| 1. |
- Marklund, Ture Jesper, 1970, et al.
(författare)
-
Aerodynamics of passenger vehicles - bluff bodies
- 2012
-
Ingår i: The Vehicle Component. - 1652-862X. ; 2012:1
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Vehicle manufacturers are today struggling to develop more energy efficient vehicles that will meet future emissions targets of CO2 (Carbon Dioxide). To do so it is essential to improve both efficiency of driveline and reduce resistance forces of all kind. The aerodynamic drag force is the single biggest resistance force for a passenger car to overcome at highway speeds and it is a significant part of the total resistance forces that the vehicle has to overcome in average use, city and highway driving. Since a reduction in fuel consumption directly will lead to a reduction of CO2 the best way is to reduce the energy required for propulsion of the system. Aerodynamic drag force can be divided into two parts, pressure and friction. Pressure forces on the exterior body of a passenger car dominate the total drag force. A rule of thumb says that 80-90% of the aerodynamics drag forces of a passenger car are pressure forces and the rest is friction. For a finite wing for instance we will have the opposite, about 95% friction and 5% pressure forces. When the pressure forces are the dominating part of the aerodynamic drag we use to call the body bluff, and if the friction forces are dominating we call it a streamlined body. This then, classifies a passenger car aerodynamically as a bluff body. The biggest pressure forces are associated to wake formations at the rear end of a bluff body.
|
|
| 2. |
- Marklund, Ture Jesper, 1970, et al.
(författare)
-
Fordonsaerodynamik - trubbig kropp
- 2012
-
Ingår i: Fordonskomponenten. - 1652-862X. ; 2012:1, s. 20-23
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Fordonstillverkare lägger idag ned mycket utvecklingsarbete på att skapa mer energieffektiva fordon som möter framtida CO2 (koldioxid) krav. För att klara detta krävs både förbättring av drivlinor och minimering av motståndskrafter. Det aerodynamiska motståndet är det särklass största motståndet, i motorvägsfart, för ett passagerarfordon och det står för en betydande del av motståndskrafterna som måste övervinnas vid en normal användning, stads och landsvägskörning. Eftersom en minskning av motståndet innebär en minskad energiåtgång för framdrivningen av fordonet, blir detta en direkt minskning av bränsleförbrukningen. Det aerodynamiska motståndet kan delas upp i två delar, friktion och tryckkrafter. Tryckkrafterna är de dominerande krafterna för ett passagerarfordon. Man brukar säga att 80-90% av det aerodynamiska motståndet är tryckkrafter och resten är friktion. För en vingprofil är 95% friktionskrafter och resten tryck. När friktionskrafterna är de dominerande kallar vi kroppen strömlinjeformad och när tryckkrafterna dominerar kallar vi den trubbig. Ett passagerarfordon klassas vanligen som en trubbig kropp. De största tryckkrafterna kommer från vaken, vid bakdelen på en trubbig kropp.
|
|
| 3. |
- Marklund, Ture Jesper, 1970, et al.
(författare)
-
Influence of a Diffuser to the Wake Flow of a Passenger Car
- 2012
-
Ingår i: American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM. - 0888-8116. - 9780791844755 ; 1:PARTS A AND B, s. 53-62
-
Konferensbidrag (refereegranskat)abstract
- To achieve more energy efficient transportation we have to reduce losses and resistance forces all over the vehicle. Aerodynamic drag is one of the primary resistance forces a passenger vehicle has to overcome and the force increases exponentially with increased speed. The under-body and rear-end geometry of a passenger car is a significant contributor to the overall aerodynamic drag and the shape of it is normally a compromise between styling, cost and other properties. To reduce the aerodynamic drag it is very important to have a good pressure recovery at the rear-end; to end up with a base pressure as high as possible. It is not necessarily the case that an optimized lower part of the rear-end for a square-back car has the same performance as a notch-back or fast-back car.This work investigates the rear-end flow and aerodynamic performance of a sedan and wagon car with varying rear-end under-body design parameters. The study is a numerical analysis using a standard CFD approach commonly used in the automotive industry. A parameter study of under-body covers with varying rear angles, making the rear floor act like a diffuser. The function of the rear floor working as a diffuser is similar regardless of the upper geometry, but its function as a drag reduction device can be very different. Results from this study show a potential to reduce aerodynamic drag of the sedan car approximately 10%, with the best diffuser angle and cover plates over the floor. The best drag reduction for the wagon car was 2-3 % and the optimum was at a smaller diffuser angle. Flow analysis of the wake shows how important it is the wake is balanced.
|
|
