More efficient vehicle energy management

CFD simulation of vehicle cooling

Enacted and pending environmental policy encourages automotive companies to focus on producing cleaner and safer vehicles. This regulatory pressure simultaneously accelerates competition; companies once devoted to raw horsepower now need to consider the energy efficiency of the vehicles they produce. Market shifts toward connected vehicles and urbanization are also changing the nature of vehicle ownership. Taking these trends into account, it is apparent more thought is needed to produce drivable and comfortable vehicles that maximize efficiency and safety. Achieving this goal requires optimizing vast and often conflicting priorities, making physical testing of all vehicle variations neither economically nor practically viable.

An integrated approach

Implementing an integrated and simulation-driven development process is the best way to meet these industry shifts to produce vehicles that meet all these customer expectations. Developing the comprehensive digital twin of a vehicle and its subsystems enables designers to virtually define the architecture of a vehicle at an early stage of development. It is now possible to reach the optimal balance between performance and energy efficiency targets and limit the number of time-consuming, expensive physical prototypes.  By enabling the digital exploration of various vehicle architectures and configurations, automotive manufacturers can find the best balance between conflicting requirements.

With the digital twin and simulation, engineers can explore, design, analyze and improve vehicle energy management (VEM) and fuel efficiency across the entire vehicle design.  This includes multi-attribute performance engineering of mechatronic systems over different phases of development, from requirements capturing to detailed engineering and validation.

Powertrain design

Internal combustion engines (ICE) enabled the rise of cars in the transportation sector. While they are losing market share to hybrids and all-electric vehicles (EV), the internal combustion engine will remain important for the next few decades. These engines will need optimizations like fine-tuning air-paths and exhaust after-treatments with computational fluid dynamics (CFD) simulation to meet environmental regulations to meet standards for real-driving emissions (RDE) and worldwide harmonized light vehicles test procedure (WLTP).

Vehicle electrification and hybridization

All-electrics and hybrids will also require improvements that are best achieved using the comprehensive digital twin. Creating a new vehicle platform requires rigorous testing and validation to be safe and reliable on the road. Virtual testing reduces not just material cost of development, but the time spent assessing possible, alternative approaches. For example, battery packs or fuel cells can easily be sized to fit in the required platform, and cooling systems for these energy stores can use simulation to improve and optimize range and energy consumption.

Vehicle heat protection

Though most vehicles will never experience the high temperatures of Death Valley, California or the extreme lows of Antarctica, components should still work at severe operating conditions. Knowing how these conditions effect batteries and motors early in the development process is critical to understanding the performance of these components. System analysis can help determine how much cooling air, or what kind of coolant system, is needed to reach efficiency requirements. This testing needs to be done for thousands of components with variation in material properties and critical operating conditions. Proactively and virtually stressing these components using simulation early in the design cycle, makes it more affordable to devise ways to improve component reliability.

CFD simulation can even be used to investigate long-term thermal transient conditions of both solids and fluids in the vehicle to understand the thermal soak condition. That means fewer physical tests, reducing development time and cost. The extra information gleaned from early CFD simulation can be further utilized to direct airflow to critical areas or understand where to add additional heat shielding in the design.

Cabin, driver and thermal comfort

Moving inside the vehicle, thermals are just as important to a great passenger experience as they are in the engine bay or in the battery packs. A range of analysis capabilities enable engineers to study in detail the behavior of the entire system according to heating/cooling strategies and drive cycles in specific operating conditions. For example, a simplified cabin can be used to help provide improved control logic in the systems model. Later in development this model can be extended with embedded CFD to build and run a CFD model to determine passenger comfort level. The insight gained can then be used to position heating or cooling vents to meet regulations on defogging and deicing of mirrors and the windshield. This type of simulation is critical for EVs and high efficiency vehicles. Since there is not enough waste heat from the engine to power defogging and deicing systems, the vehicle must shed usable range to make up the difference.

CFD simulation of car exterior

External Aerodynamics

To regain some of the range lost to passenger comfort, aerodynamic optimization has taken a vital role in vehicle efficiency. Air resistance is the largest energy sink when travelling at highway speeds. Minimizing air resistance means reducing flow impediments, but some of that air needs to flow through the vehicle to cool internal components. Balancing these competing requirements is why using a comprehensive digital twin and simulating early in development is instrumental in creating an efficient vehicle, electric or otherwise.

Balancing performance attributes

Every engineering department involved with creating a vehicle optimizes their systems to meet their requirements, but a car or truck is not a collection of systems, it is a system of systems. The overarching goal is to deliver a cohesive product that delivers a balance of performance and energy management efficiency. The nature and extent of this tuning exercise is largely dependent on customer requirements and preferences as well as emissions regulations.

Adopting an engineering process that incorporates a comprehensive digital twin and advanced simulation throughout the design process enables designers to efficiently find the optimal approach for the overall vehicle energy management. The Siemens Simcenter, part of the Xcelerator portfolio, enables designers to find the right architectural balance for their vehicle platform.

For specifics on how Siemens Simcenter, and the Xcelerator portfolio, can effectively balance competing requirements for EVs and even ICEs, check out the Simcenter Portfolio Factsheet.

Leave a Reply