engine characteristics

NATIONAL INSTITUTE OF NATIONAL INSTITUTE OF TECHNICAL TEACHERS TECHNICAL TEACHERS TRAINING AND RESEARCH TRAINING AND RESEARCH CHANDIGARH CHANDIGARH

112/20/14

Prof. (Dr.) MP PooniaDirector, NITTTR

Chandigarh (India)

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Diesel Emission Reductions

Fuel technology

Combustion technology

Aftertreatment technology

Fuel system technology

Better understanding of combustion

Alternate Fuels (Biodiesel)Low

sulfur

PM trap

Rate controlHigh pressure Multi-injection

EGR technology

Others

Control technology

Technology Pathway

Emission norms for passenger cars ( Petrol)

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Norms CO( g/km) HC+ NOx)(g/km)

1991Norms 14.3-27.1 2.0(Only HC)

1996 Norms 8.68-12.40 3.00-4.36

1998Norms 4.34-6.20 1.50-2.18

stage2000 norms

2.72 0.97

Bharat stage-II 2.2 0.5

Bharat Stage-III 2.3 0.35(combined)

Bharat Stage-IV 1.0 0.18(combined)

Emission norms for Heavy diesel vehicles:

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Norms CO (g/kwhr)

HC(g/kwhr)

Nox(g/kwhr)

PM(g/kwhr)

1991 Norms 14 3.5 18 -

1996 Norms 11.2 2.4 14.4 -

stage 2000 Norms 4.5 1.1 8.0 0.36

Bharat stage-II 4.0 1.1 7.0 0.15

Bharat Stage-III 2.1 1.6 5.0 0.10

Bharat Stage-IV 1.5 0.96 3.5 0.02

Emission sources in a gasoline fuelled car

Ref : http://nptel.iitm.ac.in/courses/112104033/2

Emission Sources in a Diesel Engine Powered Bus

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• Volumetric efficiency (ηv) = (mass of air actually drawn into cylinder) / (mass of air that ideally could be drawn into cylinder)

where ρair is at ambient = Pambient/RTambient and R - 287 J/kgK for air• Volumetric efficiency indicates how well the engine “breathes” -

what lowers ηv below 100%?– Pressure drops in intake system (e.g. throttling) & intake

valves– Temperature rise due to heating of air– Volume occupied by fuel– Non-ideal valve timing– “Choking” (air flow reaching speed of sound) in part of intake

system having smallest area

Volumetric Efficiency

nNVdairv /

(measured) mair

ρη

≡

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Turbochargers & Superchargers

• Superchargers: mechanically driven from engine crankshaft

• Turbochargers: driven by waste exhaust gases increased air mass improves the engine's thermal efficiency (fuel economy) and emissions performance,

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• Engine performance is specified in both in terms of power and engine torque - which is more important?– Wheel torque = engine torque x gear ratio

tells you whether you can climb the hill

Power and Torque

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– Power tells you how fast you can climb the hill– Torque can be increased by transmission (e.g.

2:1 gear ratio ideally multiplies torque by 2) Power can’t be increased by transmission; in fact because of friction and other losses, power will decrease in transmission

– Power tells how fast you can accelerate or how fast you can climb a hill, but power to torque ratio ~ N tells you what gear ratios you’ll need to do the job

There is a maximum in the brake power versus engine speed called the ratedbrake power.

At higher speeds brake power decreases as friction power becomes significant compared to the indicated power There is a maximum in the torque versus speed called maximum brake torque (MBT).

Brake torque drops off: • at lower speeds do to heat losses • at higher speeds it becomes more difficult to ingest a full charge of air.

Max brake torque

1 kW = 1.341 hp

Rated brake power

Power and Torque versus Engine Speed

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Mathematically different from the British unit1 Power PS = 0.986 BhpPferde Stärke = Horse Strength (German)Power (PS@rpm)

67@5500 65@6200

Torque (Nm@rpm)

99@2800 84@3500

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Convert from these to watts (W)

multiply by

erg's per second (erg/s) 0.000 000 1

horsepower (electric) 746

horsepower (hp)(metric,DIN,PS)

735.4988

horsepower (hp)(U.K.) 745.7

kilowatt (kW) 1000

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Engine

Engine Type/Model 1.4L SOHC PetrolDisplacement cc 1405Power (PS@rpm) 60PS @4500rpmTorque (Nm@rpm) 105Nm @2500rpmValve Mechanism SOHCBore (mm) 75Stroke (mm) 95Compression Ratio 9:1

No of Cylinders (cylinder) 4

Cylinder Configuration Inline

Valves per Cylinder (valve) 2

Fuel Type PetrolFuel System Carburettor mechanical fuel pump

Engine Torque and Power

Torque is measured using a dynamometer.

Load cell

Force FStatorRotor

b

N

The torque exerted by the engine is: T = F b with units: J

The power Wdot delivered by the engine turning at a speed N and absorbed by the dynamometer is:

Wdot = ω T = (2π N) T w/units: (rad/rev)(rev/s)(J) = Watt

Note: ω is the shaft angular velocity with units: rad/s

Indicated WorkGiven the cylinder pressure data over the operating cycle of the engine one can calculate the work done by the gas on the piston.

The indicated work per cycle is ∫= PdVWi

CompressionW<0

PowerW>0

IntakeW>0

ExhaustW<0

WA > 0

WB < 0

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Indicated Mean Effective Pressure (Pim):

p-V diagram for an ideal four-stroke cycle engine

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I.C. ENGINE TESTING

Measurement of Air Supply of an I.C. Engine:

Measurement of Airby Air Box Method.

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