An experimental investigation of the airflow through various axisymmetric intake ports of a motored reciprocating engine is reported. Detailed velocity field measurements obtained by laser Doppler anemometry and for steady and various unsteady flow conditions are presented together with valve discharge coefficients from steady flow tests. The results showed that over the lift range investigated the valve flow exhibited various regimes indicated by the changes in the flow pattern at the valve exit. With a 45-deg seat angle, four regimes were identified compared to three in the case of a 60-deg valve. The overall behavior of the 45-deg valve, however, was found to be generally better. Rounding of the edges of the 45-deg valve reduced the number of flow regimes to two with marked improvements on discharge coefficient. The flow angle at the valve exit depended less on the flow regimes and more on the cylinder confinement, in the absence of which the transition from one regime to another was delayed. The mean flow pattern at the valve exit was found to be insensitive to flow unsteadiness, piston confinement and valve operation and thus could be predicted with reasonable accuracy from steady flow tests. The in-cylinder flow characteristics were also insensitive to valve operation, but strongly depended on piston interaction, flow unsteadiness and residual effects from the previous cycle.

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Measurements of the three components of velocity and their corresponding fluctuations have been obtained by laser-Doppler anemometry mainly near TDC of compression in a model IC engine motored at 200 rpm with compression ratio of 6.7. The flow configurations comprised an axisymmetric cylinder head with and without upstream induced swirl and each of a flat piston and two centrally located, cylindrical and re-entrant, bowl-in-piston arrangements. In the absence of swirl and squish, the intake-generated mean motion and turbulence decayed considerably by the end of compression. The two piston-bowl configurations, however, resulted in a compression-induced squish motion with consequent formation of a toroidal vortex occupying the whole bowl space. Interacton of swirl, carried from intake and persisting through compression, with squish generated near TDC profoundly altered the axial flow structure. In the case of the cylindrical bowl, the sense of the vortex was reversed by swirl and, in the reentrant bowl, increased the number of vortices to two. The swirling motion inside the cylindrical bowl was close to solid body rotation while the re-entrant bowl gave rise to more complex flow patterns. Squish, in the presence or absence of swirl, did not augment the turbulent energy inside the cylindrical bowl contrary to the reentrant configuration where turbulence generation was observed.

Temperature and species concentration measurements have been obtained in a model combustor operating at an inlet temperature of 515 K and atmospheric pressure and are reported and discussed. The model comprises two rectangular sectors representing the primary and upper dilution zones of an annular combustor used in small gas-turbine engines. Natural gas (94 percent CH4) was used as fuel and was delivered through a T-vaporizer at rates that led to air-fuel ratios of 29 and 50, similar to those of take-off and ground-idle conditions, respectively. Temperatures were obtained at the exit of the combustor using fine-wire thermocouples and mean concentrations of major species were obtained in the primary zone and at the exit on a dry basis by gas sampling and analysis. The results show that the 200 K increase in inlet air temperature reduces the pattern factor from 0.55 to 0.3 and increases the combustion efficiency from 69 to 94 percent with the air-fuel ratio of 29. The higher air-fuel ratio improves the combustion efficiency to 97.6 percent but results in a worse pattern factor of 0.48. The results confirm the need for consideration of the rate-controlled CO → CO2 reaction in the dilution zone if CO emission is to be calculated correctly and temperatures are to be within 150 K. Examination of temperatures obtained from a local enthalpy balance shows that they are higher than measurements obtained with preheat, in contrast to a similar comparison without preheat.