Kuniyoshi Tsubouchi

Development of an Advanced Microturbine System Using Humid Air Turbine Cycle

A prototype machine for a next generation microturbine system applying a simple humid air turbine system (design target of electrical output: 150 kW, electrical efficiency: 35% LHV) was developed for its laboratory evaluation. A low NOx combustor which applied a lean-lean zone combustion concept and water lubricated bearings were developed for the prototype machine. Operation using two water lines for the humid air turbine (HAT) was proposed as an effective way to obtain rated electric output to ambient temperature of 40 deg C. Tests for the main components were done successfully. Motoring tests, full speed test with no load, 50% load and 70% load tests as preliminary tests for rated load tests were also carried out successfully. Low NOx emission of 7.6 ppm and high efficiency of 95.6% for the power conversion system were achieved in the partial load tests. At the first rated load test without HAT and Water atomizing inlet air cooling (WAC) that followed those partial load tests, 150.3 kW electric output with electrical efficiency of 32% was obtained.© 2004 ASME

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

150 kW Class Two-Stage Radial Inflow Condensing Steam Turbine System

A prototype machine for a 150 kW class two-stage radial inflow condensing steam turbine system has been constructed. This turbine system was proposed for use in the bottoming cycle for 2.4 MW class gas engine systems, increasing the total electrical efficiency of the system by more than 2%. The gross power output of the prototype machine on the generator end was 150kW, and the net power output on the grid end which includes electrical consumption of the auxiliaries was 135kW. Then, the total electrical efficiency of the system was increased from 41.6% to 43.9%. The two-stage inflow condensing turbine system was applied to increase output power under the supplied steam conditions from the exhaust heat of the gas engines. This is the first application of the two-stage condensing turbine system for radial inflow steam turbines. The blade profiles of both high- and low-pressure turbines were designed with the consideration that the thrust does not exceed 300 N at the rated rotational speed. Load tests were carried out to demonstrate the performance of the prototype machine and stable output of 150 kW on the generator end was obtained at the rated rotational speed of 51,000 rpm. Measurement results showed that adiabatic efficiency of the high-pressure turbine was less than the design value, and that of the low-pressure turbine was about 80% which was almost the same as the design value. Thrust acting on the generator rotor at the rated output power was lower than 300 N. Despite a lack of high-pressure turbine efficiency, total thermal efficiency was 10.5% and this value would be enough to improve the total thermal efficiency of a distributed power system combined with this turbine system.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.

A 150 kW Radial Inflow Steam Turbine System for the Bottoming Cycle of Reciprocating Engines

A design study for a 150 kW class radial inflow steam turbine system for the bottoming cycle in 2.4 MW class gas engine systems has been completed. The total electrical efficiency of the gas engine can be increased from 41.6% to 44.2%. A two-stage condensing turbine system is applied to increase output power under the supplied steam conditions from the exhaust heat of the gas engines. The pressure ratio of a high-pressure turbine is 3.5, and that of a low-pressure turbine is 4.6. The blade profiles of both turbines are also designed to make sure the thrust does not exceed 300 N at the rated rotational speed of 51,000 rpm. To simplify the rotor system and to reduce mechanical losses, a permanent magnet generator rotor is applied that is composed of turbine rotors in a common shaft supported by two water-lubricated bearings. The oil supply system is completely eliminated in the turbine system. Design specifications of the turbines are shown, as are operating pressure ratio ranges of upper and lower limits from the start to the rated rotational speed for a stable starting operation.Copyright

Numerical Simulation for Propagation of Pressure Waves in Railway Tunnels

When a high speed train, such as bullet train, passes through a tunnel, pressure fluctuations act on the body because of the propagation of pressure waves generated by the train entering a tunnel. In this report, a numerical analysis method for unsteady one-dimensional compressible flow, in which the method of characteristics is employed, is presented. A computer program using this method was used to investigate the propagation of pressure waves and pressure fluctuations. Calculations are performed with a train velocity of 300km/h. Results of pressure profiles in a tunnel, profiles of the rate of change of pressure, and pressure histories at front and rear sections of the train are presented.