Fuel efficient thermal management of diesel engine aftertreatment is a significant challenge, particularly during cold start, extended idle, urban driving, and vehicle operation in cold ambient conditions. Aftertreatment systems incorporating NO xmitigating selective catalytic reduction and diesel oxidation catalysts must reach ;250°C to be effective. The primary engine-out condition that affects the ability to keep the aftertreatment components hot is the turbine outlet temperature; however, it is a combination of exhaust flow rate and turbine outlet temperature that impact the warm-up of the aftertreatment components via convective heat transfer. This article demonstrates that cylinder deactivation improves exhaust thermal management during both loaded and lightly loaded idle conditions. Coupling cylinder deactivation with flexible valve motions results in additional benefits during lightly loaded idle operation. Specifically, this article illustrates that at loaded idle, valve motion and fuel injection deactivation in three of the six cylinders enables the following: (1) a turbine outlet temperature increases from ;190°C to 310°C with only a 2% fuel economy penalty compared to the most efficient six-cylinder operation and (2) a 39% reduction in fuel consumption compared to six-cylinder operation achieving the same ;310°C turbine out temperature. Similarly, at lightly loaded idle, the combination of valve motion and fuel injection deactivation in three of the six cylinders, intake/exhaust valve throttling, and intake valve closure modulation enables the following: (1) a turbine outlet temperature increases from ;120°C to 200°C with no fuel consumption penalty compared to the most efficient six-cylinder operation and (2) turbine outlet temperatures in excess of 250°C when internal exhaust gas recirculation is also implemented. These variable valve actuation-based strategies also outperform six-cylinder operation for aftertreatment warm-up at all catalyst bed temperatures. These benefits are primarily realized by reducing the air flow through the engine, directly resulting in higher exhaust temperatures and lower pumping penalties compared to conventional six-cylinder operation. The elevated exhaust temperatures offset exhaust flow reductions, increasing exhaust gas-to-catalyst heat transfer rates, resulting in superior aftertreatment thermal management performance.

Light duty vehicle emission standards are getting more stringent than ever before as stipulated by US EPA Tier 2 Standards and LEV III regulations proposed by CARB. The research in this paper sponsored by US DoE is focused towards developing a Tier 2 Bin 2 Emissions compliant light duty pickup truck with class leading fuel economy targets of 22.4 mpg "City" / 34.3 mpg "Highway". Many advanced technologies comprising both engine and after-treatment systems are essential towards accomplishing this goal. The objective of this paper would be to discuss key engine technology enablers that will help in achieving the target emission levels and fuel economy. Several enabling technologies comprising air-handling, fuel system and base engine design requirements will be discussed in this paper highlighting both experimental and analytical evaluations. Mostly, this paper will focus on steady-state emissions and fuel consumption results that are tied to operating duty cycle with actual vehicle comparisons wherever applicable. GT-Power 1D cycle simulation analysis was done to narrow the turbocharger and air-handling architecture evaluation. The importance of turbocharger matching is critical to achieving both power density and emission goals. This paper highlights the challenges involved in selecting a single stage variable geometry turbocharger capable of delivering a 75hp/liter power density in addition to meeting light duty drive cycle emission requirements. The benefits of low pressure [LP] and high pressure [HP] EGR systems for this light-duty engine architecture will be explored in detail along with outlining the possible strategy of dual loop EGR to reduce overall fuel consumption. On the combustion system development, this paper will highlight the importance of compression ratio, variable swirl architecture, injector nozzle hardware and injection strategy optimization towards meeting the stringent emissions, fuel consumption and noise targets. Fundamental thermodynamic explanations relating the fuel consumption improvements back to closed cycle and open cycle work are also being presented. Also, the paper will discuss challenges involving unburned HC and CO emissions when operating in premixed/low temperature combustion like regimes involving higher EGR rates and early pilot injection timings. Potential solutions to mitigate such undesired emissions have been investigated both analytically and experimentally.

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Human hepatocellular carcinoma cells, HepG2, are often used for drug mediated mitochondrial toxicity assessments. Glucose in HepG2 culture media is replaced by galactose to reveal drug-induced mitochondrial toxicity as a marked shift of drug IC50 values for the reduction of cellular ATP. It has been postulated that galactose sensitizes HepG2 mitochondria by the additional ATP consumption demand in the Leloir pathway. However, our NMR metabolomics analysis of HepG2 cells and culture media showed very limited galactose metabolism. To clarify the role of galactose in HepG2 cellular metabolism, U-13 C 6 -galactose or U-13 C 6glucose was added to HepG2 culture media to help specifically track the metabolism of those two sugars. Conversion to U-13 C 3 -lactate was hardly detected when HepG2 cells were incubated with U-13 C 6 -galactose, while an abundance of U-13 C 3 -lactate was produced when HepG2 cells were incubated with U-13 C 6 -glucose. In the absence of glucose, HepG2 cells increased glutamine consumption as a bioenergetics source. The requirement of additional glutamine almost matched the amount of glucose needed to maintain a similar level of cellular ATP in HepG2 cells. This improved understanding of galactose and glutamine metabolism in HepG2 cells helped optimize the ATP-based mitochondrial toxicity assay. The modified assay showed 96% sensitivity and 97% specificity in correctly discriminating compounds known to cause mitochondrial toxicity from those with prior evidence of not being mitochondrial toxicants. The greatest significance of the modified assay was its improved sensitivity in detecting the inhibition of mitochondrial fatty acid β-oxidation (FAO) when glutamine was withheld. Use of this improved assay for an empirical prediction of the likely contribution of mitochondrial toxicity to human DILI (drug induced liver injury) was attempted. According to testing of 65 DILI positive compounds representing numerous mechanisms of DILI together with 55 DILI negative compounds, the overall prediction of mitochondrial mechanism-related DILI showed 25% sensitivity and 95% specificity.

Heavy-duty over-the-road trucks require periodic active diesel particulate filter regeneration to clean the filter of stored particulate matter. These events require sustained temperatures between 500 and 600°C to complete the regeneration process. Engine operation during typical 65 mile/h highway cruise conditions (1200 rpm/7.6 bar) results in temperatures of approximately 350°C, and can reach approximately 420°C with late fuel injection. This necessitates hydrocarbon fueling of a diesel oxidation catalyst or burner located upstream of the diesel particulate filter to reach the required regeneration temperatures. These strategies require increased fuel consumption, and the presence of a fuel-dosed oxidation catalyst (or burner) between the engine and particulate filter. This paper experimentally demonstrates that, at the highway cruise condition, deactivation of valve motions and fuel injection for two or three (of six) cylinders can instead be used to reach engine outlet temperatures of 520-570°C, a 170-220°C increase compared to normal operation. This is primarily a result of a reduction in the air-to-fuel ratio realized by reducing the displaced cylinder volume through cylinder deactivation.