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Kumar R K ¹, Raghavendra Naik ¹, Saravanan V ¹, Janardhana M ¹

Affiliations
1 Central Power Research Institute, Bangalore-560080, IN

Abstract

The splitter plates of coal burners in Indian thermal plants are subjected to severe erosion and erosioncorrosion conditions owing to the combined effect of abrasive nature of coal and elevated service temperature environment. During service, tilting of splitter plates is adopted to achieve the desired final steam outlet temperature which shifts the fireball location and heat release area in the combustion zone. The tilt condition gives rise to a change in the incidence angle of the coal particle as well as the change in flow profile. The erosion life of these plates is predominantly affected by the coal particle velocity, impact angle, particle size and steady state metal temperature during service. The sensitivity of burner tilt angle on the erosion life requires an understanding of primary air with coal particle flow phenomenon within the burners. The effect of burner tilt angle on the erosion of presently used SS310 grade splitter material was studied through computational fluid dynamics. The erosion sensitive velocity exponent was calculated based on the laboratory simulated erosion tests at elevated temperatures upto 700°C. The life of the splitter plates was calculated based on the predicted erosion rate intensity.

Keywords

Coal burner, high-temperature erosion, Computational Fluid Dynamics (CFD)

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Kumar R K ¹, Janardhana M ¹, Bhaskar Sharma K V ²

Affiliations
1 Joint Director, Central Power Research Institute, Bangalore -560080, IN
2 Sampoorna Rotor Dynamics Consultancy, Bangalore-560040, IN

Abstract

Blade failures in steam and gas turbines are quite a common occurrence. The last stages of steam turbines are designed to have the lowest possible fluid temperature. In view of the longest blade length in the last stages, the blades are subjected to highest bending moment forces and susceptible for erosion-corrosion phenomenon owing to the low service temperature environment. The failure analysis of last stage blade of 54 MW direct condensing type gas turbine are presented. The blade was made of martensitic grade stainless steel. Detailed analysis of the blade surface, lacing wire hole as well as the fracture morphology was analyzed using SEM-EDX. The probable reason for the failure of the blade was brought out based on the detailed investigations of the failed blade as well as the vibration signature analysis at the time of failure incidence.

Keywords

Failure Analysis, Gas Turbine Blade, Vibration Frequency, Fractography

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Raghavendra Naik K ¹, Kumar R K ², Saravanan V ², Shekhar Kumar M ³

Affiliations
1 Senior Research Fellow, Materials Technology Division, Central Power Research Institue, Bangalore-560080, IN
2 Joint Director, Materials Technology Division, Central Power Research Institue,Bangalore-560080, IN
3 Additional Director, Materials Technology Division, Central Power Research Institue,Bangalore-560080, IN

Abstract

High temperature erosion is generally encountered in boiler components in thermal power plants, especially in superheater, reheater, and economisers parts, where in fly ash particles attack the boiler components and cause high temperature erosion phenomena. It is known as fly ash erosion. The erosion behavior at elevated temperature is much different from that of room temperature erosion as there would be a higher erosion loss encountered at higher temperature due to higher plastic deformation as well as weak bonding between grains/particles. It is therefore imperative to study in depth the erosion wear assessment both at room temperature as well as at elevated temperature in the laboratory. This paper investigates thermal sprayed coatings produced by the high velocity oxygen fuel (HVOF) to improve the material performance under such conditions. 35 WC-NiCrBSi HVOF sprayed coatings were tested under high temperature (up to 700℃) erosion by means of an apparatus that simulated real conditions. The results showed that under these tests conditions the 35WC-NiCrBSi coating worn about 1.4 times less than bare SS-310 steel at room temperature and 300℃ Temperature, while at 700℃ C 35WC-NiCrBSi worns about 2 times higher than bare SS-310 steel at 90℃ impact angle. This shows 35WC-NiCrBSi erosion sensitivity at higher temperature.

Keywords

Thermal Spray Coating, HVOF, High Temperature Erosion, Impingement Angles, Surface Analysis.

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