Changduk Kong

Component Map Generation of a Gas Turbine Using Genetic Algorithms

In order to estimate the precise performance of the existing gas turbine engine, the component maps with more realistic performance characteristics are needed. Because the component maps are the engine manufacturers propriety obtained from very expensive experimental tests, they are not provided to the customers, generally. Therefore, because the engineers, who are working the performance simulation, have been mostly relying on component maps scaled from the similar existing maps, the accuracy of the performance analysis using the scaled maps may be relatively lower than that using the real component maps. Therefore, a component map generation method using experimental data and the genetic algorithms are newly proposed in this study. The engine test unit to be used for map generation has a free power turbine type small turboshaft engine. In order to generate the performance map for compressor of this engine, after obtaining engine performance data through experimental tests, and then the third order equations, which have relationships with the mass flow function, the pressure ratio, and the isentropic efficiency as to the engine rotational speed, were derived by using the genetic algorithms. A steady-state performance analysis was performed with the generated maps of the compressor by the commercial gas turbine performance analysis program GASTURB (Kurzke, 2001). In order to verify the proposed scheme, the experimental data for verification were compared with performance analysis results using traditional scaled component maps and performance analysis results using a generated compressor map by genetic algorithms (GAs). In comparison, it was found that the analysis results using the generated map by GAs were well agreed with experimental data. Therefore, it was confirmed that the component maps can be generated from the experimental data by using GAs and it may be considered that the more realistic component maps can be obtained if more various conditions and accurate sensors would be used.

Components map generation of gas turbine engine using genetic algorithms and engine performance deck data

In order to estimate the gas turbine engine performance precisely, the component maps containing their own performance characteristics should be used. Because the components map is an engine manufacturer’s propriety obtained from many experimental tests with high cost, they are not provided to the customer generally. Some scaling methods for gas turbine component maps using experimental data or data partially given by engine manufacturers had been proposed in a previous study. Among them the map generation method using experimental data and genetic algorithms had showed the possibility of composing the component maps from some random test data. However not only does this method need more experimental data to obtain more realistic component maps but it also requires some more calculation time to treat the additional random test data by the component map generation program. Moreover some unnecessary test data may introduced to generate inaccuracy in component maps. The map generation method called the system identification method using partially given data from the engine manufacturer (Kong and Ki, 2003, ASME J. Eng. Gas Turbines Power, 125, 958–979) can improve the traditional scaling methods by multiplying the scaling factors at design point to off-design point data of the original performance maps, but some reference map data at off-design points should be needed. In this study a component map generation method, which may identify the component map conversely from some calculation results of a performance deck provided by the engine manufacturer using the genetic algorithms, was newly proposed to overcome the previous difficulties. As a demonstration example for this study, the PW206C turbo shaft engine for the tilt rotor type smart unmanned aerial vehicle which has been developed by Korea Aerospace Research Institute was used. In order to verify the proposed method, steady-state performance analysis results using the newly generated component maps were compared with them performed by the Estimated Engine Performance Program deck provided by the engine manufacturer. The performance results using the identified maps were also compared with them using the traditional scaling method. In this investigation, it was found that the newly proposed map generation method would be more effective than the traditional scaling method and the methods explained above.

Size effect on compressive strength of T300/924C carbon fibre-epoxy laminates

Abstract The effect of specimen gauge section (length×width) was investigated on the compressive behaviour of a T300/924C [45/-45/0/90]3s carbon fibre-epoxy laminate. A modified Imperial College compression test fixture was used together with an antibuckling device to test 3 mm thick specimens with a 30×30, 50×50, 70×70, and 90×90 mm gauge length by width section. In all cases failure was sudden and occurred mainly within the gauge length. Post-failure examination suggests that 0° fibre microbuckling is the critical damage mechanism that causes final failure. This is a matrix dominated failure mode and its triggering depends very much on initial fibre waviness. It is suggested that manufacturing plays a significant role in determining the compressive strength and may be more important as the section thickness of the composite increases. Additionally, compressive tests on specimens with an open hole are performed. The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material. It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor. This suggests that the material is not ideally brittle and some stress relief occurs around the hole. X-ray radiography reveals that damage in the form of fibre microbuckling and delamination initiates at the edge of the hole at ~80% of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2-3 mm (depending on specimen geometry). This damage growth and failure are analysed by a linear cohesive zone model. Using the independently measured laminate parameters of compressive unnotched strength and in plane fracture toughness the model predicts successfully the notched strength as a function of hole size and width.

Performance simulation of a turboprop engine for basic trainer

A performance simulation program for the turboprop engine (PT6A-62), which is the power plant of the first Korean indigenous basic trainer KT-1, was developed for performance prediction, development of an EHMS (Engine Health Monitoring System) and the flight simulator. Characteristics of components including compressors, turbines, power turbines and the constant speed propeller were required for the steady state and transient performance analysis with on and off design point analysis. In most cases, these were substituted for what scaled from similar engine components’ characteristics with the scaling law. The developed program was evaluated with the performance data provided by the engine manufacturer and with analysis results of GASTURB program, which is well known for the performance simulation of gas turbines. Performance parameters such as mass flow rate, compressor pressure ratio, fuel flow rate, specific fuel consumption and turbine inlet temperature were discussed to evaluate validity of the developed program at various cases. The first case was the sea level static standard condition and other cases were considered with various altitudes, flight velocities and part loads with the range between idle and 105% rotational speed of the gas generator. In the transient analysis, the Continuity of Mass Flow Method was utilized under the condition that mass stored between components is ignored and the flow compatibility is satisfied, and the Modified Euler Method was used for integration of the surplus torque. The transient performance analysis for various fuel schedules was performed. When the fuel step increase was considered, the overshoot of the turbine inlet temperature occurred. However, in case of ramp increase of the fuel longer than step increase of the fuel, the overshoot of the turbine inlet temperature was effectively reduced.

A Study on Fault Detection of a Turboshaft Engine Using Neural Network Method

It is not easy to monitor and identify all engine faults and conditions using conventional fault detection approaches like the GPA (Gas Path Analysis) method due to the nature and complexity of the faults. This study therefore focuses on a model based diagnostic method using Neural Network algorithms proposed for fault detection on a turbo shaft engine (PW 206C) selected as the power plant for a tilt rotor type unmanned aerial vehicle (Smart UAV). The model based diagnosis should be performed by a precise performance model. However component maps for the performance model were not provided by the engine manufacturer. Therefore they were generated by a new component map generation method, namely hybrid method using system identification and genetic algorithms that identifies inversely component characteristics from limited performance deck data provided by the engine manufacturer. Performance simulations at different operating conditions were performed on the PW206C turbo shaft engine using SIMULINK. In order to train the proposed BPNN (Back Propagation Neural Network), performance data sets obtained from performance analysis results using various implanted component degradations were used. The trained NN system could reasonably detect the faulted components including the fault pattern and quantity of the study engine at various operating conditions.

Investigation on Design for a 500 W Wind Turbine Composite Blade Considering Impact Damage

Recently wind energy has been alternatively used as a renewable energy resource instead of the mostly used fossil fuels due to their increasing scarcity and environmental issues. This work is to propose a structural design and analysis procedure for development of a 500 W class small wind turbine system which will be applicable to domestic use at a relatively low speed region like Korea. Structural analysis including load case study and stress, deformation, buckling, vibration and fatigue estimation was performed. In addition, the blade should be safe from the impact damage due to FOD (foreign object damage) including bird strikes. MSC Dytran was used to analyze the bird strike phenomenon on the blade, and the applied method, Arbitrary Lagrangian–Eulerian, was evaluated by comparison with the previous study results. Finally, the structural test was carried out and its test results were compared with the estimated results for evaluation of the designed structure.

A Study on Transient Performance Characteristics of the Canard Rotor Wing Type Unmanned Aerial Vehicle Propulsion System During Flight Mode Transition

A propulsion system of the CRW (Canard rotor wing) type UAV (unmanned aerial vehicle) was composed of the turbojet engine, exhaust nozzles (including some tip jet nozzles and a main nozzle), and the duct system (including straight ducts, curved ducts, and master valve). The CRW-type UAV has three different flight modes, such as the rotary wing mode for takeoff and landing, the high-speed forward flight mode with the fixed wing, and the transition flight mode between the previously mentioned two flight modes. In order to evaluate transient performance characteristics of the CRW-type UAV propulsion system during flight mode transition, the propulsion system was modeled using SIMULINK®, which is a user-friendly graphical-user-interface-(GUI) type dynamic analysis tool provided by MATLAB, in this study. The transition flight mode between the rotary wing mode and the fixed wing mode was simulated by considering area variation of the master valve and the main exhaust nozzle. In order to verify acceptability of the main turbojet engine model, performance simulation results using SIMULINK were compared to results using the commercial program GSP. Through this simulation, proper operation of the master valve and the variable area main nozzle can be found for safe flight transition. Therefore, performance characteristics were investigated depending on various angle positions of the master valve.

Modelling of Low Velocity Impact Damage in Laminated Composites

In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

Intelligent performance diagnostics of a gas turbine engine using user‐friendly interface neural networks

In this study, in order to facilitate application of the NNs as well as to provide user‐friendly conditions, a performance diagnostic computer code using MATLAB® was newly proposed. As a result, not only more precise and prompt analysis results can be obtained due to use of the toolbox in MATLAB® on diagnosis and numerical analysis, but also the graphical user interface platform can be realized. The proposed engine diagnostics system is able to train the BPN with each fault pattern and then construct the total training network by assembling the trained BPNs. The database for network learning and test was constructed using a gas turbine performance simulation program. In order to investigate reliability on construction of the database for diagnostic results, an analysis is performed with five combination cases of 40 fault patterns. Finally, a diagnostic application example for the PT6A‐62 turboprop engine is performed using the trained network with the database, which represents the best diagnostic results among test sets.

A Study on Optimal Design of Filament Winding Composite Tower for 2 MW Class Horizontal Axis Wind Turbine Systems

Although the tower of the horizontal axis wind turbine system is a simple structure in comparison with the wind turbine rotor system, the production cost of the tower is about 20-25% of the whole wind turbine system cost. If a composite materials tower is used instead of the existing steel tower, the production cost can be reduced by using of low cost composite materials, simple manufacturing process, easy transportation and easy assembly. However studies on the composite materials towers are very few. In this study a specific structural design procedure for 2 MW class glass/polyester face sheets-sand/ polyester core sandwich composite wind turbine system towers is newly proposed through load case study, trade-off study, optimal structural design and structural analysis. Optimal tower design can minimize both weight and cost. In the structural design of the tower, three kinds of loads such as wind load, blades, nacelle and tower weight and blade aerodynamic drag load should be considered. Initial structural design is carried out using the netting rule and the rule of mixture. Then the structural safety and stability are confirmed using a commercial finite element code, MSC NASTRAN/PATRAN. It is confirmed that the final proposed tower meets the tower design requirements.