PIV Investigation of the Intake Flow in a Parallel Valves Diesel Engine Cylinder Jean APA Rabault

122 Pages·2015·25.04 MB·English

PIV Investigation of the Intake Flow in a
Parallel Valves Diesel Engine Cylinder
by
Jean A. P. A. Rabault
January 2015
Technical Reports from
Royal Institute of Technology
KTH Mechanics
SE-100 44 Stockholm, Sweden
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Preface
The present Master thesis work was performed between July and December 2014
as part of a Double Degree diploma between E´cole Polytechnique, Palaiseau France
and KTH, Stockholm. The work was carried out as a collaboration between KTH
Mechanics department and the group in charge of Gas Exchange Specification and
Simulation at Scania CV AB located in So¨dert¨alje, Sweden.
January 2015, Stockholm
Jean A. P. A. Rabault
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J.A.P.A. Rabault PIV study of the Intake Flow in a Diesel Engine Cylinder
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JeanA.P.A.Rabault2015, PIV Investigation of the Intake Flow in a Parallel
Valves Diesel Engine Cylinder
KTH Mechanics, SE–100 44 Stockholm, Sweden
Abstract
Preliminary designs for the cylinder heads of Scania’s next generation Diesel Engine
have been investigated by the means of PIV measurements on a steady test rig.
General structures present in the flow have been investigated, with a specific focus
on Swirl motion due to its well documented impact on combustion e�ciency and
pollutiongeneration. Thefirstsetofmeasurementswasacquiredinthetumbleplane.
A method to perform e�ciently PIV measurements was introduced, which consists
in rotating the experimental setup rather than the PIV measurement instruments.
As a consequence, a considerable amount of work is saved and a great number of
measurement planes can be acquired. This method has allowed to reconstruct a
3D3C picture of the flow in the cylinder. Such 3D3C direct measurement of flow
in a test rig cylinder had not been reported previously in the literature, as far as
the author is aware of it. The second set of measurements was acquired in the swirl
plane. General patterns in the swirl velocity fields have been identified. The author
introduces the hypothesis that shifting down the measurement position may, to some
extend, beequivalenttoobservingtheflowevolveintimeintherealenginesituation.
Measurement performed far enough under thevalvesexhibit clear and stableswirling
vortex structure with the cylinder heads investigated. This may explain for the
validity of the combustion models used in the industry that, despite apparent over
simplification of the flow situation, have proved in good agreement with engine tests.
Descriptors: Admissionstroke,Flowincylinder,Swirlmotion,Admissionchannels.
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J.A.P.A. Rabault PIV study of the Intake Flow in a Diesel Engine Cylinder
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J.A.P.A. Rabault PIV study of the Intake Flow in a Diesel Engine Cylinder
Contents
1 Introduction 7
1.1 Introduction: need for Diesel engine improvement . . . . . . . . . . . 7
1.2 Development of Scania’s next generation engine . . . . . . . . . . . . 8
1.3 Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Engine and flow background 10
2.1 Direct injection diesel engines . . . . . . . . . . . . . . . . . . . . . . 10
2.1.1 Strokes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1.2 Engine e�ciency . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.3 Swirl and Tumble . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1.4 Flow coe�cient . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Combustion process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Flow inside a cylinder. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3.1 Compressible Navier-Stokes equation . . . . . . . . . . . . . . 17
2.3.2 Incompressible Navier-Stokes equation . . . . . . . . . . . . . 19
2.3.3 RANS decomposition and turbulence . . . . . . . . . . . . . . 19
2.3.4 Energy cascade and turbulence . . . . . . . . . . . . . . . . . 21
2.3.5 Anisotropy map . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3 Measurement technique, experimental configuration and post pro-
cessing methods 23
3.1 Mono and Stereo PIV. . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.1.1 PIV overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.1.2 Correlation technique . . . . . . . . . . . . . . . . . . . . . . . 24
3.1.3 Choice of the particles . . . . . . . . . . . . . . . . . . . . . . 25
3.1.4 PIV configuration and Stereo reconstruction . . . . . . . . . . 28
3.1.5 Basic optics considerations and image quality . . . . . . . . . 30
3.1.6 Scheimpflug criterion . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 Experimental setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2.1 Test rig and cylinder head . . . . . . . . . . . . . . . . . . . . 32
3.2.2 Measurement configurations . . . . . . . . . . . . . . . . . . . 32
3.2.3 Laser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.4 Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.2.5 Pollution by particle deposition . . . . . . . . . . . . . . . . . 36
3.2.6 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.7 �t optimization . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2.8 Software used and processing principles . . . . . . . . . . . . . 39
3.2.9 Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.2.10 Assessment of polariser film as a way to diminish reflections
intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.3 Order of magnitude analysis of the flow in the experimental cylinder . 45
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J.A.P.A. Rabault PIV study of the Intake Flow in a Diesel Engine Cylinder
3.3.1 Overall engine parameters . . . . . . . . . . . . . . . . . . . . 45
3.3.2 Order of magnitude estimates of turbulence evolution during
engine cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.4 Method for obtaining 3D3C information from tumble plane measure-
ments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.5 Post-processing techniques . . . . . . . . . . . . . . . . . . . . . . . . 47
3.5.1 Considerations about RMS analysis . . . . . . . . . . . . . . . 48
3.5.2 Streamlines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.5.3 Proper Orthogonal Decomposition (POD) . . . . . . . . . . . 49
3.5.4 Singular Value Decomposition (SVD) . . . . . . . . . . . . . . 51
3.5.5 Dynamic Mode Decomposition (DMD) . . . . . . . . . . . . . 52
3.5.6 General considerations for use of POD and DMD . . . . . . . 53
3.5.7 Other general flow analysis techniques . . . . . . . . . . . . . 54
3.5.8 Specificflowanalysistechnique: instantaneousswirlcentreiden-
tification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.6 Uncertainty analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.6.1 Confidence intervals and outliers . . . . . . . . . . . . . . . . 55
3.6.2 Time sampling of autocorrelated signals . . . . . . . . . . . . 58
3.7 Measurements of swirl, tumble and flow coe�cients in test bench . . . 60
4 Results and discussion 63
4.1 Measurement cases performed . . . . . . . . . . . . . . . . . . . . . . 63
4.2 Quality assessment and uncertainty analysis . . . . . . . . . . . . . . 64
4.2.1 Quality of recorded and processed data . . . . . . . . . . . . . 66
4.2.2 Uncertainty analysis . . . . . . . . . . . . . . . . . . . . . . . 66
4.2.3 Anisotropy map . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.3 Results from tumble plane measurements: one plane data . . . . . . . 68
4.3.1 Mean quantities . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.3.2 POD modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.4 Results from tumble plane measurements: 3D3C reconstruction . . . 74
4.5 Results from Swirl plane measurement . . . . . . . . . . . . . . . . . 77
4.5.1 Mean quantities . . . . . . . . . . . . . . . . . . . . . . . . . . 77
4.5.2 Instantaneous swirl center position . . . . . . . . . . . . . . . 81
4.5.3 POD modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.6 Discussion of the results . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.6.1 Agreement between di↵erent measurements and general flow
features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
4.6.2 Regularisation with lower position and turbulence comparison
with theory: hypothesis of similarities between evolution with
time in the engine and lower vertical position in the test bench 85
4.6.3 Radial velocity profile in central swirl structure . . . . . . . . 88
4.6.4 Flow analysis by means of artificial velocity profiles . . . . . . 90
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J.A.P.A. Rabault PIV study of the Intake Flow in a Diesel Engine Cylinder
4.6.5 2D divergence and local vorticity . . . . . . . . . . . . . . . . 91
4.6.6 Higher order derivatives: analysis of Navier-Stokes equation
terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.6.7 Comparisons with other works . . . . . . . . . . . . . . . . . . 98
5 Summary and suggestion for future work 100
6 Acknowledgements - Tack 101
7 Bibliography 102
8 Appendix 1: Exhaustive swirl plane measurements 108
9 Appendix 2: Comparison between the swirling structures obtained
in HSC and LSC 119
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