Showing papers on "Piston published in 2018"

A Critical Review on Physical Vapor Deposition Coatings Applied on Different Engine Components

Abstract: Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented ...

Noise Reduction of an Axial Piston Pump by Valve Plate Optimization

Abstract: Current researches mainly focus on the investigations of the valve plate utilizing pressure relief grooves However, air-release and cavitation can occur near the grooves The valve plate utilizing damping holes show excellent performance in avoiding air-release and cavitation This study aims to reduce the noise emitted from an axial piston pump using a novel valve plate utilizing damping holes A dynamic pump model is developed, in which the fluid properties are carefully modeled to capture the phenomena of air release and cavitation The causes of different noise sources are investigated using the model A comprehensive parametric analysis is conducted to enhance the understanding of the effects of the valve plate parameters on the noise sources A multi-objective genetic algorithm optimization method is proposed to optimize the parameters of valve plate The amplitudes of the swash plate moment and flow rates in the inlet and outlet ports are defined as the objective functions The pressure overshoot and undershoot in the piston chamber are limited by properly constraining the highest and lowest pressure values A comparison of the various noise sources between the original and optimized designs over a wide range of pressure levels shows that the noise sources are reduced at high pressures The results of the sound pressure level measurements show that the optimized valve plate reduces the noise level by 16 dB(A) at the rated working condition The proposed method is effective in reducing the noise of axial piston pumps and contributes to the development of quieter axial piston machines

Thermo-mechanical fatigue behavior and life prediction of the Al-Si piston alloy

Abstract: The thermo-mechanical fatigue (TMF) behaviors and corresponding damage mechanisms of Al-Si piston alloy were investigated in the temperature ranges of 120–350 °C and 120–425 °C in this study. For TMF cyclic stress response behavior, the rapid cyclic softening occurs in the initial stage and then the cyclic stress maintains stable at lower strain amplitudes; but the cyclic stress displays gradual decrease up to the final failure at higher strain amplitudes. For TMF damage behavior, the cracks mainly initiate from the broken primary silicon in the temperature of 120–350 °C range, and commonly nucleate from the boundary between primary Si and matrix in the temperature of 120–425 °C range. For both cases, creep may have obvious influence and result in the formation of many micro-voids, but the oxidation may only have a little effect. A new energy-based model for low-cycle fatigue (LCF) and TMF life prediction was proposed based on the hysteresis energy with strain rate modification, considering both fatigue and creep damages. The predicted results agree well with the experimental ones for the Al-Si piston alloy.

Work production of quantum rotor engines

Abstract: We study the mechanical performance of quantum rotor heat engines in terms of common notions of work using two prototypical models: a mill driven by the heat flow from a hot to a cold mode, and a piston driven by the alternate heating and cooling of a single working mode. We evaluate the extractable work in terms of ergotropy, the kinetic energy associated to net directed rotation, as well as the intrinsic work based on the exerted torque under autonomous operation, and we compare them to the energy output for the case of an external dissipative load and for externally driven engine cycles. Our results connect work definitions from both physical and information-theoretical perspectives. In particular, we find that apart from signatures of angular momentum quantization, the ergotropy is consistent with the intuitive notion of work in the form of net directed motion. It also agrees with the energy output to an external load or agent under optimal conditions. This sets forth a consistent thermodynamical description of rotating quantum motors, flywheels, and clocks.

A Free-Piston Linear Generator Control Strategy for Improving Output Power

Abstract: This paper presents a control strategy to improve the output power for a single-cylinder two-stroke free-piston linear generator (FPLG). The comprehensive simulation model of this FPLG is established and the operation principle is introduced. The factors that affect the output power are analyzed theoretically. The characteristics of the piston motion are studied. Considering the different features of the piston motion respectively in acceleration and deceleration phases, a ladder-like electromagnetic force control strategy is proposed. According to the status of the linear electric machine, the reference profile of the electromagnetic force is divided into four ladder-like stages during one motion cycle. The piston motions, especially the dead center errors, are controlled by regulating the profile of the electromagnetic force. The feasibility and advantage of the proposed control strategy are verified through comparison analyses with two conventional control strategies via MatLab/Simulink. The results state that the proposed control strategy can improve the output power by around 7–10% with the same fuel cycle mass.

Experimental and numerical investigation of flow forces in a seat valve using a damping sleeve with orifices

Abstract: The power of hydraulic piston engines is much affected by the on-off valves which control the fuel injection of the piston assembly. Therefore, the opening time of the seat valve used as the on-off valve is optimized by minimizing the axial flow forces on the spool. A damping sleeve with orifices is proposed to change the valve internal geometry. Experimental and numerical investigations of the flow forces acting on the spool with and without the proposed damping sleeve are carried out to identify the differences in the flow field and to minimize the forces’ effect. The simulated results fit the experimental results well. Both results show that the proposed damping sleeve affects the pressure distribution along the spool cone surface and the jet stream direction significantly. The effects of the orifice’s width, height, and relative sleeve installation positions on the flow field and cavitation are assessed using simulation methods. As a result of the flow field changing, the damping sleeve can reduce the flow forces significantly and even reverse the forces’ direction at the cost of a little flow loss. The opening time of the seat valve can be reduced by 31% to 0.67 ms by using the proposed damping sleeve.

Piston geometry effects in a light-duty, swirl-supported diesel engine: Flow structure characterization:

Abstract: This work studied how in-cylinder flow structure is affected in a light-duty, swirl-supported diesel engine when equipped with three different piston geometries: the first two featuring a conventio...

Optimization of Pocket Geometry for Friction Reduction in Piston–Liner Contacts

Abstract: It has recently been shown that rectangular surface pockets are effective in reducing friction in a piston–liner type contact, providing that they are oriented with their long axis transverse to th...

Design of piston bowl geometry for better combustion in direct-injection compression ignition engine

Abstract: The current computational fluid dynamics (CFD) study presents the effect of piston bowl geometry on the performance and emissions of a direct-injection diesel engine. Different piston bowl profiles, namely, hemispherical combustion chamber (HCC), shallow depth combustion chamber (SCC) and toroidal combustion chamber (TCC), have been created with a baseline compression ratio of 17.5. CONVERGETM CFD code coupled with the SAGE combustion model was used for numerical analysis. It is observed that the TCC piston bowl geometry renders better air–fuel mixture inside the cylinder, which leads to a homogeneous charge. Further, numerical experiments are carried out to analyze suitable TCC piston bowl geometry by varying the depth of the bowl. Out of all the cases, the case with 1.26 mm decrease in depth of bowl from the baseline (TCC) design gives better emissions and performance characteristics.

Effect of Untampered Plasma Coating and Surface Texturing on Friction and Running-in Behavior of Piston Rings

Abstract: The running-in behavior and the associated transient friction characteristics of a piston ring with different surface treatments are experimentally evaluated using a custom-made engine testing apparatus. Results are reported for a series of running-in and steady-state experiments on piston rings with different combinations of coated and textured surfaces. Comparisons are provided between five different types of piston rings: (1) with no textures; (2) with textures only; (3) with coating only; (4) first textured and then coated; and (5) first coated and then textured. A combination of the texturing and coating showed 12.5% improvement in the frictional behavior and up to 50% improvement in break-in time compared to cases when only one surface treatment was applied.

Modeling and measurement of a moving coil oil-free linear compressor performance for refrigeration application using R134a

Abstract: A prototype of the compressor with moving coil type linear motor has been developed. The developed compressor is integrated with test loop using R134a refrigerant to confirm its performance. The simulation results are validated with the experimental data. The experimental results from the test loop with strokes of 10, 11 and 12 mm for three different pressure ratios of 4, 7, 10 are presented and discussed in this paper. The COP of the system calculated is 1.4 from the test results (for 54 °C condenser temperature and −20 °C evaporator temperature) with the stroke of 10 mm, pressure ratio of 10 and cooling capacity of 134 W. The maximum COP of 2.13 is achieved (for 54 °C condenser temperature and 2 °C evaporator temperature) with the stroke of 12 mm, pressure ratio of 4 and cooling capacity of 325 W. Normal refrigerator compressors utilize lubricant oil but as the refrigerant is changed the oil suitable for particular refrigerant also needs to be changed. The novel linear compressor tested does not utilize lubricant oil. The linear compressor has only one friction point i.e. between the piston and cylinder. The linear compressor utilizes Rulon (low coefficient of friction material) as a special material coated on the piston surface in contact with the cylinder. The oil-free operation of the compressor helps in adapting the refrigerator to different refrigerants without having to consider a change of lubricating oil. Refrigeration system performance with both linear compressor and the conventional reciprocating compressor is measured and compared. System COP with the linear compressor is 18.6% more than with the commercially available reciprocating compressor. The absence of connecting rod and crank mechanism accompanied with oil-free operation due to reduced friction enhance the performance of the linear compressor.

The Dynamics of the Otto Engine

Abstract: The dynamic calculation of a certain mechanism and of the piston crankshaft mechanism, used as the main mechanism for Otto internal combustion engines, also implies the influence of external forces on the actual, dynamic kinematics of the mechanism. Take into account the strong and inertial engine forces. Sometimes weight forces can also be taken into account, but their influence is even smaller, negligible even in relation to inertial forces that are far higher than gravitational forces. In the present paper, one carry out an original method of determining the dynamics of a mechanism, applying to the main mechanism of an Otto or diesel engine. The presented method of work is original and complete. Relationships (1) express the velocity of the center of gravity to calculate the moment of inertia (mechanical or mass, of the whole mechanism) reduced to the crank (2). In dynamic calculations, the first derivative of the reduced mechanical inertia moment, derived by the angle FI (relations 3-4), is also required. For dynamic calculation, it is also necessary to determine the expression of the total torque momentum and crank-resistance forces (relations 5-6). The differential equation of the machine (7) is arranged under the more convenient forms (8) to solve it. It is easily observed that a second-degree equation has been reached, which is solved by the known formula (9).

A Review of the Design and Control of Free-Piston Linear Generator

Abstract: The Free-piston linear generator (FPLG) is a novel energy converter which can generate electrical energy and is regarded as a potential technology for solving the restriction of the short driving range of electric vehicles. Getting rid of the crank and flywheel mechanism, FPLG obtains some advantages of a variable compression ratio, compact size, and highly-efficient power generation. Linear electric machine (LEM) design and piston motion control are two key technologies of FPLG. However, they are currently the main obstacles to the favorable performance of FPLG. LEM being used to drive the piston motion or generate electric energy is an integrated design including a motor/generator. Various types of LEMs are investigated, and suitable application scenarios based on advantages and disadvantages are discussed. The FPLG’s controller is used to ensure stable operation and highly-efficient output. However, cycle-to-cycle variations of the combustion process and motor/generator switching make it difficult to improve the performance of the piston motion control. Comments on the advantages and disadvantages of different piston motion control methods are also given in this paper.