Steam System Design Considerations for Three Pressure Reheat Cycles With Cascade Bypass System

2002 ◽  
Author(s):  
Brandon Greer ◽  
Kurt Schnaithmann ◽  
Stefan Klatt
Keyword(s):  
High Pressure ◽  
System Design ◽  
Steam Turbine ◽  
Plant Operation ◽  
Design Considerations ◽  
System Pressure ◽  
Pressure Steam ◽  
Reheat Steam ◽  
Steam System ◽  
Turbine Exhaust

This paper discusses various issues that should be considered when designing the steam system for a typical three pressure reheat cycle, which is used at many of today’s combined cycled plants. A cascade bypass arrangement in the steam system is commonly used to ensure steam flow is available to the reheat section of the HRSG during startup. For the purposes of this paper, a cascade bypass system will be defined as high pressure steam being bypassed to the cold reheat steam and hot reheat steam being bypassed to the condenser. This arrangement can lead to conflicts between plant operation needs and the steam turbine desire to reduce the HP turbine backpressure as much as possible during startup. Plant operation needs that may dictate keeping the reheat system pressure high include export steam minimum pressure guarantees to customers, cycling operation which forces the plant to restart when equipment is still hot, and hot reheat steam bypass or condenser limitations. The HP turbine and cold reheat steam piping can have temperature limitations which may necessitate keeping the HP turbine exhaust pressure as low as possible during startup.

scholarly journals Application of an Industrial Gas Turbine for Cogeneration and Process Services

1995 ◽  
Author(s):  
Gary A. Ehlers
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Waste Heat ◽  
Exhaust Gas ◽  
Electric Generator ◽  
Pressure Steam ◽  
Industrial Gas Turbine ◽  
Steam System

The gas turbine is not limited to single service applications such as power generation or mechanical drive service. An application has been developed recently to use an industrial gas turbine to drive an electric generator for power while at the same time contributing to the heat balance of a refinery unit. Specifically, a G. E. Frame 5 gas turbine installed with a hydrogen reformer furnace can significantly reduce the overall heat input required by capturing the waste heat in the exhaust gas to preheat the feed to the furnace and to generate high pressure steam for the owner’s refinery steam system. The gas turbine selected for the projects described in this paper is the G.E. Frame 5, model “R” (5271 RA). The model “R” was originally described as a “single shaft mechanical drive” turbine but easily adapted to generator drive. The design is some 30 years old as it was developed in the 1960’s. The term “single shaft mechanical drive” is somewhat strange to us in the process industries as we’re more accustomed to mechanical drive gas turbines designed with two shafts for speed control purposes. Many of the design / construction features of this model make it ideally suited for this application. The higher cost of fuels, and electrical power contribute significantly to making the economics attractive. First of all the heat of the turbine exhaust gas will reduce the fuel required for firing to heat the feed to the furnace. The steam generated in the heat recovery section then contributes to generating power in the steam side in the steam turbine. The results are fuel savings and electric power purchase savings. The steam turbine portion of the cycle is designed to vary with the owner’s steam system and balance. For that reason the steam turbine includes a high pressure inlet, medium pressure steam chest for extraction, a low pressure steam chest designed for induction or extraction and a surface condenser to condense the steam passed through. Fuel flexibility is a major consideration of the unit design. Natural gas or methane rich gas is a base fuel that the gas turbine will fire most of the time. Alternate fuels however, such as propane or butane are commonly available in a refinery and could be fired in the gas turbine as currently configured.

Using CFD to Enhance the Preliminary Design of High-Pressure Steam Turbines

2013 ◽  
Author(s):  
Juri Bellucci ◽  
Federica Sazzini ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Design Tool ◽  
Tip Clearance ◽  
Large Set ◽  
Preliminary Design ◽  
Steam Turbines ◽  
High Pressure Steam ◽  
Wide Range ◽  
Pressure Steam

This paper focuses on the use of the CFD for improving a steam turbine preliminary design tool. Three-dimensional RANS analyses were carried out in order to independently investigate the effects of profile, secondary flow and tip clearance losses, on the efficiency of two high-pressure steam turbine stages. The parametric study included geometrical features such as stagger angle, aspect ratio and radius ratio, and was conducted for a wide range of flow coefficients to cover the whole operating envelope. The results are reported in terms of stage performance curves, enthalpy loss coefficients and span-wise distribution of the blade-to-blade exit angles. A detailed discussion of these results is provided in order to highlight the different aerodynamic behavior of the two geometries. Once the analysis was concluded, the tuning of a preliminary steam turbine design tool was carried out, based on a correlative approach. Due to the lack of a large set of experimental data, the information obtained from the post-processing of the CFD computations were applied to update the current correlations, in order to improve the accuracy of the efficiency evaluation for both stages. Finally, the predictions of the tuned preliminary design tool were compared with the results of the CFD computations, in terms of stage efficiency, in a broad range of flow coefficients and in different real machine layouts.

CFD Investigation on the Rotordynamic Characteristics of Shroud Leakage Flow in High Pressure Steam Turbine

2013 ◽  
Author(s):  
Noriyo Nishijima ◽  
Akira Endo ◽  
Kazuyuki Yamaguchi
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Mass Flow ◽  
Guide Vane ◽  
Flow Distribution ◽  
Labyrinth Seal ◽  
High Pressure Steam ◽  
Cfd Models ◽  
Pressure Steam ◽  
The Difference

We conducted a computational fluid dynamics (CFD) study to investigate the rotordynamic characteristics of the shroud labyrinth seal of a high-pressure steam turbine. Four different CFD models were constructed to investigate the appropriate modeling approach for evaluating the seal force of an actual steam turbine because shroud seals are generally short with fewer fins and the effect of surrounding flow field is thought to be large. The four models are a full model consisting of a 1-stage stator/rotor cascade and a labyrinth seal over the rotor shroud, a guide-vane model to simulate the condition similar to seal element experiments, and two other simplified models. The calculated stiffness coefficients of the four models did not agree and fell into two groups. Through careful investigations of flow fields, it was found that the difference could be explained by the circumferential mass flow distribution at the seal inlet and the mass flow bias rate is an important factor in evaluating the seal force of a turbine shroud. The results also indicate that the rotordynamic characteristics obtained from seal element experiments may differ from those of actual turbines, especially in short seals.

Optimization of a High-Pressure Steam Turbine Stage for a Wide Flow Coefficient Range

2012 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Lorenzo Arcangeli ◽  
Nicola Maceli ◽  
...  
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Low Flow ◽  
Turbine Stage ◽  
Aerodynamic Optimization ◽  
High Pressure Steam ◽  
Wide Range ◽  
Pressure Steam

In this paper a multi-objective, aerodynamic optimization of a high-pressure steam turbine stage is presented. The overall optimization strategy relies on a neural-network-based approach, aimed at maximizing the stage’s efficiency, while at the same time increasing the stage loading. The stage under investigation is composed of prismatic blades, usually employed in a repeating stage environment and in a wide range of operating conditions. For this reason, two different optimizations are carried out, at high and low flow coefficients. The optimized geometries are chosen taking into account aerodynamic constraints, such as limitation of the pressure recovery in the uncovered part of the suction side, as well as mechanical constraints, such as root tensile stress and dynamic behavior. As a result, an optimum airfoil is selected and its performance are characterized over the whole range of operating conditions. Parallel to the numerical activity, both optimized and original geometries are tested in a linear cascade, and experimental results are available for comparison purposes in terms of loading distributions and loss coefficients. Comparisons between measurements and calculations are presented and discussed for a number of incidence angles and expansion ratios.

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