Automobiles are largely composed of components that directly or indirectly possess relationship with heat transfer. Although heat is essentially required to churn out power from the engine, rest of the components are being incorporated to accommodate or transfer the generated heat, once it completes the job of producing necessary power.
The efficiency of the automobile is largely dependent on successful utilization as well as evacuation of the heat from different components apart from the engine. Once the heat becomes uncontrollable, the components can get damaged and affect the overall performance. An overheated engine would eventually seize and stop generating power, requiring an effective cooling system. Cooling system on the other hand relies on effectiveness of the coolant and radiator.
Heat is also a problem for the braking system; excessive formation of hot-spots due to braking can damage the brake pads and the rotor. Turbochargers on the other hand rely on the exhaust gases that are excessively hot, which can damage turbine blades due to thermal stresses. Similar effect of high temperature gases can be observed in the exhaust piping systems also.
To combat this heat from different regions in an automobile, CFD proves to be an extremely useful tool. As it is famously said, “A picture is worth a thousand words”, CFD allows engineers to visualize the effects more comprehensively and understand the fluid flow behavior more accurately.
Here’s how CFD can be helpful in combating heat in vehicles:
Engine cooling mainly relies on the cooling capacity of the radiator; which is essentially a heat exchanger involving the interaction of air and coolant flow. The larger the surface area available for the air, the greater the heat transfer rates will be. Using CFD, conjugate heat transfer analysis can successfully provide detailed insights on how the air flow is interacting with the radiator fins and measures the effectiveness of the HE. Regions restricting the fluid flow or allowing concentration of heat can be figured out through simulation and further optimization can be performed.
The exhaust gases driving the turbine also impacts the blade performance, as high temperature gases can eventually develop thermal stresses and produce cracks or deformation. The blade profiles are of prime interest in the turbo design, which can be successfully evaluated using CFD. Pressure drop analysis will provide details about the flow patterns inside the turbocharger and will help in identifying regions that lead to a drop in pressure. Apart from pressure drop, conjugate heat transfer will supply information on how the blades and casing are interacting with high temperature gases. It will identify hot regions in the geometry, which can be modified to improve the performance.
Brakes are bound to generate heat as they rely on the principle of friction. However, excessive heat generation will eventually lead to the failure of braking system components, and may put the vehicle safety at stake. The design of the brake rotors must accommodate easy flow of air, in order to promote convective heat transfer. In practicality, it is quite complex and costly to measure the heat transfer rate from the braking systems. On the other hand, CFD simulations are cost-effective and provide better insights on what’s happening in and around the braking system of the vehicle.
The use of CFD can also be extended to study the exhaust system effectively. The piping system utilized to evacuate the exhaust gases are bound to develop thermal stresses, if their placements are not well-designed. Studying the flow patterns of the exhaust gases coming out of the engine exhaust port and exiting from the tail pipe, can help in identifying the regions requiring design modifications.