Shigeo Hatamiya

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.

Experiments on Convection Heat Transfer Along a Vertical Flat Plate Between Pools with Different Temperatures

This paper reports that to evaluate the heat removal capability of an external water wall-type containment vessel, which is a passive system for containment cooling, thermal-hydraulic behavior in the suppression and outer pools has been examined experimentally. The following results are obtained: A thermal stratification boundary, which separates the pools into an upper high-temperature region and a lower low-temperature region, is observed just below the vent outlet. The natural-convection heat transfer coefficients (HTCs) for the downward and upward flows that appear inside and outside the primary containment vessel wall are measured. The condensation HTCs in the presence of non-condensable gas, which affect heat transfer between the wet well and the outer pool, are measured along the long wall. The capability for decay heat removal in the external water wall-type containment vessel for a 600-MW (electric) plant is evaluated based on these results and is found to be large enough.

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

An Evaluation of Advanced Humid Air Turbine System With Water Recovery

The AHAT (Advanced HAT) system can be used for single shaft gas turbines without redesigning them and it gives a similar effect as intercooling by using suction air atomization. In this paper, two basic experiments with a spray nozzle, simplified humidifier and water recovery were carried out. A compact heat exchanger for humidified gas turbines could be realized by using the spray nozzle without significant pressure loss. In addition, a big effect was found in the efficiency improvement when water atomization into the compressor was combined with the regenerative cycle. The AHAT system had high efficiency, 5% higher compared with the mid-size combined cycle.Copyright

Inlet Air Cooling With Overspray Applied to a Two-Stage Centrifugal Compressor

A Water Atomization Cooling (WAC) system is a kind of inlet fogging technique with overspray, which reduces the compression work due to the intra-cooling effect of over-injected droplet evaporation. The WAC system has been successfully applied to mid- and large-sized gas turbines, but its application to small turbines is rare. Hitachi developed a 3.7 MW Advanced Humid Air Turbine (AHAT) plant as a national project from 2004 to 2006. The plant has a two-stage centrifugal compressor with a total-to-total pressure ratio of 8.3 without the WAC system. We compare theoretical and experimental evaporation behaviors of injected droplets into the compressor and their effect on the compressor characteristics, when the WAC system was applied to the AHAT plant.Copyright

Parallel channel effects under BWR LOCA conditions

Abstract Due to parallel channel effects, different flow patterns such as liquid down-flow and gas up-flow appear simultaneously in fuel bundles of a BWR core during postulated LOCAs. Applying the parallel channel effects to the fuel bundle, water drain tubes with a restricted bottom end have been developed in order to mitigate counter-current flow limiting and to increase the falling water flow rate at the upper tie plate. The upper tie plate with water drain tubes is an especially effective means of increasing the safety margin of a reactor with narrow gaps between fuel rods and high steam velocity at the upper tie plate. The characteristics of the water drain tubes have been experimentally investigated using a small-scaled steam-water system simulating a BWR core. Then, their effect on the fuel cladding temperature was evaluated using the LOCA analysis program SAFER.

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.