Quanke Feng

A Multicolumn Envelope Meshing Pair for Single Screw Compressors

This paper introduces a new meshing pair profile envelope by multicolumn in single screw compressors. The screw groove flank of the new meshing pair is a multisegment surface, and the star-wheel tooth flank consisted of multicylindrical surfaces. When the compressor is operating, the position of the contact line on the tooth flank with the screw groove flank uniformly moves in one revolution, which is rather different from the stationary contact position of existing meshing pair profiles. The new meshing pair will result in the improved wear-resistance and longer operation life, lower gas leakage, and higher efficiency of the compressor.

Prediction of Pressure Pulsation for the Reciprocating Compressor System Using Finite Disturbance Theory

Pressure pulsations in the piping system of the reciprocating compressor produce excessive noise and even lead to damage in piping and machinery. Therefore, it is very important to predict precisely the pressure pulsation with large amplitude in the piping system. In this paper, the finite disturbance theory is used to solve the nonlinear partial differential equations that describe the unsteady one-dimensional compressible flow in the complex piping system. The solution is then compared with experimental results. The comparison shows that the finite theory fits the large pressure disturbance more precisely than the acoustic theory.

Simulation of the surface profile of the groove bottom enveloped by milling cutters in single screw compressors

In machining of a single screw compressor, the milling technique of screw rotor grooves with cylindrical milling cutters has far higher machining efficiency than turning. But, the screw groove bottom surface produced by the flat end of milling cutters will fail to mesh with the flat tooth tip hermetically, and thus give rise to compressed gas leakage. This paper carries out a mathematic simulation of the screw groove bottom surface profiles. The research brings screw groove bottom profiles machined by different cylindrical milling cutters to light, and provides some references for designing the column envelope meshing pairs in single screw compressors.

Numerical study on transient effective flow and force areas of reed valve in a rotary compressor

Transient effective flow and force areas of reed valve in a rotary compressor are studied by two three-dimensional fluid–structure interaction (FSI) models. One is the full FSI model, the other one is the simplified FSI model, in which the discharge port is not covered. It is apparent that two effects have to be considered in the one-dimensional valve model: partly covered discharge port by the cylinder and the roller, and unsteady flow. In an attempt to describe the first effect, comparison of the transient effective flow and force areas between the full FSI model and the simplified FSI model is presented. For the second effect, unsteady flow and force equations are developed and analyzed, and the steady effective flow and force areas are compared with that of the transient. It is found that if these two effects are negligible, the impact velocity of the valve reed impacting on the retainer will be overestimated.

An optimization of the star-wheel profile in a single screw compressor:

Single screw compressors have been used in various industrial fields, but the star-wheel does not have a good durability as expected. Good hydrodynamic lubrication states can enhance the wear resistance of the star-wheel. However, the imbalance of the lubricant film forces which act on the front flank and the back flank of the star-wheel tooth have a great influence on the lubrication between the meshing pair. In order to improve the lubrication, an approach for optimization of the star-wheel profile is developed, and the optimization goal is proposed in this paper. Column envelope profile meshing pair in an oil-flooded single screw compressor is taken as an optimization example. After optimization, the lubrication states in clearance between the groove flanks and the teeth flanks are improved. The meshing pairs with optimal profile are applied in an oil single screw compressor, and the experiment data supports the optimization approach well.

Geometric Design Investigation of Single Screw Compressor Rotor Grooves Produced by Cylindrical Milling

Cylindrical milling of a screw rotor groove in a single screw compressor has higher machining efficiency than turning. However, the screw groove bottom produced by the flat end of the milling cutter fails to mesh hermetically with the flat tooth tip due to the oversized clearance between them. The clearance forms two leakage paths leading to a compressed gas leakage. The shape of the path is roughly the same as that of two parallel oblate divergent nozzles in an inverse orientation. A mathematical simulation is presented for the surface profile of the screw groove bottom for a single screw compressor generated using several cylindrical milling cutters. The results contribute to improving the design of the meshing pairs in the single screw compressor.

Fluid–structure interaction model of dynamic behavior of the discharge valve in a rotary compressor:

A three-dimensional fluid–structure interaction model is proposed for the discharge valve movement in a rotary compressor. The compression chamber pressure measured by the experiment confirmed that the fluid–structure interaction model is able to predict the valve dynamic behavior precisely. To demonstrate that the fact of the discharge port being covered partly by the cylinder and the roller cannot be ignored in the valve model, another fluid–structure interaction model in which the discharge port is not covered and the cylinder shape is simplified to be cylindrical is also specially presented. In this simplified fluid–structure interaction model, the flow energy loss through the discharge valve is 68.8% of that in the fluid–structure interaction model, and the impact velocity of the valve reed impacting on the retainer is 2.9 m/s higher than that in the FSI model. It is found that the valve reed is obviously inclined because the discharge port is covered partly by the cylinder.

Dynamic simulation and stress analysis for reciprocating compressor crankshaft

With the continuous trend toward high speed and large size, the reciprocating compressor crankshaft faces more serious potential threat of crack due to vibration. Therefore, early stress analysis of the crankshaft must be done thoroughly in the design stage. This article introduces a method, which combines flexible body dynamic and finite element analysis to calculate stress of the crankshaft. In this method, the load variation with time is obtained by flexible body dynamics simulation of crank and connecting rod mechanism. After that loads are loaded on finite element model of the crankshaft, and then the stress of the crankshaft is calculated in time domain. This stress can be utilized to do fatigue analysis and predict the life of crankshaft. Using this method, stress of a practical crankshaft, belonging to 6M51 reciprocating compressor, is calculated. The result showed that the maximum von Mises stress is 158 MPa, and the estimated life, which was calculated by Palmgren–Miner linear damage accumulation theory, is 2.0230e + 007 hours.

Geometrical Design and Investigation of a New Profile of the Three Screw Pump

This paper presents a new edge blunting method of the three screw pump rotor with an elliptic arc and equations of the rotor profile after edge blunting. Through comparisons of different geometrical parameters of the pump, i.e., flow area, contact line length per lobe, blow hole area, etc., the new profile is proved to be better than the existing profiles of the three screw pump. The new streamlined profile, with a significantly smaller blow hole area, is of reference significance for the optimization design and further improvement of three screw pump.

Effect of a cross-flow perforated tube on pressure pulsation and pressure loss in a reciprocating compressor piping system

This paper experimentally investigates the effects of a cross-flow perforated tube on the pressure pulsation attenuation and pressure loss in a reciprocating compressor piping network, with particular focus on the structure parameters and installation positions. The results demonstrate that significant pressure fluctuation attenuation and less pressure loss in the whole piping system can be achieved when a well-designed cross-flow perforated tube is installed downstream of the pulsating bottle. The pressure pulsation is reduced as the perforated rate decreases and as the perforated tube length increases, while the hole diameter has little effect upon the pulsation attenuation. In the aspect of reducing pressure loss, the perforated rate should be larger than 0.05 and the hole diameter should be larger than 8 mm. In addition, a pressure pulsation computation model based on the linear acoustic wave theory and transfer matrix method is developed to predict the pulsating pressure in compressor piping systems with an installed cross-flow perforated tube. With favorable agreement between the model prediction and the present experimental results (maximum deviation within 6.8%), the predicted pulsating pressure can be attenuated for the reciprocating compressor piping system with various compressor speeds when a cross-flow perforated tube is reasonably designed and installed.