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Today's engine and combustion process development is closely related to the intake port layout. Combustion, performance and emissions are coupled to the intensity of turbulence, the quality of mixture formation and the distribution of residual gas, all of which depend on the in-cylinder charge motion, which is mainly determined by the intake port and cylinder head design. Additionally, an increasing level of volumetric efficiency is demanded for a high power output. Most optimization efforts on typical homogeneous charge spark ignition (HCSI) engines have been at low loads because that is all that is required for a vehicle to make it through the FTP cycle. However, due to pumping losses, this is where such engines are least efficient, so it would be good to find strategies to allow the engine to operate at higher loads.

This paper compares bulk impulse-torque and 2D planar PIV steady flow-field measurements created by an engine cylinder head and intake system model using a steady-flow bench and evaluates operational aspects of the steady-flow test system. The model included a full-sized intake manifold and cylinder head section from a Chrysler 2.4L PFI four-valve per cylinder engine mounted to an optical cylinder. Two test system operational aspects were evaluated: (1) upstream versus downstream engine location relative to the flowbench (operational modes corresponding to flow bench pulling or pushing through the system), (2) PIV seeding particulate choice. Several dry and oil fog particulates were assessed however, of the options tested, only laboratory grade glass and consumer grade talc allowed long enough operation for practical data acquisition. Tests were performed over lift-over-diameter (L/D) ratios spanning from 0.1 to 0.3.

Modern water injection systems typically deliver water separately from the primary fuel system using a discrete injector either through the intake port or directly to the cylinder. Recently, however, water dilution strategies using fully hydrous fuel systems have been receiving increased attention. Hydrous fuels are water and liquid fuel blends that are fully mixed prior to delivery to the combustion system. Removing water from naturally hydrous fuels such as ethanol requires large amounts of energy; consequently, it is possible to combine water injection with more economical production by leaving some amount of water in the fuel. This paper compares experimentally the water dilution effects on the combustion and emissions characteristics and overall engine performance when delivering the water through either a hydrous fuel blend or discrete port water injection. A 2.4L 4-cylinder NA GDI engine was used in experimental testing.

An investigation into applying a tracer gas method for determining trapping efficiency to 4-stroke engines is carried out. The experimental errors are identified and analyzed. The errors include incomplete cylinder reaction, exhaust instability, and inconsistent exhaust sampling. Tracer gas global kinetic mechanisms are reviewed and used as a means for tracer gas selection. The tracer gases investigated are nitrous oxide (N2O) and monomethylamine (CH3NH2). As a benchmark the oxygen tracer technique is analyzed, where oxygen is used as the tracer. Test results from a GM 5.7 l, 8 cylinder, 4-stroke engine are presented that include measurement of the experimental errors and the trapping efficiency. Of the tracers considered, N2O is determined to be optimal for the engine tested.