Internal Combustion Engine Performance Characteristics

Internal Combustion Engine Performance Characteristics

Submitted By MD MARUFUR RAHMAN

Submitted To

Dr Mark Ellis

Thermofluids and Turbomachinery 2011-2012 Assignment

Table of Contents

1.0 Introduction:....................................................................................................................3 2.0 Question Section 1: .........................................................................................................3

2.1 Calculation and table for performance characteristics: ...............................................3 3.0 Question Section 2: .........................................................................................................6

3.1 Performance characteristics Vs engine speed (rpm) Graphs:......................................7 3.1.1 Raw Torque Vs Engine Speed: ............................................................................7 3.1.2 Raw Power Vs Engine Speed: .............................................................................7 3.1.3 BMEP Vs Engine Speed: .....................................................................................8 3.1.4 SFC Vs Engine Speed:.........................................................................................9 3.1.5 AFR Vs Engine Speed: ........................................................................................9 3.1.6 Volumetric Efficiency Vs Engine Speed: ..........................................................10 3.1.7 Brake Thermal Efficiency Vs Engine Speed: ....................................................10 3.1.8 Exhaust Temperature Vs Engine Speed:............................................................11

4.0 Question Section 3: .......................................................................................................11 4.1 Corrected Measured Raw Torque and Raw Power: ..................................................11 4.1.1 Corrected Measured Raw Torque: .....................................................................12 4.1.2 Corrected Measured Raw Torque Vs Engine Speed Graph: .............................12 4.1.3 Corrected Measured Raw Power: ......................................................................13 4.1.4 Corrected Measured Raw Power Vs Engine Speed Graph:...............................13

5.0 Question Section 4: .......................................................................................................14 5.1 Air Standard Cycle Efficiency: .................................................................................14 5.1.1 Test Engine Air Standard Cycle Efficiency:......................................................14 5.1.2 Differences between Air Std Cycle efficiency and Thermal efficiency: ...........15

6.0 Question Section 5: .......................................................................................................16 6.1 Construct an Energy Balance diagram:.....................................................................16

4.0 Conclusion: ...................................................................................................................17 5.0 References:....................................................................................................................17

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Thermofluids and Turbomachinery 2011-2012 Assignment

1.0 Introduction:

A single-cylinder 4-stroke SI engine was tested on an engine dynamometer at LSBU. Engine torque, fuel flow, airflow, and exhaust gas temperature were measured at 7 different engine speeds, all full-load (FT). However, the small internal combustion engine is extensively used as a convenient and compact source of power such as cultivators, pumps, cement mixers and motor cycles. [1] Here I tried to address the questionnaires directly according to the concept of lecture notes, text books and laboratory engine performance test. Engine specification and performance test results were given as follows:

2.0 Question Section 1:

Calculate and expand Table1 to include the following performance characteristics: Raw Torque (Nm), raw Power (kW), BMEP (kPa), fuel mass flow rate (kg/hr), SFC (g/kWh), air volumetric flow rate (m3/hr), air mass flow rate (kg/hr), AFR, volumetric efficiency (%), brake thermal efficiency (arbitrary overall efficiency) (%) and exhaust temperature (degC). 2.1 Calculation and table for performance characteristics: "In an ideal world, each engine cycle (2 rev for 4-stroke engine) would start with the cylinder being completely full of fuel-air mixture, and once ignited burn completely to release all of the

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Thermofluids and Turbomachinery 2011-2012 Assignment

fuel energy rapidly. The work done and thus torque would be the same each engine cycle. In fact ideal world the same amount of torque would be produced at any engine speed."[2] The calculations for test one is as follows:

i) Raw Torque = 6.4 Nm;

ii) Raw Power = Torque ? Speed = 6.4 Nm? 392.70 = 2.51 kW

Speed = -P!" ? 2

?"

= 392.70

]

Brake Mean Effective Pressure (BMEP) allows comparison of work output between engines

of different types and sizes.

iii) BMEP =

(

() )? (

(kPa)

/)

A

=B

CD CE F

=

2-

I JKC CLMNLC

A

=B

CD CEF /2 = 4 -

I JKC CLMNLC

=

.! ? " .#! ? "$% ?()(&?'(*)

= 412.44? 10- Pa

= 412.44 kPa

O 6 = 195 cc = 195? 10 ? .-

= 1.95 ? 10 @ .-

iv) Fuel mass flow rate,

./ 01

2

=

4

? 5 21

67

(Kg/hr)

= 740 ?

:? "$) -?)(?; )(

= 1.64 Kg/hr

Density, 4 = SG? 4 R6 = 0.74? 1000 SM . = 740 SM . -

v) Specific Fuel Consumption,

SFC = / (g/kWh) = .?@? "

.!

= 652.29 g/kWh

Where: P = Power (kW) ./ 01 2= mass flow rate of fuel (g/hr)

vi) Air mass flow rate,

From the test bed figure 2.6 (viscous Flow meter calibration) graphs

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Thermofluids and Turbomachinery 2011-2012 Assignment

./ R7 = 11.90 Kg/hr

vii) Air Volumetric Flow rate,

O/R7

= calibration factor ?

/ TUV WTUV

(m3/hr)

= 1.007? .#"

. "!

= 9.95 m3/hr

viii)

Air-Fuel Ratio (AFR),

AFR = / TUV

/

= .#"

.?@

= 7.26

C.F = ? Tb =T> dTb =T>e

@?(

dbT>

'

)*

c=

dbT>e @

dTb =T>

=

" "

" -

?

( (

#-e #-e

@) @)

?

(

##--)'*

= 1.007

4R7

= TUV =

." -? "'

fd (". :P? " )? #-

= 1.205 Kg/m3

ix) Volumetric efficiency,

Volumetric efficiency is a measure of effectiveness of the cylinder filling process (working fluids ? air only). However, it significantly be affected by intake and exhaust system design and engine speed.

X

5 21 6 7YZ [

[/ TUV (\ )?](V /*)

=

.#!

#.#!? ? "$%

; )((

?()(&?'(*)

?

100%

= 45.33 %

A

=

B

CD CEF = 2 -

I JKC CLMNLC

A

=B

CD CEF /2

=

4-

I JKC CLMNLC

x) Brake thermal efficiency(arbitrary overall efficiency),

X

6_

R2Z

`R / ?a

=

.! ? " .?@? );((?@ """? "

? 100%

= 13.14 %

g01 2 Z 42000 KJ/Kg ./ 01 2 = 1.64 Kg/hr

xi) Exhaust temperature, Exhaust temperature = 450 degC

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