Genebraldo Solved Problems

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Solved Problems by Ian Ray P. Genebraldo Solved Problems by Ian Ray P. Genebraldo Problem 7-1

Problem 7-1

An SI engine operating at 1200 RPM has a 10.2-m bore !ith the spar" pl#g An SI engine operating at 1200 RPM has a 10.2-m bore !ith the spar" pl#g o$set by %-mm

o$set by %-mm &rom enter&rom enter. 'he spar" . 'he spar" pl#g is (red at 20) pl#g is (red at 20) b'*+. It ta"es %.,) o&b'*+. It ta"es %.,) o& engine rotation &or omb#stion to develop and get into ame

engine rotation &or omb#stion to develop and get into ame propagatiopropagation moden mode !here the average ame speed is 1,./ mse.

!here the average ame speed is 1,./ mse. +al#late

+al#late a3

a3 'ime o& one omb#'ime o& one omb#stion proess a&ter ame has devstion proess a&ter ame has developed i.e. time &oreloped i.e. time &or ame &ront to reah the &#rthest

ame &ront to reah the &#rthest ylinder !all3. 4se5ylinder !all3. 4se5 b3

b3 +ran" angle posi+ran" angle position at the end otion at the end o& omb#stion.& omb#stion. Sol#tion

Sol#tion a3

a3 6lame travel d6lame travel distane  boistane  bore23 8o$setre23 8o$set *

*tt  10.2 m23 8 0.%  10.2 m23 8 0.% m  ,.7 mm  ,.7 m

'ime  *

'ime  *tt  9  9& &  0.0,7 m31,./ mse3   0.0,7 m31,./ mse3  0.0036 sec0.0036 sec

b3

b3 +omb#stion starts +omb#stion starts at 1:.,) bat 1:.,) b'*+'*+ 'ime o& o

'ime o& omb#stion in degmb#stion in degrees o& enginrees o& engine rotatione rotation 0.00:% se31200%0 revse3:%0)rev3  2,.;) 0.00:% se31200%0 revse3:%0)rev3  2,.;) +ran" position at end o&

+ran" position at end o& omb#stionomb#stion 2,.;) < 1:.,) 

2,.;) < 1:.,)  12.4⁰ aTDC12.4⁰ aTDC

Problem 7-2 Problem 7-2

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It is desired that ame termination be at the same ran" angle position !hen the speed o& the engine in Problem 7-1 is inreased to 2000 RPM. In this range ame development ta"es the same amo#nt o& real time and ame speed is related to engine speed as 9& is proportional to 0.;2=.

+al#late

a3 6lame speed at 2000 RPM. 4mse5

b3 +ran" angle position !hen the spar" pl#g sho#ld be (red. 3 +ran" angle position !hen ame propagation starts.

Sol#tion

a3 9el2000  0.;232000120031,./ ms3  24.23 m/sec

b3 'ime o& omb#stion development

t  %.,)34:%0)rev31200%0 revse35  0.000;0 se 'ime o& omb#stion at 2000 rpm

t  *& 9el&  0.0,7 m3 2>.2: mse3  0.002:, se

'otal time o& ignition and omb#stion at 2000 rpm t  0.000;0 se3 8 0.002:, se3  0.00:2, se 'otal time in degrees o& engine rotation

0.00:2, se32000%0 revse3:%0)rev3  :;)

6or omb#stion to end at 12.>) a'*+ spar" pl#g m#st be (red at :;) - 12.>)  26.6 bTDC

3 ?ngine rotation d#ring omb#stion

0.002:, se32000%0 revse3:%0)rev3  2/.2) +omb#stion m#st start at

2/.2) - 12.>  15.8⁰ bTDC

Problem 7-:

A +I engine !ith a :.2-inh bore and :.;-inh stro"e operates at 1/,0 RPM. In eah yle &#el in@etion starts at 1%) b'*+ and lasts &or 0.001; seond. +omb#stion

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starts at /) b'*+. *#e to the higher temperat#re the ignition delay o& any &#el in@eted a&ter omb#stion starts is red#ed by a &ator o& t!o &rom the original I*. +al#late

a3 I* o& (rst &#el in@eted. 4se5

b3 I* o& (rst &#el in@eted in degrees o& engine rotation.

3 +ran" angle position !hen omb#stion starts on last &#el droplets in@eted. Sol#tion

a3 I* o& (rst &#el in@eted  /) o& rotation

t  /)34:%0)rev31/,0%0 revse35  0.00072 sec

b3 I* o& (rst &#el in@eted in degrees o& engine rotation  start o& in@etion < start i& omb#stion

I*  1%) - /)  8⁰

3 Ignition delay is hal& o& original I* I*  0.00072 se32  0.000:% se

'ime bet!een the start o& in@etion and (nal in@etion o& &#el droplets t  0.001; se3 8 0.000:% se3  0.0022% se

In degrees o& engine rotation 0.0022% se31/,0%0 revse3:%0)rev3  2,.1)

+ran" position !hen last droplets start to omb#st 1%) b'*+ 8 2,.1)  9.1⁰ aTDC

Problem 7->

A :.2-liter SI engine is to be designed !ith bo!l-in-piston omb#stion hambers. ith a entral spar" pl#g and omb#stion at '*+ this gives a ame

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travel distane o& B>. 'he engine is to operate !ith an average piston speed o& / mse and a b#rn angle o& 2,) o& ran" rotation. Stro"e and bore !ill be related by S  0.;,B.

+al#late

a3 Average ame speed i& the design is &or an in-line &o#r-ylinder engine. 4mse5

b3 Average ame speed i& the design is &or a 9/ engine. 4mse5 Sol#tion

a3 6or 1 ylinder o& a > ylinder engine

9d  :.2 C3>  0./ C  0.000/ m:   π >3B2S   π >3B20.;,3

B  0.102:, m S  0.;,30.102:,3  0.0;72 m 6inding the engine speed

Dp  / mse  2S=  2 stro"esrev30.0;72 mstro"e3=

=  >1.1, revse  2>%; rpm

'ime o& ame t  2,)34:%0)rev3>1.1, revse35  0.001%; se

*istane o& ame travel *&  B>  0.102:, m3>  0.02,,; m

6lame speed 9&  *& t  0.02,,; m30.001%; se3  15.15

m/sec

b3 6or 1 ylinder o& 9/ engine

9d  :.2 C3/  0.> C  0.000> m:   π >3B2S   π >3B20.;,3

B  0.0/12>m S  0.;,30.0/12>3  0.0771/ m 6inding the engine speed

Dp  / mse  2S=  2 stro"esrev30.771/ mstro"e3=

=  ,1./: revse  :110 rpm

'ime o& ame t  2,)34:%0)rev3,1./: revse35  0.001:> se

*istane o& ame travel *&  B>  0.0/12> m3>  0.020:1 m

6lame speed 9&  *& t  0.020:1 m30.001:> se3  15.15

m/sec

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A large +I engine operating at :10 RPM has open omb#stion hambers and diret in@etion !ith 2%-m bores a 7:-m stro"e and a ompression ratio o&

1%.,1. 6#el in@etion in eah ylinder starts at 21) b'*+ and lasts &or 0.01; seonds. I* is 0.00%, seonds.

+al#late

a3 I* in degrees o& engine rotation.

b3 +ran" angle position !hen omb#stion starts. 3 +ran" angle position !hen in@etion stops. Sol#tion

a3 I*  0.00%, se3:10%0 revse3:%0)rev3  12.1)

b3 +ran" angle start o& omb#stion3  angle o& &#el in@etion 8 angle o& I* 21) b'*+ 8 12.1)  8.9⁰ bTDC

3 ?ngine rotation per in@etion  d#ration o& &#el in@etion3rps3:%0)rev3 0.01; se3:10%0 revse3:%0)rev3  :,.:)in@etion

+ran" angle end o& in@etion3  angle o& &#el in@etion 8 engine rotation per in@etion