Release Notes 2021 R2

Virtual Fuel Cell Development – Components and Systems

Updates and improvements to AVL’s simulation solution

The latest release of AVL’s Virtual Fuel Cell Development Solution – 2021 R2 – includes various new features and functionalities for fuel cell analysis at system and component level. The following release note provides a short summary of the main highlights of this release. You can find more specific details in the product release notes of AVL CRUISE™ M and AVL FIRE™ M.

Fuel Cell System Layout and Integration

Freezing and Defrosting

The simulation-based development of PEM fuel cell cold-start strategies requires stack models that have the right physical depth to serve you as digital twin in office simulation and on virtual testbeds. Therefore, the reduced dimensionality PEM fuel cell model in CRUISE M is extended to handle liquid and frozen water in the gas diffusion layers. In addition to the existing membrane humidification model, you can now optionally activate models for liquid/frozen water formation. CRUISE M thus allows you to calculate the corresponding balance equations for water and thermal conditions of the stack. Furthermore, you can adjust the related formation rates and set the impact of liquid/frozen water on the fuel cell performance accordingly. Based on suitable parameterization, the model can be aligned with experimental data and is thus able to physically respond to different defrosting strategies.

Figure 1: PEMFC system model for cold-start and degradation analysis

Peroxide and Platinum Band formation

The chemical fuel cell degradation model in CRUISE M is complemented in the new release by a model for hydrogen peroxide formation in the catalyst layer and a model describing platinum band formation in the membrane. When dissolved, platinum ions diffuse from the catalyst on the cathode side into the membrane and come into contact with hydrogen originating from the anode side. The cations are reduced and form a crystallite platinum band, with the catalytic activity of the platinum band promoting the oxidation of hydrogen, the formation of water and electrical potential. In addition, hydrogen peroxide diffuses into the membrane, where its spatial concentration distribution can be interpreted as precursor for further radical formation and ionomer degradation. This implementation also gives you maximum access to the model parameters with their default values based on literature data.

Joule-Thomson Effect

The Joule-Thomson effect describes the fact that real gases change temperature when being compressed or expanded at isenthalpic conditions. This effect is specific to different gases and the heating/cooling depends on the applied pressure and temperature level. Hydrogen compressed at atmospheric pressure and 100K heats up while it cools down at 300K. While the Joule-Thomson effect can be neglected for air at atmospheric or moderate pressure levels, it must be taken into account to correctly describe the compression/expansion of hydrogen when filling / emptying high pressure gas tanks. CRUISE M 2021 R2 offers an enhanced gas property treatment accounting for the Joule-Thomson effect for the species hydrogen, methane, oxygen, nitrogen, etc. The real-gas properties are derived following the state equation by Peng-Robinson with the data compared to NIST REFPROP database.


Fuel Cell 3D Multiphysics Analysis

Platinum Particle Degradation Effects

With AVL FIRE™ M 2021 R2 we now offer you models for platinum dissolution and redeposition. This includes Ostwald Ripening, i.e. the effect of platinum dissolution on particle size, as well as for particle detachment and agglomeration. In addition, a particle size distribution (PSD) is introduced for the catalyst particles that changes due to degradation effects. The newly added degradation models are based on an extended version of the carbon corrosion, carbon oxidation and platinum oxidation models and can be used in steady state and transient simulation modes. The new degradation models allow you to analyze in detail effects such as catalyst layer and membrane thinning, reduction of exchange current density, increase of diffusion resistance in the ionomer film and the changes of the local current and heat sources.

Membrane Humidifier

Water management in low temperature PEM fuel cells is one of the most important factors in avoiding performance degradation and improving cell reliability. For external humidification, the preferred technology is a membrane humidifier since there are no moving parts and no additional power supply is required. Membrane humidifiers use the properties of ionomer membranes to transfer heat and water from the exhaust gas to the fresh gas. The latest version of FIRE M offers you the possibility to simulate such membrane humidifiers in both tubular and planar design.

Figure 2: Membrane humidifier efficiency assessment

Water Separator

Liquid water in the gas media supply paths of PEM fuel cell systems can negatively impact overall performance and significantly affect the cathode air compressor and other BoP components. FIRE M 2021 R2 gives you all required advanced dispersed multiphase capabilities including a coupled thin liquid film model. This enables you detailed analysis and evaluation of water separation efficiency and pressure drop minimization in any complex water separator configurations connected to the fuel cell system.

Figure 3: Water separator pressure loss and droplet separation optimization

Workflow Automation

An automated workflow for the simulation of a PEM fuel cell stack or even a single cell is provided to you by the current release of FIRE M. Starting from the CAD data, you are guided through the complete setup of the 3D multi-physics simulation tasks. Based on best practice, mesh settings are automatically set and can be further customized at your request. In addition, the complete simulation solver and physical model settings are initialized and the individual domains are set up based on predefined data sets. Finally, you can have an automatic report generated.