Failure analysis of a heat-resistant stainless steel ring in a gas turbine burner

Journal of Mechanical Science and Technology - Hot gas path components in gas turbines are damaged by several mechanisms due to aggressive environments. In this research, the cracking of an insert...     

Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder

In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic.     

Multi-objective optimization of the engine performance and emissions for a hydrogen/gasoline dual-fuel engine equipped with the port water injection system

Hydrogen is one of the most promising options being considered as the fuel of future. However, injection of hydrogen into modern gasoline fueled engines can cause some issues such as power loss. This study, therefore, aims to address this challenge in a simulated hydrogen/gasoline dual-fueled engine by developing a novel and innovative approach without possible side effects such as NOx increment. To achieve this goal, the impacts of water injection and the start of the combustion (SOC) modification in a gasoline/hydrogen duel fueled engine have been rigorously investigated. In current methodology, an engine is simulated using AVL BOOST software and the model is validated against the experimental data. The Latin Hypercube design of experiments method was employed to determine the design points in 3-dimensional space. Due to the existing trade-off between NOx and BMEP, multi-objective optimization using genetic algorithm (GA) was implemented to determine the optimum values of water injection and SOC in various hydrogen energy shares and the effects of optimum design parameters on the main engine performance and emission parameters were investigated. The results showed that the proposed solution could recover the brake mean effective pressure (BMEP) and in some hydrogen energy shares even increase it above the level of single fueled gasoline engine with the added benefit of there being no increase in NOx compared to the original level. Furthermore, other emissions and engine performance parameters are improved including the engine equivalent Brake specific fuel consumption (BSFC) which was shown to increased up to 4.61%.     

Kinetics of gadolinium extraction with D2EHPA and Cyanex301 using single drop column

The extraction kinetics of Gd(III) from the nitric acid medium using bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex301) and 2-ethylhexyl phosphoric acid (D2EHPA) in kerosene solution were measured by the single drop technique. The influences of hydrogen ion concentration, gadolinium ion concentration, extractant concentration, column height, and nozzle diameter on the extraction rate were investigated. The forward rate equations for the gadolinium extraction with D2EHPA and Cyanex301 were obtained. Based on the experimental results, the forward extraction rate constant was calculated. With the increase of D2EHPA or Cyanex301 concentration, the drop rising diameter and the value of interfacial tension decrease in the studied system, which shows that D2EHPA or Cyanex301 has interfacial activity as a kind of surfactant. Also, the droplet diameter and interfacial tension decrease with the increase of aqueous solution acidity. The experimental results show that the D2EHPA extractant provides faster extraction rate in comparison with Cyanex301 extractant, and it would be useful in industrial continuous extraction process.     

A neuro-fuzzy online fault detection and diagnosis algorithm for nonlinear and dynamic systems

This paper presents a new fault detection and diagnosis approach for nonlinear dynamic plant systems with a neuro-fuzzy based approach to prevent developing of fault as soon as possible. By comparison of plants and neuro-fuzzy estimator outputs in the presence of noise, residual signal is generated and compared with a predefined threshold, the fault can be detected. To diagnose the type, size, time and fault conditions, are used analytical approach and neural network for tracking fault developing online. The neuro-fuzzy nets are compared with some other identification methods in application of power plant gas turbine. Faults are considered in two forms, step, and ramp shape. This work was implemented with real data from gas turbine of Kazeroun (Iran) power plant (Mitsubishi unit) and result is presented to demonstrate the benefits of the proposed method.     

Flooding and drop size in a pulsed disc and doughnut extraction column

The hydrodynamic behavior of a pulsed disc and doughnut column has been investigated using three different systems in the absence of mass transfer. Sauter-mean drop diameter (d₃₂), flooding velocity and holdup at flooding have been measured at different operating conditions. The following operating variables have been studied: pulsation intensity and flow rate of both liquid phases. As expected, smaller mean drop sizes are obtained with the increase of pulsation intensity. The results also show no significant effect of continuous phase flow rate on mean drop size, which increases with increase of dispersed phase flow rate for the operating conditions investigated. A single correlation for the prediction of d₃₂ in the mixer-settler, transition and emulsion regimes of operation is proposed with a mean deviation of 7.32%. The maximum throughput is influenced mainly by pulsation intensity and interfacial tension. Two precise correlations are proposed for predicting flooding velocities in this column. The first is based on operating variables, column geometry, and system physical properties. The second one considers the same variables, except column geometry. Good agreement between prediction and experiments is found for all operating conditions investigated.     

Sweeping Gas Membrane Distillation (SGMD) as an Alternative for Integration of Bioethanol Processing: Study on a Commercial Membrane and Operating Parameters

This article considers the application of the sweeping gas membrane distillation process (SGMD) for direct separation of ethanol-water using a flat sheet PTFE membrane. It also studies the effect of operating parameters including feed concentration, feed temperature, feed flow rate, and sweeping gas flow rate on the permeation flux and selectivity of ethanol/water. The results showed that the increase in feed temperature increases in permeate flux and selectivity. Selectivities of 18.5 to 25 were achieved using dilute feeds within the temperature range of 35 to 55°C. However, by increasing the feed concentration by more than 5 wt.%, the selectivity was decreased. The increase in permeation flux and ethanol selectivity at higher feed flow rates was mainly due to the reduction of polarization effects. Moreover, the PTFE membrane was characterized by AFM. The results showed that the present process could be used as a stand-alone technique for bioethanol process integration.     

Beneficial effects of yttrium on mechanical failure and chemical stability of the passive film in 6061 aluminum alloy

Recent studies demonstrated that oxygen-active elements such as yttrium improved the resistance of some alloys to wear and corrosive wear. In this work, the breakdown of passive film and chemical resistance of the passive film in Y-free and Y-containing 6061 aluminum alloy samples were studied. It was demonstrated that critical load that caused failure of the passive film on Y-containing specimens was higher than Y-free samples. Also, penetration depth showed that indentation resistances of Y-containing samples were less than Y-free samples. Polarization behavior of Y-containing samples was improved in contrast of Y-free samples in water and acid environments. Y-containing samples had more power to stabilize the oxide film and make it more inert to electron transfer. Results showed that there was an optimum yttrium addition for improving the properties of Al 6061. Results showed that the best percent of yttrium addition was between 1.5 and 4% and more than this the properties of alloy did not improved