Figure 1-10. A cross section of an aeroderivative .as tur.ine en.ine.
1. Favorable installation cost. The equipment involved is of a size and weight that it can be packaged and tested as a complete unit withinthe manufacturer"s plant. Generally， the package will include either a generator or a driven pipeline compressor and all auxiliaries and control panels specified by the user. Immediate installation at the job site is facilitated by factory matching and debugging.
2. Adaptation to remote control. Users strive to reduce operating costs by automation of their systems.孔any new offshore and pipelineapplications， today are designed for remote unattended operation of the compression equipment. Jet gas turbine equipment lends itself to automaticcontrol， as auxiliary systems are notcomplex， water cooling is not required (cooling by oil-to-airexchanges)， and the starting device (gas expansion motor) requires little energy and is reliable. Safety devices and instrumentation adapt readily for pur-poses of remote control and monitoring the performance of the equipment.
3. Maintenance concept. The off-site maintenance plan fits in well with these systems where minimum operating personnel and unattended stations are the objectives. Technicians conduct minor running adjust-ments and perform instrument calibrations. 0therwise， the aeroder-ivative gas turbine runs without inspection until monitoring equipment indicates distress or sudden performance change. This plan calls for the removal of the gasifier section (the aero-engine) and sending it back to the factory for repair while another unit is installed. The power turbine does not usually have problems since its inlet temperature is much lower. Downtime due to the removal and repla-cement of the Gasifier turbine is about eight hours.
Industrial Type Gas Turbines
Industrial Type Gas Turbines are medium-range gas turbines and usuallyrated between 5-15孔W. These units are similar in design to the large heavy-duty gas turbines; their casing is thicker than the aeroderivative casing but thinner than the industrial gas turbines. They usually are split-shaft designs that are efficient in part load operations. Efficiency is achieved by letting the gasifier section (the section which produces the hot gas) operate at maximum efficiency while the power turbine operates over a great range of speeds. The compressor is usually a 10-16 stage subsonic axialcompressor， which produces a pressureratio from about 5:1-15:1.孔ost American designs use can-annular (about 5-10 combustor cans mountedin a circular ring) or annular-type combustors.孔ost European designs use
Figure 1-11. A medium size industrial .as tur.ine. (Courtesy Solar Tur.ines Incorporated.)
side combustors and have lower turbine inlet temperatures compared to their American counterparts. Figure 1-11 shows an Industrial Type Gas Turbine.
The gasifier turbine is usually a 2-3 stage axial turbine with an air-cooled first-stage nozzle and blade. The power turbine is usually a single-or two-stage axial-flow turbine. The medium-range turbines are used on offshore platforms and are finding increasing use in petrochemical plants. Thestraight simple-cycle turbine is low in efficiency， but by using regenerators to consumeexhaustgases， these efficiencies can be greatly improved. In process plants this exhaust gas is used to produce steam. The combined-cycle (air-steam) cogeneration plant has very high efficiencies and is the trend of the future.
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