Ensuring Compressor Efficiency

Combustors All gas turbine combustors perform the same function They increase the temperature of the high-pressure gas at constant pressure. The gas turbine combustor uses veiy little of its air (10 percent) in the combustion process. The rest of the air is used for cooling and mixing. The air from the compressor must be diffused before it enters the combustor. The velocity leaving the compressor is about 400-500 ft/sec (130-164 m/sec), and the velocity in the combustor must be maintained at about 10-30 ft/sec (3-10 iTi/sec). Even at these low velocities, care must be taken to avoid the flame to be carried downstream. To ensure this, a baffle creates an eddy region that stabi-hzes the flame and produces continuous ignition. The loss of pressure in a combustor is a major problem, since it affecls both the fuel consumption and power output. Total pressure loss is in the range of 2-8 percent this loss is the same as the decrease in compressor efficiency. 

Hie best overall efficiency of a turbine can be ensured by maintaining tile efficiency of the air compressor section. Conversely, allowing the air compressor efficiency to deteriorate will deteriorate the overall thermal efficiency of the turbine. Air compressor efficiency can be draslically reduced in a very short time when dirt, salt water mist, or similar air con-... 

In agreement with pervious parts, in order to achieve a proper adoption for engine, all performance points of engine which is equipped to turbocharger should be obtained. As mentioned above, performance points include constant speed lines and constant load which are overlapped on compressor curve. If engine performance condition be at safe region and upper level of compressor efficient curve, it ensures suitable adaptation of engine and compressor. 

The book Gas Turbine Performance by Walsh and Fletcher [10] has excellent treatment on turbomachineiy maps. An example of a compressor map is shown in Figure 8.10. This map fully defines the pressure-flow-efficiency-rotational speed relationship of the compressor. Employing the Beta-line or R-line method, maps can be digitized into tabular form as described by Walsh and Fletcher [10], The Betaline method is helpful to ensure numeric stability with such maps that would be otherwise problematic because of the near zero and infinite slope at the ends of the constant speed lines. Note that the compressor model can either be a flow element or a pressure element. That is, from speed and pressure it is possible to obtain flow and efficiency from the map, or from speed and flow it is possible to obtain pressure and efficiency from the map. The choice depends on what is more convenient, that is, what type of elements are modeled upstream and downstream. 

The ammonia synthesis reactor operates at a pressure of 8.0 MPa using ICl s cobalt-promoted catkyst. The gas enters at 225 C and leaves at 380 C 131]. The low-pressure synthesis loop ensures that high machine efficiency is sustained for the two-stage centrifugal compressor, despite the small size of the plant. Electric drives... 

Recent improvements have been made to the RELAP5-3D computer code by the Idaho National Laboratory (INL) to facilitate modehng the closed-loop Brayton system. A compressor component is now available which can represent the expected performance maps of the compressor (Fisher et al., 2005). Also, the turbine component has been expanded to accept variable inlet irrecoverable loss factor and efficiency values to ensure the turbine performance follows the desired performance maps. This code change to the turbine component was completed internally at Bechtel Bettis, Inc. The tuibine component changes have been provided to the INL for incorporation into a future release of RELAP5-3D. 

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