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Statistically designed experiments were run in a single-cylinder engine to understand the reason for the decrease in exhaust mass HC emissions found in the Auto/Oil Program with decreasing 90% distillation temperature (T90) of gasoline. Besides T90, the effects of mixture preparation, equivalence ratio, and ambient temperature on emissions and fuel consumption were measured. HC emissions were higher with PFI than with premixed charge, but decreasing T90 decreased HC emissions with both premixed charge and PFI. Rich mixture and low ambient temperature increased HC emissions. Speciated exhaust HC measurements indicate that incomplete vaporization of heavy components of the gasoline (C8-C10 alkanes, C6-C9 aromatics and alkenes) was responsible for higher HC emissions.

This paper describes engine research - which supports our program to develop a gasoline engine management system (EMS) with an on-board reformer to provide near-zero tailpipe emissions. With this approach, the reformer converts gasoline (or another hydrocarbon-containing fuel) into reformate, containing hydrogen and CO. Reformate has very wide combustion limits to enable SI engine operation under very dilute conditions (either ultra-lean or with heavy EGR concentrations). In previous publications, we have presented engine dynamometer results showing very low emissions with bottled reformate. This paper shows the sensitivity of engine emissions and performance to operating near the dilute limit with H2 enrichment using both bottled reformate and an actual reformer prototype.

A unique, temperature controlled, single-cylinder engine test facility was designed and constructed to simulate cold starting of a car engine. The temperature of the coolant, oil, fuel and air used by the engine can be individually controlled to -29°C. Moreover, the engine is enclosed in a temperature controlled insulated chamber. With this facility the conditions that occur in a car engine as it cranks and starts, can be quickly duplicated and maintained for detailed study. The supply equivalence ratio values for starting the engine were determined using either gasoline with port fuel injection or propane as a premixed charge. For gaseous propane, the supply equivalence ratio for starting was nearly constant at all temperatures studied. However, for gasoline the supply equivalence ratio for starting increased as the temperature was lowered. The significance of these findings is discussed.

Monochromatic ultraviolet (UV) absorbance, temperature, and pressure histories of unburned gas in a single cylinder CFR engine under motored, fired, and autoignition conditions were recorded on a multichannel magnetic tape recorder. Isooctane, cyclohexane, ethane, n-hexane, n-heptane, 75 octane number (ON), 50 ON, and 25 ON blends of primary reference fuels (PRF) were studied. Under knocking or autoignition conditions a critical absorbance at 2600 A was found, whose magnitude was independent of engine operating variables and dependent only on the knock resistance of the fuel. This absorbance increased rapidly when a certain temperature level was exceeded during the exothermic preflame reactions.

Nitrogen-free and nitrogen-doped fuels were investigated using a single-cylinder, spark-ignition engine, and gasoline and diesel-powered vehicles. The single-cylinder engine experiments showed that only NO (nitric oxide) emissions were affected by nitrogen in the fuel and that the percentage of fuel nitrogen converted to NO (PNCNO) ranged from about 5 to 100. Generally, PNCNO increased when equivalence ratio, concentration of nitrogen in the fuel, engine load, or compression ratio decreased; PNCNO also increased as the level of EGR or engine speed increased, or as spark timing was retarded from MBT. The vehicle experiments showed PNCNO to be substantially higher (∼80-90) in gasoline engines than in a diesel engine (∼35), and that equivalence ratio, fuel-nitrogen concentration and EGR affected PNCNO in a multi-cylinder gasoline engine in the same manner as in the single-cylinder engine.

Statistically designed experiments with a port fuel injected, single-cylinder engine were run to determine the effects of injector-, engine-, and fuel-related variables on exhaust smoke and hydrocarbon (HC) emissions. Among injector-related variables, targeting the fuel spray at the inlet valve centerline toward the valve head resulted in low smoke and HC emissions. These factors apparently help break up the fuel spray and they help subsequent vaporization of the fuel droplets. Among engine-related variables, high coolant temperatures and lean mixtures resulted in less smoke and HC emissions, probably because of better fuel vaporization. Gasolines with aromaticity and 90% point close to the maximum of the ranges of commercial gasolines significantly increased HC and smoke emissions compared with gasolines representing the average or minimum values, of these ranges.

This paper first reports on the benchmarking of a gasoline- fueled vehicle currently for sale in California that is certified to ULEV standards. Emissions data from this vehicle indicate the improvements necessary over current technology to meet SULEV tailpipe standards. Tests with this vehicle also show emissions levels with current technology under off-cycle conditions representative of real-world use. We then present Delphi's strategy of on-board partial oxidation (POx) reforming with gasoline-fueled, spark-ignition engines. On-board reforming provides a source of hydrogen fuel. Tests were run with bottled gas simulating the output of a POx reformer. Results show that an advanced Engine Management System with a small on-board reformer can provide very low tailpipe emissions both under cold start and warmed-up conditions using relatively small amounts of POx gas. The data cover both normal US Federal Test Procedure (FTP) conditions as well as more extreme, off-cycle operation.

This paper describes recent progress in our program to develop a gasoline-fueled vehicle with an on-board reformer to provide near-zero tailpipe emissions. An on-board reformer converts gasoline (or another hydrocarbon-containing fuel) into reformate, containing hydrogen (H2) and carbon monoxide (CO). Reformate has very wide combustion limits to enable SI engine operation under very dilute conditions (either ultra-lean or with heavy exhaust gas recirculation (EGR) concentrations). In previous publications, we have presented engine dynamometer results showing very low emissions with bottled reformate. This paper shows results from an engine linked to an experimental, fast start-up reformer. We present both performance data for the reformer as well as engine emissions and performance results. Program results continue to show an on-board reforming system to be an attractive option for providing near-zero tailpipe emissions to meet low emission standards.