Evaluation of Novel Ventilation Concepts for Level 4 Vehicle Cabins Using an Optically Tracked 3D Velocity Probe

Abstract

Highly automated (SAE Level 4) vehicles enable new, more relaxed seating postures and non-driving related activities, which challenge conventional air distribution concepts for maintaining local thermal comfort and energy-efficient HVAC operation in compact cabins. This study presents an experimental evaluation of novel ventilation concepts for a generic Level 4 vehicle cabin based on volumetric flow measurements using an optically tracked three-dimensional ultrasonic velocity probe (ProCap system). Experiments are conducted in a full-scale vehicle mock-up equipped with a configurable HVAC system. Three air distribution modes are implemented: (i) a baseline concept with globally distributed mixing outlets, (ii) a body-zone ventilation concept with supply jets targeted at thermally sensitive regions such as feet, legs, torso and hands, and (iii) an air-envelope concept, in which supply air is guided around the occupant to form a convective layer with minimal direct impingement. The ultrasonic probe was moved freely within a pre-defined measurement volume enclosing the occupant, while an optical tracking system provides accurate probe positioning and orientation, enabling the reconstruction of three-dimensional velocity fields. From the measured three-component velocities and air temperatures, spatially resolved flow quantities were derived to characterise the large-scale flow patterns and the near-body microclimate for each ventilation concept. The measurements reveal distinct air flow characteristics, recirculation structures and velocity distributions, which are linked to differences in local exposure to drafts and mixing of supply air with the cabin air. The results show how targeted, body-zone oriented air distribution and air-envelope supply can be used to shape the occupant microclimate in automated vehicles and provide input data for subsequent thermal comfort and energy performance assessments. The findings are relevant for the design of future HVAC systems in mobile indoor environments such as automated vehicles and shuttles.