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Prior work in the literature have shown that pre-chamber spark plug technologies can provide remarkable improvements in engine performance. In this work, three passively fueled pre-chamber spark plugs with different pre-chamber geometries were investigated using in-cylinder high-speed imaging of spectral emission in the visible wavelength region in a single-cylinder direct-injection spark-ignition gasoline engine. The effects of the pre-chamber spark plugs on flame development were analyzed by comparing the flame progress between the pre-chamber spark plugs and with the results from a conventional spark plug. The engine was operated at fixed conditions (relevant to federal test procedures) with a constant speed of 1500 revolutions per minute with a coolant temperature of 90 oC and stoichiometric fuel-to-air ratio. The in-cylinder images were captured with a color high-speed camera through an optical insert in the piston crown.

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 designated as: High Fire, Low Fire, and Skip (deactivation). The Low 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 Fire mode. mDSF can be implemented cost-effectively using an asymmetric intake valve lift strategy, with one high-flow power charging port and one high-efficiency Miller port.

Injecting liquid water into a fuel/air charge is a means to reduce NOx emissions. Such strategies are particularly important to hydrogen internal combustion engines, as engine performance (e.g., maximum load) can be limited by regulatory limits on NOx. Experiments were conducted in this study to quantify the effects of direct injection of water into the combustion chamber of a port-fueled, hydrogen IC engine. The effects of DI water injection on NOx emissions, load, and engine efficiency were determined for a broad range of water injection timing. The amount of water injected was varied, and the results were compared with baseline data where no water injection was used. Water injection was a very effective means to reduce NOx emissions. Direct injection of water into the cylinder reduced NOx emissions by 95% with an 8% fuel consumption penalty, and NOx emissions were reduced by 85% without any fuel consumption penalty.

Combined direct and port fuel injection (i.e., dual injection) in spark ignition engines is of increasing interest due to the advantages for fuel flexibility and the individual merits of each system for improving engine performance and reducing engine-out emissions. Greater understanding of the impact of dual injection will enable deriving the maximum benefit from the two injection systems. This study investigates the effects of dual injection on combustion, especially knock propensity and tolerance to exhaust gas recirculation (EGR) dilution at different levels of EGR. A baseline for comparison with dual injection results was made using direct injection fueling only. A splash blended E20 fuel was used for the direct injection only tests. For the dual injection tests, gasoline, representing 80% by volume of the total fuel, was injected using the direct injector, and ethanol, representing 20% by volume of the total fuel, was injected using the port fuel injector.

Dynamic skip fire (DSF) is an advanced cylinder deactivation technology where the decision to fire or skip a singular cylinder of a multi-cylinder engine is made immediately prior to each firing opportunity. A DSF-equipped engine features the ability to selectively deactivate cylinders on a cylinder event-by-event basis in order to match the requested torque demand at optimum fuel efficiency while maintaining acceptable noise, vibration and harshness (NVH). Dynamic Skip Fire (DSF) has already shown significant fuel economy improvements for throttled spark-ignition engines. This paper explores the potential benefits of DSF technology in improving fuel economy while maintaining ultra-low tailpipe emissions for light-duty (LD) Diesel powertrains.

Syngas (synthesis gas) aided combustion from various fuel reforming strategies is of increasing interest in boosted lean burn SI engines due to its impact on dilution tolerance and knock resistance. Due to the interest in reformed fuels, more concrete understanding of how to leverage syngas supplementation under various lean conditions is essential to optimize engine performance and derive the most benefit from the availability of syngas in the combustion process. While the impact of syngas supplementation on combustion stability has been studied adequately, detailed understanding of the impact of syngas on knocking is still limited. Hence, this study investigates the effect of syngas (H2/CO) addition on knock tendency under boosted EGR (Exhaust Gas Recirculation) and air diluted conditions. Syngas amount is controlled on an energy basis from 0% to 15% to compare the difference between EGR and air dilution.

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.

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.

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%.

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.

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.

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.

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.

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.

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.