Large Heavy Duty Research Articles

Milling stability for slowly varying parameters

In order to predict the quality and the stability properties of milling processes, the relevant dynamics reduced to the cutting edges needs to be known. However, the dynamics varies through the workspace along the tool path during a given machining operation. This is the case for large heavy duty milling operations, where the main source of the relevant dynamics is related to the otherwise slowly varying machine structure rather than to the fairly steady milling tool dynamics. The effect of slowly varying dynamic parameters is presented for milling stability when the cutting process takes place in a region of the work space where the steady-state cutting would change from stable to unstable. After the separation of the slow and fast time scales, the governing non-autonomous delay differential equation is frozen in slow-time in order to determine the time-periodic stationary cutting solution of the milling operation for different parameters. The loss of stability is predicted from the correction to the time-periodic frozen time solution, for which we obtained non-autonomous equation for the accumulated growth over the slow-time. The growth shows loss of stability with a shift on the parameters compared to the static parameter solution.

Sensors Based Measurement Techniques of Fuel Injection and Ignition Characteristics of Diesel Sprays in DI Combustion System

Innovative sensor based measurement techniques like needle lift sensor, photo (optical) sensor and piezoresistive pressure transmitter are introduced and used to measure the injection and combustion characteristics in direct injection combustion system. Present experimental study is carried out in the constant volume combustion chamber to study the ignition, combustion and injection characteristics of the solid cone diesel fuel sprays impinging on the hot surface. Hot surface ignition approach has been used to create variety of advanced combustion systems. In the present study, the hot surface temperatures were varied from 623K to 723K. The cylinder air pressures were 20, 30 and 40bar and fuel injection pressures were 100, 200 and 300bar. It is found that ignition delay of fuel sprays get reduced with the rise in injection pressure. The ignition characteristics of sprays much less affected at high fuel injection pressures and high surface temperatures. The fuel injection duration reduces with the increase in fuel injection pressures. The rate of heat release becomes high at high injection pressures and it decreases with the increase in injection duration. It is found that duration of burn/combustion decrease with the increase in injection pressure. The use of various sensors is quite effective, reliable and accurate in measuring the various fuel injection and combustion characteristics. The study simulates the effect of fuel injection system parameters on combustion performance in large heavy duty engines.

Development of a 90°/180° Upender for Large and Heavy Workpiece by Using Airbags-Drived Flipping Worktable

There is a serious security problem in the process of workpieces flipping, which restricts the increase of production capacity in manufacturing process of large workpieces applied in nuclear power equipment. The shapes and characteristics of flipping workpieces were analyzed; the general model of workpieces outer contour was established. The design goals of heavy castings and forgings cold-work turnover mechanism were formulated based on the requirements of turning process, then the basic constraint-face was build and the geometric constraint-model was uniformed. A novelty 3- DOF planar serial mechanism of heavy upender was proposed whose overall configuration consists of three movements, that is roll, mobile, folding turn, which can realize the double function of turning 90 ° and 180 ° of large workpiece as hollow cylindrical, conical and spherical crown three types. On this basis, the airbags-drived flipping worktable was designed; Topological optimization of flipping worktable was further conducted. Its key technology will provide useful ideas and references for the development of large heavy duty positioner and turnover machine with its other related equipment.

The Structural Design of Electrode Materials for High Energy Lithium Batteries

Lithium batteries are used to power a diverse range of applications from small compact devices, such as smart cards and cellular telephones to large heavy duty devices such as uninterrupted power supply units and electric- and hybrid-electric vehicles. This paper briefly reviews the approaches to design advanced materials to replace the lithiated graphite and LiCoO{sub 2} electrodes that dominate today's lithium-ion batteries in order to increase their energy and safety. The technological advantages of lithium batteries are placed in the context of water-based- and high-temperature battery systems.

Natural Gas Decarbonization to Reduce CO2 Emission From Combined Cycles—Part I: Partial Oxidation

This paper discusses novel schemes of combined cycle, where natural gas is chemically treated to remove carbon, rather than being directly used as fuel. Carbon conversion to CO2 is achieved before gas turbine combustion. Therefore CO2 can be removed from fuel (rather than from exhausts, thus utilizing less demanding equipment) and made available for long-term storage, to avoid dispersion toward the atmosphere and the consequent contribution to the greenhouse effect. The strategy here proposed to achieve this goal is natural gas partial oxidation. The second part of the paper will address steam/methane reforming. Partial oxidation is an exothermic oxygen-poor combustion devoted to CO and H2 production. The reaction products are introduced in a multiple stage shift reactor converting CO to CO2. Carbon dioxide is removed by means of physical or chemical absorption processes and made available for storage, after compression and liquefaction. The resulting fuel mainly consists of hydrogen and nitrogen, thus gas turbine exhausts are virtually devoid of CO2. The paper discusses the selection of some important parameters necessary to obtain a sufficient level of conversion in the various reactors (temperature and pressure levels, methane-to-air or methane-to-steam ratios) and their impact on the plant integration and on the thermodynamic efficiency. Overall performance (efficiency, power output, and carbon removal rate) is predicted by means of a computational tool developed by the authors. The results show that a net efficiency of 48.5 percent, with a 90 percent CO2 removal, can be obtained by combined cycles based on large heavy duty machines of the present technological status, either by using chemical or physical absorption.

A Modified Mallory-Cason Staining Procedure for Large Cryosections

The classic Mallory-Cason staining procedure has been modified for application to sections "on tape" obtained from large deep frozen tissue specimens. These 20 microns cryosections are collected on tape from a large heavy duty cryomicrotome. The stained sections provide anatomical details that are not revealed by other techniques. The merit of this procedure is found in the support of modern medical modalities, both for research and educational purposes.

Evolution of the Lipe Hydraseal Self Contained Fluid Clutch

The Lipe Hydraseal is a new fluid clutch concept to transmit engine torque to the transmission more efficiently than previously existing methods. It can be applied to various types of vehicle from passenger cars to large heavy duty trucks or off-road equipment. It offers the smooth coupling, long life and efficiencies of an oil spray clutch without the inherent installation difficulties.