Steady-state Performance Parameters Research Articles

Numerical analysis of finite bearing operating under non-Newtonian lubricant and flow turbulence effect

The purpose of this work is to evaluate the combined influence of turbulence and shear-thinning/shear-thickening lubricant on the steady-state characteristics of hydrodynamic journal bearings. The modified Navier–Stokes equation for linear turbulence and non-Newtonian (shear-thinning as well as shear-thickening aspect) lubricants are solved using a finite element method to acquire load capacity, attitude angle, friction coefficient variable, total oil flow, and temperature rise variable for distinct combined values of the flow behavior index and Reynolds number. This work utilizes the Navier–Stokes equation with Ng–Pan's linear turbulence and shear-thinning/shear-thickening lubricant models, which is very helpful in predicting the performance characteristics of hydrodynamic bearings under harsh industrial operating conditions. The results show that the combined presence of non-Newtonian lubricant and turbulence in the flow significantly affects the steady-state performance parameters of such type of bearing compared to existence of individual presence of turbulence and non-Newtonian lubricant in the clearance space. This work helped to provide better insight into the operation of journal bearings in a severe environment owing to the high speed and changes in the nature of lubricant.

Aircraft pitch control design using LQG controller based on genetic algorithm

Designing a robust aircraft control system used to achieve a good tracking performance and stable dynamic behavior against working disturbances problem has attracted attention of control engineers. In this paper, a pitch angle control system for aircraft is designed utilizing liner quadratic Gaussian (LQG) optimal controller technique with a numerical tuning algorithm method in the longitudinal plane through cruising stage. Main design approach of LQG controller includes obtaining best weighting matrices values using trial and error method that consumes effort and takes more time, in addition, there is no guarantees to obtain optimum values for weighting matrices elements. In this research, genetic algorithm (GA) is used to optimize the state and control weighting matrices and determine best values for their elements. The proposed traditional and optimized LQG pitch controller schemes are implemented utilizing Matlab simulation tool and their performance are presented and compared based on transient and steady state performance parameters. The simulation results reveal the ability of the optimized GA_LQG controller to reject the effect of the noises in the aircraft system dynamic and achieve a good and stable tracking performance compared with that of the conventional LQG pitch control system.

Power Control Approach for PV Panel System Based on PSO and INC Optimization Algorithms

The main purpose of this paper is to obtain optimum power from a Photovoltaic (PV) panel and deliver it to a load system under standard irradiance and temperature weather conditions. Standard Boost DC-DC converters and bidirectional Buck-Boost DC-DC converters work as voltage controlling units for the power provided from the PV panel, which is used to charge the battery and supply suitable voltage signal to AC load. MPPT technique, based on two control algorithms, Particle swarm optimization (PSO) and Incremental Conductance (INC), is used to extract maximum power from the solar cells. Matlab/ Simulink environment is adopted to simulate the proposed PV power system. Simulation results are presented and analyzed based on transient and steady-state performance parameters. The performance results of the PV array system under the Standard Test Conditions (STC) showed that the INC-MPPT control algorithm can provide a

Simulation Study on the Performance and Emission Parameters of a Marine Diesel Engine

Development of intelligent ships requires marine diesel engine simulation models of high accuracy and fast response. In addition, with advent of tighter shipping air emissions regulations, such models are required to have emission prediction capabilities. In this article, such a model was developed and validated for a 30,000-ton bulk carrier main engine using MATLAB/Simulink. The simulation is based on mean value model, which predicts both the steady-state and dynamic performance of the engine. The results show that the steady-state performance parameters of the main engine are predicted within 2.2% error, and the exhaust emissions parameters are predicted within 7% error as compared to the bench test data from the engine manufacturer. The Maximum Continuous Rating (MCR) points at 100%, 75%, 50% and 25% of the E3 duty cycle were investigated with emphasis according to the diesel propulsion characteristics. In dynamic simulation, it is found that the compressor pressure fluctuation is greater than that of the exhaust pressure with the load variation. Furthermore, the compressor and the exhaust pipe have a similar temperature drop value (about 60 K) when the engine load changes from 100% to 50% MCR, and the exhaust pipe temperature fluctuation is more significant when the load varies from 50% to 25% MCR. The above results show the model’s good transient capability in simulating the dynamic characteristics of the engine. This model can be used especially for the development and control of marine diesel engines in intelligent ships as well as training-oriented marine engine and ship simulators.

Effect of using hybrid nano lubricant on the thermo-hydrodynamic performance of two lobe journal bearings

Due to the wide range of journal bearings applications in the industrial machine, significant efforts have been made by tribology researchers to improve their performance in recent years. Designing new bearings geometry and using lubricants with new chemical compounds including additives are the most common solutions proposed to enhance the performance of journal bearing supports. New advancements in nanotechnology and producing the various types of nano particles have provided the chance of upgrading the properties of commercial lubricants. According to the different effect of nano fluids on the performance of mechanical systems corresponding to their composition, today they are used to achieve different goals in lubrication systems. Upgrading the steady state performance parameters including load carrying capacity, attitude angle, surface cooling and effective viscosity are among the expected results of applying nano lubricant in journal bearings. So, in this study the performance of hydrodynamic two lobe journal bearings lubricated with SiO2-multiwall carbon nano tubes /SAE40 hybrid nano fluid is presented considering the thermal effects. For this purpose, the governing Reynolds and energy equations as well as the equation of heat transfer in bearing shell are modified based on the properties of assumed rotor-bearing system. Then the effects of solid volume fraction of nano particles on the performance of two lobe bearings are studied for different amount of bearing noncircularity. The results indicate that upgrading the solid volume fraction of added nano particle to the SAE40 base oil, enhances the lubricant pressure distribution, load carrying capacity, and lubricant effective viscosity. Further, by increasing the solid volume fraction, the attitude angle and temperature of lubricant and rotor-bearing surfaces experience a decreasing trend. Generally, it's obvious from the results that choosing the appropriate solid volume fraction of SiO2-multiwall carbon nano tubes in hybrid nano oil composition, especially for high value of preload factor, can improve the performance of two lobe bearings.

Experimental performance evaluation of an R1234yf automobile air conditioning system employing an internal heat exchanger

A bench-top automobile air conditioning (AAC) system using a thermostatic expansion valve was developed. The system was equipped with a coaxial internal heat exchanger (HEX) and charged with R1234yf, a new refrigerant used as an alternative to R134a. The system was tested at the compressor speeds ranging between 1000 rpm and 2600 rpm with increments of 400 rpm. For each compressor speed, the air temperatures at the evaporator and condenser inlets were concurrently changed between 30 °C and 40 °C with increments of 5 °C. The system was operated for the cases of employing and not employing the HEX, and totally 30 test runs were performed. Then, the first law of thermodynamics was applied to the system components to evaluate various steady state performance parameters. The considered parameters were the refrigerant mass flow rate, evaporating temperature, cooling capacity, compressor power, coefficient of performance (COP), condenser heat dissipation rate and discharge temperature of the compressor. It was determined that the experimental system employing the HEX yielded on average 0.8 °C lower evaporating temperature, 2.2% higher cooling capacity, 2.0% lower compressor power and 3.0% higher COP values relative to the system not employing the HEX. These findings reveal that the use of HEX causes a better system performance in terms of the cooling capacity, compressor power and COP. Consequently, the performance of R1234yf AAC systems can be improved with the use of HEX, and thus, the AAC systems using R1234yf can be more competitive with those using R134a.

Effect of couple-stress parameter on the steady state performance parameters of two-lobe journal bearing operating with non-Newtonian lubricant

In the present work, steady state performance parameters have been obtained for two-lobe journal bearing, operating with non-Newtonian lubricant. Krieger-Dougherty model for viscosity is used to find the effective viscosity for a given concentration of nanoparticle in base lubricant. Different steady state performance parameters are determined from solution of Reynolds equation modified for couple-stress model. Results indicate a significant increase in load carrying capacity and flow co-efficient while there is a decrease in friction variable.

Influence of micro-groove attributes on frictional power loss and load-carrying capacity of hybrid thrust bearing

PurposeMicro-surface texturing is emerging as a possible way to enhance the tribological performance of hydrodynamic fluid film bearings. In view of this, numerical simulations are carried out to examine the influence of surface texture on performance of hybrid thrust bearing system. This paper aims to determine optimum attributes of micro-grooves for thrust bearing operating in hybrid mode.Design/methodology/approachAn iterative source code based on finite element formulation of Reynolds equation has been developed to numerically simulate flow of lubricant through the bearing. Mass-conserving algorithm based on Jakobsson–Floberg–Olsson (JFO) condition has been used to numerically capture cavitation phenomenon in the bearing. Gauss Siedel method has been used to obtain steady state performance parameters of the bearings.FindingsA parametric study has been performed to improve the load supporting capacity of the bearing by optimizing micro-groove attributes and configuration. It is noticed that use of full-section micro-groove is beneficial in improving the efficiency of bearing by enhancing the fluid film reaction and reducing the film frictional power losses.Originality/valueThis study is helpful in examining the usefulness of micro-groove textured surfaces in hybrid thrust bearing applications.

Performance Analysis of PI and SMC Controlled Zeta Converter

This paper presents the design and analysis of DC-DC Zeta converter operating in the continuous conduction mode to regulate the output voltage of the converter for automotive battery recharge applications. The state space analysis of the converter is derived to obtain the transfer function of the converter. The presented DC-DC converter exhibits the non-linearity due to the presence of energy storage elements and degrades the performance of the converter. Therefore, this paper proposes a non-linear cascaded Proportional -Integral Sliding Mode Controller (PI-SMC) to improve the performance of the converter. PI-SMC Controller contains PI Controller in the outer loop for voltage regulation and an inner fast acting SMC Controller for current shaping. The PI controller is tuned by Root locus and Routh Hurwitz criterion and the steady state performance parameters are obtained for the PI-SMC Controlled Zeta converter. MATLAB/SIMULINK results are presented for Set point tracking of the controller. The results shows that the steady state performance indices such as Integral Absolute Error (IAE) and Integral Time Absolute Error (ITE) are significantly enhanced for the converter using the proposed cascaded control scheme compared to the conventional PI controller.

Analysis and design of IMC-PI Controller with faster set point tracking and disturbance rejection for Interleaved DC-DC SEPIC converter based Power Factor Correction

This paper deals with the internal model controller (IMC) - proportional integral (PI) controller for interleaved DC-DC single ended primary inductance converter (SEPIC)-based power factor correction (PFC). The transfer function of the proposed converter exhibits seventh order dynamics with complex right hand plane (RHP) poles and zeros. IMC-based PI controller is used to achieve perfect control since it contains the internal model of the process implicitly or explicitly. The cascade control strategy is implemented for the proposed converter with IMC-based PI controller as inner current and outer voltage controller. The dynamic and steady state performance parameters of the proposed scheme are evaluated using MATLAB/Simulink software. The simulation results reveal that the proposed scheme offers excellent stability characteristics, robustness, faster set point tracking and disturbance rejection for various uncertainties in the process as compared to conventional PI controller.

Performance analysis of stand-alone six-phase induction generator using heuristic algorithms

The paper exhibits the performance analysis of six-phase self-excited induction generator for stand-alone wind energy generation system. The analysis is based essentially on solving the nonlinear equivalent circuit of the SP-SEIG, which is to find the per-unit frequency F and the magnetizing reactance Xm minimizing the determinant of the nodal admittance matrix Y instead of solving two non-linear equations with two unknowns. Hence, the equation-solving problem is converted to an optimization problem. The obtained minimum yields the adequate magnetizing reactance and frequency which will be used subsequently to compute the self-excitation process requirements in terms of the prime mover speed, the excitation capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. In this work, the analysis is performed using three different global search algorithms, the genetic algorithm (GA), the particle swarm optimization (PSO) technique and the Taguchi optimization method (TM). A study of some simulation results is carried out using MatLab to compare between these three algorithms in terms of accuracy and guaranteed convergence in finding the minimum of the admittance.

The Off-Design Performance Simulation of Marine Gas Turbine Based on Optimum Scheduling of Variable Stator Vanes

As one of the antisurge techniques, the adjusting scheme of VSV under off-design conditions has a significant impact on the performance of gas turbines. In this paper, the one-dimensional characteristic of the compressor calculation program is embedded into the zero-dimensional overall gas turbine model, which replaces the original compressor characteristic module. Based on the assembling relationship of the actual components of the marine gas turbine, the architecture of the modular model library is designed, and an integrated simulation platform of marine gas turbine is developed by using MATLAB/GUI software. The influence of the first 3 rows of variable stator vanes of the 9-stage axial compressor working alone on the performance of the compressor at different speeds and different angles was analyzed by the HARIKA compressor characteristic calculation program. Taking the economics and stability of the gas turbine as the optimization objective, the optimization of the first three-stage stator vanes regulation schemes under different working conditions was carried out. The steady-state performance parameters under each working condition of gas turbine of power generation with or without variable stator vane mode were calculated. The study results can provide references for the adjusting scheme of VSV under gas turbine off-design conditions operating process.

Performance analysis of a finite noncircular floating ring bearing in turbulent flow regime

The present paper investigates the turbulence effect on the steady-state performance of a new variety of journal bearing, i.e. the noncircular floating ring bearing. This particular bearing consists of the journal, floating ring, as well as lower and upper lobes. The shaft and the floating ring are cylindrical while surfaces of the bearing are noncircular. The classical Navier–Stokes equations and continuity equation in cylindrical coordinates are being satisfactorily adapted with the linearized turbulent lubrication model of Ng and Pan. These improved equations are being solved by the finite element method using Galerkin’s technique and an appropriate iteration strategy. The proposed bearing has a length-to-diameter ratio of 1 and operates over different values of the ratio of clearances (i.e. 0.70 and 1.30). The steady-state performance parameters computed are presented in terms of an inner and outer film eccentricity ratios, load-carrying capacity, attitude angle, speed ratio, friction coefficient variable, oil flow, and temperature rise variable for the Reynolds number up to 9000. The present analysis predicts better performance in the turbulent regime as compared to the laminar regime for the noncircular floating ring bearing.

Impact of Number of Poles on the Steady-State Performance of Induction Motors

A simplified analysis of influence of pole pairs on the steady-state behavior of induction motors is presented. The analysis makes simplifying assumptions to express relationship between key steady-state performance parameters of 2-pole reference motor compared to its multiple pole counterparts. The analysis is performed using considerations of fixed geometrical dimensions on one hand and fixed output power on the other hand. Available manufacturer catalog data of medium voltage (MV) induction machines from one manufacturer are used to evaluate the soundness of the analysis. Also test and catalog data analyses of commercially manufactured low-voltage (LV) machines from different manufacturers are evaluated to determine extent to which they conform to the theoretical considerations of the analyses. The preliminary findings indicate more agreement with the MV motors than the LV motors.

Performance Analysis of Short Journal Bearing under Thin Film Lubrication

The steady state performance analysis of short circular journal bearing is conducted using the viscosity correction model under thin film lubrication conditions. The thickness of adsorbed molecular layers is the most critical factor in studying thin film lubrication, and is the most essential parameter that distinguishes thin film from thick film lubrication analysis. The interaction between the lubricant and the surface within a very narrow gap has been considered. The general Reynolds equation has been derived for calculating thin film lubrication parameters affecting the performance of short circular journal bearing. Investigation for the load carrying capacity, friction force, torque, and power loss for the short circular journal bearing under the consideration of adsorbed layer thickness (2δ) has been carried out. The analysis is carried out for the short bearing approximation (L/D=0.5) using Gumbel’s boundary condition. It has been found that the steady state performance parameters are comparatively higher for short circular journal bearing under the consideration of adsorbed layer thickness than for plain circular journal bearing. The load carrying capability of adsorbed layer thickness considered bearing is observed to be high for the specified operating conditions. This work could promote the understanding and research for the mechanism of the nanoscale thin film lubrication.

Steady State Analysis of an Isolated Self-Excited Dual Three-Phase Induction Generator for Renewable Energy

In this paper modelling and analysis in autonomous mode of dual three-phase induction generator (DTPIG) with a new algorithm have been done. We develop the steady state model of a dual three-phase self-excited induction generator for stand-alone renewable generation dispensing with the segregating real and imaginary components of the complex impedance of the induction generator. The obtained admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Steady state performances and characteristics of different configurations are clearly examined and compared. The analytical results are found to be in good agreement with experimental results.

Analysis of the self-excited induction generator steady state performance using a new efficient algorithm

The paper presents the application of DIRECT algorithm to analyse the performance of the Self-excited induction generator (SEIG). To the author best knowledge, this is the first attempt to apply it to such a problem. DIRECT algorithm is used to minimize the induction generator's admittance without the need to separate it into its real and imaginary parts. No initial guess is required as it needs only the upper and lower values of the unknown variables which are easily determined. The obtained minimum admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Very good agreement between predicted results and experimental measurements is achieved.

Control approach for high sensitivity cardiopulmonary exercise testing during stimulated cycle ergometry in spinal cord injured subjects

Aim People with complete lower-limb paralysis resulting from spinal cord injury (SCI) can perform cycle ergometry by means of functional electrical stimulation. Here, we propose and evaluate new exercise testing methods for estimation of cardiopulmonary performance parameters during this form of exercise. Methods We utilised a customised ergometer incorporating feedback control of stimulated exercise workrate and cycling cadence. This allowed the imposition of arbitrary workrate profiles with high precision with the potential for improved sensitivity in exercise testing. New incremental exercise test (IET) and step exercise test (SET) protocols for determination of peak and steady-state performance parameters were assessed. Results The IET protocol allowed reliable determination of the ventilatory threshold, peak workrate and oxygen uptake-workrate relationship, but gave unrepresentative peak oxygen uptake values and highly variable measures of oxygen uptake kinetics. The SET protocol gave reliable estimation of steady-state oxygen uptake and metabolic efficiency of constant load exercise, but high variability in the estimation of oxygen uptake kinetics. Conclusion The feedback-controlled testbed and the new IET and SET protocols have the potential for estimation of cardiopulmonary performance parameters with improved sensitivity during stimulated cycle ergometry in subjects with SCI.

Effect of plasma confinement and impurity level upon the performance of a D-T burning tokamak experimental power reactor

The effect of uncertainties in plasma confinement and impurity concentration upon the performance of a D-T burning tokamak experiment power reactor is analysed. Steady-state performance parameters are established for ignition and beam-driven modes as a function of nτ and impurity concentration. The deleterious effect of wall-sputtered impurities on the burn cycle dynamics is examined for several potential first-wall materials. The effect of different confinement scaling laws — trapped-ion mode and pseudoclassical — on the burn cycle dynamics is studie.