Experimental and Numerical Analysis of Light-Emitting Diode (LED) Headlamp

Light-emitting diodes (LEDs) have become the preferred light source for automotive headlamps due to their excellent durability, fast response times, higher efficiency, and superior optical performance compared to traditional halogen bulbs. However, their high power output, compact design, and positioning within the headlamp assembly pose significant thermal management challenges. Prolonged operation leads to a rise in LED temperature, resulting in reduced light output—a phenomenon known as LED derating. This decrease in light output can compromise visibility, posing safety risks to drivers and road users. Additionally, the proximity of the headlamp to the vehicle's engine further elevates the surrounding temperature, worsening the LED derating. This thesis investigates the thermal and optical performance of LED headlamp under various ambient conditions and LED current control methods, including convective fan cooling and forced current derating. Experimental temperature measurements at 14 locations, along with luminous flux measurements of a headlamp model, were conducted at the Stellantis Automotive Research and Development Center (ARDC). In parallel, a computational fluid dynamics (CFD) model of a simplified LED headlamp assembly was analyzed to evaluate temperature distributions on the LEDs and the detailed flow patterns within the headlamp. The CFD results align within ±10% of the quasi-steady temperature measurements obtained for forced convection cases. The CFD analysis reveals that the flow around the LED heatsinks is significantly influenced by the position of the cooling fan. Furthermore, internal components within the headlamp obstruct the flow, creating a stagnation zone near the second LED unit. This stagnation zone results in elevated temperature distributions, indicating a potential hotspot in the system that could impact performance and reliability.