CAE from Powertrain to Radar Systems
A major update to the flagship CAE/FEA/CFD/simulation software
from Ansys responds to the variety of new engineering in automotive.
The challenges facing automotive engineers today include improving fuel economy, reducing emissions, managing electronics and software complexity, developing autonomous vehicles and maintaining high product safety, quality and reliability. “New thinking is always coming up,” says Sandeep Sovani, director, global automotive industry, for Ansys (ansys.com), “and there is a lot of new software that needs to be developed to enable that engineering.”
One of those software packages is the computer-aided engineering simulation system from Ansys. The latest version, Ansys 17.0, has a plethora of new modules, features and enhancements that, according to company officials, together deliver “10X improvements to product development productivity, insight and performance.” Here are some of the new items.
Meshing is everything
“Meshing is not a simple, straight-line process, admits Sovani. “It’s like flying a big aircraft, going from Destination A to Destination B. Different pilots like taking different routes.” Solution Adaptive Meshing (SAM), a new capability for Ansys Forté CFD, helps control mesh refinement by balancing mesh size with mesh resolution and accuracy. SAM basically allows deep mesh refinement only where and when needed. Those conditions are based on primitive solution variables (such as velocity, temperature, pressure and thermal kinetic energies), or based on absolute-value range, percentile range, or standard deviations. SAM yields excellent accuracy while maintaining fast simulation speed.
Keeping up with new flames
Fuel is a complicated compound made up of a blend of several chemical components. These components behave differently, particularly their laminar flame speeds. The conventional approach to simulating fuels averaged all flame speeds for the individual fuel components. This approach “leads to inaccuracies and coarser solutions,” says Sovani. Now Forté includes a library generator for the laminar flame speeds of more than 50 fuel components. These flame speeds are pre-calculated for the broadest possible range of engine conditions (such as varying equivalence ratio, temperature and pressure).
The library automatically accounts for the interdependencies between fuel components that might affect the laminar flame speed. This automation replaces the alternative: using power-law correlations that assume independent factors (namely, pressure, equivalence ratio, temperature, dilution and fuel structure). In practice, this alternative does not accurately account for the differences in flame-speed across different exhaust gas recirculation techniques.
Boosting fuel cell design
Modeling fuel cell technology gets particular attention in Ansys Fluent 17. A new module details the reactions within a proton exchange (or polymer electrolyte) membrane fuel cell (PEMFC). Up to now, Fluent capably modeled the catalyst layers around the membrane (gas diffusion layer, gas channel, collectors, and cooling channels), with the gas diffusion layer directly touching the catalyst layer. Now Fluent can model the anode and cathode micro porous layers (MPL) as separate layers (i.e., with different properties compared to the gas diffusion layers).
Another enhancement to the PEM module involves water. Explains Sovani, “As the hydrogen and oxygen combine in the fuel cell, water is formed as a byproduct. Managing that water is important. That’s one of the biggest challenges in fuel cell development.” The PEM module now includes three new water management models: liquid water transport in porous media (a new equation for the porous media solves for capillary pressure equation in the membrane in the catalyst), liquid water transport in the gas channels (the result yields meaningful values to model pressure drop through the viscous resistance), and dissolved phase water transport in the membrane and catalyst assembly (a rigorous transport equation treats the dissolved water as a third phase in the membrane electrode assembly, MEA).
Expanding system simulations
Ansys Simplorer is an analysis tool for system-level simulations. The latest version includes native Modelica support, which enables Simplorer to import Modelica models, the Modelica standard library, and lightweight Modelica capabilities. This addition increases the functionality of system models within Simplorer. Think about simulating brake systems, which include hydraulics, pneumatics and electronics. That entire simulation can now be done in one place: Simplorer. The Simplorer power systems library also now includes additional basic elements, sources and transforms (converters, signal generators, frequency-dependent elements).
Another vote for 26262
“Software has become a safety critical aspect in many systems, especially cars,” says Sovani. “All this emergent software is potential for catastrophic failures. The automotive industry has organically grown to develop this software. They need a better process to develop this software in a safety critical way.”
Enter the Ansys Safety Critical Application Development Environment (SCADE) tools for designing the embedded software in the microprocessor-based devices and controllers scattered throughout today’s vehicles. The suite encompasses requirements management, model-based design, simulation, verification, qualifiable/certified code generation, interoperability with other development tools and platforms, and application lifecycle management. SCADE has been predominantly used in aerospace, according to Sovani, but it’s just as applicable to automotive, especially now that SCADE is compliant with ISO-26262 (“Road vehicles – Functional safety”). This compliance, says Sovani, “means that embedded code rendered by SCADE is automatically prequalified to ISO-26262, and therefore, does not have to go through as much rigorous testing. Development testing is reduced.”
Also new in SCADE is a module for testing human-machine interfaces (HMI). SCADE Display, continues Sovani, “reduces the effort required for testing HMI applications by enabling model testing to be performed earlier in the development cycle, thus saving expensive design reworks, and automating test execution and results analysis.”
A new wave in radar
“Radars are typically delivered by radar suppliers,” says Sovani, but for vehicles, the integration is still up to the automakers. Integration goes beyond just slapping in a finished module and wiring it to the in-vehicle electronics. Continues Sovani, “Radar behaves differently in free space than when it’s installed on the fascia of a vehicle. It’s also important to figure how radar will perform in various traffic and environmental conditions.”
Sovani says that automotive radar is both a geometrically complex and electromagnetically large problem. Through its acquisition of Delcross Technologies last year, Ansys is able to simulate radar performance using a hybrid approach between the finite element method (FEM; full-wave) and the shooting and bouncing ray analysis (SBR; asymptotic) method. FEM looks at the data elements in the tens of wavelengths, such as that from potentially interfering on-board electronics and mobile devices in the passenger cabin. When the radar is installed in the fascia of a car, FEM and SBR together help in analyzing the geometrically large problem that covers hundreds of wavelengths. Last, SBR helps in understanding radar performance when a vehicle is moving through traffic, passing other vehicles, trees and buildings—geometrically huge environments with thousands of wavelengths.
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