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Condensation of fuel vapor on the cold surfaces within the combustion chamber is investigated as a possible mechanism for increased HC emissions from SI engines during cold start. A one-dimensional, transient, mass diffusion analysis is used to examine the condensation of single-species fuels on the surfaces of the combustion chamber as the pressure within the cylinder rises during compression and combustion, and re-vaporization during expansion, blowdown, and exhaust. The effects of wall temperature, fuel volatility, and engine load and speed on this mechanism are also discussed. This analysis shows that low-volatility fuel components can condense on the surfaces of the combustion chamber when the surface temperatures are sufficiently low. This condensed fuel may re-vaporize during the power and exhaust strokes, or it may remain in the combustion chamber until surface temperatures rise, perhaps tens of seconds later.

Manufacturers of heavy-duty diesel engines for sale in the United States face an unprecedented reduction in emissions in 2007 and in 2010. Compared to today's levels, a 90% reduction in particulate matter (PM) must be achieved by 2007, and a 90% reduction in nitric oxides (NOx) must be achieved by 2010. This paper focuses on the technology solutions possible for engine makers for the interim 2007-2009 timeframe and discusses the additional NOx reduction strategies for a 2010 compliant engine. The possibility of achieving a larger portion of the interim 2007-2009 NOx standard through in-cylinder control methods rather than by NOx exhaust treatment is discussed. High levels of exhaust gas recirculation (EGR) and advanced injection strategies to modify the conventional diesel combustion process are just two processes that can be accommodated in many of today's engine designs.

A technology path has been identified for development of a high efficiency, durable, gasoline engine, targeted at achieving performance and emissions levels necessary to meet heavy-duty, on-road standards of the foreseeable future. Initial experimental and numerical results for the proposed technology concept are presented. This work summarizes internal research efforts conducted at Southwest Research Institute. An alternative combustion system has been numerically and experimentally examined. The engine utilizes gasoline as the fuel, with a combination of enabling technologies to provide high efficiency operation at ultra-low emissions levels. The concept is based upon very highly-dilute combustion of gasoline at high compression ratio and boost levels. Results from the experimental program have demonstrated engine-out NOx emissions of 0.06 g/hp/hr, at single-cylinder brake thermal efficiencies (BTE) above thirty-four percent.

The impingement of liquid fuel onto the surfaces of the combustion chamber (wall-wetting) has been shown to be an important source of HC emissions from direct-injected SI engines, and can even result in pool fires and diffusion flames. Some degree of wall wetting, particularly on the piston top, is believed to occur in every current DIG engine design, but the behavior of the wall-bound fuel throughout the engine cycle is poorly understood. The goal of this study was to gain a better understanding of the fundamental interaction between liquid fuel droplets and the piston under engine-like conditions, by observing the vaporization of individual fuel drops as the surface temperature and ambient pressures were varied in a controlled environment. The vaporization of several single-component fuels, binary mixtures, and multi-component fuels was examined in the range of surface temperatures between 50 and 300 °C and ambient pressures between 50 and 1270 kPa (abs).

Because only the unburned gases in the crevices can contribute to hydrocarbon emissions, a model was developed that can be used to determine the temporal and spatial histories of both burned gas and unburned gas flow into and out of the piston-liner crevices. The burned fraction in the top-land is primarily a function of engine design. Burned gases continue to get packed into the inter-ring volume until well after the end of combustion and the unburned fuel returned to the chamber from this source depends upon both the position of the top ring end gap relative to the spark plug and of the relative positions of the end gaps of the compression rings with respect to each other. Because the rings rotate, and because the fuel that returns to the chamber from the inter-ring crevice dominates the sources between BDC and IVO when conditions are unfavorable to in-cylinder oxidation, these represent two sources of variability in the HC emissions.

A combined, experimental and numerical program is presented. This work summarizes an internal research effort conducted at Southwest Research Institute. Meeting new, stringent emissions regulations for diesel engines requires a way to reduce NOx and soot emissions. Most emissions reduction strategies reduce one pollutant while increasing the other. Water injection is one of the few promising emissions reduction techniques with the potential to simultaneously reduce soot and NOx in diesel engines. While it is widely accepted that water reduces NOx via a thermal effect, the mechanisms behind the reduction of soot are not well understood. The water could reduce the soot via physical, thermal, or chemical effects. To aid in developing water injection strategies, this project's goal was to determine how water enters the soot formation chemistry.

Southwest Research Institute (SwRI) is exploring the feasibility of extending the performance and fuel efficiency of the spark ignition (SI) engine to match that of the emission constrained compression (CI) engine, whilst retaining the cost effective 3-way stoichiometric aftertreatment systems associated with traditional SI light duty engines. The engine concept, which has a relatively high compression ratio and uses heavy EGR, is called “HEDGE”, i.e. High Efficiency Durable Gasoline Engine. Whereas previous SwRI papers have been medium and heavy duty development focused, this paper uses results from simulations, with some test bed correlations, to predict multicylinder torque curves, brake thermal efficiency and NOx emissions as well as knock limit for light and medium duty applications.

SwRI has developed a new technology concept involving the use of high EGR rates coupled with a high-energy ignition system in a gasoline engine to improve fuel economy and emissions. Based on a single-cylinder study [1], this study extends the concept of a high compression ratio gasoline engine with EGR rates > 30% and a high-energy ignition system to a multi-cylinder engine. A 2000 MY Isuzu Duramax 6.6 L 8-cylinder engine was converted to run on gasoline with a diesel pilot ignition system. The engine was run at two compression ratios, 17.5:1 and 12.5:1 and with two different EGR systems - a low-pressure loop and a high pressure loop. A high cetane number (CN) diesel fuel (CN=76) was used as the ignition source and two different octane number (ON) gasolines were investigated - a pump grade 91 ON ((R+M)/2) and a 103 ON ((R+M)/2) racing fuel.

Tremendous amount of useful information can be extracted from the cylinder pressure signal for engine combustion control. However, the physical cylinder pressure sensors are undesirably expensive and their health need to be monitored for fault diagnostic purpose as well. This paper presents the results of the development of a virtual cylinder pressure sensor (VCPS) with individual variable-oriented independent estimators. Two neural network-based independent cylinder pressure related variable estimators were developed and verified at steady state. The results show that these models can predict the variables correctly compared with the extracted variables from the measured physical cylinder pressure sensor signal. Good generalization capabilities of the developed models are observed in the sense that the models work well not only for the training data set but also for the new inputs that they have never been exposed to before.

Recent advances in Variable Valve Actuation (VVA) methods have led to development of optimized valve timing strategies for a broad range of engine operating conditions. This study focuses on the cold-start period, which begins at engine cranking and lasts for approximately 1 minute thereafter. Cold-start is characterized by poor mixture preparation due to low component temperatures, aggravated by fixed valve timing which has historically been compromised to give optimal warm engine operation. In this study, intake cam phasing was varied to explore the potential benefit in hydrocarbon emissions and driveability obtainable for cold-start. A simple experimental approach was used to investigate the potential emissions benefits realizable through intake cam phasing. High speed cylinder pressure and Fast Flame Ionization Detector (FFID) engine-out hydrocarbon (HC) measurements were made to characterize instantaneous cold-start emissions and driveability.

Large reductions in low-load NOx emissions can be obtained by replacing conventional Diesel or spark ignited combustion by HCCI combustion in reciprocating engines. Currently, HCCI combustion is limited to operating conditions with lean air/fuel ratios or large amounts of EGR. However, a numerical model shows that, even if high equivalence ratio HCCI operation were satisfactorily attained, the NOx reduction potential vs. DI-Diesel combustion would be much smaller. Thus, high-load HCCI operation may best be obtained through highly boosted fuel-lean operation. Alternatively, HCCI combustion may be suited well for “dual mode” engine applications, in which spark ignition or conventional Diesel combustion is used to obtain full load. Avoiding wall impingement with heavy fuels is critical for achieving good emissions and fuel consumption, and it appears that a large degree of mixture inhomogeneity can be tolerated from a NOx benefit standpoint.