This paper presents a thermo-economic analysis of a simple organic Rankine cycle (SORC) as a waste heat recovery (WHR) systems of a 2 MW stationary gas engine evaluating different working fluids. Initially, a systematic methodology was implemented to select three organic fluids according to environmental and safety criteria, as well as critical system operational conditions. Then, thermodynamic, exergy, and exergo-economic models of the system were developed under certain defined considerations, and a set of parametric studies are presented considering key variables of the system such as pump efficiency, turbine efficiency, pinch point condenser, and evaporator. The results show the influence of these variables on the combined power of the system (gas engine plus ORC), ORC exergetic efficiency, specific fuel consumption (∆BSFC), and exergo indicators such as the payback period (PBP), levelized cost of energy (LCOE), and the specific investment cost (SIC). The results revealed that heat transfer equipment had the highest exergy destruction cost rates representing 81.25% of the total system cost. On the other hand, sensitivity analyses showed that acetone presented better energetic and exergetic performance when the efficiency of the turbine, evaporator, and condenser pinch point was increased. However, toluene was the fluid with the best results when pump efficiency was increased. In terms of the cost of exergy destroyed by equipment, the results revealed that acetone was the working fluid that positively impacted cost reduction when pump efficiency was improved; and toluene, when turbine efficiency was increased. Finally, the evaporator and condenser pinch point increased all the economic indicators of the system. In this sense, the working fluid with the best performance in economic terms was acetone, when the efficiency of the turbine, pinch condenser, and pinch evaporator was enhanced.

This manuscript presents an advanced exergo-economic analysis of a waste heat recovery system based on the organic Rankine cycle from the exhaust gases of an internal combustion engine. Different operating conditions were established in order to find the exergy destroyed values in the components and the desegregation of them, as well as the rate of fuel exergy, product exergy, and loss exergy. The component with the highest exergy destroyed values was heat exchanger 1, which is a shell and tube equipment with the highest mean temperature difference in the thermal cycle. However, the values of the fuel cost rate (47.85 USD/GJ) and the product cost rate (197.65 USD/GJ) revealed the organic fluid pump (pump 2) as the device with the main thermo-economic opportunity of improvement, with an exergo-economic factor greater than 91%. In addition, the component with the highest investment costs was the heat exchanger 1 with a value of 2.769 USD/h, which means advanced exergo-economic analysis is a powerful method to identify the correct allocation of the irreversibility and highest cost, and the real potential for improvement is not linked to the interaction between components but to the same component being studied.

The present study aims to analyze the influence of the geometric profile of the compression ring on the tribological properties of the lubricant. Additionally, the influence of the rotation speed and the engine load on the state of the lubricant is evaluated. For this study, a single-cylinder diesel engine is taken as the basis, from which a CAD model of the combustion chamber-piston assembly was made. In addition, the conditions in the cylinder chamber were analyzed when the engine operates at a rotation speed of 3000, 3300, 3600, and 3900 rpm, and a load of 1.5, 3.0, 4.5, and 6.0 N. The calculations were developed using the OpenFOAM® simulation software. The results obtained show that changes in the geometric profile of the ring can contribute to reducing the hydrodynamic friction force by 13% and the friction force caused by roughness by 61%. This implies a decrease in the power lost by friction. In general, the modification of the geometric profile allowed a reduction of 21% in the lost power associated with friction. Additionally, it was observed that the shape of the profile allows to reduce the pressure in the lubricant by 65% and obtain a greater thickness of the lubrication film. On average, an increase of 300 rpm and 1.5 N in the speed and load of the engine causes the friction force and power losses to increase by 45% and 10%. The above results imply that the geometric profile of the compression ring can improve tribological performance in the engine, allowing a reduction in fuel and better lubricant performance.

This article presents a multivariable optimization of the energy and exergetic performance of a power generation system, which is integrated by a supercritical Brayton Cycle using carbon dioxide, and a Simple Organic Rankine Cycle (SORC) using toluene, with reheater (S À CO RH 2 À SORC), and without reheater (S À CO NRH 2 À SORC) using the PSO algorithm. A thermodynamic model of the integrated system was developed from the application of mass, energy and exergy balances to each component, which allowed the calculation of the exergy destroyed a fraction of each equipment, the power generated, the thermal and exergetic efficiency of the system. In addition, through a sensitivity analysis, the effect of the main operational and design variables on thermal efficiency and total exergy destroyed was studied, which were the objective functions selected in the proposed optimization. The results show that the greatest exergy destruction occurs at the thermal source, with a value of 97 kW for the system without Reheater (NRH), but this is reduced by 92.28% for the system with Reheater (RH). In addition, by optimizing the integrated cycle for a particle number of 25, the maximum thermal efficiency of 55.53% (NRH) was achieved, and 56.95% in the RH system. Likewise, for a particle number of 15 and 20 in the PSO algorithm, exergy destruction was minimized to 60.72 kW (NRH) and 112.06 kW (RH), respectively. Comparative analyses of some swarm intelligence optimization algorithms were conducted for the integrated S-CO 2 -SORC system, evaluating performance indicators, where the PSO optimization algorithm was favorable in the analyses, guaranteeing that it is the ideal algorithm to solve this case study.

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The objective of the present investigation is to analyze the tribological performance between the union of the cylinder liner and the compression ring under the influence of surface texturing and different lubrication boundary conditions. The analysis is carried out by developing a numerical model, which involves hydrodynamic pressure, lubrication film thickness, textured surface, dynamic forces, and lubrication boundary conditions (starved lubrication and fully flooded lubrication). MATLAB® software (The MathWorks Inc., Natick, MA, USA) is used to solve the equations developed. The results show that the application of a textured surface on the cylinder liner allows obtaining a reduction of 20% and 5% in the asperity contact force and in the total friction force. Additionally, the textured surface allows for a 4% increase in MOFT. In this way, it is possible to reduce the power loss. The implementation of a boundary condition of fully flooded lubrication produces an overestimation in the total friction force due to the greater prominence of the lubrication film. Implementing a textured surface in the ring profile is an alternative way to reduce power loss. The results show that this alternative allows an 8% reduction in power loss.

The problem of climate change and the reduction of fossil fuels has motivated the development of research focused on improving the efficiency of internal combustion engines. This research proposes a methodology based on mathematical models to determine the energy losses caused by auxiliary systems and friction processes in the engine. Therefore, models are proposed for calculating the energy losses in fuel injection, lubrication, and cooling system. In the same way, models are proposed for the energy losses due to friction in the piston, valve train, and bearings. Experimental tests are carried out on a single-cylinder diesel engine under different operating conditions to validate the proposed models. The results showed that the energy losses of the fuel injection, lubrication, and coolant system are equal to 0.61%, 0.30%, and 0.31% of the chemical energy of the injected fuel. In the case of the energy losses by friction processes, the piston, valve train, and bearings represent 5.47%, 1.34%, and 1.85% of the fuel energy, respectively. Additionally, the proposed model allows estimating the minimum lubrication film present in the piston, valve train, and bearings, which in the particular case of the present study were 0.63 µm, 0.10 µm, and 0.57 µm, respectively. In general, the methodology developed in the present work stands as a robust tool to evaluate the modifications and/or designs of auxiliary systems and friction processes to reduce the energy losses and protect the system from wear caused by lubrication problems. Additionally, the methodology allows evaluating the effect of different types of fuels on the lubrication conditions of the piston and the crankshaft bearings.