1. Encapsulation of engine bay for active thermal control and lower noise emissions
Abstract:
The project aims to study the effect of encapsulating the engine and transmission in order to reduce noise emissions while energy efficiency will be improved by controlling the temperature fields inside and outside the encapsulation.
Encapsulating the engine bay and gear box of the vehicle gives potential for increased energy efficiency, lower noise emissions as well as reduction of working temperatures for thermo-sensitive components. The lifetime of the components is increased. Furthermore, as the term encapsulation suggests, the engine is separated from the environment and consequently soiling and dusting are reduced. The project belongs to the area of energy-efficient vehicles, which is prioritized within the focal working areas of the Swedish Energy Agency. The project has a high value of innovation for the vehicle industry as the virtual model to be produced interconnects thermodynamic, fluid dynamic and acoustic phenomena, which take place in the vehicle.
Hello,
My name is Blago Minovski. I am a PhD student at Chalmers university of technology. I work on a project called Encapsulation of engine bay for active thermal control and lower noise emissions under the supervision of professor Lennart Löfdahl. The work is a cooperation between Chalmers, Volvo Trucks, Volvo cars and Scania and it is partly financed by the Vehicular Strategic Research and Innovation program.
Blago Minovski
Supervisor: Prof. Lennart Löfdahl
Department of Applied Mechanics
Division of Vehicle Engineering and Autonomous Systems
Start:
End: Fordonsstrategisk Forskning och Innovation 6842 kkr

2. Higher requirements for energy-efficient and quiet vehicles.
Background
Higher requirements for energy-efficient and quiet vehicles.
Demands for shorter lead times implicate the design process in a way that noise levels, coolant and cooling air flows, etc. must be decided already at concept stage.
There is a clear trend towards retaining heat in the engine compartment for as long as possible in order to reduce fuel consumption. At the same time it is becoming increasingly difficult to achieve a quiet and pleasant exterior noise, because a more efficient combustion is usually noisier combustion. Both problems can be solved with clever encapsulation that, at an acceptable cost, cuts CO2 emissions and reduce exterior noise. This is strongly motivated by the increanlgy tough requiremetns for exhaust and noise emissions.
In some specific scenarios, where legistlation currently banns distribution trucks in urban regions during night time the combination of a quiet and fuel efficient vehicle will prove very beneficial, as it will allow the more-quiet truck to operate during night in lower traffic and more-efficient drive-cycle modes. Studies have shown that there is a potential to save up to 15% as a result of driving during lower traffic hours and the thermal effects of the engine encapsulation.
Blago Minovski

3. Engine encapsulation retains heat in the powertrain
Concept
Engine encapsulation retains heat in the powertrain
Increases probability of high initial oil temperature at next engine start
Reduces air-bourne noise
Optimized engine cooling and vehicle thermal management by implementation of active means of temperature and flow control in the engine bay.
How does an encapsulated engine look like?
The picture shows engine mounted encapsulation, which is installed in direct proximity to the motor. There are also other engine encapsulation types.
The benefits of engine encapsulation, as mentioned before, are mainly two: thermal and acoustic.
From acoustic point of view the encapsulating panels stop or reduce the magnitude of the air-borne noise and ideally prevent it from propagting outside the engine bay.
From a thermal point of view the encapsulation retains the engine heat and prevents it, or slow is down from being convected away to the ambient after the engine is swithed off. This increases the probability for a hot oil temperature at following engine start therefore reducing the additional friction losses during the first minutes of engine operation when the oil is cold and thick.
However this brings certain design challenges which originate from the basic principle of encapsulation. Such a challenge can be the local increase of surface tempertures of components due to radiation heat and reduced local convective cooling. This could, for example happen close to the exhaust manifold.
This brings us to the main aim of this research work:
Blago Minovski

4. Cooling system temperatures for continuous drive cycles
Aim
To develop a method and a software toolbox for evaluation of engine encapsulation effectiveness
Cooling system temperatures for continuous drive cycles
Hot spots (caused by radiation)
Prediction of noise emissions
To develop a method and a software toolbox for evaluation and quantification of engine encapsulation effectiveness.
The software will capture the influence of encapsulation on a number of design critical performance factors.
Such a performance factor is the coolant temprature measured during a continuous driving cycle. Needless to say, engine encapsulation hardware influence the total heat balance of the vehicle. It is an important design requirement to account for and be able to simulate these influences on the entire engine instllaiton system and specifically on the cooling system.
Hot spots, the local, surface effects of radiative heat transfer, and noise are also accounted for by this comprehensive tool.
The picture that you see displays temperature dustribution along a cutoff plane located few milimeters in front of the radiator of the truck. Acquired from CFD. This is one small example of the tools and methods used for the analysis.
Blago Minovski

5. Current Status
Developed and validated a detailed 1-D model of the cooling system coupled with engine model that predicts important cooling system parameters with continuous signal input.
A quick presentaiton of the current status of the project.
Until now the main focus was on developing an accurate and physically detailed model of the cooling system, coupled with a predictive engine model with a continuous drivecycle input. This was done by a detailed one dimensional model of the cooling system built in GT-SUITE, that contains simultaneously communicating blocks that represent the engine and the underood.
The plots show comparisons of important performance quantities such as Fan speed and Coolant temperature.
The model is tested and validated for Hamburg-Kassel drive cycle and achieves high levels of consistency between tested and simulated quantities.
However certain modes of system operation could not be effectively captured by the simplified and fast running 1-D models. Therefore it was necessary to upgrade them and improve them by incorporating 3-dimensional methods.
Blago Minovski

6. Current work
Implementation of three-dimentional tools to increase the accuracy of simulation and prediction
Such a 3-dimensional method captures the flow characteristics and velocity and temperature nonuniformities across the surfaces of the heat exchangers, which is vital for the accurate prediction of any simulated parameter in the system.
A large amount of 3D CFD simulations are run at steady state and results are incorporated into the 1-Dimensional model.
Signifficant increase of accuracy has been observed. Furthermore, the previously needed tedious calibration procedure of the 1-D model is considerably rectified and entirely data driven.
Blago Minovski

7. Thermal models of encapsulation structures
Future work
Extend the 1-D model to simulate the engine oil temperature variation after shutdown
Thermal models of encapsulation structures
Propose an engine encapsulation concept with active control and analyze it with the developed tool
Work out radiation and acoustic models and correlate simulation results to test results for the selected concept
The main focus for the near future of the project is to finalize the 1D-3D integration concepts comletely.
As far as the further future perspective of the project is concerned, it will retain its focus on thermal management.
The oil circuit will be included in the complex analysis as well as comprehensive thermal models of the encapsulation itself.
Radiaton effects will also be capstured to a suffucuent level. Acoustic effects will also be accounted for.
Blago Minovski

8. Publications
"Study of Software Integration for Transient Simulation of Future Cooling System for Heavy Truck Application," SAE Technical Paper , 2014, doi: /
“An improved method for transient simulations of cooling systems with non-uniform thermal and flow boundaries” SAE Technical Paper
The research has lead to two publications.
Blago Minovski