Satoshi Tanimura

Burning characteristics of premixed sprays and gas-liquid coburning mixtures☆

Abstract A premixed spray burner was carefully designed for the observation of stable turbulent flames propagating in a droplet cloud suspended in a stream of air or for a gaseous fuel-air mixture. Various methods were examined to determine the most suitable reference surface of a spray flame, corresponding to its burning velocity. Difficulties arose in finding the reference flame surface, which governs the burning velocity of sprays, because the spray flames were usually thick and unsteady. It was found that the surface on which the OH radical emission had a peak intensity was more suitable as a reference flame surface than the surfaces determined by either direct or schlieren photography. The qualitative features of our burning velocity data for kerosene sprays agree with those of other investigators; that is, we found a linear dependence on the fuel-to-air ratio and an inverse proportionality to the Sauter mean diameter. Concerning coburning, there exists an optimum kerosene-to-propane mass flow ratio and an optimum mean droplet diameter that maximizes the burning velocity. Instantaneous flame images in OH and C 2 radical bands seem to suggest that group combustion occurs in a spray flame.

Advanced Dry Low NOx Combustor for Mitsubishi G Class Gas Turbines

Design features and verification results for Mitsubishi Heavy Industries’ (MHI) latest gas Dry Low NOx (DLN) combustor technology for 1500°C G-class gas turbines is presented. Key design improvements include: A) Inlet aerodynamics: CFD based design air inlet for improved flow uniformity into the pre-mixers. B) Fuel/air mixing: integrated fuel injector and swirler to decrease local flame hot-spots and reduce NOx while preventing flashback. C) Combustor aerodynamics: redesigned flame holding baffle and combustor outer wall to achieve better flame stability and NOx reduction. D) Acoustic resonator: two acoustic resonators, one in the liner to prevent high frequency combustion dynamics and the other in the bypass valve for low frequency dynamics. Tests were conducted to verify the new DLN combustor by installing it in a M501G1 gas turbine at MHI’s T-Point combined cycle power plant, with more than 1500 special measurements. Following the preliminary verification period the combustor was installed at the same plant for long-term operation. The results demonstrate the following capabilities: A) Less than 15ppm NOx operation with turn down to 60% load. B) Stable combustion dynamics at all load levels. C) High combustor ignition reliability. D) Suitable for daily start and stop (DSS) operation. E) Good reliability and durability. F) Retrofitable to existing 501G and 701G gas turbines.Copyright

New Dry Low NOx Combustor for Mitsubishi M501/701G

MHI G class gas turbine was designed to operate with a Turbine Inlet Temperature (TIT) of 1500 °C. This elevated temperature results in high thermal efficiency but also can induce relatively high emissions. MHI has developed a new Dry Low NOx (DLN) combustor that improves this class turbine compliance with stringent environmental regulations imposed around world. In addition to targeting an environmentally friendly combustor with lower emissions, the redesigned DLN combustor also improves the stability margin. Verification tests of the new DLN combustor were conducted in a M501G1 gas turbine at MHI’s T-Point Combined Cycle Power Plant from May, 2005 to March, 2007. In addition to verifying lower emission levels, these tests confirmed a wide stable operation margin as well as the reliability and durability of the components. The new design is optimized to be retrofitted into existing G class engines. The combustor is now in mass production as a MHI’s standard combustor. This paper describes the design process applied for the new combustor, including the Computational fluid Dynamics’ (CFD) and other analytical tools used.Copyright

Investigation of Combustion Structure Inside Low NOx Combustors for a 1500°C-Class Gas Turbine

This paper describes the cold flow tests and low pressure combustion tests which were conducted for the development of a 1500°C-class low NOx combustion system. In the cold flow tests, the effect of vane angle and the momentum ratio of fuel to air flow on mixing characteristics inside the premixing nozzles was investigated. The stabilization of the flow field inside the combustor was confirmed by measurement of the axial velocity distribution and observations by using a tuft of soft thread.Combustion characteristics in terms of emissions and stability were investigated initially by low pressure combustion tests, and the gas temperature distribution inside the combustor was measured. NOx emissions for a 1500°C-class gas turbine as low as 50ppm at 15% oxygen at design pressure were demonstrated.Copyright

DLN Technology Update for the M701DA: Enhancing Vintage Gas Turbine Models With Latest Technology

While the Gas Turbine design process is often focused on the development of the next advanced frame significant benefits can be achieved by retrofitting the latest technology in mature gas turbines model. This dissemination of advanced technology is a company philosophy of constant equipment enhancement. This paper will track the design process that is typically followed when enhancing vintage equipment. Also consideration will be discussed of transferring technology between 50 and 60 Hert frequency fleets.Copyright

Burning velocities of premixed sprays and their coburning characteristics.

Various methods were examined for determination of the burning velocities of liquid fuel sprays. Difficulties existed in finding the reference flame surface which governed the burning velocity of sprays since spray flames were usually thick and rather unsteady. The surface where the OH radical emission had a peak intensity was more suitable as a reference flame surface than the surfaces determined by schlieren or direct photography. The burning velocities of premixed sprays of kerosene were determined using a carefully-designed premixed spray burner. The coburning characteristic of premixed sprays of kerosene were also determined for the case of propane-kerosene spray-air mixture combustion.