Condition 2: Open-valve Injection, Idle Condition

The degree o f stratification that may be obtained with op en -valve injection can vary with injection timing C onsequently, the op en -valve injection tim ings w ere varied betw een start o f injection 65° A T D C to 135° A T D C in 10° intervals for the idle condition An additional test w as performed with the end o f injection timed at 6 0° A TDC. The FFID traces obtained at the spark plug and cylinder bore from sw eep 2 for all the op en -valve injection tim ings have been plotted in figures 8.9 a and b to 8.1 7 a and b.

X 1 0 0 .6 Sr. I 2 720 ( r a n k A n g le (D e g re e s)

Figure 8.9 a: Sweep 2, probe at spark plug, end of injection timing 60° ATDC,

idle condition

x10

8 Ï - 3 o

0

1

2 0 0 _{( r a n k A ngle (D e g re e s) 720}

Figure 8.9 b: Sweep 2, probe at cylinder bore, end of injection timing 60° ATDC,

idle condition

0 .6

I 2

( r a n k A n g le (D e g re e s) 720

Figure 8.10 a: Sweep 2. probe at spark plug, injection timing 65° ATDC, idle

condition

( r a n k A ngle (D e g re e s) 720

Figure 8.10 b: Sweep 2, probe at cylinder bore, injection timing 65° A T D C , idle

xIO"

C r a n k A n g le (D e g re e s) 720

Figure 8.11 a: Sweep 2, probe at spark plug, injection timing 75° A TDC, idle

condition

x10“

720 C r a n k A n g le (D e g re e s)

Figure 8.11 b: Sweep 2, probe at cylinder bore, injection timing 75° A T D C , idle

condition

x10“

C r a n k A n g le (D e g re e s) 720

Figure 8.12 a: Sweep 2, probe at spark plug, injection timing 85° A TDC, idle

condition

xIO

8

%

a

3

0

1

2 0 0 _{( r a n k A n g le (D e g re e s)} 720

Figure 8.12 b: Sweep 2, probe at cylinder bore, injection timing 85° A T D C , idle

condition

x10"

8

Î '

!■

0

1

2 0 720 ( r a n k A n g le (D e g re e s)

Figure 8.13 a: Sweep 2, probe at spark plug, injection timing 95° ATDC, idle

condition

X10

8

O

r

#4

o 2 0 0 _{C r a n k A n g le (D e g re e s)} 720

Figure 8.13 b: Sweep 2, probe at cylinder bore, injection timing 95° ATDC, idle

1. ' r t ^

C r a n k A n g le (D e g re e s) 720

Figure 8.14 a: Sweep 2, probe at spark plug, injection timing 105° A TDC, idle

condition

x10“

C r a n k A n g le (D e g re e s) 720

Figure 8.14 b: Sweep 2, probe at cylinder bore, injection timing 105° A T D C , idle

condition

xIO"

( r a n k A n g le (D e g re e s) 720

Figure 8.15 a: Sweep 2, probe at spark plug, injection timing 115° ATDC, idle

condition

x10

8

Ï

2 0

0

( r a n k A n g le (D e g re e s) 720

Figure 8.15 b: Sweep 2, probe at cylinder bore, injection timing 115° ATDC, idle

condition

720 ( r a n k A n g le (D e g re e s)

Figure 8.16 a: Sweep 2, probe at spark plug, injection timing 125° ATDC, idle

condition

720 ( r a n k A n g le (D e g re e s)

Figure 8.16 b: Sweep 2, probe at cylinder bore, injection timing 125° ATDC, idle

x10"

8

0,

720 ( r a n k A n g le (D e g re e s)

Figure 8.17 a; Sweep 2, probe at spark plug, injection timing 135° A TDC, idle

condition

I—

( r a n k A n g le (D e g re e s) 720

Figure 8.17 b: Sweep 2, probe at cylinder bore, injection timing 135° A TDC, idle

condition

Considering the traces obtained at the spark plug (figures 8.9 a -8 .1 7 a), the pre-flame characteristics varied significantly from cycle to cycle With closed -va lv e injection there w as a gradual flattening o f the curve prior to flame arrival and the cycle to cycle variability w as minimal (figures 8.3 a and 8 5) In contrast, the pre-flam e HC level for op en -valve injection exhibited a jagged appearance and com prised o f a number o f peaks and troughs. It w as thought that th ese peaks and troughs represented real-time HC concentration fluctuations due to rich clouds o f vapour or fuel droplets passing the probe

Summaries o f the results show n in figures 8.9 to 8.17 a and b are given in figures 8.18 and 8.19. Figure 8 18 sh ow s the peaks o f HC readings for each sw eep plotted against cycle number for the probe situated at the spark plug, the different colours refer to the different injection timing Although the amount o f fuel injected w as the same in each case, it can be seen that the higher HC concentrations w ere recorded for all op en -valve injection tim ings com pared with the clo sed -valve injection timing (circles). The timing that gave the highest readings, and hence m ost stratification, w as w hen injection started 135° A TDC. The pattern is not so clear for the probe situated in the cylinder bore (figure 8 .1 9 ), and this is to be expected considering that it w as covered by the piston. H ere only the results for closed -valve injection and the op en -valve injection tim ings that ga ve the low est and highest peaks for each cycle have been plotted, together with the peaks per

cycle for an open-valve injection timing o f 135° ATDC.

Key For Figures + Injection starts 50° ATDC ■k

Injection starts 105° ATDC Injection starts 65° ATDC ■k

Injection starts 115° ATDC + Injection starts 75° ATDC k

Injection starts 125° ATDC Injection starts 85° ATDC k

Injection starts 135° ATDC -H Injection starts 95° ATDC 0 Closed-valve Injection

12 10

8

1

5 4 X 2 0 0 5

10

1 5 C y c le N um ber

Figure 8.18: Peak obtained in each sweep at the spark plug for each injection timing against sweep number, idle condition

12 10

f 6

s

CL

O

^ 4

- ï î i î l ï ^

2 0 0 5 10 1 5 C y c le N u m be r

Figure 8.19: Peak obtained in each sweep at the cylinder bore for each injection timing against sweep number, idle condition

In document Observation and measurement of fuel distribution within a spark-ignition engine (Page 193-198)