内燃机整机振动的频域控制研究

内燃机整机振动的频域特点显示其与整机振动的固有特性和内燃机的工作转速有关。在整机振动控制过程中,根据频域特性提出PFC（Partial Frequency Control）控制策略,建立以相关频带为函数的性能指标,对该特定频带内的振动施以额外的加权,则可以将主要控制能量集中在该特定频带内,从而提高控制效果。以某柴油机为例,在整机振动频域特性分析的基础上,进行了整机振动PFC控制过程的仿真计算。结果表明,振动控制过程中选定的被控模态在主频带内的振动均取得了高于75％的降幅,使整机振动得到了极大的抑制,控制效果明显。     

基于虚拟材料法建模的柴油机振动噪声分析

为精确模拟螺栓连接,并实现柴油机复杂结构的快速高效建模,提出了一种基于虚拟材料模拟螺栓连接的动力学参数化建模方法.结合工程数据,详细介绍了虚拟材料法动力学建模的过程;通过对比机体装配体的计算模态和试验模态,并结合计算模态保证判据(MAC),结果发现:基于虚拟材料法的计算和试验前三阶模态振型完全对应、MAC值全部大于0.9,且模态频率相差在5%以内,初步验证了其用于装配体模态计算具有较高的精度.将整机运用虚拟材料法和绑定约束法分别建模进行了振动噪声计算,结果表明:基于虚拟材料法的整机振动加速度计算值为146.3 dB,接近试验值的145.6 dB;整机辐射噪声A计权计算值为109.5 dB,与试验值108.0 d B相差较小;且振动和噪声计算与测试曲线贴合较好,进一步验证了此法用于整机振动噪声计算也具有较高精度,其相较于绑定约束法整机振动响应计算效率也显著提高.     

共轨柴油机缸内压力与整机振动噪声关系研究

共轨柴油机燃烧过程的缸内压力与表面振动以及整机噪声有着密切的联系。为了研究缸内压力对表面振动和整机噪声的影响规律,对缸内压力信号、表面振动以及噪声信号,从时域以及频域上,进行了多工况内在联系的研究,其中包括结构衰减曲线、相干函数曲线分析以及高通滤波的高频压力振荡计算等,并得出了在不同转速、不同负荷下,缸内压力的变化对表面振动以及整机噪声的影响规律。     

某中速柴油机底座刚度对整机模态影响分析

某型中速柴油机在试车台测试时振动偏大,初步判定系柴油机底座刚度不足引起.对柴油机底座进行改进设计,在此基础上对不同方案的底座进行刚度计算和模态分析,然后对不同底座方案整机进行模态计算,得到底座刚度与整机振动模态间的关系.同时分析了采用不同垫板对整机模态的影响,为柴油机底座的选型设计提供参考.     

内燃机整机振动模糊控制系统的设计

内燃机振动的主要类型是整机振动和扭转振动。主动控制则可以通过外界能量主动改变控制系统的某些参数来适应内燃机整机振动的变化,因此能达到更好的减振效果。本文以4135型柴油机为研究对象,建立了内燃机整机振动六自由度的数学模型并进行了动力学分析,明确了整机振动的主要干扰力,由此建立了占主导地位的内燃机整机垂向振动控制系统的数学模型。     

内燃机整机振动模糊控制系统的设计

内燃机振动的主要类型是整机振动和扭转振动。主动控制则可以通过外界能量主动改变控制系统的某些参数来适应内燃机整机振动的变化，因此能达到更好的减振效果。本文以4135型柴油机为研究对象，建立了内燃机整机振动六自由度的数学模型并进行了动力学分析，明确了整机振动的主要干扰力，由此建立了占主导地位的内燃机整机垂向振动控制系统的数学模型。     

6120型车用发动机曲轴轴向振动的分析研究

采用有限元数值计算方法和实验测试方法分别对6120型发动机曲轴轴向振振动进行较深入的研究,所获得的理论结果与实测的结果取得较好的一致,从而为进一步揭示出发动机曲轴轴向振动的规律性,降低发动机的整机振动奠定了基础。     

模态扩展在柴油机振动和噪声分析中的应用

文章对模态扩展的基本理论进行了阐述,并以准确的有限元模型和试验振动数据作为输入,应用模态扩展和边界元法求得某大型高速V6柴油机的整机结构辐射噪声,计算结果表明发动机的爆发压力、不平衡惯性力是低频辐射噪声的主要贡献者,而高频辐射噪声的主要来源是齿轮传动产生的振动激励,发动机本体模态对整机辐射噪声贡献相对较小。该实例充分验证了模态扩展的准确性和实用性,为后续发动机的振动和噪声控制指明了方向。     

某四缸柴油机龙门式气缸体动力响应分析

建立了某四缸龙门式柴油机气缸体的有限元分析模型,从某四缸龙门式柴油机气缸体的结构动态特性和振动响应进行分析,采用模态试验对有限元模型进行修正,通过有限元、多体动力学手段研究柴油机在额定工况下,以气缸燃气压力、活塞侧压力和主轴承作用力为主要因素,确定了柴油机所受的激励力,利用模态叠加法对柴油机进行了动态响应分析计算,得出了额定载荷下的整机振动烈度,并与整机振动烈度的实测值进行比较,验证了模型的正确性。     

某四缸柴油机龙门式气缸体动力响应分析

建立了某四缸龙门式柴油机气缸体的有限元分析模型,从某四缸龙门式柴油机气缸体的结构动态特性和振动响应进行分析,采用模态试验对有限元模型进行修正,通过有限元、多体动力学手段研究柴油机在额定工况下,以气缸燃气压力、活塞侧压力和主轴承作用力为主要因素,确定了柴油机所受的激励力,利用模态叠加法对柴油机进行了动态响应分析计算,得出了额定载荷下的整机振动烈度,并与整机振动烈度的实测值进行比较,验证了模型的正确性。     

Modelica-AeroDyn: Development,benchmark, and application of a comprehensive object-oriented tool for dynamic analysis of non-conventional horizontal-axis floating wind turbines

The exploitation of offshore wind energy by means of floating wind turbines is gaining traction as a suitable option to produce sustainable energy. Multi-rotor floating wind turbines have been proposed as an appealing option to reduce the costs associated with manufacturing, logistics, offshore installations, and operation and maintenance of large wind turbine components. The development of such systems is forestalled by the lack of a dedicated tool for dynamics and load analysis. Standard codes, such as FAST by NREL, offer the desired fidelity level but are not able to accommodate multi-rotor configurations. A few experimental codes have been also proposed, which may accommodate multi-rotor systems, but low flexibility makes them impractical to study a vast range of innovative multi-rotor FWTs concepts. To close the gap, this work presents the development and comprehensive benchmark of a fully coupled aero-hydro-servo-elastic tool able to easily accommodate arbitrary platform and tower geometries and the number of wind turbines employed. Development is carried out in Modelica, which allows for the employment of the same code functionality in a virtually unlimited number of physical configurations. Full blade-element momentum capabilities are achieved by integrating into Modelica the well-established NREL aerodynamic module AeroDyn v15 within FAST v8. Structural dynamics of tower and blades are implemented through a lumped-element approach. Hydrodynamic loads are computed by employing the DNV software SESAM WADAM. Thorough benchmark is performed against FAST, and positive results are obtained. The dynamic performance of a two-rotor floating wind turbine is finally assessed considering different turbulence spectrums.     

Performance and cost of fuel cells for urban air mobility

Several companies are developing enabling elements of urban air mobility (UAM) for air taxis, including prototypes of electric vertical take-off and landing (eVTOL) vehicles. These prototypes incorporate electric and hybrid powertrains for multi-rotor and tilt-rotor crafts. Many eVTOLS are using batteries for propulsion and charging them rapidly between the flights or swapping them for slow charging overnight. Rapid charging degrades the battery cycle life while swapping requires multiple batteries and charging stations. This study has conducted a technoeconomic evaluation of the eVTOL air taxis with alternate powertrains using hydrogen fuel cell systems being developed for light-duty and heavy-duty vehicles. We consider performance metrics such as fuel cell engine power, weight, and durability; hydrogen consumption and weight of storage system; and maximum take-off weight. The metrics for economic evaluation are capital cost, operating and maintenance cost, fuel cost, and the total cost of ownership (TCO). We compare the performance and TCO of battery, fuel cell and fuel cell – battery hybrid powertrains for multi-rotor and tilt-rotor crafts. We show that fuel cells are the only viable concept for powering multi-rotor eVTOLs on an urban scenario that requires 60-mile range, and hybrid fuel cells are superior to batteries as powertrains for tiltrotor eVTOLs.     

Integrated flow reactor that combines high-shear mixing and microwave irradiation for biodiesel production

A new simple flow system which is made up of a multi-rotor high-shear mixer connected to a multimode microwave reactor has been assembled. This simple loop reactor has been successfully used in the NaOH-catalyzed transesterification of refined palm oil in methanol. Thanks to optimal mass/heat transfer, full conversion was achieved within 5 min (biodiesel yield of 99.80%). High-quality biodiesel was obtained that is in accordance with international specifications and analytical ASTM standards. The procedure's high efficiency and low energy consumption should pave the way for process scale up.     

Load response of a two-rotor floating wind turbine undergoing blade-pitch system faults

Multi-rotor floating wind turbines are among the innovative technologies proposed in the last decade in the effort to reduce the cost of wind energy. These systems are able to offer advantages in terms of smaller blades deployed offshore, cheaper operations, fewer installations, and sharing of the floating platform. As the blade-pitch actuation system is prone to failures, the assessment of the associated load scenarios is commonly required. Load assessment of blade-pitch fault scenarios has only been performed for single-rotor solutions. In this work, we address the effect of blade-pitch system faults and emergency shutdown on the dynamics and loads of a two-rotor floating wind turbine. The concept considered employs two NREL 5-MW baseline wind turbines and the OO-Star semi-submersible platform. The blade-pitch faults investigated are blade blockage and runaway, that is, the seizure at a given pitch angle and the uncontrolled actuation of one of the blades, respectively. Blade-pitch faults lead to a significant increase in the structural loads of the system, especially for runaway fault conditions. Emergency shutdown significantly excites the platform pitch motion, the tower-bottom bending moment, and tower torsional loads, while suppressing the faulty blade flapwise bending moment after a short peak. Shutdown delay between rotors increases significantly the maxima of the torsional loads acting on the tower. Comparison of blade loads with data from single-rotor spar-type study show great similarity, highlighting that the faulty blade loads are not affected by (1) the type of platform used and (2) the multi-rotor deployment.     

Development and assessment of a novel solar heliostat-based multigeneration system

In this paper, a comprehensive study on thermodynamic analysis and assessment, through energy and exergy approaches, is conducted for a multigenerational solar based integrated energy system. The system proposed in this study is based on heliostat solar system integrated with steam turbine. The system is also integrated with seawater reverse osmosis desalination unit and absorption cooling system. The desalination unit operates with energy recovery through the utilization of Pelton turbine. The system produces cooling, heating, fresh water and hydrogen through electrolysis. It is furthermore designed to cover the demand of 4 MW electric power with the production of 1.25 kg/h of hydrogen and 90 kg/s of fresh water. The system advisor model software is applied on a case study for the solar heliostat optimization analysis.     

风电-抽水蓄能联合运行系统的模拟研究

构建了一个含风电—抽水蓄能联合运行系统的小型模拟电网,并对其拟定了一个风电—抽水蓄能联合运行方案;然后在最大化利用风电的目标下,建立了该方案的经济运行计算分析模型,经对该联合运行系统与普通风电系统的比较计算分析,验证了本模拟方案和计算模型的正确性;同时证明风电—抽水蓄能联合运行系统是最大化开发利用风能资源的有效途径,具有可观的经济效益和社会效益。     

辅助汽流通过冷却器进出热力系统的定量分析计算模型

火电机组的部分辅汽通过冷却器凝结为疏水后再进入热力系统,本文针对冷却器在热力系统中所处位置,以质量平衡与能量平衡为基础,应用矩阵理论,通过严谨的数学推演,提出了辅助汽流通过冷却器进出热力系统的定量分析计算模型,具有分析与计算方便、简洁、准确性高、通用性强等特点,为火电机组的节能降耗特别是辅助汽水系统的定量分析计算提供了新方法。     

Exergoeconomic analysis of a combined heat and power (CHP) system

This study deals with exergoeconomic analysis of a combined heat and power (CHP) system along its main components installed in Eskisehir City of Turkey. Quantitative exergy cost balance for each component and the whole CHP system is considered, while exergy cost generation within the system is determined. The exergetic efficiency of the CHP system is obtained to be 38.33% with 51 475.90 kW electrical power and the maximum exergy consumption between the components of the CHP system is found to be 51 878.82 kW in the combustion chamber. On the other hand, the exergoeconomic analysis results indicate that the unit exergy cost of electrical power produced by the CHP system accounts for 18.51 US$ GW^?1. This study demonstrates that exergoeconomic analysis can provide extra information than exergy analysis, and the results from exergoeconomic analysis provide cost‐based information, suggesting potential locations for the CHP system improvement. Copyright © 2007 John Wiley & Sons, Ltd.     

A new power-conditioning system for superconducting magnetic energystorage

A power conditioning system concept for superconducting magnetic energy storage (SMES), which can independently regulate the active and reactive power of the utility network, is presented. The system is composed of ten 100 MW modules connected in parallel. Each 100 MW module consists of a tap changing transformer and a 12 pulse, force commutated power converter. This system offers a significant reduction of the system rating by reducing the reactive power demand in the converter with control of the tap changing ratio and the converter firing angle. The operational concept of this system is verified through mathematical analysis and computer simulation. The dynamic system interaction between the SMES coil and the AC network is analyzed using a simulation model with EMTP. The analysis results prove that the concept is feasible. This system can be built with commercially available components and proven technologies     

Optimal green energy management for island resorts in Malaysia

This paper proposes optimum green energy systems for electricity generation of island resorts in Malaysia. A combination of solar energy and wind energy as intermittent renewable energy sources with a fuel cell (FC) system and a battery storage energy system as a backup to the green energy system is introduced for this study. This system is eco-friendly, economical over the long-term, highly sustainable and reliable. In addition, a diesel-based energy system as a non-green system is compared with the proposed green system. National Renewable Energy Laboratory's (NREL) HOMER software is used to determine and compare the optimal configuration green energy system with the diesel-based energy system in terms of net present cost, sensitivity analysis and pollutant gas emission. The feasibility and assessment of the proposed system is evaluated by utilizing the load profile and considering the geographical condition of a village (Juara village in Tioman Island) with approximately 30 chalets located in southern Malaysia. HOMER uses two types of load profiles for each given year. The first load profile is used during the presence of tourists, and the second profile is used when the locals are the main inhabitants of the island. The optimization management for the green energy system is performed through unit sizing to find the optimum power management analysis and to perform cost analysis of the system.The potential of renewable energy as well as a diesel-based energy system to meet the power demand for such a stand-alone system is considered. Technically feasible and economically viable green energy systems as prospective plans are explored in this study.