8. Subtask 8 : Development of Hydrogen-combustion Turbine

8.2 Development of Combustion Technology

8.2.1 R&D Goals

8.2.1.1 Background

Since 1993, the investigation has been started on combustion technology in hydrogen-oxygen combustor. In 1994, the combustion tests were conducted using small burners, and cooling and dilution structures of combustor wall are investigated and examined. Since 1995, combustion method and basic structure have been examined more concretely by means of the model combustors. 3 types of combustion methods and basic structures have been proposed and the examination has been done on various measuring methods necessary for test and assessment of combustors. In order to evaluate these combustors, the combustors for evaluation tests, the high-pressure combustion test facility (test facility for evaluation of combustor), and the measuring device have been designed and produced.

8.2.1.2 Objective

8.2.2 Results in FY 1998

8.2.2.1 Evaluation test of combustors

(1) Oxygen-diluting combustion method ( I ) (annular type combustor)

1. The smooth ignition is possible.

2. Although the pressure drop rate is about 1.2% at the rated condition, the pressure drop of hydrogen and that of oxygen are about 0.8MPa and 1.2MPa, respectively.

3. Neither misfire nor abnormal combustion is observed. Maximum pressure variation is 10kPa inside the combustor.

4. Both concentrations of residual hydrogen and oxygen are about 0.5 to 1% near the stoichiometric ratio, and the influence of temperature or pressure is not observed remarkably (Fig.8-2-3).

5. The pattern factor of temperature distribution of outlet gas is about 10% at the rated condition (Fig.8-2-4).

6. Maximum temperature on the inner wall of liner is about 550°C at the rated condition (Fig.8-2-5).

(2) Hydrogen-Oxygen direct combustion method (Can type combustor)
(Combustion method: diluting with steam after hydrogen-oxygen combustion near burner)

The oxygen nozzle was put out of joint at the temperature condition of 1500°C. Although the test data couldn't be gained at the rated condition, the performance of the combustor is estimated as follows, based on the results of high-pressure and atmospheric pressure tests.

1. The smooth ignition is possible (Fig.8-2-6).

2. It is estimated that the pressure drop rate should be about 1.7% at the rated condition, and that the pressure drop of hydrogen and that of oxygen should be about 0.2MPa (Fig.8-2-7).

3. Neither misfire nor abnormal combustion is observed up to 1500°C. Maximum pressure variation is 6kPa inside the combustor, and it is estimated to be almost same even at the rated condition

4. The concentrations of residual hydrogen and oxygen in the high-pressure condition coincide with those in the atmospheric pressure condition, and they are estimated to be about 0.5 to 1% at the rated condition.

5. It is estimated that the pattern factor of temperature distribution of outlet gas should be about 15% at the rated condition.

6. It is estimated that maximum temperatures on the liner wall and on the wall of transition piece should be 500 to 600°C and 600 to 700°C, respectively, at the rated condition.

(3) Oxygen-diluting combustion method ( II ) (Can type combustor)
(Combustion method: Supplying oxygen and steam from scoop after premixing them, and combusting them with hydrogen)

1. The smooth ignition is possible.

2. At the rated condition, the pressure drop rate is about 1.5%, and the pressure drop of hydrogen and that of oxygen are about 0.2MPa and 0.1MPa, respectively.

3. Neither misfire nor abnormal combustion is observed. Maximum pressure variation is 0.1kPa inside the combustor.

4. Since the measuring device was not adjusted very well, the measured concentration of residual hydrogen was high. But, the influence of temperature or pressure is not observed remarkbly, and it is estimated that the concentrations of residual hydrogen and oxygen should be about 0.5 to 1% near the stoichiometric ratio.

5. Although the maximum temperature couldn't be measured at the rated condition because the thermocouple was snapped, it is estimated that the pattern factor of temperature distribution of outlet gas should be about 19% at the rated condition (Fig.8-2-8).

6. The maximum temperatures on the liner wall and on the wall of the transition piece are about 620°C and 840°C, respectively, at the rated condition (Fig.8-2-9).

8.2.2.2 Examination on measuring method

(1) The device continuously measuring residual gas concentrations

(2) The gas temperature probe

8.2.2.3 Evaluation of combustors

as for combustion method and basic structure, safety, controllability, maintainability, and future possibility:

as for combustion performance, characteristic of ignition, pressure drop, combustion stability, concentrations of residual hydrogen and oxygen, distribution of outlet gas temperature and distribution of wall temperature.

As a result of the assessment, the annular type combustor with oxygen-diluting combustion method is selected as the optimal combustor for the hydrogen-combustion turbine (Table 8-2-1).

8.2.3 Future studies