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With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

An experimental study was conducted to characterize the dynamics and spray behavior of a wide range of minisac and Valve-Covered-Orifice (VCO) nozzles using a high-pressure diesel common-rail system. The measurements show that the resultant injection-rate is strongly dependent on common-rail pressure, nozzle hole diameter, and nozzle type. For split injection the dwell between injections strongly affects the second injection in regards to the needle lift profile and the injected fuel amount. The minisac nozzle can be used to achieve shorter pilot injections at lower common-rail pressures than the VCO nozzle. Penetration photographs of spray development in a high pressure, optical spray chamber were obtained and analyzed for each test condition. Spray symmetry and spray structure were found to depend significantly on the nozzle type.

The current extensive revisitation of the application of gasoline direct-injection to automotive, four-stroke, spark-ignition engines has been prompted by the availability of technological capabilities that did not exist in the late 1970s, and that can now be utilized in the engine development process. The availability of new engine hardware that permits an enhanced level of computer control and dynamic optimization has alleviated many of the system limitations that were encountered in the time period from 1976 to 1984, when the capabilities of direct-injection, stratified-charge, spark-ignition engines were thoroughly researched. This paper incorporates a critical review of the current worldwide research and development activities in the gasoline direct-injection field, and provides insight into new areas of technology that are being applied to the development of both production and prototype engines.

The requirement of meeting the emission standards for low emission vehicles (LEV) and ultra low emission vehicles (ULEV) has resulted in a more stringent examination of all elements of the automotive internal combustion engine that contribute to emission formation. The fuel system, as one of the key elements, is the subject of renewed and expanded research in an effort to understand and optimize the important parameters. Only through such enhanced understanding of the basic processes of fuel injection, metering, atomization, targeting, pulse-to-pulse variability and induction of fuel under cold, normal and elevated temperature conditions can the very low emissions of today's vehicles be further reduced to ULEV values.

The process of deposit-induced, fuel-flow reduction in multiport fuel injectors of the director-plate type was investigated both experimentally and analytically in order to understand both the flow-reduction mechanism and the non-linear variation in flow reduction with engine operating time. Injectors that had accumulated deposits in previous extended engine testing utilizing a rapid-plugging fuel were flow-tested, and the orifice plates from two of the injectors containing deposits were examined using a scanning electron microscope. A thin, carbonaceous deposit protruding into the flow paths of the orifices was found to be present on the downstream face of the orifice plate, but not present within the fuel orifices or on the upstream surface of the plate. Based upon these observations, calculations were made using a fluid flow model of an orifice plate with deposits.

An experimental investigation of the effects of injector type and orientation, engine speed, in-cylinder air swirl, compression pressure, and fuel type has been conducted in motored visualization engines. A fuel-spray visualization system has been developed and utilized to obtain high-speed stroboscopic movies of the injection and penetration events. Significantly different interactions between the fuel spray and the in-cylinder air motions were found to result from changes in air-swirl ratio, nozzle geometry and injection timing. The maximum spray-tip velocity was found to occur downstream from the injector tip for all conditions tested. For applications requiring minimum fuel-spray penetration, the impinging-jet injector was found to be the most promising candidate.

The object of this research was to learn more about the effects of mixture motion upon ignition in spark ignited piston engines, and to determine how variations in mixture velocity alter the combustion process. To provide effective means for producing and measuring the mixture velocity, all tests were made in a constant volume bomb, using mixtures of propane and air. The effects of mixture motion on the lean spark ignition limit, rate of pressure rise, and burning time were determined for mixture ratios ranging from stoichiometric to the lean limit. The mixture pressures corresponded to those in Otto cycle engines at the time of spark occurrence. The results reveal that a mixture velocity of 50 fps, relative to the spark plug, requires an enrichment of 17% with respect to the stagnant lean limit. Increases in mixture velocity were found to greatly increase the rate of pressure rise during combustion. This effect was more pronounced for lean mixtures than for stoichiometric mixtures.