Two-shaft Gas Turbine Research Articles

Power and efficiency optimizations for an open cycle two-shaft gas turbine power plant

In finite-time thermodynamic analyses for various gas turbine cycles, there are two common models: one is closed-cycle model with thermal conductance optimization of heat exchangers, and another is open-cycle model with optimization of pressure drop (PD) distributions. Both of optimization also with searching optimal compressor pressure ratio (PR). This paper focuses on an open-cycle model. A two-shaft open-cycle gas turbine power plant (OCGTPP) is modeled in this paper. Expressions of power output (PP) and thermal conversion efficiency (TCE) are deduced, and these performances are optimized by varying the relative PD and compressor PR. The results show that there exist the optimal values (0.32 and 14.0) of PD and PR which lead to double maximum dimensionless PP (1.75). There also exists an optimal value (0.38) of area allocation ratio which leads to maximum TCE (0.37). Moreover, the performances of three types of gas turbine cycles, such as one-shaft and two-shaft ones, are compared. When the relative pressure drop at the compressor inlet is small, the TCE of third cycle is the biggest one; when this pressure drop is large, the PP of second cycle is the biggest one. The results herein can be applied to guide the preliminary designs of OCGTPPs.

Experimental and Numerical Studies of the Aerodynamics of Stationary Two-Shaft Gas Turbine Exhaust System

In this study, the aerodynamic performance of the exhaust system of a two-shaft gas turbine was investigated experimentally and numerically. The investigation focused on the system “Turbine Stage-Diffuser—Collector Box” and aimed to examine the impact of inlet conditions and geometry particularities on the efficiency of the exhaust system. The experiments were conducted on the Test Ring ET4 (Experimental Turbine-4) at the Peter the Great St.Petersburg Polytechnic University, which was equipped with a special diversion channel to examine the non-axisymmetric outlet of the exhaust duct. The collector box was designed to rotate by 180 degrees around the turbine axis to investigate its impact on the system’s performance. Flow traversing parameters were measured with the five-channel pneumatic pressure probes, and numerical simulations were performed with CFX 15.0. The RANS (Reynolds-averaged Navier–Stokes) equations were closed with the SST (k-ω) turbulence model (Shear Stress Transport model). The study concluded that the RANS SST model predicts the flow in the diffuser before the struts accurately. However, downstream the struts, the CFD (Computer fluid dynamic) results over-predicted the exhaust diffuser pressure recovery coefficient by 14% due to the complex vortex structure of the turbulent flow, which the Averaged Navier–Stokes equations did not resolve. The study highlights the importance of considering the last stage of the turbine, diffuser, and collector box as an integrated system when investigating the aerodynamics of exhaust ducts. The study also emphasizes the impact of geometry and inlet conditions on the exhaust diffuser’s performance and efficiency. The results of this study can be used to optimize the design of the exhaust system of two-shaft gas turbines and improve their thermal efficiency. The integrated approach of combining experimental and numerical methods can provide a detailed and reliable flow picture and can be used for future research in this area.

Off-Design Performance Comparison Between Single and Two-Shaft Engines Part 1—Fixed Geometry

Abstract This paper describes an investigation into the off-design performance comparison of single and two-shaft gas turbine engines. A question that has been asked for a long time is which gas turbine delivers a better thermal efficiency at part load. The authors, notwithstanding their intensive searches, were unable to find a comprehensive answer to this question. A detailed investigation was carried out using a state-of-the-art performance evaluation method and the answer was found to be: It depends! In this work, the performance of two engine configurations is assessed. In the first one, the single-shaft gas turbine operates at constant shaft rotational speed. Thus, the shape of the compressor map rotational speed line will have an important influence on the performance of the engine. To explore the implications of the shape of the speed line, two single-shaft cases are examined. The first case is when the speed line is curved and as the compressor pressure ratio falls, the nondimensional mass flow increases. The second case is when the speed line is vertical and as the compressor pressure ratio falls, the nondimensional mass flow remains constant. In the second configuration, the two-shaft engine, the two shafts can be controlled to operate at different rotational speeds and also varying relationships between the rotational speeds. The part-load operation is characterized by a reduction in the gas generator rotational speed. The tool, which was used in this study, is a 0-D whole engine simulation tool, named Turbomatch. It was developed at Cranfield and it is based on mass and energy balance, carried out through an iterative method, which is based on component maps. These generic, experimentally derived maps are scaled to match the design point of a particular engine before an off-design calculation is performed. The code has been validated against experimental data elsewhere, it has been used extensively for academic purposes and the research activities that have taken place at Cranfield University. For an ideal cycle, the single-shaft engine was found to be a clear winner in terms of part-load thermal efficiency. However, this picture changed when realistic component maps were utilized. The basic cycle and the shape of component maps had a profound influence on the outcome. The authors explored the influence of speed line shapes, levels of component efficiencies, and the variation of these component efficiencies within the operating range. This paper describes how each one of these factors, individually, influences the outcome.

Investigation of the Influence of Gas Turbine Power Stations on the Quality of Electric Energy in the Associated Petroleum Gas Utilization

The problem of the quality of electric energy in the utilization of petroleum gas is considered. The article presents the results of the development of a mathematical description of power supply systems with gas turbine power stations based on two-shaft gas turbine units. The typical power distribution scheme of a gas turbine power station is given. The joint analysis of the generation modes of the gas turbine power station and the detected deviations of the power quality indicators values was carried out. The influence of the used mode on the power quality indicators is determined. As a result, the factors of operation of a gas turbine power station that affects power quality are identified, and recommendations for their elimination are given.

Identification of Two-shaft Gas Turbine Variables Using a Decoupled Multi-model Approach With Genetic Algorithm

In industrial practice, the representation of the dynamics of nonlinear systems by models linking their different operating variables requires an identification procedure to characterize their behavior from experimental data. This article proposes the identification of the variables of a two-shafts gas turbine based on a decoupled multi-model approach with genetic algorithm. Hence the multi-model is determined in the form of a weighted combination of the decoupled linear local state space sub-models, with optimization of an objective cost function in different modes of operation of this machine. This makes it possible to have robust and reliable models using input / output data collected on the examined system, limiting the influence of errors and identification noises.

ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ НЕСТАЦИОНАРНЫХ ПРОЦЕССОВ В КОНТУРЕ ГАЗОВОЙ ТУРБИНЫ РЕАКТОРА ТИПА SSTAR СО СВИНЦОВЫМ ТЕПЛОНОСИТЕЛЕМ

The problem of mathematical and numerical modeling of non-stationary processes in a closed gas turbine installation as part of an energy conversion unit of a lead-cooled reactor is considered. The problem is solved in a fairly General formulation, in which the gas circuit can include an arbitrary number of turbines with gas preheating, an arbitrary number of compressors with gas pre-cooling, as well as a heat exchanger for regenerative gas heating. Variants of both single-shaft and two-shaft gas turbine installations are considered. Point idealization is used when modeling the flow part of the turbine and compressor. Heat and mass transfer in the circuits of lead and gas coolants is described in a one-dimensional approximation. The possibility of mutual phase transformations of a melt-solid phase in the lead coolant is taken into account. Calculation of heat and mass transfer in the circuits is carried out within the single approach, in which the circulation circuit is represented as a set of interconnected heat-hydraulic elements (channels). Integration of the system of heat and mass transfer equations in the contour is performed using a fast scalar sweeping algorithm. The calculation algorithm provides the ability to take into account the sources of impulse and mass at arbitrary nodal points of the contour. This makes it possible to “end-to-end” computation when integrating the system of equations of gas dynamics along a closed loop, taking into account changes in adiabatic pressure drops at the points of turbines and compressors at each time step. The possibility of using the integral form of the momentum equation for modeling heat and mass transfer in a gas circuit is considered. For the SSTAR-type reactor with a lead coolant and a gas-turbine energy conversion cycle, the calculation of an emergency process with a rupture of a hot gas pipeline was performed. It was found that, in contrast to a reactor with a steam-turbine cycle of energy conversion of the BREST type, lead solidification in gas heaters does not occur in this accident. The study results can be used in elaborating the designs of lead cooled reactors and high-temperature gas reactors.

Design point analysis of two-shaft gas turbine engines topped by four-port wave rotors for power generation systems

Wave rotors are rotating equipment designed to exchange energy between high and low enthalpy fluids by means of unsteady pressure waves. In ground power plants, they can be used as topping devices to existing gas turbines aiming to improve their performance characteristics. A four-port wave rotor is an attractive configuration to be integrated into the gas generator of a two-shaft gas turbine, typical for power generation and propulsion systems, by slightly modifying the architecture of existing engines. In particular, in the present article the wave rotor-topped engine utilizes the same compressor, combustion chamber and turbine inlet temperature of the baseline engine. Cycle analysis for two-shaft gas turbine engines topped with four-port wave rotors is studied and their performance at design point is compared to the performance of the baseline engines accordingly. It is concluded that important benefits are obtained with respect to the ones of the baseline engines in terms of specific work and specific fuel consumption. Furthermore calculations by varying the pressure ratio within the wave rotor and the pressure losses in the ducts connecting the wave rotor to the engine's components indicate the effect on performance, for engines with different compressor pressure ratios and turbine inlet temperatures.

A Strong Tracking Filtering Approach for Health Estimation of Marine Gas Turbine Engine

Monitoring and evaluating the health parameters of marine gas turbine engine help in developing predictive control techniques and maintenance schedules. Because the health parameters are unmeasurable, researchers estimate them only based on the available measurement parameters. Kalman filter-based approaches are the most commonly used estimation approaches; however, the conventional Kalman filter-based approaches have a poor robustness to the model uncertainty, and their ability to track the mutation condition is influenced by historical data. Therefore, in this paper, an improved Kalman filter-based algorithm called the strong tracking extended Kalman filter (STEKF) approach is proposed to estimate the gas turbine health parameters. The analytical expressions of Jacobian matrixes are deduced by non-equilibrium point analytical linearization to address the problem of the conventional approaches. The proposed approach was used to estimate the health parameters of a two-shaft marine gas turbine engine in the simulation environment and was compared with the extended Kalman filter (EKF) and the unscented Kalman filter (UKF). The results show that the STEKF approach not only has a computation cost similar to that of the EKF approach but also outperforms the EKF approach when the health parameters change abruptly and the noise mean value is not zero.

Experimental Aerodynamic Investigations of the 100-MW Two-Shaft Gas Turbine Unit Exhaust Duct

The article describes the results from experimental investigations into the exhaust duct aerodynamics of a stationary two-shaft gas turbine unit (GTU) intended for operation in a combined-cycle plant equipped with a heat-recovery steam generator. The experiments were carried out at the Kirillov Turbine Construction Laboratory of Peter the Great Polytechnic University (SPbPU). The aim of investigations was to experimentally determine the 3D flow structure in the diffuser–exhaust hood flow path and its integral characteristics during operation in combination with the topping turbine stage. The pressure recovery factors and the energy loss coefficients in the diffuser and in the exhaust duct are determined. The circumferential and radial distributions of the 3D flow parameters in the diffuser inlet section are presented. Based on the experimental investigation results obtained for the exhaust duct operating jointly with the topping stage, the main energy loss sources in the duct are determined, and recommendations for improving its aerodynamics are given. A comparative analysis of the exhaust duct’s integral aerodynamic characteristics and of the flow structure parameters obtained during the tests with and without the topping stage is carried out. The results obtained from the comparative analysis of the data obtained in the experiments with the connected topping stage and with the isolated exhaust duct were used for working out recommendations on modeling the stream in the flow paths of two-shaft GTU exhaust ducts.

Research on the performance improvement of a two-shaft gas turbine with a variable area nozzle power turbine

Both an increase in atmospheric temperature and a decrease in atmospheric pressure can lead to the degradation of the maximum allowable power output (MAPO) or the thermal efficiency of a gas turbine. In order to reduce these adverse effects, this paper provides a simulated study on the improvement of the MAPO and the variations of the thermal efficiency due to the fuel flow and variable area nozzle control under different atmospheric conditions. Simulation results indicate that the MAPO increases with the power turbine nozzle area, while the thermal efficiency shows a parabola trend. With the same increment of the power turbine nozzle area, the improvement of the MAPO goes up as the atmospheric temperature rises and the decrease of thermal efficiency is alleviated. Analyses show that the slow degradation of the compressor isentropic efficiency is a key factor that enables the MAPO to increase significantly and the thermal efficiency to remain almost constant.

Thermodynamic simulation of two-shaft gas turbine to study invasive weeds optimization and Min-Max controller strategies considering air-cooled blades

Proper estimation of dynamic behavior of gas turbines is essential to control of these systems. This paper investigates a thermodynamic model of two-shaft gas turbines based on thermodynamic principles, component maps and matching equations considering the blade air cooling effects. An iterative method is applied to analyze design point condition and also to evaluate steady states and transient modes. An open loop control procedure is applied to regulate inlet guide vane position. An industrial min-max control strategy is also adopted to adjust proper fuel flow rate value considering physical limits. Moreover, an invasive weed optimization (IWO) algorithm as a proper optimization method is used to find out the optimal gain values of control structure. Finally, the results are analyzed and performance of control structure has been studied in part load conditions.

Dynamic performance simulation and control of gas turbines used for hybrid gas/wind energy applications

The exponential growth of renewable electricity generation has transformed significantly the operating environment of gas turbines. Nowadays, gas turbines operate under transient conditions to support their renewable partners. Gas turbine dynamic performance simulation provides the means for assessing the engine behavior and designing engine controllers that will enable them to fulfill their new operating role.This paper presents a novel gas turbine performance system for representing the nonlinear behavior of a two-shaft gas turbine engine. The developed gas turbine engine model in MATLAB/Simulink environment is capable of simulating both steady state and transient operating conditions, and to facilitate the design of controllers for stable engine operation. Validation of the developed engine model with a gas turbine simulation package confirmed the excellent agreement among all the simulated measurements at transient conditions. The simulated behavior of a hybrid gas/wind power plant enabled the development of an optimized controller for empowering the gas turbine to support the intermittent wind turbines. The time responses of the main parameters of the hybrid gas/wind power plant demonstrated the significant amount of transient conditions that a gas turbine experiences for fulfilling the energy gap imposed by the wind turbines. Finally, the performance comparison of the hybrid power plant to a twin gas turbine power plant highlighted the effective reduction in NOx emissions.

Gas turbine gas-path fault identification using nested artificial neural networks

Purpose The purpose of this paper is to present a quantitative fault diagnostic technique for a two-shaft gas turbine engine applications. Design/methodology/approach Nested artificial neural networks (NANNs) were used to estimate the progressive deterioration of single and multiple gas-path components in terms of mass flow rate and isentropic efficiency indices. The data required to train and test this method are attained from a thermodynamic model of the engine under steady-state conditions. To evaluate the tolerance of the method against measurement uncertainties, Gaussian noise values were considered. Findings The test results revealed that this proposed method is capable of quantifying single, double and triple component faults with a sufficiently high degree of accuracy. Moreover, the authors confirmed that NANNs have derivable advantages over the single structure-based methods available in the public domain, particularly over those designed to perform single and multiple faults together. Practical implications This method can be used to assess engine’s health status to schedule its maintenance. Originality/value For complicated gas turbine diagnostic problems, the conventional single artificial neural network (ANN) structure-based fault diagnostic technique may not be enough to get robust and accurate results. The diagnostic task can rather be better done if it is divided and shared with multiple neural network structures. The authors thus used seven decentralized ANN structures to assess seven different component fault scenarios, which enhances the fault identification accuracy significantly.

Mini two-shaft gas turbine exergy analysis with a proposal to decrease exergy destruction

In this case study, exergy analysis is applied to a mini two-shaft gas turbine which is located in Islamic Azad University Khomeini Shahr Branch`s Thermodynamics laboratory and a proposal presented to make exergy destruction less using a Heat Recovery Water Heater (HRWH). Calculations were done for N2=20000 (rpm) constant and various N1 and after that for N1=60000 (rpm) constant and various N2. Results revealed that the highest exergy destruction rate occurs in combustion chamber in all conditions and a huge part of exergy destruction through the turbine exhaust. Increase in N1 leads to increases in all component exergy destruction rates. On the other hand, power turbine is the only component which is affected by changes in N2 and the exergy destruction rate increases with increase in N2. Moreover, exergy gained rate within HRWH increased with increase in N1 and is almost constant with changes in N2. In the same vein, exergetic efficiency of HRWH and exergy gained rate within HRWH are increased with decrease in water outlet temperature of HRWH.

Modeling and simulation of a two-shaft gas turbine propulsion system containing a frictional plate–type clutch

A marine propulsion system is composed of several sub-systems that operate in a variety of energy fields. The propulsion power of a ship can be provided from a two-shaft gas turbine. In this article, the modeling of a two-shaft gas turbine and its associated sub-systems including gears, flexible couplings and clutch is considered. These components are connected in the form of a virtual marine propulsion system, which is based on the bond-graph approach. When a clutch is used in a propulsion system, discontinuities occur in the describing model, which leads to some challenging problems when performing computer simulations. The two main difficulties are the numerical stiffness and the variable model structure. In this research, the bond-graph method is adapted as the modeling framework in order to allow a constant system structure model that minimizes the stiffness problem. Next, simulation results of a two-shaft gas turbine are presented in the off-design condition and verified with experimental tests. These results demonstrate the acceptable accuracy of computer simulations. Also, the effects of clutch performance on the dynamics of the marine propulsion system are discussed.

Operation of Two-Shaft Gas Turbine in the Range of Open Anti-Surge Valve

Abstract This paper presents experimental tests of full-scale two-shaft gas turbine in the range of open anti-surge valve (ASV). The tests were carried out in a laboratory gas- turbine test stand belonging to Department of Automation and Power Engineering , Faculty of Ocean Engineering and Ship Technology , Gdańsk University of Technology. The tests covered the start-up and low load operation of the turbine set in the range of open anti-surge valve.

Two-shaft stationary gas turbine engine gas path diagnostics using fuzzy logic

Our objective was to develop a Fuzzy logic (FL) based industrial two-shaft gas turbine gas path diagnostic method based on gas path measurement deviations. Unlike most of the available FL based diagnostic techniques, the proposed method focused on a quantitative analysis of both single and multiple component faults. The data required to demonstrate and verify the method was generated from a simulation program, tuned to represent a GE LM2500 engine running at an existing oil & gas plant, taking into account the two most common engine degradation causes, fouling and erosion. Gaussian noise is superimposed into the data to account measurement uncertainty. Finally, the fault isolation and quantification effectiveness of the proposed method was tested for single, double and triple component fault scenarios. The test results show that the implanted single, double and triple component fault case patterns are isolated with an average success rate of 96 %, 92 % and 89 % and quantified with an average accuracy of 83 %, 80 % and 78.5 %, respectively.

Application of Bond Graph approach in dynamic modelling of industrial gas turbine

Nowadays, gas turbines play a significant role in industry and power generation units. Therefore, any increase in their performance efficiency, is designers’ major concern. Power generation system’s principal considerations are performance, weight and reliability. Gas turbine engine is considered as a probable choice for such applications. This research develops and validates a Bond Graph model based on flow of energy and information of a gas turbine engine. Here, modelling of the gas turbine engine is achieved based on the pseudo Bond Graph approach. Subsequently, by coupling the Bond-Graph component models, a unified framework for model representation is presented. Also, to study the effect of changing external load on turbine’s performance, an industrial two-shaft gas turbine is simulated under large transient loads based on the previously developed component models. Finally, the commercial gas turbine simulation program (GSP) is used to validate the simulation results. Transient response simulations indicate an acceptable error between the GSP and Bond Graph model outputs.

Hardware-in-the-loop simulation of two-shaft gas turbine engine’s electronic control unit

An electronic control unit for a fuel control system of two-shaft gas turbine engines plays an undisputable role in providing the required fuel flow to the engine as well as satisfying engine’s operational characteristics. One of the main challenges in designing such unit is the accuracy of its performance and the control strategy implementation on an electronic hardware via repeatable and comprehensive tests. In this article, a hardware-in-the-loop simulation is presented for testing of the electronic control unit for a two-shaft gas turbine engine. For this purpose, the engine is first presented and modeled by the use of Wiener block structure method. The fuel controller with Min–Max structure is then explained. Finally, the controller is implemented on a PC/104 hardware and tested in an hardware-in-the-loop simulation in order to verify its correct performance. The results show that the fuel controller satisfies all of the engine’s physical constraints, confirming the controller competence and successful implementation of the engine control algorithm on the PC/104 hardware.

Investigation of Efficiency Deterioration Causes in Process Centrifugal Compressor Operation

The high operating efficiency of centrifugal compressor is a basic requirement to maintain the gas productivity and machine availability. However, there are several factors influencing the stage efficiency in the operating environment leading to a deterioration in the compressor performance in addition to its impact on the mechanical integrity of the internal components. These variables can be classified into three main groups which are suction parameters variation, flow profile distortion, and compressor component damage. The determination of the root cause will help for a proper maintenance plan and to reduce the machine downtime. Hence, this paper will introduce a new approach to identify the inefficient compressor operation causes based on the available operation data. The investigated case is a three-stage gas transport centrifugal compressor driven by 2.9 MW two-shaft gas turbine. The outcomes from the conducted optimisation are compared with the measured discharge parameters and the findings from the internal inspection observation to emphasize the outcomes from the derived approach.