Brayton engine efficiency

On-site combined heat and power (CHP) which has existed for years, includes turbines, reciprocating engines and steam turbines. Gas turbines in the 500-kW to 250-MW produce electricity and heat using a thermodynamic cycle known as the Brayton cycle. They produce about 40,000-MW of the total CHP in the United States. The electric efficiency for units of less... 

An engine operates on the open Brayton cycle and has a compression ratio of 8. Air, at a mass flow rate of 0.1 kg/sec, enters the engine at 27°C and 100 kPa. The amount of heat addition is IMJ/kg. Determine the efficiency, compressor power input, turbine power output, back-work ratio, and net power of the cycle. Show the cycle on a T-s... 

An engine operates on the closed Brayton cycle (Fig 4.8) and has a compression ratio of 8. Helium enters the engine at 47°C and 200 kPa. The mass flow rate of helium is 1.2 kg/sec and the amount of heat addition is 1 MJ/kg. Determine the highest temperature of the cycle, the turbine power produced, the compressor power required, the back-work ratio, the rate of heat added, and the cycle efficiency. 

An engine operates on an actual reheat open Brayton cycle (Fig. 4.15a)). The air enters the compressor at 60°F and 14.7 psia, and exits at 120psia. The maximum cycle temperature (at the exit of the combustion chamber) allowed due to material limitation is 2000°F. The exit pressure of the high-pressure turbine is 50 psia. The air is reheated to 2000° F, and the mass flow rate of air is 1 Ibm/sec. The exit pressure of the low-pressure turbine is 14.7 psia. The compressor efficiency is 86% and the turbine efficiency is 89%. Determine the power required for the compressor, the power produced by the first turbine, the rate of heat added in the reheater, the power produced by the second turbine, the net power produced, back-work ratio, and the... 

An engine operates on the actual regenerative Brayton cycle (Fig. 4.18a). Air enters the engine at 60°F and 14.7 psia. The maximum cycle temperature and the maximum pressure are 2000°F and 120 psia. The compressor efficiency is 85% and the turbine efficiency is 89%. The mass flow rate of air is 1 Ibm/sec. Determine the power required for the... 

Hall, J.L., J.A. Barclay, Analyzing Magnetic Refrigeration Efficiency A Rotary AMR-Reverse Brayton Case Study , Advances in Cryogenic Engineering, V. 43B, pp. 1719-1728, 1998... 

The idealization of the gas-turbine engine (based on air, and called the Brayton cycle) is shown on a PF diagram in Fig. 8.12. Step AB is the reversible adiabatic compression of air from Pa (atmospheric pressure) to Pb- In step BC heat Qbcz replacing combustion, is added at constant pressure, raising the air temperature prior to the work-producing isentropic expansion of the air from pressure Pc to pressure Po (atmospheric pressure). Step DA is a constant-pressure cooling process that merely completes the cycle. The thermal efficiency of the cycle is ... 

In the area of heat engines, Brayton cycles are under study. The MARS (27) high temperature concept proposes an open cycle air-turbine. The STAR concepts (24, 25, 29) consider a supercritical CO2 Brayton cycle, which can theoretically reach conversion efficiencies of about 43% at core outlet temperatures of 500-530°C, traditional for sodium and lead-bismuth cooled reactors. Since the Brayton cycle rotating machinery is smaller and the component count is smaller than for the Rankine cycle, the targeted result would be higher conversion efficiency at lower capital cost as well as smaller required operating crew and skill level to achieve reduced operation and maintenance costs. 

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