bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaporative Compressor Cooling for NOx Suppression and Enhanced Engine Performance for Naval Gas Turbine Propulsion Plants
Authors: Sexton Michael R. , Urbach Herman B. , Knauss Donald T. 
Published: December 2014

Water, in the liquid or vapor phase, injected at various locations into the gas turbine cycle has frequently been employed to improve engine performance while simultaneously reducing NOx emissions. Commercial steam injected gas turbines have been designed to inject small amounts of steam (less than 15% of air flow), generated in a heat recovery boiler, into or downstream of the combustor. Recently, it has been proposed to inject larger amounts of water (as high as 50% of air flow) and operate combustors near stoichiometric conditions. All these methods increase turbine mass flow rate without increasing air flow rate and consequently increase specific power. The increase in specific power for naval applications means smaller intake and exhaust stacks and therefore less impact on topside space.
The present paper presents a new concept, in naval propulsion plants, to decrease NOx production and increase specific power with a water fog (droplet spray) injected (WFI) directly into the inlet of the engine compressor. The simulated performance of a simple-cycle gas turbine engine using WFI is reported. The paper describes the computer model developed to predict compressor performance resulting from the evaporation of water passing through the stages of an axial flow compressor. The resulting effects are similar to those of an intercooled compressor, without the complications due to the addition of piping, heat exchangers, and the requirement for a dual spool compressor. The effects of evaporative cooling on compressor characteristics are presented. These results include compressor maps modified for various water flow rates as well as estimates of the reductions in compression work and compressor discharge temperature.
These modified compressor performance characteristics are used in the engine simulation to predict how a WFI engine would perform under various water injection flow rates. Estimates of increased output power and decreased air flow rates are presented.
Characterization of Fatigue Mechanisms of Thermal Barrier Coatings by a Novel Laser-Based Test
Authors: Rettig Uwe , Bast Ulrich , Steiner Dinorah , Oechsner Matthias 
Published: December 2014

The use of high performance ceramic thermal barrier coatings in stationary gas turbines requires fundamental knowledge of their fatigue behavior under high temperature gradients and thermal cycling. An experimental method based on rapid laser heating complemented with finite-element calculations was developed in order to identify the major damage mechanisms and to obtain a data set for reliability assessment of thermal barrier coatings for temperature and stress fields similar to gas turbine conditions.
The observed failures are strongly related to the pretreatment procedures such as annealing under high temperature gradients and isothermal long-term oxidation. The vertical crack patterns observed close to the top surface of the Zirconia coating are generated at the moment of rapid cooling. These cracks are induced by high biaxial tensile stresses caused by the temperature gradient and the stress reversion after relaxation of compressive stresses at high temperatures. The long-term fatigue behavior is decisively determined by two processes:
(i) The porous Zirconia loses its damage tolerant properties by densification.
(ii) The growth of an oxide layer at the bond coat degrades adhesion and produces localized stress fields at the interface.
Cyclic loads increase the length of existing in-plane cracks and delaminations rather than enlarging their number. Misfit of the crack flanks and wedge effects are the driving forces for continued crack propagation.
These experimental results are discussed in terms of fracture mechanics.
Gas Turbine Cycle Design Methodology: A Comparison of Parameter Variation With Numerical Optimization
Authors: Kurzke Joachim 
Published: December 2014

In gas turbine performance simulations often the question arises: What is the best thermodynamic cycle design point? This is an optimization task which can be attacked in two ways: One can do a series of parameter variations and pick from the resulting graphs the best solution or one can employ numerical optimization algorithms that produce a single cycle which fulfills all constraints.
The conventional parameter study builds strongly on the engineering judgement and gives useful information over a range of parameter selections. However, when values for more than a few variables have to be determined while several constraints are existing, then numerical optimization routines can help to find the mathematical optimum faster and more accurately. Sometimes even an outstanding solution is found which was overlooked while doing a preliminary parameter study.
For any simulation task a sophisticated graphical user interface is of great benefit. This is especially true for automated numerical optimizations. It is quite helpful to see on the screen of a PC how the variables are changing and which constraints are limiting the design. A quick and clear graphical representation of trade studies is also of great advantage. The paper describes how numerical optimization and parameter studies are implemented in a Windows-based PC program.
As an example, the cycle selection of a derivative turbofan engine with a given core shows the merits of numerical optimization. The parameter variation is best suited for presenting the sensitivity of the result in the neighborhood of the optimum cycle design point.
Pressurized Gasification of Biomass
Authors: Salo K. , Horvath A. , Patel J. 
Published: December 2014

Biomass is a fuel of increasing interest in power generation since it is clean and renewable. Besides conventional power generating systems biomass fuel will be utilized in Integrated Gasification Combined Cycle (IGCC) power plants in the near future.
Carbona Inc. (the successor to Enviropower Inc.) is commercializing a biomass fueled IGCC system. This system is based on a simplified IGCC process which applies the gasification technology originally developed by the Institute of Gas Technology (IGT) and further developed by Enviropower before licensing the technology to Carbona and an advanced hot gas clean-up system.
An extensive pilot test program has been carried out by Enviropower/Carbona covering all aspects of a biomass based gasification process. More than 5000 tons of different biomass feedstocks have been gasified at the pilot plant in Tampere, Finland. The pilot plant converts 15 MW (51 MMBtu/h) thermal input of fuel to product gas. Several biomass qualities/mixtures have been used during the test runs including hard wood, soft wood with and without branches, needles and bark. Short rotation biomass like willow and alfalfa have also been tested.
This paper concentrates on the results and differences in gasification of different biomass materials with special emphasis on the suitability of product gas for gas turbines, the fate of ammonia, vapor phase alkali metals and air toxics. The development of demonstration projects is also discussed in this paper.
Determination of the Realistic Turbocharger Efficiency With Pulsating Gas-Flow Compared on a 4-Cylinder Engine
Authors: Trenc Ferdinand , Čer Matej , Bizjan Frančišek , Hribernik Aleš 
Published: December 2014

Small single or twin entry radial turbines are mostly used to drive compressors of the turbocharged internal combustion engines. There are two general possibilities to feed the turbine of a four-stroke, 4-cylinder turbocharged Diesel engine: 1) by preserving most of the available exhaust kinetic energy, or 2) by mixing exhaust pulses from all cylinders in one common manifold. In the first case, better utilization of the dynamic pulse energy increases efficiency of the turbine; highly unsteady mass flow of the exhaust gasses, on the other hand, and thus periods of partial exhaust flow admission at the turbine inlet simultaneously reduces this gain in the turbine efficiency. More steady mass-flow of the exhaust gasses is created in the case of the exhaust system 2), however some kinetic energy is lost during the mixing phase in the common exhaust manifold. Calculation of the overall turbocharger and turbine efficiency is normally based on average values of the measured pressures and temperatures. As the result apparent efficiencies are obtained; the more the flow is pulsating, the bigger is the difference between the real and the apparent efficiency. The ratio between these two efficiencies is known as the energy pulsation factor β. It depends generally on the “pulse intensity”-pressure deviation from its mean value, shape of the pressure pulse, number of the individual pulses feeding separate gas turbine inlets, turbocharger, and can be successfully used to determine real efficiency of a turbocharger and to define some working parameters of the engine.
A field of β factors for different engine running conditions and for the 4-cylinder engine with 2-cylinder group pulse system (rarely applied), and the commonly applied exhaust system with 4-cylinder group and moderate pressure fluctuation is presented in the paper. Influence of the dynamic exhaust temperatures on the β value is discussed as well.
Experimental Investigation of Unsteady Flow Phenomena in a Centrifugal Compressor Vaned Diffuser of Variable Geometry
Authors: Justen Friedrich , Ziegler Kai U. , Gallus Heinz E. 
Published: December 2014

The behaviour of vaned radial diffusers is generally considered to be due to the flow phenomena in the vaneless and the semi-vaned space in the diffuser inlet region. Even considering unsteady aspects, the adjacent diffuser channel is regarded as less important. The flat wedge vaned diffuser of the investigated centrifugal compressor stage allows an independent continuous adjustment of the diffuser vane angle and the radial gap between impeller outlet and diffuser vane inlet, so that information about the importance of these geometric parameters can be obtained.
The time dependent pressure distribution on the diffuser front wall and on suction and pressure surface of the diffuser vanes reveal that in the semi-vaned space mainly the region near the vane suction side is influenced by the unsteady impeller-diffuser-interaction. Downstream in the diffuser channel the unsteadiness does not decay. Here, pressure fluctuations are appearing which are distinctly higher than the pressure fluctuations in the vaneless space.
An estimation of the influence of the unsteadiness on the operating performance of the centrifugal compressor stage is made by measurements at choke and surge limit for different diffuser geometries.
On the Performance of Hybrid Foil-Magnetic Bearings
Authors: Heshmat Hooshang , Chen H. Ming , Walton James F. 
Published: December 2014

Recent technological advancements make hybridization of the magnetic and foil bearings both possible and extremely attractive. Operation of the foil/magnetic bearing takes advantage of the strengths of each individual bearing while minimizing each others weaknesses. In this paper one possible hybrid foil and magnetic bearing arrangement is investigated and sample design and operating parameters are presented. One of the weaknesses of the foil bearings, like any hydrodynamic bearing, is that contact between the foil bearing and the shaft occurs at rest or at very low speeds and it has low load carrying capacity at low speeds. For high speed applications, AMBs are, however, vulnerable to rotor-bending or structural resonances that can easily saturate power amplifiers and make the control system unstable. Since the foil bearing is advantageous for high speed operation with a higher load carrying capacity, and the magnetic bearing is so in low speed range, it is a natural evolution to combine them into a hybrid bearing system thus utilizing the advantages of both.
To take full advantage of the foil and magnetic elements comprising a hybrid bearing, it is imperative that the static and dynamic characteristics of each bearing be understood. This paper describes the development of a new analysis technique that was used to evaluate the performance of a class of gas-lubricated journal bearings. Unlike conventional approaches, the solution of the governing hydrodynamic equations dealing with compressible fluid is coupled with the structural resiliency of the bearing surfaces. The distribution of the fluid film thickness and pressures, as well as the shear stresses in a finite-width journal bearing, are computed. Using the Finite Element (FE) method, the membrane effect of an elastic top foil was evaluated and included in the overall analytical procedure. Influence coefficients were generated to address the elasticity effects of combined top foil and elastic foundation on the hydrodynamics of journal bearings, and were used to expedite the numerical solution. The overall program logic proved to be an efficient technique to deal with the complex structural compliance of various foil bearings. Parametric analysis was conducted to establish tabulated data for use in a hybrid foil/magnetic bearing design analysis. A load sharing control algorithm between the foil and magnetic elements is also discussed.
CO2 Emission Abatement in IGCC Power Plants by Semiclosed Cycles: Part B — With Air-Blown Combustion and CO2 Physical Absorption
Authors: Chiesa Paolo , Lozza Giovanni 
Published: December 2014

This paper analyzes the fundamentals of IGCC power plants with carbon dioxide removal systems, by a cycle configuration alternative to the one discussed in Part A (with Oxygen-Blown Combustion). The idea behind this proposal is to overcome the major drawbacks of the previous solution (large oxygen consumption and re-design of the gas turbine unit), by means of a semiclosed cycle using air as the oxidizer. Consequently, combustion gases are largely diluted by nitrogen and cannot be simply compressed to produce liquefied CO2 for storage or disposal. However, CO2 concentration remains high enough to make separation possible by a physical absorption process. It requires a re-pressurization of the flow subtracted from the cycle, with relevant consequences on the plant energy balance.
The configuration and the thermodynamic performance of this plant concept are extensively addressed in the paper. As in the first part, the influence of the pressure ratio is discussed, but values similar to the ones adopted in commercial heavy-duty machines provide here acceptable performance. Proper attention was paid to the impact of the absorption process on the energy consumption. The resulting net overall efficiency is again in the 38–39% range, with assumptions fully comparable to the ones of Part A. Finally, we demonstrated that the present scheme enables the use of unmodified machines, but large additional equipment is required for exhausts treatment and CO2 separation. A final comparison between the two semiclosed cycle concepts was therefore addressed.
A Combustor Can With 1.8 mm Thick Plasma Sprayed Thermal Barrier Coating
Authors: Wigren Jan , Dahlin Jens , Hansson Mats-Olov 
Published: December 2014

The benefits of thermal barrier coatings for protection of combustor walls are well known. However, the trend to higher combustor inlet temperatures and the reduced availability of cooling air leads to a demand for better insulation performance from the thermal barrier coating (TBC). This is of particular benefit for low emission combustors where wall quenching effects need to be minimised and often hot side cooling is not permissible.
A combustor can, for advanced stationary gas turbines, with 1.8 mm thick thermal barrier was designed and tested. The can was compared to a combustor can with a thermal barrier coating sprayed with current state-of-the-art methods, but to the same thickness.
Steps to optimise performance were taken in all development stages. The design allowed easy spray geometries, improved edges and no film cooling. Spraying was optimised in order to achieve a segmented microstructure for reduction of stresses (by decrease of the Young’s Modulus in the coating) and increase compliance of the coating. Testing in component test rigs showed excellent results. The lifetime of the optimised combustor can was beyond test capabilities, whereas the reference combustor failed immediately.
Metallographic and X-ray characterisation before and after component rig testing was performed and revealed features that explain the superiority of the segmented thermal barrier coating.
This work has been funded by the CEC under the contract BRE-CT94-0936.
A Study of Hydrogen Combustion Turbines
Authors: Aoki S. , Uematsu K. , Suenaga K. , Mori H. , Sugishita H. 
Published: December 2014

A hydrogen combustion turbine system has been proposed by Mitsubishi Heavy Industries, LTD. which is the Closed Circuit Cooled Topping Recuperation Cycle (CCCTR cycle) and is part of a Japanese government sponsored program WE-NET (“World Energy Network”). This cycle is composed of closed Brayton and Rankine cycles. The efficiency of this cycle is more than 60% HHV (Higher Heat Value) with a power capacity of 500MW. This cycle was selected as the most suitable for hydrogen combustion turbine used for industrial power plant by the Japanese government.
A closed circuit steam cooling system has been proposed to cool vanes and blades of the high temperature turbine (HIT) which has inlet temperature of 1700°C and inlet pressure of 45bar.
This paper presents the comparisons of the thermal efficiency and the feasibility of components between the CCCTR cycle and other cycles.
Absorption of CO2 With Amines in a Semiclosed GT Cycle: Plant Performance and Operating Costs
Authors: Corti A. , Lombardi L. , Manfrida G. 
Published: December 2014

A CO2 removal system, using aqueous solutions of amines, is applied to a Semi-Closed Gas Turbine/Combined Cycle (SCGT/CC) power plant.
The SCGT/CC is interesting because of the possibility of achieving low emissions at the stack, with a decreased overall flow rate, lower NOx concentration and an increased CO2 concentration (over 15% in volume), which facilitates the removal treatment.
Several compositions of the absorbing solution have been investigated, by means of simulations with ASPEN PLUS.
A 18% DEA + 12% MDEA composition resulted the most convenient in terms of flow rate and energy requirement for the stripping.
A cost analysis of the removal plant allows to estimate additional costs for CO2 removal with respect to conventional power plants.
Shift Reactors and Physical Absorption for Low-CO2 Emission IGCCs
Authors: Chiesa Paolo , Consonni Stefano 
Published: December 2014

Integrated Gasification Combined Cycles (IGCC) exhibit conditions particularly favourable to the sequestration of CO2. The concept pursued in this paper is the generation of syngas low in carbon, where most of the heating value of the coal fuel is carried by hydrogen. Catalytic shift reactors convert most of the CO in the syngas into CO2, which is subsequently removed by physical absorption and then compressed to make it suitable for transport and permanent storage.
Energy balances, performance and cost of electricity are evaluated for two plants based on a Texaco gasifier and a large, heavy-duty gas turbine giving an overall IGCC power output between 350 and 400 MW. In one plant the raw syngas exiting the gasifier is cooled in a high-temperature, radiative cooler; in the other it is quenched by the injection of liquid water.
With respect to “conventional” Texaco IGCCs, the reduction of specific CO2 emissions by 90% reduces LHV efficiency from 5 to 7 percentage points and increases the cost of electricity of about 45%. These penalties can be reduced by accepting lower reductions of CO2 emissions. Compared to the semi-closed cycle considered by other authors, where CO2 is the main component of the gas turbine working fluid, the plants analyzed here exhibit higher efficiency over the whole range of specific CO2 emissions.
LM2500+ Single Shaft Combined Cycle With Frequency Stabilization
Authors: Kolp Donald A. , Levey Charles E. 
Published: December 2014

Zorlu Enerji needed 35 MW of reliable power at a stable frequency to maintain constant speed on the spindles producing thread at its parent company’s textile plant in Bursa, Turkey. In December of 1996, Zorlu selected an LM2500+ combined cycle plant to fill its power-generating requirements.
The LM2500+ has output of 26,810 KW at a heat rate of 9,735 Kj/Kwh. The combined cycle plant has an output of 35,165 KW and a heat rate of 7,428 Kj/Kwh.
The plant operates in the simple cycle mode utilizing the LM2500+ and a bypass stack and in combined cycle mode using the 2-pressure heat recovery steam generator and single admission, 9.5 MW condensing steam turbine. The generator is driven through a clutch by the steam turbine from the exciter end and by the gas turbine from the opposing end. The primary fuel for the plant is natural gas; the backup fuel is naphtha.
Utilizing a load bank, the plant is capable of accepting a 12 MW load loss when the utility breaker trips open; it can sustain this loss while maintaining frequency within 1% on the mill load. The frequency stabilizing capability prevents overspeeding of the spindles, breakage of thousands of strands of thread and a costly shutdown of the mill.
A description of the equipment, operation and performance illustrates the unique features of this versatile, compact and efficient generating unit.
Comparative Analysis of Gas Turbine Engine Starting
Authors: Beyene Asfaw , Fredlund Terry 
Published: December 2014

Electric, pneumatic, combustion, and hydraulic systems are commonly used as gas turbine engine starters. All such starters must allow full-load engine operation to be reached within few or several minutes, depending on the size and type of the engine. This contrast in the power source of these starters imposes a variation in their operations including control procedures and safety measures such as blow-downs and on/off sequences. Driving characteristics such as dynamic and static behaviors of these starters also vary significantly, depending on the type of starter and the size or configuration (single or multiple shafts) of the engine to be started.
This paper provides an overall comparative background of the commonly available gas turbine engine starters. It also presents numerical results comparing hot start characteristics of single, two, and three shaft engines with cold and hot ends. The possibility of a safe engine hot starting is a valid asset in some service areas, mainly military applications. The comparisons include starter power and gas producer speed (NGP) as the function of engine acceleration, and also starter torque as a function of the % NGP. Fuel consumption of the engine during the hot start is simulated and presented as a function of the load. The impact of an engine configuration on engine starting characteristics is implicated.