Study of oil flow in a simplified Volvo truck gearbox - Chalmers

Study of oil flow in a simplified Volvo truck gearbox

Trucks, buses and coaches are responsible for about a quarter of CO2 emissions from road
transport in the EU and for 6% of total EU emissions. Despite some improvements in fuel
consumption efficiency in recent years, these emissions are still rising, mainly due to
increasing road freight traffic. The first-ever EU-wide CO2 emission standards for heavy-duty
vehicles, adopted in 2019, set targets for reducing the average emissions from new trucks
for 2025 and 2030. From 2025 on, manufacturers will have to meet the targets set for the
fleet-wide average CO2 emissions of their new trucks registered in a given calendar year.
Stricter targets will start applying from 2030 on. The targets are 15% reduction from 2025
and 30% reduction from 2030 expressed as a percentage reduction of emissions compared
to EU average in the reference period from 1 July 2019 to 30 June 2020.

This means that for a truck manufacturer AB Volvo any marginal efficiency gains in every
component are considered beneficial for total reduction of CO2 emissions. Truck
transmission is one of the components where the losses can be decreased. If we look at
truck transmission, losses in the form of churning losses stem from the interaction between
oil and partially immersed rotating gear wheels. It is obvious that reducing the amount of oil
inside the transmission will lower the churning losses. However, the presence of oil inside a
transmission is not solely for lubrication purposes but also for heat dissipation. Excessive
heat on the components greatly impacts their durability and lifetime. Finding a balance
between low loss and high heat dissipation requires further studies of the oil fluid dynamics.
Also, understanding the flow at the boundary layer around the gear wheel is important to
drive inventions and design solutions in this area.

From an industry perspective, the main rig needs are:
   - Being able to verify small gains in power loss reduction
   - Being able to better observe the flow behaviour at high speeds

Left: CFD simulations of oil flow inside a transmission. Right: previous experimental rig for oil flow studies

This work was initiated by AB Volvo and it was proposed to extend the previous work by
Hartono (2019) and to conduct the proposed thesis as an initial step of this continuation.
The main idea of the proposed thesis is to design an improved test rig compared to existing
test rig available at Chalmers. The geometry of the new rig should be able to expand to
represent generic AB Volvo gearbox. As well, losses in the bearings of the gears should be
minimized to reduce their influence on the measured torque. Thus, the bearings should be
replaced by either air-lubricated or magnetic bearings. The torque meter accuracy should be
improved. A circulation system for the oil should be made similarly to that present in an AB
Volvo gearbox. If the oil level uncertainty can be minimized, that is also an important
benefit. The transmission oil circulation system is one important system parameter to study.
Similar to the existing test rig (Hartono 2019), the test section and test oil will have a clear
appearance to ensure good optical access. The rig will be located at Chalmers and material
for the rig will be ordered by Chalmers from external manufacturers. Building of the rig and
construction work will be performed by the student with help from Chalmers personnel.
If possible, in the given time frame the new rig will be manufactured assembled and tested.
Studies of the oil flow may be performed by the students by means of flow visualisation and
torque measurement. Flash photography and high-speed recording may be used to visually
capture the oil flow. The torque loss will be measured by a high-accuracy torque meter for
different oil levels, oils and gear configurations. A study of to evaluate the uncertainty of the
rig is part of the thesis.
The results will be compared with available correlations available in the literature.
Optionally, if desired by the students, CFD simulations on single special cases will be
performed for some of the studied cases.
The thesis students will be employed as students during the thesis time by Volvo and also be
located in the Volvo facility in Lundby, Göteborg.

Prerequisites for the thesis
Interest in automotive industry and general fluid dynamics, interest in construction and
CAD. Optionally interest in CFD.

Application
Follow the link and apply on Volvo Group homepage:
https://xjobs.brassring.com/TGnewUI/Search/Home/Home?partnerid=25079&siteid=5171#jobDetai
ls=705862_5171

Duration
The thesis project will start January 2021 and continue 20 weeks.
Two students, the diploma work gives 30 points/student.

Examiner
Prof. Valery Chernoray, valery.chernoray@chalmers.se, 0730346360

Tutors Volvo
Lars Jacobsson, Global System Responsible, Volvo GTT PE Driveline,
lars.jacobsson@volvo.com 031-322 37 72
Henrik Hagerman, Lead Simulation Engineer, Volvo GTT PE Driveline,
henrik.hagerman@volvo.com, 031-322 61 59

Flow visualizations made by Hartono (2019)

Reference
Hartono E.A. (2019) Experimental Study on Truck Related Power Losses: The Churning
Losses in a Transmission Model and Active Flow Control at an A-pillar of Generic Truck Cabin
Model, PhD thesis, Chalmers University of Technology.