Piston Head Research Articles

Double adjustable shock absorbers utilising electrorheological and magnetorheological fluids

Double adjustable shock absorbers allow for independent adjustment of the yield force and post-yield damping in the force versus velocity response. To emulate the performance of a conventional double adjustable shock absorber, an electrorheological (ER) and magnetorheological (MR) automotive shock absorber were designed and fabricated at the University of Maryland. For the ER shock absorber, an applied electric field between two tubular electrodes, located in the piston head, increases the force required for a given piston rod velocity. For the MR shock absorber, an applied magnetic field between the core and flux return increases the force required for a given piston rod velocity. For each shock absorber, two different shaped gaps meet the controllable performance requirements of a double adjustable shock absorber. A uniform gap allows for control of the yield force of the shock absorber, while a nonuniform gap allows for control of the post-yield damping. Force measurements from sinusoidal displacement cycles, recorded on a mechanical damper dynamometer, validate the performance of uniform and non-uniform gaps for adjustment of the yield force and post-yield damping, respectively.

316 小型 2 サイクルエンジンピストンクラウン部の燃焼堆積物分布と温度の関係 : ガソリンとメタノールの比較

316 小型 2 サイクルエンジンピストンクラウン部の燃焼堆積物分布と温度の関係 : ガソリンとメタノールの比較

Effects of the oil and liquid fuel film on hydrocarbon emissions in spark ignition engines

A model was developed to assess the absorption and desorption of fuel in oil film and in the binary diffusion of oil and fuel films. This was investigated with a parametric study according to engine speed, load and oil film temperature. The results show that Henry's constant, which is related to solubility, is the most dominant parameter in the absorption/desorption mechanism of fuel into the oil film. Under warm-up conditions, engine speed had little influence on the amount of fuel absorbed/desorbed, but when the oil film temperature was low, the quantity of fuel absorbed/desorbed decreased with increasing engine speed. Liquid fuel on the oil film and piston head caused higher hydrocarbon (HC) emissions, and under base conditions (a simulated cold engine), the amount of fuel vaporized from fuel film and desorbed from wetted oil film was 24.5 per cent of the stoichiometric fuel mass. The effect of oil film with liquid fuel was 5.3 times larger than that of oil film without liquid fuel. The amount of fuel that escaped from the piston crevice was 1.3 times larger than that of fuel in the oil film. However, the fuel trapped in the oil film desorbed into the combustion chamber more slowly than the fuel that escaped from the piston crevices under cold engine conditions.

Efficient design of the diaphragm: distribution of blood flow relative to mechanical advantage.

The mammalian diaphragm is composed of two separate muscles (costal and crural) connected by a central tendon that serves as a piston head for drawing air into the lungs. The two muscles are described as having different embryological origins, segmental innervations, and mechanical functions [De Troyer A, Sampson M, Sigrist S, and Macklem PT. Science 213: 237-238, 1981; De Troyer A, Sampson M, Sigrist S, and Macklem PT. J Appl Physiol 53: 30-39, 1982]. On the basis of regional blood flow measurements, the two muscles appear to be nonuniformly recruited at rest, but we anticipated that the two muscles would become uniformly recruited at heavy exercise to efficiently support the high energy requirements of ventilation. We used fluorescent microspheres to measure regional blood flow within the two muscles as an index of muscle recruitment from rest to heavy treadmill exercise in well-trained foxhounds. However, the heterogeneity of blood flow at rest persisted as exercise workloads were increased. Blood flow per gram of muscle remained twofold greater in ventral than dorsal regions of both muscles from rest to heavy exercise. This pattern was matched by a twofold greater regional mechanical advantage in ventral than dorsal regions of the two muscles measured anatomically. Hence blood flow was preferentially and efficiently distributed to those regions capable of generating the greatest inspiratory power independent of muscle mass. The two muscles were recruited from rest to heavy exercise as a single functional unit, not as two muscles under separate control.

Three-dimensional smoothed particle hydrodynamics simulation of high pressure die casting of light metal components

In this paper we present the extension of smoothed particle hydrodynamics (SPH) modelling of high pressure die casting (HPDC) to both three-dimensions (3D) and to realistic die geometries. The SPH method is well established in other areas and is now used for HPDC. The SPH method (in 3D) and the methodology used to represent complex three-dimensional die shapes are described. The use of this SPH system to model the filling of a representative generic HPDC component is presented. The importance of the order of the die filling, first seen in two dimensions, is demonstrated as is the role of flow separation from corners and even moderately curved surfaces. The degree of surface fragmentation, droplet formation and the strongly transient nature of the voidage are also shown. Finally the filling of the runner, gate and die for a real automotive piston head from an automatic transmission is shown and the difficulties inherent in such large scale computations are discussed.

A numerical study of the effects of piston head configurations on stratified mixture formation in gasoline direct-injection engines

In this paper, the characteristics of flow and spray motions affected by from piston head configurations were investigated numerically. Calculations were carried out from intake process to the end of compression. GTT (Generalized Tank and Tube method) code, which includes a third order upwind Chakravarthy-Osher TVD scheme andk-e turbulence model with fuel spray analysis was used for the calculations. As a results, piston heads with smaller radii of curvature were found to give stronger reverse tumble than those with larger radii of curvature. Similar results are shown in the convection and diffusion of fuel sprays.

A study on effects of recirculated exhaust gas upon wear of cylinder liner and piston in diesel engines

The effects of recirculated exhaust gas on the wear of cylinder liner and piston were experimentally investigated by a two-cylinder, four cycle, indirect injection diesel engine operating at 75% load and 1600 rpm. For the purpose of comparison between the wear rates of the two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot in exhaust emissions was removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors (A water injector has 144 nozzles of mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out with the fuel injection timing fixed at 15.3° BTDC. It was found that the mean wear rate of cylinder liner with EGR was greater in the measurement positions of the second half than those of the first half, that the mean wear rate without EGR was almost uniform regardless of measurement positions, and that the wear rate of piston skirt with EGR increased a little bit, but the piston head diameter increased, rather than decreased, owing to soot adhesion and erosion wear, and especially larger with EGR.

An experimental study on the optimization of powder forging process parameters for an aluminum-alloy piston

The purpose of this paper is to optimize the powder forging process parameters for an aluminum-alloy piston, namely the composition, mixing time, sintering time, sintering temperature, shape of the preform, etc., through experiments and to develop a high strength aluminum-alloy piston with an optimized process. At the first step, the composition of the material was determined and optimal sintering conditions for the material were examined. Proper mass percentages of Al, Cu, Si, Ni, Mn, Mg powders were added to Alumix 123 (Al–4.5Cu–0.5Mg–0.7Si), manufactured by Eckart (Germany). The number of experimental parameters were totally 27, i.e., Si contents of 1, 1.5, 2.0% (mass), sintering temperatures of 560, 580 and 600°C, and sintering times of 20, 25 and 30 min. From the experiments, a Si content of 1.5% (mass), a sintering temperature of 580°C, and a sintering time of 25 min were determined as the optimal process conditions. At the second step, the shape of preform for a cup-shaped product was determined considering the workability of the material and the effect of density increase in the forging process. Performed for this purpose was the upsetting test for the workability of the sintered specimens. The effect of density increase and strain loci were studied. A preform with a proper wall height was determined as the most effective shape. Finally, an aluminum-alloy piston for a vehicle engine was formed using the process parameters determined previously. After T6 heat-treatment of the formed piston, the hardness and tensile strength of the piston head were examined. The results showed, that compared with the hardness and tensile strength of the forged piston, those of the formed piston increased to 76.4 HRB and 500 MPa.

205 筒内直接噴射式ガソリン噴霧における壁面衝突挙動の解析的研究(GS-6・7 エンジンシステム(1))

In the case of direct injection gasoline engines, the injected fuel spray impinges on a piston head for stratification combustion, consequently, the spray-wall interaction process leads to the generation of unburned hydrocarbons and combustion chamber deposit. Therefore, it is very important to analyze the fuel behavior during the spray-wall interaction. As the first step, small non-dispersed droplet impinges on a hot wall that simplify fuel spray impinge on a hot wall. The film formation process and breakup-dispersion process was observed by means of high-speed video camera. As the second step, for impinging spray, the behavior of droplet images was taken by laser sheet scattering. As a result, the breakup pattern of the impinged droplet is classified into 7 types. The film formation and breakup-dispersion process is predicted by impingement angle, Weber number and surface superheat degree. Spray-wall interaction process of injected fuel spray is affected by surface superheat degree.

FORMATION OF COATINGS BY ANODIC MICROARC OXIDATION AND THEIR OPERATION IN THERMALLY-STRESSED ASSEMBLIES

The effect of the range of electrophysical conditions on the course of anodic microarc oxidation is studied. Process parameters are optimized and a number of production procedures are developed for providing the preparation of efficient ceramic coatings that are effective heat protection for thermally stressed assemblies of internal combustion engines. Coating thickness may reach up to 200 (m that was previously considered impossible. The results form the basis of a production method for the ceramic heat-resistant coating by anodic microarc oxidation for the piston head of a high-power internal combustion engine.

Fatigue Strength Characteristic of Metal Matrix Composite Material in $9Al_2\;.\;2B_2O_4$ / AC4CH

Metal matrix composites with whisker reinforcements have significant potentials for demanding mechanical applications including defense, aerospace, and automotive industries. Especially metal matrix composites, which are reinforced with aluminum borate whisker, have been used leer the part of piston head in automobile because of good specific strength and wear resistance. In this study, AC4CH-based metal matrix composites with B reinforcement have been produced using squeeze casting method, after T6 heat treatment, we evaluated fatigue life property of matrix and MMC composite and investigated fracture mechanism.m.

Thermomechanical fatigue characterization of zirconia (8%Y2O3-ZrO2) and mullite thermal barrier coatings on diesel engine components: Effect of coatings on engine performance

8%Y2O3-stabilized zirconia (8YPSZ) and mullite (3Al2O3·2SiO2) powders, which were made plasma sprayable by using an organic binder (polyvinyl alcohol), have been plasma spray coated on to the piston head, valves and cylinder head of a 3.8kW single-cylinder diesel engine, previously coated with Ni-Cr-Al-Y bond coat. The engine with components coated with 250 μm thick 8YPSZ and 1 mm thick mullite thermal barrier coatings has been evaluated for fuel efficiency and for endurance during 500 h long rigorous tests. Improved fuel efficiency was shown by the engine with coated components and the results are discussed. The coatings and the coated components have also been examined for phases, microstructure and chemical composition by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Mullite coatings were found to exhibit increased resistance to microcracking compared with 8YPSZ during the 500 h endurance test.

A NOVEL TISSUE ATTACHMENT SCHEME FOR BIOMECHANICAL PROSTHESES

Hamessing in situ muscle power for circulatory support requires a reliable means to anchor a biomechanical actuator to both muscle and bone. The objective of this study was to determine the long-term stability of a tissue attachment scheme designed to secure a piston-based hydraulic actuator to the latissimus dorsi (LD) and underlying ribcage. Woven stainless-steel mesh was used as a porous backing plate for fixing the device to the chest wall (using heavy suture tied through the mesh and around the ribs). LD attachment was made by wrapping the humeral tendon in Dacron fabric and pressing it between toothed clamping plates machined into the piston head. A prototype device was implanted beneath the LD of a mongrel dog and the muscle stimulated for 8 weeks (33 Hz, 9 pulses/burst, >2.6x106 contractions) following a 7-day recovery period. Piston position was fixed to maximize forces across tissue/device attachment points. Stimulation produced palpable contractions throughout the implant period. At explant, the device was fully encapsulated in its original location with LD tendon firmly attached. LD adhesions to the device were minimal, but were significant around and above the piston head. Thick fibrous ingrowth through the wire mesh formed a secure bond to the chest wall. A thinner, non-adherent fibrous layer encased the main housing and piston head. Biopsies from LD and surrounding tissues appeared normal under histologic examination. This study suggests that the use of a porous backing plate and Dacron-reinforced tendon clamp mechanism may provide an effective means to anchor motor prostheses for muscular actuation.

113 小型2サイクルエンジンピストンクラウン部の燃焼堆積物分布と温度の関係(熱工学)

It has been known that the combustion chamber deposit (CCD) makes various problems on engine property. Especially, the CCD formation in the two-stroke cycle engines is more than four-stroke. In this report, we have studied about the relation between the CCD distribution and the temperature profile on the piston head in a small two-stroke cycle engine for getting the understanding CCD formation mechanism in this engine types. The temperature was measured using many fusible plugs (FP) which has different fusing point embedded on a piston crown surface.

712 火花点火エンジンにおける壁面近傍伝播火炎の画像による乱流特性解析(OS-6 反応流動の解析および運転制御)

Premixed-charge propagating flame front in combustion chamber was visualized by using Mie-scattering technique. Rapid compression expansion machine, which has a square combustion chamber, enables to observe flame propagation in proximity of piston and cylinder head walls. The wrinkled structure of turbulent flame was analyzed by fractal analysis.

Double Adjustable Shock Absorbers Using Electrorheological Fluid

Double adjustable shock absorbers allow for adjustment of their yield force and post-yield damping. To emulate the performance of a conventional double adjustable shock absorber, an electrorheological (ER) automotive shock absorber was designed and fabricated at the University of Maryland. An applied electric field between two tubular electrodes, located in the piston head, increases the force required for a given piston rod velocity. Two different shaped gaps between the electrodes, meet the controllable performance requirements of a double adjustable shock. A uniform gap primarily adjust the yield force of the shock absorber, as opposed to a non-uniform gap which allow for control of the post-yield damping. Force measurements from sinusoidal displacement cycles, recorded on a 5 HP mechanical dynamometer, validate the performance of uniform and non-uniform gaps for yield force and post-yield damping adjustments.

Analysis and Testing of Electrorheological Bypass Dampers

We experimentally validate nonlinear quasi-steady electrorheological (ER) and magnetorheological (MR) damper models, using an idealized Bingham plastic shear flow mechanism, for the flow mode of damper operation. An electrorheological valve or bypass damper was designed, and fabricated using predominantly commercial off-the-shelf hydraulic components. Both the hydraulic cylinder and the bypass duct have cylindrical geometry, and damping forces are developed in the annular bypass via Poiseuille (flow mode) flow. Damper models assume parallel plate geometry. Three nondimensional groups are used for damper analysis, namely, the Bingham number, Bi, the nondimensional plug thickness, 6, and the area coefficient defined as the ratio of the piston head area, AP, to the cross-sectional area of the annular bypass, Ad. In the flow mode case, the damping coefficient, which is defined as the ratio of equivalent viscous damping of the Bingham plastic material, Ceq, to the Newtonian viscous damping, C, is a function only of the nondimensional plug thickness. The damper was tested using a mechanical damper dynamometer for sinusoidal stroke of 2 in., over a range of frequencies below 0.63 Hz. The damping coefficient vs. nondimensional plug thickness diagram was experimentally validated using these data over a range of damper shaft velocities or frequencies and applied electric fields. Because the behavior of ER and MR fluids are qualitatively similar, these ER damper modeling results can be extended to analysis of flow mode MR dampers.

Analysis and Testing of Electrorheological Bypass Dampers

We experimentally validate nonlinear quasi-steady electrorheological (ER) and magnetorheological (MR) damper models, using an idealized Bingham plastic shear flow mechanism, for the flow mode of damper operation. An electrorheological valve or bypass damper was designed, and fabricated using predominantly commercial off-the-shelf hydraulic components. Both the hydraulic cylinder and the bypass duct have cylindrical geometry, and damping forces are developed in the annular bypass via Poiseuille (flow mode) flow. Damper models assume parallel plate geometry. Three nondimensional groups are used for damper analysis, namely, the Bingham number, Bi, the nondimensional plug thickness, 6, and the area coefficient defined as the ratio of the piston head area, AP, to the cross-sectional area of the annular bypass, Ad. In the flow mode case, the damping coefficient, which is defined as the ratio of equivalent viscous damping of the Bingham plastic material, Ceq, to the Newtonian viscous damping, C, is a function only of the nondimensional plug thickness. The damper was tested using a mechanical damper dynamometer for sinusoidal stroke of 2 in., over a range of frequencies below 0.63 Hz. The damping coefficient vs. nondimensional plug thickness diagram was experimentally validated using these data over a range of damper shaft velocities or frequencies and applied electric fields. Because the behavior of ER and MR fluids are qualitatively similar, these ER damper modeling results can be extended to analysis of flow mode MR dampers.

Experimental study of the laser quenching of 40CrNiMoA steel

Abstract The service life of the piston head and the stability of a large diesel engine are greatly affected by the wear resistance of the groove of the piston head. Conventional high-frequency quench-and-temper treatment results in several deleterious effects that may impair the anti-friction and wear properties of the groove of the piston head. Laser surface quenching is a new candidate technique. In this study, based on orthogonal experimental design, the effect of the surface condition, the laser power, the traverse speed, the incident angle and the gas flow rate on the quenched zone of 40CrNiMoA steel was investigated systematically. The profile, hardness and microstructure of the quenched zone vary with the surface condition, the laser power, the incident angle and the traverse speed. However, they are not significantly affected by the gas flow rate. The optimum processing parameters are obtained for the laser quenching of the groove of the piston head. Using the optimum processing parameters, quenched zones with not only sufficient case depth and greater hardness but also of a suitable profile and a finer microstructure, are obtainable. The hardness of the laser quenched zone is substantially higher than that resulting from conventional high-frequency quench-and-temper treatment.

Malleus-to-footplate prosthetic interposition: Experience with 265 patients

Absence of the long process of the incus with or without absence of the stapes head accounts for more than 80% of ossicular discontinuities. Total or partial replacement prostheses, made of various materials, are interposed to restore the transfer function of the middle ear. To simplify ossicular reconstruction, reduce operative times and costs, improve functional outcomes, and avoid the risk of infections, we have adopted, during the past 10 years, a technique that makes use of a personally designed alloplastic prosthetic device. The prosthesis connects the malleus to the footplate, even in the presence of the stapes superstructure. This malleus-to-footplate prosthesis consists in a plastipore-coated steel piston and hydroxyapatite head, complete with a groove. The groove is placed beneath the malleus neck after dissection of the tensor tympani tendon and the shaft of the piston on the footplate. Two hundred ninety primary ossiculoplasties with the malleus-to-footplate prostheses were performed in 265 patients from 1986 to 1995 in the ENT Department of the University of Verona. The average postoperative air-bone gap at 0.5 to 3 kHz was 11 dB at 1 year and 14 dB at 5 years. These outcomes are significantly better than those personally obtained previously with ossicular or alloplastic prostheses. No extrusions occurred. The structural characteristics of the malleus-to-footplate prosthesis endow the prosthesis with a high degree of biocompatibility and stability and optimal sound-transfer function. The rationale for this particular ossiculoplasty procedure is discussed. (Otolaryngol Head Neck Surg 1999;120:437-44.)