On the Shaft Speed Selection of Parallel Hybrid Aero Engines

2021 ◽  
Author(s):  
Michael Sielemann ◽  
Jesse Gohl ◽  
Xin Zhao ◽  
Konstantinos Kyprianidis ◽  
Giorgio Valente ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Integrated Design ◽  
Low Pressure ◽  
Electrical Machine ◽  
Shaft Speed ◽  
Trade Off ◽  
Parallel Hybrid ◽  
Rules Of Thumb ◽  
The Impact

Abstract The boosted turbo fan or parallel hybrid is a promising means to reduce fuel consumption of gas turbines on aircraft. With an electric drive on the low-pressure spool of the gas turbine, it requires a trade-off between the characteristics of the gas turbine and the electric power sub-systems. Reducing specific thrust at a given thrust requirement results in a larger fan with a lower pressure ratio. This leads to improved propulsive efficiency but at the expense of increased weight and nacelle drag. At a given design relative tip Mach number, increasing fan size and hence tip diameter means the fan shaft speed will need to be reduced. This will, according to occasionally quoted ‘rules of thumb’, make the directly coupled electrical drive more efficient but heavier. The objective of this paper is to expose some key aspects of this trade-off in terms of efficiency and weight, and relate them to these guidelines. The paper applies sophisticated methodology in both addressed domains. For the gas turbine, multi-point design is used. Here, established synthesis matching schemes focusing on gas turbine performance parameters are extended with parameters from the sizing and weight estimation such as diameters and tip speeds. For the electrical machine, fully analytical sizing capturing the impact of cooling supply is used. The paper reports estimated gas path and machine geometries. It gives an understanding of the interactions between both sub-systems and allows concluding which low pressure spool speed gives the best instantaneous performance. It largely confirms the quoted rules of thumb but exposes that the factors affecting machine efficiency are more involved than implied for an integrated design.

Prediction and Mitigation Strategies for Compressor Instabilities due to Large Pressurized Volumes in Micro Gas Turbine Systems

2021 ◽  
Author(s):  
Thomas Krummrein ◽  
Martin Henke ◽  
Timo Lingstädt ◽  
Martina Hohloch ◽  
Peter Kutne
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Flow Instability ◽  
Measurement Data ◽  
Mitigation Strategies ◽  
Mathematical Explanation ◽  
Shaft Speed ◽  
Micro Gas Turbine ◽  
The Impact

Abstract Micro gas turbines are a versatile platform for advanced cycle concepts. In these novel cycles, basic micro gas turbine components — compressor, turbine, combustor and recuperator — are coupled with various other technologies to achieve higher efficiency and flexibility. Examples are hybrid power plants integrating pressurized fuel cells, solar receivers or thermal storages. Characteristically, such complex cycles contain vast pressurized gas volumes between compressor and turbine, many times larger than those contained in conventional micro gas turbines. In fast deceleration maneuvers the rotational speed of the compressor drops rapidly. However, the pressure decrease is delayed due to the large amount of gas contained in the volumes. Ultimately, this can lead to compressor flow instability or surge. To predict and mitigate such instabilities, not only the compressor surge limit must be known, but also the dynamic dependencies between shaft speed deceleration, pressure and flow changes within the system. Since appropriate experiments may damage the system, investigations with numerical simulations are crucial. The investigation begins with a mathematical explanation of the relevant mechanisms, based on a simplified analytical model. Subsequently, the DLR in-house simulation program TMTSyS (Transient Modular Turbo-System Simulator) is used to investigate the impact of transient maneuvers on a micro gas turbine test rig containing a large pressurized gas volume in detail. After the relevant aspects of the simulation model are validated against measurement data, it is shown that the occurrence of compressor instabilities induced by fast deceleration can be predicted with the simulator. It is also shown that the simulation tool enables these predictions using only measurement data of non-critical maneuvers. Hence, mitigation strategies are derived that allow to estimate save shaft speed deceleration rate limits based on non-critical performance measurements.

scholarly journals Comprehensive Thermodynamic Analysis of the Humphrey Cycle for Gas Turbines with Pressure Gain Combustion

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3521 ◽  
Author(s):  
Panagiotis Stathopoulos
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Process ◽  
Ideal Gas ◽  
Point Of View ◽  
Pressure Gain Combustion ◽  
Combustion Technology ◽  
Secondary Air ◽  
And Performance ◽  
The Impact

Conventional gas turbines are approaching their efficiency limits and performance gains are becoming increasingly difficult to achieve. Pressure Gain Combustion (PGC) has emerged as a very promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine thermodynamic cycles. Up to date, only very simplified models of open cycle gas turbines with pressure gain combustion have been considered. However, the integration of a fundamentally different combustion technology will be inherently connected with additional losses. Entropy generation in the combustion process, combustor inlet pressure loss (a central issue for pressure gain combustors), and the impact of PGC on the secondary air system (especially blade cooling) are all very important parameters that have been neglected. The current work uses the Humphrey cycle in an attempt to address all these issues in order to provide gas turbine component designers with benchmark efficiency values for individual components of gas turbines with PGC. The analysis concludes with some recommendations for the best strategy to integrate turbine expanders with PGC combustors. This is done from a purely thermodynamic point of view, again with the goal to deliver design benchmark values for a more realistic interpretation of the cycle.

AI Assisted High Fidelity Multi-Physics Digital Twin of Industrial Gas Turbines

2021 ◽  
Author(s):  
Senthil Krishnababu ◽  
Omar Valero ◽  
Roger Wells
Keyword(s):  
Gas Turbine ◽  
Data Storage ◽  
Gas Turbines ◽  
Building Blocks ◽  
Data Driven ◽  
High Fidelity ◽  
Test Field ◽  
Operating Characteristics ◽  
Digital Twin ◽  
The Impact

Abstract Data driven technologies are revolutionising the engineering sector by providing new ways of performing day to day tasks through the life cycle of a product as it progresses through manufacture, to build, qualification test, field operation and maintenance. Significant increase in data transfer speeds combined with cost effective data storage, and ever-increasing computational power provide the building blocks that enable companies to adopt data driven technologies such as data analytics, IOT and machine learning. Improved business operational efficiency and more responsive customer support provide the incentives for business investment. Digital twins, that leverages these technologies in their various forms to converge physics and data driven models, are therefore being widely adopted. A high-fidelity multi-physics digital twin, HFDT, that digitally replicates a gas turbine as it is built based on part and build data using advanced component and assembly models is introduced. The HFDT, among other benefits enables data driven assessments to be carried out during manufacture and assembly for each turbine allowing these processes to be optimised and the impact of variability or process change to be readily evaluated. On delivery of the turbine and its associated HFDT to the service support team the HFDT supports the evaluation of in-service performance deteriorations, the impact of field interventions and repair and the changes in operating characteristics resulting from overhaul and turbine upgrade. Thus, creating a cradle to grave physics and data driven twin of the gas turbine asset. In this paper, one branch of HFDT using a power turbine module is firstly presented. This involves simultaneous modelling of gas path and solid using high fidelity CFD and FEA which converts the cold geometry to hot running conditions to assess the impact of various manufacturing and build variabilities. It is shown this process can be executed within reasonable time frames enabling creation of HFDT for each turbine during manufacture and assembly and for this to be transferred to the service team for deployment during field operations. Following this, it is shown how data driven technologies are used in conjunction with the HFDT to improve predictions of engine performance from early build information. The example shown, shows how a higher degree of confidence is achieved through the development of an artificial neural network of the compressor tip gap feature and its effect on overall compressor efficiency.

Uncertainty Analysis of Inflow Conditions on an HPT Gas Turbine Nozzle: Effect on Particle Deposition

2020 ◽  
Author(s):  
R. Friso ◽  
N. Casari ◽  
M. Pinelli ◽  
A. Suman ◽  
F. Montomoli
Keyword(s):  
Gas Turbine ◽  
Energy Efficient ◽  
Gas Turbines ◽  
Particle Deposition ◽  
Operating Conditions ◽  
Wide Range ◽  
And Performance ◽  
Gas Turbine Nozzle ◽  
The Impact ◽  
Inflow Conditions

Abstract Gas turbines (GT) are often forced to operate in harsh environmental conditions. Therefore, the presence of particles in their flow-path is expected. With this regard, deposition is a problem that severely affects gas turbine operation. Components’ lifetime and performance can dramatically vary as a consequence of this phenomenon. Unfortunately, the operating conditions of the machine can vary in a wide range, and they cannot be treated as deterministic. Their stochastic variations greatly affect the forecasting of life and performance of the components. In this work, the main parameters considered affected by the uncertainty are the circumferential hot core location and the turbulence level at the inlet of the domain. A stochastic analysis is used to predict the degradation of a high-pressure-turbine (HPT) nozzle due to particulate ingestion. The GT’s component analyzed as a reference is the HPT nozzle of the Energy-Efficient Engine (E3). The uncertainty quantification technique used is the probabilistic collocation method (PCM). This work shows the impact of the operating conditions uncertainties on the performance and lifetime reduction due to deposition. Sobol indices are used to identify the most important parameter and its contribution to life. The present analysis enables to build confidence intervals on the deposit profile and on the residual creep-life of the vane.

Short-Term Optimization of a Combined Cycle Power Plant Integrated With an Inlet Air Conditioning Unit

2020 ◽  
Author(s):  
Weimar Mantilla ◽  
José García ◽  
Rafael Guédez ◽  
Alessandro Sorce
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Air Conditioning ◽  
Combined Cycle ◽  
Plant Performance ◽  
Mixed Integer ◽  
Environmental Load ◽  
Turbine Inlet ◽  
The Impact

Abstract Under new scenarios with high shares of variable renewable electricity, combined cycle gas turbines (CCGT) are required to improve their flexibility, in terms of ramping capabilities and part-load efficiency, to help balance the power system. Simultaneously, liberalization of electricity markets and the complexity of its hourly price dynamics are affecting the CCGT profitability, leading the need for optimizing its operation. Among the different possibilities to enhance the power plant performance, an inlet air conditioning unit (ICU) offers the benefit of power augmentation and “minimum environmental load” (MEL) reduction by controlling the gas turbine inlet temperature using cold thermal energy storage and a heat pump. Consequently, an evaluation of a CCGT integrated with this inlet conditioning unit including a day-ahead optimized operation strategy was developed in this study. To establish the hourly dispatch of the power plant and the operation mode of the inlet conditioning unit to either cool down or heat up the gas turbine inlet air, a mixed-integer linear optimization (MILP) was formulated using MATLAB, aiming to maximize the operational profit of the plant within a 24-hours horizon. To assess the impact of the proposed unit operating under this dispatch strategy, historical data of electricity and natural gas prices, as well as meteorological data and CO2 emission allowances price, have been used to perform annual simulations of a reference power plant located in Turin, Italy. Furthermore, different equipment capacities and parameters have been investigated to identify trends of the power plant performance. Lastly, a sensitivity analysis on market conditions to test the control strategy response was also considered. Results indicate that the inlet conditioning unit, together with the dispatch optimization, increases the power plant’s operational profit by achieving a wider operational range, particularly important during peak and off-peak periods. For the specific case study, it is estimated that the net present value of the CCGT integrated with the ICU is 0.5% higher than the power plant without the unit. In terms of technical performance, results show that the unit reduces the minimum environmental load by approximately 1.34% and can increase the net power output by 0.17% annually.

scholarly journals A Real-Time Degradation Model for Hardware in the Loop Simulation of Fuel Cell Gas Turbine Hybrid Systems

2015 ◽  
Author(s):  
Valentina Zaccaria ◽  
Alberto Traverso ◽  
David Tucker
Keyword(s):  
Fuel Cell ◽  
Real Time ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Current Density ◽  
Gas Turbines ◽  
Hardware In The Loop ◽  
Fuel Utilization ◽  
Time Operation ◽  
The Impact

The theoretical efficiencies of gas turbine fuel cell hybrid systems make them an ideal technology for the future. Hybrid systems focus on maximizing the utilization of existing energy technologies by combining them. However, one pervasive limitation that prevents the commercialization of such systems is the relatively short lifetime of fuel cells, which is due in part to several degradation mechanisms. In order to improve the lifetime of hybrid systems and to examine long-term stability, a study was conducted to analyze the effects of electrochemical degradation in a solid oxide fuel cell (SOFC) model. The SOFC model was developed for hardware-in-the-loop simulation with the constraint of real-time operation for coupling with turbomachinery and other system components. To minimize the computational burden, algebraic functions were fit to empirical relationships between degradation and key process variables: current density, fuel utilization, and temperature. Previous simulations showed that the coupling of gas turbines and SOFCs could reduce the impact of degradation as a result of lower fuel utilization and more flexible current demands. To improve the analytical capability of the model, degradation was incorporated on a distributed basis to identify localized effects and more accurately assess potential failure mechanisms. For syngas fueled systems, the results showed that current density shifted to underutilized sections of the fuel cell as degradation progressed. Over-all, the time to failure was increased, but the temperature difference along cell was increased to unacceptable levels, which could not be determined from the previous approach.

Thermal Influences in Gas Turbine Transients: Effects of Changes in Compressor Characteristics

1979 ◽  
Author(s):  
N. R. L. Maccallum
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Transient Response ◽  
Gas Turbines ◽  
Axial Flow ◽  
Transient Heat Transfer ◽  
Shaft Speed ◽  
Delivery Pressure ◽  
Surge Line ◽  
Transfer Parameters

During transients of axial-flow gas turbines, the characteristics of the compressor are altered. The changes in these characteristics (excluding surge line changes) have been related to transient heat transfer parameters, and these relations have been incorporated in a program for predicting the transient response of a single-shaft aero gas turbine. The effect of the change in compressor characteristics has been examined in accelerations using two alternative acceleration fuel schedules. When the fuel is scheduled on compressor delivery pressure alone. there is no increase in predicted acceleration times. When the fuel is scheduled on shaft speed alone, the predicted acceleration times are increased by about 5 to 6 percent.

Recognising the Viability of Cooling Gas Turbine Inlet Air in Colder Regions by Using Low Pressure Fogging Techniques

2002 ◽  
Author(s):  
John Confurius
Keyword(s):  
Ambient Temperature ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Low Pressure ◽  
Air Cooling ◽  
Turbine Inlet ◽  
The World

The profits that can be gained by use of inlet air cooling on gas turbines has been recognised for quite some time now and the systems installed throughout the world have shown the users in the gas turbine field that cooling indeed can be used to boost power at times when the ambient temperature reaches or exceeds the ISO rating temperature of the gas turbine. Drawback however being that the initial investment asked of the gas turbine user is rather large thus only justifying a cooling system in regions where the outdoor temperatures exceed the ISO rating time and again due to the climate in that region. Lately gas turbine users in colder climates have become interested in power augmentation during their short summer, however there is no justification for an investment like necessary when installing one of the presently available systems on the market. As the question reached us from more and more of our clients it stimulated us to go out and search for a low-investment solution to this problem. This resulted in the world’s first low pressure gas turbine inlet cooling system.

Risk-Based Assessment of Unplanned Outage Events and Costs for Combined-Cycle-Plants

2012 ◽  
Author(s):  
Dale Grace ◽  
Thomas Christiansen
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Cash Flow ◽  
Gas Turbines ◽  
Operational Reliability ◽  
Combined Cycle ◽  
Maintenance Costs ◽  
Wide Range ◽  
Turbine Equipment ◽  
The Impact

Unexpected outages and maintenance costs reduce plant availability and can consume significant resources to restore the unit to service. Although companies may have the means to estimate cash flow requirements for scheduled maintenance and on-going operations, estimates for unplanned maintenance and its impact on revenue are more difficult to quantify, and a large fleet is needed for accurate assessment of its variability. This paper describes a study that surveyed 388 combined-cycle plants based on 164 D/E-class and 224 F-class gas turbines, for the time period of 1995 to 2009. Strategic Power Systems, Inc. (SPS®), manager of the Operational Reliability Analysis Program (ORAP®), identified the causes and durations of forced outages and unscheduled maintenance and established overall reliability and availability profiles for each class of plant in 3 five-year time periods. This study of over 3,000 unit-years of data from 50 Hz and 60 Hz combined-cycle plants provides insight into the types of events having the largest impact on unplanned outage time and cost, as well as the risks of lost revenue and unplanned maintenance costs which affect plant profitability. Outage events were assigned to one of three subsystems: the gas turbine equipment, heat recovery steam generator (HRSG) equipment, or steam turbine equipment, according to the Electric Power Research Institute’s Equipment Breakdown Structure (EBS). Costs to restore the unit to service for each main outage cause were estimated, as were net revenues lost due to unplanned outages. A statistical approach to estimated costs and lost revenues provides a risk-based means to quantify the impact of unplanned events on plant cash flow as a function of class of gas turbine, plant subsystem, and historical timeframe. This statistical estimate of the costs of unplanned outage events provides the risk-based assessment needed to define the range of probable costs of unplanned events. Results presented in this paper demonstrate that non-fuel operation and maintenance costs are increased by roughly 8% in a typical combined-cycle power plant due to unplanned maintenance events, but that a wide range of costs can occur in any single year.

Off-Design Performance Investigation of a Low Calorific Value Gas Fired Generic-Type Single-Shaft Gas Turbine

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Raik C. Orbay ◽  
Magnus Genrup ◽  
Pontus Eriksson ◽  
Jens Klingmann
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Calorific Value ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Flammability Limits ◽  
Generic Type ◽  
Wobbe Index ◽  
The Impact

When low calorific value gases are fired, the performance and stability of gas turbines may deteriorate due to a large amount of inertballast and changes in working fluid properties. Since it is rather rare to have custom-built gas turbines for low lower heating value (LHV) operation, the engine will be forced to operate outside its design envelope. This, in turn, poses limitations to usable fuel choices. Typical restraints are decrease in Wobbe index and surge and flutter margins for turbomachinery. In this study, an advanced performance deck has been used to quantify the impact of firing low-LHV gases in a generic-type recuperated as well as unrecuperated gas turbine. A single-shaft gas turbine characterized by a compressor and an expander map is considered. Emphasis has been put on predicting the off-design behavior. The combustor is discussed and related to previous experiments that include investigation of flammability limits, Wobbe index, flame position, etc. The computations show that at constant turbine inlet temperature, the shaft power and the pressure ratio will increase; however, the surge margin will decrease. Possible design changes in the component level are also discussed. Aerodynamic issues (and necessary modifications) that can pose severe limitations on the gas turbine compressor and turbine sections are discussed. Typical methods for axial turbine capacity adjustment are presented and discussed.

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