巧换发动机的轴瓦

机手如遇到柴油发动机烧瓦抱轴时,可用下面简便方法更换主轴瓦和连杆瓦,不必拆卸缸盖和活塞连杆组,也不必再调气门间隙。其简便方法是:

微型光发动机

近年来，为满足极限空间的作业和医用的需求，要求现有的技术能够在难以触及的极小空间发挥作用，以此为目的，研究微机械的必要性日趋提高，其研究活动越来越兴盛。尽管微机械的定义还不够明确，但通常是指大小在几毫米到百分之一毫米左右的微小驱动机构。

七天七夜车轮战

几年前,小吴和几位朋友合伙买了一部新东风牌大卡车。大家一路高歌,商量着搞运输做生意。没想到汽车开到陕西和四川交界处的一个小山村前,突然抛锚了。一检查发现是发动机的缸体裂口了,自己无法修理。小吴叫朋友返回该厂换发动机,自己留下来守车。这前不着村后不着店的,可怎么过啊!他灵机一动,想到了自己的一技之长。

自选的舞台好唱戏

自选的舞台好唱戏●吴家文游碧景今年伊始，湖南省会同县邮电局局长李安荣摆设了打破干部职工界限，平等竞争招聘股级干部的“擂台”，经过就职演说、面试问答、职工评议、组织考查，１１名工人竞选上股级管理岗位，８名股级干部保留原职。竞选后几个月以来，会同县局的管...

下半年国产新车:乱花渐欲迷人眼

近年来,国内车市的确“迷了许多人的眼”。层出不穷的新车型、变型车令一些职业汽车销售人员也应接不暇。中国汽车工业正在悄悄地舒展着筋骨,在不知不觉间摆脱了只有“老三家”的尴尬。 经验表明,下半年是汽车工业“最出彩”的季节。今年的下半年情形如何呢?又有哪些车会登上这个舞台?

CJ818高原起降单发失效爬升梯度分析

分析研究大型客机在高原机场的单发失效爬升梯度的理论计算公式,考虑高原温度对计算结果的影响,提出相应的修正公式。以CJ818为例进行模拟计算,当单发失效爬升梯度不能满足适航要求时,针对CJ818飞机的特点,分别提出换装发动机、减小最大起飞升力系数等方法以满足适航要求。并综合考虑换装发动机和减小最大起飞升力系数对飞机结构、重量以及飞行性能等各方面的影响。

Identification of diesel front sound source based on continuous wavelet transform

Acoustic signals from diesel engines contain useful information but also include considerable noise components To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for the characterization of engine acoustics. This paper first reviews CWT characteristics represented by short duration transient signals. Wavelet selection and CWT are then implemented and wavelet transform is used to analyze the major sources of the engine front's exterior radiation sound. The research provides a reliable basis for engineering practice to reduce vehicle sound level. Comparison of the identification results of the measured acoustic signals with the identification results of the measured surface vibration showed good agreement.

Multi-stage optimum design of magazine type automatic tool changer arm

To enhance machining efficiency,tool change time has to be reduced.Thus,for an automatic tool changer attached to a machining center,the tool change time is to be reduced.Also the automatic tool changer is a main part of the machining center as a driving source.The static attributes of the automatic tool changer using the commercial code,ANSYS Workbench V12,were tried to interpret.And the optimum design of automatic tool changer arm was proposed by performing the multi-stage optimum design.The shape optimization of the automatic tool changer was proposed and the result was verified to obtain acceptable improvements.It is possible to obtain an optimized model in which the maximum deformation,maximum stress,and mass are reduced by 10.46%,12.89% and 9.26%,respectively,compared with those of the initial model.Also,the results between conventional method by the design of experiments and proposed method by the multi-stage optimum design method were compared.

Comparison of two types of twin-rotor piston engine mechanisms

A novel twin-rotor piston engine （TRPE） mechanism with high volumetric output and power density was introduced. This new engine comprises an energy conversion system and a differential velocity drive mechanism （DVDM）. Two special geared four-bar mechanisms, DVDM-1 and DVDM-2, were utilized and compared. Based on the closed loop vector method, a mathematical model for position, velocity, and acceleration of the two mechanisms was established. Numerical examples illustrate that the kinematic characteristics were presented. Expression of the displacement and compression ratio of the two engine mechanisms were derived and compared. It is concluded that both DVDM-1 and DVDM-2 adopted in the proposed TRPE with six vane pistons create thirty-six power strokes per revolution of the output shaft, and the summation of two angles covered by each rocker is always 2x/N as the output shaft rotates an angle of x/N. In DVDM-1, the span angle of a vane piston should be designed to be 10.2°, and the compression ratio should be equal to 10; in DVDM-2, the span angle of a vane piston should be designed to be 10.6°, and the compression ratio should be equal to 4.3.

Study on Combination of Engine/Steam Turbine Cycle for Improving the Energy Conversion

This work discusses the combination of two thermodynamic cycles seeking to improve the overall chemical energy conversion rate into mechanical energy. Here one engine operates according a Rankine cycle in order to use part of the thermal energy released to the boundary, i.e., the neighboring atmosphere. The analysis of this combined cycle shows that it might, under proper condition, represent a gain of 1.2% in the overall delivered engine power.

Application of clutch to clutch gear shift technology for a new automatic transmission

For the purpose of engineering development for a new 8-step speed automatic transmission,a simplified dynamic model for this gearbox was established and key parameters which affected the shift quality were analyzed.Aiming at four different shift types,the ideal characteristics of shift clutch and engine control were set up.By using torque estimation method,PI slip control algorithm and engine coordinated control principle,the control model and transmission controller were well developed for three shift phases which included rapid-fill phase,torque phase and inertia phase.The testing environment on the rig and prototype vehicle level was built and the testing results obtained in ultimate condition could verify the accuracy and feasibility of this shift control strategy.The peak jerk during shift process was controlled within ±2 g/s where the smooth gearshift was obtained.The development proposal and algorithm have a high value for engineering application.

Multistage Stack with Multiple Pore Radii Applying the Temperature Gradient to a Thermoacoustic Engine

Conventional thermoacoustic engines have a stack pore radius that is almost constant in the axial direction. Hence, a thermoacoustic engine is expected to improve the energy conversion efficiency using a multistage stack with multiple pore radii. The stack comprises several bundles of numerous narrow tubes with specified pore radii. The optimum pore radius of the stack is determined by the oscillation frequency and the temperature in the stack. Consequently, the suitable pore radius changes in the axial direction, because the temperature gradient exists along the stack axis. Therefore, a multistage stack with multiple pore radii is introduced, which achieves a desired optimum pore radius everywhere in the stack. The energy conversion efficiency of the multistage stack, which was studied experimentally for a straight-tube type thermoacoustic engine, was compared with that of a conventional single-stage stack. In these experiments, the improvement of the energy conversion efficiency was confirmed. A numerical method with the transmittance matrix to include the effect of a multistage stack was used, and good agreement between experimental and numerical results was obtained. The results make a future possibilities for stack design intended to higher thermoacoustic engine efficiency expect.

Research on Direct Torque Control System Based on Induction Motor

The mathematic model of direct torque control (DTC) was deduced. Two simulating models based on the MATLAB & SIMULINK were established. The emphasis is focused on study of the performance difference of the DTC system with stator flux hexagon and circle trajectories. The simulation waveforms of flux, torque and current characters with two flux trajectories were given. Experiments were carried out in an AC drive system based on induction motor and two-level inverter. A dual-CPU structure was used and the communication with two CPUs was obtained by a dual-port RAM in this system.

Numerical Simulation of Heat Exchanger＇s Length＇s Effect in a Thermoacoustic Engine

A numerical study of a standing-wave thermoacoustic engine is presented. The aim of this work is to study the effect of increasing the heat exchangers length on the acoustic power. The analysis of the flow and the prediction of the heat transfer are performed by solving the non linear unsteady Navier-Stocks equations using the finite volume method implemented in -ANSYS CFX- CFD code. The results show an increase in the limit cycle acoustic pressure and power as well as the specific work per cycle with the increase of heat exchangers length.

Flow and heat transfer characteristics of regenerative cooling parallel channel

Due to the complex high-temperature characteristics of hydrocarbon fuel,the research on the long-term working process of parallel channel structure under variable working conditions,especially under high heat-mass ratio,has not been systematically carried out.In this paper,the heat transfer and flow characteristics of related high temperature fuels are studied by using typical engine parallel channel structure.Through numeri⁃cal simulation and systematic experimental verification,the flow and heat transfer characteristics of parallel chan⁃nels under typical working conditions are obtained,and the effectiveness of high-precision calculation method is preliminarily established.It is known that the stable time required for hot start of regenerative cooling engine is about 50 s,and the flow resistance of parallel channel structure first increases and then decreases with the in⁃crease of equivalence ratio(The following equivalence ratio is expressed byΦ),and there is a flow resistance peak in the range ofΦ=0.5~0.8.This is mainly caused by the coupling effect of high temperature physical proper⁃ties,flow rate and pressure of fuel in parallel channels.At the same time,the cooling and heat transfer character⁃istics of parallel channels under some conditions of high heat-mass ratio are obtained,and the main factors affect⁃ing the heat transfer of parallel channels such as improving surface roughness and strengthening heat transfer are mastered.In the experiment,whenΦis less than 0.9,the phenomenon of local heat transfer enhancement and deterioration can be obviously observed,and the temperature rise of local structures exceeds 200℃,which is the risk of structural damage.Therefore,the reliability of long-term parallel channel structure under the condition of high heat-mass ratio should be fully considered in structural design.

Flow Structure and Heat Exchange Analysis in Internal Cooling Channel of Gas Turbine Blade

This paper presents the study of the flow structure and heat transfer,and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade.The investigations focus on heat transfer and aerodynamic measurements in the channel,which is an accurate representation of the configuration used in aeroengines.Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models.It is important to note that real engine passages do not have perfect rectangular cross sections,but include coiner fillet,ribs with fillet radii and special orientation.Therefore,this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

十年历练,非凡直-10

“霹雳火”直-10,军龄已有十年。十年来,直-10作为后起之秀,从未放弃成为世界一流武装直升机的梦想。它换装发动机、增设装甲,苦练低空空战、高原驻训等各顶绝技。直-10内外兼修,总体实力在世界先进武装直升机中跻身前三!向“霹雳火”致敬!

旧机车获得新生

美国Progress Rail Service公司与诺福克南方铁路公司共同证明,减少机车排放对环境影响的途径不只有一种。两家公司联合开发了换装了动力装置的PR43C型机车,目前已有3台该型机车投入使用。