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.

Turbine Dimensionless Coefficients and the Net Head/Flow Rate Characteristic for a Simplified Pico Hydro Power System

The basic operational parameters of a simplified pico-hydropower system with provision for water recycling were investigated. Five simplified turbine of runner diameters 0.45, 0.40, 0.35, 0.30 and 0.25 m were designed, locally fabricated, and tested in conjunction with five PVC pipes of diameters 0.0762, 0.0635, 0.0508, 0.0445 and 0.0381 m as penstocks. Five simple nozzles of area ratios 1.0, 0.8, 0.6, 0.4 and 0.2 were fabricated for each penstock diameter. The turbines were successively mounted at the foot of an overhead reservoir such that the effective vertical height from the outlet of the reservoir to the plane of the turbine shaft was 6.95 m. A 1.11 kW electric pump was used to recycle the water downstream of the turbine back to the overhead reservoir. The mean maximum and minimum rotational speeds of the shaft of each turbine were measured for each penstock diameter and nozzle area ratio, and the volumes of water displaced in the reservoirs were also monitored. These measured data were used to compute shaft power and system volumetric flow rate for each operation. Dimensionless flow, head and power coefficients, and specific speed were computed and functional characteristics relating them developed. This standard procedure generally used for the analysis of geometrically similar hydraulic machines have been applied to this system and the results obtained will be invaluable in development of the system into a simple, environmentally friendly and decentralized small power generation system that could potentially contribute positively to the energy mix in Nigeria. The possibility of scaling the system to accommodate larger turbine and penstock diameters, and as a result higher capacity alternators exist and is a target for future developments.

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.

Computational Fluid Dynamics Investigation of Turbulent Flow Inside a Rotary Double External Gear Pump

This article presents a numerical investigation of 2D turbulent flow within a double external gear pump. The configuration of the inlet and outlet ports is determined such that the double gear pump acts like the combination of two parallel pumps. The complex geometry of the double gear pump, existence of narrow gaps between rotating and stationary walls, and rapidly deforming flow domain make the numerical solution more complicated. In order to solve the mass, momentum, and energy conservation laws along with the k-ε turbulence model, a second-order finite volume method has been used over a dynamically varying unstructured mesh. The numerical results including pressure contours, velocity vectors, flow patterns inside the suction chamber, leakage paths, and time variation of volumetric flow rate are presented in detail. The flow rate characteristic curves with linear behavior are demonstrated at rotational speeds and outlet pressures in the range of 1500–4000 rpm and 2–80 bar, respectively. The effect of reducing the gear-casing gap-size on the augmentation of the net flow rate has been investigated. It is concluded that the minimum oil pressure within the gear pump occurs at the two places between contacting gears near the inlet ports. The contours of vapor volume fraction are also illustrated.

Measure and Study on Heat Balance of Engine

—The main research contents in this paper are as following. Building a test bench for engine heat balance, and completed the test equipment and debug engine. Through test we can obtain the coolant pressure characteristic curve, temperature characteristic curve and flow rate characteristic curve in different working conditions. Researched the engine heat distribution laws and influencing factors based on the engine coolant temperature in the engine full-load characteristic conditions.

Determination of Flow Rate Characteristics for Pneumatic Components During Isothermal Discharge by Integral Algorithm

In this paper, we proposed a method to determine the flow rate characteristic parameters directly by using an integral algorithm which is not needed to calculate the flow rate. In the isothermal discharge method discussed by ISO, the flow rate characteristics of pneumatic components can be obtained by pressure response and flow rate. The pressure response is measured in an isothermal tank and the flow rate can be given by differentiating the measured pressure response. Because of using the differential algorithm, calculation precision for measurement error and distribution is much poorer. By integrating pressure experimental result with least error method, characteristics can be obtained easily with Excel tool. Some experimental results are given to show that the proposed calculation method in this paper is more effective than the conversational method by using pressure sensors with different precision.

Research on Influence of Parameters Variation on the Fixed Orifice Performance of the Servo-Valve

In this paper, The finite element analysis software is applied to compute the flow field in the fixed orifice with different structural parameter combinations, the pressure distribution curve, the velocity distribution curve, flow rate characteristic, power loss are obtained. By analyzing simulation results, the influence of the orifice parameters on the performance of the orifice is clear. The research is important for the design and optimization of the fixed throttle orifice of the nozzle-flapper valve.