Experiment #4

IC Engine

Indicator Diagram

The indicated work per cycle is computed from the area under the p-v diagram

Indicated power =

expansion

compressionintake

exhaust

ignition

Pi

WiN

np

Work/power stroke rev./time rev/power stroke

Brake power = indicated power -friction power Pb = Pi-Pf

Experimental Apparatus

Engine rpm

ThrottleControls:• Throttle setting• Load valve

Instrumentation:• Engine rpm• Dynamometer pressure• Fuel flow rate• Cylinder head temperature• Oil temperature

Objectives

• Using a single cylinder four stroke engine

• Mea sure engine power, rpm and fuel consumption at difference throttle settings

• Plot relevant engine parameters as a function of engine rpm and discuss the results

Engine Parameters • Measured Brake power (W):

• Brake specific fuel consumption (kg/Nm):

• Brake mean effective pressure (N/m2):

• Brake Torque (Nm):

• Fuel/Air mass ratio

power brakerate flow mass fuel

bP

fm

bsfc

efficiency pump

pressurer dynamometerate flow oilr dynamometeppQ

bP

bmepW

bV

d

Pbnp

VdN

brake power revolutions per power stroke

displacement volume rev/time

P

bN

brake powerrev/time

Use p = 0.8

amf

mF/A

Engine Parameters (continued)

Volumetric Efficiency = Nd

Vai

pnam

ntdisplacemecylinder densityair strokeower inducted/pair of mass

dV

ai

amv

v

Engine rpm

Effects of: air friction chocking backflow, etc

mP

bP

iMechanical Efficiency

HVHbsfc

1

valueheating fuelrate flow fuel

power brake

HVHf

mb

P

f Conversion Efficiency:

Use HHV = 44 MJ/kg, and

Engine Parameters (continued)

p2npApSbmep

pn

Nd

Vbmep

pnHV

N(F/A)Hd

Vaivf

HV(F/A)HamfHVH

fm

fbP

bmepfvHHV

aiFA

VdApL

S p 2LNwhere

Report

• For each throttle setting (1/4,1/2,3/4,full) – Compute power, torque,sfc,mep, conversion efficiency– Plot these computed quantities against engine rpm– Discuss the results using references, and the relationships in the notes – Determine the most desirable engine speed for power,torque and

efficiency• Compare the efficiencies with that of an idea Otto cycle• Answer the question on connecting rod stress

PLEASE REPORT YOUR ANSWERS IN SI UNITS