Trucks, buses, and coaches are responsible for a quarter of CO2 emissions from road transport and for 6% of total emissions in the EU. Despite some improvements in the efficiency in recent years, these emissions are still rising, mainly due to increasing road freight traffic. The first-ever EU CO2 emission standard for heavy-duty vehicles sets strict targets for reducing the average emissions from newly produced trucks for 2025 and 2030. From 2025, manufacturers will have to meet the targets set for the fleet-wide average CO2 emissions. The targets are a 15% reduction from 2025 and 30% reduction from 2030 as compared to the EU average in a reference period of 2019--2020.
The new EU standards put the electrification of AB Volvo’s trucks in first place. The cooling system of an electrified truck (EV, either electrical or hybrid) is very different from a cooling system of a traditional truck. There is a need for battery cooling, cooling of a densely packed underhood hybrid powertrain, cooling of brakes at downhill operation for heavy trucks, and extra cooling for fast-charging batteries. Other major differences are that the cooling system in an EV is driven by electrical motors and that its silent operation becomes much more important. In the absence of any combustion engine noise, the fan noise becomes more audible and undesired, especially as the fans occasionally are switched on and off.
The heat rejection is highly dependent on the airflow created by the fan applied directly or through heat exchangers and radiators. Since the specific heat and thermal conductivity for the air are much lower than for a coolant (1/10 and 1/4 respectively), the airside is the bottleneck in the heat transfer process in the radiator. Hence, optimized airflow is crucial for the cooling performance, and the fan is the limiting factor and a key component for meeting the requirements. There is substantial potential for energy saving in the cooling system of an EV. A conventional electrical fan has a peak efficiency of about 45% while an improvement to 60-65% is feasible, which would give a significant energy saving, higher performance, and less heat generated by the fan. Assuming that the electrical fans consume about 5% of the truck’s total energy, such savings would correspond to 50 to 300 GWh annually.
Two students looking for a 60-credit master thesis. We are expecting interest in, automotive industry and/or turbomachinery. Knowledge of basic fluid dynamics is compulsory. Knowledge of Matlab is highly desirable. The working language is English.
Description of thesis work
In this thesis project, using testing and simulations, a correlation between the fan aerodynamics, performance, and efficiency will be studied and quantified for a standalone fan and for a fan in a modeled engine compartment. The energy-saving will be quantified. Guidelines for efficient high-performance electrical fans and multi-fans will be extracted from the studies. The work will be performed at Chalmers’ Laboratory of Fluids and Thermal Sciences in cooperation with AB Volvo. The fan efficiency and aerodynamic tests will be performed. The inlet and outlet flow fields will be measured with aerodynamic probes and by Particle Image Velocimetry (PIV). The test results will be used for validation of CFD simulations and for improvement of simulation methodology for generic electrical fan applications. The CFD simulations are currently performed by a PhD student and the thesis workers are welcome to participate if interested. The experimental test rig is currently ready for operation and equipped with one of the tested fans. During the project, several fan configurations will be tested, including a distributed multi-fan system, and it is expected that the thesis workers will participate in the implementation of these configurations.
The thesis students will learn:
- EV cooling and difference between the EV and traditional vehicle cooling
- key issues with the cooling system and fan design
- fan aerodynamics and basics of turbomachinery
- experimental methods for turbomachinery research
- how to compare and critically analyze data from CFD and experiments.
Thesis Level: Master and/or Bachelor
Starting date: January 2022
Number of students: 2
Supervisor and project leader at AB Volvo
Prof. Sassan Etemad, 076-553-3722
Examiner and supervisor at Chalmers
Prof. Valery Chernoray, 073-034-6360
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