The Characteristics of Instantaneous Angular Speed of Diesel Engines for Fault Diagnosis

279 Pages·2017·6.68 MB·English

The Characteristics of Instantaneous Angular Speed
of Diesel Engines for Fault Diagnosis

Misan Madamedon

A thesis submitted to the University of Huddersfield in partial fulfilment of the requirements for
the degree of
Doctor of Philosophy

Department of Mechanical Engineering
School of Computing and Engineering
University of Huddersfield

September 2017

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ABSTRACT
Early fault detection and diagnosis of diesel engines are paramount now, especially with countries
like the UK and France, in-line with the 2015 Paris agreement on climate change, making plans to
ban the use of an automobile with diesel and petrol engines before the year 2040. This ban could
affect other sectors where diesel engines are the prime mover and result in more stringent exhaust
emission regulations. The instantaneous angular speed (IAS) model based fault diagnosis has
shown more prospects of fault detection and location. However, there are serious gaps in available
knowledge regarding IAS model based fault diagnosis which takes into account the effect of the
system’s modal properties. Hence, this research focuses on the online modal properties
identification of a typical engine-load system for an improved performance of IAS based fault
diagnosis.

Having acknowledged the essentials of IAS based fault diagnosis techniques through a
comprehensive literature study, this research firstly investigates the impact of modal properties on
the IAS of a four-cylinder engine. This is achieved through a three degree of freedom (DOF)
torsional vibration model of the engine-load system, which allows for the modal properties of the
system to be calculated and analysed. The calculated modal properties of the system showed one
rigid and two flexible modes which had a low (<13Hz) and high (<92Hz) frequencies. The mode
shape of the low frequency resonance shows more amplitude on the flywheel-load reference point
of the system while that of the high frequency resonance shows more amplitude on the engine-
flywheel reference point of the system. It then simulated the IAS which represents the torsional
vibration signature with altered modal properties. The simulated result demonstrated that the low
frequency resonance is more sensitive to the peak and trough values of the IAS waveform.

After identifying the deployment merits of operational modal analysis (OMA) techniques through
a comprehensive literature study, this research then explore the prospect of an IAS based output-
only modal properties identification of a typical engine-load system. This was done through both
experimental and simulation evaluations, which allowed simulated and experimental IAS to be
used for implementing covariance-driven reference based stochastic subspace identification (SSI).
The simulated result using pseudo-random input shows that the identified resonance frequencies
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and mode shapes are 80% correlated with the calculated ones. The simulation results also
demonstrated that the accuracy of the identified modal properties is dependent on the number of
IAS responses used for implementing the covariance-driven reference based SSI technique. The
experimental result using estimated IAS during engine shutdown operation showed that both high
and low frequency vibration mode can be identified. The identified resonance frequencies with
their mode shapes are 80% correlated with the predicted ones.

Having identified the modal properties of the engine-load system online through the
implementation of an IAS based covariance-driven SSI, this research then investigates the impact
of misfire on the system’s modal properties especially the mode shape of the low frequency
resonance. This was achieved experimentally by inducing a complete misfire in respective
cylinders (1st, 3rd and 4th) and the IAS estimated during engine’s transient shutdown operation was
used for implementing a covariance-driven reference based stochastic subspace modal properties
identification. While the mode shape of the identified high frequency resonance (<80Hz) showed
no characteristics for cylinder misfire detection, that of the low frequency resonance (<13Hz) did.

Faults in the engine’s injection system and an abnormal clearance valve train conditions
significantly affects its combustion process. The cylinder by cylinder pressure torque obtained
from measured IAS through order domain deconvolution technique can be used to detect and
diagnose injection faults. In the interim, this research has also recognised that the closer the low-
resonance frequency of the model used for the order domain deconvolution gets to its real time
value the more accurate the pressure torque becomes. The reconstructed pressure torque which
takes into consideration the real time low frequency resonance can be used to detect faulty injection
system with different severities and abnormal clearance valve conditions of several severities.
Furthermore, the importance of an accurate modal properties utilisation in IAS model based fault
diagnosis of a four-cylinder diesel engine is shown.

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Declaration
No portion of this work referred to in this thesis has been submitted in support of an application
for another degree or qualification of this or any other university or another institute of learning.
Misan Madamedon

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Acknowledgement
I would give all the praise and glory to the almighty God who has given me good health and
strength to the complete this work all through my study period.

My unreserved gratitude goes to my supervisory team which comprises of the director of studies
University of Huddersfield Prof. Andrew David Ball and Dr Fengshou Gu for the continuous
support, motivation, encouragement, advice, guidance and supervision which they expressed
towards me all through my years of study. Their constant direction and doors open for discussions
anytime were of great help to me all through my years of study. I really appreciate their effort and
contribution towards this research and couldn’t have asked for any other team than them both.
To the team leader of the automotive lab Martin Gargett, I want to say without you the experiment
conducted in this research would not have come to a realization. I cannot thank you enough for the
help you rendered all through the experimental stage of this research. My special thanks to the
Nigerian government represented by the Office of the Special Adviser on Niger Delta Affairs
(OSPNDA) for proving me with the required funding for this research. I would like to appreciate
my parents Mr and Mrs Louis Madamedon for their encouragement all through the period of my
research.
Most of all I would like to appreciate my adorable and beautiful wife Abiola Madamedon for her
patience, love and care all through the years of my research. And I cannot forget my two lions
Jeremiah and Isaiah Madamedon who are priceless jewels of joy to me.
To all my friends at the Centre for Efficiency and Performance Engineering (CEPE) research
group Ugo, Osama, Naima, Zainab, Yuandong and others I want to say a big thank you for their
input one way or the other in this research.

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List of Contents
ABSTRACT .................................................................................................................................... 1
Declaration ...................................................................................................................................... 3
Acknowledgement .......................................................................................................................... 4
List of Contents ............................................................................................................................... 5
List of Figures ............................................................................................................................... 13
List of Tables ................................................................................................................................ 19
List of Abbreviations .................................................................................................................... 21
List of Publications ....................................................................................................................... 25
List of Notations ........................................................................................................................... 26
CHAPTER ONE ........................................................................................................................... 30
INTRODUCTION ................................................................................................................. 30
Introduction to Condition Monitoring ............................................................................ 31
Research Background and Motivation ........................................................................... 32
Focus of this Thesis ................................................................................................ 33
Research Aims and Objectives ............................................................................... 33
Thesis Structure and Organization ................................................................................. 34
CHAPTER TWO .......................................................................................................................... 36
DIESEL ENGINES AND CONDITION MONITORING .................................................... 36
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Introduction .................................................................................................................... 37
Engine Valve and Injection System ............................................................................... 40
Diesel Engine Valve Operation System .................................................................. 40
Diesel Engine Fuel Injection System ...................................................................... 42
Review of Principal Faults in Diesel Engines ................................................................ 44
Condition Monitoring and Fault Diagnosis (CMFD) for Diesel Engines: An Overview
45
Visual Inspection Monitoring ................................................................................. 46
Lubrication Oil Analysis Monitoring...................................................................... 46
Cylinder Pressure Monitoring ................................................................................. 46
Vibration Monitoring .............................................................................................. 47
Acoustic Monitoring ............................................................................................... 48
Exhaust Pressure Monitoring .................................................................................. 48
Key Findings .................................................................................................................. 48
CHAPTER THREE ...................................................................................................................... 50
OVERVIEW OF IAS Measurement ...................................................................................... 50
Introduction .................................................................................................................... 51
Instantaneous Angular Speed (IAS) Monitoring ............................................................ 52
Signal Based Diagnosis........................................................................................... 53
Model Based Fault Diagnosis ................................................................................. 54
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Modelling the IAS Generation Process .......................................................................... 57
Measurement Principle ........................................................................................... 57
IAS Encoder Signal................................................................................................. 59
IAS Signal Denoising ............................................................................................. 61
IAS Estimation Techniques .................................................................................... 63
IAS Measurement Performance Parameters and Analysis ............................................. 69
Minimum Measurable Speed .................................................................................. 69
Maximum Measurable Speed ................................................................................. 70
Measurement Error ................................................................................................. 70
Key Findings .................................................................................................................. 70
CHAPTER FOUR ......................................................................................................................... 72
EXPERIMENTAL FACILITIES AND INSTRUMENTATION ......................................... 72
Experimental Engine-Dynamometer System ................................................................. 73
Test Engine ............................................................................................................. 74
Flexible Coupling.................................................................................................... 78
Instrumentation............................................................................................................... 78
Cylinder Pressure Sensor ........................................................................................ 79
Encoders .................................................................................................................. 80
Data Acquisition Hardware and Software .............................................................. 83
Test Procedures and Fault Simulation ............................................................................ 84
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Engine Test Procedure ............................................................................................ 85
Injection System Fault Simulation .......................................................................... 87
Abnormal Valve Clearance Simulation .................................................................. 89
Key Findings .................................................................................................................. 90
CHAPTER FIVE .......................................................................................................................... 92
MODELS OF ENGINE DRIVELINE TORSIONAL VIBRATION .................................... 92
Introduction .................................................................................................................... 93
Engine Geometry............................................................................................................ 93
Engine Driveline Model ................................................................................................. 96
Numerical Model .................................................................................................... 97
Model Size Reduction ............................................................................................. 97
Damped Eigenvalues and Eigenvectors ................................................................ 101
Continuous-Time State-Space Models ................................................................. 103
Discrete-Time State Space Models ....................................................................... 107
Key Findings ................................................................................................................ 109
CHAPTER SIX ........................................................................................................................... 110
SIMULATION AND VALIDATION OF MODEL ........................................................... 110
Introduction .................................................................................................................. 111
Engine-Dynamometer Simulation Program ................................................................. 111
Torsional Modal Properties................................................................................... 112
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