Turbines Expanders

Equations (2.31) and (2.32) are appropriate energy relations. However, the potential-energy term can be omitted, because there is little change in elevation. Moreover, in any properly designed turbine, heat transfer is negligible and the inlet and exit pipes are sized to make fluid velocities roughly equal. Equations (2.31) and (2.32) therefore reduce to  

Normally, the inlet conditions Fi and Pi and the discharge pressure P2 are known. Thus in Eq. (7.14) only Hi is known, and both H2 and remain as unknowns. The energy equation 

The sliaft work Wj (isentropic) is the maximum tliat can be obtained from an adiabatic hirbine with given inlet conditions and given discharge pressure. Actual turbines produce less work, because the actual expansion process is irreversible. We therefore define a turbine 

M wife ii. i lial filial stite is also ttWd.ijs qu aJity s ionnd from the r- i 

Example 7.6 is solved with data from the steam tables. When a comparable set of tables is not available for the working fluid, the generalized correlations of Sec. 6.7 may be used in conjunction with Eqs. (6.84) and (6.85), as illustrated in the following example. 

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Power is generated by the pressurized gas expanding through an 11,000 rpm single-stage, radial-inflow turbine expander, which drives a synchronous generator. Exhaust gas from the expander is liquified by air-cooled condensers and is pumped back to the heat exchangers to repeat the cycle. 

The Brayton cycle in its ideal form consists of two isobaric processes and two isentropic processes. The two isobaric processes consist of the combustor system of the gas turbine and the gas side of the HRSG. The two isentropic processes represent the compression (Compressor) and the expansion (Turbine Expander) processes in the gas turbine. Figure 2-1 shows the Ideal Brayton Cycle. 

The optimum pressure ratio for maximum output work for a turbine taking into aeeount the effieieneies of the eompressor and the turbine expander seetion ean be expressed by the following relationship ... 

The calculation of the turbine expander module depends whether or not this is a single shaft gas turbine or a multiple shaft gas turbine. In aero-derivative turbines, there are usually two or more shafts. In the latest aero-derivative turbines, there are usually two compressor sections, the LP compressor section, and the HP compressor section. This means that the turbine has three shafts the third shaft is the power shaft. The turbines that drive the compressor section are known as the gasifier turbines, and the turbine, which drives the generator, is the power turbine. The gasifier turbine produces the work to drive the compressor. 

The turbine firing temperature, whieh affeets the life, power output, as well as the overall thermal effieieney of the turbine, must be ealeulated very aeeurately. To ensure the aeeuraey of this ealeulation, the turbine firing temperature is eomputed using two teehniques. These teehniques are based firstly on the fuel heat input and seeondly on the turbine heat balanee. Turbine expander effieieneies are eomputed and deterioration noted. 

Steam turbines, which generate more than 80 percent of the world s electric power, differ from steam engines m that steam drives blades and not pistons. Steam turbines expand pressurized steam through nozzles that accelerate the steam at the expense of heat energy and pressure. Work is created by transferring a portion of steam velocity to blades, buckets, or nozzles affixed to a rotor to move at high speeds. Steam turbines are relatively compact in relation to steam... 

The aircraft gas turbine engine, developed more than sixty years ago, uses the principle of jet reaction and the turbine engine. The engine consists of three major elements a compressor and a turbine expander, which are connected by a common shaft and a combustor, located between the compressor and the turbine expander. The useful work of the engine is the difference between that produced by the turbine and that required by the compressor. For the simple cycle system shown in Figure 1, about two-thirds of all the power produced by the turbine is used to drive the compressor. 

Advanced two- and three-dimensional computer analysis methods are used today in the analyses of all critical components to verify aerodynamic, heat transfer, and mechanical performance. Additionally, the reduction of leakage paths in the compressor, as well as in the gas turbine expander, results in further plant efficiency improvements. At the compressor inlet, an advanced inlet flow design improves efficiency by reducing pressure loss. Rotor air cooler heat utilization and adt anccd blade and vane cooling arc also used. 

Expander inlet temperature. The power produced by the turbine (expander) is proportional to the absolute temperature of the inlet gases. An increase in the expander inlet temperature increases the power output and efficiency... 

The combusted air and fuel stream (stream 12) from the high-pressure fuel cell are expanded (stream 13) in a turbine expander. The work of this turbine is used to drive the low- and high-pressure air compressors. The reduced pressure exhaust stream (stream 13) is utilized as the low-pressure fuel cell oxidant stream. Although vitiated, it still has 15% oxygen. The low-pressure TSOFC operates at 0.62 volts per cell, and fuel and air utilizations of 78 and 21.9%, respectively. The spent air and fuel effluents are combusted and sent (stream 14) to the low-pressure power turbine. The turbine generator produces approximately 1.4 MW AC. The low-pressure exhaust (stream 15) still has a temperature of 649°C (1200°F) and is utilized to... 

First, it is instructive to examine the performance of a recuperated system that has only one compressor (i.e., remove the IC and C2 from Figure 8.2) and compare this to a simple cycle GT (i.e., also remove the recuperator from the diagram). Consider an isentropic compressor efficiency of 85%, isentropic turbine expander efficiency of 90%, recuperator effectiveness of 88% and no pressure losses. A fixed turbine inlet temperature of 1200 K will be assumed for various pressure ratios. This value is based on an assumed 1000 K SOFC inlet temperature, and a 200 K temperature rise from the SOFC inlet to the turbine inlet. The 200 K temperature increase from the cathode inlet to the turbine inlet is reasonable to assume given a cathode temperature difference across the cell of 150 K, and another 50 K temperature increase from anode exhaust combustion. Thus, 1200 K will be used as a base case for the turbine inlet temperature, and for sensitivity, values of 1100 and 1300 K will also be analyzed. 

In order to get the real mass flow from the map, multiply by delta and divide by the square root of theta. The pressure and temperature condition immediately before the turbomachineiy is used, not the ambient measurement. For instance, at the turbine expander, the inlet temperature and pressure will be quite elevated and will change dramatically with a change in some process condition such as combustor firing rate therefore, the look-up value on the map will change. 

A steady-flow adiabatic turbine (expander) accepts gas at conditions J], Pj, and discharges at conditions Ti, P2. Assuming ideal gases, detemiine (per mole of gas) W, W ideait W iost, and Sq for one of tlie following cases. Take X = 300 K. 

Tests on an adiabatic gas turbine (expander)yield values for inlet conditions (Ti, P ) and outlet conditions (72, P2)- Assuming ideal gases with constant heat capacities, determine the turbine efficiency for one of the following ... 

The efficiency of a particular series of adiabatic gas turbines (expanders) correlates with power output according to the empirical expression ... 

Turbines (Expanders) High-velocity streams from nozzles impinging on blades attached to a rotating shaft form a turbine (or expander) through which vapor or gas flows in a steady-state expansion process which converts internal energy of a high-pressure stream into shaft work. The motive force may be provided by steam (turbine) or by a high-pressure gas (expander). 

Liquid NH, + liquid N, Turbine expander Uquid NH, + liquid N,... 

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