No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
EGR System Optimization for Light-Duty Gasoline Compression Ignition (GCI) Engine
... A GT-Power software [28]-based 1D engine model was developed and calibrated for the analysis. The schematic of the simulated engine setup is shown in Figure 2. The details of the 1D engine model calibration process have been explained previously [19,29] and are summarized here briefly. engine was equipped with a two-step exhaust valvetrain, which included a two-step roller finger follower, hydraulic lash adjuster (HLA), and oil control valve (OCV). ...
... A GT-Power software [28]-based 1D engine model was developed and calibrated for the analysis. The schematic of the simulated engine setup is shown in Figure 2. The details of the 1D engine model calibration process have been explained previously [19,29] and are summarized here briefly. For the air system, a high-efficiency VNT turbocharger including a variable inlet compressor was modeled using the supplier-provided performance maps. ...
The global automotive industry is undergoing a significant transition as battery electric vehicles enter the market and diesel sales decline. It is widely recognized that internal combustion engines (ICE) will be needed for transport for years to come; however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach for achieving the demanding efficiency and emissions targets. A key technology enabler for GCI is partially-premixed, compression ignition (PPCI) combustion, which involves two high-pressure, late fuel injections during the compression stroke. Both NOx and smoke emissions are greatly reduced relative to diesel, and this reduces the aftertreatment (AT) requirements significantly. For robust low-load and cold operation, a two-step valvetrain system is used for exhaust rebreathing (RB). Exhaust rebreathing involves the reinduction of hot exhaust gases into the cylinder during a second exhaust lift event during the intake stroke to help promote autoignition. The amount of exhaust rebreathing is controlled by exhaust backpressure, created by the vanes on the variable nozzle turbine (VNT) turbocharger. Because of the higher cycle temperatures during rebreathing, exhaust HC and CO may be significantly reduced, while combustion robustness and stability also improve. Importantly, exhaust rebreathing significantly increases exhaust temperatures in order to maintain active catalysis in the AT system for ultra-low tailpipe emissions. To achieve these benefits, it is important to optimize the rebreathe valve lift profile and develop an RB ON→OFF (mode switch) strategy that is easy to implement and control, without engine torque fluctuation. In this study, an engine model was developed using GT-Suite to conduct steady-state and transient engine simulations of the rebreathing process, followed by engine tests. The investigation was conducted in four parts. In part 1, various rebreathe lift profiles were simulated. The system performance was evaluated based on in-cylinder temperature, exhaust temperature, and pumping work. The results were compared with alternative variable valve actuation (VVA) strategies such as early exhaust valve closing (EEVC), negative valve overlap (NVO), positive valve overlap (PVO). In part 2, steady-state simulations were conducted to determine an appropriate engine load range for mode switching (exhaust rebreathing ON/OFF and vice-versa). The limits for both in-cylinder temperature and exhaust gas temperature, as well as the external exhaust gas recirculation (EGR) delivery potential were set as the criteria for load selection. In part 3, transient simulations were conducted to evaluate various mode switch strategies. For RB OFF, the cooled external EGR was utilized with the goal to maintain exhaust gas dilution during mode switches for low NOx emissions. The most promising mode-switch strategies produced negligible torque fluctuation during the mode switch. Finally, in part 4, engine tests were conducted, using the developed RB valve lift profile, at various low-load operating conditions. The mode switch experiments correlated well with the simulation results. The tests demonstrated the simplicity and robustness of the exhaust rebreathing approach. A robust engine response, low CNL, high exhaust gas temperature, and low engine out emissions were achieved in the low load region.
... As can be clearly observed by looking at Figure 14, the use of EGR delays the SOC. Additionally, as explained in the literature, despite the increment in intake temperature given by the exhaust gas recirculation reducing the ID, by increasing the EGR rate the combustion will be even more delayed [19,32]. This phenomenon could be explained through the worsening of the internal mixing process generated by the EGR, which reduces the oxygen content of the charge. ...
Increasingly stringent pollutant emission limits and CO2 reduction policies are forcing the automotive industry toward cleaner and decarbonized mobility. The goal is to achieve carbon neutrality within 2050 and limit global warming to 2 °C (possibly 1.5 °C) with respect to pre-industrial levels as stated in both the European Green Deal and the Paris Agreement and further reiterated at the COP26. With the aim of simultaneously reducing both pollutants and CO2 emissions, a large amount of research is currently carried out on low-temperature highly efficient combustions (LTC). Among these advanced combustions, one of the most promising is Gasoline Compression Ignition (GCI), based on the spontaneous ignition of a gasoline-like fuel. Nevertheless, despite GCI proving to be effective in reducing both pollutants and CO2 emissions, GCI combustion controllability represents the main challenge that hinders the diffusion of this methodology for transportation. Several works in the literature demonstrated that to properly control GCI combustion, a multiple injections strategy is needed. The rise of pressure and temperature generated by the spontaneous ignition of small amounts of early-injected fuel reduces the ignition delay of the following main injection, responsible for the torque production of the engine. Since the combustion of the pre-injections is chemically driven, the ignition delay might be strongly affected by a slight variation in the engine control parameters and, consequently, lead to misfire or knocking. The goal of this work was to develop a control-oriented ignition delay model suitable to improve the GCI combustion stability through the proper management of the pilot injections. After a thorough analysis of the quantities affecting the ignition delay, this quantity was modeled as a function of both a thermodynamic and a chemical–physical index. The comparison between the measured and modeled ignition delay shows an accuracy compatible with the requirements for control purposes (the average root mean squared error between the measured and estimated start of combustion is close to 1.3 deg), over a wide range of operating conditions. As a result, the presented approach proved to be appropriate for the development of a model-based feed-forward contribution for a closed-loop combustion control strategy.
... A HP EGR cooler bypass (EGRByp) strategy was also investigated for the intake charge temperature increase. Previous studies [33,34] have reported favorable thermal promotion performance by utilizing uncooled ext.EGR flow. To implement this strategy, the hot exhaust gas from the exhaust manifold (upstream of the HP EGR cooler shown in Figure 1) was bypassed from the EGR cooler and introduced into the mixer and the intake manifold. ...
By harnessing gasoline’s low reactivity for partially premixed combustion promotion, gasoline compression ignition (GCI) combustion shows the potential to produce markedly improved NOx-soot trade-off with high fuel efficiency compared to conventional diesel combustion. However, at low-load conditions, gasoline’s low reactivity poses challenges to attaining robust combustion with low unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions. Increasing the in-cylinder charge temperature by using variable valve actuation (VVA) can be an effective means to address these challenges. In this numerical investigation, VVA strategies, including (1) early exhaust valve opening (EEVO), (2) positive valve overlap (PVO), and (3) exhaust rebreathe (ExReb), were investigated at 1375 RPM and 2 bar brake mean effective pressure in a heavy-duty GCI engine using a market-based gasoline with a research octane number (RON) of 93. The total residual gas level was kept over 50% to achieve an engine-out NOx target of below 1.5 g/kWh. For a complete engine system analysis, one-dimensional (1-D) system-level modeling and three-dimensional (3-D) computational fluid dynamics (CFD) analysis were close-coupled in this study. Performance of the VVA strategies was compared in terms of in-cylinder charge and exhaust gas temperatures increase versus brake-specific fuel consumption (BSFC). The EEVO strategy demonstrated in-cylinder charge and exhaust temperature increase up to 130 and 180 K, respectively. For similar in-cylinder charge temperature gains, the ExReb strategy demonstrated 11% to 18% lower BSFC compared to the EEVO strategy. This benefit primarily originated from a more efficient gas-exchange process. The PVO strategy, due to the valve–piston contact constraint, required excessive exhaust back-pressure valve (BPV) throttling for hot residuals trapping, thereby incurring higher BSFC compared to ExReb. In addition, the ExReb strategy demonstrated the highest potential for exhaust temperature increase (up to 673 K) among the three strategies. This was achieved by ExReb’s maximum air-fuel ratio reduction from high internal residuals mass and BPV throttling. Finally, the ExReb profile was optimized in terms of the peak lift, the duration, and the location for maximizing the fuel-efficiency potential of the strategy.
div class="section abstract"> Currently, on-road transport contributes nearly 12% of India’s total energy related carbon dioxide (CO2) emissions that are expected to be doubled by 2040. Following the global trends of increasingly stringent greenhouse gas emissions (GHG) and criteria emissions, India will likely impose equivalent Bharat Stage (BS) regulations mandating simultaneous reduction in CO2 emissions and nearly 90% lower nitrogen oxides (NOx) from the current BS-VI levels. Consequently, Indian automakers would likely face tremendous challenges in meeting such emission reduction requirements while balancing performance and the total cost of ownership (TCO) trade-offs. Therefore, it is conceivable that cost-effective system improvements for the existing internal combustion engine (ICE) powertrains would be of high strategic importance for the automakers. In this second part of a two-part article, several component-level advancements are discussed, including both the engine and the aftertreatment system (ATS) for heavy-duty (HD) diesel engine based powertrains. For engine system level, the role of efficient air-handling systems (AHS), including turbochargers and EGR configurations to reduce engine out NOx emissions, was reviewed. For thermal efficiency improvements, potential of millerization and its implications on the AHS performance were presented. For an efficient ATS performance during the engine cold-start warm-up period, critical to meeting criteria emissions compliance, thermal management strategies, including valve variability, were reviewed. Finally, market-relevant HD engine system recipes with a minimal TCO implications were highlighted.
</div
div class="section abstract"> A PPCI-diffusion combustion strategy has shown the potential to achieve high efficiency, clean gasoline compression ignition (GCI) combustion across the full engine operating range. By conducting a 3-D CFD-led combustion system design campaign, this investigation was focused on developing a next generation (NextGen), step-lipped piston design concept in a 2.6L advanced light-duty GCI engine. Key geometric features of the NextGen piston bowl were parametrized and studied with customized spray targeting. A low lip positioning design with 128° spray targeting was found to provide the best performance.
Fuel injection strategy optimization was performed at a full-load operating point (OP), 2000 rpm/24 bar closed-cycle IMEP (IMEPcc). When combined with the optimized fuel injection strategy, the best NextGen design was predicted to produce a 1.3% ISFC improvement and 42.5% lower soot compared to the baseline piston bowl design due to faster diffusion combustion and enhanced late-stage air-utilization. Subsequently, at 2000 rpm/12 bar IMEPcc, the NextGen design was able to soften the first-stage PPCI combustion to reduce the negative work and lower the MPRR, leading to 2.1% better ISFC and 48.8% lower soot than the baseline design when combined with its benefit to improve the second-stage diffusion combustion. Finally, at 1500 rpm/6 bar IMEPcc, the NextGen design was found to appreciably reduce the in-cylinder heat transfer and enable a larger fuel injection quantity in the first fuel injection event while retaining its air utilization benefit compared to the baseline design. Therefore, it was predicted to produce 2.4% better ISFC and 49.3% lower soot.
</div
div class="section abstract"> A two-stage PPCI-diffusion combustion process recently showed good potential to enable clean and fuel-efficient gasoline compression ignition (GCI) combustion at medium-to-high loads. By conducting closed-cycle 3-D CFD combustion analysis, a further step was undertaken in this work to evaluate and optimize the PPCI-diffusion combustion strategy at a full load operating point (2000rpm-23.5 bar IMEPcc) while keeping engine-out NOx below 1 g/kWh.
The light-duty GCI engine used in this investigation featured a custom-designed piston bowl geometry at a 17.0 compression ratio (CR), a high pressure diesel fuel injection system, and advanced single-stage turbocharging. A split fuel injection strategy was used to enable the two-stage PPCI-diffusion combustion process.
First, the injector spray pattern and swirl ratio effects were evaluated. In-cylinder air utilization and the PPCI-diffusion combustion process were notably influenced by the closed-cycle combustion system design. Among the different spray patterns at a swirl ratio of 0, the one with 120° spray inclusion angle, 8-hole, and 1.5 times total nozzle area (TNA) was favored due to enhanced late-stage fuel-air mixing and more rapid diffusion combustion. In the second step, a fuel injection strategy optimization campaign was performed through a space-filling Design of Experiments (DoE) approach. Overall, the optimized injector spray pattern and the optimized fuel injection strategy together were predicted to produce 5.1% lower ISFC and 50% soot reduction over the baseline. A competitive analysis showed the optimized PPCI-diffusion combustion strategy had the potential to generate substantially lower NOx and soot than a modern light-duty diesel engine at full load.
</div
Concawe and Aramco have jointly commissioned this study, aiming to conduct a techno-environmental (Part 1) and economic (Part 2) analysis of different e-fuels pathways produced in different regions of the world (North, Centre and South of Europe, as well as Middle East and North Africa) in 2020, 2030 and 2050, with assessments of sensitivities to multiple key techno-economic parameters.
The e-fuels pathways included in the scope of this study are: e-hydrogen (liquefied and compressed), e-methane (liquefied and compressed), e-methanol, e-polyoxymethylene dimethyl ethers (abbreviated as OME3-5), e-methanol to gasoline, e-methanol to kerosene, e-ammonia, and e-Fischer-Tropsch kerosene/diesel (low temperature reaction). The e-hydrogen is considered a final fuel but also feedstock for producing other e-fuels.
The study also includes:
- An assessment of stand-alone units versus e-plants integrated with oil refineries
- A comparison of e-fuels production costs versus fossil fuels / biofuels / e-fuels produced from nuclear electricity
- An analysis of the context of e-fuels in the future in Europe (potential demand, CAPEX, renewable electricity potential, land requirement, feedstocks requirements)
- A deep dive into the safety and environmental considerations, societal acceptance, barriers to deployment and regulation
The e-fuels techno-environmental assessment (Part 1) has been developed by Concawe and Aramco. The e-fuels economical and context assessment (Part 2) has been conducted by the consultants Ludwig-Bölkow-Systemtechnik GmbH (LBST) and E4tech, under the supervision of Concawe and Aramco.
An experimental study is carried out to compare the effects of high-pressure-loop, low-pressure-loop and dual-loop exhaust gas recirculation systems (HPL-EGR, LPL-EGR and DL-EGR) on the combustion characteristics, thermal efficiency and emissions of a diesel engine. The tests are conducted on a six-cylinder turbocharged heavy-duty diesel engine under various operating conditions. The low-pressure-loop portion (LPL-Portion) of DL-EGR is swept from 0% to 100% at several constant EGR rates, and the DL-EGR is optimized based on fuel efficiency. The results show that the LPL-EGR can attain the highest gross indicated thermal efficiency (ITEg) in the three EGR systems under all the tested conditions. At a middle load of 0.95 BMEP, 1660 r/min, the pumping losses of LPL-EGR lead to the lowest BTE among the EGR systems. The HPL-EGR can achieve the best brake thermal efficiency (BTE) and emissions within the EGR rate of 22.5% mainly due to the reduced pumping losses. For the DL-EGR, the low-pressure loop is enabled when the EGR rate exceeds 22.5%, and the LPL-Portion should be increased as the EGR further increases. The DL-EGR can achieve the best BTE and emissions. This is because the DL-EGR can achieve an optimum trade-off performance between the ITEg and pumping losses, and the lowest emissions are related to the proper ignition delay and equivalence ratio. As the engine load decreases, the low-pressure loop in DL-EGR mode should be activated at a higher EGR rate. At a lower speed of 1330 r/min, 1.43 MPa BMEP, the HPL-EGR can achieve a slightly better BTE within the EGR rate of 12%. The DL-EGR can achieve the best BTE for the higher EGR rates, but the emissions of LPL-EGR are much better than that of DL-EGR.
SAE 2007-01-0006
A Swedish MK1 diesel fuel and a European gasoline of
~95 RON have been compared in a single cylinder CI
engine operating at 1200 RPM with an intake pressure
of 2 bar abs., intake temperature of 40°C and 25%
stoichiometric EGR at different fuelling rates and using
different injection strategies. For the same operating
conditions, gasoline always gives much lower smoke
compared to the diesel fuel because of its higher ignition
delay; this usually allows the heat release to be separate
in time from the injection event. NOx can be controlled
by EGR. With dual injection, for diesel fuel, there can be
significant heat release during the compression stroke
because of the pilot injection earlier in the compression
stroke. For a fixed total fuelling rate, compared to single
injection, this reduces fuel efficiency and increases the
lowest achievable level of smoke. With gasoline, pilot
injection helps reduce the maximum heat release rate
for a given IMEP and enables heat release to occur later
with low cyclic variation compared to single injection.
This enables higher mean IMEP to be reached with
lower smoke, NOx and maximum heat release rate
compared to single injection. One of the operating points
reached with gasoline with double injection had mean
IMEP of 15.95 bar (stdev. 0.112 bar), AVL smoke
opacity of 0.33% (FSN < 0.07), ISNOx of 0.58 g/kWh,
ISFC of 179 g/kWh, ISHC of 2.9 g/kWh, ISCO of 6.8
g/kWh and peak pressure of ~ 120 bar. At the same
operating conditions, to get such low level of smoke with
Swedish MK1 diesel fuel, IMEP has to be below 6.5 bar.
There is scope for further improvements by increasing
intake pressure and the EGR level and through
optimisation of the injection and mixture preparation
strategy e.g. more injection pulses and injector design
e.g. more holes.
div class="section abstract"> It is widely recognized that internal combustion engines (ICE) are needed for transport worldwide for years to come, however, demands on ICE fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieve demanding efficiency and emissions targets. At Aramco Research Center-Detroit, an advanced, multi-cylinder GCI engine was designed and built using the latest combustion system, engine controls, and lean aftertreatment. The combustion system uses Aramco’s PPCI-diffusion process for ultra-low NOx and smoke. A P2 48V mild hybrid system was integrated on the engine for braking energy recovery and improved cold starts. For robust low-load operation, a 2-step valvetrain system was used for exhaust rebreathing.
Test data showed that part-load fuel consumption was reduced 7 to 10 percent relative to a competitive 2.0L European diesel engine. The GCI engine produced “near-zero” tailpipe emissions of NOx, smoke, HC, and CO at most warm operating conditions. At 1500rpm, the engine was capable of over 25bar BMEP, demonstrating excellent low-speed torque characteristics of the engine.
Cold transient tests were conducted on the US FTP75 drive cycle using a “virtual vehicle” test methodology. A real engine and aftertreatment system with controller were tested in combination with vehicle and transmission models. Measured fuel economy (mpg) was 61 percent higher than the baseline spark-ignited turbocharged engine in a large SUV vehicle. Hydrocarbon, carbon monoxide, and NOx and PM emissions were below the stringent US 2026 Tier3- Bin30 regulations. An electrically heated SCR catalyst was needed to meet NOx tailpipe targets.
In addition to room temperature cold starts, cold startability tests were conducted in a cold chamber down to -30 degrees C. Electric intake air heating combined with exhaust rebreathing provided robust cold starts without spark assistance.
When operated on commercial E10 gasoline, simulated life-cycle CO2 emissions were reduced about 31 percent relative to the baseline. When operated on low carbon eGasoline, CO2 emissions were reduced by an estimated 80 percent, which is competitive with various new energy vehicles (NEV) including battery electric vehicles. Overall, this work shows that GCI technology has evolved as an efficient, clean, and robust powertrain for future transport.
</div
div class="section abstract"> The global automotive industry is undergoing a significant transition as battery electric vehicles enter the market and diesel sales decline. It is widely recognized that internal combustion engines (ICE) are needed for transport for years to come, however, demands on fuel efficiency, emissions, cost, and performance are extremely challenging. Gasoline compression ignition (GCI) is one approach to achieving demanding future efficiency and emissions targets. A key technology enabler for GCI is partially premixed, compression ignition (PPCI) combustion, which involves two high-pressure, late, fuel injections during the compression stroke. Both NOx and smoke emissions are greatly reduced relative to diesel engines, and this reduces aftertreatment (AT) requirements significantly.
Exhaust rebreathing (RB) is used for robust low-load and cold operation. This is enabled by use of 2-Step, mode switching rocker arms to allow switching between rebreathe and normal combustion modes. Exhaust rebreathing involves reinduction of hot exhaust gases into the cylinder during a second exhaust lift event during the intake stroke to help promote autoignition. The amount of exhaust rebreathing is controlled by exhaust backpressure created by the vanes on the variable nozzle turbine (VNT) turbocharger. Due to higher cycle temperatures when rebreathing, exhaust HC and CO may be significantly reduced, while combustion robustness and stability also improve. Increased charge dilution during rebreathing can also lower NOx emissions. Importantly, exhaust rebreathing significantly increases exhaust temperatures to maintain active catalysis in the AT system for ultra-low tailpipe emissions.
A 2-step valvetrain system was designed and developed for exhaust rebreathing on a 2.6l light-duty gasoline compression ignition engine. Tri-roller, switching rocker arms with hydraulically actuated lock pins were built for low friction. The 2-step actuation system was designed for fast response using a pulse-width-modulated oil control valve that regulated the oil pressure feeding the switching rocker arms.
Tests were conducted on the dynamometer demonstrating robust combustion with high exhaust temperatures and active catalysis at low load operation. Calibration mapping tests were also conducted. Overall, the tests demonstrated the simplicity and robustness of the exhaust rebreathing approach while delivering low exhaust emissions.
</div
Currently the OEMs of commercial vehicles (using an internal combustion engine) are preparing for the new emission legislation EU-VII und EPA-27. The challenge is an improved NOx-reduction at cold-start and low load conditions as well as reduced CO2. In the meantime, also in the Off-Road sector (NRMM) the first discussions started on next steps. The existing exhaust aftertreatment systems are typically showing very high NOx-conversion rates when operated at the appropriate temperature. OEMs are investigating a variety of possible solutions to increase the temperature level of the SCR catalysts for the critical operation points: cold start and low load. “Pure” electrical heating has quite a high CO2-disadvantage in the case that the electrical power is coming from alternator and battery. The high power-demand for higher exhaust mass-flow is another challenge for the electrical system. Fuel dosing into the exhaust system is a state-of-the-art process for DPF regeneration and shows a high efficiency in energy release. Combining electrical heating with fuel dosing results in an efficient heating with moderate electrical power demand. “Engine-independent” heating of the exhaust system allows in turn the engine to operate in the “CO2-bestpoint” and thus reduce the fuel consumption. The innovative compact catalytical heater as an add-on component upstream of a well proven CV-muffler allows to begin fuel dosing very early in the cold-start phase, generating high amount of energy for the fast heat-up of all components (including catalysts) within the muffler. It is also intended to operate for keeping the exhaust system warm in low load operation. The goal is to continue using already existing and well-established exhaust components (muffler) to reduce R&D efforts & tooling costs. This paper describes the development of the system including simulation as well as test results on a dynamic heavy-duty engine test bench resulting an improvement of 11%-points in the FTP cold start and in the Low Load Cycle (LLC) a NOx conversion of 99% with active heating.KeywordsLow NOxExhaust thermal managementElectrically heated catalystCatalytical heater
div class="section abstract"> Commercial vehicles require fast aftertreatment heat-up to move the SCR catalyst into the most efficient temperature range to meet upcoming NOX regulations while minimizing CO2. The focus of this paper is to identify the technology levers when used independently and also together for the purpose of NOX and CO2 reduction toward achieving 2027 emissions levels while remaining CO2 neutral or better. A series of independent levers including cylinder deactivation, LO-SCR, electric aftertreatment heating and fuel burner technologies were explored. All fell short for meeting the 2027 CARB transient emission targets when used independently. However, the combinations of two of these levers were shown to approach the goal of transient emissions with one configuration meeting the requirement. Finally, the combination of three independent levers were shown to achieve 40% margin for meeting 2027 transient NOx emissions while remaining CO2 neutral. These independent levers and combinations were also quantified for meeting the new Low Load Cycle. This paper shows which combinations of technologies meets both the transient emission cycles and low load cycles for NOx with adequate margin while also saving CO2.
</div
div class="section abstract"> A PPCI-diffusion combustion strategy has shown the potential to achieve high efficiency, clean gasoline compression ignition (GCI) combustion across the full engine operating range. By conducting a 3-D CFD-led combustion system design campaign, this investigation was focused on developing a next generation (NextGen), step-lipped piston design concept in a 2.6L advanced light-duty GCI engine. Key geometric features of the NextGen piston bowl were parametrized and studied with customized spray targeting. A low lip positioning design with 128° spray targeting was found to provide the best performance.
Fuel injection strategy optimization was performed at a full-load operating point (OP), 2000 rpm/24 bar closed-cycle IMEP (IMEPcc). When combined with the optimized fuel injection strategy, the best NextGen design was predicted to produce a 1.3% ISFC improvement and 42.5% lower soot compared to the baseline piston bowl design due to faster diffusion combustion and enhanced late-stage air-utilization. Subsequently, at 2000 rpm/12 bar IMEPcc, the NextGen design was able to soften the first-stage PPCI combustion to reduce the negative work and lower the MPRR, leading to 2.1% better ISFC and 48.8% lower soot than the baseline design when combined with its benefit to improve the second-stage diffusion combustion. Finally, at 1500 rpm/6 bar IMEPcc, the NextGen design was found to appreciably reduce the in-cylinder heat transfer and enable a larger fuel injection quantity in the first fuel injection event while retaining its air utilization benefit compared to the baseline design. Therefore, it was predicted to produce 2.4% better ISFC and 49.3% lower soot.
</div
div class="section abstract"> Continued improvement in the combustion process of internal combustion engines is necessary to reduce fuel consumption, CO2 emissions, and criteria emissions for automotive transportation around the world. In this paper, test results for the Gen3X Gasoline Direct Injection Compression Ignition (GDCI) engine are presented. The engine is a 2.2L, four-cylinder, double overhead cam engine with compression ratio ~17. It features a “wetless” combustion system with a high-pressure direct injection fuel system. At low load, exhaust rebreathing and increased intake air temperature were used to promote autoignition and elevate exhaust temperatures to maintain high catalyst conversion efficiency. For medium-to-high loads, a new GDCI-diffusion combustion strategy was combined with advanced single-stage turbocharging to produce excellent low-end torque and power. Time-to-torque (TT) simulations indicated 90% load response in less than 1.5 seconds without a supercharger. For cold starts, the engine is equipped with a fast 2.5kW electric air heater positioned upstream of the intake valves. No spark plugs are used.
Dynamometer tests indicated excellent fuel efficiency over the operating map. Minimum BSFC of 194 g/kWh (BTE 43%) was measured at 1750rpm- 12bar IMEP with BSFC less than 210 (40% BTE) over a very wide operating region. The GDCI engine operates on US pump gasoline (RON91) and is ideal for down speeding and uploading for improved vehicle fuel economy. New simulations showed that potentially 48% BTE could be achieved through use of thermal barrier coatings and other improvements to the engine (Gen4X engine).
Vehicle simulations were performed at Argonne using the Gen3X engine map for a midsize sedan, SUVs, and a pickup truck. Results indicated a 36 to 51% improvement in combined FTP fuel economy over a competitive 2015 1.6L turbocharged GDi engine equipped with intake variable valve lift. The simulations showed that the Gen3X engine with 12V start/stop or mild hybridization can compete with full hybrid powertrains in various vehicle segments.
</div
As the control of real driving emissions continues to increase in importance, the importance of understanding emission formation mechanisms during engine transients similarly increases. Knowledge of the NO 2 /NO x ratio emitted from a diesel engine is necessary, particularly for ensuring optimum performance of NO x aftertreatment systems. In this work, cycle-to-cycle NO and NO x emissions have been measured using a Cambustion CLD500, and the cyclic NO 2 /NO x ratio calculated as a high-speed light-duty diesel engine undergoes transient steps in load, while all other engine parameters are held constant across a wide range of operating conditions with and without exhaust gas recirculation. The results show that changes in NO and NO x , and hence NO 2 /NO x ratio, are instantaneous upon a step change in engine load. NO 2 /NO x ratios have been observed in line with previously reported results, although at the lightest engine loads and at high levels of exhaust gas recirculation, higher levels of NO 2 than have been previously reported in the literature are observed.
Diesel engine exhaust gas flows through the DOC upstream of the DPF system. In this process, NO contained in NOx is oxidized into NO2 and then enters DPF. The presence of NO2 can greatly reduce the light-off critical temperature of soot particles, so that the soot particles captured by DPF will conduct a certain amount of continuous passive regeneration at a lower temperature. However, there is the complex coupling reaction relationship between NOx and PM contained in the DPF, not only the reaction between the particulates and NOx, but also a series of reaction between CO and NOx. And except NO and NO2 of NOx in diesel engineer exhaust which are recognized and studied widely, there is a small amount of N2O generated as the intermediate product in the entire reaction process of DPF generation. The oxidation ability of NO2, NO, and N2O contained in NOx are different, and the change of diesel engine exhaust composition also affects the quantity and proportion of them. These factors have a close relationship with the removal of soot particulate, in other words, the regeneration of DPF. This paper builds the NOx-PM reaction mechanism in DPF, and studies the chemical reaction process between NOx and PM under different inlet conditions. This paper defines the coefficient α, which is used to characterize the ratio of NO2 in diesel engineer exhaust at the DPF inlet accounting for the total amount of NOx. The results show that when α is between 0.7 and 0.8, the good regeneration removal effect of soot particulates under the premise of not worsening NOx removal efficiency is achieved. The molar ratio of NOx at the DPF inlet and carbon in the PM is defined as β. When β≈1, NOx removal efficiency is the maximum. When β⩾8, the soot particulates can complete continuous passive regeneration totally only by relying on the mutual reaction of DPF internal reactants in this condition. Investigation results show that N2O and CO are important intermediate products during the reaction process of NOx-PM.
In this paper we consider the issues facing the design of a practical multivariable controller for a diesel engine with dual exhaust gas recirculation (EGR) loops. This engine architecture requires the control of two EGR valves (high pressure and low pressure), an exhaust throttle (ET) and a variable geometry turbocharger (VGT). A systematic approach suitable for production-intent air handling control using Model Predictive Control (MPC) for diesel engines is proposed. Furthermore, the tuning process of the proposed design is outlined. Experimental results for the performance of the proposed design are implemented on a 2.8L light duty diesel engine. Transient data over an LA-4 cycle for the closed loop performance of the controller are included to prove the effectiveness of the proposed design process. The MPC implementation process took a total of 10 days from the start of the data collection to build a calibrated engine model all the way through the calibration of the controller over the transient drive cycle.
As the markets require more environmentally friendly and high fuel consumption vehicle, we have to satisfy bilateral target. Though many new after-treatment techniques like LNT, SCR are investigated to meet both strong emission regulations and low fuel consumption, high cost of these techniques should be solved to adopt widely. This paper describes how to optimize the dual loop EGR as a tool to reduce CO2 emission of a HSDI diesel engine in the passenger car application. Focus is not only on the optimization to obtain the maximum CO2 reduction but also on how to assess and overcome various side effects. As a result of careful optimization, as much as 6% CO 2 reduction was achieved by introduction of low pressure EGR loop, maintaining the same boundary conditions as those with high pressure EGR loop only. Not only the dual EGR system but also further improvement was applied such as combustion improvement, friction reduction and many others to achieve as much as 20% total CO2 reduction. The dual loop EGR was proven to be an effective solution to reduce CO2 and therefore it is considered to be one of the core technologies in the passenger diesel applications of Hyundai-Kia Motors to meet the future CO2 regulation.
This paper compares 4 different EGR systems by means of simulation in GT-Power. The demands of optimum massive EGR and fresh air rates were based on experimental results. The experimental data were used to calibrate the model and ROHR, in particular. The main aim was to investigate the influence of pumping work on engine and vehicle fuel consumption (thus CO2 production) in different EGR layouts using optimum VG turbine control. These EGR systems differ in the source of pressure drop between the exhaust and intake pipes. Firstly, the engine settings were optimized under steady operation-BSFC was minimized while taking into account both the required EGR rate and fresh air mass flow. Secondly, transient simulations (NEDC cycle) were carried out-a full engine model was used to obtain detailed information on important parameters. The study shows the necessity to use natural pressure differences or renewable pressure losses if reasonable fuel consumption is to be achieved.
Four high-efficiency alternative combustion modes were modeled to determine the potential brake thermal efficiency (BTE) relative to a traditional lean burn compression ignition diesel engine with selective catalytic reduction (SCR) aftertreatment. The four combustion modes include stoichiometric pilot-ignited gasoline with EGR dilution (SwRI HEDGE technology), dual fuel premixed compression ignition (University of Wisconsin), gasoline partially premixed combustion (Lund University), and homogenous charge compression ignition (HCCI) (SwRI Clean Diesel IV). For each of the alternative combustion modes, zero-D simulation of the peak torque condition was used to show the expected BTE. For all alternative combustion modes, simulation showed that the BTE was very dependent on dilution levels, whether air or EGR. While the gross indicated thermal efficiency (ITE) could be shown to improve as the dilution was increased, the required pumping work decreased the BTE at EGR rates above 40%. None of the alternative combustion modes was able to exceed the BTE of a traditional lean burn diesel engine with EGR when calibrated to 2.7 g/kW-h engine-out NOx when constrained by currently available turbocharger efficiency.
The goal of this research was to improve thermal efficiency under conditions of stoichiometric air-fuel ratio and 91 RON (Research Octane Number) gasoline fuel. Increasing compression ratio and dilution are effective means to increase the thermal efficiency of gasoline engines. Increased compression ratio is associated with issues such as slow combustion, increased cooling loss, and engine knocking.
The ongoing pursuit of improved engine efficiency and emissions are driving gasoline low-pressure loop EGR systems into production around the globe. To minimize inevitable downsides of cooled EGR while maintaining its advantages, the Dedicated EGR (D-EGR®) engine was developed. The core of the D-EGR engine development focused on a unique concept that combines the efficiency improvements associated with recirculated exhaust gas and the efficiency improvements associated with fuel reformation. To outline the differences of the new engine concept with a conventional low-pressure loop (LPL) EGR setup, a turbocharged 2.0 L PFI engine was modified to operate in both modes and also compared to the baseline. The first part of the cooled EGR engine concept comparison investigates efficiency, emissions, combustion stability, and robustness at throttled part load conditions. In addition, the LPL EGR configuration was supplemented with bottled H2 / CO to examine if the D-EGR engine performance can be matched. The results show the D-EGR engine can tolerate higher EGR dilution levels, enable faster burn rates, reduce cycle-to-cycle variations and can further improve efficiency and emissions. Additionally, the D-EGR technology decreases the ignition energy requirements. Moreover, by adding the bottled reformate to the LPL EGR engine, the performance of the D-EGR setup can be simulated.
A single-cylinder engine was used to study the potential of a high-efficiency combustion concept called gasoline direct-injection compression-ignition (GDCI). Low temperature combustion was achieved using multiple injections, intake boost, and moderate EGR to reduce engine-out NOx and PM emissions engine for stringent emissions standards. This combustion strategy benefits from the relatively long ignition delay and high volatility of regular unleaded gasoline fuel. Tests were conducted at 6 bar IMEP - 1500 rpm using various injection strategies with low-to-moderate injection pressure. Results showed that triple injection GDCI achieved about 8 percent greater indicated thermal efficiency and about 14 percent lower specific CO2 emissions relative to diesel baseline tests on the same engine. Heat release rates and combustion noise could be controlled with a multiple-late injection strategy for controlled fuel-air stratification. Estimated heat losses were significantly reduced. GDCI has good potential for full-time operation over the US Federal drive cycle.
Intake boosting is an important method to improve fuel economy of internal combustion engines. Engines can be down-sized, down-speeded, and up-loaded to reduce friction losses, parasitic losses, and pumping losses, and operate at speed-load conditions that are thermodynamically more efficient. Low-temperature combustion engines (LTE) also benefit from down-sizing, down-speeding, and up-loading, but these engines exhibit very low exhaust enthalpy to drive conventional turbochargers. This paper describes modeling, evaluation, and selection of an efficient boost system for a 1.8L four-cylinder Gasoline Direct-Injection Compression-Ignition (GDCI) engine. After a preliminary concept selection phase the model was used to develop the boost system parameters to achieve full-load and part-load engine operation objectives. The simulation was used to demonstrate that a practical boost system can provide the boost necessary at reasonable brake efficiency levels over the entire engine operating range. A comprehensive simulation based calibration was performed to determine the most efficient steady operation settings. Also a step change in speed/load engine operation was simulated to demonstrate the system transient response.
Cooled EGR Shows Benefits for Gasoline Engines
- B Morey
The Landscape of GCI Combustion "Fuel Properties and Stratification
- D A Splitter
- R M Wagner
- A B Dempsey
- S J Curran
Splitter, D.A., Wagner, R.M., Dempsey, A.B., and
Curran, S.J., "The Landscape of GCI Combustion "Fuel
Properties and Stratification," SAE 2015 Gasoline Compression
Ignition Engine Symposium, September 17, 2015, Capri, Italy.
MAZDA SKYACTIV-X 2.0L Gasoline Engine
- E Nakai
- T Goto
- K Ezumi
- Y Tsumura
Nakai, E., Goto, T., Ezumi, K., Tsumura, Y., et al.,
"MAZDA SKYACTIV-X 2.0L Gasoline Engine," 28th Aachen
Colloquium Automobile and Engine Technology, 2019.
Zero Impact Pollutant Emissions and 50% Real-World Efficiency-The Future of CI Powertrains
- C Menne
- M Ehrly
- R Zegers
- P Recker
Menne, C., Ehrly, M., Zegers, R., Recker, P., et al.,
"Zero Impact Pollutant Emissions and 50% Real-World
Efficiency-The Future of CI Powertrains," 30th Aachen
Colloquium Sustainable Mobility, 2021.
BASF LT-NA Technology Overview
- X Wei
Wei, X., "BASF LT-NA Technology Overview,"
Personal Communication, April 23, 2020.
Die Systementwicklung des elektrisch beheizbaren Katalysators E-Kat feur die LEV/ULEV und EU III Gesetzgebung
- E Otto
- W Held
- A Donnerstag
- P Kueper
- B Pfalzgraf
- A Wirth
Otto, E., Held, W., Donnerstag, A., Kueper, P.,
Pfalzgraf, B., Wirth, A. (1995). "Die Systementwicklung des
elektrisch beheizbaren Katalysators E-Kat feur die LEV/ULEV
und EU III Gesetzgebung". MTZ Publication 56 (1995).
Combination of electrically heated catalytic converter and SCR@DPF for challenging V-TDI projects
- H Loerch
- S Moehn
- U Weiss
- J Haas
Loerch, H., Moehn, S., Weiss, U., Haas, J., (2014),
"Combination of electrically heated catalytic converter and
SCR@DPF for challenging V-TDI projects", 14. International
Stuttgarter Symposium, 2014.
Innovative EAS Technologies in development for On-Road and Off-Road Applications
- R Brueck
Brueck, R. (2019). "Innovative EAS Technologies in
development for On-Road and Off-Road Applications", 10th
ICPC Conference 2019, Graz, Austria.
Future Regulatory technology options to reduce risk in application for heavy duty diesel engines
- C Webb
- P Stephenson
- M Meijer
- A Coumans
- R Brueck
- J Kramer
Webb, C., Stephenson, P., Meijer, M., Coumans, A.,
Brueck, R. and Kramer, J. (2021). "Future Regulatory
technology options to reduce risk in application for heavy duty
diesel engines". Aachen Colloquium Sustainable Mobility 2021.
Classification: Public Information