Tadaharu Kishibe

An Advanced Microturbine System with Water-Lubricated Bearings

A prototype of the next-generation, high-performance microturbine system was developed for laboratory evaluation. Its unique feature is its utilization of water. Water is the lubricant for the bearings in this first reported application of water-lubricated bearings in gas turbines. Bearing losses and limitations under usage conditions were found from component tests done on the bearings and load tests done on the prototype microturbine. The rotor system using the water-lubricated bearings achieved stable rotating conditions at a rated rotational speed of 51,000 rpm. An electrical output of 135 kW with an efficiency of more than 33% was obtained. Water was also utilized to improve electrical output and efficiency through water atomizing inlet air cooling (WAC) and a humid air turbine (HAT). The operation test results for the WAC and HAT revealed the WAC and HAT operations had significant effects on both electrical output and electrical efficiency.

Development of a 150kw Microturbine System Which Applies the Humid Air Turbine Cycle

A prototype machine for a next generation microturbine system incorporating a simplified humid air turbine cycle has been developed for laboratory evaluation. Design targets of electrical output were 150 kW and of electrical efficiency, 35% LHV. The main feature of this microturbine system was utilization of water for improved electrical output, as lubricant for bearings and as coolant for the cooling system of the generator and the power conversion system Design specifications without WAC (Water Atomizing inlet air Cooling) and HAT (Humid Air Turbine) were rated output of 129 kW and efficiency of 32.5% LHV. Performance tests without WAC and HAT were done successfully. Electrical output of 135 kW with an efficiency of more than 33% was obtained in the rated load test. Operation tests for WAC and HAT were carried out under the partial load condition as preliminary tests. Water flow rates of WAC were about 0.43 weight % of inlet air flow rate of the compressor and of HAT, about 2.0 weight %. Effects of WAC and HAT were promptly reflected on electrical output power. Electrical outputs were increased 6 kW by WAC and 11kW by HAT, and efficiencies were increased 1.0 pt % by WAC and 2.0 pt % by HAT. Results of WAC and HAT performance tests showed significant effects on the electrical efficiency with an increase of 3.0 point % and electrical output with an increase of 20% by supplying just 2.4 weight % water as the inlet air flow rate of the compressor.Copyright

Improvement in the Design of Helium Turbine for the HTGR-GT Power Plant

This paper describes the conceptual design of a 600MW HTGR-GT power plant which has been completed in the framework of the HTGR-GT feasibility study project. The project is assigned to JAERI by the Science and Technology Agency in Japan. The inlet and outlet gas temperatures in the reactor are 460°C and 850°C, respectively. Helium gas pressure is 6MPa. The gas turbine system type is intercooled recuperative direct cycle. Designs of helium turbine, LP and HP compressors and generator are presented. Efforts have been focussed on reducing their dimensions and weight in the preliminary design to facilitate the mechanical design of the rotor and also reduce the size of power conversion vessel. Rotor dynamics behavior and maintenance procedures of the horizontal single-shaft configuration adopted are explained.Copyright

Design Study of Helium Turbine for the 300MW HTGR-GT Power Plant

This paper describes the design of a 300MW HTGR-GT power plant which was completed in the framework of the HTGR-GT feasibility study project. The project is assigned to JAERI by the Science and Technology Agency of Japan. The inlet and outlet gas temperatures in the reactor are 550°C and 900°C, respectively. Helium gas pressure is 6MPa. The turbine system is a recuperative intercooled direct cycle one. Designs of helium turbine, LP and HP compressors and generator are presented, whose adiabatic efficiencies are 93.09, 89.92 and 90.25%, respectively. A horizontal single-shaft configuration was adopted whose rotor dynamics is given.Copyright

Starting Characteristic Analysis of a Radial Inflow Turbine for the Regenerative Brayton Cycle

Microturbines have been developed as compact gas turbines to be applied in the regenerative Brayton cycle. A typical microturbine is composed of a centrifugal compressor and a radial inflow turbine. As such, the microturbine has a starting characteristic peculiar to radial inflow turbines. An idling state known as the windage point for mass flow rate can be formed because of improper inlet flow conditions for turbine expansion flow. The present study looked at the relationships between the radius ratio of the radial inflow turbine to the centrifugal compressor and the starting characteristic and at the effects of turbine inlet flow conditions on the starting characteristic. Fundamental equations for the relationships between the radius ratio and the starting characteristic were obtained. Effectiveness of the equations was compared with experiment results obtained with a 150 kW class prototype microturbine.

Evaluation of Axial Compressor Characteristics Under Overspray Condition

An axial compressor was developed for an industrial gas turbine equipped with a water atomization cooling (WAC) system, which is a kind of inlet fogging technique with overspray. The compressor performance was evaluated using a 40MW-class test facility for the advanced humid air turbine system. A prediction method to estimate the effect of WAC was developed for the design of the compressor. The method was based on a streamline curvature (SLC) method implementing a droplet evaporation model. Four test runs with WAC have been conducted since February 2012. The maximum water mass flow rate was 1.2% of the inlet mass flow rate at the 4th test run, while the design value was 2.0%. The results showed that the WAC decreased the inlet and outlet temperatures compared with the DRY (no fogging) case. These decreases changed the matching point of the gas turbine, and increased the mass flow rate and the pressure ratio by 1.8% and 1.1%, respectively. Since prediction results agreed with the results of the test run qualitatively, the compressor performance improvement by WAC was confirmed both experimentally and analytically. The test run with the design water mass flow rate is going to be conducted in the near future.Copyright

Improving the Performance of a High Pressure Gas Turbine Stage Using a Profiled Endwall

A non-axisymmetric endwall contouring technology has been developed in highly loaded axial turbomachinery. This paper describes the computational and experimental evaluation of our contouring approach applied in an air turbine nozzle. The geometrical parameters and the flow conditions are consistent with a modern high pressure gas turbine. In the design of the non-axisymmetric endwall, our original design concept is applied in order to improve the aerodynamic performance. The concept, derived from the governing equation of compressible flow, is verified in comparison with the previous researches. Effectiveness of our endwall contouring technology is shown in detail through the results of a computational study for the secondary flow in the vicinity of the endwall. The flow is seen to be significantly different from that of the annular endwall. The numerical results showed that the contoured endwall controlled both generation of a horseshoe vortex near the leading edge and the growth of secondary flow in the blade passage. The effective control of the secondary flow ensures more uniform flow in the front and rear part of the passage than that in the case of the non-contoured endwall. The effect also influences the increment of Mach number in the turbine nozzle and significantly changes the distribution of the total pressure loss coefficient in the main flow region. We confirmed 35% loss reduction using an air turbine test rig. Our study demonstrates the potential of the developed non-axisymmetric endwall contouring technology for enhancing the aerodynamic performance of turbine nozzles.Copyright