Showing papers in "Journal of Engineering for Gas Turbines and Power-transactions of The Asme in 1988"
TL;DR: In this article, a methodology is established to predict thermal barrier coating life in an environment similar to that experienced by gas turbine airfoils, and a preliminary life prediction model developed focuses on the two major damage modes identified in the critical experiments tasks.
Abstract: A methodology is established to predict thermal barrier coating life in a environment similar to that experienced by gas turbine airfoils. Experiments were conducted to determine failure modes of the thermal barrier coating. Analytical studies were employed to derive a life prediction model. A review of experimental and flight service components as well as laboratory post evaluations indicates that the predominant mode of TBC failure involves thermomechanical spallation of the ceramic coating layer. This ceramic spallation involves the formation of a dominant crack in the ceramic coating parallel to and closely adjacent to the topologically complex metal ceramic interface. This mechanical failure mode clearly is influenced by thermal exposure effects as shown in experiments conducted to study thermal pre-exposure and thermal cycle-rate effects. The preliminary life prediction model developed focuses on the two major damage modes identified in the critical experiments tasks. The first of these involves a mechanical driving force, resulting from cyclic strains and stresses caused by thermally induced and externally imposed mechanical loads. The second is an environmental driving force based on experimental results, and is believed to be related to bond coat oxidation. It is also believed that the growth of this oxide scale influences the intensity of the mechanical driving force.
227 citations
TL;DR: In this paper, the maximum power that can be extracted from an engine operating at a given condition was determined by means of analyses based on the first and second laws of thermodynamics.
Abstract: The maximum power that can be extracted from an engine operating at a given condition was determined by means of analyses based on the first and second laws of thermodynamics. These analyses were applied to a heavy-duty single-cylinder open-chamber diesel engine operated at constant speed. Over the range of operating conditions investigated, the second-law efficiency (ratio of brake power to maximum extractable power) of the engine, which increased with engine load, was found to vary from 22 to 50 percent. It was concluded that besides heat transfer, the combustion process was the most important source of irreversibility and accounted for 25 to 43 percent of the lost power.
108 citations
TL;DR: In this article, a simple equation of state for superheated and two-phase property calculations for use in these circumstances is described. But this equation is unsuitable for inclusion infinite difference flow calculation computer codes, which may require 106 property evaluations before convergence is achieved.
Abstract: Large-scale equations of state for steam used for generating tables are unsuitable for inclusion infinite difference flow calculation computer codes. Such codes, which are in common use in the turbomachinery industry, may require 106 property evaluations before convergence is achieved. This paper describes a simple equation of state for superheated and two-phase property calculations for use in these circumstances. Computational efficiency is excellent and accuracy over the range of application is comparable to that of the large-scale equations. Further advantages are that complete thermodynamic consistency is maintained and the equation can be differentiated analytically for direct substitution into the gas dynamic equations where required. A truncated virial form is used to represent superheated properties and a new empirical correlation for the third virial coefficient of steam is presented.
90 citations
TL;DR: Thesis (Ph.D.) as mentioned in this paper, Mass. Institute of Technology, Dept. of Mechanical Engineering, 1984, Boston, MA, USA, United States of America, USA.
Abstract: Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1984.
79 citations
TL;DR: In this paper, the current status and future trends in application of thermal barrier coatings (TBC) to turbine components, and in particular to high turbine airfoils, are discussed.
Abstract: This paper provides an overview of the current status and future trends in application of thermal barrier coatings (TBC) to turbine components, and in particular to high turbine airfoils. Included are descriptions of the favorable results achieved to date with bill-of-material applications of plasma deposited TBC, and recent experience with developmental coatings applied by electron beam-physical vapor deposition.
79 citations
TL;DR: Conception d'un systeme de commande non lineaire pour un moteur d'automobile a injection de carburant as discussed by the authors, which is based on an injection of carburants.
Abstract: Conception d'un systeme de commande non lineaire pour un moteur d'automobile a injection de carburant
78 citations
TL;DR: In this article, a general, dimensionless formulation of the thermodynamic, heat transfer, and fluid-dynamic processes in a cooled gas turbine is used to construct a compact, flexible, interactive system-analysis program.
Abstract: A general, dimensionless formulation of the thermodynamic, heat transfer, and fluid-dynamic processes in a cooled gas turbine is used to construct a compact, flexible, interactive system-analysis program A variety of multishaft systems using surface or evaporative intercoolers, surface recuperators, or rotary regenerators, and incorporating gas turbine reheat combustors, can be analyzed Different types of turbine cooling methods at various levels of technology parameters, including thermal barrier coatings, may be represented The system configuration is flexible, allowing the number of turbine stages, shaft/spool arrangement, number and selection of coolant bleed points, and coolant routing scheme to be varied at will Interactive iterations between system thermodynamic performance and simplified quasi-three-dimensional models of the turbine stages allow exploration of realistic turbine-design opportunities within the system/thermodynamic parameter space The code performs exergy-balance analysis to break down and trace system inefficiencies to their source components and source processes within the components, thereby providing insight into the interactions between the components and the system optimization tradeoffs
69 citations
64 citations
TL;DR: In this paper, a modified equation for calculation of the heat transfer coefficient was presented, which confirmed the effects demonstrated in [1], including the influence on the wall temperature, on the performance of naturally aspirated and turbocharged engines.
Abstract: Recently great expectations were put into the insulation of combustion chamber walls. A considerable reduction in fuel consumption, a marked reduction of the heat flow to the cooling water, and a significant increase of exhaust gas energy were predicted. In the meantime there exists an increasing number of publications reporting on significant increase of fuel consumption with total or partial insulation of the combustion chamber walls. In [1] a physical explanation of this effect is given: Simultaneously with the decrease of the temperature difference between gas and wall as a result of insulation, the heat transfer coefficient between gas and wall increases rapidly due to increasing wall temperature, thus overcompensating for the decrease in temperature difference between gas and wall. Hence a modified equation for calculation of the heat transfer coefficient was presented [1]. In the paper to be presented here, recent experimental results are reported that confirm the effects demonstrated in [1], including the influence of the heat transfer coefficient, which depends on the wall temperature, on the performance of naturally aspirated and turbocharged engines.
58 citations
TL;DR: Autoallumage d'un jet de carburant diesel and influence des proprietes du carburants et des caracteristiques de l'injection.
Abstract: Autoallumage d'un jet de carburant diesel et influence des proprietes du carburant et des caracteristiques de l'injection
57 citations
TL;DR: Nickel and cobalt-base superalloy blades and vanes in the hot sections of all gas turbines are coated to enhance resistance to hot corrosion as mentioned in this paper, which is the most widely used coating process.
Abstract: Nickel and cobalt-base superalloy blades and vanes in the hot sections of all gas turbines are coated to enhance resistance to hot corrosion. Pack cementation aluminizing, invented in 1911, is the most widely used coating process. Corrosion resistance of aluminide coatings can be increased by modification with chromium, platinum, or silicon. Chromium diffusion coatings can be used at lower temperatures. Formation and degradation mechanisms are reasonably well understood and large-scale manufacturing processes for these coatings are gradually being automated. Pack cementation and related diffusion coatings serve well for most aircraft engine applications. The trend for industrial and marine engines is more toward the use of overlay coatings because of the greater ease of designing these to meet a wide variety of corrosion conditions.
TL;DR: In this paper, a modified intercooled/recuperated cycle was compared with nonintercooled steam-injected gas turbine systems at each component technology level and the present cycle was found to be superior by about 2.75 percentage points in efficiency and to require a substantially smaller water flow rate.
Abstract: The thermal efficiency of an intercooled/recuperated cycle may be increased by: (a) evaporatively aftercooling the compressor discharge; and (b) injecting and evaporating an additional amount of water in the recuperator. Comparative computations of such a modified cycle and intercooled/recuperated cycles carried out over a wide range of pressure ratios and turbine inlet temperatures and at two different levels of component technologies show an advantage of over five percentage points in efficiency for the modified cycle. About 60 percent of this improvement results from modification (a) and 40 percent from modification (b). The modified intercooled/recuperated cycle is compared with nonintercooled steam-injected gas turbine systems at each component technology level. The present cycle is found to be superior by about 2.75 percentage points in efficiency and to require a substantially smaller water flow rate. To assist in interpreting those differences, the method of available-work analysis is introduced and applied. This is identical to exergy analysis for systems with a pure-substance working fluid, but differs from the latter for systems using a mixture of pure substances insofar as the thermodynamic dead state is defined for the chemical and phase composition realized at the exhaust conditions of practical engineering devices and systems. This analysismore » is applied to the heat-recovery processes in each of the three systems considered. It shows that the substantial, fundamental available-work loss incurred by mixing steam and gases in the steam-injected system is the main reason for the superior efficiency of the precent cycle.« less
TL;DR: In this paper, an analytical procedure for calculating the performance of a two-phase flow screw-type expander is presented, compared with experimental measurements made with a recently developed prototype expander.
Abstract: An analytical procedure for calculating the performance of a two-phase flow screw-type expander is presented. Predicted results are compared with experimental measurements made with a recently developed prototype expander. This expander was designed for investigating the applicability of this type of machine as the expansion device in refrigeration or heat pump cycles with the objective of taking advantage of the power-producing capability of the expanding fluid. It has two rotors each with a diameter of 81.6 mm and a length of 135 mm, and was operated with Freon-12 entering at a pressure of 1.588 MPa (230.4 psia) and subcooling of between 2 and 12 K. Maximum power generated was 10 kW at a rotor speed of 3000 rpm. The internal (machine) efficiency is predicted to increase from about 30 to 70 percent as the rotor speed increases from 500 to 3000 rpm. Experimental results over the same speed range increase from 30 to 60 percent. The low experimental values at the higher rotor speeds are attributed primarily to frictional losses not included in the analysis. Estimates of the performance of machines with larger diameter rotors yielded internal efficiencies reaching 80 percent and increases in power output proportional to the squaremore » of the rotor diameter.« less
TL;DR: The influence de l'inertie du fluide sur les performances d'un rotor monte sur des amortisseurs a film comprime is discussed in this paper.
Abstract: Influence de l'inertie du fluide sur les performances d'un rotor monte sur des amortisseurs a film comprime
TL;DR: In this article, the performance characteristics of prefilming airblast atomizers depend largely on the shear stresses in each of the two air supply channels, and it was shown that the quality of atomization can be limited due to internal droplet formation.
Abstract: The performance characteristics of prefilming airblast atomizers depend largely on the shear stresses in each of the two air supply channels. As an extension of previously reported results, experiments were conducted using an atomizer model with separately controlled air ducts and typical prototype nozzles. It was shown that the quality of atomization can be limited due to internal droplet formation. However, the velocity profiles of the atomization air and the properties of the liquid are the dominant parameters that determine the drop-size distribution generated at the atomization edge. The shear flow at the nozzle exit and the recirculation zone depend largely on the swirl or counterswirl of the exiting air. Correlations are obtained between the spray characteristics and the relevant parameters.
TL;DR: In this article, the authors investigated leakage flow and heat transfer of scaled-up stepped labyrinth seals under steady conditions in a test rig under different geometries and pressure ratios, using finite element programs to determine the temperature distribution and subsequently heat transfer coefficients.
Abstract: Leakage flow and heat transfer of scaled-up stepped labyrinth seals were investigated experimentally and numerically. The experiments were conducted in a test rig under steady conditions. For different geometries and pressure ratios a finite element program was used to determine the temperature distribution and subsequently the heat transfer coefficients. In verifying the experimental results, the flow field of the seals was calculated numerically by a finite difference program. Heat transfer coefficients were derived utilizing the well-known analogies between heat transfer and wall friction.
TL;DR: In this article, the recepteur solaire comprenant un systeme de stockage thermique a materiau a changement de phase (melange eutectique de LiF and CaF 2 ) permettant la production d'energie pendant les eclipses se produisant sur les orbites basses.
Abstract: Conception et developpement du recepteur solaire comprenant un systeme de stockage thermique a materiau a changement de phase (melange eutectique de LiF et CaF 2 ) permettant la production d'energie pendant les eclipses se produisant sur les orbites basses
TL;DR: In this article, the authors compare on both an ideal and, where possible, an actual basis the approximate performances of four types of pressure-gain combustors, which are potentially suitable for use in gas turbines in place of conventional steady-flow combustors.
Abstract: The objective of the work was to compare on both an ideal and, where possible, an actual basis the approximate performances of four types of pressure-gain combustor. Such combustors are potentially suitable for use in gas turbines in place of conventional steady-flow combustors. The ideal theoretical performance comparison was based on a specially conceived, universal, analytical model capable of representing, in a fundamental manner, the dominant features of each of the systems studied. The comparisons of nonideal performance were based on actual test results and, where these were not available, on ideal performance characteristics suitably modified to take irreversibilities, etc., into account. It was found that in general the pressure-gain potential of the concepts studied increased with increasing system complexity. It was also found that with most concepts the combustor pressure ratio achievable increases with combustor temperature ratio.
TL;DR: In this paper, the influence of torsional-lateral coupling on the stability behavior of a simple geared system supported by oil film bearings is investigated by parameter studies and a sensitivity analysis for the uncoupled and coupled system.
Abstract: In high-performance turbomachinery trouble often arises due to unstable asynchronous lateral vibrations. The instabilities are mostly caused by oil film bearings, clearance excitation, internal damping, annular pressure seals in pumps, or labyrinth seals in turbocompressors. In recent times as an additional influence the coupling between torsional and lateral vibrations is considered, which is of practical importance in geared rotor systems. In the literature [1, 2], some field problems are described, where in geared drive trains unstable lateral vibrations occurred together with torsional oscillations. This presentation studies the influence of torsional-lateral coupling on the stability behavior of a simple geared system supported by oil film bearings. The coupling effect is investigated by parameter studies and a sensitivity analysis for the uncoupled and the coupled system.
TL;DR: In this paper, the modele dynamique d'un moteur diesel de locomotive et de son systeme de regulation electrohydraulique is described, as well as the system of regulation electrohybrid.
Abstract: Modele dynamique d'un moteur diesel de locomotive et de son systeme de regulation electrohydraulique
TL;DR: In this article, the authors present an overview of a method used to model windage rise and ingestion on a macroscopic scale and compare the model results to engine test data.
Abstract: Typically cooling air must be metered into cavities bordering turbine disks to offset cavity air temperature rise due to windage generated by air drag from rotating and stationary surfaces and the ingestion of hot mainstream gas. Being able to estimate the minimum amount of cooling air required to purge turbine rim cavities accurately is important toward providing optimum turbine cycle performance and hardware durability. Presented is an overview of a method used to model windage rise and ingestion on a macroscopic scale. Comparisons of model results to engine test data are included.
TL;DR: Etude experimentale de la dispersion and de la combustion d'un jet de carburant diesel (dispersion par un procede electrostatique) as mentioned in this paper.
Abstract: Etude experimentale de la dispersion et de la combustion d'un jet de carburant diesel (dispersion par un procede electrostatique)
TL;DR: In this paper, the GE 7FDL single-cylinder research diesel engine, coal-water slurry (CWS) fuel combustion optimization studies were conducted using electronically controlled CWS and pilot accumulator injectors.
Abstract: This paper reports that in the GE 7FDL single-cylinder research diesel engine, coal-water slurry (CWS) fuel combustion optimization studies were conducted using electronically controlled CWS and pilot accumulator injectors. The most important performance parameters of peak firing pressure, combustion efficiency (coal burnout) and specific fuel consumption were evaluated in relationship to CWS and pilot injection timing, CWS injector hole size, shape, and number, CWS fuel injection spray angles and injection pressure. Heat release diagrams, as well as exhaust samples (gaseous and particulate), were analyzed for each case. Interesting effects of fuel spray impingement and CWS fuel Delayed Ignition were observed. With the engine operating at 2.0 MPa IMEP and 1050 rpm, it was able to obtain over 99.5 percent combustion efficiency while holding the cylinder firing pressure below 17 MPa and thermal efficiency equivalent to diesel fuel operation.
TL;DR: The influence des conditions de l'injection sur les emissions d'hydrocarbures d'un petit moteur diesel a chambre ouverte is discussed in this article.
Abstract: Influence des conditions de l'injection sur les emissions d'hydrocarbures d'un petit moteur diesel a chambre ouverte. On etudie deux phenomenes: le melange trop pauvre a la peripherie du jet; la penetration trop profonde du jet a l'interieur de la chambre
TL;DR: The influence of l'amplitude and de la distribution des vitesses a l'admission sur l'intensite de la turbulence dans les cylindres and le taux de combustion dans un moteur is discussed in this article.
Abstract: Influence de l'amplitude et de la distribution des vitesses a l'admission sur l'intensite de la turbulence dans les cylindres et le taux de combustion dans un moteur. Comparaison entre theorie et experience