Gas Turbine Exhaust, SCR and HRSG CFD Analysis
Improving exhaust performance, emissions compliance and system reliability
Gas turbine exhaust systems play a critical role in plant efficiency, emissions compliance and long-term reliability. Poor flow distribution, thermal maldistribution or inadequate mixing can lead to reduced SCR performance, elevated ammonia slip, measurement uncertainty and premature equipment degradation.
Navier provides high-fidelity CFD analysis of gas turbine exhaust systems to support compliant operation, emissions optimisation and robust design across new-build and operational assets.
Our work focuses on understanding how exhaust flow, temperature and species actually behave through diffusers, ductwork, SCR reactors and stacks under real operating conditions.
Exhaust system aerodynamics and thermal performance
We apply CFD to assess exhaust ducting and diffuser systems, including:
- Exhaust diffuser and transition-duct performance
- Pressure-loss prediction and optimisation
- Velocity and temperature maldistribution
- Thermal stratification and hot-spot identification
- Assessment of off-design and part-load operation
- Impact of upstream engine operating conditions
These studies help identify root causes of excessive pressure loss, thermal fatigue risk and uneven downstream loading.
SCR performance, AIG and ammonia mixing
Effective NOx reduction depends on achieving uniform flow, temperature and reagent distribution at the catalyst face. CFD allows these interactions to be assessed in detail before physical modification or commissioning.
Typical analyses include:
- Velocity and temperature distribution into SCR reactors
- Ammonia Injection Grid (AIG) optimisation
- Ammonia–air mixing effectiveness
- Catalyst-face uniformity assessment
- Prediction of NOx reduction performance and ammonia slip
- Sensitivity studies for load variation and transient operation
CFD provides a robust basis for improving SCR efficiency, reducing reagent consumption and supporting emissions-compliance strategies.
HRSG flow distribution and thermal performance
Heat Recovery Steam Generators (HRSGs) are highly sensitive to upstream exhaust flow and temperature distribution. Maldistribution at the HRSG inlet can lead to uneven tube-bank loading, elevated thermal gradients, fatigue damage and long-term reliability issues.
Navier applies CFD to assess and improve HRSG inlet conditions, focusing on the interaction between the gas turbine exhaust system and downstream heat-recovery equipment.
Typical HRSG-related studies include:
- Exhaust flow and temperature distribution at the HRSG inlet plane
- Identification of maldistribution and thermal hot spots
- Assessment of diffuser and transition-duct performance
- Evaluation of duct geometry, turning vanes and flow-conditioning devices
- Tube-bank loading uniformity and fatigue risk indicators
- Transient thermal behaviour during startup and shutdown
- Support for retrofit modifications and life-extension studies
These analyses help reduce thermal stress, improve heat recovery efficiency and support long-term HRSG reliability.
Exhaust stack behaviour and dispersion assessment
For plants where exhaust discharge interacts with surrounding structures or air intakes, CFD can be used to assess plume behaviour and recirculation risk.
We support:
- Exhaust stack plume visualisation and dispersion studies
- Recirculation risk assessment for nearby intakes and HVAC systems
- Thermal buoyancy and momentum-driven plume behaviour
- Support for stack height justification and layout optimisation
These studies are particularly valuable for constrained sites, retrofits and plant upgrades.
Design reviews, troubleshooting and retrofit support
Navier supports both EPC and operational teams with CFD-based design verification and troubleshooting, including:
- Review of proposed exhaust and SCR layouts
- Diagnosis of under-performing SCR systems
- Support for AIG retrofits or duct modifications
- Investigation of temperature or flow-induced fatigue issues
- Evidence-based justification for design changes
Our focus is on delivering clear engineering insight that can be acted upon, not just visual output.
Why Navier?
Clients work with Navier because we combine advanced CFD capability with practical power-generation engineering experience.
- Independent, vendor-neutral consultancy
- High-fidelity analysis applied where it adds value
- Clear conclusions aligned with plant operation
- Experience across intake, exhaust, SCR and balance-of-plant systems
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If you are experiencing emissions challenges, flow maldistribution or exhaust-system performance issues, we can help you understand the root causes and identify practical solutions.
Need Help?
Contact Navier on +44(0)115 6979141 or info@navier-flow-consultants.com for a free initial consultation with one of our CFD experts and receive a competitive fixed price quotation, with zero obligation. Alternatively, if you’d like to learn more about how we structure a CFD project, browse our ‘How We Work’ page.