Transient tribo-dynamic analysis of crosshead slipper in low-speed marine diesel engines during engine startup

Rui LI; Xianghui MENG; Jingjin DONG; Wenda LI

doi:10.1007/s40544-020-0433-9

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Research Article | Open Access

Transient tribo-dynamic analysis of crosshead slipper in low-speed marine diesel engines during engine startup

Rui LI^{¹^,²}, Xianghui MENG^{¹^,²}(), Jingjin DONG^³, Wenda LI^³

1State Key Laboratory of Mechanical System and Vibration, Shanghai Jiaotong University, Shanghai 200240, China

2School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China

3China Shipbuilding Power Engineering Institute Company Limited, Shanghai 201206, China

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Abstract

A crosshead slipper-guide system, which bears a significant thrust force, is an essential friction pair in low-speed marine diesel engines. Owing to the low moving speed of the crosshead slipper during engine startup, it is difficult to form good hydrodynamic lubrication between the crosshead slipper and guide. Therefore, a detailed analysis of the crosshead slipper during engine startup is needed. In this study, a new transient tribo-dynamic model for a crosshead slipper during the engine startup process is presented. The model consists of a mixed lubrication model of the crosshead slipper-guide and dynamic models of the piston assembly, crosshead assembly, connecting rod, and crankshaft. The tribo-dynamic performances of the crosshead slipper during startup and under the rated conditions were simulated and compared. The results show that the tribo-dynamics of the crosshead slipper during the startup process are significantly different from those under the rated conditions. Some measures beneficial for the low friction of a crosshead slipper-guide under the rated conditions may significantly increase the friction loss of the crosshead slipper-guide system during the startup process.

Keywords

low-speed marine diesel engine crosshead slipper engine start-up mixed lubrication friction loss tribo-dynamic model

References

[1]

Holmberg

, Erdemir

. Influence of tribology on global energy consumption, costs and emissions. Friction 5(3): 263–284(2017)

$A_{1}, A_{2}$	Lubricating area of slipper on thrust side and anti-thrust side
$a$	Vertical distance between the crosshead pin center and top of slipper
$b$	Vertical distance between the center of mass (COM) of slipper and top of slipper
$COM$	Abbreviation of “center of mass”
$C$	Slipper-guide nominal clearance
$e_{t}, e_{b}$	Eccentricities of slipper at the top and bottom ends
$e_{tp}, e_{bp}$	Eccentricities of piston skirt at the top and bottom ends
$F_{x}$	Force of slipper from crosshead pin in X direction
$F_{y}$	Force of slipper from crosshead pin in Y direction
$F_{c}$	Total normal force acting on slipper from guide
$F_{c f}$	Total friction force acting on slipper from guide
$F_{c s x}$	Force of connecting rod from crankshaft in X direction
$F_{c s y}$	Force of connecting rod from crankshaft in Y direction
$F_{ic 1}$	Reciprocating inertial force of slipper
$F_{ic 2}$	Transverse inertial force of slipper
$F_{icp1}$	Reciprocating inertial force of crosshead pin
$F_{icp2}$	Transverse inertial force of crosshead pin
$F_{ip1}$	Reciprocating inertial force of piston
$F_{ip2}$	Transverse inertial force of piston
$F_{irod1}$	Reciprocating inertial force of piston rod
$F_{irod2}$	Transverse inertial force of piston rod
$F_{i c r x}$	Connecting rod inertial force in X direction
$F_{i c r y}$	Connecting rod inertial force in Y direction
$F_{p}$	Total normal force acting on piston skirt from cylinder liner
$F_{pf}$	Total friction force acting on piston skirt from cylinder liner
$F_{x 1}$	Force of piston from bolt in X direction
$F_{x 2}$	Force of piston rod from bolt in X direction
$F_{y 1}$	Force of piston from bolt in Y direction
$F_{y 2}$	Force of piston rod from bolt in Y direction
$f (x_{1}, y_{1})$	Profile of slipper
G_c	Gravity of slipper
$G_{cp}$	Gravity of crosshead pin
$G_{p}$	Gravity of piston
$G_{rod}$	Gravity of piston rod
$G_{cr}$	Gravity of connecting rod
$h_{c}$	Oil film thickness of slipper
$I_{c}$	Rotary inertia of slipper about its COM
$I_{p}$	Rotary inertia of piston about its COM
$I_{cp}$	Rotary inertia of crosshead pin about its COM
$I_{rod}$	Rotary inertia of piston rod about its COM
$I_{cr}$	Rotary inertia of connecting rod about its COM
$j$	Ratio of $l_{s t}$ to $l_{r t}$
$L$	Length of piston rod
$L_{1}$	Vertical distance between COM of piston and top end of piston skirt
$L_{2}$	COM of piston and bottom end of piston skirt
$L_{3}$	Length of slipper
$l_{rt}$	Length of connecting rod
$M_{1}$	Moment of piston from bolt
$M_{2}$	Moment of piston rod from bolt
$M_{c}$	Moment of $F_{c}$ about the crosshead pin center
$M_{i c}$	Inertial moment of slipper
$M_{ip}$	Inertial moment of piston
$M_{icp}$	Inertial moment of crosshead pin
$M_{irod}$	Inertial moment of piston rod
$m_{c}$	Mass of slipper
$m_{p}$	Mass of piston
$m_{cp}$	Mass of crosshead pin
$m_{rod}$	Mass of piston rod
$m_{cr}$	Mass of connecting rod
$p$	Oil film pressure
$p_{c}$	Contact pressure
$R$	Piston radius
$R_{c}$	Crank radius
$R_{pin}$	Crosshead pin radius
$U = {\dot{Y}}_{c}$	Longitudinal velocity of crosshead slipper
$w$	Half of the height of slipper
$x_{1}$ , $y_{1}$	Local coordinate system on the crosshead slipper
$X, Y$	Global coordinate system
$Y_{c}$	Longitudinal displacement of crosshead assembly and piston assembly
$σ$	Composite roughness of slipper and guide
$θ$	Connecting rod angle
$φ$	Crack angle
$ϕ_{x}, ϕ_{y}$	Pressure flow factors
$ϕ_{c}$	Contact factor
$ϕ_{s}$	Shear flow factor
$ϕ_{f}, ϕ_{f s}, ϕ_{f p}$	Shear stress factors
$μ$	Dynamic lubricant viscosity
$ω = \dot{φ}$	Rotation speed of crankshaft
$γ_{p}$	Attitude angle of piston
$μ_{f}$	Friction coefficient of asperity contact

Parameter	Meaning	Value
$I_{c}$	Rotary inertia of crosshead slipper about its COM	0.83 (kg·m²)
$I_{cp}$	Rotary inertia of crosshead pin about its COM	0.51 (kg·m²)
$I_{p}$	Rotary inertia of piston about its COM	1.11 (kg·m²)
$I_{rod}$	Rotary inertia of piston rod about its COM	52.36 (kg·m²)
$I_{cr}$	Rotary inertia of connecting rod about its COM	258.50 (kg·m²)
$L$	Length of piston rod	2074E-3 (m)
$L_{1}$	Vertical distance between COM of piston and top end of piston skirt	29.50E-3 (m)
$L_{2}$	Vertical distance between COM of piston and bottom end of piston skirt	29.50E-3(m)
$L_{3}$	Length of crosshead slipper	300E-3 (m)
$l_{r t}$	Length of connecting rod	1600E-3 (m)
$m_{c}$	Mass of crosshead slipper	25 (kg)
$m_{cp}$	Mass of crosshead pin	60 (kg)
$m_{p}$	Mass of piston	90 (kg)
$m_{rod}$	Mass of piston rod	202.80 (kg)
$m_{cr}$	Mass of connecting rod	575.60 (kg)
$R$	Piston radius	170E-3 (m)
$R_{c}$	Crank radius	800E-3 (m)
$R_{pin}$	Crosshead pin radius	130E-3 (m)
w	Half of the height of slipper	325E-3 (m)
J	Rotation inertia of the crankshaft	8E4 (kg·m²)
M	Resistance moment on the shaft	1000 (N·m)

Parameter	Value
Surface pattern parameter	1
Guide surface rms roughness	0.7 (μm)
Crosshead slipper surface rms roughness	0.8 (μm
$η$	0.038 (μm^-2)
$β$	7.57 (μm)
Asperity friction coefficient ( $μ_{f}$ )	0.15