Intercooled simple cycle

Thermodynamic Cycle Recuperated and Intercooled Recuperated and Intercooled Simple Cycle Simple Cycle... 

The thermal efficiency of an ideal simple cycle is decreased by the addition of an intercooler. Figure 2-7 shows the schematic of such a cycle. The ideal simple gas turbine cycle is 1-2-3-4-1, and the cycle with the intercooling added is -a-b-c-2- i-A-. Both cycles in their ideal form are reversible and can be simulated by a number of Carnot cycles. Thus, if the simple gas turbine cycle 1-2-3-4-1 is divided into a number of cycles like m-n-o-p-m,... 

All the Carnot cycles making up the simple gas turbine cycle have the same efficiency. Likewise, all of the Carnot cycles into which the cycle a-b-c-2-a might similarly be divided have a common value of efficiency lower than the Carnot cycles which comprise cycle 1-2-3-4-1. Thus, the addition of an intercooler, which adds a-b-c-2-a to the simple cycle, lowers the efficiency of the cycle. 

A simple cycle with intercooler can reduce total compressor work and improve net output work. Figure 2-7 shows the simple cycle with intercooling between compressors. The assumptions made in evaluating this... 

This cycle produces an increase of 30% in work output, but the overall efficiency is slightly decreased as seen in Figure 2-15. An intercooling regenerative cycle can increase the power output and the thermal efficiency. This combination provides an increase in efficiency of about 12% and an increase in power output of about 30%, as indicated in Figure 2-16. Maximum efficiency, however, occurs at lower pressure ratios, as compared with the simple or reheat cycles. 

To further understand the thermodynamic philosophy of the improvements on the EGT cycle we recall the cycle calculations of Chapter 3 for ordinary dry gas turbine cycles—including the simple cycle, the recuperated cycle and the intercooled and reheated cycles. 

From a simple cycle standpoint, the combination of intercooling with recuperation eliminates the problem of the reduced combustor inlet temperature associated with intercooled cycles. The simple cycle then gets the benefit of the reduced compressor work and, at all but high pressure ratios, actually has a higher burner inlet temperature than the corresponding nonintercooled, nonrecuperated cycle. This results in a dramatic increase in the simple cycle efficiency. 

Figure 8.3 plots the efficiency versus pressure ratio at three turbine inlet temperatures (1100, 1200 and 1300 K) for the recuperated case, without intercooling, and the simple cycle. Also plotted are the power curves that apply to both cycle configurations. 

Figure 8.4 compares the recuperated cycle with and without intercooling. Intercooling will reduce the overall compressor power since the average density is reduced. Since there is recuperation, the lower compressor outlet temperature should not hurt system efficiency (intercooling is not shown for the simple cycle since the... 

The calculated cycle efficiencies are shown in Fig.3. When a recuperater is used, the cycle efficiency increases at the lower side of the pressure ratio as the recuperater exchanging heat capacity increases and as the system pressure loss is reduced. As seen from the theoretical value (component efficiency 100%) of the recuperated cycle, this is because a raised pressure ratio would reduce the exhaust gas temperature resulting in the smaller heat recovery by the recuperater. The efficiency of the recuperated/intercooled cycle is above the theoretical efficiency of the simple cycle in a pressure ratio range below 3.5. Because the efficiency of the... 

If the compression cycle approaches the isothermal condition, pV = constant, as is the case when several stages with intercoolers are used, a simple approximation of the power is obtained from the following formula ... 

Therefore, if a simple gas turbine cycle is modified with the compression accomplished in two or more adiabatic processes with intercooling between them, the net work of the cycle is increased with no change in the turbine work. 

Similar calculations (Fig. 6.10) were made for intercooled cycles, without and with water injection, i.e. comparing the efficiency of the dry CICBTX cycle with an elementary recuperated water injection plant, now a simple version of the. so-called RWl plant (see Section 6.4.2.1). Again there is an increase in thermal efficiency with water injection, but it is not as great as for the simple EGT plant compared with the dry CBTX plant the optimum pressure ratio, about 8 for the dry intercooled plant, appears to change little with water injection. 

In the search for higher plant thermal efficiency, the simplicity of the two basic STIG and EGT cycles, as described by Frutschi and Plancherel, has to some extent been lost in the substantial modifications described above. But there have been other less complex proposals for water injection into the simple unrecuperated open cycle gas turbine one simply involves water injection at entry to the compressor, and is usually known as inlet fog boosting (IFB) the other involves the front part of an RWI cycle, i.e. water injection in an evaporative intercooler, usually in a high pressure ratio aero-derivative gas turbine plant. 

Consider a simple ideal Brayton cycle with fixed maximum temperature and fixed minimum temperature. What is the effect of intercooling the gas on the cycle network ... 

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