Research Papers: Internal Combustion Engines

A Comparison Between Combustion Phase Indicators for Optimal Spark Timing

[+] Author and Article Information
Emiliano Pipitone

Dipartimento di Meccanica, University of Palermo, Vialle delle Scienze, Palermo 90128, Italypipitone@dima.unipa.it

J. Eng. Gas Turbines Power 130(5), 052808 (Jun 19, 2008) (11 pages) doi:10.1115/1.2939012 History: Received September 25, 2007; Revised January 15, 2008; Published June 19, 2008

The closed-loop control of internal combustion engine spark timing may be accomplished by means of a combustion phase indicator, i.e., a parameter, derived from in-cylinder pressure analysis, whose variation is mainly referable to combustion phase shift and assumes a fixed reference value under optimal spark timing operation. The aim of the present work is a comparison between different combustion phase indicators, focusing on the performance attainable by a feedback spark timing control, which uses the indicator as pilot variable. An extensive experimental investigation has been carried out, verifying the relationship between indicators’ optimal values and the main engine running parameters: engine speed, load, and mixture strength. Moreover, assessment on the effect of the most common pressure measurement problems (which are mainly related to pressure referencing, sampling resolution, top dead center determination, and cycle-by-cycle variations) on the indicators’ values and on the performance attainable by the spark timing control is included. The results of the comparison point out two indicators as the most suitable: the location of pressure peak and the location of maximum heat release rate. The latter, not available in literature, has been introduced by the author as an alternative to the 50% of mass fraction burned.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

In-cylinder pressure and its derivative, 2500rpm—IMEP 6bar (LPP and LMPR are shown)

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Figure 2

MFB and heat release rate, 2500rpm, 6bar BMEP (MFB50 and LMHR are shown)

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Figure 3

PR as function of CAD: the indicator PRM10 is the ratio between A (PR10) and B (PR55)

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Figure 4

BMEP and IMEP as a function of spark advance 3500rpm, λ=0.95

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Figure 5

Percentage efficiency loss due to bad spark advance setting (1500to3500rpm, 3bar and 6bar BMEP)

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Figure 6

Engine torque and combustion phase indicators as a function of spark timing (1500rpm, λ=1.1)

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Figure 7

Indicators versus engine speed (stoichiometric mixture, 3bar and 6bar BMEP)

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Figure 8

Indicators versus mixture strength

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Figure 9

(a) Spark advance error and (b) performance loss with indicators’ value on the edge of the variation range

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Figure 10

(a) Spark advance error and (b) performance loss with optimal spark advance control

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Figure 11

LMHR versus MFB50 (all operative conditions)

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Figure 12

(a) Maximum indicators’ evaluation error and (b) maximum spark advance errors for bad pressure referencing

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Figure 13

Mean and maximum pressure referencing variation versus start of the referencing arc

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Figure 14

Maximum pressure correction difference between “MAP” and k=1.32 referencing methods

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Figure 15

Pressure correction difference between “MAP” and k referencing methods for different polytropic indices

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Figure 16

(a) Indicators’ maximum evaluation errors and (b) spark advance maximum errors with varying sampling resolution

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Figure 17

IMEP evaluation error with wrong TDC reference

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Figure 18

(a) Indicators’ maximum evaluation errors and (b) spark advance maximum deviation from MBT value as a function of TDC error

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Figure 19

In-cylinder pressure cycle-by-cycle variation: 50 consecutive cycles with constant speed, load, A/F and spark timing

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Figure 20

Indicators cycle-by-cycle variation (3500rpm4.8bar IMEP, MBT SA, λ=1)

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Figure 21

Indicators’ range of variation versus number of engine cycles for the mean pressure cycle calculation (3200rpm, 3.78bar IMEP, COV IMEP 4.9%)

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Figure 22

Minimum number of engine cycles for stable indicators’ evaluation as a function of IMEP COV



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