Chemical- and Mechanical-Induced Lubrication Mechanisms during Hot Rolling of Titanium Alloys Using a Mixed Graphene-Incorporating Lubricant

Hot rolling of titanium alloy currently is carried out without lubrication because of the surface defects. In order to explore an effective lubrication scheme to reduce friction and wear during hot rolling of titanium alloy, a mixed graphene-incorporating lubricant has been proposed to study its lubrication performance and mechanism. The tribological experiments were carried out by ball-disk friction and wear tester under hot-rolling parameters. Scanning electron microscopy (SEM), X-ray energy spectrum analyzer (EDS), X-ray powder diffractometer (XRD) and Raman analysis were used to analyse the surface and cross-section of the wear marks on the samples after the tribological experiments. The results show that the friction coefficient decreases up to about 35% compared with tests under dry and lubricated conditions. The surface quality of the wear marks is improved significantly after applying the proposed lubricant. The graphene which is embedded in the phosphate film can be effectively applied as a lubricating material to strengthen the lubricating film with less combustion loss at high temperatures. A chemical- and mechanical-induced lubrication mechanism for the hot rolling of titanium sheets has been proposed due to the synergistic lubrication effect of the graphene, ZrO2 nano particles and phosphate. It is of great significance and potential value to apply this proposed lubricant as an effective way to reduce the wear, friction and oxidation during the hot-rolling process of titanium alloy.

Modeling and Efficiency Optimization of Steam Boilers by Employing Neural Networks and Response-Surface Method (RSM)

Boiler efficiency is called to some extent of total thermal energy which can be recovered from the fuel. Boiler efficiency losses are due to four major factors: Dry gas flux, the latent heat of steam in the flue gas, the combustion loss or the loss of unburned fuel, and radiation and convection losses. In this research, the thermal behavior of boilers in gas refinery facilities is studied and their efficiency and their losses are calculated. The main part of this research is comprised of analyzing the effect of various parameters on efficiency such as excess air, fuel moisture, air humidity, fuel and air temperature, the temperature of combustion gases, and thermal value of the fuel. Based on the obtained results, it is possible to analyze and make recommendations for optimizing boilers in the gas refinery complex using response-surface method (RSM).

Modeling and Efficiency Optimization of Steam Boilers by Employing Neural Networks and Response-Surface Method (RSM)

Boiler efficiency is called to some extent of total thermal energy which can be recovered from the fuel. Boiler efficiency losses are due to four major factors: the dry gas flux, the latent heat of steam in the flue gas, the combustion loss or the loss of unburned fuel, radiation and convection losses. In this research, the thermal behavior of boilers in gas refinery facilities is studied and their efficiency and their losses are calculated. The main part of this research is comprised of analyzing the effect of various parameters on efficiency such as excess air, fuel moisture, air humidity, fuel and air temperature, the temperature of combustion gases, and thermal value of the fuel. Based on the obtained results, it is possible to analyze and make recommendations for optimizing boilers in the gas refinery complex using response-surface method (RSM).

Development of Straw Briquette Boiler

According to the specialty of straw briquette combustion, thermodynamic calculating and special processing methods, the special boiler which applies to cornstalk briquettes is designed and made. It has double fire grates which have function of smoke removing. Moreover, the combustion efficiency of this boiler is higher and the incomplete combustion loss of solid and gas is less. The contents of fume, nitrogen oxide and sulfur dioxide in the vent smoke are low enough to accords with national standard requirement. So it will have a splendid future to use straw as the substitute of coal in our country.

A Reduced-Order Through-Flow Program for Choked and Cooled Axial Turbines

A reduced-order through-flow program has been developed at the Lund Institute of Technology. The goal of the work was to develop and verify a program suitable for scientific studies of axial turbines. The program has built-in capability for multiple choked stages, and turbine cooling, as well as flexible modules for state, losses, deviation, and blockage. The code uses Matlab™ as a platform for numerics, pre- and post-processing. The turbine modules are available from the Institute free of charge for scientific use. Matlab is a commercially available mathematical package and is used as a numerical tool by many universities and companies. Today, several codes are available for turbine analysis at different levels. Most of the codes are proprietary and not available outside the companies that have developed them. There are, however, commercially available codes, but the user does not normally have accesses to the source code. This poses serious problems when such codes are used for scientific studies, and open easily modified code is indeed a desirable feature. The present paper describes in detail the calculation methods used to simulate performance of a cooled and choked turbine at off-design conditions. The algorithms necessary for finding the turbine choke point will, for example, be described in detail. The way in which the loss, deviation (including secondary and tip clearance), and blockage are included in a quasi 1-D calculation environment is also presented. The code is suitable for further development (e.g. streamline curvature through-flow), since it is based on modules for e.g. state, combustion, loss, deviation, diffuser, numerics, and in-and output data processing. It is fairly easy to transform the Matlab program into e.g. Fortran. However, the use of the original platform simplifies plotting of turbine characteristics, velocity triangles, etc. The program is validated against test-rig data from an industrial two-stage power turbine.

The Problem of Fuel-oil Ash Deposition in Open-cycle Gas Turbines

The loss of power due to the deposition of fuel-oil ash on the turbine blades at present limits the use of boiler fuels in open-cycle gas turbines, and therefore prevents the more widespread application of this form of prime mover in the marine and industrial fields. The nature and occurrence of the ash-forming constituents are discussed, followed by consideration of the possibilities of removal of these from the oil. There appears to be no solution along these lines nor by removal of the ash from the gas stream. The basic factors controlling deposition of ash are still not fully understood and therefore further experimental work is required. However, a method which gives a considerable reduction in deposition has been discovered. In this, combustion of the fuel droplets is controlled so that each droplet burns down and leaves the combustion chamber as a hard, dry, carbon particle containing an appreciable proportion of the ash. The combustion loss due to this unburnt carbon is less than 1 per cent. Long-term engine tests are now required to assess the practical use of the method. Another means of reducing deposition which appears to offer considerable promise is the use of various additives to the fuel or gas stream. Of those tested the oxides of silicon, zinc, and magnesium were the most effective.