考虑压力脉动的消防水炮自适应炮头射流系统参数振动研究

消防水炮自适应炮头可根据流体压力和流量变化自动调整炮口开度,从而显著提升其射流性能。考虑自适应炮头射流系统中流体的压力脉动,结合流体体积弹性模量与刚度间的关系,建立基于时变流体刚度的射流系统参数振动动力学模型,采用多尺度法推导脉动激励频率接近射流系统固有频率和固有频率与脉动频率的组合频率时的共振响应公式,分析射流系统的主共振和组合共振响应。结果表明射流系统发生主共振响应时,激励频率占主导成分,且接近一阶固有频率时系统共振幅值最大;射流系统发生组合共振响应时,激励频率与流体刚度波动频率的组合频率对系统响应的影响与流体脉动频率有关;主共振和组合共振将恶化系统的动力学行为。本项研究可为深入探索自适应炮头射流系统的动力学特性,优化不同工况环境下的设计参数提供理论依据。     

基于外差式随机共振的涡街频率检测方法

涡街频率检测是涡街流量计的关键技术问题,也是当前的研究热点.分析非线性双稳系统在噪声和单一频率信号、多频率信号作用下的随机共振特性,将外差式频谱分析与随机共振原理相结合,提出基于外差式随机共振的涡街频率检测方法.理论分析、数值仿真和试验结果表明,含噪的涡街信号通过随机共振能有效地提高涡街信号信噪比,准确获取涡街频率.该方法在涡街频率检测中的应用是可行和有效的,为提高涡街流量计现场适应性及小流量弱涡街信号频率检测提供了一种新的方法.     

带的强迫共振与主参数共振实验研究

不考虑轴向运动,采用两端简支的模型以阶次跟踪方法实验研究铜带的强迫共振和主参数共振。从谱阵图中易发现强迫共振频率等于横向激励频率,主参数共振频率为铜带张力波动频率的1/2,并且两种共振振幅峰值频率均大于铜带的固有频率,这与理论分析相符,为后续研究工作提供了实验依据。     

小流量涡街信号的随机共振特性与频率检测方法

分析了小流量涡街信号特性,探讨了信号与随机共振系统的阈值和克莱默斯逃逸率之间的关系,提出一种基于幅值和频率双重调制的随机共振方法,用于检测小流量涡街信号的频率。该方法以外加控制信号的幅值和频率作为调控变量,采用多参数控制方式使小流量涡街信号产生随机共振。经数值仿真及实验研究,表明该方法能将小流量涡街信号通过随机共振得到增强,有效获取涡街频率,实现小流量测量,为随机共振的控制和微弱信号的检测提供一种新方法。     

考虑构件偏心时磁场调制型磁齿轮传动系统的主共振

考虑磁场调制型磁齿轮传动系统中内转子偏心,建立了基于时变磁耦合刚度的参数振动动力学模型,采用多尺度法推导了内转子上转矩激励频率接近系统固有频率时的共振响应计算公式,分析了算例系统的主共振响应。结果表明:当转矩波动频率接近系统不同阶固有频率时,产生的共振振幅相差较大,且共振响应中只有一个自由度的振幅很大,而其他自由度振幅很小;系统响应中激励频率占主导成分,而激励频率与磁耦合刚度波动频率的组合频率对系统响应影响很小。较大的主共振会严重恶化系统动力学行为,对其进行研究可以为深入探索该系统的动力学特性、优化不同工况环境下的设计参数提供理论依据。     

模态共振液压脉动衰减器仿真与实验研究

为了衰减液压脉动,提出一种模态共振液压脉动衰减器结构,利用共振板的多模态拓宽衰减频率范围。当液压油的脉动频率接近共振板的某一阶固有频率时,就会激发相应的振型将该频率成分的脉动能量最大限度衰减掉。选择合适的材质,合理设计共振板的结构使共振板固有频率分布得均匀而密集,使模态共振脉动衰减器具备广谱消声效果。用LMS Virtual.Lab对模态共振液压脉动衰减器进行声振耦合模态计算,并进行样机试验测试。研究结果表明:模态共振液压脉动衰减器结构紧凑、消声频率广、消声效果良好。     

电子皮带秤的共振频率分析及解决方法

在电子皮带秤的安装现场周围,有时存在固定频率的振动源导致电子皮带秤产生受迫振动.当振动源频率和皮带秤固有频率接近时,皮带秤将发生共振.本文讨论杠杆式皮带秤的振动模型、共振频率分析及解决共振的办法.解决皮带秤共振现象的一种方法就是要消除振动源、采取隔振措施或改变振动源的振动频率;另一种方法就是要改变皮带秤秤体的固有频率.     

GP-周期势随机共振在无线电弱信号检测中的应用

无线电信号在传播过程中,由于复杂的环境和外界噪声导致信号接收的不确定性。为有效增强检测的特征频率,减少干扰频率成分,更清晰地识别目标频率特征,将周期势系统势阱模型与Gaussian Potential(GP)势阱模型相结合提出GP-周期势随机共振系统,令待测信号、噪声及随机共振系统产生最佳的共振效果,对无线电弱信号进行检测,并与传统随机共振系统和周期势随机共振系统检测无线电弱信号的效果进行对比。实验结果表明,GP-周期势随机共振系统在无线电弱信号检测中识别目标频率更清晰,频谱更平坦,和传统随机共振系统相比对噪声的利用率更高。     

机电集成电磁蜗杆传动系统参数振动响应

针对机电集成电磁蜗杆传动系统中啮合磁极数的周期性变化规律,推导了电磁啮合刚度傅里叶级数形式的表达式,建立了该机电耦合系统参数振动模型及其相应的线性时变微分方程。采用多尺度法推导了该系统自由振动近似解析解,给出了系统包含固有频率及固有频率与啮合频率的组合频率成分的自由振动、主共振、组合共振时域及频域响应曲线。结果表明：系统发生组合共振时的主导频率为系统的固有频率,系统的组合共振振幅随谐波次数增大而递减。     

基于随机共振的任意大频率微弱信号检测方法研究

通用非线性随机共振系统(参数a=1,b=1)在检测微弱信号时受小频率参数和弱信号幅度的约束,给实际应用带来了很大困难.针对这一情况,提出了一种能够检测大频率微弱信号的随机共振检测方法,通过调整系数k改变非线性参数6,使输入弱信号满足共振幅度要求;调整系数R改变非线性参数a、6,将共振频率提高R倍,从而实现了大频率微弱信号的随机共振.通过理论分析和数值仿真,研究了系数k和R的调整方法、步长等,构建了一种可实现的大频率微弱信号检测方法.     

电控喷油器强度的有限元计算分析

喷油器是电控喷油系统中最基本、最关键的元件之一,它接受电子控制单元（ECU）发出的控制指令,完成喷油过程,以实现满足系统要求的各种不同喷油规律。由于喷油器的工作油压很高,为保证其工作的安全性和可靠性,检验其结构参数是否合理,有必要对其进行有限元强度计算。本文采用大型CAD软件I-DEAS Master SeriesTM,对喷油器体进行了强度计算和应变分析。对喷油器的结构参数和材料选择进行了调整和优化,为喷油器的结构设计和材料选用提供理论指导,提高设计成功率,降低开发成本。     

汽油发动机电控喷油器结构改进设计

为进一步提高汽油发动机电控喷油器的性能,建立了喷油器工作过程的数学模型,分析了影响喷油器电磁响应特性的关键因素,对喷油器核心运动件即衔铁-球阀组件的结构进行了改进设计,改进后喷油器运动件质量减少10％.通过有限元分析软件分析验证表明,结构改进后能够保持喷油器电磁力基本不变,并能满足耐久性要求.对比试验测试结果表明,由于运动件质量减少,改进后的喷油器开启与关闭滞后时间与原喷油器相比分别缩短11％和8％,动态响应性能得到了提高.     

Elimination of Fuel Pressure Fluctuation and Multi-injection Fuel Mass Deviation of High Pressure Common-rail Fuel Injection System

The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot,but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently.In this paper,a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation.Linear model of the improved high pressure common-rail system(HPCRS)including injector,the pipe connecting common-rail with injector and the hydraulic filter is built.Fuel pressure fluctuation at injector inlet,on which frequency domain analysis is conducted through fast Fourier transformation,is acquired at different target pressure and different damping hole diameter experimentally.The linear model is validated and can predict the natural frequencies of the system.Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model,and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists.Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally,and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter.The amplitude of main injection fuel mass deviation can be reduced by 73%at most under pilot-main injection mode,and the amplitude of post injection fuel mass deviation can be reduced by 92%at most under main-post injection mode.Fuel mass of a single injection increases with the increasing of the damping hole diameter.The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.     

柴油机喷油阀碰撞分析

喷油器是柴油机燃油供给系统中实现燃油喷射的重要部件,然而在其工作中,针阀常与针阀体产发生碰撞,产生很大应力,针阀体工作寿命相当有限。以某款柴油机的喷油器为例,在CATIA中建立喷油器的三维模型,导入Hypermesh中进行模型的简化和网格的划分,利用Hypermesh和ABAQUS的接口,在ABAQUS的显式动力学有限元模块进行瞬态力学分析,模拟出喷油器中针阀与针阀体的碰撞过程,发现与应力波理论推导出的经验公式计算出的应力值基本接近。采用有限元方法对喷油器进行力学分析,有利于喷油器的改进设计。     

高压共轨喷油器测试电路设计及其检测平台开发研究

为了检测高压共轨喷油器的工作性能,改善汽车尾气的排放质量,对高压共轨喷油器的动作原理及其检测波形进行了分析,并对喷油器的喷油量进行了计算。采用PLC技术,利用PWM方法,设计了一种喷油器检测电路及其测试平台,可以检测各类型号的高压共轨喷油器在怠速及全油门状态下的喷油状况,对其喷油质量给出判定,该平台也可进行喷油嘴驱动电路的优化研究。     

Optical investigation of the fuel injector influence in a PFI spark ignition engine for two-wheel vehicles

This paper describes the results obtained in a port fuel injection spark-ignition (PFI SI) engine by optical diagnostics during the fuel injection and the combustion process. A research optical engine was equipped with the fuel injection system, the head and the exhaust device of a commercial 250 cc engine for scooters and small motorcycles. Two injectors were tested: standard 3-hole injector that equipped the real reference engine and a 12-hole injector. The intake manifold was modified to allow the visualization of the fuel injection using an endoscopic system coupled with CCD camera. Size and number of the fuel droplets were evaluated through an image processing procedure. The cycle resolved visualization and chemiluminescence allowed to follow the combustion process from the spark ignition to the exhaust phase. All the optical data were correlated with engine parameters and exhaust emissions. The effect of the fuel injector type on deposits formed by fuel accumulation and dripping on the intake valves steams and seats was investigated. In particular, the evolution of diffusion-controlled flames due to the fuel deposits burning was analyzed. These flames were principally located near the intake valves, and they persisted well after the normal combustion event. The consequences were the formation and emission of soot and unburned hydrocarbons. The multi-hole injector helped reducing wall wetting and deposit formation so that the emission characteristic can be improved. The use of 12-hole injector allowed a more homogeneous distribution for a lower time of fuel droplets in the intake manifold than the 3-hole injector. This study also investigated the detailed physical/chemical phenomena to figure out reasons for the improvement using optical measurements.     

一种带正温度系数材料加热的柴油喷油器

为了改善发动机冷起动性能和排放,提出了一种用正温度系数（PTC）材料加热柴油喷油器内燃油的方法,并设计了相应的喷油器。为研究喷油器内PTC材料加热柴油的过程,试验选择了居里温度为75℃的陶瓷基PTC材料为加热元件,测量了不同电压下用PTC陶瓷加热柴油的温度变化规律。试验表明,用PTC材料对柴油进行预热,可以将柴油加热到居里点附近,实现自限温加热;同时,将PTC材料成功应用于喷油器内还需要进行相关的基础研究和解决工艺问题。     

Fuel spray dynamic characteristics of GDI high pressure injection system

In order to improve the fuel consumption and exhaust emission for gasoline engines,gasoline direct injection (GDI) system is spotlighted to solve these requirements.Thus,many researchers focus on the i...     

An investigation on the spray characteristics of DME with variation of ambient pressure using the common rail fuel injection system

We investigated the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system were used since DME has compressibility and vaporization at atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed for spray shape, penetration length, and spray angle at the six nozzle holes. There are two types of injectors: 0.166 mm diameter and 0.250 mm diameter. The ambient pressure, which was based on gage pressure, was 0, 2.5, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 to 70 MPa. By comparing with the common injector, using the converted injector it was shown that the DME injection quantity was increased 127% but it didn??t have the same low heating value. Both the common and converted injectors had symmetric spray shapes. In case of converted injector, there were asymmetrical spray shapes until 1.2 ms, but after 1.2 ms the spray shapes were symmetric. Also, the converted injector had shorter penetration length and wider spray angle than the common injector.     

An experimental study on the spray characteristics of a dual-orifice type swirl injector at low fuel temperatures

The objective of this study is to investigate the effects of fuel temperature on the spray characteristics of a dual-orifice type swirl injector used in a gas turbine. The major parameters affecting spray characteristics are fuel temperature and injection pressure entering into the injector. In this study, the spray characteristics of a dual-orifice type swirl injector are investigated by varying fuel temperature from — 30°C to 120°C and injection pressure from 0.29 to 0.69 MPa. Two kinds of fuel having different surface tension and viscosity are chosen as atomizing fluids. As a result, injection instability occurs in the low fuel temperature range due to icing phenomenon and fuel property change with a decrease of fuel temperature. As the injection pressure increases, the range of kinematic viscosity for stable atomization becomes wider. The properties controlling the SMD of spray is substantially different according to the fuel temperature range.