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Investigation of engine design parameters on the efficiency and performance of the high specific power downsized SI engine
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.This study investigates the impact of employing the Miller cycle on a high specific
power downsized gasoline engine by means of Early Intake Valve Closing (EIVC) and
Late Intake Valve Closing (LIVC). This investigation assesses the potential for the Miller
cycle to improve fuel economy at part load points, as well as high load points with
significantly elevated boost pressures (Deep Miller) of up to 4 bar abs. The impact of
geometric Compression Ratio (CR) and Exhaust Back Pressure (EBP) has also been
investigated. The knock mitigating qualities of Deep Miller have been assessed, and its
ability to increase maximum engine load explored. Low Speed Pre-ignition (LSPI) and
autoignition tendencies with reduced coolant flow rates and with aged and new fuels
have also been studied. This study comprises both experimental and analytical studies. A Ricardo Hydra single
cylinder thermodynamic engine was developed and used for the experimental
component of the study. This engine features a high specific power output (120kW/l)
cylinder head from the Mahle 1.2l 3 cylinder aggressively downsized engine. The
analytical component was carried out using a 1-dimensional GT-Power model based on
the Ricardo Hydra experimental engine. A Design of Experiments (DoE) based test plan
was adopted for this analytical study. The experimental study found that EIVC was the optimal strategy for improving fuel economy at both part-load and high-load conditions. LIVC yielded a fuel economy
penalty at part-load operations and a fuel economy improvement at high-loads. The unexpected part-load LIVC result was attributed to the engine breathing dynamics of the experimental engine. The analytical study found moderate LIVC to be the optimal strategy at lower speeds, unless compensation for the increased degree of scavenging experienced with EIVC was compensated for, in which case EIVC was optimum. At
higher speeds EIVC was found to be optimum regardless of whether or not compensation for scavenging was employed. It was generally found that less sensitivity to EBP was exhibited the more extreme the EIVC and LIVC. It was also found that a higher geometric CR could be tolerated with extreme EIVC and LIVC, and a fuel
economy benefit could be obtained through the elevation of Geometric CR
CO2 reduction through low cost electrification of the diesel powertrain at 48V
In order to achieve fleet average CO2 targets, mass market adoption of low CO2 technologies is required. Application of low cost technologies across a large number of vehicles is more cost-effective in reducing fleet CO2 than deploying high-impact, costly technology to a few. Therefore, to meet the CO2 reduction challenge, commercially viable, low cost technologies are of significant interest. This paper presents results from the ‘ADEPT’ collaborative research program which focuses on CO2 reduction through the application of intelligent 48V electrification to diesel engines for passenger car applications. Results were demonstrated on a C-segment vehicle with a class-leading 4-cylinder 1.5 litre Euro 6 diesel engine. Electrification was applied through a high power, high efficiency, switched reluctance belt integrated starter generator (B-ISG) capable of both generation and motoring, and an Advanced Lead Carbon Battery for energy storage. The conventional alternator was replaced with a highly efficient DC-DC converter to supply energy to the 12V system. These technologies enabled powertrain efficiency improvement through the recovery of kinetic energy with regenerative braking and reapplication of the recovered energy through motoring to offset fuel usage. Efficiency was further optimised through application of engine downspeeding and advanced auto-stop strategies to extended engine-off time. Additional electrification was investigated through 48V ancillaries, including water-pump and air-conditioning compressor, and a turbo-compound generator for waste heat recovery from exhaust gas. These technologies have demonstrated a combined CO2 reduction of 10–11% against the conventional vehicle baseline. Additional studies of advanced thermal systems for improved warm-up, and lubrication control for FMEP reduction have also been conducted on this program. These indicate that by applying intelligent electrification to ancillaries a further 3–4% reduction in CO2 is achievable. Overall, this program shows that 48V technologies can achieve CO2 savings with a lower cost per gram CO2 than full hybrid solutions
CO2 reduction through low cost electrification of the diesel powertrain at 48V
In order to achieve fleet average CO2 targets, mass market adoption of low CO2 technologies is required. Application of low cost technologies across a large number of vehicles is more cost-effective in reducing fleet CO2 than deploying high-impact, costly technology to a few. Therefore, to meet the CO2 reduction challenge, commercially viable, low cost technologies are of significant interest. This paper presents results from the ‘ADEPT’ collaborative research program which focuses on CO2 reduction through the application of intelligent 48V electrification to diesel engines for passenger car applications. Results were demonstrated on a C-segment vehicle with a class-leading 4-cylinder 1.5 litre Euro 6 diesel engine. Electrification was applied through a high power, high efficiency, switched reluctance belt integrated starter generator (B-ISG) capable of both generation and motoring, and an Advanced Lead Carbon Battery for energy storage. The conventional alternator was replaced with a highly efficient DC-DC converter to supply energy to the 12V system. These technologies enabled powertrain efficiency improvement through the recovery of kinetic energy with regenerative braking and reapplication of the recovered energy through motoring to offset fuel usage. Efficiency was further optimised through application of engine downspeeding and advanced auto-stop strategies to extended engine-off time. Additional electrification was investigated through 48V ancillaries, including water-pump and air-conditioning compressor, and a turbo-compound generator for waste heat recovery from exhaust gas. These technologies have demonstrated a combined CO2 reduction of 10–11% against the conventional vehicle baseline. Additional studies of advanced thermal systems for improved warm-up, and lubrication control for FMEP reduction have also been conducted on this program. These indicate that by applying intelligent electrification to ancillaries a further 3–4% reduction in CO2 is achievable. Overall, this program shows that 48V technologies can achieve CO2 savings with a lower cost per gram CO2 than full hybrid solutions
CO2 reduction through low cost electrification of the diesel powertrain at 48V
In order to achieve fleet average CO2 targets, mass market adoption of low CO2 technologies is required. Application of low cost technologies across a large number of vehicles is more cost-effective in reducing fleet CO2 than deploying high-impact, costly technology to a few. Therefore, to meet the CO2 reduction challenge, commercially viable, low cost technologies are of significant interest. This paper presents results from the ‘ADEPT’ collaborative research program which focuses on CO2 reduction through the application of intelligent 48V electrification to diesel engines for passenger car applications. Results were demonstrated on a C-segment vehicle with a class-leading 4-cylinder 1.5 litre Euro 6 diesel engine. Electrification was applied through a high power, high efficiency, switched reluctance belt integrated starter generator (B-ISG) capable of both generation and motoring, and an Advanced Lead Carbon Battery for energy storage. The conventional alternator was replaced with a highly efficient DC-DC converter to supply energy to the 12V system. These technologies enabled powertrain efficiency improvement through the recovery of kinetic energy with regenerative braking and reapplication of the recovered energy through motoring to offset fuel usage. Efficiency was further optimised through application of engine downspeeding and advanced auto-stop strategies to extended engine-off time. Additional electrification was investigated through 48V ancillaries, including water-pump and air-conditioning compressor, and a turbo-compound generator for waste heat recovery from exhaust gas. These technologies have demonstrated a combined CO2 reduction of 10–11% against the conventional vehicle baseline. Additional studies of advanced thermal systems for improved warm-up, and lubrication control for FMEP reduction have also been conducted on this program. These indicate that by applying intelligent electrification to ancillaries a further 3–4% reduction in CO2 is achievable. Overall, this program shows that 48V technologies can achieve CO2 savings with a lower cost per gram CO2 than full hybrid solutions