Connecting the second exhaust-heat boiler to the operating first one under the conditions of flow circuits of combined-cycle plants with two gas-turbine units and one steam turbine

Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer) is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined. __________ Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17.     

We All Know That a0 = 1, But Can You Explain Why?

This article is concerned with exploring the mathematical knowledge and reasoning that can be engaged in providing explanations for the convention a⁰ = 1. Posts from online open forums are used to illustrate the variety of mathematical ideas that can be utilized in the explanations. The explanations are examined in terms of quality criteria of definitions and proofs.     

Methodical Fundamentals for Constructing Startup Assignment Schedules for Combined-Cycle Power Plants Considering Damage Accumulation

Depending on the requirements for power plants at thermal power stations (TPS), alternative approaches can be used for constructing assignment schedules to start power units from different initial thermal states. This issue becomes topical for combined-cycle power plants (CCPP) with heat-recovery steam generators (HRSG) whose thermal cycle includes gas turbines featuring excellent maneuverability and a steam system with equipment characterized by a relatively low loading rate. This paper examines an approach to construction of assignment schedules for CCPP starting based on accumulation of damages of the most heavily loaded thickwall elements in the steam path to meet the requirements for CCPP maneuverability during the entire service life of a CCPP. A principle is proposed for constructing an assignment schedule for starting a CCPP from any initial thermal state within the desired time provided that the number of these startups would not exceed the prescribed limit value determined in assessing the damage accumulation. Assignment schedules must be prepared based on the monitored temperature conditions of CCPP equipment, the allowable limits for predicted temperature stresses, and the allowable number of cycles determined by the low-cycle fatigue.     

Calculation of low-cycle fatigue in accordance with the national standard and strength codes

Over the most recent 15 years, the Russian power industry has largely relied on imported equipment manufactured in compliance with foreign standards and procedures. This inevitably necessitates their harmonization with the regulatory documents of the Russian Federation, which include calculations of strength, low cycle fatigue, and assessment of the equipment service life. An important regulatory document providing the engineering foundation for cyclic strength and life assessment for high-load components of the boiler and steamline of a water/steam circuit is RD 10-249-98:2000: Standard Method of Strength Estimation in Stationary Boilers and Steam and Water Piping. In January 2015, the National Standard of the Russian Federation 12952-3:2001 was introduced regulating the issues of design and calculation of the pressure parts of water-tube boilers and auxiliary installations. Thus, there appeared to be two documents simultaneously valid in the same energy field and using different methods for calculating the low-cycle fatigue strength, which leads to different results. In this connection, the current situation can lead to incorrect ideas about the cyclic strength and the service life of high-temperature boiler parts. The article shows that the results of calculations performed in accordance with GOST R 55682.3-2013/EN 12952-3: 2001 are less conservative than the results of the standard RD 10-249-98. Since the calculation of the expected service life of boiler parts should use GOST R 55682.3-2013/EN 12952-3: 2001, it becomes necessary to establish the applicability scope of each of the above documents.     

Kernel methods for learning languages

This paper studies a novel paradigm for learning formal languages from positive and negative examples which consists of mapping strings to an appropriate high-dimensional feature space and learning a separating hyperplane in that space. Such mappings can often be represented flexibly with string kernels, with the additional benefit of computational efficiency. The paradigm inspected can thus be viewed as that of using kernel methods for learning languages.     

Some comments on the use of markov models in communications

In their recent article Feng, Field and Haykin rediscovered an approach to the channel modelling based on stochastic differential equations (SDE). In the following we would like to bring readers attention to a body of literature which deals with similar subjects using SDE approach.