background for ic engine lab

Background for IC Engine Lab

• Review of Thermodynamics

• Fundamentals of Combustion

• Engine Emissions and Smog

• 3-Way Catalytic Converter

• Objectives of Lab

• Overview of Lab System

IC Engine: Theremodynamics

• engine\applet.htm

• P-V diagram: Work

• Thermal Efficiency: Work/Heat

Otto Cycle: =

• Energy Balance: Heat Losses1

11

kr

Fundamentals of Combustion

• Fuel + Oxidizer -> Products

• Chemical Reaction->

Heat Release

• Heat of Combustion

Properties of Common Fuels

Property Natural

Gas Gasoline Diesel

Flammability Limits (volume % in air)

5-15 1.4-7.6 0.6-5.5

Autoignition Temperature (°F)

842 572 446

Minimum Ignition Energy in Air (10-6 BTU)

0.27 0.23 0.23

Peak Flame Temperature (°F)

3423 3591 3729

Combustion Chemistry

• Overall Description of Chemical Reaction

CnHm +[ (n+m/4) / )x4.7619 (0.21O2 +0.79N2)=

np{ XCaHb CaHb + XCO2 CO2 + XCO CO + XH2O H2O + XO2 O2 + XN2N2},

where = Equivalence RatioOctane = C8 H18; n=8, m=18

Equivalence Ratio

)n / n(

)n / n( =

)Air / (Fuel

)Air / (Fuel

stoichaf

actualaf

stoich

actual

> 1 Rich mixtures : too much fuel< 1 Lean mixutres : too much oxidizer=1 Stoichiometric : perfect condition

** Note many countries use air-fuel ratio: =A/F= stoich / actual

Emissions from IC Engines

• Unburned Hydrocarbons (HC), Soot, CO

• Nitrogen Oxides: NOx (NO+ NO2) 

• N2+O - > NO + N (R1)

• N+O2 -> NO + O (R2)

Emissions as function of air-fuel ratio

Smog

• What is smog? The term "smog" was first coined more than three decades ago to describe a mixture of smoke and fog in the air

• Smog is the popular name for the brownish-yellow haze that hangs in the warm, still air over many North American cities.

• Smog is made up, in large part, of ozone gas.

Smog (O3+PAN)

•Nitrogen Oxides: These are produced when fossil fuels like gasoline, natural gas, heating oil and coal are burned. These gases are also produced naturally by forest fires, volcanoes and soil. •Volatile Organic Compounds (VOCs): These come mainly from the evaporation of liquid fuels, solvents and organic chemicals (nail polish remover, barbecue starter, paints, cleaners) and from burning gasoline. VOCs are also produced naturally by trees in cities and forests.

Chemistry of Photochemical Smog

• Sunlight.

• The production of oxides of nitrogen (NOx).

• The production of volatile organic compounds (VOCs).

• Temperatures greater than 18 degrees Celsius.(T> 18 oC)

Chemistry of Photochemical

• Ozone (O3) and PeroxyAcetyl Nitrate (PAN) { R-C-O-O2-NO2}

NO2 + sunlight »»» NO + O

O + O2 »»» O3

NO2 + R »»» products such as PAN

Symbol R represents a hydrocarbon (a molecule composed of carbon, hydrogen and other atoms) which is primarily created from volatile organic compounds

Typical Exhaust Emissions From Gasoline Engines

HC 750 ppm* CO2 13.5 vol-% NOX 1050 ppm O2 0.51 vol-% CO 0.68 vol-% H2O 12.5 vol-% H2 0.23 vol-% N2 72.5 vol-% * Based on C3

Emission Controls

Three-Way Catalyst

• The precious metals currently used in three-way catalyst applications are platinum, palladium and rhodium.

Three-Way Catalyst

• Rhodium has proven to be an efficient catalyst for NOX reduction.

• Palladium and platinum metals are used in CO and hydrocarbon oxidation reactions.

• 2 CO + O2 → 2 CO2

• 4 CnHm + (4n + m)O2 → 4n CO2 + 2m H2O

• 2NO + 2 CO → N2 + 2CO2

Three-Way Catalyst

Three-Way Catalyst- T Effect

• Conversion as a function of temperature: rate controlling regimes

Three-Way Catalyst

• Automotive emission control system showing the pre- and main catalytic converters

Three-Way Catalyst: Effect

• The conversion efficiency (%) of a three-way catalyst as a function of A/F-ratio. An A/F-ratio of 14.6 corresponds to stoichiometric gasoline-air combustion.

Rich Mixtures Lean

IC Engine Lab

dynamometer

IC Engine Lab

IC Engine Lab

• Overall Objectives• a)   Thermodynamics cycle efficiency and P-V

diagram of the actual cycle,• b)  The most important parameter(s) controlling

engine power,• c)  The optimal speed for best fuel economy, and• d) The best operation condition that yields the

lowest pollutant emissions.• e) Effects of turbocharger, intercooling, timing

Schematic of Lab System

Dynamometer

Shaft

City water

Water outflow

Exhaust

Air in

T 7

T 8

T 12

T 5

T 6

T 3 T 4

T 2

T 1 T 11

Engine

Turbocharger

Heat exchanger

Volvo Intercooler

T9 T 10

Exhaust M anifold

after catalytic converter

T13

T 13

T 14

T 13

Catalytic Converter

Air/water inlet

Turbocharger for IC Engines

Principles of Turbochargers

Turbochargers

Orifice Plate: Flow Measurement

Connected to manometer

Manometer

p=gh

= fluid density

g= gravity force

h=height

• http://www.efunda.com/formulae/fluids/manometer.cfm

Principle of Eddy-Current Electro Brake Dynamometer

• The current through the stator becomes heat on the stator. Rotational movement is coverted into heat by braking and heat is removed by

cooling water.

Applications with Dynamometer

Large 2-Stroke Diesel Engines

http://www.bath.ac.uk/~ccsshb/12cyl/

Large 2-Stroke Diesel Engines

• The cylinder bore is just under 38" and the stroke is just over 98".  Each cylinder displaces 111,143 cubic inches (1820 liters) and produces 7780 horsepower.  Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the fourteen cylinder version.

•      Some facts on the 14 cylinder version:Total engine weight:2300 tons  (The crankshaft alone weighs 300 tons.) Length:89 feet Height:44 feet Maximum power:108,920 hp at 102 rpm Maximum torque:5,608,312 lb/ft at 102rpm      Fuel consumption at maximum power is 0.278 lbs per hp per hour (Brake Specific Fuel Consumption).  Fuel consumption at maximum economy is 0.260 lbs/hp/hour.  At maximum economy the engine exceeds 50% thermal efficiency.  That is, more than 50% of the energy in the fuel in converted to motion.     For comparison, most automotive and small aircraft engines have BSFC figures in the 0.40-0.60 lbs/hp/hr range and 25-30% thermal efficiency range.