With the global push toward sustainability, electric vehicle manufacturers are working to meet consumer demands by extending the range, increasing the power, and reducing the charging times of electric vehicles. To accomplish these goals, significant research and development efforts are being devoted to battery technology. Lithium-ion (Li-ion) batteries are the most commonly used power source for today's electric vehicles. They offer a relatively high energy density and long lifetime compared to alternatives such as nickelmetal hydride (NiMH) batteries, which are often used in hybrid vehicles. Li-ion batteries can utilize various cathodes chemistries for different commercial applications, differing primarily in their chemical composition and resulting electrochemical properties. Lithium cobalt oxide (LCO) and nickel-rich nickel manganese cobalt (NMC) batteries are favored for their high energy densities, but this comes with an increase in cost due to critical minerals (cobalt) and poor stability with high nickel content. Lithium iron phosphate (LFP) and manganese-based cathodes (LMO) offer superior thermal stability, being less prone to thermal runaway, but offer low energy density.

With the push toward net-zero emissions, renewable technologies are poised to play a significant role in the future of the transportation and energy sectors. While multiple technologies have the potential to help move us toward our goal, few show as much promise as hydrogen. Hydrogen can help address issues related to energy security, pollution, emissions reduction, and sustainability across many industrial sectors, making it a key focus of research and development efforts. Additionally, there is a growing interest in green hydrogen production and storage technologies, which could position hydrogen as one of the primary fuel sources for both industrial processes and transportation.

CONVERGE CFD software was developed to simulate compressible fluid mechanics inside complex moving geometries with intermittent blockage between sub-regions, where energy is exchanged between the moving geometry and fluid dynamical processes. With this framework, CONVERGE is well suited to model positive-displacement pumps and compressors. Such a pump poses substantial setup and modeling challenges in many simulation software suites, whose developers might consider such a physical system somewhat esoteric. In contrast, CONVERGE is specifically designed to handle the challenges that are posed when modeling flows in pumps. This white paper will discuss three positive displacement pump types, each highlighting a single case setup or physical modeling challenge as well as the solution approach adopted by CONVERGE. The first is a reciprocating piston pump with spring-loaded valves, which requires attention to fluid-structure interaction (FSI). The second is a gerotor pump, with attendant surface-to-surface sealing modeling. The third case is a vane pump, which may be prone to cavitation. Finally, there is a brief discussion of a representative centrifugal dynamic pump.

One of the primary design drivers in the initial development of CONVERGE CFD software was the ability to easily accommodate complex moving geometries. These feature prominently in internal combustion engines, where both piston motion and valve motion must be accounted for. However, engines are by no means unique in this unavoidable complexity. Many systems of engineering interest involve fluid flow around complex geometries that are moving with respect to one another. Often, these problems are so elaborate and sophisticated that they do not seem amenable to traditional computational analysis. Consider, as a case study, an automotive paint bake oven. The unibody structure of a modern automobile consists of a number of sheet metal stampings and panels welded together in the factory. At this stage of the production process, this unit is commonly referred to as a body in white (BIW). The BIW is sprayed with the base coat of paint, which must be carefully cured for durability. In practice, the painted BIW traverses a large paint bake oven, where it is subjected to hot impinging air jets and radiant heaters. The carefully controlled thermal environment ensures a durable coat of paint.

The fluid dynamics of positive-displacement compressors give rise to many phenomena that affect the efficiency of these machines, such as leakage flows, viscous losses, and pressure pulsations. Three-dimensional computational fluid dynamics (CFD) models can help elucidate these phenomena by providing a complete description of the relevant flow fields in both space and time. The primary challenge in applying CFD to compressors is the complexity of their geometries. These devices come in many shapes and sizes and typically have multiple moving parts, such as intake and discharge valves and the mechanical linkage that compresses the fluid. CONVERGE CFD software offers unique autonomous meshing capabilities that make it easy to simulate this complex motion with minimal setup time, even for the most novel geometries. CONVERGE also includes options for modeling fluid-structure interaction, conjugate heat transfer, and other physical processes that can be critical to compressor flows. Recent studies have established CONVERGE as a powerful tool for the design and analysis of these devices, capable of producing accurate results at a reasonable computational cost.

To ensure the longevity of internal combustion engines in the adverse conditions to which they are subjected, engine designers must carefully consider the thermal and structural stresses that affect the critical components of the device. Because of the combustion process that occurs in the engine cylinder, it is critical to study the thermal stresses that exist in the vicinity of the cylinder. Analyzing the temperature distribution in the solid cylinder head is an important part of determining the durability of the engine. Predicting such a temperature distribution during the design phase helps engineers create a reliable and efficient product. While experimental test devices provide useful results for the temperature distribution in the solid, computational fluid dynamics (CFD) offers the ability to accurately calculate a pointwise temperature distribution in these solid metal components with higher spatial resolution.

Although the SAGE detailed chemistry solver has demonstrated success in a host of gas turbine, internal combustion engine, and other applications, it has been questioned for not employing a model to account for turbulence-chemistry interaction (TCI). In this study, we demonstrate that CONVERGE CFD (with LES, detailed chemistry, and sufficient grid resolution) can account for turbulence without explicitly assigning a sub-grid model to account for those interactions. We simulate the Sandia Flame D case, which is a canonical turbulent partially premixed flame. Because LES and detailed chemistry can be computationally expensive, these CONVERGE simulations include Adaptive Mesh Refinement (AMR) and adaptive zoning as acceleration strategies.

When using computational fluid dynamics (CFD) to solve the Navier-Stokes equations, the act of discretizing the equations necessarily replaces terms in the equations with approximations. These approximations add error to the solution. Some of this error can be represented as an additional diffusive term, which is referred to in the literature as "numerical diffusion," "diffusive error," or "numerical viscosity." Whatever your preferred terminology, this is a nonphysical artifact of CFD that can pollute your results. CONVERGE has several features to minimize the effects of numerical viscosity and improve solution quality.