Micro Gas Turbine With Ceramic Nozzle and Rotor

Abstract

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.

Small recuperated ceramic microturbine demonstrator concept

“…The small test engine embodied a 55 mm diameter radial flow turbine (about the same size as ceramic turbines used in automobile turbochargers in Japan), and for this application was fabricated in SN235 ceramic material by Kyocera [21]. While some problems were encountered a rotational speed of 140,000 rpm was demonstrated at a turbine inlet temperature of 1280°C [22]. Continuing development led to a 1-h test run at a temperature above 1000°C without severe damage [23], and further duration tests are planned.…”

Micro Gas Turbine With Ceramic Nozzles and Rotor: Part 2

“…As in the previous studies [11,12,13], J-850 jet engine (Sophia Precision Co., Ltd) was used as a baseline engine. Figure 1 and Table 1 indicate the whole view and the specifications of the baseline engine, respectively.…”

“…Type 2 has ceramic turbine-nozzle casing and ceramic nozzle vanes [12]. The outer casing was replaced by a thick one.…”

“…A series of our study aims at further accumulation of experience and knowledge on the design and fabrication of durable micro ceramic gas turbine systems [11,12,13]. In this paper, we discuss performances of prototypes with various metal-ceramic hybrid configurations.…”

FOD Simulation for Ceramic Turbine Blades

“…1,2) Moreover, recent growing interest in small, distributed energy systems seems likely to facilitate development of small CGTs with a power of 100 kW or less. 3,4) In this context, Tsuchiya et al evaluated the economic competitiveness of micro-gas turbine cogeneration systems based on efficiency and maintenance cost, 5) suggesting that increasing the thermal efficiency of the micro-CGT is an important issue.…”