‘Shuttle’ Technology for Noise Reduction and Efficiency Improvement of Hydrostatic Machines - Part 2

In 2001, INNAS introduced the ‘Shuttle’ technology for noise reduction and efficiency improvement of hydrostatic machines. The current study revisits this technology for application in hydrostatic pumps and motors. In many hydrostatic pumps and motors, commutation is imposed by a fixed component like a valve plate. Designing a valve plate (or comparable component) that ensures good commutation at one specific operating condition, is fairly simple. However, an inherent problem of such a component is that it should ensure good commutation at all of the operating conditions. In an attempt to minimise losses and reduce noise emission caused by improper commutation, so-called shuttles were introduced by INNAS in 2001. These shuttles act as small pistons between two working chambers, essentially providing a connection to the ports while the valve plate is still closed. In theory, this will result in a check-valve like commutation. In the original paper, shuttles were implemented in a hydraulic transformer. This paper discusses and analyses the use of shuttles in pumps and motors. Simulation results show that the introduction of shuttles can reduce commutation losses to negligible levels. Furthermore, the results suggest that the use of shuttles could also reduce noise emissions.

Algebraic Parameter Identification of Nonlinear Vibrating Systems and Non Linearity Quantification Using the Hilbert Transformation

A novel algebraic scheme for parameters’ identification of a class of nonlinear vibrating mechanical systems is introduced. A nonlinearity index based on the Hilbert transformation is applied as an effective criterion to determine whether the system is dominantly linear or nonlinear for a specific operating condition. The online algebraic identification is then performed to compute parameters of mass and damping, as well as linear and nonlinear stiffness. The proposed algebraic parametric identification techniques are based on operational calculus of Mikusiński and differential algebra. In addition, we propose the combination of the introduced algebraic approach with signals approximation via orthogonal functions to get a suitable technique to be applied in embedded systems, as a digital signals’ processing routine based on matrix operations. A satisfactory dynamic performance of the proposed approach is proved and validated by experimental case studies to estimate significant parameters on the mechanical systems. The presented online identification approach can be extended to estimate parameters for a wide class of nonlinear oscillating electric systems that can be mathematically modelled by the Duffing equation.

Wind Turbine Lubrication Based on Parallel Control of Multiple Factors

The lubrication needs of wind turbines vary with the operating conditions. To provide a dynamic lubrication scheme for wind turbines under variable conditions, this paper designs a dynamically adjustable lubrication scheme through parallel control of multiple influencing factors. Based on mid- and long-term loads, the proposed scheme fully considers the influence of various sudden changes in addition to slowly changing factors like load, operating hours, and speed, such as to dynamically adjust the injection flow as per the specific operating condition of the turbine. The ideal lubrication effect was tracked through the adjustment of the injection flow or injection time, and used to determine the optimal dynamic lubrication control strategy during turbine operation. The proposed control strategy overcomes the defects of the traditional fixed-time fixed-flow lubrication approach, and provides reasonable on-demand lubrication schemes for wind turbines in different operating conditions. The on-demand injection of lubricant prevents under- or over-lubrication, reduces the rate of mechanical failure, and extends the service life of wind turbines. Suffice it to say that the proposed control strategy can lower power generation cost and save energy, making wind turbines more profitable.

Optimization of the Mechanical and Thermodynamic Efficiency Loss Dynamic in a Lean Single Cylinder Natural Gas-Fueled Jet Ignition Engine

In an effort to reduce fuel consumption and lower emissions output, there is a growing need for high efficiency engines in power generation. Ultra-lean (λ > ∼1.6) combustion via air dilution is an enabling technology for achieving high efficiencies while simultaneously reducing emissions of nitrogen oxides (NOx). Jet ignition is a pre-chamber-based combustion system that enables ultra-lean operation beyond what is achievable with traditional spark ignition engines. In this paper, results and analyses related to the downspeeding of a 390cc, high efficiency low-output single cylinder jet ignition engine operating ultra-lean are presented. The engine was developed as part of the US Department of Energy’s Advanced Research Projects Agency–Energy (DOE ARPA-E) GENSETS program1. The purpose of the program is to develop technologies for use in high efficiency combined heat and power generator sets. Due to the intended application of power generation, optimization of the engine for a specific operating condition is critical. An efficiency loss breakdown based on the Thermodynamic First Law is used to analyze the interdependent trends of engine speed, brake power, and normalized air-fuel ratio, lambda, with the aim of optimizing these parameters for brake thermal efficiency. The general trends of efficiency loss pathways with enleanment are found to be relatively insensitive to speed and load although the magnitude of the loss pathways changes. As the relative importance of the efficiency loss pathways changes with operating condition, so too does the lambda at which peak brake thermal efficiency occurs. The “peak efficiency lambda” was found to be at its leanest at low speed and high power where the influence of heat transfer is greatest and mechanical losses are minimized.

On the modeling of tensile index from larger data sets

The objective of this study is to analyze and foresee potential outliers in pulp and handsheet properties for larger data sets. The method is divided into two parts comprising a generalized Extreme Studentized Deviate (ESD) procedure for laboratory data followed by an analysis of the findings using a multivariable model based on internal variables (i. e. process variables like consistency and fiber residence time inside the refiner) as predictors. The process data used in this has been obtained from CD-82 refiners and from a laboratory test program perspective, the test series were extensive. In the procedure more than 290 samples were analyzed to get a stable outlier detection. Note, this set was obtained from pulp at one specific operating condition. When comparing such “secured data sets” with process data it is shown that an extended procedure must be performed to get data sets which cover different operating points. Here 100 pulp samples at different process conditions were analyzed. It is shown that only about 60 percent of all tensile index measurements were accepted in the procedure which indicates the need to oversample when performing extensive trials to get reliable pulp and handsheet properties in TMP and CTMP processes.

Optimal button arrangement of a percussion drill bit and its operating condition for improving drilling efficiency

This paper proposes an optimal button arrangement of a percussion drill bit and its operating condition to improve drilling efficiency. A new evaluation method is introduced for the button arrangement that utilizes the superimposed impact area, blank area, and drilling deviation moment as the quantitative indices to evaluate the impact of buttons on the rock surface. To determine the optimal button arrangement and its operating conditions, a progressive metamodel-based design optimization was conducted using the new evaluation indices as the analysis response, and then the optimal solution was determined through iteration. Consequently, all the button evaluation indices were reduced significantly and the impact areas were distributed uniformly under a specific operating condition. Additionally, the drilling performances of the optimal button arrangement were investigated according to the operating conditions to obtain the maximum drilling performance in terms of the drilling machine operation.

Symbolic Time-Series Analysis of Gas Turbine Gas Path Electrostatic Monitoring Data

The aero-engine gas-path electrostatic monitoring system is capable of providing early warning of impending gas-path component faults. In the presented work, a method is proposed to acquire signal sample under a specific operating condition for on-line fault detection. The symbolic time-series analysis (STSA) method is adopted for the analysis of signal sample. Advantages of the proposed method include its efficiency in numerical computations and being less sensitive to measurement noise, which is suitable for in situ engine health monitoring application. A case study is carried out on a data set acquired during a turbojet engine reliability test program. It is found that the proposed symbolic analysis techniques can be used to characterize the statistical patterns presented in the gas path electrostatic monitoring data (GPEMD) for different health conditions. The proposed anomaly measure, i.e., the relative entropy derived from the statistical patterns, is confirmed to be able to indicate the gas path components faults. Finally, the further research task and direction are discussed.

Dynamic analysis of gearbox behaviour in milling process: Non-stationary operations

Dynamic behaviour of gearbox transmitting power to milling tool in a milling process application is considered in this paper. The gearbox is subjected to variable cutting torque induced by the milling operation. This variability will lead to fluctuating speed. The dynamic behaviour of the system should be investigated according to this non-stationary operating condition. To achieve this objective, a simple model of motor-gearbox-milling tool system is developed. The influence of variable cutting torque on driving motor speed is taken into account. The gearmesh function which describes the meshing phenomena is modified according to this specific operating condition. Simulations of the dynamic behaviour of the gearbox show a simultaneous frequency and amplitude modulation. These modulations are highlighted using time frequency representation which is necessary to implement so that it is possible to achieve a correct diagnosis of the transmission. Simulations in presence of tooth crack defect confirmed the necessity to implement time frequency techniques to characterize time varying systems.

Temperature Peak Analysis and Its Effect on Absorption Column for CO2 Capture Process at Different Operating Conditions

The role of temperature is important in CO2 capture processes. Unfortunately, detailed analysis on the temperature profile of the absorption column is scarce in the literature. Important factors like CO2 capture capacity and corrosion rate directly depend on temperature of the column. Many side reactions such as solvent degradation, formation of stable salts, corrosion and reduction in CO2 capture are prominent at a higher temperature. This study reports a broad study on the temperature profile for CO2 capture process based on a detailed mathematical model, Kent–Eisenberg vapor–liquid equilibrium (VLE) model. This model is quite accurate in calculating CO2 capture for any specific operating condition. Results produced from Kent–Eisenberg VLE model are consistent with experimental data. This study reports temperature profiles of an absorption column for different operating conditions. Moreover, it was found that CO2 absorption is more effective at low and ambient temperatures than at high temperature confirmed by a peak temperature in all cases and in the lower section of the column, which is attributed to exothermic CO2 absorption in monoethanolamine. This temperature variation of the column will be helpful in designing CO2 capture plants.

Design of Compressor Blades Considering Efficiency and Stability Using CFD Based Optimization

To design a highly loaded axial transonic compressor several objectives need to be considered simultaneously. From an aerodynamic perspective, one of the major requirements is high efficiency at a specific operating condition where the fuel consumption is of main interest. Furthermore, the compressor needs to have a sufficient stall-margin along the entire flight envelope to ensure a stable operating range. This work is focused on creating an efficient design method which produces a trade-off between high stall margin and high efficiency. The design method is based on an automatic multiobjective optimization process divided into two steps. In the first step, 2D blade profiles are optimized where both efficiency and stall margin are considered. Once the optimization is finished the selected profiles are stacked together to be further optimized in 3D. When going to the second step, i.e. a 3D optimization, one can focus on a smaller set of design variables thereby reducing the time to get what is considered the optimal solution. The results show that it is possible to rate designs with potential of having high stall margin and high efficiency both in the 2D and 3D optimization. The main contribution in this work is the design method, which offers an efficient way of designing robust blades where the designer can decide the best trade off between stall margin at part speed and efficiency at the design point.