Poppet Valve Research Articles

Simulation and experimental investigation of swirl-loop scavenging in two-stroke diesel engine with two poppet valves

Scavenging is becoming one of the determinants of two-stroke engine performance. Efficiency of U-type loop scavenging of two-stroke diesel engine with two poppet valves is generally unsatisfactory due to scavenging short-circuiting and large amount of residual burned gas in cylinder, and it is hard to generate the swirl that facilitates fuel spray mixing and combustion. In order to deal with the above issues, a swirl-loop scavenging configuration is proposed to involve swirl and depress short-circuiting. To investigate swirl-loop scavenging performance, this article simulates the scavenging process by numerical method, optimizes the tracer gas method to measure and evaluate the scavenging performance, as well as analyzes the influence factors. The results demonstrate that, compared with U-type loop scavenging, the trapping efficiency and scavenging efficiency of swirl-loop scavenging respectively increase by 8% and 10%. Change of engine speed has an impact on the delivery ratio and trapping efficiency but load does not. Both intake and exhaust valve timings affect scavenging performance and short-circuiting to a large extent. In addition, the accuracy of tracer gas method in measurement of scavenging performance parameters is improved, and the scavenging efficiency deviation between simulation and experiment is decreased from 6% to 2%.

Investigation on the modeling and dynamic characteristics of a fast-response and large-flow water hydraulic proportional cartridge valve

In large-power and high-pressure hydraulic systems, the maximum instantaneous flow rate is often several thousand liters per minute. Normal proportional valves are often difficult to meet their requirements for large flow rate and fast response at the same time. And the leakage of hydraulic oil will seriously pollute the environment. Therefore, a novel water hydraulic proportional valve with fast response and high flow capacity is presented for the large transient power hydraulic system in this paper. The valve utilizes a two-stage structure with two 2/2-way water hydraulic proportional valves as the pilot stage and a cartridge poppet valve as the main stage to achieve fast-response and large-flow capacity simultaneously. A detailed and precise nonlinear mathematical model of the valve considering both structural parameters and flow force is developed. A comprehensive performance optimization has been carried out, which can be mainly divided into computational fluid dynamics simulation optimization based on reducing flow force and multi-objective optimization based on genetic algorithm. The effects of double U-grooves' parameters on the flow force (flow-induced loads) have been studied in detail by numerical simulation. Through the grooves geometry optimization, the maximum flow force can be reduced by 10%. Then, the influences of structure parameters on the performance of step response have been studied, and the optimal parameters of the valve have been obtained by multi-objective optimization based on genetic algorithm. The maximum overshoot has been reduced from 15% to 6% (about 60%) and the adjusting time has been reduced from 58 ms to 48 ms. The dynamic characteristics of the valve have been improved effectively. Finally, a test apparatus which has the ability to provide transient large flow is built. The accuracy of simulation model and optimization design method is verified by test results.

Information and energy approach to solving problems of hydrodynamics and mechatronics in energy transfer processes

Abstract. The article considers the approach of the physical aspects of transfer processes. From the angle of the main postulate of thermodynamics - the conversion of thermal energy into mechanical work and vice versa, the energy balance in a poppet valve was considered. A diagram of the interaction of the system through the process of transfer, operation, and an analogy between a poppet hydraulic valve and an electric transistor is illustrated. It is shown that heat is one form of energy that can be converted into other forms. As a result of numerical and physical visualization, it has been established that when the fluid moves in a poppet valve, various physical transfer processes occur. For example, cavitation, in which there is a significant change in the energy balance and energy dissipation under non-stationary modes of fluid motion. As a first approximation, an attempt is made to connect the equations of the transport phenomenon with information transfer through an energy gradient.The given information-energy approach and algorithm are acceptable for formulating and solving problems on non-idealized mechanical and hydromechanical systems that are in dissipative processes. The article describes the principles that can be used to design apparatuses and modules of mechatronic systems.

Increasing the Performance of Existing IC Engines by Free Valve Actuation Technology

In this current generation, the efficiency of gasoline engines is around 50%. This isbecause of many losses within the system. The most important losses are because of moving parts. Moving parts comprises piston, cams, rod etc. Investigations are being conducted to cut the losses to enhance efficiency. One such outcome is that the free Valve Mechanism which uses poppet valves operated by means of pneumatic actuators rather than cams. Actuators are used to open and shut the valves and control combustion within each cylinder and hence improving the efficiency.

Visual experimental investigation on the stability of pressure regulating poppet valve

The unstable vibration of a poppet valve drastically fluctuates pressure which directly affects the stability, reliability and safety of a hydraulic system. The unstable vibration of the poppet and cavitation is studied using visual experiments. Experimental results show that for a poppet valve, an orifice at the front of the valve cavity, the compressibility of oil in the sensitive cavity will lead poppet to unstable vibrations. For poppet valve without orifice, the instable vibration appears as three states: impact valve seat, transition (impact or non-impact valve seat occurs randomly) and does not impact valve seat. When poppet impacts valve seat, there will be severe cavitation phenomenon at the valve port. Although poppet does not impact valve seat, the cavitation come up is affected by the pressure difference at the port or vibration amplitude of the poppet. In addition, both of the flow pulsation of the hydraulic pump and the coupling between the poppet and pipeline system will lead the poppet to be unstable.

Comparative study on the improvement of the gas exchange process efficiency of a high speed IC engine using swinging valve

Using poppet valves to control the air-fuel mixture entering and leaving the combustion chamber of an engine is just one among many other more flow efficient alternative solution. The geometry of the poppet valve and its valve seat are the main causes of the flow restriction in the internal combustion engines. The engine downsizing concept dictates to obtain more power from a given engine volume, therefore proportionally more air should be drawn into the cylinders to burn more fuel. These criteria best fulfilled with a new Swinging Valve (SwV) solution that enables the unhindered flow of air and exhaust gas through an engine’s cylinder. The filling of a cylinder is improved while the pumping losses are decreased. In this experiment, a Super Flow SF600 flow bench was used to examine a Suzuki SV650 motorcycle engine’s normal poppet valve cylinder head and a Swinging Valve cylinder head was constructed as well. First the flow parameters of the original cylinder head were obtained then the Swinging Valve head was investigated in the same way. The outcomes of the tests show the superiority of the new concept. The results will also be the base of further 0D/1D engine simulations.

Alternative mechanical heart valves for the developing world.

Due to the prevalence of rheumatic heart disease in the developing world, mechanical heart valves in the younger patient population remain the prostheses of choice if repair is not feasible. Despite their durability, mechanical valves are burdened by coagulation and thromboembolism. Modern design tools can be utilized during the design process of mechanical valves, which allow a more systematic design approach and more detailed analysis of the blood flow through and around valves. These tools include computer-aided design, manufacturing, and engineering, such as computational fluid dynamics and finite element analysis, modern manufacturing techniques such as additive manufacturing, and sophisticated in-vitro and in-vivo tests. Following this systematic approach, a poppet valve was redesigned and the results demonstrate the benefits of the method. More organized flow patterns and fewer complex fluid structures were observed. The alternative trileaflet valve design has also been identified as a potential solution and, if a similar design approach is adopted, it could lead to the development of an improved mechanical heart valve in the future. It is imperative that researchers in developing countries continue their search for a mechanical heart valve with a reduced thromboembolic risk, requiring less or no anticoagulation.

Simulation of Composite Titanium Nitrite (TiN) Coated Internal Combustion Engine Exhaust Valve using ANSYS

In Internal Combustion Engine, valves play a crucial role in the circulation of intake and exhaust gases. Although inlet valve is exposed to higher temperatures during combustion, its failure rate is less when compared with exhaust valve. This is because the inlet valve is cooled by fresh charge admitting into the cylinder. But exhaust valve is heated up by the enormous heat carrying flue gases. Hence it is more prone to failure and has become the focus of study. The exhaust valve undergoes mechanical and thermal loads when gases are circulated from the cylinder. The valve is exposed to these extreme high temperatures subjected to fatigue loads which cause failure of valve. The valves should possess good material properties at high temperatures i.e., higher hardness, hot hardness, higher thermal conductivities and high strength properties. It has been observed that the exhaust valve performance can be appreciably enhanced by using thin film Titanium coatings like Titanium Nitride (TiN), Titanium Carbide (TiC), Titanium Nitride (TiCN) based Titanium coatings. The Titanium based thin film coatings have high corrosion resistance, less wear rates due to cyclic loads, and higher thermal resistance. In the present work, the valve coated with TiN and uncoated IC engine exhaust valves, here poppet valve of four stroke two wheeler engine valve is chosen and simulated under both high temperature loads and mechanical loads using finite element analysis(FEA). The simulated results obtained are then compared for both coated TiN and uncoated valve. It indicates that the Titanium Nitrate (TiN) coated valve has low thermal resistance and less thermal and mechanical failure than uncoated valve. FEA simulated results of TiN coating on the valve and uncoated exhaust valves are analyzed and presented in the research article.

Assortment analysis of shutter valves for spark ignition engines timing systems

Continually tightened emission restrictions together with limited crude oil resources are factors driving more efficient fuel management strategies implementation. Such operations results in increase of internal combustion engine efficiency due to change in geometry and materials of existing systems as well as introducing new solutions. Over the years many approaches were taken. One of them was timing valve geometry optimization, which in case of conventional poppet valves is burden with number of restrictions. At this place some nonconventional designs might be introduced and one of them is so called shutter valve. Construction of shutter valve finds its roots in photographic industry where it is commonly used for exposition of photosensitive material for exactly determined period, enforcing very fast operation of mechanism similar like in case of valve train, which makes it suitable to adapt in engine timing system.

Dynamic modeling of a cabin pressure control system

Cabin pressure control system of an aircraft maintains cabin pressure in all flight modes as per the aircraft cabin pressurization characteristics by controlling the air flow from the cabin through the outflow valve of the cabin pressure control valve. The movement of outflow valve in turn depends on the air flow from the control chamber of cabin pressure control valve, which is controlled by the clapper and the poppet valves. These valves are actuated by absolute pressure and the differential pressure capsules, respectively depending upon the operating flight conditions. Mathematical models have been developed to simulate the air outflow rates from the cabin and the control chamber of cabin pressure control valve during steady-state and transient flight conditions. These mathematical models have then been translated into a MATLAB program to obtain plots of cabin pressures as a function of aircraft altitudes. The mathematical models are validated for standard cabin pressurization characteristics of a multirole light fighter/trainer aircraft. The model developed, thus can be used to produce a number of variants of cabin pressure control valve to suit different cabin pressurization characteristics.

Position Control of Pneumatic Actuators Using Three-Mode Discrete-Valued Model Predictive Control

A novel discrete-valued model-predictive control (DVMPC) algorithm termed DVMPC2 for the position control of pneumatic actuators using inexpensive on/off valves is presented. DVMPC2 includes a more flexible cost function, an improved prediction strategy, and other improvements. The actuator is a double-acting cylinder with two on/off solenoid poppet valves connected to each chamber. To reduce the switching frequency and prolong the valve life, DVMPC2 directly switches the valves when necessary, instead of using relatively high-frequency pulse-width modulation. Experimental comparisons are made with the state-of-the-art sliding-mode control (SMC) algorithm and the previous DVMPC algorithm. The comparisons are based on the five performance metrics: integral of time-weighted absolute error (ITAE), root mean square error (RMSE), overshoot (OS), steady-state error (SSE), and valve switches per second (SPS). The robustness is evaluated by increasing and decreasing the total mass of the moving components while keeping the controller parameters constant. The experimental results show that the proposed algorithm is superior to the previous DVMPC and outperformed SMC by a wide margin. Specifically, DVMPC2 reduced ITAE by 80%, RMSE by 52%, OS by 43%, and SPS by 20% relative to SMC. There was no clear winner in terms of SSE.

Numerical investigation on cavitating jet inside a poppet valve with special emphasis on cavitation-vortex interaction

A thorough understanding of the internal flow dynamics inside a poppet valve makes sense for an improved control performance. Hence, a numerical simulation for the cavitating jet is performed with main concern on the cavitation-vortex interaction. The periodic cavitation structure, along with corresponding variation in vorticity distribution and large scale eddy, is presented for the quasi-steady flow from numerical results. As expected, cavitation inception exhibits great dependence on coherent structure, which is organized as paired vortex rings. Besides, cavitation is persistently located at core of vortex, indicating strong correlation between cavitation and vortex dynamics. The cavitation-vortex correlation is further discussed with analysis of vorticity transport equation, involving vortex stretching, dilatation and baroclinic torque terms. At incepting stage, vortex stretching is the dominant factor, responsible for vortex growth and the elliptical shape of cavitation ring. In comparison, the dilatation term could produce either enhancement or suppression in local vorticity, depending on the volumetric variation induced by cavitation. During the collapse stage, the bubble collapse creates baroclinic vorticity, and contributes to 3-dimensional vorticity. The most significant finding of the present study is the suppression of vorticity during the growing process of cavitation, contributing to an enhanced understanding of the cavitation-vortex interaction.

Experimental Comparison of Gasoline Compression Ignition and Diesel Combustion in a Medium-Duty Opposed-Piston Engine

The Achates Power Inc. (API) opposed-piston (OP) engine architecture provides fundamental advantages that increase thermal efficiency over current poppet valve 4 stroke engines. In this paper, the combustion performance of diesel and gasoline compression ignition (GCI) combustion in a medium-duty, OP engine are shown. By using GCI, NOx and/or soot reductions can be seen compared with diesel combustion at similar or increased thermal efficiencies. The results also show that high combustion efficiency can be achieved with GCI combustion with acceptable noise and stability over the same load range as diesel combustion in an OP engine.

Novel Design and Modeling of Shutter Valves for Camless Engines

For the intake of air fuel mixture and exhaust of gases camshaft operated valves are mounted on the cylinder head. In this paper, we have proposed a novel physical model of a shutter valve to replace the traditional camshaft operated valve resulting in a camless four–stroke engine. The lift control for the opening and closing of the intake and exhaust valves are monitored traditionally by a camshaft which is a mechanical component having a fixed shape. A camless engine replaces the camshaft by allowing the control of valves through the Electronic Control Unit (ECU). The already developed valves have limitations in terms of lift, life expectancy or higher costs. This research work proposes a novel shutter valve design instead of a poppet valve for intake and exhaust of four– stroke engines. These valves are then operated directly by an ECU and controlled through pulse width modulation. The proposed variation in shutter valve design optimally adjusts and controls the fuel intake amount and the flow of exhaust gases in and out of the cylinder respectively. The opening of the valve can be set to maximum or at the desired angle so that the engine can run according to the driver’s requirement. The novel design of the shutter valve will reduce the engine cost and will improve the fuel economy. At the same time, providing complete control to the driver’s performance preferences.

Analysis of the Design of a Poppet Valve by Transitory Simulation

This article contains the results and analysis of the dynamic behavior of a poppet valve through CFD simulation. A computational model based on the finite volume method was developed to characterize the flow at the interior of the valve while it is moving. The model was validated using published data from the valve manufacturer. This data was in accordance with the experimental model. The model was used to predict the behavior of the device as it is operated at high frequencies. Non-dimensional parameters for generalizing and analyzing the effects of the properties of the fluid were used. It was found that it is possible to enhance the dynamic behavior of the valve by altering the viscosity of the working fluid. Finally, using the generated model, the influence of the angle of the poppet was analyzed. It was found that angle has a minimal effect on pressure. However, flow forces increase as angle decreases. Therefore, reducing poppet angle is undesirable because it increases power requirements for valve actuation.

Dynamic Characteristics and Stability Analysis of Conical Relief Valve

The overflow rate of poppet relief valve is established, the dynamics characteristics of poppet relief valve which contains transient flow force and steady flow force is established. Based on this point, the stability conditions of poppet relief valve system are derived using Routh-Hurmitz method. The effect of the design parameters of relief valve on the dynamic characteristics of poppet valve system is analyzed. Using sensitivity analysis, the effects of parameters of the most significant is obtained, that is diameter D of liquid flow cylinder fluid. The results showed that, the established model can largely capture the dynamic characteristics of the relief valve system, the established stability condition can be used as a favorable basis for the design of valve. DOI: http://dx.doi.org/10.5755/j01.mech.25.1.22881

Experimental investigation of the air–fuel charging process in a four-valve supercharged two-stroke cycle GDI engine

Fuel consumption standards imposed in several countries for the next years have prompted the development of hybrid passenger cars with ever smaller internal combustion engines. In such powertrain, fuel consumption is as important as engine packaging and power density, so two-stroke engines may be an option due to their higher combustion frequency compared to four-stroke engines. Therefore, the present research investigates the air–fuel charging process of an overhead four-valve direct injection supercharged engine operating in the two-stroke cycle. The optimum start of fuel injection was evaluated for commercial gasoline by means of indicated and combustion efficiencies where a trade-off was found between early and late fuel injections. By advancing the injection timing, more fuel was prone to short circuit to the exhaust during the valve overlap, while late injections resulted in poor charge preparation. The gas exchange parameters, i.e. charging and trapping efficiencies, were obtained from seventy operating points running at fuel-rich conditions. The Benson–Brandham mixing-displacement scavenging model was then fit to the experimental data with a coefficient of determination better than 0.95. With such model, the air trapping and charging efficiencies could be estimated solely based on the scavenge ratio and exhaust lambda, regardless of the engine load, speed, or air/fuel ratio employed. Further twenty-five different lean-burn testing points were tested to certify the proposed methodology applied to the poppet valve two-stroke engine. The in-cylinder lambda was calculated and found different from the exhaust lambda due to mixing between burned gases and intake air during the scavenging process.

A Numerical Study on Jet Structure and Noise Emission of Underexpanded Radial Jet

In this study, an underexpanded radial jet issuing from a small gap between two circular tubes facing each other is investigated numerically. Radial jet is formed, for example, downstream of high-pressure valves in piping system and of poppet valves in engines, and causes many industrial problems such as the noise generation and the fatigue failure of structure. In this study, the jet issuing from a small gap between two tubes with same diameter is numerically simulated. The flow field is assumed to be axisymmetric against the central axis of tubes and to be symmetric against the intermediate plane between the exits of two tubes. The axisymmetric Euler equations are solved using symmetric TVD (Total Variation Diminishing) scheme. The effects of nozzle pressure ratio and of diameter of circular tubes on the structure and the behavior of jets are examined. Typical cell structure of underexpanded jet appears in radial jet and the length of cell becomes smaller in downstream region because the jet spreads radially like a disc. The length and width of first cell are larger with higher nozzle pressure ratio. Many vortices are generated one after another near the jet boundary and move downstream, which cause the oscillation of jet. Outside of jet, two types of density waves are observed. One of them propagates toward the nozzle (toward the upstream region) and the other propagates in opposite direction. Focusing on the pressure change caused by the former waves, which is related to well-known screech, dominant frequency obtained by FFT analysis was found to become lower with higher pressure ratio and smaller diameter of tube.

Stepping Valve Actuator Algorithm for a Camless IC Engine

Abstract Camless Engines offer many advantages over poppet valve systems. However, they suffer from air/hydraulic leakages and piston-valve interactions. In addressing the situation, the stepping valve rotates perpendicularly to the piston motion with no interactions. In this case, the valve events will be flexible enough to allow engine cranking without the mechanical starter. For this study, a 3-phase, 12-coil Stator rated at 3Amp 12V DC and a Stepping Valve were used. To avoid friction against its seat, the Stepping Valve is lifted up by 1mm in 2mS. Then it steps to a new Valve State Position in 2mS before gently landing back on its seat in 4mS. The Valve Event Algorithm has been designed, simulated and successfully programmed onto an Altera Programmable Device using Max Plus II Design Environment. The overall aim of this study is to have the three components required for ignition: fuel, spark and air, entirely controlled in software to maintain engine efficiency for the entire RPM range.

Coherent structure of paired vortex and transition in flow pattern in cavitating jet through a poppet valve

A combined experimental and numerical method is performed in order to investigate the flow pattern for cavitating jet through a poppet valve. Results show that coherent structure, which is organized as paired vortex structure, is widely involved in internal dynamics of the investigated jet flow. Its formation is governed by a similar mechanism, whereas its subsequent evolution shows variation close correlated to flow pattern. Generally, transition of coherent structure leads to noticeable alteration in flow pattern. In the present case, however, it is the subsequent evolution of coherent structure that plays a determinant role for flow pattern. For low pressure drop below 25 bar in poppet valve of 0.7 mm openness, coherent structure experiences a gradual collapse, and the laminar potential core is persistent along poppet surface. For moderate pressure drop, coherent structure undergoes a progressive intensification, and the laminar flow becomes partly disturbed as a waving pattern in the wake or a further periodic cavitating pattern. With pressure drop over 36 bar, vortex evolves fast into a cavitating bubble cluster, which involves strong interaction between coherent structures. Consequently, potential core experiences a sudden and aggressive fragmentation. In addition, three kinds of vortex pairing process are captured, which are demonstrated highly involved in evolution of coherent structure and at the same time exhibit some distinctive features from conventional paring process. Furthermore, the transition in flow pattern reveals and explains the piecewise flow-rate performance.