Showing papers in "Jsme International Journal Series B-fluids and Thermal Engineering in 1976"
TL;DR: In this article, the Sauter mean diameter of diesel spray droplets was measured using liquid immersion sampling technique with the mixtute of water-methylcellulose solution and ethanol used as an immersion liquid for diesel fuel oil.
Abstract: In order to determine spray droplet size in diesel engine, fuel was injected into high pressure gaseous environments with a diesel engine injection system. Droplet size was measured using the liquid immersion sampling technique with the mixtute of water-methylcellulose solution and ethanol used as an immersion liquid for diesel fuel oil. The volume distribution of diesel spray droplet is well correlated with chi-square distribution with freedom, φ=8 in the range of this investigation. The Sauter mean diameter increased with increasing back pressure, with the amount of fuel in a spray and with decreasing pump speed. An empirical correlation was developed between effective injection pressure, air density, the quantity of the fuel delivery and the Sauter mean diameter of spray droplets.
106 citations
TL;DR: In this article, an experimental and theoretical study on the ignition delay of a single paraffin hydrocarbon droplet in high pressure gaseous environments were carried out. But the experimental results were correlated with the following expression.
Abstract: Experimental and theoretical studies on the ignition delay of a single droplet in high pressure gaseous environments were carried out. In the experiments, a movable furnace was dropped over a droplet to cause the ignition and the measurement of ignition delay was made for normal paraffin hydrocarbon droplets at 0 atg40 atg of ambient gas pressure and 220°C700°C of ambient gas temperature. Experimental data were correlated with the following expression. [numerical formula] where P, T, and φd are pressure, and temperature and oxygen concentration of ambient gas of which increase makes the ignition delay short. Ignition delay was independent of droplet size and increased with an increase in the number of carbon atom in a molecule of fuel. In the theory, a model was developed for droplet ignition, which consisted of the evaporation of a droplet and ignition of homogeneous gas mixture, and ignition delay was calculated. Both the experimental and the theoretical results showed reasonable agreements.
97 citations
68 citations
TL;DR: In this paper, the authors investigated the properties of two different types of interference regions of a round jet of water impinging vertically on a horizontal plane forming a thin film flowing radially which later turns into an ordinary flow after passing through a hydraulic jump region.
Abstract: A round jet of water impinging vertically on a horizontal plane forms a thin film flowing radially which later turns into an ordinary flow after passing through a hydraulic jump region. Hydrodynamic and heat transfer characteristics of two domains of the flow are investigated experimentally. The one domain is the jump region and the other is the interfering films of two equal jets. These two domains have several properties similar to each other because they are both interference zones of two flow regions. The radial location of the interference is found to be an important factor in the hydraulic and thermal properties of the interference region. The film of the jet flow is measured and analysed. It is found that different behavior of the interference zone are characterized by the film Froude number and the Reynolds number taking the radius from the center of the jet as the representative length.
65 citations
TL;DR: In this article, the behavior of nucleate and transition boiling within a space gap made by holding a ll-mm dia. glass disc in coaxial position above a heated llmm Dia. horizontal, upwardfacing copper disc has been studied experimentally for saturated water at atmospheric pressure.
Abstract: Nucleate and transition boiling within a space gap made by holding a ll-mm dia. glass disc in coaxial position above a heated ll-mm dia. horizontal, upward-facing copper disc has been studied experimentally for saturated water at atmospheric pressure. The distance between the glass disc and the heated surface s is changed within a range from s=∞ to s=0.1 mm, and high-speed photography is employed to record the behavior of liquid and vapor within the narrow space. It is clarified in the present study that, following the change of s, characteristic variations appear in the state of boiling, in the form of supply of liquid to the heated surface, and in the occurrence of burnout, respectively.
50 citations
TL;DR: In this paper, the instability of two pairs of infinitely long parallel vortex sheets for initial disturbances is investigated by a linear analysis in an inviscid incompressible fluid, and it is shown paradoxically that two pairs can not exist at a gap distance between two pairs less than the distance between vortex sheets of each pair.
Abstract: The instability of two pairs of infinitely long parallel vortex sheets for initial disturbances is investigated by a linear analysis in an inviscid incompressible fluid, and it is shown paradoxically that two pairs of parallel vortex sheets can not exist at a gap distance between two pairs less than the distance between vortex sheets of each pair. By calculating the non-linear growth in time of periodic disturbances in the vortex sheets, the essential features of the formation and interaction of two parallel vortex streets are analysed, and it is explained that the initially antisymmetric disturbance is more apt to cause the interaction between two vortex streets in their developing stage than the symmetric one. These theoretical results are compared with the experimental ones which were observed in a flow past two circular cylinders spaced in the direction perpendicular to a uniform flow.
45 citations
41 citations
TL;DR: In this article, the fundamental equations for pulsating turbulent flow in a circular tube containing a slightly compressible fluid are derived by describing Reynolds stress in terms of eddy viscosity, for whose distribution five models are introduced.
Abstract: Fundamental equations for pulsating turbulent flow in a circular tube containing a slightly compressible fluid are derived by describing Reynolds stress in terms of eddy viscosity, for whose distribution five models are introduced. Analytical solutions based on each model are developed for steady flow velocity, oscillating velocity and wave propagation constant. Comparison of these solutions for each model shows that the four-region model proposed by Karman is rather reasonable enough to illustrate the flow behaviours. The distributions of oscillating velocities, wave propagation constant, and oscillating pressures based on the four-region model at low frequencies and small Reynolds numbers are similar to those at high frequencies and small Reynolds numbers are similar to those at high frequencies and large Reynolds numbers. Because of the assumption of time-invariant eddy viscosity profile, the low frequency values of wave propagation constant should not be reliable. The analogy of these turbulent flow solutions with the laminar ones is shown schematically.
34 citations
TL;DR: In this paper, the main geometrical parameters of housing, which determine the fan performance are the tip clearance of tongue, the setting angle of its suction side and the size of casing.
Abstract: Cross flow fan has various kinds of performance curves according to housing geometry, but quantitative relations between them have not been made clear. In this paper, experiments are carried out systematically with the housings of simplified form at first. However, the following results are valid even for housings of a more generalized form. It is found that the main geometrical parameters of housing, which determine the fan performance are the tip clearance of tongue, the setting angle of its suction side and the size of casing. the delivery angle of impeller and the height of fan outlet have only a secondary effect compared with these main parameters. The tip clearance is important for the stability of performance curve, and the setting angle has a certain optimum value. Various types of performance curves are obtained by changing the size of casing.
26 citations
TL;DR: Dimensionless approximate solutions for slightly compressible fluid flow are derived from the exact solutions of the fundamental linear equations for unsteady viscous compressible flow, and shown to be reasonable within the region w'≤3c' and c'≥3375×104 (w' =R2w/v, c'=Rc/v ; w, angular frequency ; c, speed of sound ; R, pipe radius ; v, kinematic viscosity).
Abstract: Dimensionless approximate solution for slightly compressible fluid flow are derived from the exact solutions of the fundamental linear equations for unsteady viscous compressible flow, and shown to be reasonable within the region w'≤3c' and c'≥3375×104(w'=R2w/v, c'=Rc/v ; w, angular frequency ; c, speed of sound ; R, pipe radius ; v, kinematic viscosity) In this region radial velocity and cross-sectional variation of pressure are shown to be negligibly small Pressure and velocity of air and water flow pulsating through a vertical pipe by means of a piston are measured by the use of a strain-gauge-type pressure transducer and a hot-wire anemometer, respectively Comparisons of experimental results with approximate solutions show that cross-sectional distribution of oscillating velocities agree closely with the theoretical value within the frequency range 002 l f l 12 Hz, independently of Reynolds number, piston amplitude, pipe radius, and fluid, and that oscillating pressure distribution within the pipe and oscillating velocity distribution along the pipe axis also agree well with the theoretical values
24 citations
TL;DR: In this article, the flexural vibration s of a circular plate under various mixed boundary conditions is investigated. But the results of the experiments are limited to three examples: one is of a plate clamped on part of its boundary and simply supported on the remainder, another, partly simply supported and partly free, and a third, partly clamped and partially free.
Abstract: This paper deals with the flexural vibration s of a circular plate under various mixed boundary conditions. The mixed constraint conditions for the displacements of the plate on its circumference are formulated by means of the weighted residual method, and the corresponding dynamical boundary conditions are derived from the Lagrangian by the multiplier method in the calculus of variations. Numerical calculations are carried out for three examples ; one is of a circular plate clamped on part of its boundary and simply supported on the remainder, another, partly simply supported and partly free, and a third, partly clamped and partly free. an experiment is made on the last example, and the experimental values almost agree with the calculated values.
TL;DR: In this paper, a technique to obtain an optimum strength shape is proposed by applying an automated design system, where at the first step a fundamental shape, which satisfies the design conditions, is made ; at the second step the superiority or inferiority of the shape is judged according to the stress distributions obtained by using the F.E.M. ; and more the shape was corrected at the final step.
Abstract: In this paper, a technique to obtain an optimum strength shape is proposed by applying an automated design system. The main process of this technique is that at the first step a fundamental shape, which satisfies the design conditions, is made ; at the second step the superiority or inferiority of the shape is judged according to the stress distributions obtained by using the F.E.M. ; and more the shape is corrected at the final step. Particularly, at the final step the correction of shape is made by the method of changing the finite elements used by the F.E.M. into the optimum shapes. If these steps are repeated, the optimum shape will be obtained. Next, the above mentioned technique is applied to determine an optimum strength shape of a dam under water pressure.
TL;DR: In this paper, the authors investigated the relationship between the shape of performance curve and flow pattern of cross flow fan and found that when φ > 0.3, both the angle of delivery arc and the size of casing affect the pattern as well as fan performance.
Abstract: Relations between the shape of performance curve and flow pattern of cross flow fan are investigated. Total pressure distributions along inner periphery of impeller are measured by traversing a three-hole circular yaw probe. Output signals from a hot-wire probe fitted to impeller are photographed to show the relative flow through blades. Movements of the eccentric vortex inside impeller are measured by these methods, and the following results are obtained. When the flow rate decreases, the vortex center moves along the inner periphery of impeller towards the tongue over the flow rate corresponding to the maximum of ψt. Substantially different two types of flow patterns appear according as φ is larger than 0.3 or not. That is, when φ>0.3, the shape of tongue is the determining factor to the flow pattern, if casing of ordinary size are used. However, when φ<0.3, both the angle of delivery arc of impeller and the size of casing affect the pattern as well as fan performance.
TL;DR: In this article, a straight horizontal pipe conveying a two-phase fluid is derived by accounting for 1) inertia force, 2) the pipe's elastic restoring force, 3) Coriolis' force, 4) centrifugal force, 5) pressure fluctuations, 6) momentum change due to time-varying density of the two phase flow and 7) gravity as an external force.
Abstract: This paper deals with experimental and theoretical analyses of the excitation mechanism of vibrations induced by an air-and-water two-phase flow in a straight horizontal pipe. The experiment reveals a strong relationship between the first natural frequency of a piping system and the dominant frequency of void-signals -- that is, the frequency ratio being 1/2, 1/1, 3/2, -- when extraordinarily strong vibrations are observed. The equation of motion in a straight horizontal pipe conveying a two-phase fluid is derived by accounting for 1) inertia force, 2) the pipe's elastic restoring force, 3) Coriolis' force, 4) centrifugal force, 5) pressure fluctuations, 6) momentum change due to time-varying density of the two-phase flow and 7) gravity as an external force. The equation is transformed into a Mathieu's with a periodic external term ; instability analysis concludes that parametric excitation and resonance are the main causes of such strong vibrations. Good agreement can be seen between experimental and theoretical results.
TL;DR: In this paper, the effect of the random components of the error on dynamic loads is analyzed theoretically and one example of numerical result is shown, where the Fokker-Planck equation is derived.
Abstract: Analysis of transmission error curve of a pair of gears measured by a single flank meshing tester shows that the error can be separated into harmonic components and random ones. In this paper the effect of the random components of the error on dynamic loads is analysed theoretically and one example of numerical result is shown. Dynamic behavior of gear systems is considered as nonlinear, nonstationary random process because of variable spring constant, backlash term and random component of error, so the Fokker-Planck equation is derived. It is analysed approximately using statistical linearization and the mean and the variance of dynamic loads are calculated numerically. Monte-Carlo-Simulation is also performed to find dynamic loads by means of an analogue computer. The results show that the mean of the dynamic loads remains at similar level as in deterministic process where the random components of error are not considered for any gear speed, but the variance of them increases rapidly with an increase in speed over resonance frequency.
TL;DR: In this paper, a solution for the stress distribution in an infinite elastic solid with three spherical cavities is presented, based on the Papcovich-Neuber stress function approach and deduced with use of the spherical harmonics.
Abstract: This paper contains a solution in series form for the stress distribution in an infinite elastic solid which posseses three spherical cavities. The loading consists of a uniform field of uniaxial tension at infinity in the direction perpendicular to the common axis of the cavities. The solution is based upon the Papcovich-Neuber stress function approach and deduced with use of the spherical harmonics. The method can be developed for a variety of cavity numbers and sizes. Numerical evaluations are given for the stress distributions in the infinite medium containing (i) three equidiameter spherical cavities or (ii) two outer cavities of the same size and the central cavity of any size. The results illustrate the interference of three sources of stress concentration in a three-dimensional problem.
TL;DR: In this article, a modified Reynolds equation is derived to obtain the pressure distribution and the load capacity of journal bearings, and the effects on the bearing performance are discussed, by introducing a "ratio of nonlinearity" and a "rate of non-linear influence".
Abstract: It is found experimentally that the lubricating oils, with high molecular weight polymers, indicate the composite flow characteristics involving pseudo-plastic and dilatant behavior. Applying a polynomial expression for such non-Newtonian characteristics, a modified Reynolds equation is derived, to obtain the pressure distribution and the load capacity of journal bearings. Comparing with experiments, the physical meanings of the composite flow characteristics are made clear. The effects on the bearing performance are discussed, by introducing a "ratio of nonlinearity" and a "rate of nonlinear influence".
TL;DR: In this paper, the authors measured the pressure and velocity of pulsating turbulent air and water flows in circular pipes generated by rotary valves using a strain-gauge-type pressure transducer and a hot-wire anemometer.
Abstract: Pressure and velocity of pulsating turbulent air and water flows in circular pipes generated by rotary valves were measured by the use of a strain-gauge-type pressure transducer and a hot-wire anemometer, respectively (0.0432 <= f <= 48.0 Hz, 7740 <= Re <= 95900). Comparisons of experimental data with approximate solutions derived from a four-region model for a pulsating turbulent flow in a circular pipe containing a slightly compressible fluid show that : (i) Cross-sectional distribution of time-averaged velocities agrees well with that of steady flow velocities. (ii) Cross-sectional distribution profiles of oscillating velocity coincide well with the above-mentioned theoretical ones, and therefore, depend only on the Reynolds number and the dimensionless angular frequency w'=R2w/v, where R is pipe radius, w angular frequency, v kinematic viscosity. (iii) Axial distributions of oscillating pressures and velocities on the pipe axis also agree well with the above-mentioned theoretical ones within the frequency range of 0.1 <= f <=48.0 Hz.
TL;DR: In this paper, the free flexural vibration characteristics of an elliptical plate with the edge restrained in a manner that prevents transverse edge motion and provides a restoring edge moment proportional to rotational angle of edge.
Abstract: It is the object of this paper to make clear the free flexural vibration characteristics of an elliptical plate with the edge restrained in a manner that prevents transverse edge motion and provides a restoring edge moment proportional to rotational angle of edge. Based on the ordinary thin plate theory, the procedure leading to a frequency equation is given in the case of the normal mode of symmetrical vibration about both axes. The numerical calculations are carried out and the lowest nondimensional frequencies are tabulated for he aspect ratios of the ellipse and the rotational spring stiffnesses of edge restraint in the cases of Poisson's damental ellipse tends to a circle, the frequency equation degenerates to the form for a circular plate.
TL;DR: In this article, a systematic analysis of static and dynamic characteristics of plate heat exchangers having a number of heat transfer plates is presented, and the results are numerically compared under the condition that each flow rate of the hot and cold-side fluids remains constant in any flow type.
Abstract: This paper presents a systematic analysis of static and dynamic characteristics of plate heat exchangers having a number of heat transfer plates. There are various flow types in a plate heat exchanger system. The results are numerically compared under the condition that each flow rate of the hot- and cold-side fluids remains constant, respectively in any flow type. The significant results are : 1) In almost every flow type, the temperature effectiveness increases as the number of passages increases. 2) Dynamic responses may greatly depend on the relation between the inlet and outlet passages where each fluid flows in a counter- or a parallel current. 3) Series flow types where the inlet and outlet passage are adjacent and the flow is a countercurrent have the best statics and dynamics among all types when the number of passages is the same.
TL;DR: The performance of pumps with semi-open impellers was tested under air admitting conditions and the effects of running clearance between the impeller vanes and the stationary casing were discussed and the results were compared with those of closed-impeller pumps.
Abstract: The performance of pumps with semi-open impellers was tested under air admitting conditions and the effects of running clearance between the impeller vanes and the stationary casing were discussed. The results were compared with those of closed-impeller pumps. when the clearance reduces, the pump ability under no air admission increases continuously, but the performance is much decreased by air admission. When the clearance relative to the channel depth of impellers λ is increased beyond 0.1, the drop of pump head due to air admission is much weakened, and it tends to a definite value, regardless of impeller shape. When two pumps with a closed-impeller and with a semi-open impeller show the same performance under no air admission, both pumps develop nearly the same performance under air admitting condition. The clearance range of λ=0.033∼0.086 is suitable for the duty of delivering air-water mixture.
TL;DR: In this paper, the authors presented some experimental and analytical studies on a new repulsive type dynamic vibration absorber consisting of three permanent magnets of thick disk type(1)∼(2).
Abstract: This paper presents some experimental and analytical studies on a new repulsive type dynamic vibration absorber consisting of three permanent magnets of thick disk type(1)∼(2). These magnets are so arranged in a non-magnetic conductive or non-conductive cylinder that one magnet can move freely between the two fixed ones. The result showed that: (1) Repulsive force(3) interacting between the two magnets may be assumed to be inversely proportional to the nth power of the center distance between the magnets. This assumption makes the analysis easier, and the results of the experiment show considerable coincidence with those of the analysis. (2) The new absorber may be able to control the resonant amplitude of the vibrating body which weighs several dozen times the free magnet. Further merits of the absorber are an eddy current damping generated in the conductive cylinder and arbitrary choice of the vibration direction as well as the frequency adjustability.
TL;DR: In this article, an active vibration absorber controlling the pressure of the air spring is applied to a preview control system of a vehicle suspension, where the front half part of the vehicle functions as the sensor for the vibration absorption of the rear half part.
Abstract: In this paper, the active vibration absorber controlling the pressure of the air spring is applied to a preview control system of a vehicle suspension. The front half-part of the vehicle functions as the sensor for the vibration absorption of the rear half-part. The design criterion for the optimum preview control absorber is the minimization of the rms value of the acceleration under the specified constraints on the relative displacement. The optimum preview system is realized by the feedforward and feedback compensation systems. Chang's optimum control theory is applied to the optimization. The experimental results show good coincidence with the analyses.
TL;DR: In this paper, a tentative method for calculating the optimum case depth for surface durability of roller pairs which had various relative radii of curvature was introduced, and this calculation method was successfully discussed with the practical case-hardened gears.
Abstract: In order to clarify the surface durability of the surface hardened steels and the optimum design condition of the surface hardened gears, the carburized and hardened steel rollers were tested with a rolling contact fatigue testing machine. Consequently, it was made clear that there is an optimum case depth for the surface durability and that the crack initiation depth of spalling coincides quite well with the depth where the amplitude of the ratio of orthogonal shear stress to Vickers hardness becomes maximum. By using these test results, the authors introduced a tentative method for calculating the optimum case depth for surface durability of roller pairs which had various relative radii of curvature. And this calculation method was successfully discussed with the practical case-hardened gears.
TL;DR: In this paper, a continuous data acquisition system utilizing the analog computing circuits was developed and its accuracy was verified satisfactorily in order to study the cycle-by-cycle variations of combustion in a diesel engine.
Abstract: In order to study the cycle-by-cycle variations of combustion in a diesel engine, a continuous data acquisition system utilizing the analog computing circuits was developed and its accuracy was verified satisfactorily. Preliminary experiment proved that the amount of injected fuel per cycle could be measured indirectly by the integrated value of the injection nozzle lift. Then, applying the whole system to a two-stroke diesel engine, the necessary data including the indicated mean effective pressure etc. were collected and analyzed statistically. The result indicates that the irregularity of amount of injected fuel per cycle, which is subjected to the varying characteristics of the injection system concerned, mainly governs the variation of the indicated mean effective pressure.
TL;DR: In this paper, the relationship between the number of heat transfer units and the temperature efficiency e is analyzed analytically or numerically, assuming that K = 1+mxn or K = mθn in the non-dimensional form referred to the standard value K0.
Abstract: In case where the overall heat transfer coefficient K varies with positions on the heat exchanger surface or fluid temperature in the cross-flow exchanger, the relations between the number of heat transfer units and the temperature efficiency e are obtained analytically or numerically, assuming that K = 1+mxn or K = 1+mθn in the nondimensional form referred to the standard value K0. The effects of parameters m and n are shown quantitatively, arranging the calculated results by the ratio of the efficiency change (e-e0)/e0, where e0 is the temperature efficiency for K = K0 and by the single overall coefficient signifying "true mean overall coefficient". Further, it is shown that there is considerable difference among flow arrangements and that conventional methods are not sufficient for large value of m.
TL;DR: In this paper, the effects of the shape of the tongue and the lap of the suction cone and mouth ring on the performance and noise level of a high specific speed airfoil fan are investigated.
Abstract: The performance and noise level of the high specific speed airfoil fan are affected by the structural factors of its casing. Of such factors the following two are thought to produce particularly pronounced effects : (1) clearance and shape of the tongue; and (2) clearance and lap of the suction cone and mouth ring. The work presented here is a study to determine the effects of such structural factors. For experimental purposes two types of tongues were developed: a skew type slanting in the direction parallel to the vane outlet width; and a modified type having a clearance changed in the same direction as above. A series of experiments was performed in single suction type airfoil fans in which these parameters were incorporated. As a result, their effects on the performance, noise level and noise spectrum of the fan were clarified, thus enabling us to obtain useful information for fan design optimization.
TL;DR: In this paper, an experimental investigation of the wake flow behind a two-dimensional wedge was performed in the wind tunnel at the Reynolds number Re = 9.0×103, where the velocity distribution and the width of wake in the similar profile region were compared with the theoretical results obtained by Schlichting and Reichardt, and discussed in comparison with the results for a circular cylinder.
Abstract: The present work is concerned with an experimental investigation of the wake flow behind a two-dimensional wedge. The experiment was performed in the wind tunnel at the Reynolds number Re = 9.0×103. The pressure distribution on the wedge surface, the vortex-shedding frequency behind the wedge and the distributions of velocities and static pressures in the wake flow were measured. From the surface pressure the drag of wedge was obtained. The velocity distribution and the width of the wake in the similar profile region were compared with the theoretical results obtained by Schlichting and Reichardt, and discussed in comparison with the results for a circular cylinder.
TL;DR: In this article, experimental investigations were made on the blowing characteristics of a single hole on a circular cylinder in cross flow and on film cooling with injection from rows of holes located near the leading edge of a flat plate model with a blunt nose, and the change in the flow pattern of the injected flow around the model by visualizing technique.
Abstract: For the application to film cooling of turbine blades, experimental investigations are made on the blowing characteristics of a single hole on a circular cylinder in cross flow, and on film cooling with injection from rows of holes located near the leading edge of a flat plate model with a blunt nose, and on the change in the flow pattern of the injected flow around the model by visualizing technique. It is concluded that the flow rate coefficient of an ejection hole varies under the influence of the main flow, and that the film cooling effectiveness downstream of rows of blowing holes is sometimes lowered by excessive injection, and that the inclination of ejection holes in the spanwise direction shows very high cooling effectiveness.