Lifing methods and safety criteria in aero gas turbines

Modern gas turbines engines concentrate high power into a relatively small machine, e.g. more than 50 MW in each engine suspended from the aircraft wing in a large civil transport application. The rotational speed of the shafts reaches as high as 13,000 rpm in large engines and even higher in smaller engines as used in helicopters. Hence there is both a concentration of thermal energy in the combustion process and kinetic energy in the rotating parts that presents issues for structural integrity. This paper describes the regulatory requirements that must be achieved to allow operation of engines in civil applications and at how these requirements are satisfied in practice. It concentrates on those parts whose failure can directly threaten the integrity of the airframe through the generation of hazardous effects. The main issues are associated with fatigue through cyclic operation of the engine and the ability of the engine to survive abnormal conditions in such a way that the aircraft can safely land and be brought to rest.     

Spiral weight for modeling cracks in meshless numerical methods

In the last decade several different approaches have been developed to study arbitrary static and dynamic cracks. Among these methods meshless techniques play an important role. These methods provide an accurate solution of a wide range of fracture mechanics problems while traditional methods such as finite element and boundary element have limitations. We wish to increase the accuracy of the meshless approximations without increasing the nodal density. This is done by an appropriate modification of the weight function near crack tips. Earlier attempts still had limitations that result in a lack of accuracy, especially in the case when a linear basis is used. In this work a new technique, the spiral weight, is introduced that minimizes the drawbacks of existing methods. Numerical examples show that the spiral weight method is more efficient than existing methods, when using a linear basis, for the solution of crack problems.     

Corrosion in coal-fired gas turbines

The purpose of this paper is to review corrosion processes and experience related to coal-fired gas turbines. For over 40 years there have been major programmes of research directed towards burning coal in a gas turbine either directly or as a coal-derived fuel. This history is briefly reviewed, demonstrating the importance which corrosion of the hot section has had in limiting the achievements and defining the systems. The probable corrosion mechanisms are identified, and because of their synergistic interaction with corrosion, erosion and deposition are also considered. The discussion identifies pressurized fluidized bed combustion (PFBC) as the direct combustion technique most likely to be able to avoid serious corrosion problems in the immediate future. Recent results from PFBC pilot plant investigations related to turbine materials are compared, and thereby future directions for overcoming corrosion problems are proposed. MST/449     

Applying methods of numerical modeling to optimize a plasma burner of atmospheric pressure

The shape of a plasma burner is optimized by the methods of numerical modeling. Vortex-free flow is created in the burner merely at the expense of selecting the external tube profile rather than by introduction of additional protective flows into the burner.A. A. Blagonravov Institute of Metallography, Russian Academy of Sciences, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 3, pp. 325–331, September, 1993.     

Relevance of the small crack problem to lifetime prediction in gas turbines

The anomalous behaviour of ‘small’ fatigue cracks is summarized, and the current bases for understanding this phenomenon are discussed. The limited literature pertaining to small cracks in nickel-base superalloys is reviewed, and the consequences of this behaviour upon the lifetime prediction of gas turbines are evaluated for a typical case. Evaluation of lifetimes using large crack data is found to be non-conservative, especially at lower stress (longer lifetimes). It is shown that improvement in the resolution of non-destructive inspection techniques leads to even greater discrepancy between lifetime estimates based on small crack or large crack growth rate data.     

Forging of blades for gas turbines

Abstract

Forging technology has been developed to the point where wrought nickel alloy turbine blades can be manufactured to accurate dimensional tolerances and consistent metallurgical characteristics. Metallurgists and engineers have utilized theoretical knowledge and practical understanding of nickel superalloys and the forging process to meet the ever-increasing temperature and stress demands of turbine engines. New materials, forging techniques, and the use of computer-aided design and manufacturing systems are being developed to compete with advanced casting technology.

MST/259     

Hot corrosion site environment in gas turbines

The importance and complexity of environmental influences on the hot corrosion process in gas turbines is now recognized. The present paper seeks to emphasize that the hot corrosion phenomenon is the end product of a chain of events which starts at the air / sea interface (encompassing wind speed, relative humidity, intake siting, etc) and which extends through filter performance, compressor operating characteristics, and flame tube design before terminating at the hot corrosion site, i.e. the high-pressure rotors. Attention is particularly drawn to the influence exerted by both salt and carbon particulate material and their interrelationship with each engine stage upstream of the turbine.     

Infra-red radiation thermometry applied to the development and control of gas turbines

Efficient gas turbines operate close to their thermal limits. Detailed temperature mapping of rotating components is needed in development and reliable monitoring in operation. These needs are being met by infra-red radiation thermometers. These thermometers represent a quantum leap in performance over familiar industrial instruments.     

Lifing issues in hot gas path components of heavy-duty gas turbines

Abstract

Gas turbine hot-gas-path components, which include combustion liners, transition pieces, turbine nozzles and turbine buckets, are exposed to hot gases discharged from combustion systems and suffer from severe materials degradation and damage even in the early stage of operation. The severity of the damage and degradation increases with increasing inlet temperature and size of the gas turbines, which also increase the maintenance cost. ‘Lifing’ of components is, therefore, becoming a very critical issue. This paper describes several kinds of component damage and material degradation occurring in the 1,100°C- and 1,300°C-class heavy-duty gas turbines and then shows how we revised those component lives from the original design ones. Analytical-based assessment methods associated with condition-based assessment ones, some examples of assessment results, and component life extension technologies are also described.     

Bird's substitute tests results and evaluation of available numerical methods

Recent bird impact tests were conducted using gelatine as a bird substitute. A recipe for the gelatine is suggested in order to use as a reference in further bird test certification procedures. Results from the tests are also given so that they can be used to validate numerical models and promote the use of numerical tools in aircraft design and certification process.     

Utilisation of sludge gas for power generation through aero gas turbines

Utilisation of sludge gas as a fuel for power generation in gas turbines is discussed. Such a scheme is likely to be very cost effective particularly when the gas turbines are derived from aircraft after their flying life is over. The development and preliminary trials of a demonstration plant in Bangalore, based on a Rolls Royce “Dart” turbo-prop engine were promising and are described here. It is estimated that with the present proposal it may be feasible to meet over 30% of the domestic consumption of electricity under favourable conditions.     

Fuzzy logic controller to improve parameters affecting gas turbines power generation

In order to improve the performance of the gas turbine power plant and to generate electricity at the best cost, a fuzzy logic controller model was used to show the effect of different parameters on the power generation output of gas turbines. The proposed methodology was applied to certain parameter values collected from Rehab power station in Jordan—as a case study—for validation purposes. Relative weights were used, i.e., very very low power generation “extremely low power generation,” very low power generation, low power generation, normal power generation, high power generation, and very high power generation. The study reveals that the major factors that affect yield are ambient temperature (T ₁), compressor’s exit temperature (T ₂), turbine’s inlet temperature (T ₃), turbine exit temperature (T ₄), pressure ratio (R _p), mass of fuel (M _f), relative humidity (H), turbine efficiency (η_t), and compressor efficiency (η_c). Based on the increase of productivity, the results show that different factors are found to affect the yield of a power generator. Therefore, using fuzzy logic controller model has lead the researchers to focus on the highest priority parameters that should be enhanced and developed to increase the power output productivity.     

Development of ceramic components for car gas turbines

Components for internal combustion engines are being develop ed from non-oxide and oxide ceramzc r:naterzals at the Research Division of Volkswagenwerk AG. The properties of some materials, the process technology and the design methods of the components are discussed. The advantages of the incorporation of ceramics into automotive gas turbines are deduced and th e present state of Volkswagen’s component development is reported.     

回热循环燃气轮机中回热器的动态特性研究

采用多段集中参数模型对具有分布参数特性的回热器建模，简化了由偏微分方程带来的大量计算，应用Matlab／Simlink软件作为仿真平台，采取数值方法求解，对具体回热燃气轮机中的回热器进行了仿真，结果表明，回热器时间常数较大，在回热循环燃气轮机仿真中回热器的热惯性不能忽略，而且是影响系统平衡稳定性的重要因素．     

Strength of guide vane components of gas turbines

The article presents an analysis of the main kinds of damage to elements of guide vanes of gas turbine engines: cracking, irreversible deformations, bending of the vane edges. Methods are described for calculating the safety factor of guide vane components under conditions of loading by heat cycling on the basis of the theory of adaptability.Leningrad. Translated from Problemy Prochnosti, No. 11, pp. 119–124, November, 1989.     

Experience with platinum aluminide coatings in land-based gas turbines

Hot-corrosion crucible tests with salt mixtures which simulated actual blade deposits were carried out to evaluate the potential of platinum-modified aluminide coatings for application in advanced industrial gas turbines. In comparison with simple aluminide coatings, a significantly improved resistance against hot corrosion at intermediate temperatures was found. At the highest turbine-operating temperature, coating life exceeds that of conventional plasma-sprayed NiCrSi coatings. Actual engine test results are presented which confirm the beneficial role of platinum. However, the susceptibility of platinum aluminide coatings to crack formation and propagation may make them unsuitable for application to rotating blades.