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Low NOx and soot free premixed diesel combustion can be realized by increasing ignition delays in low oxygen atmospheres, as well as the combustion here also depends on fuel ignitability. In this report single intermittent spray combustion with primary reference fuels and a normal heptane-toluene blend fuel under several oxygen concentrations in a constant volume combustion vessel was analyzed with high-speed color video and pressure data. Temperature and KL factor distributions are displayed with a 2-D two-color method. The results show that premixing is promoted with a decrease in oxygen concentration, and the local high temperature regions, above 2200 K, as well as the duration of their appearance decreases with the oxygen concentration. With normal heptane, mild premixed diesel combustion can be realized at 15 vol% oxygen and there is little luminous flame.

Diesel Particulate Filter (DPF) has become a key technology in modern diesel vehicles to achieve low emissions, and the performance of DPFs has been improved through considerable efforts by manufacturers. While DPF is essential to meeting the stringent regulations for particulate matter (PM), it has a negative impact on fuel efficiency (FE) due to its periodical regeneration for burning off the accumulated PM in DPF. Hence, detailed assessments on the FE impact of DPF regeneration technologies are necessary to better understand the FE potential of diesel vehicles. However, few quantitative FE studies have been reported regarding the DPF regeneration technologies applied to vehicles introduced into the market. We investigated the influence of the DPF regeneration on FE performance using three new diesel vehicles with different DPF regeneration technologies.

The objective of this program was to improve the HCCI combustion process on a single-cylinder VCR engine by calibrating engine and HCCI operation specific factors such as EGR flow rates, intake air pressure, intake air temperature, compression ratio, etc. Due to the large number of factors to be investigated, a statistical design of experiments method (DoE) was utilized in order to reduce the number of test combinations in the calibration test matrix and, thus, the duration of the engine calibration task. Upon completion of the HCCI engine calibration, the engine was operated through a steady-state test matrix representing vehicle certification test cycles. Weighting factors for each of the test points were applied to estimate the engine performance and emissions in respect to certification requirements.

This paper explores the possibility of on-board fuel classification for fuel property adaptive compression-ignition engine control system. The fuel classifier is designed to on-board classify the fuel that a diesel engine is running, including alternative and renewable fuels such as bio-diesel. Based on this classification, the key fuel properties are provided to the engine control system for optimal control of in-cylinder combustion and exhaust treatment system management with respect to the fuel. The fuel classifier employs engine input-output response characteristics measured from standard engine sensors to classify the fuel. For proof-of-concept purposes, engine input-output responses were measured for three different fuels at three different engine operating conditions. Two neural-network-based fuel classifiers were developed for different classification scenarios. Of the three engine operating conditions tested, two conditions were selected for the fuel classifier to be active.

Four fuels in the gasoline boiling range where tested in a constant volume combustion bomb and a variable compression ratio HCCI engine. The fuels were tested using a port fuel injection system. The results of the experiments defined the range of HCCI operation in terms of the Coefficient of Variation (COV) of IMEP and the maximum rate of pressure rise. The results for the test fuels are compared to each other and to a baseline gasoline. The results are discussed in terms of the effects of the fuel properties (basically, various measure of ignition quality) on the engine heat release rates and efficiencies.

For better understanding of diesel emissions in real world, the effects of driving conditions and fuel properties on diesel emissions were studied. A diesel engine system that is compliant to the Japanese New Short Term Regulation (J-2003 regulation) was used in this study. Major technologies for emission reduction were a common-rail high-pressure fuel injection equipment system, a cooled exhaust gas recirculation (EGR) system and a diesel oxidation catalyst (DOC). Various driving modes with a wide range of average vehicle speeds and accelerations were selected, including US FTP, US Highway, Japanese JC08, Japanese JE05, Tokyo Metropolitan Government #2, #5 and #8. Several kinds of test fuels of which characteristics were drastically changed in distillation range, aromatics content and sulfur content were used. A test fuel that complies with the Category-4 Specification of the World-Wide Fuel Charter (WWFC) was included.

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.

Homogeneous Charge Compression Ignition (HCCI) experiments were performed in a variable compression ratio single cylinder engine. This is the fourth paper resulting from work performed at Southwest Research Institute in this HCCI engine. The experimental variables, in addition to speed and load, included compression ratio, EGR level, intake manifold pressure and temperature, fuel introduction location, and fuel composition. Mixture preparation and start of reaction control were identified as fundamental problems that required non-traditional mixture preparation and control strategies. The effects of the independent variable on the start of reaction have been documented. For fuels that display significant pre-flame reactions, the start of the pre-flame reactions is controlled primarily by the selection of the fuel and the temperature history of the fuel air mixture.

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 effect of sulfur concentration in gasoline fuel on emissions from vehicles equipped with lean NOx catalyst (LNC) was studied. The durability of the emission control systems against sulfur poisoning was evaluated using three recently launched vehicles under mileage accumulation tests. The major elements for the NOx trap function of the lean NOx catalysts evaluated in this study were Ba, Na and/or K. The range of sulfur contents of the test fuels was 3 to 80 ppm. The mileage accumulation was conducted up to 10,000 km mainly with Japanese 11 lap mileage accumulation driving cycle where the average and maximum velocities are 46 and 100 km/h respectively. The effects of vehicle velocity on emissions were also investigated by modifying the mileage accumulation driving cycle. As a result, it was found that the durability of the emission control systems against sulfur poisoning has been remarkably improved with the recently launched vehicles.

Researchers at Southwest Research Institute (SwRI) have been working for the past several years on the fundamental and practical aspects of homogeneous charge compression ignition (HCCI) operation of reciprocating engines. Much of the work has focused on the use of diesel fuel. The work at SwRI has, however, demonstrated that there are fundamental limitations on the use of current diesel fuels in HCCI engines. The results of engine and constant volume combustion bomb experiments are presented and discussed. The engine experiments were used to identify important fuel properties that must be included in a fuel specification for HCCI fuels. The primary properties relate to the distillation characteristics and the ignition characteristics. The engine test provided preliminary guidance on the distillation requirements and an indication of the important ignition requirements.

1 A novel analysis approach called “Regression Density method” was developed for better understanding of fuel property effects on exhaust emission. The approach was applied to diesel emission data obtained in JCAP programs and emission models were conducted to analyze the effects of fuel properties and engine conditions on emissions. By introducing this analysis method, the relationship between density factor and aromatics factor (chemical composition factor) was identified, however, they have been reported previously as dominant factors in fuel properties. The effects of engine conditions and fuel properties on emissions were investigated quantitatively based on the statistically conducted emission models to clarify universal ways to emission reduction. The mechanism of emission formation of vehicles and engines with characteristic behavior was also examined.

Significant reductions of particulate matter (PM) and nitrogen oxides (NOx) emissions from diesel engines have been realized through fueling with water-fuel emulsions. However, the physical and chemical in-cylinder mechanisms that affect these pollutant reductions are not well understood. To address this issue, laser-based and chemiluminescence imaging experiments were performed in an optically-accessible, heavy-duty diesel engine using both a standard diesel fuel (D2) and an emulsion of 20% water, by mass (W20). A laser-based Mie-scatter diagnostic was used to measure the liquid-phase fuel penetration and showed 40-70% greater maximum liquid lengths with W20 at the operating conditions tested. At some conditions with low charge temperature or density, the liquid phase fuel may impinge directly on in-cylinder surfaces, leading to increased PM, HC, and CO emissions because of poor mixing.

An experimental investigation of the effects of partial premixed charge compression ignition (PCCI) combustion and EGR temperature was conducted on a Caterpillar C-12 heavy-duty diesel engine (HDDE). The addition of EGR and PCCI combustion resulted in significant NOx reductions over the AVL 8-mode test. The lowest weighted BSNOx achieved was 2.55 g/kW-hr (1.90 g/hp-hr) using cooled EGR and 20% port fuel injection (PFI). This represents a 54% reduction compared to the stock engine. BSHC and BSCO emissions increased by a factor of 8 and 10, respectively, compared to the stock engine. BSFC also increased by 7.7%. In general, BSHC, BSCO, BSPM, and BSFC increased linearly with the amount of port-injected fuel.

A new combustion concept has been developed and tested for improving the low to moderate load efficiency and NOx emissions of natural gas engines. This concept involves operation of a dual-fuel natural gas engine on Homogeneous Charge Compression Ignition (HCCI) in the load regime of idle up to 35 % of the peak torque. A dual-fuel approach is used to control the combustion phasing of the engine during HCCI operation, and conventional spark-ignited natural gas combustion is used for the high-load regime. This concept has resulted in an engine with power output and high-load fuel efficiency that are unchanged from the base engine, but with a 10 - 15 % improvement to the low to moderate load fuel efficiency. In addition, the engine-out NOx emissions during HCCI operation are over 90% lower than on spark-ignited natural gas operation over the equivalent load range.

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant.

This paper reports on the third part of a continued study (SAE Papers 961182, 971636) to develop the Ignition Quality Tester (IQT™). Past research has shown that this automated laboratory/refinery apparatus can be used to accurately predict the cetane number of middle distillates and alternative fuels using small sample volumes (< 50 mL). The paper reports on the main objective of a study performed by Advanced Engine Technology Ltd. (AET), in co-operation with its research partners. The primary research objective of this work is to further the understanding of fuel preparation (fuel air mixing) and start of combustion processes in the IQT™. Key to this understanding is the manner in which single molecule compounds and full boiling-range diesel fuels behave during these processes. Insights are provided into the manner in which the American Society for Testing and Materials (ASTM) D-613 primary reference fuels (PRFs) undergo fuel preparation and start of combustion in the IQT™.

The engine selected for this work was a Caterpillar 3176 engine. Engine exhaust emissions, performance, and heat release rates were measured as functions of engine configuration, engine speed and load. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to achieve a NOx emissions level of 2.5 gm/hp-hr. Measurements were performed at 7 different steady-state, speed-load conditions on thirteen different test fuels. The fuel matrix was statistically designed to independently examine the effects of the targeted fuel properties. Cetane number was varied from 40 to 55, using both natural cetane number and cetane percent improver additives. Aromatic content ranged from 10 to 30 percent in two different forms, one in which the aromatics were predominantly mono-aromatic species and the other, where a significant fraction of the aromatics were either di- or tri-aromatics.

Methods to reduce direct injected diesel engine emissions in the combustion chamber will be discussed in this paper. The following NOx emission reduction technologies will be reviewed: charge air chilling, water injection, and exhaust gas recirculation (EGR). Emphasis will be placed on the development of an EGR system and the effect of EGR on NOx and particulates. The lower limit of NOx that can be obtained using conventional diesel engine combustion will be discussed. Further reductions in NOx may require changing the combustion process from a diffusion flame to a homogeneous charge combustion system.