Turbine pressure

FIG. 29-22 Three -arm lever/mechanism for extraction-turbine-pressure control. 

Combustor inlet temperature depends on engine pressure ratio, load and engine type, and whether or not the turbine is regenerative or nonregen-erative espeeially at the low-pressure ratios. The new industrial turbine pressure ratio s are between 17 1, and 35 1, whieh means that the eombustor inlet temperatures range from 850 °F (454°C) to 1200 °F (649 °C). The new aireraft engines have pressure ratios, whieh are in exeess of 40 1. 

The turbine pressure ratio, however, remains relatively eonstant. The baek-pressure on the turbine was measured at a relatively eonstant value of 30.25 inehes Hg abs (1.02 Bar). This value ereates about a 9-ineh H2O (228 mm H2O) baek-pressure on the turbine. The effieieney of the eompres-sor is based on the following equation ... 

Calculation of the specific work and the arbitrary overall efficiency may now be made parallel to the method used for the a/s cycle. The maximum and minimum temperatures are specified, together with compressor and turbine efficiencies. A compressor pressure ratio (r) is selected, and with the pressure loss coefficients specified, the corresponding turbine pressure ratio is obtained. With the compressor exit temperature T2 known and Tt, specified, the temperature change in combustion is also known, and the fuel-air ratio / may then be obtained. Approximate mean values of specific heats are then obtained from Fig. 3.12. Either they may be employed directly, or n and n may be obtained and used. 

Fig. 3.13 shows the overall efficiency for the [CBTJic, plant plotted against the i.sentropic temperature ratio for various maximum temperatures Tj (and 6= Ty/Ti, with T, = 27°C (3(X) K)). The following assumptions are also made polytropic efficiency, rjp = 0.9 for compressor and turbine pressure loss fraction in combustion 0.03 fuel (methane) and air supplied at 1 bar, 27°C (3(X) K). 

Newby et al. found that increasing the PO turbine pressure resulted in higher steam flow (for a given pinch point temperature difference in the HRSG), increased PO turbine power and overall plant efficiency. However, at the highest pressure of 100 bar attempts to increase the steam flow further resulted in incomplete combustion in the main combustor and the overall thermal efficiency did not increase substantially at this pressure level. 

The integration of the turbine pressure regulator and control system with the reactor water recirculation flow control system permits automated... 

The plant in Figure A.4 can be dealt with in exactly the same way. The reformer and the two fuel cells would be elevated to IT/SOFC conditions, as in Figure A.6. All surplus fuel, heavy hydrocarbons and unoxidised fuel from the three plant sections, together with three hot exhausts, would be swallowed by a gas turbine combustion chamber as above. That would yield a controllable plant, subject to availability of semi-permeable membranes and of isothermal concentration cells, appropriate to IT/SOFC temperatures and gas turbine pressure. 

Gas turbine pressure ratio Gas turbine inlet temperature Turbine polytropic efficiency Compressor polytropic efficiency Recuperator effectiveness... 

The gas volumes in the body of the turbine are very small, so that the establishment of flow in the turbine is very fast, with a response time measured in tenths of a second. Since these time constants are an order of magnitude less than the rotor time constant associated with turbine speed, it is permissible to treat the equations of fluid flow as algebraic, simultaneous equations. This simplification receives even greater justification when the model of the turbine and the machine it drives are interfaced with a model of the rest of the process plant, which will be invariably much slower still. It is only when the turbine is being considered in detail on its own, for example in designing a speed-control system, that some of the larger turbine pressure constants, such as those associated with the turbine inlet manifolds, will need to be considered. 

The effects of A Pi, AP23 and AP4 can be found by modifying their corresponding pressure ratios, Vpc for the compressor and Vpt for the turbine, and using the binomial theorem to simplify the results. AP23 and AP4 apply to the turbine pressure ratio. 

Steam Turbine (Pressure Eubricated) 202.20—Reciprocating Pump... 

Extent of reaction specified Two-phase, chemical equilibrium Multiphase, chemical equilibrium Continuous-stirred tank reactor Plug-flow tubular reactor Pump or hydraulic turbine Compressor or turbine Pressure drop in a pipe Stream multiplier Stream duplicator... 

In the fuel cell/turbine hybrid power plant the fuel cell does not need to operate at the turbine pressure, instead it operates at the preferred ambient pressure and its independent of gas turbine cycle pressure ratio. The system works efficiently with a wide range of turbine compression ratio. This allows taking a system developed for integration at the multi-MW... 

The BWR operates at constant pressure and maintains constant steam pressure similar to most fossil boilers. The integration of the turbine pressure regulator and control system in conjunction with the reactor water recirculation flow control system permits automated changes in steam flow to accommodate varying load demands on the turbine. Power changes of up to 25% of rated power can be accomplished automatically by recirculation... 

The turbine generator plant and systems are similar to the conventional islands of standard reactors. In spite of the low inlet turbine pressure, improvements in the EPR turbine design [V-11] lead to a SCOR efficiency of 31.5%. 

Typical pressure ratios used were 1.5 to 3.0 lately, modern turbochargers have used pressure ratios of 3.2 to 3.5 and higher. The turbine pressure ratio is somewhat smaller than the compressor pressure ratio because of the pressure drop in the engine. 

In Case 3, an adequate heat exchanger can increase efficiency by recovering part of the heat from the gas turbine outlet This solution increases efficiency to 66% and decreases the gas turbine pressure ratio to 8.2. TIT is still very high at... 

Piping and component pressure drops also impact the converter and system efficiencies. The turbine pressure ratio is set by the pressure rise across the compressor minus the pressure losses in the components and piping. The larger the pressure drop within the system, the smaller the turbine pressure ratio. Decreasing the turbine pressure ratio decreases the turbine temperature ratio and therefore the turbine temperature drop. This decreases the amount of useful work extracted from the fluid and results in a less efficient system. 

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