Open dual cycle with composition change and limited pressure for prediction of miller engines performance and its turbine temperature

An improved thermodynamic open Dual cycle is proposed to simulate the working of internal combustion engines. It covers both spark ignition and Diesel types through a sequential heat release. This study proposes a procedure that includes (i) the composition change caused by internal combustion, (ii) the temperature excursions, (iii) the combustion efficiency, (iv) heat and pressure losses, and (v) the intake valve timing, following well-established methodologies. The result leads to simple analytical expressions, valid for portable models, optimization studies, engine transformations, and teaching. The proposed simplified model also provides the working gas properties and the amount of trapped mass in the cylinder resulting from the exhaust and intake processes. This allows us to yield explicit equations for cycle work and efficiency, as well as exhaust temperature for turbocharging. The model covers Atkinson and Miller cycles as particular cases and can include irreversibilities in compression, expansion, intake, and exhaust. Results are consistent with the real influence of the fuel-air ratio, overcoming limitations of standard air cycles without the complex calculation of fuel-air cycles. It includes Exhaust Gas Recirculation, EGR, external irreversibilities, and contemporary high-efficiency and low-polluting technologies. Correlations for heat ratio gamma are given, including renewable fuels

Prosessisimulointityökalun kehittäminen pienelle kaasuturbiinille

Power consumption is increasing in the next decades and demands to fulfill this need are expected to turn towards cleaner and more efficient energy production. While renewables are expected to increase, their growth rate cannot compensate for the increase in power consumption alone, and gaseous fuels, such as natural gas, are expected to play a big role along renewables in this transition to produce energy cleaner and more efficiently. Demand for efficient and exact energy also drives decentralization, meaning that energy can be produced where demand is, to fulfill needs precisely and quickly. Many industrial applications also require process heat and with decentralized combined heat and power production, great efficiency increase is possible. Small gas turbines excel in this type of combined heat and power production with versatile fuels, also including natural gas. With this current continuing trend in the energy market, increase in the gas turbine installations can be expected. Interest towards gas turbines increases the importance of gas turbine performance models. In off-design conditions, performance is significantly affected by the load and ambient conditions. With accurate models, the performance of engines can be predicted for each application and designing costs and time can be reduced. During operation, drive can be optimized to reach higher efficiencies and with engine monitoring, maintenances can be planned to be condition-based, not predictive based. In this master’s thesis, performance prediction model was created for intercooled and recuperated gas turbine process with two spools, both spools including generator, compressor and turbine. The model was requested by the company to replace currently used model, with one which could better correspond to the company’s need. The developed model was steady-state, full range performance model which used Newton-Raphson iteration. The developed model was compared to old model and results were in-line. The new model was as requested by the company excluding some attributes which could not be included in the scope of this thesis but will be added to the model later

Carnot Cycle and Heat Engine Fundamentals and Applications II

This second Special Issue connects both the fundamental and application aspects of thermomechanical machines and processes. Among them, engines have the largest place (Diesel, Lenoir, Brayton, Stirling), even if their environmental aspects are questionable for the future. Mechanical and chemical processes as well as quantum processes that could be important in the near future are considered from a thermodynamical point of view as well as for applications and their relevance to quantum thermodynamics. New insights are reported regarding more classical approaches: Finite Time Thermodynamics F.T.T.; Finite Speed thermodynamics F.S.T.; Finite Dimensions Optimal Thermodynamics F.D.O.T. The evolution of the research resulting from this second Special Issue ranges from basic cycles to complex systems and the development of various new branches of thermodynamics

Mechanical Engineering: Prospectus for Day and Evening Classes 1951-52

Courses and timetables for the College of Technology, Bolton Street, Dublin 1

Mechanical Engineering: Prospectus for Day and Evening Classes 1950-51

Courses and timetables for the College of Technology, Bolton Street, Dublin 1

Real-time friction torque estimation on a diesel engine using the crankshaft speed fluctuation

Under the pressure of stricter regulations on pollutant emissions and the desire of users for lower fuel consumption and more comfortable driving, engine control based on torque has been developed. To provide an accurate estimate of effective torque, friction losses must be modeled. The details of a model that predicts the total instantaneous friction torque for compression ignition engines are described. The model is based on a combination of the dynamic model of the crankshaft and the thermodynamic model. The total instantaneous friction torque is determined using the instantaneous measurements or numerical predictions of the gas pressure in the combustion chamber, the rotational speed of the crankshaft and the load torque. The experimental data and the numerical simulation results were compared. The comparison between the different variables shows a good agreement between the simulation and the experimental results

3D CFD Combustion Simulation of a Four-Stroke SI Opposed Piston IC Engine

The reciprocating IC engine plays an important role in the world transport, with very few alternative configurations having commercial success. In light aircraft applications where low vibrations are crucial, boxer engines have predominated. The rising cost of fuel and the growth of public concern over pollutant emissions has led to an increased interest in alternative designs. In recent years, with the uprising of new technologies, research techniques and materials, the OP engine has emerged as a viable alternative to the conventional IC engine in some applications including in the aeronautical field. This study presents a numerical analysis of the combustion process of octane-air mixture in a four-stroke SI opposed piston engine. The model used in the simulations represents the internal volume of the cylinder of UBI/UDI-OPE-BGX286 engine. The simulation was run in Fluent 16.0 software, the species transport model was chosen to model combustion from the available in Fluent, and three different engines speeds were simulated: 2000RPM, 3200RPM and 4000RPM. Regarding the results obtained from the three CFD simulations, the overall behavior and properties of the in-cylinder flow and the obtained graphics were considered acceptable.O motor alternativo de combustão interna desempenha um papel importante no mundo dos transportes, existindo ainda poucas configurações alternativas com sucesso comercial. Relativamente a aplicações em aeronaves ligeiras, onde as baixas vibrações são de extrema importância, os motores boxer têm predominado o mercado. O aumento do custo do combustível e o aumento da preocupação do público com as emissões de poluentes levaram a um maior interesse em novas alternativas. Nos últimos anos, com o surgimento de novas tecnologias, técnicas de pesquisa e materiais, o motor de pistões opostos surgiu como uma alternativa viável ao motor convencional de combustão interna em algumas aplicações, inclusive na área aeronáutica. Este estudo apresenta uma análise numérica do processo de combustão da mistura de octano-ar num motor de faísca a quatro tempos e de pistão oposto. O modelo utilizado nas simulações representa o volume interno do cilindro do motor UBI / UDI-OPE-BGX286. A simulação foi executada no software Fluent 16.0, dos modelos disponíveis no Fluent o modelo de transporte de espécies foi escolhido para modelar a combustão, e três diferentes velocidades de motor foram simuladas: 2000RPM,3200RPM e 4000RPM. Em relação aos resultados obtidos nas três simulações CFD, o comportamento geral e as propriedades do fluxo no cilindro e os gráficos obtidos foram considerados aceitáveis

Homogeneous Lean Combustion in Downsized Spark-Ignited Engines

Emissions of greenhouse-gasses and noxious compounds from internal combustion engines propelling personal transportation vehicles is an imminent issue in the society. Therefore, it is vital to find means of reducing these emissions to decrease the impacts of transportation. Despite the current rapid electrification of the light duty vehicle fleet, it is expected that there will still be a substantial share of vehicles, produced and sold, that are propelled either solely or partly by combustion engines in the next decades to come. An advantage of combustion engines is that they consume hydrocarbon fuels, which are energy dense and can be produced from renewable sources enabling elimination of net carbon emissions. These fuels can be distributed using the current infrastructure, allowing for a fast transition into a low-carbon transportation system. The sources of renewables are however limited, and production of renewable fuels requires energy, which is why the fuel efficiency of combustion engines is key.This thesis addresses the need for reduced emissions from personal transportation vehicles by investigating homogeneous lean combustion in downsized spark-ignited engines as a means of improving combustion engine fuel efficiency. Lean combustion offers substantial efficiency improvements to the current already well-developed combustion systems. However, historically, it has been proven difficult to achieve robust lean combustion that achieves both efficiency improvements and sufficiently low emissions of nitrogen oxides. In this thesis, the focus has been to investigate the potentially synergetic combination of high engine loads above 10 bar brake mean effective pressure, a common attribute of downsized engines, and lean combustion. The idea is that lean combustion reduces knocking combustion, a harmful event that limits engine efficiency due to cylinder pressure limitations. Simultaneously, it is hypothesized that higher engine loads will lead to faster and more stable combustion, allowing important reductions in nitrogen oxides.Using engine experiments and simulations, homogeneous lean combustion has been investigated. From the experiments it could be concluded that lean combustion can be sustained at high loads. One of the world’s first two-stage turbochargers designed solely for lean combustion was utilized for this purpose and found to be successful. However, it was discovered that lean combustion does not eliminate knocking combustion completelyKeywords: engine, efficiency, emissions, lean, combustion, nor did high load operation eliminate cyclic dispersion of combustion, which imposes limitations. Using improved in-cylinder charge motion and alternative fuels, these limitations can be mitigated, allowing for stable, efficient, low nitrogen oxide high load lean combustion