Design Study of a Humidification Tower for the Advanced Humid Air Turbine System

The AHAT (advanced humid air turbine) system, which can be equipped with a heavy-duty, single-shaft gas turbine, aims at high efficiency equal to that of the HAT system. Instead of an intercooler, a WAC (water atomization cooling) system is used to reduce compressor work. The characteristics of a humidification tower (a saturator), which is used as a humidifier for the AHAT system, were studied. The required packing height and the exit water temperature from the humidification tower were analyzed for five virtual gas turbine systems with different capacities (1MW, 3.2MW, 10MW, 32MW and 100MW) and pressure ratios (π = 8, 12, 16, 20 and 24). Thermal efficiency of the system was compared with that of a simple cycle and a recuperative cycle with and without the WAC system. When the packing height of the humidification tower was changed, the required size varied for the three heat exchangers around the humidification tower (a recuperator, an economizer and an air cooler). The packing height with which the sum total of the size of the packing and these heat exchangers became a minimum was 1m for the lowest pressure ratio case, and 6m for the highest pressure ratio case.

A New Calculation Approach to the Energy Balance of a Gas Turbine Including a Study of the Impact of the Uncertainty of Measured Parameters

Computing the solution to the energy balance around a gas turbine in order to calculate the intake mass flow and the turbine inlet temperature requires several iterations. This makes hand calculations very difficult and, depending on the software used, even causes significant calculation times on PCs. While this may not seem all that important considering the power of today’s personal computers, the approach described in this paper presents a new way of looking at the gas turbine process and the resulting simplifications in the calculations. This paper offers a new approach to compute the energy balance around a gas turbine. The energy balance requires that all energy flows going into and out of the control volume be accounted for. The difficulty of the energy balance equation around a gas turbine lies in the fact that the exhaust gas composition is unknown as long as the intake flow is unknown. Thus, a composition needs to be assumed when computing the exhaust gas enthalpy. This allows the calculation of the intake flow, which in turn provides a new exhaust gas composition, and so forth. By viewing the exhaust gas as a flow consisting of ambient air and combusted fuel, the described iteration can be avoided. The study presents the formulation of the energy balance applying this approach and looks at the accuracy of the result as a function of the inaccuracy of the input parameters. Furthermore, solutions of the energy balance are presented for various process scenarios, and the impact of the uncertainty of key process parameter is analyzed.

A New Gas Turbine Enclosure Ventilation Design Criterion

Dilution ventilation is a widely used means of protection against the risk of explosion within gas turbine acoustic enclosures arising from the leakage and accumulation of flammable gas and its ignition from the turbine. In ASME 98GT-215 a safety criterion was proposed for the design of ventilation by defining the allowable size of flammable gas cloud as a proportion of the enclosure volume. This criterion was theoretically based, with a significant safety factor. Whilst generally viable, it was found to be difficult to achieve in some cases. A research project, described in ASME GT-2002-30469, was launched to define a criterion more accurately and with known conservatism based on a detailed programme of experimental explosions and Computational Fluid Dynamics (CFD) modelling. The $600k project was largely financed by the gas turbine industry, including suppliers and users, and by CFD contractors. The paper describes the project aims, its scope of work, and includes the main results, the new criterion and conclusions.

Improving Operational Availability of Gas Turbine Generators Aboard U.S. Navy DDG-51 Class Ships by Combining the Capabilities of the Integrated Condition Assessment System (ICAS) and the Generator Set’s Full Authority Digital Controller (FADC)

Operational availability of Gas Turbine Generator Sets (GTGs) aboard the U.S. Navy’s DDG 51 Class ships is being enhanced through the combined capabilities of the ship’s Integrated Condition Assessment System (ICAS) and the GTG’s Full Authority Digital Control (FADC). This paper describes the ICAS and FADC systems; their current capabilities and the vision of how those capabilities will evolve in order to improve equipment readiness and reduce life cycle costs.

Developing and Deploying ICAS-Capable CBM Software Modules: Best Practices and Lessons Learned

The U.S. Navy’s Integrated Condition Assessment System (ICAS) is a shipboard monitoring system that helps enable the Navy’s Condition Based Maintenance (CBM) initiative. ICAS is installed on a large number of Navy Surface Combatants and provides data acquisition, display, and logging, as well as equipment diagnostic analysis for troubleshooting and maintenance tasking of hull mechanical and electrical systems. In recent years, it has been desirable to integrate specialized, third party diagnostic or prognostic software as plug ‘n play modules within the ICAS environment. A specific effort focused on such modules for shipboard LM2500 and Allison 501K gas turbine engines is well underway. Over the course of this three-year Prognostic Enhancement to Diagnostic System (PEDS) program, many lessons have been learned, best practices for ICAS integration have been identified, and the important steps required to field ICAS-capable modules have been realized. This paper summarizes these lessons and processes for future 3rd party integration efforts and provides specific examples for the developed gas turbine modules. The successful deployment of these modules aboard Navy ships is used to validate the ideas presented.

Development of Parametric Mass and Volume Models for an Aerospace SOFC/Gas Turbine Hybrid System

In aerospace power systems, mass and volume are key considerations to produce a viable design. The utilization of fuel cells is being studied for a commercial aircraft electrical power unit. Based on preliminary analyses [1, 2], a SOFC/gas turbine system may be a potential solution. This paper describes the parametric mass and volume models that are used to assess an aerospace hybrid system design. The design tool utilizes input from the thermodynamic system model and produces component sizing, performance and mass estimates. The software is designed such that the thermodynamic model is linked to the mass and volume model to provide immediate feedback during the design process. It allows for automating an optimization process that accounts for mass and volume in its figure of merit. Each component in the system is modeled with a combination of theoretical and empirical approaches. A description of the assumptions and design analyses is presented.

Sensitivity Analysis of Transient Compressor Operation Behaviour in SOFC-GT Hybrid Systems

This paper presents a sensitivity analysis of unsteady-state SOFC-GT-HS operation based on two different characteristic maps of centrifugal compressor taken from open literature and scaled by the law of similitude to match the design point of the Hybrid System. The system layout under investigation is a pressurised type comprising a low and high temperature recuperator. Computations are based on a one-dimensional finite element model of planar high temperature SOFC, which is validated against open literature. The reduced Moore and Greitzer model is used for compressor modelling. Calculation results of the coupled SOFC-GT-Hybrid System show that unsteady-state part-load operation is sensitive to the characteristics of compressor speed-lines but also to the load change operation procedure.

An Adaptation Approach for Gas Turbine Design-Point Performance Simulation

Accurate simulation and understanding of gas turbine performance is very useful for gas turbine users. Such a simulation and performance analysis must start from a design point. When some of the engine component parameters for an existing engine are not available, they must be estimated in order that the performance analysis can be carried out. However, the initially simulated design point performance of the engine using estimated engine component parameters may give a result that is different from the actual measured performance. This difference may be reduced with better estimation of these unknown component parameters. However, this can become a difficult task for performance engineers, let alone those without enough engine performance knowledge and experience, when the number of design point component parameters and the number of measurable/target performance parameters become large. In this paper, a gas turbine design point performance adaptation approach has been developed to best estimate the unknown design point component parameters and match the available design point engine measurable/target performance. In the approach, the initially unknown component parameters may be compressor pressure ratios and efficiencies, turbine entry temperature, turbine efficiencies, air mass flow rate, cooling flows, by-pass ratio, etc. The engine target (measurable) performance parameters may be thrust and SFC for aero engines, shaft power and thermal efficiency for industrial engines, gas path pressures and temperatures, etc. To select initially the design point component parameters, a bar chart has been used to analyze the sensitivity of the engine target performance parameters to the design point component parameters. The developed adaptation approach has been applied to a design point performance matching problem of an industrial gas turbine engine GE LM2500+ operating in Manx Electricity Authority (MEA), UK. The application shows that the adaptation approach is very effective and fast to produce a set of design point component parameters of a model engine that matches the actual engine performance very well. Theoretically the developed techniques can be applied to other gas turbine engines.

A Study of On-Line and Off-Line Turbine Washing to Optimize the Operation of a Gas Turbine

This paper highlights the procedure followed in order to establish an effective on-line and off line water wash program on a fleet of 36 small industrial turbines. To determine the efficacy of water washing a program of tests under controlled conditions was organized. With proper condition monitoring techniques, a set of tests were developed in order to identify the proper water wash frequency and the dissolving agent used to water wash. The goal of the water wash program is to maximize turbine power, and efficiency; while minimizing maintenance labor, and material. The Gas Turbine Compressor Isentropic Efficiency, the overall heat rate, and the overall thermal efficiency were used to compare the tests and evaluate the performance of different water wash frequencies and solvents. 8760 points defined each test as the data was taken over a one year time period, at a one hour interval.

Optimization of Thermodynamically Efficient Nominal 40 MW Zero Emission Pilot and Demonstration Power Plant in Norway

In Aug 2004 the Zero Emission Norwegian Gas (ZENG) project team completed Phase-1: Concept and Feasibility Study for a 40 MW Pilot & Demonstration (P&D) Plant, that is proposed will be located at the Energy Park, Risavika, near Stavanger in South Norway during 2008. The power plant cycle is based upon implementation of the natural gas (NG) and oxygen fueled Gas Generator (GG) (1500°F/1500 psi) successfully demonstrated by Clean Energy Systems (CES) Inc. The GG operations was originally tested in Feb 2003 and is currently (Feb 2005) undergoing extensive commissioning at the CES 5MW Kimberlina Test Plant, near Bakersfield, California. The ZENG P&D Plant will be an important next step in an accelerating path towards demonstrating large-scale (+200 MW) commercial implementation of zero-emission power plants before the end of this decade. However, development work also entails having a detailed commercial understanding of the techno-economic potential for such power plant cycles: specifically in an environment where the future penalty for carbon dioxide (CO2) emissions remains uncertain. Work done in dialogue with suppliers during ZENG Project Phase-1 has cost-estimated all major plant components to a level commensurate with engineering pre-screening. The study has also identified several features of the proposed power plant that has enabled improvements in thermodynamic efficiency from 37% up to present level of 44–46% without compromising the criteria of implementation using “near-term” available technology. The work has investigated: i. Integration between the cryogenic air separation unit (ASU) and the power plant. ii. Use of gas turbine technology for the intermediate pressure (IP) steam turbine. iii. Optimal use of turbo-expanders and heat-exchangers to mitigate the power consumption incurred for oxygen production. iv. Improved condenser design for more efficient CO2 separation and removal. v. Sensitivity of process design criteria to “small” variations in modeling of the physical properties for CO2/steam working fluid near saturation. vi. Use of a second “conventional” pure steam Rankine bottoming cycle. In future analysis, not all these improvements need necessarily be seen to be cost-effective when taking into account total P&D program objectives; thermodynamic efficiency, power plant investment, operations and maintenance cost. However, they do represent important considerations towards “total” optimization when designing the P&D Plant. We observe that Project Phase-2: Pre-Engineering & Qualification should focus on optimization of plant size with respect to total capital investment (CAPEX); and identification of further opportunities for extended technology migration from gas turbine environment that could also permit raised turbine inlet temperatures (TIT).