Turbines computation

In RANS codes, the weak numerical coupling of the phases makes the EL method well suited for gas turbine computations, but RANS with the EE approach may also be found for example in simulations of fluidized beds [277 335] or chemical reactors [284 272 289], two examples of two-phase flows with a high load of particles. The experience gained in the development of RANS has led to the conclusions that both approaches are useful and they are both found today in most commercial codes. Moreover, coupling strategies between EE and EL methods within the same application are considered for certain cases. In the framework of LES of gas turbines, it is interesting to compare again EL with EE formulations. 

Is there a computer program that monitors the system and advises on what turbines to operate and how to minimise steam venting ... 

Fig. 11. Computer-simulated recirculating patterns in a mixing tank with full baffles (a) elevation view shows circulation patterns generated by turbine blades (b) plane view shows the effect of the baffle on the radial velocity vectors above the turbine blades.

Thrust-Bearing Power Loss The power consumed by various thrust bearing types is an important consideration in any system. Power losses must be accurately predicted so that turbine efficiency can be computed and the oil supply system properly designed. 

The primary cause of efficiency losses in an axial-flow turbine is the buildup of boundary layer on the blade and end walls. The losses associated with a boundary layer are viscous losses, mixing losses, and trailing edge losses. To calculate these losses, the growth of the boundary layer on a blade must be known so that the displacement thickness and momentum thickness can be computed. A typical distribution of the displacement and momentum thickness is shown in Figure 9-26. The profile loss from this type of bound-ary-layer build-up is due to a loss of stagnation pressure, which in turn is... 

With the advance of the turbine to idle speed, the turbine is ready to synchronize, and control is considered in synchronization. Both manual and automatic synchronizing are available locally. The unit is synchronized, and the main breaker closed. The speed reference will be switched to become a load reference. The speed/load reference will be automatically increased at a predetermined rate so that the fuel valve will be at the approximate position required for the desired load. For maintenance scheduling, the computer will count the number of normal starts and accumulate the number of hours at the various load levels. 

Since the reliability of gas turbines in the power industry has been lower than desired in recent years because of hot-corrosion problems, techniques have been developed to detect and control the parameters that cause these problems. By monitoring the water content and corrosive contaminant in the fuel line, any changes in fuel quality can be noted and corrective measures initiated. The concept here is that Na contaminants in the fuel are caused from external sources such as seawater thus, by monitoring water content, Na content is automatically being monitored. This on-line technique is adequate for lighter distillate fuels. For heavier fuels, a more complete analysis of the fuel should be carried out at least once a month using the batch-type system. The data should be input directly to the computer. The water and corrosion detecting systems also operate in conjunction with the batch analysis for the heavier fuels. 

Turbine flow meters. The principle of this flow meter is the computation of the revolutions of the turbine wheel in a given time frame. 

Loss computation, this enables the operator to ensure that the filters are clean and that no additional losses than necessary reduce the performance of the gas turbine. The following parameters are necessary to monitor the filter ... 

This section deals with the equations, and techniques used to compute and simulate the various performance and mechanical parameters for the gas turbine power plant. The goals have been to be able to operate the entire power plant at its maximum design efficiency, and at the maximum power that can be obtained by the turbine without degrading the hot section life. 

The turbine firing temperature should be computed by knowing the gas characteristics of the combustion gas. If these characteristics are known then one can use the combustion gas equations given in the ASME performance test codes 4.4 (1991) for gas turbine HRSG. Usually the gas constituents are not known so it is not a bad assumption to use the 400% theoretical air tables in the Keenan and Kaye gas tables. The following equations for... 

The turbine firing temperature based on the heat balance can be also computed and must be within about 2-6 °F (1-3 °C) of each other. The heat balance relationships as they apply to the gas turbine... 

Gonzalez, Fr., Boyce, Me. P., Solutions to Field Problems of a Gas Turbine-Axial Flow Chemical Process Compressor Train Based on Computer Simulation of the Process, Proceedings of the 28th Turbomachinery Symposium, Texas A M University, p. 77, 1999. 

In Section 3.4, we consider the open gas turbine cycle in which fuel is supplied in a combustion chamber and the working fiuids before and after combustion are assumed to be separate semi-perfect gases, each with Cp(T), c (T), but with R = [Cp T) — Cv( )l constant. Some analytical work is presented, but recently the major emphasis has been on computer solutions using gas property tables results of such computations are presented in Section 3.5. 

In practical open circuit gas turbine plants with combustion, real gas effects are present (in particular the changes in specific heats, and their ratio, with temperature), together with combustion and duct pressure losses. We now develop some modifications of the a/s analyses and their graphical presentations for such open gas turbine plants, with and without heat exchangers, as an introduction to more complex computational approaches. 

Essentially, the analytical approach outlined above for the open circuit gas turbine plants is that used in modem computer codes. However, gas properties, taken from tables such as those of Keenan and Kaye [6], may be stored as data and then used directly in a cycle calculation. Enthalpy changes are then determined directly, rather than by mean specific heats over temperature ranges (and the estimation of n and n ), as outlined above. 

The discussion of the performance of gas turbine plants given in this chapter has developed through four steps reversible a/s cycle analysis irreversible a/s cycle analysis open circuit gas turbine plant analysis with approximations to real gas effects and open circuit gas turbine plant computations with real gas properties. The important conclusions are as follows ... 

Lloyd s detailed computation for a steam/TCR cycle is. shown in Fig. 8.11. Here the main thermodynamic parameters have been specified pressure ratio 15, turbine entry... 

Ranade, V.V., 1997. An efficient computational model for simulating flow in stirred vessels a case of Rushton turbine. Chemical Engineering Science, 52, 4473-4484. 

Advanced two- and three-dimensional computer analysis methods are used today in the analyses of all critical components to verify aerodynamic, heat transfer, and mechanical performance. Additionally, the reduction of leakage paths in the compressor, as well as in the gas turbine expander, results in further plant efficiency improvements. At the compressor inlet, an advanced inlet flow design improves efficiency by reducing pressure loss. Rotor air cooler heat utilization and adt anccd blade and vane cooling arc also used. 

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