化计算出的桨距角变化量,调节桨叶的位置.最后利用Simulink构建...     

基于全局模型的直流内磁式磁流体推进系统研究

阐述了磁流体推进系统的不同分类和面临的问题,着重研究了直流内磁式磁流体推进系统的结构设计和优化.为进一步提高推进效率,从动量和能量守恒出发提出一种全局计算方法,研究船舶磁流体推进器的几何形状、尺寸和位置等参数,并通过对其不同组件和产生损失的综合分析得出一种优化模型.     

Passive flow control in liquid-propellant rocket engines with cavitating venturi

In a companion liquid rocket engine development project, due to the overall weight constraint of the propulsion system, a cavitating venturi is selected to control the liquid fuel and liquid oxidizer mass flow rates. Two cavitating venturis, one for the fuel and the other for the oxidizer, are designed to deliver the desired mass flow rates for a specified operating inlet pressure, temperature, and inlet cross-sectional area. The converging and diverging angles of the venturis are selected from the literature for minimum pressure losses. An experimental setup is designed to verify that the cavitating venturis can deliver the specified flow rates. Two different techniques are used to pressurize the system: in the first method, pressurized nitrogen gas is used, and in the second method, high pressure combustion gases generated from a solid propellant gas generator are used. Transient mass flow rates could not be measured using standard methods due to the short duration of the water tests; instead, average mass flow rates are calculated. The results verify that the designed cavitating venturis can indeed provide the desired mass flow rates.     

A fuel cell/battery hybrid power system for an unmanned aerial vehicle

A hybrid propulsion system composed of a homemade Polymer electrolyte fuel cell (PEFC) with a Lithium polymer (LiPo) battery in parallel connection was developed for Unmanned aerial vehicles (UAVs). The characteristics and performance of the system were evaluated considering its dynamic load responding capability and energy efficiency. A homemade PEFC stack composed of 36-unit cells and Balance of plant (BOP) was used to construct the fuel cell system directly connected to the propulsion system. Ten cells of a 3300-mAh 40C LiPo battery were combined with the PEFC system in parallel, and the LiPo battery was only switched on when high power was required for takeoff, acceleration and landing. The independent use of the homemade PEFC system and battery for the UAV showed a good load responding capability and a high fuel cell system efficiency of approximately 45%, which was obtained during cruising. The parasitic loss and the amount of unreacted hydrogen gas discharged outside of PEFC were nearly 3.91% and 0.89%, respectively. Results of the field test flights confirmed that the hybrid propulsion system based on the parallel connection of a PEFC system and a battery power is extremely effective in operating a UAV.