Heat transfer intensity of pulsating gas flows in the exhaust system elements of a piston engine

Internal combustion engines are the most common sources of energy among heat engines. Therefore, the improvement of their design and workflow is an urgent task in the development of world energy. Thermal-mechanical perfection of the exhaust system has a significant impact on the technical and economic performance of piston engines. The article presents the results of experimental studies of gas-dynamics and heat exchange of pulsating gas flows in the exhaust system of a piston engine. Studies were carried out on a full-scale model of a single-cylinder engine. The article describes the instrument-measuring base and methods of experiments. The heat transfer intensity was estimated in different elements of the exhaust system: the exhaust pipe, the channel in the cylinder head, the valve assembly. Heat transfer studies were carried out taking into account the gas-dynamic nonstationarity characteristic of gas exchange processes in engines. The article presents data on the influence of gas-dynamic and regime factors on the heat transfer intensity. It is shown that the restructuring of the gas flow structure in the exhaust system occurs depending on the engine crankshaft speed, this has a significant impact on the local heat transfer coefficient. It has been established that the heat transfer intensity in the valve assembly is 2-3 times lower than in other elements of the exhaust system. © The Authors, published by EDP Sciences.Russian Science Foundation, RSF: 18-79-10003The work has been supported by the Russian Science Foundation (grant No. 18-79-10003)

Single-phase media hydrodynamics and heat transfer in heat exchangers with twisted profile tubes

A profiled heat exchanger tube is the one in which some features have been incorporated into the tube geometry for heat transfer enhancement. They offer a perspective method of steam turbine shell-and-tube heat exchangers improvement. Twisted profile tubes (TPT) are widely used in power engineering. This paper presents some results of experimental and theoretical research of hydrodynamics and heat transfer in TPTs. It is revealed that the heat transfer coefficient for water flow in a TPT increases up to 80% compared to that of a plain tube. With a rise of media Reynolds number, the heat transfer rate in a TPT decreases in comparison to that of a plain tube, but for air flow in a TPT the heat transfer coefficients ratio does not depend on the Reynolds number value. Water flow hydraulic losses in TPTs increase from 15 to 100% depending on the tube profile parameters. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen

Development of a procedure for substantiating replacement terms for the condenser tubes of steam turbine installations

Results obtained from elaboration of a procedure for estimating replacement terms for the condenser tube systems of steam turbine installations are presented. Censored data processing methods are used in performing statistical assessment of replacement terms. The service life of condenser tubes blanked off in the course of turbine operation is assumed to be known (complete operation time), and that for tubes blanked off during the turbine repair process is assumed to be undetermined (censored operation time). The criterion for estimating the replacement term for a condenser tube system is defined as the ratio between the number of tubes blanked off during a repair and in the course of turbine operation. The procedure is validated by the results from a study on analyzing the damageability of tubes made of different materials for the condensers of 11 turbines with capacities ranging from 25 to 500 MW. © 2013 Pleiades Publishing, Ltd

Heat transfer augmentation during water steam condensation on twisted profile tubes

Some results are presented of experimental and theoretical research of hydrodynamics and heat transfer during condensation of water steam (both stationary and slowly moving) on twisted profile tubes (TPT). For a heat transfer coefficient during condensation of stationary steam on TPT two characteristic areas were observed. At small values of condensate film Reynolds numbers a TPT heat transfer coefficient can be 10-15% below that of the plain tubes depending on profile parameters. With the rise of both condensate film Reynolds number and profile parameter h/s heat transfer coefficient increases up to 50% in comparison to a plain tube. During slowly moving steam condensation the TPT heat transfer coefficient increases up to 70% as compared to a plain tube. Conducted research and industrial tests results showed that the assured effect of a heat transfer coefficient increase in TPT heat exchangers could reach for turbine condensers 15%, for low cycle heaters 35-40%. The heat exchangers hydraulic resistance increases by 40-70%. © 2014 WIT Press.International Journal of Safety and Security Engineering;International Journal of Sustainable Development and Planning;WIT Transactions on Ecology and the Environmen

Modern technologies for rendering information support to cogeneration steam turbine units in their design and operation stages

Application of modern information technologies in different stages of the lifecycle of cogeneration turbines is considered as one of possible ways for improving their competitiveness. Specific features relating to rendering information support for steam turbine units during the periods of their design and operation, which are the main stages of their life cycle, are presented. Three-dimension modeling, adaptive, and parametric design technologies are applied in the equipment design stages. Information support technologies developed by the authors are applied during the operation stage. Information is integrated by using a product lifecycle management (PLM) system. © 2013 Pleiades Publishing, Ltd

Features of thermomechanics of pulsating gas flows in intake systems with grooves in relation to turbocharged engines

Reciprocating engines (RICE) are widely used as heat engines to convert the chemical energy of fuel into mechanical work on the crankshaft. Aerodynamic and thermophysical processes in gas exchange systems significantly affect the efficiency of internal combustion RICEs. This article explores the possibility of influencing the gas dynamics and heat transfer of pulsating gas flows in the intake system by placing a channel with grooves. It is known that the presence of grooves in the channel leads to the formation of significant secondary vortices, which radically change the physical picture of the gas flow. The studies are carried out on a laboratory bench, which was a single-cylinder model of a turbocharged RICE. The system of measurements of basic physical quantities is described, taking into account their high dynamics in gas exchange systems. The experimental data processing techniques are presented. Primary data on the instantaneous values of the gas-dynamic and heat-exchange characteristics of pulsating flows are reported. It is established that the presence of a channel with grooves in the intake system leads to a decrease in the turbulence number by 40% and the intensification of heat transfer in the range of 5-50% compared with the basic intake system. A positive effect is shown in the form of an increase in engine power by 3% when using an upgraded system. © Published under licence by IOP Publishing Ltd.The work has been supported by the Russian Science Foundation (grant No. 18-79-10003)

Identification of corner separation modelling in axial compressor stage

The paper presents a study of corner separations in hub to blade region at various operation conditions towards compressor stall. It is known that for compressor flows with low or none separations computation fluid dynamics with RANS methods work quite well, however, for highly separated flows they are no longer entirely valid. Therefore, several criteria were applied for prediction and quantification of possible corner separation, and the main interest of this work is in predicting the separation just before it will actually happen by certain flow metrics, so these metrics can be further used as a 'pre-stall' criteria whilst the RANS CFD operating point still behave within its appropriate limits. Also the effect of shear lean is discussed in the presented context. © The Authors, published by EDP Sciences, 2020

Redesign of an axial compressor with mass flow reduction of 30%

In this paper redesign process of an axial compressor of a Gas Turbine for mechanical drive is discussed together with computational results and experimental data. The goal of the project was to reduce compressor mass flow by 30% and at the same time to increase compressor specific work by about 10%. This could not be achieved by conventional methods such as re-staggering of Inlet Guide Vanes. Throughflow and CFD calculations were performed for redesigned versions. As a result an updated compressor was produced for the real engine and achieved design objectives. This paper shows how the swept area distribution along the compressor affects stage loading distribution and surge limits. © 2019 WIT Press

Computational and Experimental Evaluation of Heat Transfer Intensity in Channels of Complex Configuration for Gas Flow with Different Levels of Turbulence

Disclosure of the physical mechanism of the influence of the turbulence intensity of gas flows on the heat transfer level in pipes of different configurations is an urgent task in the field of heat and power engineering. A brief overview of the literature on this topic is given in the article. A description of the boundary conditions for modeling is presented. The main characteristics of the experimental stand and measuring instruments are described. The purpose of this study is to study the effect of the initial turbulence level of a stationary gas flow on the heat transfer intensity in long pipes with different cross sections. The study is carried out using numerical simulation. The simulation results are qualitatively confirmed using experimental data. The values of the local heat transfer coefficient are shown to increase from 5 to 17% with increasing turbulence intensity (from 2 to 10%) in pipes with different cross sections. The heat transfer intensity in a triangular pipe is found to increase up to 30% compared to a round pipe. It is revealed that there is an up to 15% suppression of heat transfer in a square pipe compared to a round pipe. The data obtained may be useful for the design of flow paths and gas exchange systems for power machines and installations. © 2021 Institute of Physics Publishing. All rights reserved

Turbine Diagnostics: Algorithms Adaptation Problems

Enterprises of energy equipment and operational utilities set sights on diagnostic systems. This is necessary for state control and maintenance planning of steam turbines. It is useful for digitalization purposes too. So far, some mathematical systems are already used. Algorithms for flow part, heat expansion systems, control systems, vibration-based diagnostics and auxiliary equipment have already been designed. We have designed algorithms just in principle. We met difficulties adapting them for the PT-75/80-90 turbine. Firstly, we should connect them to a single interface. Secondly, adaptation should include features of the equipment, its state (if not new), even operating conditions. Diagnostic signs for each turbine are the most important. We define them based on the operational data. When adapting the algorithms, we reconsider the signs list. We also estimate its coefficients of importance again. This requires experts to study designs, calculations, and modelling. We also analyzed a large amount of operational data at various power plants. To define the state we use tests. Adapting is based on the modes of a specific power station. Following this strategy, we adapt general algorithms for various turbines. © 2020 WIT Press