Browsing by Author "Narayana, M"

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item: Article-Full-text
Adaptive linear prediction for optimal control of wind turbines
(IEEE, 2017) Narayana, M; Sunderland, KM; Putrus, G; Conlon, MF
In order to obtain maximum power output of a Wind Energy Conversion System (WECS), the rotor speed needs to be optimised for a particular wind speed. However, due to inherent inertia, the rotor of a WECS cannot react instantaneously according to wind speed variations. As a consequence, the performance of the system and consequently the wind energy conversion capability of the rotor are negatively affected. This study considers the use of a time series Adaptive Linear Prediction (ALP) technique as a means to improve the performance and conversion efficiency of wind4 turbines. The ALP technique is introduced as a real time control reference to improve optimal control of wind turbines. In this study, a wind turbine emulator is developed to evaluate the performance of the predictive control strategy. In this regard, the ALP reference control method was applied as a means to control the torque/speed of the emulator. The results show that the employment of a predictive technique increases energy yield by almost 5%.
item: Conference-Abstract
Adaptive model predictive control with successive linearization for distillate composition control in batch distillation
Mendis, P; Wickramasinghe, C; Narayana, M; Bayer, C
This paper investigates the application of adaptive model predictive control (MPC) with successive linearization for the control of top product purity of a batch distillation column. Adaptive MPC with successive linearization can overcome the prediction inaccuracies associated with linearization of highly non-linear and dynamic mathematical model of a batch distillation column, with a lower computational load than nonlinear MPC. A binary mixture of methanol and water was selected to demonstrate the controller development, and its performance was investigated by varying MPC tuning parameters in the MATLAB/Simulink simulation environment. Results indicated that the choice of tuning parameters had a considerable influence on the MPC’s ability to track a constant set-point for the output. With the correct choice of tuning parameters, however, it is possible for the controller to track a constant set-point. The present approach is compared with nonlinear MPC in order to gain a quantitative understanding on accuracy and computational effort.
item: Conference-Abstract
Adaptive prediction of power fluctuations from a Wind Turbine at Kalpitiya Area in Sri Lanka
Narayana, M; Witharana, S
Hydro power is the major renewable energy contributor to the national grid in Sri Lanka amounting to 48% of the total installed capacity. Further expansion of hydropower however is limited due to environmental and resource constraints. Meanwhile the demand for electricity is estimated to rise at an annual rate of 8% - 10% prompting the need to find alternative power options. The wind energy has been identified as a promising candidate to generate electricity in Sri Lanka. However for a reliable integration of wind energy the volatile nature of wind has to be understood. Wind speedtime series data typically exhibit autocorrelation, which can be defined as the degree of dependence on preceding values. Generally, statistical models and neural network techniques being used for time series analysis. Present study shows how an adaptive digital filter can serve as a modelling, forecasting and monitoring technique, and, how they contribute to a successful integration of wind power into the national grid. The north-western region of Kalpitiya has been identified as one of the potential location for wind power generation in the country. This study also predicts power generation and investigates power fluctuations for grid integrations of a commercially available wind turbine installed in Kalpitiya area by using measured wind speeds and performance of the wind turbine.
item: Conference-Full-text
Analysis and derivation of optimum operating conditions of lapple cyclone separator by using cfd
(IEEE, 2016-04) De Silva, MSM; Narayana, M; Jayasekara, AGBP; Bandara, HMND; Amarasinghe, YWR
Cyclones are one of the most extensively used gas cleaning equipment in the industry. Current empirical model based cyclone designs and performance prediction have many limitations due to complex nature of the gas-solid flow field. Computational Fluid Dynamic (CFD) simulation could be useful to predict cyclone performance as an alternative approach. This paper represents a CFD simulation of a Lapple cyclone separator using OpenFOAM software. The flow field of cyclone was obtained by using Reynolds averaged Navier-Stockes equations combine with k-ε closure model. Flow field pressure and velocity distribution were obtained from the simulation and they were compared with the literature to evaluate the model validity. Multiphase Particle in Cell (MPPIC) method was used for the particle modeling, in which particle interactions with other particles were represented by models. Tangential gas velocity profile, pressure drop and particulate collection efficiency of cyclone obtained from the model were comparable to experimental results in the literature. Optimum values for inlet gas-solid velocity and particulate loading rate for the Lapple cyclone were obtained by this analysis. Pressure drop variation with gas-solid inlet velocity which has been obtained by this analysis could be useful to minimize the energy requirement while maintaining the required collection efficiency.
item: Thesis-Full-text
Analysis and optimization of cyclone separators by using rans
De silva, MSM; Narayana, M
Many types of particulate matter collectors are used in the industry to separate particulate matter from the gaseous streams. Among various type of particulate collectors, cyclone separators are one of the most extensively used gas cleaning equipment because ofthey are inexpensive; easier to fabricate, and could be designed to stand under harsh operating conditions. Due to this extensive usage in the industry, many theoretical and experimental studies have been carried out and empirical models were developed to predict cyclone separator’s most important operational parameters. These models have many limitations of illustrating flow behavior properly due to the complex nature of the cyclone gas-solid flow behavior. Computational Fluid Dynamic (CFD) simulation could be useful to predict cyclone performance as an alternative approach. This work represents a CFD simulation of a Lapple cyclone separator using OpenFOAM software. Cyclone simulations have been carried out using turbulence models associated with the Reynolds Average Navier Stokes (RANS) equations. Multiphase Particle in Cell (MPPIC) method was used for the particle modeling, in which particle interactions with other particles were represented by models. The perditions of simulations have been compared both mutually and to literature in terms of cyclone pressure drop, gas-solid flow pattern and collection efficiency. RANS model fairly predict the gas-solid flow pattern of the cyclone. Pressure drop and collection efficiency of cyclone well fitted to the experimental results in the literature. Optimum values for inlet gas-solid velocity and particulate loading rate for the Lapple cyclone were obtained by RANS analysis. Pressure drop variation with gassolid inlet velocity which has been obtained by this analysis could be useful to minimize the energy requirement while maintaining the required collection efficiency.
item: Thesis-Full-text
Analysis of wood chip combustion system for hot air generation in the industrial drying process
(2015-10-19) Rajika, JKAT; Narayana, M
A two-dimensional steady state packed bed CFD model is developed for the combustion of wood chip in a moving grate.The model is validated using an industrial moving bed hot air generator used in Tea industry.Various empirical models have used for thermophysical property modeling.For this purpose free-board region of the hot air generator is also simulated including volatile reactions and turbulent combustion.Modeling and simulation carried out using open source CFD software OpenFOAM.Radiation heat incident on the packed bed is unknown and it is assumed in the first packed bed simulation.Therefore, CFD simulation involves number of iterative runs of the packed bed model and free board model to obtain the radiation temperature incident on packed bed due to free board heat.According to the validation results the developed packed bed model can be used to predict temperature of the packed bed wood chip combustion of thermally thin wood particles. The gas compositions could not be validated using the model.Further improvements to the model have suggested.
item: Conference-Abstract
Applicability of environmental and physical planning laws to the construction industry in Sri Lanka
(2018-05) Rathnasinghe, IP; Wijeivickrama, MKCS; Abeynayake, M; Narayana, M; Chathuranga, D
The development of construction industry should be aligned within the legal boundaries of a country. Generally, complications in the environmental and physical planning directly impact the construction activities and triggered to disputes and conflicts. Thus, the legal considerations related to Environmental and Physical Planning Laws may directly affect the construction industry. Henceforth, this research aims to evaluate the applicability of Environmental and Physical Planning Law to the construc-tion industry in Sri Lanka. Accordingly, the mixed research ap-proach was selected by steering both questionnaire survey and experts' opinion survey. The findings reveal that some aspects of the existing Environmental and Physical Planning Law areas should be amended in order to meet current industry challenges. Moreover, there are some provisions in the existing law which have failed due to the improper implementation process. Therefore, the research manifests that the aforementioned laws should be properly monitored and amended according to the industry requirements.
item: Conference-Abstract
Bed shrinkage in packed bed biomass combustion
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2016-04) Adassuriya, TL; Jayatillake, KDKY; Nupehewa, JM; Kaluhendiwela, YC; Narayana, M; Jayasekara, AGBP; Amarasinghe, YWR
This paper focuses on evaluating shrinkage of a biomass packed bed. A laboratory scale packed bed is designed to conduct experiments in batch mode. Different types of biomass i.e. Ginisiriya, coconut shells and rubber are used for the packed bed to study the behavior of bed shrinkage. The model uses inlet air stream at room temperature as the gasifying medium and a fixed batch of biomass. Ignition of the biomass batch is initiated by an external heat source. Further operation is maintained by the own heat emitted by combustion reactions, until the whole batch is finished. As the time goes height of the packed bed is decreasing due the shrinkage of the bed. Empirical data obtained from this model can be used to evaluate the bed shrinkage and temperature variations in solid phase and gas phase with time.
item: Conference-Abstract
Biodiesel production using rendered oil from waste chicken skin
(Department of Chemical & Process Engineering University of Moratuwa., 2023-08-17) Wickramathilaka, A; Gunarathne, S; Rathnayake, M; Walpalage, S; Gunawardena, S; Narayana, M; Gunasekera, M
Biodiesel is a prominent biofuel that can be locally produced from various feedstock options to replace/blend with diesel. This study explores the feasibility of biodiesel production from waste chicken skin in the laboratory-scale. The average yield of rendered oil obtained from waste chicken skin is 280 mL/kg. The rendered chicken skin oil displayed minimal impurities and exhibited a yellow color, demonstrating the presence of natural pigments. To determine the suitability of the rendered oil for biodiesel production, experimental tests were conducted to measure the Free Fatty Acid (FFA) content and Acid Value (AV). The FFA content was found to be less than 3%, indicating the possibility of direct conversion of rendered chicken skin oil into biodiesel via transesterification. The biodiesel yield obtained from the rendered chicken skin oil samples ranged with an average yield of 43%. The results demonstrate the potential of waste chicken skin as a viable feedstock for local biodiesel production. While density and net calorific value are nearly the same, biodiesel samples display significantly lower kinematic viscosity, suggesting improved flow characteristics while reporting a higher flash point than that of diesel, indicating the requirement of a higher ignition temperature. Further, an economic analysis was also performed to evaluate the overall production cost of a scaled-up biodiesel production plant from waste chicken skin. This study demonstrates the potential of waste chicken skin as a viable feedstock for biodiesel production and supports important findings for future developments of commercial scale biodiesel production from locally available bio-waste/food-waste sources.
item: Conference-Extended-Abstract
Biomass gasification in a bubbling fluidized bed reactor
(Department of Chemical and Process Engineering, University of Moratuwa, 2019) Dodawatta, DVBK; Indula, UD; Maddumage, MDRS; Wijesekere, GAT; Narayana, M; Rathnasiri, PG
The effect of secondary air flow rate and particle size on the combustion temperature inside the bubbling fluidized bed reactor was reviewed. The experiments were carried out for four particle sizes with varied secondary air flow rates. From the results it was evident that the secondary air flow rate has a larger impact on the temperature of the freeboard zone. The temperature profiles show that a maximum temperature is achievable when the magnitude of the secondary air flow rate is lower than that of the primary air flow rate. It was concluded that desired maximum temperature can be achieved regardless of the particle size through the optimum secondary air flow rates for each particle size.
item: Conference-Extended-Abstract
Carbonization of urban bio waste in Sri Lanka
(Department of Chemical and Process Engineering, University of Moratuwa, 2019) Bandara, AMHS; Gunathilaka, T; Pieirs, KCA; Narayana, M; Rathnasiri, PG
The research scope was set to study the compatibility of applying torrefaction for bio-waste of Sri Lanka. For this purpose, it was decided to analyze the before and after torrefaction properties of a sample with Sri Lankan municipal solid bio waste composition; with the use of ultimate and proximate analysis. A laboratory scale reactor was made to undertake the conventional torrefaction process with N2 purging. Heat was supplied for the reactor using a 3 kW heating coil and insulations were made around the reactor to minimize the heat loss during the torrefaction. The reactor temperature was controlled to maintain at desired temperature with a maximum of 350OC using LabVIEW software.
item: Thesis-Full-text
CFD modeling of a centrifuge for oil - water separation
Thilakarathna, HGSM; Narayana, M
Centrifugation is an efficient, economical and environmentally friendly method to remove un-desirable water content from oil and water mixtures and separate out the desired oil content.Moreover, the disc stack centrifuges are widely used for separating liquids of different densi-ties and applied in industrial coconut oil clarification as well.The main focus of this research work is to model the fluid flow inside the Westfalia discstack centrifuge using Ansys Fluent and identify the flow behavior. With the availability of thelimited computer hardware facility, the model has been run without the discs to avoid com-plexities. In the developed 3 dimensional model, the fluid dynamic behavior of the multiphaseflow has been considered and modeled using the VOF multiphase model available in fluent.The step by step procedure of the model development has been discussed such as the veryfirst stage of geometry selection, drawing and importing to the fluent, mesh generation, allsolution set ups and even the two stage simulation procedure.The simulation results of this research work provides an out line of the resulted flow param-eters of velocity and pressure profiles, turbulent effects such as turbulence intensity, turbulentkinetic energy, and specific dissipation rate and also the phase volume fractions which havebeen saved in every critical stage of the simulation process. Despite the phase volume fractionwhich has been experimentally validated, all other results were theoretically validated.CFD modeling of flow behavior inside the centrifuges is not a popular topic among theresearchers due to the complex flow patterns and the requirement of advanced computer hard-ware facility. However this research work provides a platform to model the similar flow be-haviors and even to model the same case including the discs.
item: Conference-Full-text
Characterising the drying behaviour of microwave assisted drying of coconut chips
(IEEE, 2021-07) Muhammed Aadhil, MFH; Amarasinghe, ADUS; Narayana, M; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Drying is the most critical unit operation in coconut oil and desiccated coconut industry. Different technologies are used for drying coconut chips and hot air drying is the most popular method. Microwave (MW) drying has gained attention in many process industries due to its faceted benefits. This study examines the critical parameters governing the microwave drying of coconut chips. Sliced coconut chips of 1cm×1cm×1cm were used. The effect of the two independent variables MW Power (100 W, 180 W, 300 W) and Mass Loading rate (20 g, 40 g, 60 g, 80 g, 100 g) on three response variables, moisture content, drying time and drying rate was examined. Air velocity of 0.6 m/s was circulated in the drying chamber to ensure convective mass transfer. The ratio of Microwave Power to the Mass Loading was found to define two distinct regions for selecting the mass loading for a given microwave power. At high MW power to mass loadings, the total drying time was found to be constant against the mass loading while at low MW power to mass loadings, the total drying time was found to increase with the mass loading for a given MW power. Considering both statistical conformity ( R2>0.995 , SSE and RMSE close to zero) and the simplicity together, Page model was identified as the best thin layer drying model for describing the Microwave Assisted Air Drying of coconut chips.
item: Conference-Abstract
ChemECon 2023 Solutions worth spreading (Pre Text)
(Department of Chemical & Process Engineering University of Moratuwa., 2023-08-17) Walpalage, S; Gunawardena, S; Narayana, M; Gunasekera, M
Proceedings of ChemECon 2023 Solutions worth spreading
item: Conference-Abstract
Comparative study of energy potential of mango pit as biomass with coconut shell Ginisyria & mixture in laboratory scale developed updraft gasifier
Amin, M; Narayana, M
Biomass energy is getting peak level attention from last few years in terms of improvement in technology to increase energy conversion efficiency. The world is facing energy issue this biomass energy can play vital role due to its abundant availability in different sectors such as domestic waste, agricultural waste, industrial waste etc. Many of the biomass contains a lot of energy and then it needs attention to be utilized in proper manner. One of the major technologies to produce energy from biomass is thermochemical conversion. Gasification is thermochemical conversion process ' is of much interest in which carbonaceous material is converted into different valuable products by application of heat in suitable designed unit. This study aims to develop 25 KW updraft gasifier (70% thermal efficiency) with gas cleaning unit for performance analysis of reactor by testing mango pit as new biomass material and its comparison with coconut shell ginisyria and mixture of biomass (50%,25%,25% coconut shell, mango shell & ginisyria respectively). Properties of feed materials such as ultimate and proximate analysis were done for each kind. Performance was analyzed in developed unit without packing plate vs. with packing plate (which was introduced about 609.6 mm above the grate in chamber) in terms of producer gas composition and its variation with equivalent ratio, lower heating . value (MJ/Nm3) of product gas for the said materials and their comparison. Results indicate that that producer gas can be generated from mango pit and its lower heating value was calculated as 3 3 5(MJ/Nm3) at equivalent ratio of 0.2while in comparison with others materials coconut shell has more energy contents while mixture has lowest energy contents among all. With increase m air velocity as ER approaches 0.25 LHV of product for all biomass materials was observed m reducmg trend .Overall performance of unit gives satisfactory results arc! from analysis it identify that mango pit is competitive candidate as biomass.
item: Article-Full-text
A comprehensive two dimensional Computational Fluid Dynamics model for an updraft biomass gasifier
(Elsevier, 2016) Fernando, N; Narayana, M
This study focuses on developing a dynamic two dimensional Computational Fluid Dynamics (CFD) model of a moving bed updraft biomass gasifier. The model uses inlet air at room temperature as the gasifying medium and a fixed batch of biomass. The biomass batch is initially ignited by a heat source which is removed after a certain amount of time. This model operates by the heat emitted by combustion reactions, until the fuel is finished. Since the operation is batch wise, model is transient and takes into consideration the effect of bed movement as a result of shrinkage. The CFD model is capable of simulating the movement of interface between solid packed bed and gas free board and this motion is also presented. The model is validated by comparing the simulation results with experimental data obtained from a laboratory scale updraft gasifier operated in batch mode with Gliricidia. The developed model is used to find the optimum air flow rate that maximizes the cumulative CO production. It is found that from the simulation study for the particular experimental gasifier, a flow rate of 7 m3/h maximizes the CO production. The maximum cumulative CO production was 6.4 m3 for a 28 kg batch of Gliricidia
item: Thesis-Full-text
Computational fluid dynamics modeling of thermo-chemical processes in an updraft biomass gasifier
(2016-09-15) Fernando, N; Narayana, M
Biomass is recently gaining popularity in industry as a promising source of renewable energy. Gasification of biomass is a major thermal conversion method to improve the efficiency of raw biomass fuel. It is a process by which biomass is partially oxidized to produce a combustible gas named Syngas; a mixture of carbon monoxide, hydrogen and methane. Although the gasification technology is used throughout the history and there are a large number of gasification plants worldwide, their smooth operation remains questionable. This is due to a lack of understanding of proper design criteria. In order to gain insights to optimal design parameters, mathematical models and computer simulations based performance analysis can be used. Recently Computational Fluid Dynamics (CFD) analysis has been applied by many researchers as a tool for optimizing packed bed processes including gasification process. In this research study, a two dimensional CFD model has been developed for an updraft biomass gasifier. The model uses air as the gasifying medium and a fixed batch of biomass. The model is capable of tracking the movement of interface between solid packed bed and gas free board due to bed shrinkage. The two phase model is developed using the Euler-Euler approach. The model consists of several sub models, including reaction models, turbulence model for packed bed gas phase and free board, a radiation model for solid phase, a bed shrinkage model, and interphase heat transfer models. The final mathematical model is converted into a numerical model using open source CFD tool OpenFOAM. Required code was developed by using C++ language in OpenFOAM package, including all the relevant differential equations and procedures in the CFD model. To validate the CFD model, simulation results for gas temperature and gas compositions are compared against experimental gas temperatures and compositions measured from an operational laboratory gasifier. The validated model is used to perform air flow rate optimization. A series of CFD simulations were performed for air flow rates ranging from 3 m3/hr to 10 m3/hr for a computational geometry corresponding to the experimental gasifier and cumulative CO was calculated. It is found that cumulative CO production maximized at 7 m3/hr airflow rate. The maximum cumulative CO volume was 6.4 m3.
item: Conference-Abstract
Condition monitoring system for outdoor insulators
(2018-05) Karunarathna, IMAM; Karunathilaka, KTL; Wanasinghe, WMHM; Sampath, GKL; Lucas, JR; Samarasinghe, R; Narayana, M; Chathuranga, D
High Voltage insulators are vital components in transmission and distribution systems in a power network. Most of the insulators are used in open air applications where they are subjected to different environment conditions. Exposure to these different weather conditions and contaminations determine their performance as insulators. Condition monitoring ot power line insulators is an important requirement for asset management engineers in a power network in order to maintain a healthy power system. There are several techniques that have been introduced to fulfil this requirement. One ot the techniques ot measuring surface leakage current is introduced here. This paper highlights the concepts of measuring surface leakage current for insulators under contaminated conditions. Results show that the surface leakage current is closely related to the insulator condition.
item: Article-Full-text
The cost of energy associated with micro wind generation: International case studies of rural and urban installations
(Elsevier, 2016) Sunderland, KM; Narayana, M; Putrus, G; Conlon, MF; McDonald, S
National targets for increased renewable energy are common-place internationally and small/microgeneration may help achieve such goals. Energy yields from such technologies however, are very location and site specific. In rural environments, the average wind speed is relatively high and the homogeneous landscape promotes laminar air flow and stable (relatively) wind direction. In urban environments however, the wind resource has lower mean wind speeds and increased levels of atmospheric turbulence due to heterogeneous surface forms. This paper discusses the associated costs per unit of electricity generated by micro wind energy conversion systems from the perspective of both urban and rural locations, with three case studies that consider the potential and financial viability for such systems. The case studies ascertain the cost of energy associated with a standard HAWT (horizontal axis wind turbine), in terms of exemplar rural and urban locations. Sri Lanka, Ireland and the UK, are prioritised as countries that have progressive, conservative and ambitious goals respectively towards the integration of micro-generation. LCOE (Levelized cost of energy) analyses in this regard, offers a contextualised viability assessment that is applicable in decision making relating to economic incentive application or in the determination of suitable feed-in tariff rates.
item: Conference-Abstract
Development of a liquid level controller by using digital signal processing system
Kumara, GKGS; Narayana, M
Liquid level control is vital in the chemical and process industries. Some processes need liquids to be pumped to a certain desired level. This paper presents development of Proportional-Integral-Derivative (PID) controller for controlling the desired liquid level of a tank. Three conventional techniques of PID tuning that is Ziegler-Nichols, Z-N, method and Good Gain, G-G, method and Trial & Error method will be tested in order to obtain the PID controller parameters. Simulink is used to build the model and the liquid level of a tank is controlled by using TI Delfino F28355 Experimental kit which is a digital signal processing (DSP) control board. Arduino UNO board is used for real time data acquisition which is used to plot required graphs in Labview. The performance of the system is evaluated in terms of Rise Time (Tr), Settling Time (Ts), Steady State Error (SSE) and Overshoot (OS).