Keisuke Miura

Performance Demonstration of the Full-Size Multi-Cluster Combustor for DME Under Real Engine Conditions

DME (dimethyl ether: CH3 OCH3 ) is currently attracting worldwide attention because it is a clean fuel which can be synthesized from various materials such as natural gas, coal, biomass, etc. But DME has the possibility of spontaneous ignition in gas turbine use because of its low auto-ignition temperature. To avoid spontaneous ignition or flash-back, a coaxial jet cluster nozzle burner configuration was proposed previously which can mix air and fuel effectively within a short time. In this work, demonstration tests were carried out for the developed full size combustor, called the multi cluster combustor for 25MW class gas turbine. The combustor, which is composed of cluster nozzle burners, was tested under practical gas turbine operating conditions from start up to base load using a full pressure combustion test rig. In the tests, LNG was also used as the test fuel because it is expected to be used as a back up fuel when DME is first introduced for wide commercial use. Test results showed good combustion performances for the developed multi cluster combustor. NOx emission level was below 24ppmv (15%O2 ) and combustion efficiency was over 99.9% for the base load condition of the 25MW class gas turbine when fueled with DME or LNG. Dynamic pressure level and liner metal temperature were low. No flash-back phenomena occurred throughout the demonstration tests.Copyright

Full Scale Testing of a Cluster Nozzle Burner for the Advanced Humid Air Turbine

The advanced humid air turbine (AHAT) system, which has a humidifier and a heat recovery system has the advantage of improving the thermal efficiency of gas turbine power generation without needing an extremely high firing temperature and pressure ratio. A pilot plant and a prototype gas turbine adapted to the AHAT system have been developed. Before the pilot plant test, an experimental study using a combustion test rig was carried out to obtain the characteristics of a prototype combustor and it is described in this presentation. The combustion conditions in the AHAT system are characterized by both high humidity and high temperature air (17.6wt%, 629C). It is expected that a low flame temperature caused by the high humidity condition will decrease NOx emission while the high temperature air condition will sustain flame stability. However, the latter condition has the disadvantage of causing NOx emission and autoignition of fuel. A cluster nozzle burner configuration, which has many fuel and air coaxial jet streams, was previously proposed. The cluster nozzle burner can mix fuel and air effectively within a short time which makes it suited to the AHAT system and able to cope with both flame stability and NOx reduction problems. The combustion rig test results showed good combustion performance for the developed cluster nozzle burner. Both the high temperature condition of the AHAT system and the recirculation zone generated by swirling of center burner air sustained flame stability at a level sufficient for the nozzle burner in AHAT operation. The low flame temperature due to the high humidity condition was effective in decreasing NOx emission, which was less than 10ppm at 50-100% load.Copyright

Numerical Simulation of Turbulent Combustion Flows for Coaxial Jet Cluster Burner

We have developed a burner for the gas turbine combustor, which was high efficiency and low environmental load. This burner is named the “coaxial jet cluster burner” and, as the name indicates, it has multiple fuel nozzles and holes in a coaxial arrangement. To form lean premixed combustion, this burner mixes fuel and air in the multiple holes rapidly. The burner can change the combustion form between premixed and non-premixed combustion by controlling the mixing. However, the combustion field coexisting with premixed and non-premixed combustion is complicated. The phenomena that occur in the combustion field should be understood in detail.Therefore, we have developed the hybrid turbulent combustion (HTC) model to calculate the form in which non-premixed flame coexists with premixed flame. Turbulent flow has been simulated using a large eddy simulation (LES) with a dynamic sub grid scale (SGS) model coupled with the HTC model. These models were programmed to a simulation tool based on the OpenFOAM library. However, there were unclear points about their applicability to an actual machine evaluation and the predictive precision of CO concentration which affects burner performance. In this study, we validate the HTC model by comparing its results with measured gas temperature and gas concentration distributions obtained with a coaxial jet cluster burner test rig under atmospheric pressure. In addition, we analyze the CO generation mechanism for the lean premixed combustion in the burner.Copyright