Shinya Marushima

Design Study of a Humidification Tower for the Advanced Humid Air Turbine System

The advanced humid air turbine (AHAT) system, which can be equipped with a heavy-duty, single-shaft gas turbine, aims at high efficiency equal to that of the HAT system. Instead of an intercooler, a WAC (water atomization cooling) system is used to reduce compressor work. The characteristics of a humidification tower (a saturator), which is used as a humidifier for the AHAT system, were studied. The required packing height and the exit water temperature from the humidification tower were analyzed for five virtual gas turbine systems with different capacities (1, 3.2, 10, 32, and 100 MW) and pressure ratios (π=8, 12, 16, 20, and 24). Thermal efficiency of the system was compared with that of a simple cycle and a recuperative cycle with and without the WAC system. When the packing height of the humidification tower was changed, the required size varied for the three heat exchangers around the humidification tower (a recuperator, an economizer and an air cooler). The packing height with which the sum total of the size of the packing and these heat exchangers became a minimum was 1 m for the lowest pressure ratio case, and 6 m for the highest pressure ratio case.

Conceptual Design of the Cooling System for 1700°C-Class, Hydrogen-Fueled Combustion Gas Turbines

The effects of three types of cooling systems on the calculated operating performances of a hydrogen-fueled thermal power plant with a 1,700°C-class gas turbine were studied with the goal of attaining a thermal efficiency of greater than 60 percent. The combination of a closed-circuit water cooling system for the nozzle blades and a steam cooling system for the rotor blades was found to be the most efficient, since it eliminated the penalties of a conventional open-circuit cooling system which ejects coolant into the main hot gas stream. Based on the results, the water cooled, first-stage nozzle blade and the steam cooled first-stage rotor blade were designed. The former features array of circular cooling holes close to the surface and uses a copper alloy taking advantage of recent coating technologies such as thermal barrier coatings (TBCs) and metal coatings to decrease the temperature and protect the blade core material. The later has cooling by serpentine cooling passages with V-shaped staggered turbulence promoter ribs which intensify the internal cooling.

Test Results From the Advanced Humid Air Turbine System Pilot Plant: Part 2—Humidification, Water Recovery and Water Quality

The AHAT (advanced humid air turbine) system has been studied to improve thermal efficiency of gas turbine power generation. This is an original gas turbine power generation system which substitutes the WAC (water atomization cooling) system for the intercooler system of the HAT cycle. A pilot plant was built to verify feasibility of the AHAT system, which is composed of a gas turbine, a humidification tower, a recuperator and a water recovery system. Firstly, characteristics of the humidification tower were examined. The experimental results of the humidification rate agreed with the calculation results within a deviation of 1%. Humidification increased the heat recovery, and the electrical efficiency exceeded 40%. Secondly, characteristics of the spray-type water recovery system were examined. 95% of water consumed by the humidification tower was recovered, and a significant reduction of the make-up water for the HAT cycle was confirmed. Thirdly, concentrations of impurities within the circulating water of the AHAT system were measured when the recovered water was recycled without any purification process.Copyright

Development of Elemental Technologies for Advanced Humid Air Turbine System

The Advanced Humid Air Turbine (AHAT) system improves the thermal efficiency of gas turbine power generation by using a humidifier, a Water Atomization Cooling (WAC) system, and a heat recovery system, thus eliminating the need for an extremely high firing temperature and pressure ratio. The following elemental technologies have been developed to realize the AHAT system: (1) a broad working range and high-efficiency compressor that utilizes the WAC system to reduce compression work, (2) turbine blade cooling techniques that can withstand high heat flux due to high-humidity working gas, and (3) a combustor that achieves both low NOx emissions and a stable flame condition with high-humidity air. A gas turbine equipped with a two-stage radial compressor (with a pressure ratio of 8), two-stage axial turbine, and a reverse-flow type of single-can combustor has been developed based on the elemental technologies described above. A pilot plant that consists of a gas turbine generator, recuperator, humidification tower, water recovery system, WAC system, economizer, and other components is planned to be constructed, with testing slated to begin in October 2006 to validate the performance and reliability of the AHAT system. The expected performance is as follows: thermal efficiency of 43% (LHV), output of 3.6 MW, and NOx emissions of less than 10 ppm at 15% O2. This paper introduces the elemental technologies and the pilot plant to be built for the AHAT system.© 2006 ASME

Test Results From the Advanced Humid Air Turbine System Pilot Plant: Part 1—Overall Performance

The AHAT (advanced humid air turbine) system is based on a recuperated cycle using high-humidity air. This system improves thermal efficiency by using the high-humidity air as working gas. After many studies and elemental tests, a 4MW-class pilot plant was planned and built in order to verify feasibility of the AHAT system from the viewpoints of heat cycle characteristic and engineering. This plant consists of a gas turbine, a recuperator, a humidification tower, a water recovery system, an economizer, and other components. The gas turbine consists of a two-stage centrifugal compressor (pressure ratio of 8), a reverse-flow type single-can combustor, and a two-stage axial-flow turbine. In overall performance tests, the plant thermal efficiency exceeded 40%LHV.Copyright

An Experimental and Analytical Study on the Advanced Humid Air Turbine System

The Advanced Humid Air Turbine (AHAT) is a regenerative cycle using high-humidity air. This system improves the gas turbine thermal efficiency by using high-humidity air without needing high firing temperature and pressure ratio. It is estimated AHAT cycle thermal efficiency exceeds that of combined cycle if it is designed by the optimum conditions, and the efficiency difference grows especially by the small and medium-size gas turbine. To verify the system concept and cycle performance of AHAT system, AHAT verification plant construction began in April 2005 and completed in September 2006. The plant that consists of a gas turbine with a two-stage radial compressor (pressure ratio of 8), a two-stage axial turbine, a reverse-flow type of single-can combustor, a recuperator, a humidification tower, a water recovery tower, an economizer, and other components. It is planned to validate performance and reliability of the AHAT system. Expected performance is: rated output 3.6 MW, efficiency 43% (LHV), and NOx emissions less than 10 ppm at 16% O2. This paper describes the system verification plant constructed, a news flash of integrated test results, and so on.

Conceptual Design of the Cooling System for 1700°C-Class Hydrogen-Fueled Combustion Gas Turbines

The effects of three types of cooling systems on the calculated operating performances of a hydrogen-fueled thermal power plant with a 1,700°C-class gas turbine were studied with the goal of attaining a thermal efficiency of greater than 60%. The combination of a closed-circuit water cooling system for the nozzle blades and a steam cooling system for the rotor blades was found to be the most efficient, since it eliminated the penalties of a conventional open-circuit cooling system which ejects coolant into the main hot gas stream.Based on the results, the water cooled first-stage nozzle blade and the steam cooled first-stage rotor blade were designed. The former features array of circular cooling holes close to the surface and uses a copper alloy taking advantage of recent coating technologies such as thermal barrier coatings (TBCs) and metal coatings to decrease the temperature and protect the blade core material. The later has cooling by serpentine cooling passages with V-shaped staggered turbulence promoter ribs which intensify the internal cooling.Copyright

Improvement of Heat Transfer Performance of Turbulence Promoter Ribs

Numerical and experimental approaches were taken to improve the heat transfer performance of V-shaped staggered (VSG) ribs. At first, a numerical method using Large Eddy Simulations (LES) was employed to determine the effect of VSG rib-induced flow on the local heat transfer coefficient distributions. The results revealed that the secondary flows generated by the rib configuration carry cold coolant air from the passage core region to the rib-roughened wall, thus enhancing heat transfer. Conversely, behind each rib there is a recirculation zone that does not contribute to enhanced heat transfer. Based on said results, six types of the advanced V-shaped staggered (AVSG) rib configurations were proposed. The test apparatus employing a comparative method was used to measure the total heat transfer coefficient and pressure loss coefficient of the VSG and AVSG ribs. It was concluded that thermal performance of the most effective type was 25% higher than that of VSG.Copyright

A Method for Analyzing Static Performance at Part Load in a Heat Recovery Steam Generator.

When designing a combined cycle plant, it is essential to estimate performance of the heat recovery steam generator not only at full load but also part load. The method for analyzing the part load performance presented in this paper is based on a full load heat mass balance of the combined cycle plant. Steam turbine inlet pressure, which is the base point of pressure balance, is calculated from a relationship between the pressure ratio and corrected mass flow. Pressure losses of pipes and heat exchangers are corrected by their full load pressure losses. Temperature balance is determined by correcting superheater outlet temperature, pinch point and approach point under the constraints that the area of each heat exchanger is unchangeable. This method is applied to a reheat and triple pressure heat recovery steam generator.

A Method for Analyzing Sensitivity of Recoverable Heat in a Heat Recovery Steam Generator.

We propose a method for analyzing the sensitivity of recoverable heat in a multi-pressure heat recovery steam generator. In order to calculate how much steam is supplied to the steam turbine, equations of heat balance are derived from the quantities of steam which are generated in the heat recovery steam generator and recoverable heat such as that of gas turbine exhaust or from other heat sources. A matrix which represents the relationship between the quantities of steam and the recoverable heat is obtained from the equations of heat balance. The performances of the bottomming cycle can be analyzed by comparing the elements of the matrix. This method is applied to bottomming cycles of a three-pressure heat recovery steam generator which have various types of recoverable heats.