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Technical Paper

The Effects of EGR Composition on Combustion Performance and Efficiency

2020-09-15
2020-01-2052
Because of the thermodynamic relationship of pressure, temperature and volume for processes which occur in an internal-combustion engine (ICE), and their relationship to ideal efficiency and efficiency-limiting phenomena e.g. knock in spark-ignition engines, changing the thermo-chemical properties of the in-cylinder charge should be considered as an increment in the development of the ICE engine for future efficiency improvements. Exhaust gas recirculation (EGR) in spark-ignited gasoline engines is one increment that has been made to alter the in-cylinder charge. EGR gives proven thermal efficiency benefits for SI engines which improve vehicle fuel economy, as demonstrated through literature and production applications. The thermal efficiency benefit of EGR is due to lower in-cylinder temperatures, reduced heat transfer and reduced pumping losses.
Technical Paper

Ignition Delay Model Parameterization using Single-Cylinder Engines Data

2020-09-15
2020-01-2005
The confluence of increasing fuel economy requirements and increased use of ethanol as a gasoline blend component has led to various studies into the efficiency and performance benefits of higher octane numbers and high ethanol content fuels in modern engines. As part of a comprehensive study of the autoignition of different fuels in both the CFR octane rating engine and a modern, direct injection, turbocharged spark-ignited engine, a series of fuel blends were prepared with varying composition, octane numbers and ethanol blend levels. The paper reports on the third part of this study where cylinder pressures were recorded for fuels under knocking conditions in both a single-cylinder research engine (SCRE), utilizing a GM LHU head and piston, as well as the CFR engines used for octane ratings.
Technical Paper

Bridging the Knock Severity Gap to CFR Octane Rating Engines

2020-09-15
2020-01-2050
It is widely acknowledged that the CFR octane rating engines are not representatively of modern engines and that there is a gap in the quantification of knock severity between the two engine types. As part of a comprehensive study of the autoignition of different fuels in both the CFR octane rating engines and a modern, direct injection, turbocharged spark-ignited engine, a series of fuel blends were prepared with varying composition, octane numbers and ethanol blend levels. The paper reports on the forth part of this study where cylinder pressures were recorded under standard knock conditions in the CFR engines under RON and MON conditions using the ASTM prescribed instrumentation. By the appropriate signal conditioning of the D1 detonation pick-up on the CFR engine, a quantification of the knock severity was achieved that matched that of a cylinder pressure transducer as well as exhibiting the same frequency response.
Technical Paper

The Diesel Aftertreatment Accelerated Aging Cycle Protocol: An Advanced Aftertreatment Case Study

2020-09-15
2020-01-2210
As agencies and governing bodies evaluate the feasibility of reduced emission standards, additional focus has been placed on technology durability. This is seen in proposed updates, which would require Original Equipment Manufacturers (OEMs) to certify engine families utilizing a full useful life (FUL) aftertreatment system. These kinds of proposed rulings would place a heavy burden on the manufacturer to generate FUL components utilizing traditional engine aging methods. Complications in this process will also increase the product development effort and will likely limit the amount of aftertreatment durability testing. There is also uncertainty regarding the aging approach and the representative impact compared to field aged units. Existing methodologies have evolved to account for several deterioration mechanisms that, when controlled, can be utilized to create a flexible aging protocol. As a result, these methodologies provide the necessary foundation for continued development.
Technical Paper

Comparison of Partial and Total Dilution Systems for the Measurement of Polycyclic Aromatic Hydrocarbons and Hydrocarbon Speciation in Diesel Exhaust

2020-09-15
2020-01-2190
There are two methods of sampling exhaust emissions: total dilution using a constant volume sampling (CVS) system and partial flow dilution by proportionally diluting a small part from the main exhaust stream. The CVS dilutes the entire exhaust flow to a constant volumetric flowrate which allows for proportional sampling of the exhaust species during transient engine operation. For partial dilution sampling during transient engine operation, obtaining a proportional sample is more rigorous and the proportionality of the sample must be continuously changed throughout the cycle in order to be proportional to the overall continuously-changing exhaust flow. For this study, a Sierra Instruments BG-3 Partial Flow Sampling Cart (BG-3) and a standard CVS were used to compare the measurements for polycyclic aromatic hydrocarbons (PAH) and hydrocarbon speciation of compounds from methane to dodecane including aldehydes and ketones in diesel exhaust.
Technical Paper

Detailed Analyses and Correlation of Fuel Effects on Stochastic Preignition

2020-04-14
2020-01-0612
Stochastic or Low-Speed Preignition (SPI or LSPI) is an undesirable abnormal combustion phenomenon encountered in spark-ignition engines. It is characterized by very early heat release and high cylinder pressure and can cause knock, noise and ultimately engine damage. Much of the focus on mitigating SPI has been directed towards the engine oil formulation, leading to the emergence of the Sequence IX test and second-generation GM dexos® oil requirements. Engine design, calibration and fuels also contribute to the prevalence of SPI. As part of a recently completed research consortium, a series of engine tests were completed to determine the impact of fuel composition on SPI frequency. The fuel blends had varying levels of paraffins, olefins, aromatics and ethanol.
Technical Paper

CARB Low NOx Stage 3 Program - Modified Engine Calibration and Hardware Evaluations

2020-04-14
2020-01-0318
With the conclusion of the California Air Resources Board (CARB) Stage 1 Ultra-Low NOX (ULN) program, there continues to be a commitment for identifying potential pathways to demonstrate 0.02 g/bhp-hr NOX emissions. The Stage 1 program focused on achieving the ULN levels on the heavy-duty regulatory cycles utilizing a turbo-compound engine which required the integration of novel catalyst technologies and a supplemental heat source. While the aftertreatment configuration provided a potential solution to meet the ULN target, a complicated approach with a greenhouse gas (GHG) penalty was required to overcome challenges from low temperature exhaust. A subsequent Stage 2 program was concerned with the development of a new low load test cycle and evaluating the trade-off between GHG and tailpipe NOX on the Stage 1 ULN solution.
Journal Article

Use of Nitric Acid to Control the NO2:NOX Ratio within the Exhaust Composition Transient Operation Laboratory Exhaust Stream

2020-04-14
2020-01-0371
The Exhaust Composition Transient Operation LaboratoryTM (ECTO-LabTM) is a burner system developed at Southwest Research Institute (SwRI) for simulation of IC engine exhaust. The current system design requires metering and combustion of nitromethane in conjunction with the primary fuel source as the means of NOX generation. While this method affords highly tunable NOX concentrations even over transient cycles, no method is currently in place for dictating the speciation of nitric oxide (NO) and nitrogen dioxide (NO2) that constitute the NOX mixture. NOX generated through combustion of nitromethane is dominated by NO, and generally results in an NO2:NOX ratio of < 5 %. Generation of any appreciable quantities of NO2 is therefore dependent on an oxidation catalyst to oxidize a fraction of the NO to NO2.
Technical Paper

Investigation into Low-Temperature Urea-Water Solution Decomposition by Addition of Titanium-Based Isocyanic Acid Hydrolysis Catalyst and Surfactant

2020-04-14
2020-01-1316
Mitigation of urea deposit formation and improved ammonia production at low exhaust temperatures continues to be one of the most significant challenges for current generation selective catalytic reduction (SCR) aftertreatment systems. Various technologies have been devised to alleviate these issues including: use of alternative reductant sources, and thermal treatment of the urea-water solution (UWS) pre-injection. The objective of this work was to expand the knowledge base of a potential third option, which entails chemical modification of UWS by addition of a titanium-based urea/isocyanic acid (HNCO) decomposition catalysts and/or surfactant to the fluid. Physical solid mixtures of urea with varying concentrations of ammonium titanyl oxalate (ATO), oxalic acid, and titanium dioxide (TiO2) were generated, and the differences in NH3 and CO2 produced upon thermal decomposition were quantified.
Technical Paper

Heat Transfer Enhancement through Advanced Casting Technologies

2020-04-14
2020-01-1162
There is growing interest in additive manufacturing technologies for prototype if not serial production of complex internal combustion engine components such as cylinder heads and pistons. In support of this general interest the authors undertook an experimental bench test to evaluate opportunities for cooling jacket improvement through geometries made achievable with additive manufacturing. A bench test rig was constructed using electrical heating elements and careful measurement to quantify the impact of various designs in terms of heat flux rate and convective heat transfer coefficients. Five designs were compared to a baseline - a castable rectangular passage. With each design the heat transfer coefficients and heat flux rates were measured at varying heat inputs, flow rates and pressure drops. Four of the five alternative geometries outperformed the baseline case by significant margins.
Technical Paper

Portable In-Cylinder Pressure Measurement and Signal Processing System for Real-Time Combustion Analysis and Engine Control

2020-04-14
2020-01-1144
This paper presents an in-cylinder pressure measurement system for cycle-to-cycle feedback combustion control purposes. Such a system uses off-the-shelf components to measure cylinder pressure and performs user-defined algorithms for heat release analysis. The working principle of the device is discussed as well as the simplifications for heat release analysis required for fast computation. The system is benchmarked against a commercially-available combustion analyzer in order to quantify the accuracy and time response. The results showed that the system is satisfactorily accurate for combustion phasing control. The main advantage, however, comes from the reduction of calculation and communication delays observed in the commercially-available system. This enables the use of cycle-to-cycle cylinder pressure-based feedback control algorithms.
Technical Paper

In-Situ Measurement of Component Efficiency in Connected and Automated Hybrid-Electric Vehicles

2020-04-14
2020-01-1284
Connected and automated driving technology is known to improve real-world vehicle efficiency by considering information about the vehicle’s environment such as traffic conditions, traffic lights or road grade. This study shows how the powertrain of a hybrid-electric vehicle realizes those efficiency benefits by developing methods to directly measure real-time transient power losses of the vehicle’s powertrain components through chassis-dynamometer testing. This study is a follow-on to SAE Technical Paper 2019-01-0116, Test Methodology to Quantify and Analyze Energy Consumption of Connected and Automated Vehicles [1], to understand the sources of efficiency gains resulting from connected and automated vehicle driving. A 2017 Toyota Prius Prime was instrumented to collect power measurements throughout its powertrain and driven over a specific driving schedule on a chassis dynamometer.
Technical Paper

Electronic Control of Brake and Accelerator Pedals for Precise Efficiency Testing of Electrified Vehicles

2020-04-14
2020-01-1282
Efficiency testing of hybrid-electric vehicles is challenging, because small run-to-run differences in pedal application can change when the engine fires or the when the friction brakes supplement regenerative braking, dramatically affecting fuel use or energy regeneration. Electronic accelerator control has existed for years, thanks to the popularity of throttle-by-wire (TBW). Electronic braking control is less mature, since most vehicles don’t use brake-by-wire (BBW). Computer braking control on a chassis dynamometer typically uses a mechanical actuator (which may suffer backlash or misalignment) or braking the dynamometer rather than the vehicle (which doesn’t yield regeneration). The growth of electrification and autonomy provides the means to implement electronic brake control. Electrified vehicles use BBW to control the split between friction and regenerative braking. Automated features, e.g. adaptive cruise control, require BBW to actuate the brakes without pedal input.
Technical Paper

CARB Low NOX Stage 3 Program - Aftertreatment Evaluation and Down Selection

2020-04-14
2020-01-1402
With the conclusion of the California Air Resources Board (CARB) Stage 1 Ultra-Low NOX program, there continues to be a commitment for identifying potential pathways to demonstrate 0.02 g/hp-hr NOX emissions. The Stage 1 program focused on achieving the Ultra-Low NOX (ULN) levels utilizing a turbo-compound (TC) engine, which required the integration of novel catalyst technologies and a supplemental heat source. While the aftertreatment configuration provided a potential solution to meet the ULN target, a complicated approach was required to overcome challenges from low temperature exhaust. The Stage 3 program leverages a different engine architecture more representative of the broader heavy-duty industry to meet the Phase 2 Greenhouse Gas (GHG) targets and to simplify the ULN aftertreatment solution. The following work will discuss the aftertreatment technology evaluation, down selection criteria, and the emission results for the candidate ULN systems
Technical Paper

The Effect of Heavy-Duty Diesel Cylinder Deactivation on Exhaust Temperature, Fuel Consumption, and Turbocharger Performance up to 3 bar BMEP

2020-04-14
2020-01-1407
Diesel Cylinder Deactivation (CDA) has been shown in previous work to increase exhaust temperatures, improve fuel efficiency, and reduce engine-out NOx for engine loads up to 3 bar BMEP. The purpose of this study is to determine whether or not the turbocharger needs to be altered when implementing CDA on a diesel engine. This study investigates the effect of CDA on exhaust temperature, fuel efficiency, and turbocharger performance in a 15L heavy-duty diesel engine under low-load (0-3 bar BMEP) steady-state operating conditions. Two calibration strategies were evaluated. First, a “stay-hot” thermal management strategy in which CDA was used to increase exhaust temperature and reduce fuel consumption. Next, a “get-hot” strategy where CDA and elevated idle speed was used to increase exhaust temperature and exhaust enthalpy for rapid aftertreatment warm-up.
Technical Paper

A Controls Overview on Achieving Ultra-Low NOx

2020-04-14
2020-01-1404
The California Air Resources Board (CARB)-funded Stage 3 Heavy-Duty Low NOX program focusses on evaluating different engine and after-treatment technologies to achieve 0.02g/bhp-hr of NOX emission over certification cycles. This paper highlights the controls architecture of the engine and after-treatment systems and discusses the effects of various strategies implemented and tested in an engine test cell over various heavy-duty drive cycles. A Cylinder De-Activation (CDA) system enabled engine was integrated with an advanced after-treatment controller and system package. Southwest Research Institute (SwRI) had implemented a model-based controller for the Selective Catalytic Reduction (SCR) system in the CARB Stage 1 Low-NOX program. The chemical kinetics for the model-based controller were further tuned and implemented in order to accurately represent the reactions for the catalysts used in this program.
Technical Paper

Evaluation of Cylinder Deactivation on a Class 8 Truck over Light Load Cycles

2020-04-14
2020-01-0800
Selective Catalytic Reduction (SCR) systems provide excellent NOX control for diesel engines provided the exhaust aftertreatment inlet temperature remains at 200° C or higher. Since diesel engines run lean, extended light load operation typically causes exhaust temperatures to fall below 200° C and SCR conversion efficiency diminishes. Heated urea dosing systems are being developed to allow dosing below 190° C. However, catalyst face plugging remains a concern. Close coupled SCR systems and lower temperature formulation of SCR systems are also being developed, which add additional expense. Current strategies of post fuel injection and retarded injection timing increases fuel consumption. One viable keep-warm strategy examined in this paper is cylinder deactivation (CDA) which can increase exhaust temperature and reduce fuel consumption.
Technical Paper

Improving Heavy Duty Natural Gas Engine Efficiency: A Systematic Approach to Application of Dedicated EGR

2020-04-14
2020-01-0818
The worldwide trend of tightening CO2 emissions standards and desire for near zero emissions is driving development of high efficiency natural gas engines for a low CO2 replacement of traditional diesel engines. A Cummins Westport ISX12 G was previously converted to a Dedicated EGR® (D-EGR®) configuration with two out of the six cylinders acting as the EGR producing cylinders. Using a systems approach, the combustion and turbocharging systems were optimized for improved efficiency while maintaining the potential for achieving 0.02 g/bhp-hr NOX standards. A prototype variable nozzle turbocharger was selected to maintain the stock torque curve. The EGR delivery method enabled a reduction in pre-turbine pressure as the turbine was not required to be undersized to drive EGR. A high energy Dual Coil Offset (DCO®) ignition system was utilized to maintain stable combustion with increased EGR rates.
Journal Article

Development and Demonstration of a Class 6 Range-Extended Electric Vehicle for Commercial Pickup and Delivery Operation

2020-04-14
2020-01-0848
Range-extended hybrids are an attractive option for medium- and heavy-duty commercial vehicle fleets because they offer the efficiency of an electrified powertrain with the driving range of a conventional diesel powertrain. The vehicle essentially operates as if it was purely electric for most trips, while ensuring that all commercial routes can be completed in any weather conditions or geographic terrain. Fuel use and point-source emissions can be significantly reduced, and in some cases eliminated, as many shorter routes can be fully electrified with this architecture. Under a U.S. Department of Energy (DOE)-funded project for Medium- and Heavy-Duty Vehicle Powertrain Electrification, Cummins has developed a plug-in hybrid electric Class 6 truck with a range-extending engine designed for pickup and delivery application.
Technical Paper

Extend Syngas Yield through Increasing Rich Limit by Stratified Air Injection in a Single Cylinder Engine

2020-04-14
2020-01-0958
Dedicated exhaust gas recirculation (D-EGR®) concept developed by Southwest Research Institute (SwRI) has demonstrated a thermal efficiency increase on many spark-ignited engines at both low and high load conditions. The syngas (H2+CO) produced in the dedicated cylinder (D-cyl) by rich combustion helps to stabilize combustion at highly dilute conditions at low loads and mitigate knock at high loads. The dedicated cylinder with 25% EGR can typically run up to equivalence ratio of 1.4, beyond which the combustion becomes unstable. By injecting fresh air near the spark plug gap at globally rich conditions, a locally lean or near-stoichiometric mixture can be achieved, thus facilitating the ignitability of the mixture and increasing combustion stability. With more stable combustion a richer global mixture can be introduced into the D-cyl to generate higher concentrations of syngas. This in turn can further improve the engine thermal efficiency.
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