8.3 Development of turbine-blades, rotors and other major components

8.3.1 R&D Goals

8.3.1.1 Research Objective

(1) Technology Development Subjects

(2) Technology Development Objectives

8.3.1.2 Scope of Research

8.3.2 Results in FY 1998

(1) Development of turbine blades cooling technology

1. Outline of the Test

   1) Outline of major test results is as follows.

   • Evaluation tests for blades cooling were conducted from October 1998 to December 1998. Test condition considered the correlation to commercial plants, and the blade length for the test was approximately 35mm to 40mm against the half scale of commercial use. And heat flux and Re. number set a numerical order to be able to apply the correlation to commercial use. The detailed test condition is shown in Table 8-3-1.

   2) Major specification of the test blades are as follows, and detail is shown in Table 8-3-2.

   • WATER COOLING METHOD: Mother material for a stationary vane with water cooling hired copper alloy (CZ-Cu), and a rotating blade hired Nickel alloy with single crystal. Thermal barrier coating (TBC) is Zirconium-Yttrium (Zr₂O₃-Y₂O₃) for top coating and its fabrication method hired partially electron beam physical vapor deposition (EB-PVD).

   • FULL RECOVERY STEAM COOLING METHOD: Both vanes and blades hired steam recovery cooling method completely, and mother metal material is cobalt base alloy. TBC is conventional one but thickness of the topcoat is 0.5 mm, double thickness of commercial use.

   • RECOVERY STEAM COOLING METHOD: The test blades for the evaluation ware recovery steam cooling type with small film cooling, and the material of them hired Nickel alloy with single crystal known as second generation material of the turbine blades metal. EB-PVD method is hired to the TBC on the blades and vanes.

   3) As considering safety program of the evaluation tests toward stationary vanes and blades, test temperature rose up step-by step as 1000°C, 1200°C,1500°C and 1700°C. Necessary measurement of temperature, pressure, cooling quantity etc for required evaluation were done at each step. Finally 1700°C test was planned to conduct 20 minuets test for measurement.

2. Test results

   Total test hours were merely different among the three cases, but test data of 1700°C for each method were gotten. In spite of short test hours, feasibility of the TBC was verified, and over 60% plant efficiency would be achieved by the re-calculation based upon the gotten data. Each test results are shown in Table 8-3-2.

   1) As one point in the test data for water cooling methods showed the possibility of vaporization of water , target metal temperature below 300°C and good correlation for design figures were verified.

   2) As a point of metal temperature was partially exceeded to 900°C, overall metal temperature obtained the good results as below 820°C, design criteria.

   3) A point of the data was partially recognized higher metal temperature of 900°C, but in considering overall evaluation, good correlation was confirmed .

3. Evaluation result of the turbine cooling technology

   The test evaluation for the cooling methods, factory laboratory tests and design capability was evaluated against re-entrusted companies.

   As the result of it, the order of the evaluation was Toshiba for 83.31 points, Hitachi for 83.01 and Mitsubishi (MHI) for 82.13.

   However a item of cooling method at Tashiro test result showed Hitachi, Toshiba and Mitsubishi in row, one of cooling method in overall evaluation was Mitsubishi, Hitachi and Toshiba, and the other of structural feasibility was Toshiba, Hitachi and Mitsubishi which remained some consideration on these diversified evaluation. The evaluation result in detail is shown in Table 8-3-2.

4. Feature consideration

   Following are subjects to the future consideration as requested.

   1. To conduct rotating tests for confirmation of fluid dynamic analysis.
   2. To develop a confirmation method and confirmation of long term test of TBC
   3. To review efficiency and reliability of the turbine system with rotor cooling etc.
   4. To develop a pyrometer with high reliability

(2) Development of rotor cooling technology

1. Development of seal mechanism and computerized fluid dynamics

   Development of computerized fluid dynamics were conducted to the influence of rotor cooling and seal quantity by introduction of turbine main stream turbulence. Fig. 8-3-1 showed the elements of turbulence such as unbalance combustion and offset of rotor axis, and as assumed three-dimension turbulence around seal outlet, the introduction of its steam quantity was analyzed. This result is shown in Fig. 8-3-4. By the analysis of the results about the influence to seal performance with three-dimension turbulence, design method concerned three-dimension turbulence was created as Fig. 8-3-2, adding main stream parameters of the rotor cooling system shown in Fig. 8-3-3.

2. Development of rotor cooling technology

   Basic structure design, structure strength study and optimum cooling design of rotor desks were conducted. As a result of the study on comparison between conventional seal performance and the seal performance required for the system in this project, the plant efficiency was revised from 61.8% of planned efficiency to 60.1% for a 500MW-hydrogen combustion power plant. This study result is shown in Table 8-3-3 as comparison of the efficiency between conventional one and study case, and steam model introducing optimum desks for rotor system is shown in Fig. 8-3-5.

3. Future consideration

   Followings are subject to future study as concerned.

   1. To verify accuracy of CFD under high temperature and high pressure
   2. To continuously analyze heat fluid dynamics and structure for aiming commercial use
   3. To develop new seal structure to improve system performance
   4. To analyze mechanical strength in seal steam pass in detail