Simplified calculation of friction mean effective pressure for fast simulation of fuel consumption

An environmentally friendly and economical ship operation can be accomplished through many different methods. Most of these approaches focus on technological solutions, e.g. internal engine measures in order to make the engine more eco-friendly, by changing engine control parameters for a better connection between propulsion system and ship, by usage of different fuels or fuel supplements or installation of exhaust gas-treatment systems. For many ships, it is neither efficient nor economically viable to replace or improve existing power generation or propulsion systems in order to improve efficiency or reduce emissions. Some of the internal measures used to reduce NOx-emissions like exhaust gas recirculation even lead to a higher fuel consumption. The vessel itself is still controlled by a crew and they should be kept in the loop to improve efficiency. Therefore optimal operational procedures for handling ships and specifically the outcome of engine manoeuvres is a substantial source for eco-friendly ship operations. The German research project MEmBran (Modelling Emissions and Fuel Consumption during Ship Manoeuvres) addresses especially the basis for optimising ship engine manoeuvres. It focusses on very detailed simulation of the processes of currently existing ship diesel engines, especially in a first step 4-stroke engines in order to implement models in wider comprehensive ship handling simulation software. As part of an existing planning and prediction software that can be used on board, it enables the watch keeping nautical officer and the shipping company to forecast and compare the fuel consumption of the ship for each manoeuvre. In order to reach this goal it is necessary to use fast calculating and stable methods that can be used to forecast the power output of the engine and the fuel consumption. This paper discusses an approach to calculate friction mean effective pressure.

Persistent, Extensive Channelized Drainage Modeled Beneath Thwaites Glacier, West Antarctica

Subglacial hydrology is a leading control on basal friction and the dynamics of glaciers and ice sheets. At low discharge, subglacial water flows through high-pressure, sheet-like systems that lead to low effective pressures. However, at high discharge, subglacial water melts the overlying ice into localized channels that efficiently remove water from the bed, thereby increasing effective pressure and basal friction. Recent observations suggest channelized subglacial flow exists beneath Thwaites Glacier, yet it remains unclear if stable channelization is feasible in West Antarctica, where surface melting is nonexistent and water at the bed is limited. Here, we use the MPAS-Albany Land Ice model to run a suite of over 130 subglacial hydrology simulations of Thwaites Glacier across a wide range of physical parameter choices to assess the likelihood of channelization. We then narrow our range of viable simulations by comparing modeled water thicknesses to previously observed radar specularity content, which indicates flat, spatially extensive water bodies at the bed. In all of our data-compatible simulations, stable channels reliably form within 100–200 km of the grounding line, and reach individual discharge rates of 35–110 m3 s−1 at the ice-ocean boundary. While only one to two channels typically form across the 200 km width of the glacier in our simulations, their high efficiency drains water across the entire lateral extent of the glacier. No simulations resembled observed specularity content when channelization is disabled. Our results suggest channelized subglacial hydrology has two consequences for Thwaites Glacier dynamics: (i) amplifying submarine melting of the terminus and ice shelf, while (ii) simultaneously raising effective pressure within 100 km of the grounding line and increasing basal friction. The distribution of effective pressure implied from our modeling differs from parameterizations typically used in large-scale ice sheet models, suggesting the development of more process-based parameterizations may be necessary.

Matrix gas flow through ‘impermeable’ rocks – shales and tight sandstone

The effective pressure sensitivity of gas flow through two shales (Bowland and Haynesville shales) and a tight gas sandstone (Pennant sandstone) was measured over the typical range of reservoir pressure conditions. These are low permeability rocks such as can be exploited as caprocks above reservoirs that might be developed to store compressed air, methane, hydrogen or to bury waste carbon dioxide, all of which may become important components of the forthcoming major changes in methods of energy generation and storage. Knowledge of the petrophysical properties of such tight rocks will be of great importance in such developments. All three rocks display only a small range in log10 permeability at low pressures, but these decrease at dramatically different rates with increasing effective pressure, and the rate of decrease itself decreases with pressure, as the rocks stiffen. The pressure sensitivity of the bulk moduli of each of these rocks was also measured, and used to formulate a description of the permeability decrease in terms of the progressive closure of narrow, crack-like pores with increasing pressure. In the case of the shales in particular, only a very small proportion of the total porosity takes part in the flow of gases, particularly along the bedding layering.

Characterization of the stability indices of a methanol induced partially premixed diesel dual fuel operation under varying split injection profiles: An experimental endeavour

The present investigation attempts to explore the prospects of the engine operational stability of a methanol induced partially premixed dual fuel operation under split injection strategy operating on a conventional single cylinder diesel engine coupled with a dedicated CRDI. The operation of such LTC regimes often deals with the stability concerns which are primarily characterized as the harshness of the operations and the non-repeatability of the combustion cycles. These two markers of operational stability have been mapped in this study through a comprehensive set of metrics of maximum pressure rise rate (ROPRmax) and Coefficient of Variation of Indicated Mean Effective Pressure (COVIMEP), Peak Pressure (COVPP) and Crank Angle of 50% mass fraction burn (COVCA50). The parametric investigation has been carried out at three different injection timings and pilot mass percentages at predefined methanol injection durations. The results have shown tremendous reductions in the non-repeatability of the combustion cycles and the harshness of the engine operation under split injection strategy, indicated by the lower scores of the stability indicators in comparison to the baseline single injection operation. Subsequently, the lowest scores of the maximum pressure rise rate and the Coefficient of Variation of indicated mean effective pressure, peak pressure and CA50 for the entire scope of investigation were registered as 0.62bar/CA, 0.75%, 0.48% and 1%, which were apparently observed as 65.5%, 86.36%, 94% and 53% lower than the corresponding scores registered in the baseline single injection operation.

Performance Small Spark Ignition Engine Using Producer Gas From Coal Gasification: Dual Fuel Operation

This study proposed a dual fuel operation of a mix of gasoline and producer gas from coal gasification on the spark ignition engine. The experiment was carried out on a constant load with variations in speed for single fuel operation of gasoline and dual fuel operation of a mix of gasoline and producer gas to see the influence on speed, torque, power, and braking (effective pressure). The power produced was compared to power produced by the single fuel of producer gas that has been reported in the literature. The result shows an increase of speed would increase torque, power, and braking (effective pressure) for single fuel operation of gasoline and dual fuel operation of a mix of gasoline and producer gas. The power operation of dual fuel of a mix of and gasoline and producer gas will decrease by about 10.9% compared to operation of single fuel of gasoline, and the power operation of the single fuel of producer gas will decrease by about 20% compared to the operation of the single fuel of gasoline. The maximum shaft power produced by dual fuel operation is 1.49 kW at a load of 5 kg and a speed of about 3,500 rpm.

Experimental Study About Water Saturation Influence on Changes in Reservoirs Petrophysical Properties

Experimental determination of the physical properties of rocks under conditions simulating in situ reservoir conditions is of great importance both for the calculation of reserves and for the interpretation of well logging data. In addition, it is also important for the preparation of hydrocarbon field development projects. The study of the processes of changes in the petrophysical properties of the reservoir under controlled conditions allows not only to determine their reliability but also to evaluate the dynamics of these changes depending on the temperature and pressure conditions of the reservoir and the water saturation of the rocks. In this work, an evaluation of the dependence of the physical properties of hydrocarbon reservoirs on their water saturation (Sw) was carried out. Residual water saturation (Swr) was created in the rocks and the properties of these rocks were compared at the states of partial (25 %) and complete water saturation (100 %). The changes in petrophysical parameters of partially water saturated rocks during the increase in effective pressure were studied and estimates of these changes were obtained. The results showed that when the effective pressure is increased, the Swr increases by an average of 6 % compared to atmospheric conditions. This is accompanied by an increase in the velocity of longitudinal (by 51.9 % on average) and lateral waves (by 37.1 % on average). As residual water saturation increases, effective permeability decreases for both standard and reservoir conditions, with, gas permeability decreasing for both dry samples (by 23 % on average) and samples with residual water saturation (effective permeability decreases by 27 % on average). HIGHLIGHTS Changes in physical properties of hydrocarbon reservoirs by determining physical properties (permeability, porosity, elastic, electrical, deformation strength) under the standard conditions and in physical modelling of reservoir conditions and processes Assessment of the effectiveness of water saturation on the physical properties of the reservoir Comparisons between the petrophysical properties of reservoir core samples in which the pore space is fully saturated with the reservoir fluid model and samples with residual water saturation Experimental determination of the physical properties of rocks under conditions simulating in situ reservoir conditions Estimation of the changes in petrophysical parameters of partial water-saturated rocks during the increase in effective formation pressure GRAPHICAL ABSTRACT

Influence of Effective Pressure on Percolation Rate of Coal

To study the role of the effective pressure on the percolation rate of coal, the effect of gas pressure, gas adsorption, and temperature on coal is taken into consideration comprehensively. Starting from the research direction of effective pressure and porosity, the coal body percolation rate and effective pressure equations considering the influence of temperature and gas pressure are established. The experiments on the percolation characteristics of raw coal are implemented under different effective pressure by using the independently developed thermos-solid-gas linking triaxial servosystem. The theoretical equation of the effective pressure and percolation rate of coal is calculated with the finite element software COMSOL, and the results obtained from the theoretical equation agree well with the experimental results. The results show that the percolation rate of coal gradually decreases with the growth of the effective pressure when the gas pressure and temperature are kept unchanged. Therefore, the results of the research are of certain reference value for the effective prevention of gas disaster.