Modelling the Causal Relationship among Remittances, Exchange Rate, and Monetary Policy in Nigeria

This study examined the relationship and causality that exist between remittance inflows exchange rate and monetary aggregates - money supply, interest rate, and the domestic price level in Nigeria. The Johansen co-integration and the Granger causality techniques were employed. The Johansen co-integration test indicated that long run relationship exist among the variables. The Granger causality test results revealed a unidirectional causality running from money supply (LM2) to remittances (LREM) only at lag one and not in the reverse. In other lags, there was no evidence of causality between the duos. The results also showed that, consistently from lag one to lag five, causality run from exchange rate (LEXR) to LREM and not in reverse direction. Unidirectional causality run from interest rate (INT) to LREM, occurring from lag one to lag four. There was no evidence of causality in any direction between inflation rate (INF) and LREM within these lags. We also found that causality run from exchange rate (LEXR) to money supply (LM2) only at lags one and four and not in the reverse order. Keywords: Remittance Inflows, Exchange Rate, and Monetary Policy.

Effect of working fluid on selection of gas turbine cycle configuration for Gen-IV nuclear power plant system

The cycle configuration of the energy conversion system in a nuclear power plant tends to have a governing effect on the overall performance and acquisition cost. Interestingly, one factor that could greatly affect the design choice of the cycle configuration which may not have been explored extensively in many literatures reviewed is the choice of the working fluid. This paper presents a technical analysis on the effect of working fluid on selection of the cycle arrangement for a Generation IV nuclear power plant. It provides insight on potential performance gains that justifies the benefit for an additional cost of a complex cycle, and how the working fluid can influence this choice. The study identifies candidate working fluid that may be suitable for simple, inter-cooled-recuperated, recuperated and other complex cycles. The results obtained shows that for fluid like carbon dioxide, its optimal performance is achieved above it critical points which will require pressurizing the system or operating at high pressure ratio, hence, it would be suitable for a re-compressed inter-cooled cycle configuration. Similar, for fluid like helium with low molecular weight and high gas properties, the simple cycle configuration seem more realistic for its highest cycle efficiency of 41% and turbomachinery design

Integrated gas turbine system diagnostics: components and sensor faults quantification using artificial neural networks

The role of diagnostic systems in gas turbine operations has changed over the past years from a single support troubleshooting maintenance to a more proactive integrated diagnostic system. This has become so, because detecting and fixing fault(s) on one gas turbine sub-system can trigger false fault(s) indication, on other component(s) of the gas turbine system, due to interrelationships between data obtained to monitor not only the GT single component, but also the integrated components and sensors. Hence, there is need for integration of gas turbine system diagnostics. The purpose of this paper is to present artificial neural network diagnostic system (ANNDS) as an integrated gas turbine system diagnostic tool capable of quantifying gas turbine component and sensor fault. A model based approach which consists of an engine model, and an associated parameter estimation algorithm that predicts the difference between the real engine data and the estimated output data is described in this paper. The ANNDS system was trained to detect, isolate and assess component(s) and sensor fault(s) of a single spool industrial gas turbine GT-PG9171ER. The ANN model was construed with multi-layer feed-forward back propagation network for component fault(s) and auto associative network for sensor fault(s). The diagnostic methodology adopted was a nested network structure, trained to handle specific objective function of detecting, isolating or quantifying faults. The data used for training, and testing purposes were obtained from a non-linear aero-thermodynamic model using PYTHIA; a Cranfield University in-house software. The data set analyzed in this paper represent samples of clean and faulty gas turbine components caused by fouling (0.5% - 6% degradation) and sensor fault(s) due to bias (±1% - ±7%). The results show the capability of ANN to detect, isolate (classification) and quantify multiple faults if properly trained

Nutritional and antioxidant potential of rice flour enriched with kersting’s groundnut (Kerstingiella geocarpa) and lemon pomace

This study was designed to enhance the nutritional quality, antioxidant properties and product utilization potentials of locally produced ‘Igbemo’ rice flour by adding Kersting’s groundnut and lemon pomace. Kersting’s groundnut is an underutilized legume while lemon pomace is a byproduct of lemon utilization; both meant to enhance the protein quality, antioxidant potential and fibre contents of the composite flour. The dependent variables were minerals composition, amino acid profile, antioxidants and antinutrients properties, in-vitro protein digestibility and in-vitro carbohydrate digestibility. The result showed that blends with higher lemon pomace of 10.00 g had the best calcium, iron, potassium and magnesium contents and antioxidant contents, while blends with highest Kersting’s groundnut (20.00 g) had the best zinc content. The anti-nutrients in the blends were generally low and safe for consumption

Feasibility of a helium closed-cycle gas turbine for UAV propulsion

When selecting a design for an unmanned aerial vehicle, the choice of the propulsion system is vital in terms of mission requirements, sustainability, usability, noise, controllability, reliability and technology readiness level (TRL). This study analyses the various propulsion systems used in unmanned aerial vehicles (UAVs), paying particular focus on the closed-cycle propulsion systems. The study also investigates the feasibility of using helium closed-cycle gas turbines for UAV propulsion, highlighting the merits and demerits of helium closed-cycle gas turbines. Some of the advantages mentioned include high payload, low noise and high altitude mission ability; while the major drawbacks include a heat sink, nuclear hazard radiation and the shield weight. A preliminary assessment of the cycle showed that a pressure ratio of 4, turbine entry temperature (TET) of 800 °C and mass flow of 50 kg/s could be used to achieve a lightweight helium closed-cycle gas turbine design for UAV mission considering component design constraints

GT-ACYSS: gas turbine arekret-cycle simulation modelling for training and educational purposes

This paper presents the modelling approach of a multi-purpose simulation tool called GT-ACYSS; which can be utilized for simulation of steady-state and pseudo transient performance of closed-cycle gas turbine plants. The tool analyses the design point performance as a function of component design and performance map characteristics predicted based on multi-fluid map scaling technique. The off-design point is analyzed as a function of design point performance, plant control settings and a wide array of other off-design conditions. GT-ACYSS can be a useful educational tool since it allows the student to monitor gas path properties throughout the cycle without laborious calculations. It allows the user to have flexibility in selection of four different working fluids, and the ability to simulate various single-shaft closed-cycle configurations, as well as the ability to carry out preliminary component sizing of the plant. The modelling approach described in this paper has been verified with case studies and the trends shown appeared to be reasonable when compared with reference data in the open literature, hence, can be utilized to perform independent analyses of any referenced single-shaft closed-cycle gas turbine plants. The results of case studies presented herein demonstrated that the multi-fluid scaling method of components and the algorithm of the steady state analysis were in good agreement for predicting cycle performance parameters (such as efficiency, and output power) with mean deviations from referenced plant data ranging between 0.1% and 1% over wide array of operations

Economic optimization from fleets of aero-derivative gas turbines utilising flared associated gas

Associated gas is been wasted to flaring in some parts of the world. The use of these flared gases for both industrial and economic purposes would be very beneficial. This paper presents the development of a model for optimizing the economic return of fleets of gas turbines utilizing flared associated gas. The paper further analyzed the impact of gas turbine degradation on the optimized divestment times of the redundant engines and the economic use of associated gas. Hypothetical but realistic gas turbines were modeled using the Cranfield University performance simulation tool, TURBOMATCH. In furtherance with the investigation, the Techno-Economic and Environmental Risk Assessment (TERA) framework has been adopted for a broad and multi-dimensional optimization of the economic return from the fleets. The results were employed in three degradation scenarios (optimistic, medium, and pessimistic) within the TERA framework to generate economic models. Genetic Algorithm (GA) in MATLAB was used in carrying out optimization to maximize the economic benefit. The result showed that an increase of 1.0% and 1.6% in the energy and net present value (NPV) respectively of the optimized clean fleet as against the baseline were achieved. The economic performance of the fleets shows the optimized fleet (clean) having the highest NPV of $2.84b and the pessimistic degraded fleet having the least NPV of$2.39b. More results revealed that degradation reduced the NPV of the project by 4.0%, 9.1%, and 15.8% for the three different degradation scenarios. This paper has proposed a model that can be used for the profitable economic utilization of associated gas which would be useful to gas turbine operators and investor

Performance analyses and evaluation of CO2 and N2 as coolants in a recuperated Brayton gas turbine cycle for a Generation IV nuclear reactor power plant

As demands for clean and sustainable energy renew interests in nuclear power to meet future energy demands, Generation IV nuclear reactors are seen as having the potential to provide the improvements required for nuclear power generation. However, for their benefits to be fully realised, it is important to explore the performance of the reactors when coupled to different configurations of closed-cycle gas turbine power conversion systems. The configurations provide variation in performance due to different working fluids over a range of operating pressures and temperatures. The objective of this paper is to undertake analyses at the design and off-design conditions in combination with a recuperated closed-cycle gas turbine and comparing the influence of carbon dioxide and nitrogen as the working fluid in the cycle. The analysis is demonstrated using an in-house tool, which was developed by the authors. The results show that the choice of working fluid controls the range of cycle operating pressures, temperatures and overall performance of the power plant due to the thermodynamic and heat properties of the fluids. The performance results favored the nitrogen working fluid over CO2 due to the behavior CO2 below its critical conditions. The analyses intend to aid the development of cycles for Generation IV NPPs specifically Gas-cooled Fast Reactors (GFRs) and Very High-Temperature Reactors (VHTRs)

Performance simulation to understand the effects of multi-fluid scaling of gas turbine components for Generation IV nuclear power plants

A significant hurdle in the development of performance simulation tools to analyse and evaluate nuclear power plants (NPP) is finding data relating to component performance maps. As a result, Engineers often rely on an estimation approach using various scaling techniques. The purpose of this study is to determine the component characteristics of a closed-cycle gas turbine NPP using existing component maps with corresponding design data. The design data is applied for different working fluids using a multi-fluid scaling approach to adapt data from one component map into another. The multi-fluid scaling technique described herein was developed as an in-house computer simulation tool. This approach makes it easy to theoretically scale existing maps using similar or different working fluids without carrying out a full experimental test or repeating the whole design and development process. The results of selected case studies show a reasonable agreement with available data. The analyses intend to aid the development of cycles for Generation IV NPPs specifically Gas-cooled Fast Reactors (GFRs) and Very High-Temperature Reactors (VHTRs)

Thermodynamic performance and creep life assessment comparing hydrogen- and jet-fueled turbofan aero engine

There is renewed interest in hydrogen as an alternative fuel for aero engines, due to their perceived environmental and performance benefits compared to jet fuel. This paper presents a cycle, thermal performance, energy and creep life assessment of hydrogen compared with jet fuel, using a turbofan aero engine. The turbofan cycle performance was simulated using a code developed by the authors that allows hydrogen and jet fuel to be selected as fuel input. The exergy assessment uses both conservations of energy and mass and the second law of thermodynamics to understand the impact of the fuels on the exergy destruction, exergy efficiency, waste factor ratio, environmental effect factor and sustainability index for a turbofan aero engine. Finally, the study looks at a top-level creep life assessment on the high-pressure turbine hot section influenced by the fuel heating values. This study shows performance (64% reduced fuel flow rate, better SFC) and more extended blade life (15% increase) benefits using liquefied hydrogen fuel, which corresponds with other literary work on the benefits of LH2 over jet fuel. This paper also highlights some drawbacks of hydrogen fuel based on previous research work, and gives recommendations for future work, aimed at maturing the hydrogen fuel concept in aviation