Norihiko Iki

Micro Gas Turbine Firing Kerosene and Ammonia

A demonstration test with the aim to show the potential of ammonia-fired power plant is planned using a micro gas turbine. 50kW class turbine system firing kerosene is selected as a base model. A standard combustor is replaced by a prototype combustor which enables a bi fuel supply of kerosene and ammonia gas. Diffusion combustion is employed in the prototype combustor due to its flame stability. Demonstration test of co-firing of kerosene and ammonia gas was achieved to check the functionality of the each component of the micro gas turbine. The gas turbine started firing kerosene and increased its electric power output. After achievement of stable power output, ammonia gas was started to be supplied and its flow rate increased gradually. 21kW power generation was achieved with 30% decrease of kerosene by supplying ammonia gas. Ammonia gas supply increases NOx in the exhaust gas dramatically. However post-combustion clean-up of the exhaust gas via SCR can reduce NOx successfully.© 2015 ASME

Micro Gas Turbine With Ceramic Nozzle and Rotor

A series of operation tests of a ceramic micro gas turbine has been successfully carried out. The baseline machine is a small single-shaft turbojet engine (J-850, Sophia Precision Corp.) with a centrifugal compressor, an annular type combustor, and a radial turbine. As a first step, an Inconel 713C alloy turbine rotor of 55 mm in diameter was replaced with a ceramic rotor (SN-235, Kyocera Corporation). A running test was conducted at rotational speeds of up to 140,000 rpm in atmospheric air. At this rotor speed, the compression pressure ratio and the thrust were 3 and 100 N, respectively. The total energy level (enthalpy and kinetic energy) of the exhaust gas jet was 240 kW. If, for example, it is assumed that 10% of the total power of the exhaust jet gas was converted into electricity, the present system would correspond to a generator with 24 kW output power. The measured turbine outlet temperature was 950°C (1,740°F) and the turbine inlet temperature was estimated to be 1,280°C (2,340°F). Although the ceramic rotor showed no evidence of degradation, the Inconel nozzle immediately in front of the turbine rotor partially melted in this rotor condition. As a second step, the Inconel turbine nozzle and casing were replaced with ceramic parts (SN-01, Ohtsuka Ceramics Inc.). The ceramic nozzle and case were supported by metal parts. Through tests with the ceramic nozzle, it became evident that one of the key technologies for the development of ceramic gas turbines is the design of the interface between the ceramic components and the metallic components, because the difference between the coefficients of linear thermal expansion of the ceramic and metal produces large thermal stress at their interface in the high-temperature condition. A buffer material made of alumina fiber was therefore introduced at the interface between the ceramic and metal.Copyright

System Analysis of IGFC With Exergy Recuperation Utilizing Low-Grade Coal

Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) is expected to be the most efficient power generation system in coal fired power generation systems [1,2]. The Japanese project of the Strategic Technical Platform for Clean Coal Technology (STEP-CCT) aims a target efficiency of 65% (HHV) with exergy recuperation. We have been analyzing the processes of the exergy recuperated Integrated Coal Gasification Combined Cycle (IGCC) and the Advanced IGCC (A-IGCC) [3] which is expected to be realized in 2040. Previous studies have indicated a limitation of the quantity of high temperature steam in the case of auto-thermal reactions with the fluidized bed coal gasifier in the A-IGCC, in particular for TIT 1500 °C class gas turbine. The Advanced IGFC (A-IGFC) system can reduce the exergy loss resulting from combustion, and its ‘exergy recuperation’ is appealing. The waste heat exhausted from the fuel cells is recycled to the gasifier for steam reforming in an endothermic reaction with a low exergy loss and a high cold gas efficiency. Our current study focuses on the optimization of the unit configurations of the A-IGFC including gasifier, compressor, solid oxide fuel cell (SOFC), combustor, gas turbine, heat recovery steam generator (HRSG), and steam turbine. The process simulator HYSYS®.Plant (Aspen technology Inc.) is employed in order to express the gasifier, the SOFC and the other units. The optimum construction over the whole system by numerical simulation was examined for higher energy utilization efficiency. Under ideal conditions using bituminous coal, we verified the power generation efficiency to be 64.5% (HHV). However, utilizing low-grade coals, i.e., lignite and sub-bituminous coal, is deemed an important future energy resource to compensate for a decreasing supply of good-quality bituminous coal. For these low-grade coals, the power generation efficiency was as high as 53.6% (HHV) under the following conditions: Gasifier inlet: coal 23.6 Kg/s (667 MJ/s), steam 16.44 kg/s; Reactor reforming gas: 30.0, 8.7, 2.0, 0.8, 0.3, 0.05, 0.24, 0.14, 0.1 and 5.5 kg/s for CO, CO2 , H2 , CH4 , C2 H4 , C2 H6 , C3 H6 , HCN, N2 and H2 O respectively. The projected power outputs with this system were, SOFC: 214 MW; Gas turbine: 318 MW; Steam turbine: 86 MW.Copyright

Micro Gas Turbine With Ceramic Rotor

A series of operation tests by using a desktop size gas turbine has been successfully carried out. In the first step of the tests, we have concentrated ourselves on the operation at elevated temperatures. Thus the duration of the bench test at each rotation speed was set to be 1 minute. The baseline machine is J-850 (Sophia Precision, Co., Ltd.) originally made for model airplanes. In this study, we replaced an INCONEL 713C alloy turbine rotor with 5.5 cm diameter into a type SN235 ceramic rotor (Kyocera Corporation). Mixture of 70% white kerosene and 30% gasoline was used as the fuel. The running test was made at the rotational speeds up to 140,000 r.p.m. in the atmospheric air. The basic performance of the small gas turbine was found as follows: At 140,000 r.p.m., 1) the turbine inlet temperature was estimated to be higher than 1,200. This estimation was supported by the observation of the partially melted INCONEL alloy nozzle located before the ceramic rotor. But the ceramic rotor revealed no damages. 2) The compression ratio and the thrust of the ceramic rotor turbine attained at 140,000 r.p.m. were 3 and 100 N, respectively. 3) Total energy level of the exhaust gas jet was 240 kW at the same rotation speed. Experiences learned from the present running tests suggest that the small gas turbine system employed in this study could be a useful tool to quicken the cycle of R & D of micro ceramic gas turbines with reasonable costs.Copyright

Analysis of IGFC With Exergy Recuperation and Carbon Dioxide Separation Unit

Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) is expected to be the most efficient power generation system in coal fired power generation systems [1,2]. However, more energy efficient power generation system has to be developed to decrease CO2 emission in the middle and long term. Thus, the authors have proposed Advanced Integrated Coal Gasification Combined Cycle (A-IGCC) and Advanced IGFC (A-IGFC) systems, which utilize exhaust heat from solid oxide fuel cells (SOFC) and / or a gas turbine as a heat source of gasification (exergy recuperation) [3]. Previously A-IGCC [4] and A-IGFC [5] without CO2 capture option were analyzed with the process simulator HYSYS®.Plant (Aspen technology Inc.) to calculate thermal efficiencies of the proposed systems. Then IGCC and A-IGCC with CO2 capture option [6, 7] were analyzed with Amine process simulator AMSIM(DBR), a module in PRO/II® (Invensys Process Systems Japan, Inc) combined with HYSYS®.Plant model. It shows in the results of thermal efficiency with CO2 capture option that the penalty of A-IGCC case is larger than that of IGCC case, indicating somewhat scope for increase of exergy recuperation in A-IGCC case [6]. This study deals in the analyses of A-IGFC with CO2 separation unit.Copyright

Energy Flow of Advanced IGCC With CO2 Capture Option

Conventional IGCC (integrated gasification combined cycle) employs a cascaded energy flow with a high efficiency, yet it is difficult to achieve over 50% HHV (higher heating value). The current study proposes an alternative model of exergy recuperated Advanced IGCC (A-IGCC) to achieve higher plant efficiency by applying an autothermal reaction in the gasifier. This requires an additional heat supply from the gas turbine exhaust and the steam extracted from the steam turbine. System and performance analyses were studied on base IGCC and A-IGCC cases incorporating the heat (exergy) recuperation concept with an air-blown twin circulating fluidized bed gasifier for the gasification of sub-bituminous coal, both with and without the post combustion carbon dioxide (CO2 ) capture option. A-IGCC could deliver sufficient energy in the gasifier to the gas turbine without losing heat as resulted in IGCC. Chemical absorption methods using monoethanolamine (MEA) and methyldiethanolamine (MDEA) were selected as a CO2 absorbent. A-IGCC demonstrated a significantly higher system efficiency (51%) than IGCC (43%) without CO2 separation, provided the gas purification was at high temperature. The thermal efficiency penalty by CO2 capture was −8% using MDEA (56% absorption) and −11% using MEA (90% absorption).Copyright

Parametric Study of an Advanced IGCC

IGCC achieve high efficiency energy conversion from coal to electricity. However its efficiency is below 50% [HHV]. To achieve higher efficiency, Advanced IGCC was planned by using exergy-recuperation concept. Advanced IGCC requires many breakthroughs in technology. Advanced IGCC achieve high efficiency by using the heat of reformed gas and the application of the autothermal reaction in the gasifier. Authors try parametric study of Advanced IGCC to figure out the desirable consists of Advanced IGCC. The performance of Advanced IGCC depends on coal, gasifier condition, configuration of components, etc. The heat value of the supplied coal is 667MW [HHV]. Foreign subbituminous coal is selected as standard fuel. The adiabatic efficiencies of the compressor, the gas turbine, steam turbine and condensing turbine at standard condition were defined so that the efficiency of IGCC with 1500 °C class gas turbine is 48% [HHV] with high performance gasifier. The efficiency of IGCC reaches to 52% [HHV] by applying autothermal reaction in the gasifier. This system requires the extra heat supply in order to hold the autothermal reaction condition in the gasifier. Therefore the net efficiency of this system is about 44% [HHV]. The net efficiency of the advanced IGCC is 48% [HHV]. On the other hand, 1700 °C class advanced IGCC can achieve 51% [HHV] net efficiency and its gas turbine exhaust high temperature heat to hold autothermal reaction condition. Increase of the adiabatic efficiencies of the compressor and the gas turbine enables the high efficiency of the advanced IGCC. If the adiabatic efficiency of compressor reaches to 87% and adiabatic efficiency of the gas turbine reaches to 92%, 1700 °C class advanced IGCC has the potential of over 60% [HHV].Copyright

Active Control of Flow Separation Over a NACA0024 Airfoil by DBD Plasma Actuator and FBG Sensor

Dielectric barrier discharge plasma actuators (DBD-PA) and fiber Bragg grating flow sensors (FBG-FS) have been investigated for active control of flow separation around a NACA0024 airfoil. Tangential jets were produced in the vicinity of the DBD-PA slightly aft of the leading edge of the airfoil. The flow separation control ability was evaluated at a low Reynolds number, Re = 5.0×104 , in an open-circuit wind tunnel. Analysis of instantaneous and time-averaged velocity distributions around the airfoil was achieved using a particle image velocimetry (PIV) system. The flow conditions induced by the DBD-PA to suppress the flow separation were found for angles of attack of α = 8°, 12°, and 16°. When unaided by the DBD-PA system, flow separations from NACA0024 airfoil are suppressed significantly for certain Reynolds numbers and angles of attack. FBG-FS attached a chord-wise cantilever near the trailing edge of the airfoil was used to measure strain fluctuations for its feasibility to detect flow separation in real time and construct feedback control system with DBD-PA. In this study, it was found that standard deviations of strain fluctuations increase obviously in cases of flow conditions at which the flow around NACA0024 airfoil separates.Copyright

Remote Measurement and Heat Demand Control of CHP System With Heat Storage at Sapporo City University

Combined heat and power (CHP) systems are widely used to prevent global warming and reduce energy costs. Both high efficiency of the elements and good coordination of the systems are considered as the points to solve. A microturbine CHP with a latent heat storage system was demonstrated at Sapporo City University. The heat exchanger of the CHP and an economizer were located in parallel downstream a bypass-dumper of the exhaust gas. The latent heat storage tank was located downstream the economizer. The bypass-dumper released exhaust gas when the boiler water in the heat exchanger exceeded 90°C. It is very important to use the heat supply of hot water as much as possible. At Sapporo City University, the winter term heat demand from 6pm to 7pm was somewhat smaller than that from 8am to 6pm. We tested a partial load from 6pm to 7pm to observe how it would respond to the heat demand. The heat supply from the microturbine CHP from 6pm to 7pm was shown to be controllable with heat storage. The heat supply from the microturbine CHP at the lowest power was larger than the heat demand so without the heat storage it was uncontrollable.Copyright

Gas Turbine With Ceramic and Metal Components

To obtain a micro gas turbine with high turbine inlet temperature and efficiency, a series of running tests has been carried out. J-850 jet engine (Sophia Precision Co., Ltd.) was chosen as a base line machine. The turbine nozzle and the rotor are replaced to ceramic type. The observed problems occurring during the running test taught us various measures to improve heat tolerance of the engine. Especially, the ceramic nozzle vanes can be installed on a metal disk very simply. The disk structure enables us to replace blades with various shape and attack angles. We tried to operate several sets of ceramic components and metal components, such as a set of a ceramic turbine nozzle and an Inconel rotor, etc.Copyright