Compressor

FIGURE 3 Components of a split-shaft gas turbine

FIGURE 4 Typical curve of power output versus shaft speed for a split-shaft gas turbine

In noting that h3 is directly proportional to temperature, one can appreciate why continuous emphasis is being placed on the development of materials and techniques that permit higher combustion temperatures and correspondingly higher turbine inlet temperatures.

Classifications In an open-cycle gas turbine, the inlet air mixes directly with the combustion products and is exhausted to the atmosphere after passing through the power turbine. The closed-cycle gas turbine uses a heat exchanger to transfer heat to the working fluid, which is continuously recirculated in a closed loop. A combined cycle uses the principles of both the open and closed cycles. In current practice, the combined cycle uses an open cycle to provide shaft work while the heat from the exhaust is partially recovered in a waste-heat boiler. The heat recovered then proceeds through a standard steam power cycle until heat is rejected to the most readily available low-temperature reservoir.

Of the above configurations, the open-cycle gas turbine is most extensively used today for driving centrifugal pumps. This is probably due to the important consideration of minimum capital investment for each power output.

Two distinct types of open-cycle gas turbines have evolved: the single-shaft and split-shaft versions. The single-shaft gas turbine was developed primarily for the electric power industry and uses a compressor and a power turbine integrated on a common shaft. As the unit is used continuously at a single rotational speed, the compressor and power turbine efficiency can be optimized.

The split-shaft gas turbine was developed primarily for mechanical drive applications where output power and speed might be expected to vary. Figure 3 illustrates such a turbine. A typical curve of power output versus shaft speed is illustrated in Figure 4.

Split-shaft gas turbines are available in conventional and aircraft-derivative versions. The conventional gas turbine evolved from steam turbine technology and is illustrated in

Figure 5. Figure 6 shows a modified jet engine used as a source of hot gas to a power turbine. Note that the jet engine combines the compression, combustion, and power turbine necessary to drive the compressor.

Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

Get My Free Ebook


Post a comment