Double Nozzle Flapper Research Articles

A Numerical Research on Vortex Street Flow Oscillation in the Double Flapper Nozzle Servo Valve

The oscillating flow field of the double nozzle flapper servo valve pre-stage is numerically analyzed through Large Eddy Simulation (LES) turbulent modeling with the previous grid independence verification. The vortex street flow phenomenon can be observed when the flow passes through the nozzle flapper channel, the vortex alternating in each side produces the periodical flow oscillation. The structural and flow parameter effects on the oscillating flow are emphasized, and it could be determined that the pressure on the flapper is nearly proportional to the flow velocity and inversely proportional to the actual distance between the flapper and the nozzle. On the other hand, the main frequency of oscillation decreases with the velocity and increases with the distance between the nozzle flapper. The main stage movement is further considered with a User Defined Function (UDF), and it could be determined that the influences of the structural and flow parameters on the flow oscillation are rarely changed, but the main frequencies drop, generally.

Full simulation of a piezoelectric double nozzle flapper pilot valve coupled with a main stage spool valve

This paper develops a detailed simulation model, realized by the software Simscape, which can be a powerful tool to analyze the performance of a double nozzle flapper valve actuated by a piezoelectric ring bender. The particularity of this valve is that the use of the torque motor and flexure tube is avoided, thus reducing the complexity, manufacturing time and cost of the valve assembly. The model accounts for all the real phenomena present in the valve, such as fluid compressibility and fluid viscosity. The viability of the valve concept is validated by step tests simulated at different valve openings. It is shown that the response time obtained for a supply pressure of 210 bar and necessary to reach 90% of the maximum opening degree (corresponding to a maximum spool position of 1mm and maximum flow rate of 60 l/min) is only 6 ms, which is comparable with typical commercially available double nozzle flapper valves, but with the advantage of having removed critical components such as the torque motor and the flexure tube.

Design criterion involving comprehensive performance characteristics of nozzle–flapper valves

The traditional parameter design rule for the nozzle–flapper valves has always followed the maximum control pressure sensitivity criterion; however, this article queries the validity of this traditional parameter design theory for the comprehensive performance characteristics of a flapper–nozzle valve. Accordingly, a new parameter design rule, which involves symmetry, linearity and sensitivity of the control pressure, was constructed from a detailed and rigorous mathematical derivation that employs a non-dimensional analysis method. Then, an effect verification of the new criterion and a comparison between the pressure–flow curves and three key valve coefficients, which are dominated by the traditional rule and the new criterion, respectively, are performed. Finally, the comprehensive performance characteristics of the flapper–nozzle valve, such as the reliability, response, accuracy, sensitivity, efficiency, anti- disturbance and control pressure range, which are produced by the two parameter design rules, are compared. The results indicate that the performance of nozzle–flapper valve followed by the new parameter design criteria is superior to the performance directed by the traditional one with respect to various indexes, such as the reliability, response, accuracy and anti-disturbance. In addition, for the design of nozzle–flapper valves, the studies have also revealed that the optimal values of the structural parameter are dependent on the actual flapper motion ranges and the priority of the above-mentioned performance indexes. All these new findings can develop and supplement the existing design theory of nozzle–flapper valve and can also be beneficial to the design of double-nozzle–flapper electro-hydraulic servo valves.

Servo Valve Nozzle Fuzzy Clustering Analysis Pairing Algorithm

Electro-hydraulic servo valve is the key component of an electro-hydraulic servo control system, and double nozzle flapper valve is the main type of electro-hydraulic servo valve. Nozzles are the important part of a double nozzle flapper valve, the pairing quality is directly related to the performance of the servo valve .Servo valve is of symmetrical structure, and the use of nozzles is also in pairs. The process of nozzles matched in pairs is called pairing process. Because the orifice diameter of the nozzle is only about 0.2 to 0.3 mm, it is difficult to pair with the method of direct measurements. Besides, as a kind of hydraulic components, nozzles are usually paired by flow rate measured under differential pressure. Two nozzles will be matched to a pair if their pressure-flow rate characteristic curve is within the allowed tolerance. To ensure the success rate of pairing, it usually needs a large number of machined nozzles to be sifted. According to the principle of clustering analysis, we propose a new paring algorithm which can match nozzles efficiently and automatically.

Research of Double Nozzle Flapper Valve Accelerated Degradation Test

This paper selected the double nozzle flapper type electro-hydraulic servo valve as the research object. Through to analys the wear failure mechanism of electro-hydraulic servo valve to determine the test stress and to select the Pressure gain and leakage as the Degradation performance indicators. So it makes the detail Accelerated degradation test project . and it designs a test system for the pollution wear test. Then, by modeling the degradation process as a drift Brown Motion of which the first passage time follow inverse Gaussian distribution, this paper generated the reliability model of the electro-hydraulic servo valve. Finally, the maximum likelihood combined with least square of accelerated degradation testing data is used to estimate the degradation data of leakage from the test.

The Influence of the Damping Hole Parameters on the Performance of Double Nozzle Flapper Valve Basing on the Orthogonal Test

This paper analyses the flow of the double nozzle flapper valve. Three-dimensional model is established with software Pro/E, fluid analysis software is used for modeling and meshing, CFD method is applied for researching pressure, and flow characteristics of the fixed damping hole is researched when parameters of double nozzle flapper valve is varied. The results show that: the highest velocity through the fixed orifice hole is about 150m/s, the pressure is about 5.9MPa; Using orthogonal test to analyze the simulation results, it is obtained that the power losses of the double nozzle flapper with the change of the diameter, length and the angle of the fixed orifice, the influencing factors on the power losses are the diameter, length and the angle, and the best parameter combination through orthogonal table analysis is gained, which can provide the reference for the whole designing of the double nozzle flapper valve.

Design and experiment of novel piezoelectric double nozzle flapper electro-hydraulic servo valve

To improve the performance of the existing nozzle flapper type electro-hydraulic servo valve, a novel piezoelectric double nozzle flapper electro-hydraulic servo valve (PDNFESV) is proposed. An electricity-machine transducer is designed to replace the torque motor in the traditional nozzle flapper servo valve. The electricity-machine transducer is constructed by two identical piezoelectric bimorphs and a beryllium bronze board. The design and fabrication of the electricity-machine transducer is introduced. The structure and work principle of the novel PDNFESV is analysed. The static and dynamic characteristic of the electricity-machine transducer are tested, the experimental results show that the designed electricity-machine transducer can meet the demand of the novel PDNFESV. At last, the performance indexes of the novel PDNFESV are researched.

Influence of Flow Force on the Flapper of a Water Hydraulic Servovalve.

In this paper, flow force due to nozzle flow and its influence on the flapper-nozzle system for water hydraulic servovalves are discussed. The flow force acting on the flapper is estimated using the momentum theory, and expressed as a function of the nozzle pressure and flapper-nozzle gap. Analysis shows that the double nozzle flapper gives a quasi-linear characteristic to the relationship among the force on the flapper, the flapper gap and the spool velocity. The numerical result based on the theory is used to estimate the accuracy of the classical linear approximation. The moment due to the flow force resists input moment acting on the armature. Consequently the flow force reduces the magnitude of the change of the nozzle backpressures that drive the spool of the water hydraulic valve. Experimental verification of the theory is also presented.

Influence of Flow Force on the Flapper of a Water Hydraulic Servovalve.

In this paper flow force due to nozzle flow and its influence on the flapper-nozzle system for water hydraulic servovalves are discussed. The flow force acting on the flapper is estimated using the momentum theory, and expressed as a function of the nozzle pressure and flapper-nozzle gap. Analysis shows that the double nozzle flapper gives a quasilinear characteristic to the relationship between the force on the flapper, the flapper gap and the spool velocity. The numerical result based on the theory is used to estimate accuracy of the classical linear approximation. The flow force reduces the magnitude of the change of the nozzle back pressures which drive the spool of the water hydraulic valve, because the input moment acting on the armature is resisted by the moment due to the flow force. Experimental verification of the theory is also given.