Solutions

Combustion and Emissions

From predictive SI and diesel combustion to detailed chemical kinetics for knock and emissions, GT-POWER provides the accuracy and speed needed to develop cleaner, more efficient engines across all combustion concepts and fuel types.

Solution Overview

Comprehensive Combustion & Emissions Simulation

GT-POWER provides a comprehensive combustion and emissions simulation environment that supports every stage of engine development, from concept evaluation through calibration and validation. Predictive combustion models cover modern engine architectures including direct injection diesel, spark ignition, dual-fuel, pre-chamber jet ignition, and HCCI, while supporting burn rate profiles derived from cylinder pressure analysis, Wiebe functions, or neural networks. Built-in emissions prediction calculates 13 combustion products using equilibrium chemistry, with detailed kinetics and dedicated models for NOx, HC, CO, and soot. The Advanced Combustion Toolset adds a high-speed chemical kinetics solver for knock prediction, burned zone emissions, and exhaust oxidation analysis. Additional flame speed models for hydrogen, ammonia, and methanol support next-generation and alternative fuel engine development.

PREDICTIVE SI COMBUSTION

With SI Turb, users are provided a two-zone, entrainment and burn-up model which also include:

  • Combustion rates predicted based on in-cylinder conditions
    • Head and piston crown geometry from 3D-CAD
    • Spark Timing and Location(s)
    • Fuel Properties
    • Mixture Composition
    • Turbulence (incl. tumble and swirl effects)
  • High accuracy, fast run times
    • Detailed Analysis (Knock, CCV, Emissions)
    • Fast Running Models
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PREDICTIVE DIESEL COMBUSTION

With DIPulse, users are provided a phenomenological combustion model that’s designed to handle modern multi-pulse injection.

DIPulse capabilities include:

  • Combustion rate predicted based on in-cylinder conditions
    • Pressure and temperature
    • Mixture composition (fresh air, fuel, EGR/residuals)
    • Injection timings and profiles
  • Fast run time
  • Real Time/HiL capable
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MAGNITUDE SPEED UP WITH ACT

ACT (Advanced Combustion Toolset) is a collection of productivity tools that enable both increased model fidelity and faster runtimes. It includes a state of the art chemical kinetics solver that offers significantly improved computational times, enabling usage of more detailed mechanisms. Potential applications for detailed kinetics include:

  • Chemistry in Cylinder Unburned Zone (Knock)
  • Chemistry in Cylinder Burned Zone (Emissions)
  • Chemistry in Pipes/Flowsplits (Exhaust Manifold Oxidation)
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Application Highlights

Predictive Combustion & Emissions Modeling

  • Predictive combustion models for:
    • Multi-pulse direct injection diesel
    • Port and/or direct injection spark ignition
    • Dual-fuel (premixed fuel-air mixture ignited by direct injection)
    • Pre-chamber jet ignition
    • HCCI
    • User code
  • Imposed burn rate profiles for any combustion concept (derived from cylinder pressure analysis, Wiebe, map based, neural network, etc.)
  • Predictive emissions models for NOx, HC, CO and soot
  • Predictive cycle to cycle variation (CCV) models
  • Predictive knock models
  • New sub-models for alternative fuels including laminar flame speed models for hydrogen, ammonia, and methanol as well as a predictive fuel stratification model for direct injected hydrogen
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Advanced Combustion Capabilities

Explore advanced modeling capabilities for combustion analysis, emissions prediction, knock simulation, and thermal performance evaluation across a wide range of engine technologies.

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Universal Combustion Mode and Fuel Support

Model any combustion concept, including SI, diesel, dual-fuel, pre-chamber, HCCI, and more, with any fuel, including hydrogen, ammonia, and methanol. This breadth of coverage eliminates the need for separate tools across different engine development programs.

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Predictive Knock Detection and Boundary Analysis

Evaluate knock onset, intensity, and boundary conditions using detailed chemical kinetics or induction time integral models, enabling engineers to reduce reliance on costly prototype testing during combustion development.

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Mean Cycle and Cycle-to-Cycle Variation Modeling

Simulate both ensemble-averaged mean cycle combustion and individual cycle-to-cycle variation within a single modeling environment, providing a complete picture of combustion stability and variability.

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Detailed Chemical Kinetics for Emissions Prediction

Calculate any emissions species, including NOx, HC, CO, soot, and beyond, using detailed kinetics or partial equilibrium solvers, delivering the accuracy required for regulatory compliance and emissions optimization work.

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Coupled In-Cylinder Flow, Turbulence, and Combustion

GT-POWER's in-cylinder flow and turbulence model is fully coupled to combustion and heat transfer, ensuring that changes to geometry, valve events, or operating conditions propagate consistently across all physics simultaneously.

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Finite Element Cylinder Wall Temperature Integration

Combustion models interact directly with the cylinder finite element wall temperature solution, enabling accurate prediction of thermal loads, part load behavior, and dynamic operation, which is critical for durability and efficiency analysis.

Combustion and Emissions FAQs

Find answers to common questions about combustion and emissions.

  • Which emissions species does GT-POWER calculate, and how accurate are the predictions?

    GT-POWER predicts 13 combustion products by default, including NOx, CO, CO2, H2O, and SO2, using equilibrium chemistry, with the option to apply chemical kinetics for species where reaction timing matters, such as NOx and CO. CO2 is always calculated automatically as a primary product of hydrocarbon combustion. For NOx specifically, predictions are calibrated against measured data using the Extended Zeldovich mechanism, with the Stratified Burned Zone approach available for improved accuracy under stratified combustion conditions.

  • How does GT-POWER handle NOx calibration across multiple operating points?

    GT recommends calibrating NOx sequentially after predictive combustion model calibration, using just two multipliers: the NOx Calibration Multiplier and the N2 Oxidation Activation Energy Multiplier, to keep the optimization problem computationally manageable. A single set of calibration constants applied across all operating points is preferred over point-by-point tuning, which can produce unphysical results outside the calibration range. When preparing models for real-time applications, recalibration of the NOx model using the full Fast Running Model is recommended if time step size increases significantly.

  • Can measured emissions data be used directly in a GT-POWER model instead of predicting them from combustion?

    Yes. When emissions species are known from test data, they can be imposed directly in the cylinder model using the EngCylEmisMaps object, with values entered as constants, map-based dependencies on engine speed or load, or actuated dynamically from a control system. This approach is particularly useful for system-level models where combustion detail is not the primary focus but accurate exhaust composition is still required downstream.

  • What is the difference between burn rate and heat release rate in GT-POWER, and why does it matter?

    Burn rate controls the rate at which fuel and air are transferred to the burned zone, while heat release rate reflects the actual thermal energy released, which lags the burn rate when intermediate combustion products form before complete oxidation occurs. GT-POWER uses burn rate as the simulation input, never heat release rate directly; apparent heat release is available as a calculated result for comparison against pressure-derived measurements. Understanding this distinction is essential for correctly interpreting simulation outputs and avoiding calibration errors when comparing GT-POWER results to dynamometer data.

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