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Experiments on Heat Transfer During Diesel Combustion Using Optical Methods
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. Scania CV AB.ORCID iD: 0000-0002-1003-0700
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transportation is a crucial part of modern societies. This includes their economies. Trade and the transportation of goods have a great influence on prosperity. Nevertheless, the transportation sector with road transport in particular is heavily dependent on fossil fuels and emits a significant amount of greenhouse gases. One approach to mitigate the negative environmental impact of road transport is to increase the efficiency of its most common propulsion system, that is the internal combustion engine. Due to its dominant role in the road freight transportation sector, this thesis directs its attention to heavy-duty diesel engines. In-cylinder heat losses are one of the main factors that reduce engine efficiency. Therefore, the objective of this thesis is to gain a better understanding of the processes that influence in-cylinder heat losses by resolving them in time and space using optical methods. In diesel engines, most of the in-cylinder heat losses are transferred to the piston. As a result, this thesis focuses specifically on that component.

In this research project, the task to determine in-cylinder heat losses to the piston in heavy-duty diesel engines is divided into two parts. The most important part consists of fast surface temperature measurements on the piston using phosphor thermometry. The heat transfer coefficient inside the piston cooling gallery defines an additional steady-state boundary condition.

The work presented in this thesis includes therefore efforts to improve in-cylinder surface temperature measurements and an assessment of their accuracy and precision. Furthermore, it comprises of experimental results from measurements on steel pistons and a piston with an insulating thermal barrier coating. Results reveal spatial differences of the heat transfer during diesel combustion. Measurements at the impingement point indicate a strong influence of flame impingement on local heat transfer. A correlation is detected between heat transfer and cycle-to-cycle variations of flame impingement.

The thesis also reports efforts to determine the heat transfer coefficient inside the piston cooling gallery. Using an infrared camera a method is presented to spatially resolve convective heat transfer inside this cooling channel.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 131
Series
TRITA-ITM-AVL ; 2019:23
Keywords [en]
Heat transfer, Internal combustion engines, Phosphor thermometry
National Category
Other Mechanical Engineering
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-255657ISBN: 978-91-7873-263-0 (print)OAI: oai:DiVA.org:kth-255657DiVA, id: diva2:1340516
Public defence
2019-09-20, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency, 38370-1
Note

QC 20190806,

Available from: 2019-08-30 Created: 2019-08-05 Last updated: 2019-09-02Bibliographically approved
List of papers
1. Heat Loss Analysis of a Steel Piston and a YSZ Coated Piston in a Heavy-Duty Diesel Engine Using Phosphor Thermometry Measurements
Open this publication in new window or tab >>Heat Loss Analysis of a Steel Piston and a YSZ Coated Piston in a Heavy-Duty Diesel Engine Using Phosphor Thermometry Measurements
Show others...
2017 (English)In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, no 4, p. 1954-1968Article in journal (Refereed) Published
Abstract [en]

Diesel engine manufacturers strive towards further efficiency improvements. Thus, reducing in-cylinder heat losses is becoming increasingly important. Understanding how location, thermal insulation, and engine operating conditions affect the heattransfer to the combustion chamber walls is fundamental for the future reduction of in-cylinder heat losses. This study investigates the effect of a 1mm-thick plasma-sprayed yttria-stabilized zirconia (YSZ) coating on a piston. Such a coated piston and a similar steel piston are compared to each other based on experimental data for the heat release, the heat transfer rate to the oil in the piston cooling gallery, the local instantaneous surface temperature, and the local instantaneous surface heat flux. The surface temperature was measured for different crank angle positions using phosphor thermometry. The fuel was chosen to be n-heptane to facilitate surface temperature measurements during non-skip-fire, thermally stabilized operating conditions. Assuming one-dimensional heat transfer inside each piston, the local instantaneous surface heat flux was calculated using the heat transfer rate to the oil in the piston cooling gallery and the surface temperature measurements. The results from this study show that the surface temperature variation is similar for both pistons. The instantaneous heat flux during combustion is however significantly greater for the steel piston than the coated piston. The heat release analysis also indicates that combustion is slower for the piston with the yttria-stabilized zirconia coating.

Place, publisher, year, edition, pages
SAE International, 2017
Keywords
phosphor thermometry; heat losses; diesel engines; thermal barrier coating; TBC
National Category
Vehicle Engineering Energy Engineering
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-254606 (URN)10.4271/2017-01-1046 (DOI)000416807900053 ()2-s2.0-85018343474 (Scopus ID)
Projects
Heat losses during diesel combustion
Funder
Swedish Energy Agency, 38370-1
Note

QC 20190806

Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-08-06Bibliographically approved
2. Experimental Determination of the Heat Transfer Coefficient in Piston Cooling Galleries
Open this publication in new window or tab >>Experimental Determination of the Heat Transfer Coefficient in Piston Cooling Galleries
2018 (English)In: SAE Technical Papers, ISSN 0148-7191Article in journal (Refereed) Published
Abstract [en]

Piston cooling galleries are critical for the pistons’ capability to handle increasing power density while maintaining the same level of durability. However, piston cooling also accounts for a considerable amount of heat rejection and parasitic losses. Knowing the distribution of the heat transfer coefficient (HTC) inside the cooling gallery could enable new designs which ensure effective cooling of areas decisive for durability while minimizing parasitic losses and overall heat rejection. In this study, an inverse heat transfer method is presented to determine the spatial HTC distribution inside the cooling gallery based on surface temperature measurements with an infrared (IR) camera. The method utilizes a piston specially machined so it only has a thin sheet of material of a known thickness left between the cooling gallery and the piston bowl. The piston - initially at room temperature - is heated up with warm oil injected into the cooling gallery. The transient of the piston’s outer surface temperature is captured with an IR camera from the top. Combining the temperature transient of each pixel, the HTC is later obtained through an inverse heat transfer solver based on one-dimensional heat conduction inside the piston material. To the authors’ knowledge, the current study presents the first application of an inverse heat transfer method for spatially resolved and experimentally determined heat transfer coefficients inside a piston cooling gallery. Preliminary measurements at standstill to demonstrate the method display an area of increased heat transfer where the entering oil jet impinges onto the wall of the cooling gallery.

Place, publisher, year, edition, pages
Heidelberg, Germanay: , 2018
Keywords
Piston cooling gallery, IR camera, Heat transfer coefficient
National Category
Energy Engineering Fluid Mechanics and Acoustics Vehicle Engineering
Research subject
Engineering Mechanics; Energy Technology
Identifiers
urn:nbn:se:kth:diva-254662 (URN)10.4271/2018-01-1776 (DOI)2-s2.0-85056842855 (Scopus ID)
Conference
SAE 2018 International Powertrains, Fuels and Lubricants Meeting, FFL 2018; Heidelberg; Germany; 17 September 2018 through 19 September 2018
Projects
Heat
Note

QC 20190806

Available from: 2019-07-03 Created: 2019-07-03 Last updated: 2019-10-14Bibliographically approved
3. Study on heat losses during flame impingement in a diesel engine using phosphor thermometry surface temperature measurements
Open this publication in new window or tab >>Study on heat losses during flame impingement in a diesel engine using phosphor thermometry surface temperature measurements
2019 (English)In: SAE Technical Papers, ISSN 0148-7191Article in journal (Refereed) Published
Abstract [en]

In-cylinder heat losses in diesel engines decrease engine efficiency significantly and account for approximately 14-19% [1, 2, 3] of the injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the flame impingement onto the piston. Therefore, the present study investigates the heat losses during flame impingement onto the piston bowl wall experimentally. The measurements were performed on a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the flame was determined by evaluating a phosphor's temperature dependent emission decay. Simultaneous cylinder pressure measurements and high-speed videos are associated to the surface temperature measurements in each cycle. Thus, surface temperature readings could be linked to specific impingement and combustion events. The results showed a sharp increase of the surface temperature during the flame impingement and an abrupt decrease as the flame disappeared.

Place, publisher, year, edition, pages
Detroit, United States: SAE International, 2019
Keywords
Phosphor thermometry; diesel engine; heat losses; flame impingement
National Category
Energy Engineering Vehicle Engineering
Research subject
Energy Technology; Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-254622 (URN)10.4271/2019-01-0556 (DOI)2-s2.0-85064646818 (Scopus ID)
Conference
SAE World Congress Experience, WCX 2019; Cobo CenterDetroit; United States; 9 April 2019 through 11 April 2019
Projects
Heat losses during CI combustion
Funder
Swedish Energy Agency, 38370-1
Note

QC 20190806

Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-08-06Bibliographically approved
4. Comparison of heat losses at the impingement point and in between two impingement points in a diesel engine using phosphor thermometry
Open this publication in new window or tab >>Comparison of heat losses at the impingement point and in between two impingement points in a diesel engine using phosphor thermometry
2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In-cylinder heat losses in diesel engines reduce engine efficiency significantly and account for a considerable amount of injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the impingement of the flame. The present study compares the heat losses at the point where the flame impinges onto the piston bowl wall and the heat losses between two impingement points. Measurements were performed in a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the combusting diesel spray and at a point in between two impingement points was determined using phosphor thermometry. The dynamic heat fluxes and the heat transfer coefficients which result from the surface temperature measurements are estimated. Simultaneous cylinder pressure measurements and high-speed videos are associated to individual surface temperature measurements. Thus each surface temperature measurement is linked to a specific impingement and combustion events. An analysis of the surface temperature in connection with the high speed images reveals the great impact of flame impingement on instantaneous local heat flux at the impingement point. Absence of such an effect in between two impingement points implies an inhomogeneous temperature field.

Place, publisher, year, edition, pages
Kyoto, Japan: , 2019
Keywords
Phosphor thermometry, diesel engines, heat losses, flame impingement
National Category
Energy Engineering Vehicle Engineering
Research subject
Energy Technology; Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-254626 (URN)
Conference
JSAE/SAE 2019 International Powertrains, Fuels and Lubricants Meeting, August 26 - 29 2109
Projects
Heat losses during CI combustion
Funder
Swedish Energy Agency, 38370-1
Note

QC 20190819

Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-08-06Bibliographically approved
5. Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines
Open this publication in new window or tab >>Phosphor Thermometry for In-Cylinder Surface Temperature Measurements in Diesel Engines
2019 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501Article in journal (Other academic) Submitted
Abstract [en]

Surface temperature measurements in technically relevant applications can be very  hallenging and yet of great importance. Phosphor thermometry is a temperature measurement technique that has previously been employed in technically relevant applications to obtain surface temperature. The technique is based on temperature-dependent changes in a phosphor’s luminescence. To improve the accuracy and precision of temperature measurements with this technique, the present study considers, by way of example, the impact of conditions inside the cylinder of a diesel engine on decay time based phosphor thermometry. After an initial, general assessment of the effect of prevailing measurement conditions, this research investigates errors caused by soot luminosity, extinction, signal trapping and changes of phosphors’ luminescence properties due to exposure to the harsh environment. Furthermore, preferable properties of phosphors which are suitable for in-cylinder temperature measurements are discussed. 16 phosphors are evaluated, including four which – to the authors’ knowledge –have previously not been used in thermometry. Results indicate that errors due to photocathode bleaching, extinction, signal trapping and changes of luminescence properties may cause an erroneous temperature evaluation with temperature errors in the order of serval tens of Kelvin.

Keywords
phosphor thermometry, temperature measurement, diesel engine, phosphor
National Category
Energy Engineering Aerospace Engineering Vehicle Engineering Other Mechanical Engineering
Research subject
Energy Technology; Physics; Vehicle and Maritime Engineering
Identifiers
urn:nbn:se:kth:diva-254922 (URN)
Projects
Heat losses during CI combustion
Funder
Swedish Energy Agency, 38370-1Swedish Research Council, 2017-02974
Note

QC 20190806

Available from: 2019-07-09 Created: 2019-07-09 Last updated: 2019-08-06Bibliographically approved

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