Search results

The purpose of this study is to model steam condensing flows through steam turbine blades and find the most suitable condensation model to predict the condensation phenomenon.

To find the most suitable condensation model, five nucleation equations and four droplet growth equations are combined, and 20 cases are considered for modelling the wet steam flow through steam turbine blades. Finally, by the comparison between the numerical results and experiments, the most suitable case is proposed. To find out whether the proposed case is also valid for other boundary conditions and geometries, it is used to simulate wet steam flows in de Laval nozzles.

The results indicate that among all the cases, combining the Hale nucleation equation with the Gyarmathy droplet growth equation results in the smallest error in the simulation of wet steam flows through steam turbine blades. Compared with experimental data, the proposed model’s relative error for the static pressure distribution on the blade suction and pressure sides is 2.7% and 2.3%, respectively, and for the liquid droplet radius distribution it totals to 1%. This case is also reliable for simulating condensing steam flows in de Laval nozzles.

The selection of an appropriate condensation model plays a vital role in the simulation of wet steam flows. Considering that the results of numerical studies on condensation models in recent years have not been completely consistent with the experiments and that there are still uncertainties in this field, further studies aiming to improve condensation models are of particular importance. As condensation models play an important role in simulating the condensation phenomenon, this research can help other researchers to better understand the purpose and importance of choosing a suitable condensation model in improving the results. This study is a significant step to improve the existing condensation models and it can help other researchers to gain a revealing insight into choosing an appropriate condensation model for their simulations.

The purpose of this paper is to study the condensation flow of wet steam in the last stage of a steam turbine and to obtain the distribution of condensation parameters such as nucleation rate, Mach number and wetness.

Because of the sensitivity of the condensation parameter distribution, a double fluid numerical model and a realizable k-ε-k_d turbulence model were applied in this study, and the numerical solution for the non-equilibrium condensation flow is provided.

The simulation results are consistent with the experimental results of the Bakhtar test. The calculation results indicate that the degree of departure from saturation has a significant impact on the wet steam transonic condensation flow. When the inlet steam deviates from the saturation state, shock wave interference and vortex mixing also have a great influence on the distribution of water droplets.

The research results can provide reference for steam turbine wetness losses evaluation and flow passage structure optimization design.

The purpose of this study is to improved the efficiency of condensing steam turbines by legitimately reforming the flow structure. It is of great significance to study the condensation flow characteristics of wet steam for optimizing the operation of condensing steam turbines.

A two-fluid model was used to study the wet steam flow in a stator cascade. The effects of the inlet temperature and pressure drop on the cascade performance were analyzed. On this basis, endwall protrusion models were set up at varied axial position on the pressure surface to evaluate the wetness control and loss under different design conditions for cascade optimization.

The analysis indicates that increasing the inlet temperature or decreasing the pressure drop can effectively control the steam wetness but increase the droplet radius. The increasing inlet temperature can delay the condensation and alleviate the deterioration of the aerodynamic performance of cascades. The non-axisymmetric endwall can significantly affect the distribution of steam parameters below its height and slightly reduce the droplet radius. Compared with the original stator cascade, the optimum design conditions reduce the steam wetness by 8.07 per cent and the total pressure loss by 6.91 per cent below a 20 per cent blade height.

These research results can serve as a reference for condensing steam turbine wetness losses evaluation and flow passage optimization design.

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal radiation and hot steam.

An experiment-based model was introduced to analyze heat and moisture transfer in the vertical air gap between the protective clothing and human body. A developed test apparatus was used to simulate different air gap sizes (3, 6, 9, 12, 15, 18, 21 and 24 mm). The protective clothing with different air gap sizes was subjected to dry and wet heat exposures.

The increase of the air gap size reduced the heat and moisture transfer from the protective clothing to the skin surface under both heat exposures. The minimum air gap size for the initiation of natural convection in the dry heat exposure was between 6 and 9 mm, while the air gap size for the occurrence of natural convection was increased in the wet heat exposure. In addition, the steam mass flux presented a sharp decrease with the rising of the air gap size, followed by a stable state, mainly depending on the molecular diffusion and the convection mass transfer.

This research provides a better understanding of the optimum air gap under the protective clothing, which contributes to the design of optimum air gap size that provided higher thermal protection against dry and wet heat exposures.

A lesser known strength of Texaco is as a supplier of lubricants to the operators of old steam engines.

This case deals with steps taken by NTPC in construction and project management in 500 MW power plant. The project have several innovative ways of managing challenges, in land acquisition, design, implementation, contract worker management, enforcement of safety rules, managing regulation iand in team building in leadership. A suitable case for site management, it shows in spite of being a public sector undertaking, how the project was constructed in record time of 42 months.

The flow state of wet steam will affect the thermodynamic and aerodynamic characteristics of steam turbine. The purpose of this study is to effectively control the wetness losses caused by wet steam condensation, and hence a cascade of 600 MW steam turbine was taken as the research object.

The influence of blade surface roughness on the condensation characteristics was analyzed, and the dehumidification mechanism and wetness control effect were obtained.

With the increase of blade surface roughness, the peak nucleation rate decreases gradually. According to the Mach number distribution on the blade surface, there is a sensitive region for the influence of roughness on the aerodynamic performance of cascade. The sensitive region of nucleation rate roughness should be between 50 and 150 µm.

The increase of blade surface roughness will increase the dynamic loss in cascade, but it can reduce the thermodynamic loss caused by condensation to a certain extent.

The steam engine was the first practical means of producing mechanical power from the heat of combustion of a fuel, and its introduction was a vital factor in the progress of the Industrial Revolution. For many years the development of the steam reciprocating engine continued apace, but in the early years of the present century introduction of the steam turbine and internal combustion engine made available alternative methods of power production. From then on interest in the steam reciprocating engine tended to slacken and, although it has shown a number of notable improvements, far more spectacular advances have been made in other power units.

To make clear that C‐steel can differ very much in corrosion resistance under practical conditions only because of differences in chemical composition of the steels.

In the electricity generating industry, “mild” (i.e. “plain carbon”) and low‐alloyed steels are used in huge quantities, for instance, in boilers, steam generators, heat recovery boilers and waste incineration boilers. The resistance to strain induced corrosion cracking (SICC) was determined by measuring the “repassivation” behaviour of the steels at freshly ground surfaces with an electrochemical technique. The corrosion current measured with time was used to calculate the cracking rates of a compact tension specimen.

A correlation was found between chemical composition, corrosion resistance to SICC and experiences under practical conditions. The results of early‐published papers on boiler corrosion (testing in FeCl₂ solutions), erosion corrosion (testing in wet steam at 20 bar), nitrate stress corrosion cracking (testing in NH₄NO₃ solutions) and SICC together with those originating from in‐service failures, were compiled into a reference database. This paper is a compilation of this work too.

The database and formulas presented make clear there is often a direct correlation between chemical composition of ordinary C‐steel and mentioned types of corrosion failures. The paper is of importance to designers, failure analysts and researchers.

The advantages of reclaiming as much condensate as possible in any steam‐generating system are manifest. The return of hot water to the boiler results in a considerable reduction in fuel and water consumption. In addition, a low make‐up will give rise to a lower rate of corrosion attack due to carbon dioxide generated from dissolved bicarbonates. However, such a procedure greatly increases the length of piping and number of fittings which are exposed to attack. The corrosion of steam and condensate return lines, and also of steam‐using equipment, can become a major problem. Perforation of steam jackets, steam coils, pipes and fittings; choking of steam traps with corrosion products; leaking valves and joints are serious enough in themselves. The cost of replacing the corroded equipment is often considerable and excessive damage may be caused by the ingress of steam or water to the product being manufactured. In addition, a very high labour cost is often involved. Repairs to damaged plant must usually take place at weekends and during holiday time, when overtime rates are paid.