The increasing attention in reducing pollutant emissions and fuel consumption in internal combustion engines is promoting the development of more sophisticated control systems for the diagnosis and the optimization of the combustion process. In this view, the real-time monitoring of the in-cylinder pressure is becoming mandatory in order to ensure the desired levels of performance and efficiency. At the current state of technology, however, the cost and the intrusiveness of pressure sensors, coupled with the harsh operating conditions that limit their lifetime, make the direct measurement of in-cylinder pressure not suitable for mass production applications yet. Therefore, cost-effective and reliable alternative solutions to extract the pressure trace are of major interest. In this study, a methodology for this scope has been developed and validated with experiments. The methodology consists in a two-step procedure; first, the mechanical stress signal coming from a piezoelectric strain washer, installed under one of the engine studs, is considered. Then, this information is coupled with a 0D thermodynamic model, able to estimate the in-cylinder pressure for the entire cycle without combustion. In this way it is possible to compare in real-time the estimated in-cylinder pressure and the mechanical stress measured on the engine stud and to define a direct mathematical correlation between the two. The developed model has proven to properly estimate the correlation between stud stress and in-cylinder pressure, providing a more accurate estimation of the in-cylinder pressure, pressure peak position and maximum value, together with the parameters related to the combustion process.

1.
Pestana
,
G.
, “
Engine Control Methods Using Combustion Pressure Feedback
,”
SAE Technical Paper 890758
, (
1989
); DOI:
2.
Wibberley
,
P.
and
Clark
,
C.
, “
An Investigation of Cylinder Pressure as Feedback for Control of Internal Combustion Engines
,”
SAE Technical Paper 890396
, (
1989
); DOI:
3.
El-Ghamry
,
M.
,
Steel
,
J.
, and
Reuben
,
R.
, “
Indirect measurement of cylinder pressure from diesel engines using acoustic emission
”,
Mechanical Systems and Signal Processing
751–765
, (
2005
); DOI:
4.
Fleming
,
W.
, J., “
New automotive sensors–a review
,”
IEEE Sensors Journal
, Vol.
8
, no.
11
, pp.
1900
1921
, (
2008
); DOI:
5.
Moskwa
,
J.
and
Bucheger
D.
, “
A new methodology for use in engine diagnostics and control, utilizing ‘‘synthetic’’ engine variables: theoretical and experimental results
”,
Journal of Dynamic Systems
,
2001
; DOI:
6.
Moro
,
D.
,
Cavina
N.
and
Ponti
,
P.
In-cylinder Pressure Reconstruction Based on Instantaneous Engine Speed Signal
J. Eng. Gas Turbines Power
124
(
1
),
220
225
, (
2001
); DOI:
7.
Hamedović
,
H.
,
Raichle
,
F.
,
Breuninger
,
J.
,
Fischer
,
W.
 et al., “
IMEP-Estimation and In-Cylinder Pressure Reconstruction for Multicylinder SI-Engine by Combined Processing of Engine Speed and One Cylinder Pressure
,”
SAE Technical Paper 2005-01-0053
,
2005
; DOI:
8.
Bengtsson
,
F.
, “
Estimation of Indicated and Load Torque from Engine Speed Variations
, Master’s thesis,
Linkoping University
,
2006
.
9.
Hamedovic
,
H.
,
Raichle
,
F.
,
Breuninger
,
J.
,
Fischer
,
W.
,
Dieterle
,
W.
,
Klenk
,
M.
, “
IMEP-Estimation and In-Cylinder Pressure Reconstruction for Multicylinder SI-Engine by Combined Processing of Engine Speed and One Cylinder Pressure
”,
SAE World Congress & Exhibition
,
2005
; DOI:
10.
Frelund
,
A.
, R., “
Engine Combustion Chamber Pressure Sensor
”, US Patent 4,601,196, (
1986
).
11.
Sellnau
,
M.
, “
Combustion Pressure Sensor
”, US Patent 4,969,352, (
1990
).
12.
Sellnau
,
M.
, “
Non-Intrusive Cylinder Pressure Sensor Having Improved Response Characteristics
”, US Patent 5,367,904, (
1994
).
13.
Sawamoto
,
K.
, “
Combustion Pressure Sensor Arrangement
”, US Patent 4,602,506, (
1986
).
14.
L.
Romani
,
A.
Bianchini
,
G.
Vichi
,
A.
Bellissima
and
G.
Ferrara
, “
Experimental assessment of a methodology for the indirect in-cylinder pressure evaluation in four-stroke internal combustion engines
”,
Energies
, Volume
11
issue
8
,
1982
, (2018); DOI:
15.
Woschni
,
G.
, “
A Universally Applicable Equation for the Instantaneous Heat Transfer Coefficient in the Internal Combustion Engine
”, SAE Paper 670931; DOI:
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