Abstract
The top-tensioned riser is an important equipment in offshore oil and gas development. The hydro-pneumatic tensioner is an essential device to ensure the safety of the top-tensioned riser. To investigate the dynamic performance of the marine platform hydro-pneumatic tensioner, this paper proposed a first-order Taylor approximation method and created the frequency response function of the hydro-pneumatic tensioner. According to the frequency response function, the hydro-pneumatic tensioner is a first-order spring-mass system. With the given parameters, the system stiffness coefficient is 66.1 kN/m, the natural annular frequency is 20.99 rad/s and the damping ratio is 2.23 × 10−4. The effects of the high-pressure accumulator, low-pressure accumulator, hydraulic cylinder and pipeline design parameters on the stiffness coefficient, natural annular frequency and damping ratio are analyzed. The stiffness coefficient can be increased by (1) increasing the high-pressure accumulator pressure and reducing the high-pressure accumulator volume; (2) increasing the pressure of the low-pressure accumulator and reducing the low-pressure accumulator volume; (3) increasing the piston diameter; and vice versa. The natural annular frequency can be increased by: (1) increasing the high-pressure accumulator pressure and reducing the high-pressure accumulator volume; (2) increasing the pressure of the low-pressure accumulator and reducing the low-pressure accumulator volume; (3) increasing the piston diameter; and vice versa. The damping ratio can be increased by increasing the pipeline length and reducing the pipeline inner diameter.
Highlights
The top-tensioned riser (TTR) system is widely used on the offshore floating production platform, which connects the underwater wellhead and the platform
This paper proposed a first-order Taylor approximation method to create frequency response function of the hydro-pneumatic tensioner (HPT) and analyzed the effects of the design parameters of the high-pressure accumulator, low-pressure accumulator, hydraulic cylinder, oil pipeline and friction between the piston and cylinder on the stiffness coefficient, natural annular frequency and damping ratio of the tensioner system
The following assumptions [2,17,18] are made: (1) There is no leakage of gas or hydraulic fluid; (2) Due to thermal inertia, nitrogen is approximately adiabatic during the dynamic process; (3) The hydraulic oil pressure in the high-pressure accumulator is equal to the gas pressure; (4) Hydraulic oil is incompressible
Summary
The top-tensioned riser (TTR) system is widely used on the offshore floating production platform, which connects the underwater wellhead and the platform. Proposed a coupled model of vortex-excited vibration and parameter-excited vibration for the TTR and analyzed the influence of the tube vibration on the platform motion. Wang Y. et al established models to study the vortexinduced vibration bifurcation response of TTR under variable lift coefficient and shear flow [12,13]. These studies were based on the same assumption: the tension force of the riser is constant. Some studies developed more detailed models for the HPT [16,17,18,19,20,21,22] and used the models in riser systems to study the influence of tensioner parameters These studies were based on the time domain analysis rather than frequency domain, and the influence of frequency domain characteristics was not considered. This paper proposed a first-order Taylor approximation method to create frequency response function of the HPT and analyzed the effects of the design parameters of the high-pressure accumulator, low-pressure accumulator, hydraulic cylinder, oil pipeline and friction between the piston and cylinder on the stiffness coefficient, natural annular frequency and damping ratio of the tensioner system
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