Numerical Simulation of Discharge Process in the Single Screw Compressor

In the process of the single screw air compressor, the symmetrical grooves of the compressor are periodically connected with the discharge ports and the gas enters the discharge chamber or flows back from chamber, generating gas pulsation. The gas pulsation increases the flowing loss to bring additional energy loss, meanwhile the gas pulsation is the one of main reasons for the generation of vibration and noise. The thermodynamic model of the compression chamber and the discharge chamber of a single screw air compressor is established in this paper taking the discharge chamber structure and the flow resistance into consideration. The working process in discharge chamber is simulated base on the thermodynamic model. In addition, the influence of speed and back pressure on the pressure in the discharge chamber is investigated in detail. The analysis results provide a basis for optimum design of structure and reduction of vibration and noise

Simulation of the Superheated Water Expansion Process in a Cylinder with Moving Piston

The Trilateral cycle has attracted more and more attentions because of its better temperature profiles matching in the heater compared to conventional heat recovery cycles, such as the Organic Rankine Cycle and the Kalina Cycle. However, the actual fundamentals of the two-phase expansion process have not been clarified, especially, the evolution mechanisms of the evaporating rate and the degree of superheat during the expansion process are indistinct. In the present study, two-phase expansion process of superheated water in a cylinder with moving piston was analyzed. A model was proposed to calculate the evaporating rate and the degree of superheat of liquid water. A semiempirical Nusselt number was adopted to solve the energy conservation equations. It was shown that the degree of superheat of liquid water was increased rapidly to the maximum at the beginning of the expansion process and then was decreased continuously. The degree of superheat was almost equal to 0 at the end of the expansion process. The simulation results also showed a complex evolution profile of the evaporating rate during the expansion process. As a whole, the evaporating rate was increased from 0 to the maximum, and then it was decreased to 0 at the end of the expansion process. This situation is similar to the experimental results in the published literature. The evaporating rate appeared a transient dropping process at the beginning of the expansion. It was considered that this result was associated with the rapid decline of the degree of superheat. Meanwhile, there were two or three significant inflection points on the evolution profile. From the model prediction, it was concluded that the evaporating rate may be related to the degree of superheat of liquid water, the piston velocity and the mass of liquid water in the cylinder

Cofilin Activation in Peripheral CD4 T Cells of HIV-1 Infected Patients: A Pilot Study

Cofilin is an actin-depolymerizing factor that regulates actin dynamics critical for T cell migration and T cell activation. In unstimulated resting CD4 T cells, cofilin exists largely as a phosphorylated inactive form. Previously, we demonstrated that during HIV-1 infection of resting CD4 T cells, the viral envelope-CXCR4 signaling activates cofilin to overcome the static cortical actin restriction. In this pilot study, we have extended this in vitro observation and examined cofilin phosphorylation in resting CD4 T cells purified from the peripheral blood of HIV-1-infected patients. Here, we report that the resting T cells from infected patients carry significantly higher levels of active cofilin, suggesting that these resting cells have been primed in vivo in cofilin activity to facilitate HIV-1 infection. HIV-1-mediated aberrant activation of cofilin may also lead to abnormalities in T cell migration and activation that could contribute to viral pathogenesis.Department of Defense (National Defense Science and Engineering Fellowship); National Institute of Allergy and Infectious Diseases (AI069981

Study of Valve Motion in Reciprocating Refrigerator Compressors based on the 3-D Fluid–structure Interaction Model

 Abstract: In this paper, a 3-D fluid-structure interaction model was established to investigate the working process of the small reciprocating refrigeration compressors. According to the numerical calculation, the working process of the small reciprocating refrigeration compressor, the motion of valve and the impact velocity and the contact stress of discharge valve and suction valve were given. Experiments on a small reciprocating refrigeration compressor for testing the p-v graph were carried out .Experimental results agree well with the numeric model. The result provides a guidance to research and design the small reciprocating refrigeration compressors