Research Papers: Internal Combustion Engines

Kinematics of an Articulated Connecting Rod and Its Effect on Simulated Compression Pressures and Port Timings

[+] Author and Article Information
Kelsey Fieseler

Texas A&M University,
College Station, TX 77843
e-mail: kdfieseler@gmail.com

Timothy J. Jacobs

Texas A&M University,
College Station, TX 77843
e-mail: tjjacobs@tamu.edu

Mark Patterson

GE Oil & Gas,
Houston, 77040
e-mail: mark.patterson@bhge.com

Contributed by the IC Engine Division of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 21, 2018; final manuscript received March 21, 2018; published online May 24, 2018. Editor: David Wisler.

J. Eng. Gas Turbines Power 140(9), 092803 (May 24, 2018) (7 pages) Paper No: GTP-18-1087; doi: 10.1115/1.4039831 History: Received February 21, 2018; Revised March 21, 2018

This study discusses the motion of the articulated connecting rod of an integral-engine compressor and the effect of the kinematics on in-cylinder pressure and port timings. A piston position modeling technique based on kinematics and engine geometry is proposed in order to improve the accuracy of simulated in-cylinder compression pressures. Many integral-engine compressors operate with an articulated connecting rod. For this type of engine-driven compressor, two power pistons share a crank throw with the compressor. The hinge pins that attach the power piston connecting rods to the crank are offset, causing the piston locations for each cylinder to be out of phase with each other. This causes top dead center (TDC) to occur at different crank angles, alters the geometric compression ratio, and also changes the port timings for each cylinder. In this study, the equations of motion for the pistons of the four possible compressor/piston configurations of a Cooper-Bessemer GMW are developed. With the piston profiles, the intake and exhaust port timings were determined and compared to those of a slider-crank mechanism. The piston profile was then inputted into GT-POWER, an engine modeling software developed by Gamma Technologies, in order to obtain an accurate simulation match to the experimental in-cylinder pressure data collected from a Cooper-Bessemer GMWH-10C. Assuming the piston motion of an engine with an articulated connecting rod is similar to a slider-crank mechanism can create a difference in port timings. The hinge pin offset creates asymmetrical motion about 180°aTDC, causing the port timings to also be asymmetrical about this location. The largest differences are shown in the intake port opening of about 10 deg and a difference in exhaust port opening of about 7 deg when comparing the motion of the correct configuration to the motion of a slider-crank mechanism. It is shown that properly calculating the piston motion profiles according to the crank articulation and engine geometry provides a good method of simulating in-cylinder pressure data during the compression stroke.

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Fig. 1

Articulated connecting rod configuration of an integral-compressor engine. Adapted from Ref. [10].

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Fig. 2

A schematic of a theoretical four-cylinder integral-compressor engine with two compressors on opposite sides

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Fig. 3

Geometry of the articulated connecting rod system with variables labeled

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Fig. 4

Geometry of a slider-crank mechanism with variables labeled [2]

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Fig. 5

Piston depth normalized to BDC versus crank angle

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Fig. 6

Normalized piston depth to BDC versus crank angle, zoomed in to near BDC

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Fig. 7

Normalized hingepin motion for pistons with same-side compressors

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Fig. 8

Normalized hinge pin motion for pistons with opposite-side compressors

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Fig. 9

Port timings compared to the timings of a slider-crank mechanism

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Fig. 10

Experimental and simulated compression stroke for a LH bank piston with a RH compressor

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Fig. 11

Experimental and simulated compression stroke for a RH bank piston with a RH compressor

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Fig. 12

Experimental and simulated compression stroke for a LH bank piston with a LH compressor

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Fig. 13

Experimental and simulated compression stroke for a RH bank piston with a LH compressor




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