Recently, attention has been paid to the visualization and image analyses of combustion fields. For a phenomenon as complicated as combustion, visualization is most effective as a first step in model construction and the most reliable means to avoid mistakes. Details such as (a) temperature and density, (b) mixing ratio, (c) concentrations of molecules and radicals, (d) reaction and heat-release rates, (e) velocity and turbulence, (f) parameters concerning two-phase flow, (g) parameters concerning soot and particulates, (h) parameters concerning thermal radiation, (i) states in engine combustion chambers and (j) derivatives such as correlations, gradients and vectors, were targetted as objectives of the imaging diagnostics of combustion. Each item was briefly explained and its state of art was reviewed.

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The characteristics of the air jets issuing from two kinds of exit shapes with an aspect ratio of 5 were measured at the first half of the experiment. Discrepancies between the orifice-type jet and the nozzle-type jet with a parallel part are clarified for two bilaterally symmetric planes of the jets. At the latter half of the experiment, submerged jets, colored by blue-black ink, are issued into a water tank and observed for exits of different exit shapes and aspect ratios. The observed flow types corresponded to the already known characteristics of the jet spread in the two bilatellary symmetric planes. In addition, it is interesting to find that the relative magnitude of the spread in the planes changed twice. This is also the case for both the nozzle- and orifice -type jets with a small exit velocity (a low Reynolds number).

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An air turbine with self-pitch-controlled blades in a reciprocating flow has been developed for wave power utility. In order to obtain the basic design data of this turbine, the experimental investigations have been performed by model tests of the rotor with fixed staggered blades under steady operating conditions. Twelve kinds of the rotors have been manufactured and tested to investigate the effects of the setting angle, solidity, thickness/chord ratio, and the aspect ratio on the turbine performance. The results have been shown that the turbine with self-pitch-controlled blades is superior to the Wells turbine both in the starting and running characteristics. A suitable choice of design factors has been suggested.

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The effects of seeding and mass separation in molecular beams of helium and argon binary mixtures are experimentally studied to quantitatively handle composition fraction deviations which inevitable occur during transport from the gas source chamber to the detecting instrument. The experiment is carried out over the source molar fractions χ₀=0∼100% and the source pressure p₀=25∼75 Torr under a constant room temperature. Heavier argon molecules are remarkably accelerated by the seeding effect due to lighter helium ones, especially at χ₀<1%, and the translational kinetic energy gain ratio reaches to the mass ratio of the binary molecules of 10. The Mach number of argon, however, slightly reduces. The mass separation effect is also prominent at χ₀<1%, and the total species enrichment factor attains also 10. The effect is essentially due to the Mach number focusing, which is observed by the difference in spatially spread behaviors between helium and argon molecules.

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This paper presents the results of an experimental study on the deflection and reattachment of a radial turbulent wall jet through two comparatively wide-spaced parallel disks, in the presence of a lateral control flow. The main content of this report concerns the effects of various opposite wall heights and control flow rates on the jet flow properties at and after the reattachment point on the wall surface. A flow field was divided into five regions. The changes of the maximum jet center velocity, the jet half-width and the turbulence intensities at the velocity maxima, and also the deflection of the jet center axis in each region, depended mainly on the combination of the opposite wall height and the control flow rate. Further, the limiting position in which the wall jet flow pattern might be maintained was examined.

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An analysis was performed on the laminar flow of the magnetic fluid between two parallel plates with a low-speed traveling magnetic field, using Shliomis' and Glazov's equations. The velocity profile, the mean velocity and the coefficient of friction were calculated for the flow with and without a pressure gradient, and compared with the authors' previous experimental results and analytical values in a steady magnetic field. The induced flow was in the same or opposite direction to the magnetic field depending on α₁ and the strength of the applied current. The increase in the coefficient of friction was appreciable in a low Reynolds number range and for relatively strong, high-frequency current.

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The surface tension of a magnetic fluid subjected to a magnetic field tangential to its surface was measured. The surface tension of a water-based magnetic fluid decreased with increases in the mass concentration on the constant strength of the external field. In contrast, the surface tension of the kerosine-based magnetic fluid increased. The surface tension of the magnetic fluid increased slightly with the strength of the magnetic field. The interfacial tension between nonmagnetic and magnetic fluids was measured. The interfacial tension also increased with the external field. Based on the measurements of the surface tension, the deformation of a drop of magnetized liquid in a magnetic field was investigated. The elongation of a magnetic drop was measured. The experimental results were compared with the theoretical value determined by the minima of energy.

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Unsteady liquid film flow on a rotating disk which is related to a spin coating technique to form a uniform thin film on a plate is calculated numerically. A newly developed calculation method which takes the surface tension on the liquid surface into account is applied. The numerical results reveal the following : the hemispherical liquid on the disk, which starts to rotate impulsively from rest, spreads by gravitational forces at the first stage. The development of the distribution of radial and azimuthal velocities is affected complicatedly by the Coriolis forces, viscous forces and centrifugal forces. The liquid spreads mainly by centrifugal forces and forms a uniform thin film on the disk at the last stage. The surface tension only show a little influence on the spreading process at the first stage.

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A method was developed for calculating unsteady aerodynamic forces acting on vibrating cascade blades in a three-dimensional flow field. Blades were allowed to have nonuniform span-wise steady loading, and to be vibrating in three-dimensional modes. The effects of wake deformation behind blade trailing edges were also considered. It was shown that nonuniform steady loading along the span controlled the unsteady aerodynamic characteristics of vibrating blades at lower reduced frequencies, and the effects of wake deformation became relatively significant at higher reduced frequencies. Compared to the results by a two-dimensional strip theory, there were considerable differences at lower reduced frequencies, especially in the case of highly loaded and staggered cascades. A high-order vibrating mode was also investigated in which an airfoil section might change its chord-wise shape significantly. The results indicated that this mode could be critical in determining the flutter boundary.

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This study investigates the developmental process of an axisymmetric (bubble type) vortex breakdown. In the the preceding reports, the growing process of the bubble was discussed, based on the inviscid linear theory of the internal wave. In this study, experiments on the unsteady swirling pipe flow are conducted to confirm the theoretical results concerning the growing process. The generation of a group of internal waves by the abrupt change of the upstream boundary condition, its propagation and dispersion are measured by a Laser-Doppler-Velocimeter, and the obtained data are compared with the results of the inviscid theory. The growing process of a bubble is clearly visualized by the method of intermittent injections of dye, and also examined by numerical analysis of the Navier-Stokes equations. The obtained results of the growing process showed a good agreement with the theory.

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Experimental investigations directed towards improving the range of operation of the Wells self-rectifying air turbine are reported. Several rotor configurations were tested. These include (1) rotor blades with their center line offset from a radial line, (2) rotor blades with leading edge slats, (3) rotor blades with trailing edge devices, (4) rotor blades with blunt trailing edges, (5) biplane rotors, (6) large thickness-to-chord ratio blades and (7) a turbine with a high level of inlet turbulence. Most of the configurations tested showed improvements in the operation range primarily by postponement of stall.

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Characteristics of in-cylinder gas flow in a two-cycle uniflow-type engine were investigated by using laser doppler velocimetry (LDV). Through swirl velocity measurements at several sections along the cylinder axis, it was found that in the early compression stroke, axial distribution of angular momentum is uneven and swirl velocity at each measuring section fluctuates periodically. Mean angular momentum in the whole of the combustion chamber, however, decays monotonously and analysis showed that its decaying process after a late compression stroke is similar to the swirl-decaying process in a cylindrical constant-volume bomb. A secondary airflow in the upper part of the combustion chamber is inferred from the measured radial and axial velocities in an early compression stroke.

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A modification of the values of three constants C₁, C₂ and C₃ in the standard K-ε turbulence model is proposed, based on the empirical law of decay obtained for nearly homogeneous in-cylinder turbulence. Since the decay exponent of Reynolds numbers for in-cylinder turbulence is found to be different from that for steady ducted flow just behind a turbulence-generating grid, the C₂ value is modified first, followed by the C₁ and C₃ values, which depend on the C₂ value. The derived C₂ value of 1.40 is smaller than that in the standard K-ε turbulence model, but the C₁ value, 1.40, is close to that of the standard one. The C₃ value, -1.05, is very close to the recommended value by Morel et al. for the case of a unidirectional axial compression.

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This paper describes the experimental results of the characteristics of the freezing heat transfer of layered air-water flow in a circular tube, in which cooled air and water co-flow. The experiments were carried out under a variety of conditions of water velocity, water temperature, tube wall temperature, and air temperature. Special attention was focused on photographic visual observations of the developing ice layer along the tube wall. Two different regions characterizing the ice formation were observed, one of which was the freeze-off region, and the other was the steady-state region. It was found that the criterion between the regions was described by the equation θ_c=1.92×10^-1Re_W^0.35. The onset of freeze-off was also accurately predicted by the equation F₀=7.43×10^-1Re_W^0.14Re_a^-0.03θ_c^-1.01.

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Forced convective boiling heat transfer data are obtained for R 12-R 22 mixtures and R 114-R 22 mixtures flowing in a horizontal tube. The test section is a stainless steel tube 8 mm ID and 4 m long, which is uniformly heated by direct current. Assuming a thermodynamic equilibrium state, the vapor quality and the saturated temperature of the mixture are calculated from the pressure data, the heat flux and the mass velocity. The local heat transfer coefficient normalized by the single-phase heat transfer coefficient, assuming that the liquid phase is flowing alone, is correlated to the function of the Lockhart and Martinelli parameter and the boiling number. Since the R 12-R 22 mixture has a small temperature difference between saturated liquid and saturated vapor at constant pressure (less than 3 degrees), the boiling heat transfer coefficient of binary mixtures lied between those of its component. For R 114-R 22 mixtures a significant reduction in the boiling heat transfer coefficient due to mass transfer effects is observed. This behavior is examined by means of a bubble growth model in a superheated binary liquid mixture.

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The coefficients of heat transfer on combustion chamber walls of internal combustion engines differ according to individual locations, but no actual experimental results have been reported. This study determined the coefficients of local heat transfer at each location on the wall surfaces of a combustion chamber. The coefficients were obtained by the instantaneous temperature, the instantaneous heat flux at each location measured by highly accurate thin-film thermocouples developed by the authors, and the instantaneous gas temperature in the combustion chamber determined by the gas pressure in the combustion chamber, which is the only source of information on gas in the chamber. As a result. It was found that the engine speed, gas flow, ignition timing, distance from the plug, shape of the combustion chamber, and temperature significantly affect the local heat transfer coefficient. It was also found that Eichelbeg's formula or Woschni's formula, in which the gas flow is taken into account, yield substantial differences from the measured values at high engine speeds.

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Initiation processes of gaseous detonation waves were observed experimentally in a tube. Gases to be tested were methane/oxygen mixtures of various initial compositions. The initiation was performed by blast waves caused by gaseous detonations of initiator gases which were stoichiometric oxyhydrogen mixtures at various initial pressures, the initiation energies of which were estimated by the method developed by the authors. The initiation energies were estimated from the experimental result of the decay of an inert planar blast wave produced by the initiator by utilizing the point source blast wave theory. The critical initiation energies were evaluated for the near limit composition of the mixture. In the initiation processed, local explosions were observed which played an important role under the critical condition, which was produced not only by the effect of the leading shock wave but also by that of the detonation products of the driver gas.

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Techniques of gas flow measurement in the field of combustion have greatly advanced since optical methods such as the laser Doppler velocimeter were introduced. Most of them, however, cannot map the velocity distribution over a plane of interest with a single observation. A fine wire which was set across a section of a combustion chamber was heated for a very short period of time during which a sheath of unbrunt gas attached to the wire was heated to give rise to schlieren to make it possible to trace the schlieren as well as that of the flame front until the heated gas was consumed by the flame. The electric circuitry and the characteristics of the system were investigated to evaluate the usefulness of this method. A 100 μm Ni-Cr wire was used to observer the transient flow around and in front of the jet in a divided combustion chamber. The flow in a cusp of the wedge shaped flame front in a simple rectangular chamber was observed as another example.

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To obtain a better understanding of the combustion process in a spark ignition engine with an unscavenged horizontal prechamber connected to a main chamber by a torch nozzle of various area sizes (An), the flame propagations in the pre- and main chambers are simultaneously visualized with high-speed photography under such operating conditions as the optimum spark advance for best torque (MBT), volumetric efficiency ηυ=80±2%, air-fuel ratio of A/F<bsime>15 and engine speed of N <bsime>1000 rpm. The torch flame patterns in the main chamber are found to correspond fairly well with those of heat release rates computed from the ensemble-averaged pressure diagrams. On the basis of those flame photographs, several combustion characteristics, namely, the apparent flame speed, timing of actual ignition, ejected timing of torch flame and timing of combustion finish and combustion area fraction are also examined for each torch nozzle with different areas and an open chamber. In addition, the correlations between the above combustion characteristics and the engine performances are discussed.

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An experimental study was performed of the fundamental aspect of the mixture formation in the combustion chamber of an automotive spark ignition engine with multipoint fuel injection. The mixture formation during the intake stroke of an engine was simulated by the timed or continuous injection of Freon-113 or Freon-12 into the steady flow of dust-free dry air through an intake port. The vapor concentration in the transparent combustion cylinder was determined with the application of the laser Rayleigh scattering. The results showed that the present optical system was useful for the time- and space-resolved measurements of vapor concentration in the combustion chamber in the case of liquid and gaseous fuel injections. The spatial distributions of the time-averaged vapor concentration were highly heterogeneous. It was also found that the vapor concentration profile was largely affected by the place for fuel injection and the intake valve lift.

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