Coupled CFD and FEA Project Work

CFD and FEA services are our core business and have been for more than 20 years. We are broad generalists in the consulting services business and our differentiator is experience.

Recently we just completed a coupled computational fluid dynamics (CFD) and finite element analysis (FEA) project on a "Power Augmentation" device that fits onto an existing 60kW gas turbine. The energy physics of this device is to spray water droplets into the inlet of the compressor side of the turbine, thereby increasing the mass density of the already 100% saturated air. This air-water mixture is then combusted with increased gas flow, yielding a 10 to 15% boost in energy output from the turbine. In other words, one can take a 60kW turbine and turbocharge it to ~70kW at no more than 1% of the original turbine cost.

The challenge for our client (an electrical utility) is that this device is bolted onto the flow housing at the inlet to the gas turbine. If this device fails, then parts would directly enter the turbine, leading to a very expensive repair operation plus unexpected disruption to the utility’s power grid. The graphics down below provide a generalized description of the CFD and FEA models. Air enters through the filter house and then around the housing, through some guide vanes and then into the compressor-side of the gas turbine. The CFD analysis (using STAR-CCM+) provides us with component pressures over the housing and the water spray system, which were then mapped onto a FEA model (using FEMAP). The FEA model was then exercised through a static stress, normal modes and modal frequency analyses (using NX Nastran). To verify this work, a CFD mesh convergence study was done and the FEA work was checked against hand calculations.

Results assured the client that the power augmentation device was more than structurally adequate and could easily handle the power plant’s dominate 60Hz vibration plus any multiples. Along with our structural recommendation we also discussed the importance of using tie-offs on all bolts and a complete corrosion/weld inspection at maintenance intervals. Our experience is more than just numbers but how structures and systems operate within their enviroments. Simply put, we aim to own the structure that we analyze and to ensure that it never fails based on the complete envelope of operating, material and loading factors.

 

Air Inlet Section (Filter House and Air Flow Housing) of 60kW Gas Turbine

Coupled CFD and FEA Project Work February 2017 - fig 1

 

CFD Air Flow Modeling (STAR-CCM+)

Coupled CFD and FEA Project Work February 2017 - fig 2

 

FEA Stress Results (per CFD pressure loads)

Normal Modes and Sine-Sweep Analysis

Coupled CFD and FEA Project Work February 2017 - fig 3

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