A Comparison of Inverse Models for the Estimation of Ice-Induced Propeller Moments on a Polar Vessel

Full-scale measurements were conducted on the port side propulsion shaft the S.A. Agulhas II during the 2019 SCALE Spring Cruise. The measurements included the shaft torque captured at two separate measurement locations, and the shaft rotational speed at one measurement location. The ice-induced propeller moments are estimated from the full-scale shaft responses using two inverse models. The first is a published discrete lumped mass model that relies on regularization due to the inverse problem being ill-posed. This model is only able to make use of the propulsion shaft torque as inputs. The second model is new and employs modal superposition to represent the propulsion shaft as a combination of continuous modes, resulting in a well-posed problem. This new model requires the additional measurement of the shaft rotational speed for the inverse solution. The continuous model is shown to be more consistent and efficient, which allows its use in real-time monitoring of propeller moments.

Estimation of gas turbine shaft torque and fuel flow of a CODLAG propulsion system using genetic programming algorithm

In this paper, the publicly available dataset of condition based maintenance of combined diesel-electric and gas (CODLAG) propulsion system for ships has been utilized to obtain symbolic expressions which could estimate gas turbine shaft torque and fuel flow using genetic programming (GP) algorithm. The entire dataset consists of 11934 samples that was divided into training and testing portions of dataset in an 80:20 ratio. The training dataset used to train the GP algorithm to obtain symbolic expressions for gas turbine shaft torque and fuel flow estimation consisted of 9548 samples. The best symbolic expressions obtained for gas turbine shaft torque and fuel flow estimation were obtained based on their R2 score generated as a result of the application of the testing portion of the dataset on the aforementioned symbolic expressions. The testing portion of the dataset consisted of 2386 samples. The three best symbolic expressions obtained for gas turbine shaft torque estimation generated R2 scores of 0.999201, 0.999296, and 0.999374, respectively. The three best symbolic expressions obtained for fuel flow estimation generated R2 scores of 0.995495, 0.996465, and 0.996487, respectively.

Torque at elastic-plastic torsion of sheet-straightening machines’ steel shafts

The experiments on the torsion of the steel shaft were conducted on the machine Instron 55MT2 with a maximum torque of 220 N×m and a mass of 2500 N. The ends of the shaft clamped with collet-chucks. For the torsion we used the round cylindrical samples from a low-carbon steel with the Young’s modulus of 2×1011 Pa, the shear modulus of 7.752×1010 Pa, the Poisson’s ratio of 0.29, the yield strength of 524 MPa, the yield strength at shift of 302 MPa, the ultimate shear stress of 352 MPa, the ultimate shift of 0.18 and the plastic module at shift of 740 MPa. The torsion of the steel shafts and thick-walled pipes is widely used in the metallurgy, mechanical engineering and oilgas industry. For example, the shafts’ torsion is observed in the drive mechanisms of the sheet-straightening machines for the thin and thick steel sheets, in the rolling mills for the cold and hot steel sheets, in the drives of the rear wheels of motor transport, in the land and sea gas-oil drilling platforms and so on. Under the significant torque, the steel shafts can experience not only elastic, but also plastic deformation without the destruction. The experimental dependence of the shaft torque on the twisting angle gives researchers much more information about the mechanical properties of steel than the analogous experiments on the rupture of the steel shafts, since there is no neck formation during the torsion and the steel shaft does not collapse even at the very large twisting angles. The classical Ludwik’s and Nadai’s approximations for shear do not sufficiently accurately describe the shear deformation and are, therefore, not sufficiently effective for calculating the shaft torque. Therefore, the more accurate the straight and back Shinkin’s approximations are used below to describe the shear deformation. A special feature of calculating the dependence of the shaft torque on the shear angle is that the torque is calculated approximately as a power series, since the corresponding integrals are transcendental (cannot be calculated analytically). At the same time, the relative accuracy of the torque calculation is very high (about 10-6 %).

The Sensitivity Study of a Mechanical Loss Model in Turbocharger System

3D modelling can be a very useful tool for optimising the design of turbocharger turbines. However, it is difficult to achieve high levels of correlation with experimental data which can undermine confidence in the 3D model results. A key difference between modelling and experiments is the way turbine efficiency is estimated: in CFD this is estimated directly from the shaft torque created by the turbine, however in experiments this is usually estimated based on the enthalpy rise measured at the compressor. This means that there is an inherent offset between the two which is the mechanical losses of the bearing system used to support the connecting shaft. The accuracy of the mechanical loss estimate can therefore play a critical role in the correlation of 3D modelling with experiments. A 3D CFD model of a turbocharger turbine of a 1.5L gasoline engine has been coupled with a 0D mechanical losses model. The model comprises of seven parameters that characterise the bearing losses such as oil film thickness, bearing surface finish and clearances. A sensitivity study is conducted on these parameters to understand which are the critical aspects that should be parameterised and what relationship these parameters may have with the operating state of the turbocharger (shaft speed, shaft torque etc.). Experimental measurements were conducted for the same turbocharger to provide a baseline for assessing the impact of the mechanical losses model. These provide the boundary conditions to the CFD by ignoring the effects of heat transfer, and the results were compared to the 3D simulation results.

Full-Scale Propulsion Measurements on a Planing Pleasure Yacht in Head Sea

Full scale seakeeping trials are rare, especially planing hull and are in general focused in studying bottom pressures, accelerations and vibrations. In this paper, a comprehensive description of the experimental setup and analysis of full scale seakeeping trials propulsion data of a 65 ft planing pleasure yacht is presented. Torque and rpm have been measured on both propeller shafts during seakeeping trials in mild sea conditions, along with hull motions and accelerations. Correlations between hull motions and propulsion data are discussed, both in the time and frequency domain. Further tests on a shaft sample have been carried out in order to validate its mechanical properties and hence quantitative results regarding shaft torque. The main novelty of the present work lays in a detailed analysis of the propulsion system response of a planing pleasure yacht in mild weather conditions.