Refine Your Search

Topic

Search Results

Technical Paper

λDSF: Dynamic Skip Fire with Homogeneous Lean Burn for Improved Fuel Consumption, Emissions and Drivability

2018-04-03
2018-01-0891
Dynamic skip fire (DSF) has shown significant fuel economy improvement potential via reduction of pumping losses that generally affect throttled spark-ignition (SI) engines. In DSF operation, individual cylinders are fired on-demand near peak efficiency to satisfy driver torque demand. For vehicles with a downsized-boosted 4-cylinder engine, DSF can reduce fuel consumption by 8% in the WLTC (Class 3) drive cycle. The relatively low cost of cylinder deactivation hardware further improves the production value of DSF. Lean burn strategies in gasoline engines have also demonstrated significant fuel efficiency gains resulting from reduced pumping losses and improved thermodynamic characteristics, such as higher specific heat ratio and lower heat losses. Fuel-air mixture stratification is generally required to achieve stable combustion at low loads.
Technical Paper

mDSF: Improved Fuel Efficiency, Drivability and Vibrations via Dynamic Skip Fire and Miller Cycle Synergies

2019-04-02
2019-01-0227
mDSF is a novel cylinder deactivation technology developed at Tula Technology, which combines the torque control of Dynamic Skip Fire (DSF) with Miller cycle engines to optimize fuel efficiency at minimal cost. mDSF employs a valvetrain with variable valve lift plus deactivation and novel control algorithms founded on Tula’s proven DSF technology. This allows cylinders to dynamically alternate among 3 potential states: high-charge fire, low-charge fire, and skip (deactivation). The low-charge fire state is achieved through an aggressive Miller cycle with Early Intake Valve Closing (EIVC). The three operating states in mDSF can be used to simultaneously optimize engine efficiency and driveline vibrations. Acceleration performance is retained using the all-cylinder, high-charge firing mode.
Technical Paper

Smart Cylinder Deactivation Strategies to Improve Fuel Economy and Pollutant Emissions for Diesel-Powered Applications

2019-09-09
2019-24-0055
Further improvement of the trade-off between CO2 and pollutant emissions is the main motivating factor for the development of new diesel engine concepts, from light-duty car applications via medium-duty commercial vehicles up to large long-haul trucks. The deactivation of one or more cylinders of a light-duty diesel engine during low load operation can be a sophisticated method to improve fuel economy and reduce especially NOx emissions at the same time. Dynamic Skip Fire (DSF) is an advanced cylinder deactivation technology, where the decision to fire or skip singular units of a multi-cylinder engine architecture is taken just prior to each firing opportunity, based on a balanced rankling of multiple input parameters.
Technical Paper

Port Injection of Water into a DI Hydrogen Engine

2015-04-14
2015-01-0861
Hydrogen fueled internal combustion engines have potential for high thermal efficiencies; however, high efficiency conditions can produce high nitrogen oxide emissions (NOx) that are challenging to treat using conventional 3-way catalysts. This work presents the results of an experimental study to reduce NOx emissions while retaining high thermal efficiencies in a single-cylinder research engine fueled with hydrogen. Specifically, the effects on engine performance of the injection of water into the intake air charge were explored. The hydrogen fuel was injected into the cylinder directly. Several parameters were varied during the study, including the amount of water injected into the intake charge, the amount of fuel injected, the phasing of the fuel injection, the number of fuel injection events, and the ignition timing. The results were compared with expectations for a conventionally operated hydrogen engine where load was controlled through changes in equivalence ratio.
Technical Paper

Multi-Dimensional Modeling of NO and Soot Emissions with Detailed Chemistry and Mixing in a Direct Injection Natural Gas Engine

2002-03-04
2002-01-1112
This work reports the development and application of multi-dimensional ignition, combustion and emissions models that account for detailed chemistry and mixing effects in a direct injection engine simulation. A detailed chemical reaction mechanism, consisting of 24 species and 104 reactions, is used for increased accuracy of emissions predictions. Turbulent combustion is represented using a modified Eddy Dissipation Concept (EDC) model to account for mixing effects. The soot model includes all aspects of soot formation and destruction. Particle transport equations are used to realistically track transport of the soot particles formed. All computational sub-models developed in this work have been implemented in a modified version of the KIVA-3V code. In order to illustrate the behavior of the new models, soot and NO emissions have been predicted at different operating conditions by varying injection timing, exhaust gas recirculation (EGR) and injection pressure.
Technical Paper

Modeling and Simulation of Airflow Dynamics in a Dynamic Skip Fire Engine

2015-04-14
2015-01-1717
Dynamic skip fire is a control method for internal combustion engines in which engine cylinders are selectively fired or skipped to meet driver torque demand. In this type of engine operation, fueling, and possibly intake and exhaust valves of each cylinder are actuated on an individual firing opportunity basis. The ability to operate each cylinder at or near its best thermal efficiency, and to achieve flexible control of acoustic and vibrational excitations has been described in previous publications. Due to intermittent induction and exhaust events, air induction and torque production in a DSF engine can vary more than conventional engines on a cycle-to-cycle basis. This paper describes engine thermofluid modeling for this type of operation for purposes of air flow and torque prediction.
Journal Article

Method to Compensate Fueling for Individual Firing Events in a Four-Cylinder Engine Operated with Dynamic Skip Fire

2018-04-03
2018-01-1162
Cylinder deactivation in multicylinder spark-ignition (SI) engines leads to increased fuel efficiency at part load by allowing fired cylinders to operate closer to their peak thermal efficiency compared to all-cylinder operation. Unlike traditional cylinder deactivation strategies that are limited to deactivating only certain cylinders, Dynamic Skip Fire (DSF) is an advanced cylinder deactivation control strategy that makes deactivation decisions for every cylinder on an individual firing opportunity basis to best meet driver torque demand while saving fuel and mitigating noise, vibration, and harshness (NVH). During DSF operation, inducted charge air mass can vary for each firing event due to the firing sequence history. To maximize efficiency, cylinder fueling should be adjusted for each firing event in DSF based on the inducted charge air mass for that event.
Journal Article

In-Cylinder Particulate Matter and Spray Imaging of Ethanol/Gasoline Blends in a Direct Injection Spark Ignition Engine

2013-04-08
2013-01-0259
A single-cylinder Direct Injection Spark Ignition (DISI) engine with optical access was used to investigate the effects of ethanol/gasoline blends on in-cylinder formation of particulate matter (PM) and fuel spray characteristics. Indolene was used as a baseline fuel and two blends of 50% and 85% ethanol (by volume, balance indolene) were investigated. Time resolved thermal radiation (incandescence/natural luminosity) of soot particles and fuel spray characteristics were recorded using a high speed camera. The images were analyzed to quantify soot formation in units of relative image intensity as a function of important engine operating conditions, including ethanol concentration in the fuel, fuel injection timing (250, 300 and 320° bTDC), and coolant temperature (25°C and 90°C). Spatially-integrated incandescence was used as a metric to quantify the level of in-cylinder PM formed at the different operating conditions.
Journal Article

Hydrogen DI Dual Zone Combustion System

2013-04-08
2013-01-0230
Internal combustion (IC) engines fueled by hydrogen are among the most efficient means of converting chemical energy to mechanical work. The exhaust has near-zero carbon-based emissions, and the engines can be operated in a manner in which pollutants are minimal. In addition, in automotive applications, hydrogen engines have the potential for efficiencies higher than fuel cells.[1] In addition, hydrogen engines are likely to have a small increase in engine costs compared to conventionally fueled engines. However, there are challenges to using hydrogen in IC engines. In particular, efficient combustion of hydrogen in engines produces nitrogen oxides (NOx) that generally cannot be treated with conventional three-way catalysts. This work presents the results of experiments which consider changes in direct injection hydrogen engine design to improve engine performance, consisting primarily of engine efficiency and NOx emissions.
Journal Article

Highly Turbocharged Gasoline Engine and Rapid Compression Machine Studies of Super-Knock

2016-04-05
2016-01-0686
Super-knock has been a significant obstacle for the development of highly turbocharged (downsized) gasoline engines with spark ignition, due to the catastrophic damage super-knock can cause to the engine. According to previous research by the authors, one combustion process leading to super-knock may be described as hot-spot induced pre-ignition followed by deflagration which can induce detonation from another hot spot followed by high pressure oscillation. The sources of the hot spots which lead to pre-ignition (including oil films, deposits, gas-dynamics, etc.) may occur sporadically, which leads to super-knock occurring randomly at practical engine operating conditions. In this study, a spark plasma was used to induce preignition and the correlation between super-knock combustion and the thermodynamic state of the reactant mixture was investigated in a four-cylinder production gasoline engine.
Technical Paper

High-Speed Imaging Study on the Effects of Internal Geometry on High-Pressure Gasoline Sprays

2020-09-15
2020-01-2111
High-pressure gasoline injection can improve combustion efficiency and lower engine-out emissions; however, the spray characteristics of high-pressure gasoline (>500 bar) are not well known. Effects of different injector nozzle geometry on high-pressure gasoline sprays were studied using a constant volume chamber. Five nozzles with controlled internal flow features including differences in nozzle inlet rounding, conicity, and outlet diameter were investigated. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar. The chamber pressure was varied using nitrogen at ambient temperature and pressures of 1, 5, 10, and 20 bar. Spray development was recorded using diffuse backlit shadowgraph imaging methods.
Technical Paper

High-Speed Imaging Studies of Gasoline Fuel Sprays at Fuel Injection Pressures from 300 to 1500 bar

2018-04-03
2018-01-0294
High-pressure gasoline fuel injection is a means to improve combustion efficiency and lower engine-out emissions. The objective of this study was to quantify the effects of fuel injection pressure on transient gasoline fuel spray development for a wide range of injection pressures, including over 1000 bar, using a constant volume chamber and high-speed imaging. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar into the chamber, which was pressurized with nitrogen at 1, 5, 10, and 20 bar at room temperature (298 K). Bulk spray imaging data were used to quantify spray tip penetration distance, rate of spray tip penetration and spray cone angle. Near-nozzle data were used to evaluate the early spray development.
Technical Paper

Fuel Economy Gains through Dynamic-Skip-Fire in Spark Ignition Engines

2016-04-05
2016-01-0672
Pumping losses are one of the primary energy losses in throttled spark ignition engines. In order to reduce fuel consumption, engine manufacturers are incorporating devices that deactivate the valve-train in some cylinders. In the operating strategies currently implemented in the market, fixed sets of cylinders are deactivated, allowing 2 or 3 operating modes. In contrast, Tula Technology has developed Dynamic Skip Fire (DSF), in which the decision of whether or not to fire a cylinder is decided on a cycle-by-cycle basis. Testing the DSF technology in an independent certified lab on a 2010 GMC Denali, reduces the fuel consumption by 18% on a cycle-average basis, and simultaneously increases the ability to mitigate noise and vibration at objectionable frequencies.
Journal Article

Fast Catalyst Light-Off with Dynamic Skip Fire

2020-04-14
2020-01-0313
Catalytic aftertreatment is commonly used to reduce regulated gas emissions from Internal Combustion (IC) engines. Achieving fast catalyst light-off has always been a challenge for automobile IC engine applications. This paper experimentally studied the thermal management and regulated gas emissions from a Spark Ignition (SI) engine with Dynamic Skip Fire (DSF®) technology during cold start period. The study has found that DSF can increase exhaust gas temperature at the catalyst inlet by up to 100°C, and the exhaust enthalpy by up to 20%. Cold start tailpipe carbon monoxide (CO) and hydrocarbon (HC) emissions can be reduced by 10% to 20% largely due to the increased exhaust gas temperature and enthalpy. Dynamic air pumping can further increase exhaust gas temperature by 30 °C, and can nearly double enthalpy delivered to the catalyst, which reduces cold start HC emissions by more than 50%.
Technical Paper

Extending the Dilution Limit of Spark Ignition Combustion via Fuel Injection during Negative Valve Overlap

2016-04-05
2016-01-0671
Using exhaust gas recirculation (EGR) as a diluent instead of air allows the use of a conventional three-way catalyst for effective emissions reduction. Cooled EGR can also reduce fuel consumption and NOx emissions, but too much cool EGR leads to combustion instability and misfire. Negative valve overlap (NVO) is explored in the current work as an alternative method of dilution in which early exhaust valve closing causes combustion products to be retained in the cylinder and recompressed near top dead center, before being mixed with fresh charge during the intake stroke. The potential for fuel injection during NVO to extend the dilution limit of spark ignition combustion is evaluated in this work using experiments conducted on a 4-cylinder 2.0 L gasoline direct injection engine with variable intake and exhaust valve timing. The results demonstrate fuel injection during NVO can extend the dilution limit, improve brake specific fuel consumption (BSFC), and reduce CO and NOx emissions.
Technical Paper

Evaluation of New High Efficiency Engine Concept with Atkinson Cycle, Cooled EGR and Dynamic Skip Fire

2021-04-06
2021-01-0459
Dynamic Skip Fire (DSF) is a proven cylinder deactivation strategy developed at Tula Technology that, in production, has proven to deliver significant fuel consumption improvements across engine and vehicle platforms. DSF allows cylinders to operate near optimal efficiency by reducing pumping losses and improving combustion stability. The Atkinson cycle is also a well-known strategy to improve thermodynamic efficiency by reducing pumping losses and over-expanding combustion gases. This strategy is commonly implemented with long duration intake cams and late intake valve closing. The Atkinson cycle sacrifices power density in a naturally aspirated engine so displacement is commonly increased. The upsized Atkinson cycle engine still shows significant reduction in fuel consumption at high load but has a fuel consumption penalty at low loads due to increased friction and throttling losses.
Technical Paper

Electrified Dynamic Skip Fire (eDSF): Design and Benefits

2018-04-03
2018-01-0864
Tula’s Dynamic Skip Fire (DSF®) technology combines highly responsive torque control with cylinder deactivation to optimize fuel consumption of spark ignited engines. Through careful control of individual combustion events, engine operation occurs at peak efficiency over the full range of torque demand. A challenge with skip-fire operation is avoiding objectionable noise and vibration. Tula’s DSF technology uses sophisticated firing control algorithms which manage the skip-fire sequence to avoid excitation of the powertrain and vehicle at sensitive frequencies. DSF enables a production-quality driving experience while reducing CO2 emissions by 8-15% with no impact on regulated toxic emissions. Moreover, DSF presents a high value solution for meeting global emissions mandates, with estimated cost less than $40 per percent gain in fuel efficiency.
Technical Paper

Efficiency Improvement of Electric Motor Drives Using Dynamic Motor Drive Technology

2022-03-29
2022-01-0721
Tula Technology has developed a novel, patented motor control strategy called Dynamic Motor Drive (DMD®), which reduces the light-load losses of electric motor drives by intermittently pulsing motor torque. Since passenger vehicles frequently operate at light loads, DMD can significantly reduce the energy consumption of electric vehicles, extending their range. DMD is particularly beneficial for rare-earth-free or reduced-rare-earth permanent magnet (PM)-based electric motor drives, and can help make these less expensive, more environmentally friendly motors range-competitive with traditional PM motors. This paper details the efficiency improvement when DMD is applied to a rare-earth-free synchronous reluctance motor (SynRM). We present recent experimental results to show the loss reduction by DMD in a prototype 8-kW three-phase SynRM, and compare them to simulation results.
Technical Paper

Effects of Fuel Injection Events of Ethanol and Gasoline Blends on Boosted Direct-Injection Engine Performance

2017-10-08
2017-01-2238
Numerous studies have demonstrated the benefits of ethanol in increasing the thermal efficiency of gasoline-fueled spark ignition engines via the higher enthalpy of vaporization and higher knock resistance of ethanol compared with gasoline. This study expands on previous work by considering a split fuel injection strategy with a boosted direct injection spark ignition engine fueled with E0 (100% by volume reference grade gasoline; with research octane number = 91 and motor octane number = 83), E100 (100% by volume anhydrous ethanol), and various splash-blends of the two fuels. Experiments were performed using a production 3-cylinder Ford Ecoboost engine where two cylinders were de-activated to create a single-cylinder engine with a displacement of 0.33 L. The engine was operated over a range of loads with boosted intake manifold absolute pressure (MAP) from 1 bar to 1.5 bar.
Technical Paper

Effects of Engine Speed on Spray Behaviors of the Engine Combustion Network “Spray G” Gasoline Injector

2018-04-03
2018-01-0305
Non-reacting spray behaviors of the Engine Combustion Network “Spray G” gasoline fuel injector were investigated at flash and non-flash boiling conditions in an optically accessible single cylinder engine and a constant volume spray chamber. High-speed Mie-scattering imaging was used to determine transient liquid-phase spray penetration distances and observe general spray behaviors. The standardized “G2” and “G3” test conditions recommended by the Engine Combustion Network were matched in this work and the fuel was pure iso-octane. Results from the constant volume chamber represented the zero (stationary piston) engine speed condition and single cylinder engine speeds ranged from 300 to 2,000 RPM. As expected, the present results indicated the general spray behaviors differed significantly between the spray chamber and engine. The differences must be thoughtfully considered when applying spray chamber results to guide spray model development for engine applications.
X