Combustion modelling of a dual fuel diesel – producer gas compression ignition engine

Abstract A thermodynamic tool for a dual fuel engine combustion simulation is presented in this work. The modelling represents an initial approach which aims at defining the performance of a single-cylinder diesel engine modified to work under dual fuel conditions and fuelled with producer gas as a gaseous fuel. The tool is based on the application of the first law of thermodynamics to closed systems. A novel approach using a triple Wiebe function has been implemented to describe and predict the heat release rate of dual fuel combustion; ignition delay has also been modelled with a methodology derived from the application of Prakash delay time model. Validation of the proposed combustion model has been realized according to experimental data already present in the recent scientific literature production. The calibrated model has been applied to the UNIBZ energy system set-up in order to predict its main performance characteristics; a future experimental campaign will be carried out to validate the predicted trends

a generalized theoretical methodology to forecast flow coefficient head coefficient and efficiency of pumps as turbines pats

Abstract Among the most used hydraulic machines in the small-scale hydropower sector, Pump-as-Turbine (PaT) technology is suitable for both practical and economical aspects. These machines are already profitably applied in remote and rural zones for electricity production and in energy recovery applications in both civil and industrial plants, like Water Distribution Networks (WDNs) and chemical plants. Several studies aimed to provide theoretical formulas able to forecast flow rate and head at the Best Efficiency Point (BEP) in turbine mode obtaining, however, contrasting results and a lack of generalization. In this work, a generalized theoretical methodology for forecasting the flow rate, the head and the efficiency of PaTs at their BEP is studied. Specific correlations between the non-dimensional parameters of PaTs in pump and in turbine mode are presented and discussed. The accuracy of the presented methodology is compared to the ones available in literature showing a good generalization capability and a significant improvement in forecasting the behaviour of the PaT, starting from the available performance characteristics in pump mode

analytical prediction models for evaluating pumps as turbines pats performance

Abstract: The hydropower sector is moving to the small-scale generation due to the exploitation of the majority water reservoirs with the aim of providing electrical energy in rural zones. Pump-as-Turbines (PaTs) is one of the most interesting technology due to their use for recovering energy in different industrial applications. Several studies aimed to study the performance of the tested PaTs and to describe their performance curves. The efficiency of these machines at their Best Efficiency Point (BEP) is comparable as much as the pump mode. In this work, a general analytical method for forecasting PaTs performance in turbine mode was investigated

effect of the regenerator efficiency on the performance of a micro gas turbine fed with alternative fuels

Abstract In this paper a validated in-house MATLAB© model was used to assess the behaviour of the Turbec T100 MGT when operated with alternative low lower heating value (LHV) fuels; moreover, the effect of the cycle humidification is assessed. In both the aforementioned cases, the flow rates through the turbomachines, their operating points, and the effectiveness of the recuperator might change and determine performance losses. In particular, the recuperator in a MGT is a crucial component that allows to achieve good thermodynamic performance, also in presence of low compression ratios, and its performance can strongly influence the final output of the machine. Therefore, the aim of the work is to evaluate the effect of the variation of the operating conditions on the performance of the recuperator and, therefore, of the whole MGT. The use of alternative fuels with low LHV and of steam injection shifts the operative points of the turbomachines without strongly affecting their isentropic efficiency; in general, compression ratio is reduced and the flow rate of the compressor is reduced. Therefore, attention must be paid for the compressor stall limit. The recuperator shows a slight variation of the temperature of the fluids, but a higher efficiency is recorded as the flow rate are typically reduced and a better heat recovery performance can be obtained

a predicting model of pats performance in off design operating conditions

Abstract The aim of this work is to propose a predicting model for evaluating Pump-as-Turbines' (PaTs) performance in off-design operating conditions. The predicting model has been derived from an elaboration of experimental test data available in literature on a set of several pumps operating in reverse mode. The performance prediction capability of the model has been compared with the results of the Computational Fluid Dynamics (CFD) analysis of a centrifugal pump running in turbine mode for several operating conditions. The comparison of the performance predicted by the model and the ones obtained with the numerical analysis has allowed to evaluate the effectiveness of the proposed model, highlighting its pros and cons and possible improvements. In general, it is possible to conclude that the proposed model is able to correctly assess the work and the efficiency of the studied PaT within errors in the range of few percentage points, especially for operating conditions not so far from the designed one

the effect of using diesel biodiesel bioethanol blends on the fuel feed pump of a small scale internal combustion engine

Abstract Biofuels represent an environmental-friendly and feasible alternative to fossil fuels for internal combustion engines. The use of diesel-biodiesel-bioethanol fuel blends (ternary blends) is one of the most interesting solutions in terms of fossil fuels substitution. They provide an improvement of exhausts gas emissions without any significant sacrifices in terms of energy-conversion efficiency. However, engine operation may be affected by the fuel substitution especially in the auxiliary mechanical fuel-feed systems, traditionally designed for low-density and high-viscosity fossil fuels. In the proposed work, two easy-to-use experimental-based mathematical models have been obtained by using the response surface method to assess the behaviour of fuel feed-pumps when biofuels blends are used. Density and mass flow-rates have been measured for several fuel mixtures and at different temperatures. The proposed equations are intended to be used as a practical tool, based on the optimal behaviour of the fuel feed-pump, in order to choose the best ternary fuel-mixture composition and/or predict/infer the engine performances under non-tested conditions (i.e., other mixtures' compositions and temperatures, however within the inquired domain)

A MILP algorithm for the optimal sizing of an off-grid hybrid renewable energy system in South Tyrol

The exploitation of renewable energy sources through sustainable energy technologies are taking the field to decrease the pollutions' emissions into the Earth's environment. To offset the limitations of such resources, hybrid energy systems are becoming fundamental in grid-connected applications as well as in off-grid ones. However, the unsteady behavior of renewable sources, such as Sun and Wind, complicates the prediction of the energy production's trend. The main factors and components involved in the design of hybrid energy systems are: (i) type of generators, (ii) their optimal number, (iii) storage systems and (iv) optimal management strategies. All of them have to be considered simultaneously to develop the optimal solution aimed at either reducing the dependence from fossil fuels or granting the supply of energy. In this paper, a methodology based on the Mixed Integer Linear Programming (MILP) is presented and adopted to meet the electric demand of a mountain lodge located in a remote area in South-Tyrol (Italy). The methodology has been developed implementing an algorithm through the Matlab ©software. The algorithm is capable of evaluating the optimal size of a hybrid off-grid Solar–Wind system with battery storage in order to replace an Internal Combustion Engine (ICE) fueled by diesel. Keywords: Hybrid off-grid energy system, Mixed integer linear programming, Matlab©, Optimization algorithm, Renewable energ

effects of viscosity on the performance of hydraulic power recovery turbines hprts by the means of computational fluid dynamics cfd simulations

Abstract Centrifugal pumps are used for increasing the energy content of a liquid: this technology is used in chemical processes with liquids having specific chemical and physical characteristics. Most of the processes are closed-loop, meaning that the liquid is reused after a proper physical or chemical washing treatment is performed. Therefore, the pressure of the liquid has to be decreased by means of a lamination valve or a Hydraulic Power Recovery Turbine (HPRT) with the advantage of recovering energy. HPRTs are generally tested in both pump and turbine modes using water as working fluid. The technical report ISO/TR 17766 indicates the procedure to evaluate the performance of centrifugal pumps handling viscous liquids by supplying correction factors with respect to water, but no indications are given in turbine mode. This work provides correction factors able to evaluate also the performance of HPRTs handling viscous fluids in turbine mode by varying the proposed formulae in the technical report. Computational Fluid Dynamics (CFD) simulations of two tested HPRTs are performed using, at first, water as working fluid for validating the experimental results and, subsequently, the SELEXOL® solvent. Results show that the original correction factors are still valid for the HPRT B that has a parameter B, which is the main one to be involved in the evaluation of the correction factors, lower than 1. A better accuracy, instead, is achieved by modifying the correction factors of the HPRT A, having a value of B higher than 1

Improving flexibility of industrial microgrids through thermal storage and HVAC management strategies

Abstract The increasing share of non-programmable renewable energy sources in national energy portfolios requires a high flexibility to balance demand and offer in energy markets. Demand side management programs and microgrids will play a key role in achieving flexibility on the demand side. This paper aims at presenting the increase of flexibility that can be achieved by an industrial microgrid. On field tests were carried out in an Italian industrial microgrid, where a set of load management strategies were implemented. These strategies aim at leveraging the thermal inertia of a building using both thermal energy storage and the HVAC system. Results show that the thermal energy storage can contribute to limit the peak cooling load by up to 40 kWe for three hours, while implementing a load shifting strategy using the HVAC system can provide a temporary reduction in power consumption of 20 kWe. Results also prove that it is possible to identify the effect of a load shifting strategy using electricity consumption data sampled with a 15-minutes granularity

use of diesel biodiesel bioethanol blends in farm tractors first results obtained with a mixed experimental numerical approach

Abstract The fuelling of internal combustion engines with biofuels has certainly many environmental and energetic advantages. These advantages are particularly effective in the agricultural sector, where an integrated biofuel supply-chain would further benefit the overall carbon balance. Unfortunately, there are also some drawbacks, mainly concerning the engine performances (lowering of the torque curve), but also environmental (possible raising of the NOx emissions). However, by appropriately mixing two biofuels with known opposite effects on the combustion process, it is theoretically possible to compensate the aforementioned disadvantages. In this work, some experiments were carried out in this direction by fuelling a farm tractor with four different fuel mixes; the collected data were processed through the Response Surface Methodology to obtain multi-parameter regression equations useful to identify the optimal fuel mixtures composition. Thanks to this approach, it was found that biodiesel has a positive effect on the torque, while the addition of bioethanol has a much bigger detrimental effect; on the contrary, bioethanol should be added to a mixture with a minimum of 8-12 % of biodiesel to get advantages in terms of NOx concentration reduction