Piston Head Research Articles

Experimental visualization of gas–liquid two-phase flow during reciprocating motion

The piston-cooling system is one of the critical elements that impact on the thermal management of engines. At present, the use of a cooling gallery inside the piston head makes it possible to optimize the heat extraction and control the piston temperature effectively. However, owing to the small space in piston galleries and their complicated structure, it is rather difficult experimentally to perform accurate visual observations of the internal cooling oil and study the heat transfer characteristics. In the current work, a high-speed camera was employed to capture the flow patterns of water and air inside a simplified piston gallery at various crank angles. The heat transfer mechanisms in gas–liquid two-phase flow during reciprocating motion were explored. The effects of oscillation frequency and water filling ratio were discussed. An effective method was developed to achieve a full understanding of the flow and heat transfer characteristics of cooling medium inside a piston cooling gallery. This could provide an effective method to optimize the thermal management of engines in future.

The heat transfer coefficient calculations of internal combustion engine fuelled with natural gas

In this paper the calculations of heat transfer coefficient in the combustion chamber of the internal combustion engine fuelled with natural gas is presented. The mean value of heat transfer coefficient has been calculated using Woschni and Nusselt equation and compared with results obtained using algorithm based on experimental data. The proposed algorithm can be helpful to determine the average values of heat transfer coefficient from working medium to the combustion chamber walls (crown of a cylinder head, cylinder walls and piston head) during combustion process. The calculation method includes modified one zone heat release model in combustion chamber of SI engine. Proposed method is based on the energy balance equation closed by the coefficient which expresses the heat losses to the walls of the combustion chamber.

THE HEAT TRANSFER COEFFICIENT CALCULATION IN THE ICE CYLINDER BASED ON IN-CYLINDER PRESSURE DATA

In this paper the calculations algorithm of heat-transfer coefficient in the combustion chamber of the internal combustion engine is presented. Developed algorithm is based on the in cylinder pressure data. The proposed algorithm can be helpful to determine the average values of heat-transfer coefficient from working medium to the combustion chamber walls (crown of a cylinder head, cylinder walls and piston head) during combustion process. The calculation method includes modified one zone heat release model in combustion chamber of SI engine. Proposed method consists in closing the energy balance equation by the coefficient which expresses the heat losses to the walls of the combustion chamber. The average value of the heat losses during combustion process is calculated by two steps. Firstly, the integration of the energy balance equation (without specifying the heat losses) leads to designation of the so-called net value of heat released in cylinder. In the next step the amount of the total energy supplied to the cylinder is determined taking into account the chemical energy of the supplied fuel. The difference between the supplied value of chemical energy and heat released net value allows to determine the heat losses average value. In last stage, the heat flow equation leads to calculate the mean value of heat transfer coefficient during combustion process.

Interring Gas Dynamic Analysis of Piston in a Diesel Engine considering the Thermal Effect

Understanding the interaction between ring dynamics and gas transport in ring pack systems is crucial and needs to be imperatively studied. The present work features detailed interring gas dynamics of piston ring pack behavior in internal combustion engines. The model is developed for a ring pack with four rings. The dynamics of ring pack are simulated. Due to the fact that small changes in geometry of the grooves and lands would have a significant impact on the interring gas dynamics, the thermal deformation of piston has been considered during the ring pack motion analysis in this study. In order to get the temperature distribution of piston head more quickly and accurately, an efficient method utilizing the concept of inverse heat conduction is presented. Moreover, a sensitive analysis based on the analysis of partial regression coefficients is presented to investigate the effect of groove parameters on blowby.

新設計CADデータへの既存メッシュフィッティング技術の開発

We developed a mesh morphing technique, which can be used to change the shape of existing analytical mesh models, and generated a mesh model for a new shape by morphing the mesh model for the previous one. Therefore, our method is suitable to use for analysis during the early stage of design because it reduces the amount of time required to generate analytical mesh models. However, this technique is impossible to morph a free-form surface, and to change surface type. Accordingly, we developed the fitting morphing technique for solving the problem. This technique is possible to morph based on specification of the STL data as morphed shapes and indication of fitting nodes and movable nodes. We developed a series of techniques that include three distinct features. (1) Geometric feature recognition algorithm based on region growing method. (2) Geometric feature assignment algorithm on the basis of distance and angle of geometric features between original mesh and morphed shapes. (3) Node fitting and moving algorithm by displacement coefficient calculation using Ferguson curve characteristics. We confirmed that this technique can morphed to free-form surface from cylindrical surface by applying to the piston head model. Furthermore, the technique can morphed to maintain the boundary continuity of the shape by applying to the gear model.

WEAR CUMULATING PROCESS FOR FRICTION PAIR IMPLEMENTED BY FIRST ORDER RECURRENCES

Wear determination engages a major part of our efforts in considered numerous tribology problems including animal teeth and joints, human joints, cams, piston, rings, tires, brakes, dirt seals, belts, shoes, fabrics, electrical contacts, tape and CD reader heads and others. At times it seems after numerous observation, that the rate of progress in the knowledge of wear is very slow. Modern design activities are mostly concern in the wear cumulative values determination rather than the wear values determination in successive time units of friction nods during the operation time. Therefore, presented paper determines in analytical way the cumulative wear values of friction nods after specified finite and infinite units of operation time. Therefore are considered the convergences and divergences of wear value cumulative processes for various friction nods. The kind of friction nods depends on type of wear process propagation. Such propagation is described in this paper by the recurrence first order equation. Mentioned equation is formulated with constant or variable parameters. This parameters are determined by virtue of experimental measurements and depend on: bearing materials properties, environmental conditions, roughness of cooperating surfaces, vibration effects, electrical conductivity of materials, hardness of materials, deformations mode of cooperating surfaces, temperature, air humidity, kind of the friction, sliding velocity, loading of the friction nod and others. The range of wearing influence components and devices is endless. Therefore, this paper presents the methods of solutions of numerous specific class of ordinary non-homogeneous recurrence equations of first order with variable coefficients occurring in hydrodynamic theory of bearing especially micro-bearing wear problems. The obtained solutions are examined by means of the UOS operator. The examples presented in this paper determine the abrasive wear cumulative values of micro-bearing system after the indicated time units of operating time. Moreover, after infinite time units of micro-bearing operation are considered the convergences and divergences of the obtained sums of cumulative wear process.

Effects of Electromagnetic Stirring on the Microstructure and High-Temperature Mechanical Properties of a Hyper-eutectic Al-Si-Cu-Ni Alloy

A liquid treatment method by electromagnetic stirring was applied to a hyper-eutectic Al-15wt pctSi-4wt pctCu-3wt pctNi alloy for the piston manufacturing with diecasting process in order to improve high-temperature mechanical properties of the piston heads. The mechanical properties, such as hardness, high-temperature tensile stress, thermal expansion, and high-temperature relative wear resistance, were estimated using the specimens taken from the liquid-treated diecast products, and the results were compared with those of a conventional metal-mold-cast piston.

REVISITING THE ICONIC: THE EXCAVATION OF THE REELFITZ PIT ENGINE AND THE NEWCOMEN STEAM ENGINE IN CUMBERLAND, UK

Examples of excavated 18th-century stationary steam engine sites are very rare in Britain. This article records the rescue excavations ahead of road-building works of one such site in 1974–5 at Reelfitz Pit in Little Clifton, Cumberland. The Reelfitz Pit pumping engine was built around 1780 and abandoned in 1781. The remains uncovered show that the site had two external boilers and a narrow engine house with a cylinder on the ground floor. The excavation uncovered three engine parts from within the engine house: the piston flange from the cylinder, the connecting link from the piston rod to the beam and one of the chain links which fitted into the piston head. The current work discusses the site in terms of the development of the West Cumberland coalfield and in the context of the surviving 18th-century Newcomen engines.

Improvement of the shape of ceramic piston head by optimization and FEM

In the present study, the shape of ceramic piston head was improved by optimization methods. The objective function used was failure probability. The polyaxiality of the stress field was in principle taken into account by the Principle of Independent Action, which is based on Weibull's theory. However because of the large differences in principal stresses, the expression could be simplified. According to the results obtained the probability of failure decreased to 1/10 of the original the volume was reduced by 20 percent principal stress decreased.

Study of mixture formation and early flame development in a research GDI (gasoline direct injection) engine through numerical simulation and UV-digital imaging

The analysis of the mixture formation and early combustion processes in a slightly lean burn gasoline direct injection (GDI) engine is performed by using experimental and numerical techniques. UV–visible natural emission digital imaging is applied in the optically accessible combustion chamber of a research engine. This is equipped with the four-valve head and the same injection system of a commercial turbocharged engine. Optical accessibility is obtained through a quartz window placed on the piston head. Numerical simulations are performed by means of a 3D model developed within the AVL FireTM environment, which exploits an in-house developed sub-model for simulating the spray dynamics. Tests are carried out using commercial gasoline. The cyclic variability of the engine is first analysed in order to properly define a reference average pressure cycle to be used for the validation of the numerical model. This last is then proved as being highly predictive as the start of injection is moved in the working cycle. The main effects of the injection and ignition timing on the characteristic flame development angles, namely on the flame initiation and propagation, are analysed. Flame initiation is visualised both numerically and experimentally.

Design, simulation, and testing of a magnetorheological fluid–based haptic actuator for mobile applications

This article presents a novel design of a miniature haptic actuator based on magnetorheological fluids for mobile applications with the aim of providing various haptic sensations to users in mobile devices. The primary design goal for a haptic actuator for mobile applications is to miniaturize its size while achieving large forces and low power consumption. To this end, this study proposes to design the actuator’s piston head (or plunger) in cone shape and activate multiple modes of magnetorheological fluids. A prototype actuator was designed and fabricated based on a simulation model. Using a dynamic test frame, the performance of the prototype actuator was evaluated in terms of the force (resistive force) produced by the prototype. The results show that the small actuator (10 mm × 10 mm × 6.5 mm) produced a maximum resistive force of about 5 N and the force rate of nearly 80% at 0.3 W. This change in resistive force or the force rate is sufficient to provide several steps of force variation that is explicitly perceivable for operators, depending on the input power. The results demonstrate a feasibility of using the proposed actuator’s applications in mobile devices, conveying realistic haptic sensations to users.

A study of combustion and emissions characteristics of a compression ignition engine processes using a numerical tool

Experimental analysis of a diesel engine gives only the global picture of the in-cylinder processes, through averaged quantities. These averages are sometimes global averages or in some cases taken at each crank angle. To understand the in-cylinder processes better, the distribution of scalars becomes very important. In this paper, Converge, a CFD-tool was used to simulate the closed cycle in-cylinder process of a diesel engine to develop deeper insights into the effects of various injection parameters and compression ratio on engine performance and exhaust emissions. Results from Converge CFD-tool have been validated against the experimental data published in the literature. Effects of compression ratio, number of injector holes, spray angle, half cone angle and injection duration were studied using the validated model. Simulation results indicate that decreasing compression ratio resulted in a significant reduction in NO concentrations with a slight increment in specific fuel consumption (SFC). A narrow spray angle resulted in a considerable reduction of soot and SFC. Spray-to-spray interaction was increased with increasing number of nozzle holes. As a result, higher SFC, CO and soot were observed with increasing number of nozzle holes. Various in-cylinder contour plots showed that the injection with higher injection duration i.e. lower injection pressure produces relatively lower extent of fuel wall wetting and hence resulted in less intensity flames close to the piston head. Increasing the spray angle, number of holes and injection duration resulted in clear decline in exhaust NO concentration.

An experimental study on the effects of spring stiffness on the combustion and dynamic characteristics of a linear engine

We investigated the effects of the stiffness of springs applied to linear compressor chambers experimentally. The applied springs could prevent conflict between the engine piston head and engine head cover as well as be available to save the regenerative energy. The linear engine bore size was 30 mm, the maximum stroke was 31 mm and effective stroke volume of a cylinder was 25.45 cc. The spring stiffness was varied: 0, 0.5, 1.00, 2.9 and 14.7 N/mm. The linear engine was fueled with a pre-mixture combined with LPG (propane 99%) and air. As an experimental result, higher spring stiffness affected growth in regenerative energy and stroke. Also, IMEP was increased by rising stroke. Finally, increased IMEP and regenerative energy made more electricity than no spring.

High shear rate flow in a linear stroke magnetorheological energy absorber

To provide adaptive stroking load in the crew seats of ground vehicles to protect crew from blast or impact loads, a magnetorheological energy absorber (MREA) or shock absorber was developed. The MREA provides appropriate levels of controllable stroking load for different occupant weights and peak acceleration because the viscous stroking load generated by the MREA force increases with velocity squared, thereby reducing its controllable range at high piston velocity. Therefore, MREA behavior at high piston velocity is analyzed and validated experimentally in order to investigate the effects of velocity and magnetic field on MREA performance. The analysis used to predict the MREA force as a function of piston velocity squared and applied field is presented. A conical fairing is mounted to the piston head of the MREA in order reduce predicted inlet flow loss by 9% at nominal velocity of 8 m/s, which resulted in a viscous force reduction of nominally 4%. The MREA behavior is experimentally measured using a high speed servo-hydraulic testing system for speeds up to 8 m/s. The measured MREA force is used to validate the analysis, which captures the transient force quite accurately, although the peak force is under-predicted at the peak speed of 8 m/s.

Thermal Load Simulation and Structure Improvement of High Speed Diesel Engine Piston

In order to solve cylinder-scraping of a four-cylinder high speed diesel engine, based on the measurement of piston temperature, the piston temperature field was numerically simulated by using temperature fitting method, the calculation results were well consistent with the measured temperature. By finite element analysis of piston thermal load based on the calculation results as temperature load, enlarging oil cooling cavity in the piston head was proposed to enhance cooling locally, which could effectively reduce temperature of the piston head and the first ring groove and avoid the occurrence of cylinder-scraping.

SPECIES TRANSPORT IN DIFFUSER INDUCED CYLINDER

Engines are the devices which can produce a huge amount of energy and can move heavy things such as automobiles and ships. Usually the power which is being produced by a engine varies directly with the amount of fuel combusted in the combustion chamber. Over the years much new technological advancement were made to increase the power output from the engine. This includes the incorporation of systems such as turbochargers, superchargers, ECU’s etc. These devices consume some power to increase the output from the engine. The modification proposed will increase the torque and the power output from the engine without consuming any power. This is achieved by incorporating a diffuser shape in the cylinder block which increases the pressure acting on the piston head thus increasing the engine rating without the help of external devices. In this paper the modified cylinder block has been created using CATIA and then its flow properties are analysed using CFD and the results are compared with a engine having a normal cylinder block .It is seen that the ratings of the modified cylinder are higher than the ratings of the unmodified cylinder.

Numerical investigation of natural gas direct injection properties and mixture formation in a spark ignition engine

In this study, a numerical model has been developed in AVL FIRE software to perform investigation of Direct Natural Gas Injection into the cylinder of Spark Ignition Internal Combustion Engines. In this regard two main parts have been taken into consideration, aiming to convert an MPFI gasoline engine to direct injection NG engine. In the first part of study multi-dimensional numerical simulation of transient injection process, mixing and flow field have been performed via three different validation cases in order to assure the numerical model validity of results. Adaption of such a modeling was found to be a challenging task because of required computational effort and numerical instabilities. In all cases present results were found to have excellent agreement with experimental and numerical results from literature. In the second part, using the moving mesh capability the validated model has been applied to methane Injection into the cylinder of a Direct Injection engine. Five different piston head shapes along with two injector types have been taken into consideration in investigations. A centrally mounted injector location has been adapted to all cases. The effects of injection parameters, combustion chamber geometry, injector type and engine RPM have been studied on mixing of air-fuel inside cylinder. Based on the results, suitable geometrical configuration for a NG DI Engine has been discussed.

2412 CADデータフィッティングメッシュモーフィング技術の開発(OS3 デジタルエンジニアリング)

We developed a mesh morphing technique, which can be used to change the shape of existing analytical mesh models, and generated a mesh model for a new shape by morphing the mesh model for the previous one. Therefore, our method is suitable to use for analysis during the early stage of design because it reduces the amount of time required to generate analytical mesh models. However, this technique is impossible to morph a free-form surface, and to change surface type. Therefore, we developed the fitting morphing technique for solving the problem. This technique is possible to morph based on specification of the STL data as morphed shape and indication of fitting nodes and movable nodes. We confirmed that this technique can be morphed to free-form surface from cylindrical surface by application to the piston head model in 2 seconds. Futhermore, the technique can be morphed to maintain the boundary of the shape by application to the gear model.

Experimental and finite element analysis of a coated diesel engine fueled by cashew nut shell liquid biodiesel

The main purpose of this study is to utilize a low cost feedstock, CNSL (cashew nut shell liquid) as a source for producing biodiesel and operate it in a diesel engine with and without coating. The further scope of the work delineates to conduct a thermal–stress analysis of the coated engine piston so as to understand the physical mechanism underlying the impact of coating on engine performance characteristics. With this intent, in the current work, a different approach to extract CNSL has been adopted and the extracted CNSL was subjected to double stage trans-esterification to synthesize CNSL biodiesel. In face of its insulating properties, PSZ (partially stabilized zirconia), used in high temperature application, has been designated as the perfect coating material to be applied on engine piston, valves and cylinder head by plasma spray coating technique. From the experimental investigation of CNSLME (CNSL biodiesel – 25% and diesel – 75%) in coated engine, it was observed that the BTE (brake thermal efficiency) of the engine was increased by 6%, when compared to uncoated engine. Further, the emissions such as CO (carbon monoxide), HC (hydro carbon) and smoke were reduced by 27.7%, 7.2% and 14.3%, respectively, at full load condition, while NOX (oxides of nitrogen) emission was increased. Finally, from the simulation study using FEA (finite element analysis), the average temperature, heat flux and thermal stress were noted to be lower for coated piston, confirming the substantial improvement in thermal efficiency in the experimental study.

Design of New Ecological Combustion Engine with Double Potential Power Output

Internal combustion engine popularity has been won commercially by the four-stroke type engine surpassing the two-stroke and rotary wankel engines in the world market places. Commercial engines both gasoline and diesel fuels are mostly using the four-stroke principle and even the hybrid cars still rely on this type of engine as their backup source of power. Current research in this areas are optimizing the effectiveness of the four-stroke combustion engine related to fuel consumption, fuel-air mixture, reuse of exhaust energy to feed air inflow, fuel control system to feed exact volume of fuel, exact firing time using intelligent control unit and lower hydrocarbon emissions. However, the development in the engine power output generation is limited due to nearly satisfied expectation of the automotive users caused by limited road development; meanwhile, the short range aerospace engine technology has limited attention in the advanced countries but certainly not in the archipelago country such as Indonesia. This paper is classified to initiates first publication from series of research log book on a new engine design that promotes double power output principle called Double Power Ecological Engine (DPE) for power drive vehicles. The design of DPE engine is located in the firing order, which has direct influence to the new design configuration of crank shaft, air inlet, exhaust and the piston head geometry. The ultimate design of this combustion engine is secured under the firing orders, which are made to secure power output twice as much as it is in the four-stroke engine so that double potential power engine is promoted under ecological fuel ethanol. The design of DPE engine of this research is expected to generate 280 kW power output based on the 1.4 liter engine, which commercially generate around 141 kW. Further research will show the effectiveness of the DPE engine design leading to commercial application.