Torque ratio concept for combustion phasing detection of a spark ignited engine
This paper presents a method for estimating combustion phasing of a five cylinder, four stroke, spark ignited engine, equipped with a crankshaft based torque sensor. A new measure for combustion phasing based on the torque signal is derived for a single cylinder engine. The measure is called 50% torque ratio. A validation of the measure is done by comparing to the related cylinder pressure based 50% pressure ratio measure. A method is also presented to apply the torque ratio measure to a multi-cylinder engine. A physical model for the instantaneous torque measurement is described handling the torque contributions from all individual cylinders in all combustion phases. The torque contribution from the combusting cylinder is isolated and analyzed by the torque ratio method to find the combustion phasing. The multi-cylinder algorithm is validated on torque and cylinder pressure data from a five cylinder Volvo V70 engine.
A system inversion approach on a crankshaft of an internal combustion engine
This paper presents a method for inversion of a five-input-one-output mechanical system, a crankshaft of an internal combustion engine. The inputs are the individual torque contributions from each cylinder combustion and the output is the total momentary torque output of the engine. The system inversion problem appears when individual combustion classification of a multi-cylinder engine is desired based on a measurement of the output signal only. The crankshaft can be represented as a linear system with modifications to the input signals. The system inversion method requires that only one input signal at a time is estimated, and the others are regarded as known. The linear part of the crankshaft model was found from two sources; physical modeling and identification of a black-box model. The cylinder individual estimated input torque is used for an estimation of a combustion phasing measure for comparison. The combustion phasing measure used is the 50% torque ratio and was calculated for both the measured and the estimated input torque. The physical model shows good correlation for low engine speeds but with an offset. The identified black-box model shows good performance at both 1000 and 3000 rpm without any offset.
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.