Engines Control Power CVHS

Introduction We will be examining several types of engine converters that are commonly used  Many are used in the Transportation sector We call them “Heat Engines” because:  convert thermal energy from fuel to mechanical energy for motion Classifications are based on:  location of combustion, type of combustion, and type of internal motion

Common Classifications IC or ICE combustion is internal combustion directly touches the parts that must be moved example: car engine EC or ECE combustion is external example: boiler (steam engine)

Common Classifications Intermittent Combustion Engine combustion starts and stops many times examples: car engines - gas and diesel Continuous Combustion Engine example: rocket engine Reciprocating Engine classification based on internal part motion examples: gas and diesel engines

Common Classifications Rotary Engines another parts motion classification internal parts have a continuous rotation movement examples: Wankel and Turbine engines Others Classifications Cycles, Cooling Sys, Fuel Sys, Ignition Sys

Heat Engine Parts and Systems Cylinder Block Foundation All other components are attached to it Cylinders internal holes in the block (combustion chambers) Autos: 2, 3, 4, 5, 6, 8,10,12Autos: 3, 4, 6, 8, 12 Cylinder Head houses the valves, ports and spark plugs for the engine Valves and Ports purpose is to allow air and fuel to enter and leave the combustion chamber

Heat Engine Parts and Systems Pistons the round piece that slides up and down within the cylinder Connecting Rod and Crankshaft CR is attached from the bottom of the piston and attaches to the crankshaft the crankshaft converts reciprocating motion to rotary Combustion Chamber the area inside the Cylinder Head and Block

Heat Engine Parts and Systems Camshaft the mechanism used to open the valves at the right times it is driven by the crankshaft which is connected to the connecting rod (timed to the crankshaft) may be mounted in the block or on top of the block (OHC - Overhead camshaft) (DOHC - Dual Overhead Camshaft)

Heat Engine Parts and Systems Flywheel connected to the end of the crankshaft to smooth out any intermittent motion (remember we have intermittent combustion) utilize Newton’s Law  “An object in motion tends to remain in motion, whereas an object at rest tends to remain at rest”

Heat Engine Parts and Systems Carburetor/Fuel Injection mixes the air and fuel in the right proportion

Engine Systems Cooling: liquid and air - keep temp constant Fuel: monitor and control the feed Lubrication: reduce friction Ignition: providing the spark for combustion Starting: crank (battery & dc starter motor) Charging: replenish the battery Air/Exhaust: feed air in an out Computer Controlled: to aid - precision of sys. Fuel, ignition, etc. Pollution Control: environmental

Combustion Requirements 1) AIR 2) FUEL 3) SPARK 4) TIMING 5) COMPRESSION

Bore & Stroke Bore & Stroke help determine the size: Bore - diameter of the cylinder Stroke - distance the piston travels from TDC to BDC  determined by design of the crankshaft  center of the crankshaft to the center of the crankpin multiplied by 2 = the stroke distance

Four Stroke Engine Design One of the most popular reciprocating-type heat engines Intake: piston moves downward with intake valve open Compression: piston moving upward, all valves are closed Power: after the spark, power occurs downward Exhaust: as the piston moves upward again, exhaust valves open

Two-Cycle Engine Design Does not use standard valves like the 4-cycle Oil is added to the Air-Fuel mixture because there is no oil in the crankcase as with the 4-cycle engine design  the oil acts as a lubricant Compression Stroke up creates a vacuum and pulls in the fuel/oil mixture into the combustion chamber (Crankshaft) Ignition just before TDC, crankcase full, reed valve closed Power Stroke down exhaust is vented out by pressure on the fuel in the combustion chamber from the piston

Advantages & Disadvantages of 2-Stroke ADV: Very responsive (power pulse every rev.) Usually lighter than 4-cycle engines, fewer parts Can be operated at varying angles of operation no crankcase that holds oil DISADV Not as efficient as 4 stroke Not as durable

Diesel Engine Design Considered a 4 cycle, IC (can also have 2 cycle) Compression rather than spark ignition Glow plug and block heaters used to pre-warm fuel and engine on cold starts No carburetor (fuel injection) air enters on the intake stroke Fuel is injected during compression Extreme pressure (diesel engines have very high compression ratios) & heat ignite fuel

Rotary (Wankel) MAZDA Most popular during the 1970’s Not Reciprocating Rotors instead of Pistons No valves (only the intake and exhaust ports) Intermittent combustion, spark ignition, rotary design Few moving parts = extremely high revs.