Modeling of an Oil-Free Carbon Dioxide Compressor Using Sanderson-Rocker Arm Motion (S-RAM) Mechanism

Transcription

1 Modeling of an Oil-Free Carbon Dioxide Compressor Using Sanderson-Rocker Arm Motion (S-RAM) Mechanism Bin Yang, Orkan Kurtulus, and Eckhard A.Groll Purdue University Ray W. Herrick Laboratories West Lafayette, Indiana 47907, USA

2 Learning Objectives Introduction to a CO2 compressor using a novel driving mechanism Introduction to the integrated simulation model ASHRAE is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to ASHRAE Records for AIA members. Certificates of Completion for non-aia members are available on request. This program is registered with the AIA/ASHRAE for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. 2

3 Outline Introduction Modeling Effort Kinematics model In-cylinder process model Gas pulsation in discharge pipes Overall energy balance model Numerical Methodology Simulation Results Future Work 1/27/ ASHRAE Winter Conference

4 Introduction High efficiency mechanism to convert shaft rotary motion into piston reciprocating motion. Patents 35+ patents issued since the first patent in

5 Introduction Features Oil free Less frictional power loss Variable capacity control (constant clearance volume above the piston top!) 5

6 Outline Introduction Modeling Effort Kinematics model In-cylinder process model Gas pulsation in discharge pipes Overall energy balance model Numerical Methodology Simulation Results Future Work 1/27/ ASHRAE Winter Conference

7 Kinematics Model universal joint origin of the coordinate system Schematic of Driving Mechanism Coordinate System 7

8 Kinematics Model 1/27/ ASHRAE Winter Conference

9 Kinematics Model 14, Z m max,1 10, Z m max,2 Z Z x max,1 max,2 x x x x cos cos14 x (cos10 cos14 ) x = = "= m 2 Z Z x max,1 max,2 9

10 In-cylinder Process Model Governing equations Continuity equation: Kinematic equation: Energy equation: dm dm dm dm dm dt dt dt dt dt c suc li dis lo dvc 1 dvc Vc dmc 2 dt mc dt mc dt dq dw d ( m c u c) dm dis dm lo dm suc dm li h h h h dt dt dt dt dt dt dt dis lo suc li Leakage model: isentropic, compressible fluid Valve model: isentropic, compressible fluid dmgap 2 p ( ) 2 d pd p { [( ) ( ) ]} 2 d mgap Cgap Agap p u, 0.54 dt ZRTu 1 pu pu pu dmgap 2 p ( ) 2[( ) 1] 2 d mgap Cgap Agap p u, 0.54, choked dt ZRTu 1 pu dmvalve p (2 ) 2 low plow { [( ) ( ) ]} 2 valve valve valve high high dt 1 phigh phigh m C A p 10

11 Gas Pulsation in Discharge Pipes - Anechoic assumption - Elson and Soedel s method (1974) impedance Z oscillated acoustic pressure p pul 0 u pul c gas density in the pipeline gas velocity speed of sound 11

12 Overall Energy Balance Model m ( h h ) Q Q Q comp suc, a case plate, gas gas, shell friction, loss Q Q gas, shell shell, amb 0 Q Q Q Q 0 plate, amb,1 plate, amb,2 plate, gas cyl, wall Q m ( h h ) 0 pipe, amb comp suc, a suc, b W Q m ( h h, ) comp cyl, wall comp dis suc b Schematic of overall energy flow Q Ta T R ab b 12

13 Overall Energy Balance Model T plate Q cyl, wall T gas R plate, gas Q friction, loss R gas, shell R plate, shell R plate, amb,1 R plate, amb,2 T shell R shell, amb T amb Thermal resistance network of the overall energy balance n t T Qcyl, wall Qcyl, wall dt 60 t 13

14 Overall Energy Balance Model Heat transfer categories: Convection along the horizontal plate Convection along the vertical plate Convection along the horizontal pipe Convection along the vertical pipe Heat conduction between cylinder plate and case shell (neglected here) 14

15 Overall Energy Balance Model Real pipe arrangement Simplified pipe arrangement 15

16 Outline Introduction Modeling Effort Kinematics model In-cylinder process model Gas pulsation in discharge pipes Overall energy balance model Numerical Methodology Simulation Results Future Work 1/27/ ASHRAE Winter Conference

17 Numerical Methodology Flow chart of in-cylinder process model solution 17

18 Numerical Methodology Flow chart of overall compressor model solution 18

19 Outline Introduction Modeling Effort Kinematics model In-cylinder process model Gas pulsation in discharge pipes Overall energy balance model Numerical Methodology Simulation Results Future Work 1/27/ ASHRAE Winter Conference

20 Simulation Results P-V diagram Valve displacement 20

21 Simulation Results Effect of discharge pressure P-V diagram Discharge valve displacement 21

22 Simulation Results Effect of discharge pressure Instantaneous heat transfer between in-cylinder refrigerant and cylinder wall In-cylinder refrigerant temperature 22

23 Simulation Results Effect of stroke-to-bore ratio Instantaneous refrigerant leakage through clearance between piston assembly and cylinder wall Instantaneous heat transfer between in-cylinder refrigerant and cylinder wall 23

24 Simulation Results Effect of stroke-to-bore ratio Effect of stroke-to-bore ratio on the volumetric efficiency 24

25 Outline Introduction Modeling Effort Kinematics model In-cylinder process model Gas pulsation in discharge pipes Overall energy balance model Numerical methodology Simulation results Future Work 1/27/ ASHRAE Winter Conference

26 Future Work Dynamics model (frictional power loss) Performance testing of the prototype compressor Discharge pipe gas pulsation measurement Validation of the simulation model Parametric studies 26

27 Questions? Bin Yang 27