Thermal investigations on a high-speed direct injection diesel engine

Papaioannou, N

Abstract:: Modern compression ignition engines offer higher thermal efficiency compared to gasoline engines, thus offering superior fuel consumption performance and lower CO₂ emissions, a major greenhouse gas. With future legislation pushing the automotive manufacturers for even lower fleet average CO₂ emissions the compression ignition engine can assist in achieving these goals, however further research is required to extend their efficiency.

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APA Style

Papaioannou, N. (2018). Thermal investigations on a high-speed direct injection diesel engine [PhD thesis]. University of Oxford.

MLA Style

Papaioannou, N. Thermal Investigations on a High-Speed Direct Injection Diesel Engine. 2018. University of Oxford, PhD thesis.

Chicago Style

Papaioannou, N. 2018. “Thermal Investigations on a High-Speed Direct Injection Diesel Engine.” PhD thesis, University of Oxford.
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Files:: Papaioannou_2018_Thermal_investigations_on.pdf

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Authors

+ Papaioannou, N More by this author

Division:: MPLS
Department:: Engineering Science
Role:: Author

Contributors

+ Davy, M

Role:: Supervisor

+ Jaguar Land Rover More from this funder

+ Engineering & Physical Sciences Research Council More from this funder

DOI:: 10.5287/ora-yrpyjznbj
Type of award:: DPhil
Level of award:: Doctoral
Awarding institution:: University of Oxford

Language:: English
Keywords:: temperature measurements

diesel engines

energy balance
Subjects:: Internal combustion engines
UUID:: uuid:86cae955-8bba-4e19-8b25-61090ebe6998
Deposit date:: 2019-05-30
ARK identifier:: ark:/29072/ora_86cae9558bba4e198b2561090ebe6998

Related item:: Effect of thermocouple size on the measurement of exhaust gas temperature in internal combustion engines
Description:: Accurate measurement of exhaust gas temperature in internal combustion engines is essential for a wide variety of monitoring and design purposes. Typically these measurements are made with thermocouples, which may vary in size from 0.05 mm (for fast response applications) to a few millimetres. In this work, the exhaust of a single cylinder diesel engine has been instrumented both with a fast-response probe (comprising of a 50.8 μm, 127 μm and a 254 μm thermocouple) and a standard 3 mm sheathed thermocouple in order to assess the performance of these sensors at two speed/load conditions. The experimental results show that the measured time-average exhaust temperature is dependent on the sensor size, with the smaller thermocouples indicating a lower average temperature for both speed/load conditions. Subject to operating conditions, measurement discrepancies of up to ~80 K have been observed between the different thermocouples used. Thermocouple modelling supports the experimental trends and shows that the effect of conduction is inversely proportional to the thermocouple junction size-an effect attributed to changes in the thermal inertia of the device. This conduction error is not typically considered in the literature for exhaust gas temperature measurement. Modelling results also show that radiative heat transfer is small compared to the effect of conduction on the measurements. Finally, a new dynamic response thermocouple compensation method is presented, in order to correct for the dynamic error induced by the thermocouples. This technique recovers the “true” gas temperature with a maximum error of ~1.5-2% in peak temperature depending on speed/load conditions.
Related item:: Thermal analysis of steel and aluminium pistons for an HSDI diesel engine
Description:: Chromium-molybdenum alloy steel pistons, which have been used in commercial vehicle applications for some time, have more recently been proposed as a means of improving thermal efficiency in light-duty applications. This work reports a comparison of the effects of geometrically similar aluminium and steel pistons on the combustion characteristics and energy flows on a single cylinder high-speed direct injection diesel research engine tested at two speed / load conditions (1500 rpm / 6.9 bar nIMEP and 2000 rpm/25.8 bar nIMEP) both with and without EGR. The results indicate that changing to an alloy steel piston can provide a significant benefit in brake thermal efficiency at part-load and a reduced (but non-negligible) benefit at the high-load condition and also a reduction in fuel consumption. These benefits were attributed primarily to a reduction in friction losses. In terms of energy transfer, switching to the steel piston design was shown to reduce heat transfer to the coolant, consistent with lower friction work and reduced conduction through the ring pack, and increase the energy transfer to the oil. Piston blowby was also greatly reduced. Ignition delay times and overall combustion durations were reduced with the steel piston design, possibly indicative of higher piston surface temperatures.
Related item:: Evaluation of exhaust gas recirculation techniques on a high-speed direct injection diesel engine using first law analysis
Description:: The effects of different exhaust gas recirculation (EGR) strategies on engine efficiency and the resulting energy flows at two speed/load conditions (1500 r/min/6.8 bar net indicated mean effective pressure (nIMEP) and 1750 r/min/13.5 bar nIMEP) were studied using a first law analysis approach. The EGR strategies tested were as follows: cooled high-pressure exhaust gas recirculation (baseline), the application of exhaust gas recirculation with the swirl flap closed and the use of exhaust gas recirculation under constant λ conditions. The closed swirl flap exhaust gas recirculation strategy reduced brake efficiency under high load conditions and increased heat transfer to the coolant for both load cases. Soot and CO emissions increased at high load, however, with an increase in NOx relative to the baseline case. The constant λ exhaust gas recirculation strategy reduced brake efficiency under low load, as well as the heat flow to the coolant for both load cases. The constant λ exhaust gas recirculation strategy benefited smoke emissions and increased combustion exhaust gas recirculation tolerance, albeit with a penalty in NOx emission.

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Copyright holder:: Papaioannou, N

Licence:: Terms and Conditions of Use for Oxford University Research Archive

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Thermal investigations on a high-speed direct injection diesel engine

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