Power Requirements of A Vehicle P M V Subbarao Professor Mechanical Engineering Department Match the Horse to theCart ….

Animal Driven Vehicles 2

The Powering Torque for a vehicle is: The speed of the vehicle in km/h is: r wheel = Wheel Rolling Radius (meters) Ideal capacity of Powering Engine: Cycle Work to be done by an Engine Directly Powering the Vehicle Ideal cycle work of to be provided by A Powering Engine:

Engine Practical Power Output & Torque at Maximum Fuel Consumption 4

Need for Gear Box 5

Modern Cars are not Directly Driven!?!?! 6

High Way Driving Cycle

Indian Urban Driving Cycle

Comprehensive Test Driving Cycles 9

Forces To be Overcome by an Automobile

Resistance Forces on A Vehicle The major components of the resisting forces to motion are comprised of : Acceleration forces (F accel = ma & I  forces) Aerodynamic loads (F aero ) Gradeability requirements (F grade ) Chassis losses (F roll resist ).

Aerodynamic Force : Flow Past A Bluff Body Composed of: 1.Turbulent air flow around vehicle body (85%) 2.Friction of air over vehicle body (12%) 3.Vehicle component resistance, from radiators and air vents (3%)

Aerodynamic Resistance on Vehicle Dynamic Pressure: Drag Force: Aero Power

C d = coefficient of drag  = air density  1.2 kg/m 3 A = projected frontal area (m 2 ) V = vehicle velocity (m/sec) V 0 = head wind velocity

Purpose, Shape & Design Drag

Shape & Components of Drag

Some examples of C d : The typical modern automobile achieves a drag coefficient of between 0.30 and SUVs, with their flatter shapes, typically achieve a C d of 0.35–0.45. Notably, certain cars can achieve figures of , although sometimes designers deliberately increase drag in order to reduce lift. at least a typical truck Hummer H2, Citroën 2CV over Dodge Viper Toyota Truck,

Lamborghini Countach, Triumph Spitfire Mk IV, Plymouth Duster, Dodge Durango, Triumph Spitfire, Volkswagen Beetle Mazda Miata, Ford Capri Mk III, Ferrari F50, Eagle Talon, mid-1990s Citroën DS, Ferrari Testarossa, Opel GT, Honda Civic, Citroën CX, 1974 (the car was named after the term for drag coefficient) NSU Ro 80, 1967

Ford Sierra, Ferrari F40, Chevrolet Caprice, Chevrolet Corvette Z06, Chevrolet Camaro, Dodge Charger, Audi A3, Subaru Impreza WRX STi, Mazda RX-7 FC3C, Citroen SM, Volkswagen GTI Mk V, 2006 ( with ground effects) Toyota Celica, Citroën AX, Citroën GS, Eagle Vision Ford Falcon, Mazda RX-7 FC3S, Renault 25, Saab Sonett III, Audi 100, BMW E90, Porsche 996, Saab 92, 1947

General Motors EV1, Alfa Romeo BAT Concept, Dodge Intrepid ESX Concept, Mercedes-Benz "Bionic Car" Concept, 2005 ([2] mercedes_bionic.htm) (based on the boxfish) Daihatsu UFEIII Concept, General Motors Precept Concept, Fiat Turbina Concept, Ford Probe V prototype, 1985

Transient aerodynamic forces on overtaking road vehicles

Effect of relative velocity on the variation in the aerodynamic Drag coefficient 24