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The arrangement shown in Fig. 16.36 has two shafts with two turbines in series. It gives advantage of independent shaft speeds. GAS TURBINE FUELS The various fuels used for gas turbines are as follows:

It is possible to use two turbines in parallel by using a single compressor and a single combustion chamber. The arrangement for such a system is shown in Fig. 16.34. For 1 kg of air through the compressor, a certain fraction x is required to pass through turbine I in order to drive the compressor. Then (1 − x)…

The operating variables for the performance of open cycle gas turbine are as follows: These variables affect the thermal efficiency and the work ratio of the gas turbine. 1 Effect of Pressure Ratio For the simple Brayton cycle, Thermal efficiency,  Work ratio,  The thermal efficiency for various values of γ and rp are given in Table 16.2. The variation of…

Similar to the case of 16.12.6, it can be shown that Example 16.1 Calculate the indicated mean effective pressure and efficiency of a Joule cycle if the temperature at the end of combustion is 2000 K and the temperature and pressure before compression are 350 K and 1 bar, respectively. The pressure ratio is 1.3…

The thermal efficiency of open cycle constant pressure gas turbine can be improved by the following methods: 1 Regeneration In this method, the heat of the exhaust gases is used to heat the air coming out from the compressor, thus reducing the mass of fuel supplied in the combustion chamber. A schematic diagram of such…

The open cycle constant pressure gas turbine plant is shown diagrammatically in Fig. 16.8. The fuel is burned with air coming out from the compressor into the combustion chamber. The products of combustion from the combustion chamber are passed through the turbine and developed the required power. Part of the power developed is used to run…

1 Maximum Pressure Ratio for Maximum Specific Work It is not possible to achieve isentropic compression and expansion in the actual Brayton cycle because of inevitable losses due to friction and turbulence in the compressor and turbine. Therefore, the temperature at the end of compression and expansion are higher than that in an ideal cycle…

1 Efficiency The Brayton cycle is shown on p-V and T-s diagrams in Fig. 16.4. During this cycle, air is drawn into the compressor at point 1 and then compressed isentropically along the process 1-2. Process 2-3 represents the burning of the oil at constant pressure p2. Process 3-4 is the isentropic expansion of the gases through the turbine. Process 4-1…

Constant pressure gas turbines are now used for generating electricity, driving locomotives and aeroplane propellers, producing the air stream for wind tunnels, and jet propulsion of air craft. In some types of aircraft, the exhaust gases from the main engines are used for driving a gas turbine which, in turn, drives the supercharger. Gas turbines…

The comparison of open and closed cycles gas turbines is given in Table 16.1.   Table 16.1 Comparison of open and closed cycles gas turbines