C. Z. Chen

Development of aerodynamic foil journal bearings for a high speed cryogenic turboexpander

The research presented in this paper is aimed at the development of aerodynamic foil journal bearings applying to a small high speed cryogenic turboexpander. A small high speed cryogenic turboexpander is designed. Attention has been paid to the study of the effect of foil stiffness on the vibration performance of bearings. From rotation tests, it is clear that, with the proper choice of foil stiffness, the foil bearing presented here can possess sufficiently high stability. The maximum rotational speed obtained is greater than 230 000 rpm. Therefore, owing to its simplicity and high performance, this type of foil journal bearing can hopefully be applied to a small high speed cryogenic turboexpander.

Experimental Study of a New Compliant Foil Air Bearing with Elastic Support

A new air-lubricated compliant foil journal bearing with elastic support, which has uniform surface stiffness and is much simpler in structure than previous compliant foil bearings (CFBs), is introduced in this article. Experiments have been conducted on the application of this type of CFB to a high-speed test rig, and this CFB can operate stably at 151,000 rpm. From the tests it is clear that the radial clearance C has a direct impact on the performance of this CFB, so the numerical relationship of structural parameters is listed in this article. Experimental results indicate that the CFB presented here offers preferable system dynamic and stability performance and has adequate damping to effectively reduce the possibility of self-excited and fractional frequency whirl.

The Experimental Study of Aerodynamic Plate-Foil Journal Bearings for High Speed Cryogenic Turboexpander

Experiments have been conducted on the application of a new type of gas lubricated self-acting journal bearing—plate-foil bearing to a high speed cryogenic turboexpander. The 25.0 mm diameter bearing consists of a rigid housing and a flexible foil element; different structure parameters of the bearing are selected in the experiments. Experimental results indicate the foil bearing presented here offers better system stability performance and high durability, and it confirmed that the application of this type of plate-foil bearing to the cryogenic turboexpander is feasible. The experiment results, including the effect of the plate-foil bearing structure parameters on the rotor-bearing system stability, are described in this paper. Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

A Feasibility Study on the Use of New Gas Foil Bearings in Cryogenic Turboexpander

Experiments have been conducted with two type of gas lubricated foil journal bearings and a small cryogenic turboexpander. One of these bearings is named as a spirally-wound foil bearing and the another is named as a multi-leaves foil bearing. Both of them have much simpler construction and lower cost as compared with the conventional foil bearings. The rotor of cryogenic turboexpander, 103 mm long and weighing 0.9 N, has the working speed up to 230,000 rpm. The main purpose of the investigation is a preliminary examination of stabilizing characteristics of those foil bearings under several different clearances and foil stiffness as well as the durability of the foils. Experimental results indicate the foil bearings presented here offer system stability and high durability, and it confirmed that the application of gas foil bearing to the cryogenic turboexpander is feasible and hopeful.

Durability and Stability Analysis of Compliant Foil Journal Bearings with Elastic Support Using Different Surface Treatments

The durability and stability characteristics of compliant foil journal bearings with elastic support are discussed in this paper. Using different choices for surface treatment of foil materials and foil element geometry parameters, the start-stop cycle and the rotor-bearing system dynamic characteristics of a compliant foil bearing (CFB) were experimentally studied. This CFB with elastic support can steadily run the turbo expander with a 25.0-mm-diameter rotor revolving at 14.8 × 10 4 rpm and has excellent performance in terms of stability and durability. The test results indicate that with suitable bearing structure parameters, foil materials and application of the surface treatment of this type of CFB is appropriate for high-speed turbo machinery.

A new helium gas bearing turboexpander

A new helium gas bearing turboexpander of a helium refrigeration system used for space environment simulation experiments is described in this paper. The main design parameters and construction type of some key parts are presented. An improved calculation of thermodynamic efficiency and instability speed of this turboexpander has been obtained by a multiple objects optimization program. Experiments of examining mechanical and thermodynamic performance have been repeatedly conducted in the laboratory by using air at ambient and liquid nitrogen temperature, respectively. In order to predict the helium turboexpander performance, a similarity principles study has been developed. According to the laboratory and on-the-spot experiments, the mechanical and thermodynamic performances of this helium turboexpander are excellent.

Predicting Performance of Expansion Turbines Using Different Working Fluids Based on the Artificial Neural Network

In order to obtain the efficiency curve of a helium Expansion Turbine (ET) in the factory, a method which can be used to transform the performance of an ET with one kind of Working Fluid (WF) to another must be investigated because of the lack of the helium in the factory. A performance prediction program based on an one-dimensional analysis of ETs has been developed and has proved valid. On the basis of the program, the Artificial Neural Network(ANN) (Back-Propagation Algorithm) has been used to deal with the transformation problem. The method has proved effective by the efficiency experiments of an ET using the CO2 and the air as the WF respectively.

Design of small turbo brayton cycle air refrigerator test rig

Publisher Summary This chapter introduces the reverse turbo brayton cycle refrigerator test rig established in 2002. The refrigerator adopts air as refrigerant medium and works in single stage, open cycle. The mechanical and thermodynamic performance of the refrigerator has been tested and analyzed. This test rig of small reverse turbo brayton cycle refrigerator employs open regenerative cycle and uses the air in atmosphere temperature as its refrigerant. The turbo expander is the most important component of the reverse brayton cycle refrigerator, and reflects the technological level of this system. The turbo expander provides the refrigeration capability in low temperature for system, so its thermodynamic and mechanical performance are extraordinary important to the economy and reliability of this equipment. The relationship between the temperature in the cryogenic box and the time has been shown. When the environmental temperature was 6°C and the rotational speed of turbine maintained at 220,000 rpm, the temperature of the cryogenic box could reach -75oC after 100 minutes and the temperature drop in turbo expander was 32oC at this time. The rotation speed of turbo expander has reached 230,000 rpm. The temperature in cold box can reach below 200 K and the temperature drop in the refrigerator has exceeded 80 K.

Study of new aerodynamic foil thrust gas bearing with elastic support for cryogenic turbo-expander

Publisher Summary This chapter conducts an experimental study to meet requirements of the gas bearing cryogenic turbo-expanders development. A new type of aerodynamic foil gas thrust bearing with elastic support is proposed and developed. The experimental study has been conducted on the gas bearing test rig. The factors affected on the main performances of the gas bearing have been analyzed and the ranges of optimum bearing parameters have been obtained. The Cryogenic turbo-expander, using the foil gas beatings with elastic support, has better development potential and wide application foreground. In recent years, two types of new self-acting foil thrust beatings have been proposed and developed. The foil beating is supported with double layers copper wires and elastic material respectively. And the domestic experiments have been conducted on the gas beating test rig. The features of the new aerodynamic foil thrust gas beating with elastic support are given briefly in this chapter. The experimental results indicate that the new aerodynamic foil thrust gas bearing with elastic support possesses good stability and operation performance. The good damping characteristics of the elastic support material restrain the rotors vibrations and the growth of whiting amplitudes. And the flexible surface of the bearing decreases the damage to the rotor and the beating surface effectively. The good damping characteristics of the elastic support and the good performance of the bearing are presented sufficiently.