Valve Seat Research Articles

Experimental investigations into the effects of string cavitation on diesel nozzle internal flow and near field spray dynamics under different injection control strategies

On the test bench of the high-pressure common rail injection system with a high-speed camera, the visualization experiments of real-size tapered hole nozzle of the diesel engine were performed to obtain needle valve lift, string cavitation in the sac chamber and nozzle hole, residual bubbles and near-field spray characteristic. And a high-pressure sensor was utilized to measure the real pressure fluctuation for the nozzle inlet. On the basis, under different control strategies, the comprehensive effects of needle valve throttling and pressure fluctuation for nozzle inlet on the internal flow and near-field spray characteristic under the multiple injections were studied. Research indicated that the spray cone angle and the spray area ratio in the main injection stage shows a boot-shaped increasing trend of slowness and then abruptness. In the development stage, the spray cone angle fluctuates in a little range (20°-30°); In the saturation phase, the spray cone angle fully develops and the fluctuation is relatively stable (40°-50°). As the throttling position shifts, there is an obvious string cavitation process, and the spray cone angle increases suddenly. In the process of pre-injection and post-injection, needle valve and valve seat throttling and lift instability cause fuel pressure fluctuation in the control chamber and sac, which is the main immediate cause of the fluctuation of low fuel injection quantity. Besides, the interval time between multiple injections, on the one hand, affects the state of residual bubbles in the nozzle before the next injection beginning, on the other hand, it also affects the stability of the inlet pressure at this time. The flow transition in the low-lift zone and the cavitation changing in the high-lift stable zone also cause transformation in the form of pressure fluctuation.

Microstructure and properties of CrN coating via multi-arc ion plating on the valve seat material surface

The multi-arc ion plating technology is used to prepare CrN coating on the valve seat material surface. Results show that the surface grains gradually increase in size and becomes less uniform with the increase of the Cr target current. At different Cr target currents, the main phases of the CrN coating are Cr, CrN, and Cr2N. The critical load of the coating and matrix is 49.2 N. When the Cr target current is 65 A, the nano-hardness is maximum (18.84 GPa), and Young ’s modulus is 255.41 GPa. The CrN coating can reduce the friction coefficient of the valve seat material from 0.62 to 0.48, thereby improving the wear-resistance behavior. The main wear mechanism is abrasive wear.

Investigation of the friction-induced vibration of a novel four-way reversing valve using spectral kurtosis and number of peaks spectrum

FWRVs (Four-way reversing valves) are widely used to switch operating conditions in air conditioner systems. Most previous research focused on the efficiency of the FWRVs in heat pump systems. However, the vibrations during the valve reversing processes are not yet well investigated. The friction-induced vibration (FIV) is generated when the slider slides on the valve seat under the high pressure in the valve chamber. In this study, an novel FWRV is proposed to reduce the FIV and improve the fluency during the valve reversing process. The pressure change in the chamber is obtained using CFD (computational fluid dynamics) simulations. Experimental tests are performed to analyze the performance of the novel FWRV. Short-term RMS is employed to evaluate the vibration energy from the measured signal. The FIV acceleration signals generated in FWRV reversing process are periodic impulsive vibrations. A new method named SKNPS (Spectral Kurtosis and Number of Peaks spectrum), which is based on the decomposition criterion of Spectral Kurtosis (SK) and Number of Peaks (NP), is proposed to further analyze the duration of the reversing process. The results indicate that the vibrations of the novel FWRV are reduced and the reversing process is more fluent compared with the prototype valve.

High Performance Valve Seat Materials for CNG Powered Combustion Engines.

The conventional copper infiltrated high speed steel (HSS) valve seats used in gasoline engines are not suitable for CNG combustion because the exhaust gas temperature is at least 80 °C higher, which drastically shortens the service life of the engine valves. Therefore, a proprietary high-alloy HSS-base material was designed to combat hot corrosion and mechanical wear of valve seat faces in CNG fuelled engines. A batch of −100 mesh water atomized HSS powder was commissioned. The powder was vacuum annealed in order to reduce oxygen content and increase its compressibility. To improve the final part machinability, 1.2% MnS was admixed to the HSS powder prior to compaction. The green compacts were sintered at 1135 °C in nitrogen to around 83% TD and subsequently infiltrated with a copper alloy. After installing the valve seat components on a cylinder head, the engine was tested for 100 h according to the automotive industry valve seat wear test procedures. Both the periodic 8-h checks as well as the final examination of the valve seats showed very slow wear, indicating their suitability for CNG powered engines.

Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System

One technique for mitigating disruptions in a tokamak is shattered pellet injection (SPI). SPI is a process in which a large solid pellet consisting of deuterium, neon, or argon is desublimated in a pipe gun barsrel and launched downstream. Pellets are shattered just before entering the plasma by an impact with an angled tube. Injection of these materials into the plasma radiates stored thermal energy, limits current decay rates, suppresses the generation of runaway electrons, and dissipates runaway electrons if necessary. A critical element of the SPI system is a fast-acting valve that releases high-pressure gas to dislodge and accelerate pellets directly, or indirectly via a mechanical punch. A prototype valve sized for the ITER SPI system has been designed and fabricated. A pulsed high-voltage power supply energizes the valve’s internal magnetic coil, which induces eddy currents in the adjacent flyer plate resulting in a repulsive force between the flyer plate and the coil. The flyer plate action lifts a valve seat, allowing high-pressure gas to flow from the valve plenum to the downstream (breech) location of the pellet or mechanical punch. All of the valve’s internal components are designed to operate in ITER-level static background magnetic fields. A study was conducted to optimize the downstream pressure response for a range of valve sizes and operating pressures. In particular, the study analyzes the breech pressure response associated with varying plenum pressures as well as varying breech volumes. A computational fluid dynamics simulation was built in STAR-CCM+ and validated against data from laboratory experiments. The resulting simulation outputs, in the form of downstream responses for a variety of initial plenum pressures and breech volumes, will be used as a complement to experimental data to ensure the pressure pulse is suitable for pellet survivability. These data, combined with studies on pellet shear strength and shock response, will be applied to optimization of overall operating parameters of the ITER SPI system.

Analysis of Instantaneous Collision Process of Axial Flow Check Valve Closing

When the pump stops suddenly, the axial flow check valve will shut down suddenly under the action of the medium pressure differential force, and the impact load between the disc and the valve seat will produce when the valve closes, which will have a certain impact on the structural strength and life of the check valve. In this paper, the display dynamics is used to simulate the impact process of the disc and the valve seat when the valve is completely closed. The dynamic response of the disc and the seat, the velocity of the disc and the energy change during the collision are obtained. The research has certain guiding significance for the practical application of axial flow check valve.

Cavitating flows of organic fluid with thermodynamic effect in a diaphragm pump for organic Rankine cycle systems

Diaphragm pumps often experience cavitation and subsequent fluid flow oscillation when delivering an organic fluid in small/micro scale organic Rankine cycle (ORC). The cavitation behaviour of diaphragm pumps has rarely been investigated for organic fluids so far. Three-dimensional, unsteady cavitating flows of organic fluid R245fa in a diaphragm pump were simulated with ANSYS 2019R2 CFX in suction stroke in terms of the k -ω turbulence model, the ZGB cavitation model, rigid body motion model for one-dimensional motion of valve and moving mesh technique for the first time. The thermodynamic effect in cavitation of R245fa was considered. The vapour volume fraction threshold for cavitation inception was determined, and the cavitation inception and cavitation developed states were identified, and vortex production and entropy generation rate during cavitation were clarified. Cavitation inception emerges at the edge of the valve seat, then on the valve surface. With cavitating development, the pressure and force on the valve, valve opening, and velocity oscillate violently due to vapour bubble collapse cycles. Expansion cavitation and flow induced cavitation happen in sequence at different crank rotational angles. The maximum temperature depression is 0.549 K in the cases studied. The volume-integrated entropy generation rate in the valve chamber correlates to cavitation states.

Influence of Sulfur and Additives on Wear of Exhaust Valve Seat of Cylinder Head

In this paper, taking a certain type of high-power diesel engine exhaust valve abnormal wear phenomenon as an example, we conduct research on the exhaust valve surface micromorphology characteristics, contact surface accumulation products, additive transition layer, and combustion test. These passed diesel sulfur content comparative test, diesel additive composition analysis, and high-sulfur-content and low-sulfur-content diesel and diesel oil additive action test. At present, there is no authoritative research on the influence of sulfur content in diesel on valve seat wear of high-power diesel engines, and the protection mechanism of diesel additives on the valve seat is not clear. The sulfur in diesel, like the lead in gasoline, has long been known to resist wear in the valve seats of high-power diesel engines; just as gasoline additives compensate for the loss of lead, diesel oil additives seem to compensate for the loss of sulfur. Tests show that a uniform carbon deposition layer is formed on the contact surface after the diesel is burned, and the carbon deposition layer is more densely and uniformly adsorbed on the contact surface under the action of diesel additives to form an antiwear layer. Tests also show that the sulfur in diesel has no effect on the wear resistance of the valve seat.

Numerical Study on the Closing Characteristics of a Check Valve with Built-in Damping System

When check valve works in long distance or high lift liquid pipeline system, it is often subjected to water hammer. In this study, the UDF program was used to simulate the closing process of an axial flow check valve at the moment of pump shutdown, and the porous media model was applied to simulate the complete closing of the valve disc. It was found that there was local vacuum at the end of the valve disc at the moment when the valve was completely closed. The water hammer and characteristics of the force acting on the valve disc in the whole closing process were also obtained. In order to reduce the pressure surges on the valve disc and seat, a built-in critical damping was designed and added to the to the valve disc drive system. Since the spring force is directly proportional to the movement displacement of the valve disc, the elastic force and the speed of the valve disc reach the peak value when the valve is fully closed, while the damping force is directly proportional to the speed of the valve disc, therefore, the damping force increases gradually with the speed of the valve disc, which only produces the maximum damping force at the moment of fully closing, so as to reduce the slam shut, but has little effect on the closing time, thus adding damping is more effective than reducing the elastic force of spring. The current study provides a possible approach to protect the valve disc and seat of check valves in liquid supply and drainage systems.

Failure Mechanism and Optimization of Throttle Valve Based on Computational Fluid Dynamics

Throttle valve is an important device in well control manifold. In the process of field use, the valve seat and plug of the valve often have corrosion failure, which brings serious potential safety hazards to the well control work. Using the three-dimensional flow field analysis software of computational fluid dynamics (CFD), it is found that the velocity on the left wall is greater than that on the right. The field failure investigation also proved that the erosion damage mainly occurred on the left wall of the throttle valve, which verified the failure causes of the throttle valve core and valve seat. In addition, the flow field of the erosion resistance device is numerically simulated. The results show that under the given boundary conditions, when the fluid passes through the inlet and outlet of the erosion resistance device, the average velocity changes little. It is known from the velocity curve that under a certain flow rate, the smaller the overflow area is, the greater the velocity is, which is consistent with the hydrodynamic control equation. From the velocity curve data on the alloy head, it is found that the velocity changes little and tends to be horizontal, and the surface velocity of the alloy head is relatively flat, which shows that the fluid velocity on the wall can be effectively reduced after adding the stab prevention short section, so as to reduce the erosion on the wall.

МЕХАНИЧЕСКИЕ И ТРИБОЛОГИЧЕСКИЕ СВОЙСТВА ЗАЩИТНО-ВОССТАНОВИТЕЛЬНЫХ ПОКРЫТИЙ РАБОЧЕЙ ФАСКИ КЛАПАНОВ ДВИГАТЕЛЕЙ ВНУТРЕННЕГО СГОРАНИЯ

Over the past 7-10 years, there has been a steady increase in the cost of gasoline and gas fuel. This circumstance forces the enterprises operating automotive equipment to switch to the use of gas-powered fuel. (Research purpose) The research purpose is in creating a protective and recovering coating that can withstand the wear of the working chamfer of the valve caused by high operating temperatures, dry friction in the valve–seat interface, as well as high flow rates of exhaust gas. (Materials and methods) The article presents an analysis of a priori information, which resulted in the following powder compositions: Ni- ZrO2-SiC; Ni–B4C–BN–ZrO2; Ni–B4C–ZrO2–MgO; Ni-B4C. The samples were subjected to tests on the SMT 2070 friction machine under boundary friction conditions to determine the tribological parameters of coatings made of these materials. The parameters of the friction moment and the coefficient of friction were taken during the tests, depending on the applied load on the tribo-coupling. (Results and discussion) At the first stage of the research, the microhardness of the coatings was analyzed. Tribological studies were performed depending on the microhardness of the coatings. Along with the economic effect, there are negative factors that affect the performance of the valve-seat coupling: increased temperatures up to 750-800 degrees Celsius, the transition to dry friction, high exhaust rates of combustion products (over 1000 meters per second). The best value of the coefficient of friction obtained during the tests belongs to the composition Ni–ZrO2–SiC, which takes values below 0.1. (Conclusions) The use of standard and well-known methods of protecting the working chamfer of the valve in this case is ineffective, since it does not provide the required operating conditions. The article recommens the use of Ni-ZrO2-SiC as the material of the protective and restorative coating of the working chamfer of the valve.

WITHDRAWN: Microstructure and Properties of CrN Coating via Multi-arc Ion Plating on Valve Seat Material Surface

WITHDRAWN: Microstructure and Properties of CrN Coating via Multi-arc Ion Plating on Valve Seat Material Surface

Geometry of Ball Seat Valves

The macroscopic geometry of ball seat valves is important for the quality of the seal. This works discusses the influence of different geometric properties on the contact area, the contact pressure and their relation to the leakage. The leakage is calculated using the results of finite element method (FEM) calculations and Persson’s percolation based method. The following properties of the seat are examined: the angle, the curvature and the eccentricity.

Data Assimilation of Steam Flow Through a Control Valve Using Ensemble Kalman Filter

Abstract The present work concentrates on the simulation enhancement of steam flow through a control valve using the data assimilation (DA) approach based on ensemble Kalman filter (EnKF). The k-ω shear stress transport (SST) model is used as the predictive model in which the model constants are optimized by DA. The selected measurement data at different operating conditions are used as observation, while the rest data are involved for validation. Before DA, four flow patterns which arise on their respective operating conditions are identified and analyzed to illustrate the basic characteristics of flow in the control valve. Then DA is performed based on the sample computation by perturbing the model constants and the EnKF process to determine the optimal model constants. These optimized constants are subsequently used for the precomputation of the valve flow with significant improvement on the flow rate prediction. The velocity and turbulent kinetic energy fields with default and DA-optimized model constants are also compared. The results show that the DA enhanced model constants can significantly reduce the predicted volume flow rate error at all opening ratios presently concerned. With the optimized model constants, the velocity and turbulent kinetic energy distributions are greatly modified in the valve seat between main valve and control valve.

Fracture Analysis for the Vavle disc of Nickel Based Superalloy prepared by Hot Isostatic Pressing

The technology of hot isostatic pressing is combined with the mould control technology under high temperature and high pressure, which can make the powder material quickly and completely shape the complex parts of the forging parts. At the same time, the controllable loading temperature and pressure can be used to realize the preparation and regulation of the material. HIP technology has been widely used in nickel-based alloy valve spheres, valve seats, valve discs and so on. The reasons leading to fracture for the globe valve disc of nickel based superalloy prepared by HIP was analyzed by means of morphology analysis, mechanical properties test, hardness test, metallographic test and other detection means. The results show that there are more black massive carbides, original powder outlines, residual dendrite structure can be seen in the base body structure, and resulting in greater brittleness and poor impact resistance, the fracture failure first occurs under the action of several impact forces generated by the valve action, which in turn causes the sealing gap between the valve disc and the valve seat to change, resulting in the drainage of water from the high pressure side through the gap to the low pressure side, and the gap on both sides metal constitutes erosion.

빗물펌프장의 수력학적 과도현상에 관한 연구

In this study, a field test was conducted to study the water hammer, which is a hydraulic transient phenomenon occuring at a rainwater pumping station. The drainage pump subject to the field test was a vertical shaft two floor mixed flow pump with a pump bore of 2,000 mm and a motor power of 1,320 kW. To test the hydraulic transients phenomenon of the drainage pump, the pressure sensors were installed on the pump discharge side and the outlet of the check valve. In the electrical transient test, the voltage, current, and the power facter of the motor were measured using a power meter. The measured pressure and electrical values were stored in a data acquisition system. A field test for water hammer phenomenon that occur when starting and stopping the drainage pump were conducted in cases where the electric butterfly valve was throttled and when it was full open. As a result of the field test, it was analyzied that the method of cutting off the power of the drainage pump after significantly throttling the electric butterfly valve can reduce the flow velocity in the discharge pipe, but the effect of increasing the pressure of the drainage pump appeared greater. It was observed that the flap valve closed before the check valve when the power to the drainage pump was shut off, and when the flap valve closed abruptly 1 second before and after, slamming occurred. This may cause the valve disk and the valve seat to be damaged by the impact, therefore, caution is required.

Investigation on Dynamic Characteristics of the Reed Valve in Compressors Based on Fluid-Structure Interaction Method

The flow in the gap between the reed and the valve seat has a significant influence on the dynamic characteristics of the reed valve used in reciprocating compressors. The fluid–structure interaction (FSI) method is an effective method for studying reciprocating compressors. A three-dimensional FSI model of a reciprocating compressor with a reed valve is established in this paper, which has an important influence on the flow rate characteristic of reciprocating compressors. Furthermore, an experimental investigation is implemented to verify the FSI model. Based on the established FSI model, the pressure distribution on the reed valve surface is identified by varying the height of the suction valve limiter and the rotational speed of the compressor, which has an important effect on the dynamic characteristics of the reed valve. Although the low-pressure region, due to the Bernoulli effect on the surface of the reed, hinders the rapid opening of the valve to some extent, it is obviously beneficial to the timely closure of the valve and increases the volumetric efficiency of the compressor. Moreover, the optimal height of the valve limiter and the appropriate rotational speed of the compressor are obtained.

Failure analysis of the blackwater regulating valve in the coal chemical industry

Valves’ failure is common in the coal industry due to their severe working conditions, like high-velocity erosion, cavitation erosion, and so on. The damage morphologies of the blackwater regulating valve (BRV) in coal chemical equipment were investigated by stereo microscopy, metallographic microscopy, and scanning electron microscopy (SEM). Failure causes of the valve were analyzed from the material structure, hole defects, composition, hardness of the material, corrosive media, and computational fluid dynamics (CFD). The results showed the damage on the valve spool and seat was attributed to the combined effect of slurry erosion, cavitation erosion, and corrosion. The soft cobalt phase was preferentially removed followed by the pulling-off of WC particles, which is the failure mechanism of BRV.

Numerical Analysis of the energy loss mechanism in cavitation flow of a control valve

Cavitation can cause considerable damage within control valves and nearby pipelines. Despite the extensive research, the mechanism of energy loss in cavitation flow of control valves is not yet adequately understood. In this study, the mechanism of mechanical energy transfer and loss in unsteady cavitation flow and the effect of cavitation on energy loss of a control valve with different pressure ratio conditions were numerically investigated by the validated numerical method based on the LES model. A dimensionless parameter called flow energy gradient was proposed to evaluate the rate of energy loss. Results show that the contribution of the energy loss is much greater in the region of valve seat throat where strong throttling and severe cavitation occur. The total energy loss in the control valve is composed by the throttling loss and the additional energy loss of cavitation, the latter leads to an increase in flow resistance and a decrease in flow capacity of the control valve. Moreover, the additional energy loss induced by cavitation increases with the severity of cavitation, which may result from the change of the liquid-vapor phase.

Mathematical Modelling and Dynamic Analysis of a Direct-Acting Relief Valve Based on Fluid-Structure Coupling Analysis

To explain the sudden jump of pressure as the variation of water depth for a direct-acting relief valve used by torpedo pump as the variation of water depth, a 2-DOF fluid-structure coupling dynamic model is developed. A nonlinear differential pressure model at valve port is applied to model the axial vibration of fluid, and a nonlinear wake oscillator model is used to excite the valve element in the vertical direction; meanwhile, the contact nonlinearity between the valve element and valve seat is also taken into consideration. Based on the developed dynamical model, the water depths for the sudden jumps of pressure can be located precisely when compared with the experimental signals, and the corresponding vibration conditions of the valve element in both the axial and vertical directions are explored. Subsequently, in order to eliminate the sudden jumps of pressure, different pump inlet pressure was tested experimentally; when it was decreased to 0.4 MPa, the pressure jumps ever appeared during the dropping and lifting processes were removed, and the numerical simulation based on the developed mathematical model also verified the experimental measurements.