Piston Set Research Articles

PROFILING THE SURFACE OF THE PIN HOLE IN THE PISTON BODY

Minimization of the mass of the piston kit, which consists of three main parts - piston, pin and connecting rod, is connected, among other things, with the possibility of reducing the diameter of the steel pin. On the other hand, a decrease in its diameter inevitably leads to an increase in stresses in the piston pin hole (PPH) and possible destruction. It is known that reducing the mass of the piston set from 5 to 20% leads to an increase in the output parameters of the internal combustion engine - torque and power by 1% to 4.5%. The purpose of the study is to determine the possibility of reducing the stresses in the bearing due to the profiling of its surface while reducing the diameter of the piston pin. The research algorithm is presented, which consists of building a geometric model of the piston assembly, loading with excessive pressure taking into account the plasticity of the material, modifying the geometry of the PPH and checking the stresses of the loaded state. The conventional piston model has the following geometry: diameter – 80 mm; height – 60 mm; compression height – 30 mm; the diameter of the finger hole is 18 mm; the distance between the bumps is 28 mm. Piston material – aluminum-based alloy – AISI 2014-0, pin and connecting rod material – AISI 1020 steel. Pressure loading conditions: taking into account plasticity – nonlinear, harmonic, 2 cycles, maximum amplitude – 8 MPa; test - static, 6.5 MPa. A crumpling zone with residual deformations was detected in the PPH, the maximum final deformation practically does not differ in the first and second load cycles (0.0081 vs. 0.0084). Residual deformations occur 1/3 of the length from the inner edge of the head. The absolute residual deformations are given in the form of a sweep of the change in the PPH radius. The maximum value is about 0.04 mm. This result is the basis for modifying the geometry of the surface of the finger hole. The modified geometry of the PPH is obtained by boring the cylindrical surface with a profile modeled by the appropriate spline on the geometric model. The boring axis is offset by 0.02 mm from the PPH axis. Verification modeling showed that the averaged loads on the edge of the model are 143 MPa for the cylindrical and 107 MPa for the modified PPH (-25% for the modified profile).

A Novel Coaxial Balance Mechanism for Reciprocating Piston Engines

Vibration is an important issue faced by reciprocating piston engines, and is caused by reciprocating inertia forces of the piston set. To reduce the vibration without changing the main structure and size of the original engine, we proposed a novel coaxial balance mechanism design based on a compact unit body. By introducing a second-order balance mass, this mechanism can significantly increase the efficiency of vibration reduction. The proposed mechanism can effectively balance the first-order and second-order inertia forces with the potential of balancing high-order inertia forces. To accurately determine the second-order balance mass, a closed-form method was developed. Simulation results with a single-cylinder piston DK32 engine demonstrate the effectiveness and advantage of the proposed mechanism. At a crankshaft speed of 2350 r/min, compared with the first-order balance device, the average root mean square velocity of the test points on the engine’s cylinder was reduced by 97.31%, and the support reaction force was reduced by 96.54%.

The Influence of A Cross-Channel Extrusion Process on The Microstructure and Properties of Copper.

A new cross-channel extrusion (CCE) method with the application of a back pressure (BP) is proposed and experimentally tested. The introduction of pressure blocks the free flow of material by using an additional set of pistons, which prevents the loss of consistency. The paper presents results of experimental trials of CCE process. Between one and eight passes of CCE with and without a BP were applied to pure copper billets to refine their initial coarse-grained microstructure at room temperature. It was found that processing by CCE results in the formation of a lamellar structure along the extruded axis and the fine-grained structure in the remaining volume. The material exhibited dynamic recrystallization, which results in the formation of 0.5- to 2-μm grains after one pass and 2- to 8-μm grains after four CCE passes. The fine-grained material had YS of 390-415 MPa. An increase in the microhardness from 70 to 130 HV02 after one pass and then a decrease after four passes were observed. This might indicate that secondary recrystallization and selective grain growth occur, because an exothermic peak (158.5 °C, 53 ± 2.1 J/mol) was observed during DSC (differential scanning calorimetry) testing. The resistivity of the once deformed copper significantly decreases, while its further processing causes the resistivity to increase.

A moving model rig with a scale ratio of 1/8 for high speed train aerodynamics

To achieve an accurate aerodynamic optimization of the outline of a high speed train and an experimental simulation of the meeting of two trains, especially in a tunnel, a train model in a moving model rig (MMR) should feature a large scale ratio and be capable of accelerating to the real Mach number. For this purpose, an MMR is developed for the acceleration, testing, and deceleration of a train model along opposite directions. To meet the railway standards of China, the distance between the centers of the two tracks is set to 625mm for the scale ratio of 1/8. The powers of the train models originate from compressed air and the brake force from the motion of the permanent magnets relative to the motionless steel plates along the tracks. The compressed air from an air gun with an air chamber pushes a set of pistons in an accelerating tube forward. These pistons tow a trailer through a towrope, and this trailer drives the train model up to a certain speed. The initial pressure of the compressed air determines the speed of the train model, and the brake distance depends on the kinetic energy of the model and the weight of magnets on the bottom of the model. The corresponding experimental measurements are presented in this work. Two train models weighing 265 and 106kg can be accelerated to speeds of 401 and 507km/h, respectively, within a brake distance of 70m. Thus, the train model with one or several cars can have a scale ratio of at least 1/8. Additional experimental results on the evolution of the pressure wave on the tunnel wall are introduced to demonstrate the repeatability of the experiment on the train model passing through the tunnel model.

Miscibility, phase separation and volumetric properties in solutions of poly(ɛ-caprolactone) in acetone + CO2 binary fluid mixtures at high pressures

Miscibility and phase separation behavior, and the volumetric properties of poly(ɛ-caprolactone) (PCL) solutions in acetone+CO2 binary fluid mixtures were investigated for PCL concentrations of 2.0, 5.0, 9.0, 12.0, 15.0, 25.0 and 34.9wt% at temperatures up to 410K and pressures up to 28MPa. Experiments were carried out by using a unique high pressure variable-volume view-cell equipped with a dual set of pistons and dual set of sapphire windows which permit measurements of both the transmitted light intensities for determination of phase boundaries, and the scattered light intensities for assessment of the mechanism and the kinetics of phase separation. The system allows the continuous recording of the piston positions and thus the solution densities as a function of pressure at a given temperature from which liquid–vapor or liquid–liquid–vapor phase boundaries are easily assessed and the isothermal compressibilities and isobaric expansivities are readily evaluated. It is shown that these solutions display lower critical solution temperature (LCST) type behavior with respect to their liquid–liquid (LL) phase boundaries and the LL phase separation proceeds via nucleation and growth for 2.0, 5.0, 25.0 and 34.9wt% solutions and via spinodal decomposition for 9.0, 12.0, and 15.0wt% solutions. It is shown that the LL phase separation pressure which is a function of temperature scales with the solution density and shifts to higher densities with increasing polymer concentration, with the rate of change of LL phase separation pressure with density becoming higher at concentrations above the critical polymer concentration. The compressibilities in the homogeneous mixtures are found to decrease with increasing PCL concentration. At pressures below the LL phase separation pressures, the rate of decrease in compressibility with pressure is higher which is interpreted as being a consequence of the difference in the phase compositions of the polymer-lean and polymer-rich phases that develop at pressures below LL phase separation. Isobaric expansivities increase with temperature at a given pressure. They become more sensitive to temperature at lower pressures. The excess volumes for all PCL solutions display large negative values, indicative of close-packing of the polymer plus solvent molecules.

Light scattering behavior and the kinetics of pressure-induced phase separation in solutions of poly(ε-caprolactone) in acetone + CO2 binary fluid mixtures

The miscibility and the kinetics of pressure-induced phase separation in solutions of poly(ε-caprolactone) (PCL) in acetone + CO2 binary fluid mixtures have been studied at pressures up to 28 MPa and temperatures up to 410 K using a unique high pressure view-cell equipped with a dual set of pistons and dual set of sapphire windows. One set of the windows separated by 25.4 mm allows the assessment of the phase state and is used to monitor the transmitted light intensities. The second set of windows separated by 50 μm is used to monitor the scattered light intensities over a wide range of scattering vector q (from 0.35 to 4 μm−1) which allows the assessment of the mechanism of phase separation. Investigations have been carried out for a wide range of polymer concentrations, from 2.0 to 34.9 wt%, while holding the acetone-to-CO2 (wt:wt) ratio in each solution at a constant value of 2:1. The dual set of pistons that are employed which are synchronized and motorized create a churn-like action in the cell insuring effective mixing, even at the high polymer concentrations by translating the cell content across a magnetically-coupled rotating mixer impeller. The piston actions assure also that the solution is effectively introduced into the narrow gap between the scattering windows, and refreshed. The solutions at off-critical concentrations undergo pressure-induced phase separation via nucleation and growth mechanism which shows circular symmetric patterns in their light scattering patterns. For these solutions, the Debye–Bueche type scattering function was used to analyze the domain size of the new phase that forms and develops after a pressure quench. The phase separation in solutions at or near the critical polymer concentrations (9.0–15.0 wt%) proceeds via spinodal decomposition which is characterized by the formation and evolution of the spinodal ring patterns corresponding to a maximum in the angular variation of the scattered light intensities. The results in early stage of the spinodal decomposition were described by the linearized Cahn theory. The variation of the scattered light intensity maximum Im and its location in scattering vectors qm with time in the later stage of the spinodal decomposition obey power-law scaling according to Im ∼ tβ and qm ∼ t−α. The results for the 9.0 and 12.0 wt% solutions show that β/α changes its value from β/α > 3 to β/α ≈ 3 with time, indicating the progression of the spinodal decomposition from intermediate to late stage.

Clustering and collapse of a set of adiabatic pistons enclosing granular gases

The clustering instability in granular matter manifests in many physical situations. Here we present an analysis of a set of adiabatic pistons that separate different granular gases. It is shown, by means of a linear stability analysis, that the symmetric state is unstable against small perturbations, leading to a collapse of all the pistons to the outer walls.

The Development of Engine Cylinder Pressure Intelligent Micro Detection System

Basing the development engine cylinder intelligence examination of the pressure micro system to blend a technique according to the information, adopting the microprocessor chip AduC812 in order to develop terrace, launching the cylinder pressure cold booting, rates, and start electric current etc., according the test of the parameter, combine a proof for logically judge to launch the engine cylinder piston set and start to fasten of break down. This paper introduces the design work of hardware which launches the machine cylinder pressure micro system, and combines a solid example to carry on an experiment, compares the engine of starting break down

An improved model for the acoustic radiation impedance of the mouth based on an equivalent electrical network

This paper proposes a model for acoustic radiation impedance of the mouth in the form of the equivalent electrical network. Five known models of radiation impedance are compared: radiation of a circular piston set in a spherical baffle: radiation of a circular piston set in an infinite baffle, the Flanagan model, the Wakita and Fant model, and the Stevens, Kasowski and Fant model. The proposed model most accurately approximates the radiation impedance of a circular piston set in a spherical baffle. Differences between the acoustic resistance and reactance calculated by the proposed model and the piston set in a spherical baffle of 9 cm radius are relatively small in the kr < 2 region. The deviations in calculated values of the acoustic resistance and the reactance are within ±0.023 × ρc/ A m and ±0.008 × ρc/ A m, respectively, where A m denotes the area of the mouth aperture. The accuracy of the proposed model is demonstrated by vowel formant frequency calculations. Differences in formant frequencies calculated by applying the proposed model and the piston set in a spherical baffle model are less than 0.3%.

Active control of radiation from a piston set in a rigid sphere.

Active control of the sound radiated from a piston set in a rigid sphere with a set of control point sources around is considered in this paper, where the scattering sound field of the control sound from the rigid sphere has been taken into account to minimize the total radiated sound power. Analytic results of the sound power are obtained and numerical simulations show that it is possible to reduce the radiation from a small piston set in a rigid sphere similar to the size of a human head up to a certain frequency. It is found that the introduction of the scattering object makes significant differences from the active control without scattering objects. This being the case, the scattering object makes the active noise control easier. To increase the global reduction of sound-power output, the optimal number and locations of the control sources and the optimal number and locations of error sensors are discussed. Finally, experiments with one control source and one error sensor around a head simulator have been carried out to verify the simulation results.

Design for a novel MRF semi active damper and certification of the nonlinear controller's effects

This paper deals with a novel type of semi active damper, which is composed of a cylinder injected with Magnetic Rheological Fluid (MRF) and an electromagnet with a nonlinear H/spl infin/ controller. It is generally known that the viscosity of MRF can be changed by the magnitude of a magnetic field. Therefore, this study aims at constructing such a semi active damper system that makes good use of the property. A flow for controlling the semi active damper system is as follows. First, if an electromagnet current is changed, the magnitude of the magnetic field generated by the current is changed. Next, the viscosity of MRF is also changed by the magnetic field. Thus, the motion of a piston set under the MRF is controlled. As these results, an overall equivalent damping coefficient in the semi active damper system can be controlled by the electromagnet current. Thus a semi active damper is made and its properties are measured. In addition, a suitable nonlinear compensator for the MRF damper is installed, various vibration experiments are carried out and many interesting results are reported.

Structure of surface layers and wear resistance of quenched 50G steel after finishing, antifriction, nonabrasive treatment

The effect of the finishing, anti~ction, nonabrasive treatment (FANT) on the structure of the surface layer of the 50G steel subjected to quenching with rf heating without any friction is investigated. Ideas are formulated about the mechanism of formation of the surface layer. Structural parameters of the quality of the coatings determined by the method of nondestructive testing of the surface layers are presented, which can be used as criteria for rapid estimation of the conditions of technological surface treatment. The aggregate of tribotechnical properties of parts of cylindrical piston group including the wear resistance of linings, rings, and pistons, the coefficient of friction, breaking-in ability of the cylinder-lining--piston-ring pair, and the compatibility between the contacting metallic materials refer to factors that control the reliability and longevity of the internal-combustion engines. These properties can be estimated under service-, bench-testing-, and laboratory-testing conditions. A comparison between the results of laboratory tests using machines that produce reciprocating sliding with the wear data on linings and piston rings obtained during service [1 and others] showed that they were qualitatively in agreement, which indicates that it is expedient to estimate the tribotechnical properties in laboratory tests. These tests happen to offer unique possibilities for obtaining a separate estimate of the quality of a pair consisting of a cylinder--piston set needed for the substantiation of the approach toward the choice the structural and lubricating materials, the conditions of the technological processing of the surface parts leading to reduced losses by friction and wear. One of the methods of improving the tribotechnical properties of the parts of a cylinder--piston set is the brass plating or a finishing, antifriction, nonabrasive treatment (FANT) of the surface [2-4]. This treatment is also technologically simple, as well as effective in preventing seizure and decreasing friction and wear. However, according to the data of [4], depending upon the service conditions the effect of FANT may not even be manifest which gives us reaso~ to assume that a negative result is possible depending upon many factors, particularly the structural state of the treated material. Such cases were observed in practice during the service of internal-combustion engines. In this paper, based on the results of laboratory tests on the lining--ring friction pair, we have analyzed the changes in the structure of the surface layer of the quenched 50G steel subjected to FANT, their effect on wear resistance, as well the quality of the surface layer. Using a 77MT-1 reciprocating sliding-friction machine (at a pressure of 30 MPa and average velocity of 0.1 m/sec),

Application of BEM (boundary element method)-based acoustic holography to radiation analysis of sound sources with arbitrarily shaped geometries

A method employing holograms that conform with arbitrarily shaped sources has been developed for enhancing conventional near-field acoustic holography, which has been limited to sources with simple geometries, e.g., planar or cylindrical surfaces. Four holography transformation algorithms have been developed, based on acoustic holography theory and the boundary element method (BEM). Singular value decomposition (SVD) has been incorporated into the algorithms in order to alleviate the ill-posed nature frequently encountered in backward reconstruction of a field. A pulsating sphere, a cylinder with spherical endcaps, and a vibrating piston set in a rigid sphere have been adopted in a numerical simulation for verifying the algorithms. Satisfactory agreement has been achieved between the holographically transformed results and the analytical solutions.

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Holographic reconstruction of odd‐shaped 3‐D sources

As previously described [J. D. Maynard, J. Acoust. Soc. Am. Suppl. 174, S37 (1983)], nearfield acoustical holography can reconstruct the surface velocity and pressure over a level surface in a separable coordinate system from measusrements of the radiated pressure field over a parallel level surface. This study investigates the feasability of reconstructing the surface pressure and normal velocity over surfaces which do not conform to a level surface. Such a reconstruction involves numerically determining a distribution of surface pressure and velocity which satisfies the surface Helmholtz integral equation and which is consistent with the Helmholtz integral equation for the pressure field measured on the level surface. Details of the algorithm and results of computer simulations for a uniformly pulsating sphere and a piston set in a sphere (measurements simulated over a planar surface) are presented. [Work supported by ONR and NASA.]

Transient field of a baffled planar piston having an arbitrary vibration amplitude distribution

A theoretical model is presented for evaluating the transient velocity potential and pressure fields radiated by a pulsed planar piston set in an infinite rigid baffle and having an arbitrary spatial velocity distribution. The method is based on the development of a generalized spatial impulse response function which describes the velocity potential, either at a point or averaged over a finite receiving surface, resulting from the velocity impulse excitation of a uniformly or nonuniformly vibrating piston source. For the specific case of a circular source and receiver this function is plotted using several source distributions and receiver sizes. Then corresponding plots are presented for two piston velocity waveforms: a Gaussian pulse and a Gaussian-modulated sinusoidal burst. These plots are compared and the effects of a nonuniformly vibrating source and finite receiver are discussed. Lastly, a previous solution by Schoch, in which the field of a rigid piston is separated into geometrical and boundary diffraction waves, is extended to account for a nonuniform source, and the relationship of this more general result to the present approach is illustrated.

Theoretical study of the pulsed ultrasonic field radiated by a nonuniformly vibrating planar piston source

A mathematical method is presented for evaluating the transient field radiated by a pulsed planar piston set in an infinite rigid bafffle and having an arbitrary spatial velocity distribution. The method allows for the field to be found at a point or averaged over a finite receiving surface. The approach taken is based on an expanded convolution integral representation of the transient field using a generalized spatial impulse response function development. To illustrate the effect of a nonuniform source and finite receiver on the detected transient field, the generalized spatial impulse response is plotted for several receiver sizes and source distributions representable by analytic functions. Then corresponding plots are presented for two piston velocity waveforms: A Gaussian pulse and a Gaussian‐modulated sinusoidal burst. Lastly, the relationship of this theoretical method to other mathematical descriptions of the field radiated by a planar piston is discussed. In particular, the “plane” and “edge” wa...

The effect of flow on the piston problem of acoustics

A compressible fluid, bounded on one side by an infinite plane, flows with constant subsonic speed U parallel to the plane, and acoustic disturbances are caused by a small amplitude vibration of a circular piston set in the plane. The effect of the mean flow on this classical radiation problem is investigated and the distant field is expressed in elementary form. For the compact piston, whose radius is small compared with a wavelength, it is confirmed (in agreement with earlier work) that the distant field is not simply that of a point source with strength equal to the displaced volume flux since the piston has an additional blockage effect on the mean flow. The total excess energy flow is calculated for the compact piston with any subsonic mean flow (and also for the non-compact piston with low Mach number mean flow) and is compared with that for the complementary problem of a moving piston in a quiescent fluid. Since this is the previous problem referred to a reference frame that moves with the mean flow, the pressure and velocity fluctuations are as before, but the energy balance is different since the drag force on the piston does work in the latter case.

Boundary integral solutions of three dimensional acoustic radiation problems

This paper is concerned with the development of a procedure for generating the sound fields radiated by arbitrarily shaped, three dimensional bodies from an integral representation of the solutions of the Helmholtz equation. The method of Burton and Miller is employed to eliminate the non-uniqueness in the external Helmholtz formulae which occurs at the internal eigenfrequencies of the geometry under consideration. Also, a representation of the most singular component in the Burton and Miller formulation is developed resulting in an integral equation which is amenable to numerical solutions. A simple numerical scheme is introduced which reduces the large amounts of computer storage and time normally required for the solution of similar problems. This numerical scheme is then used to obtain solutions for the radiated sound field generated by a vibrating piston set in a sphere. The numerical solutions for the surface and far field sound patterns are compared with exact analytical solutions and deviations of 10% at most are noted. Since the symmetry of the sphere was not taken advantage of in these computations, the numerical schemes employed are applicable to general three dimensional sound radiation problems.

The radiation of sound from a piston set in a non-rigid baffle

We consider the far-field radiation pattern produced by a vibrating circular piston set in a plane non-rigid impedance condition baffle. Using an extension of an approximate method suggested by Mangulis, a simple formula is derived for the radiation pattern function, and its accuracy is assessed by a comparison with some numerical results of Mangulis.