Engine downsizing is a trusted method to reduce fuel consumption and pollution emitted from internal combustion Engines. In this method, Engine displacement volume is reduced while maintaining the same power/torque characteristics. However, there still exist several limitations to utilize this technology. In this paper, the naturally aspirated type of Iran national Engine (EF7-NA) is investigated for a possible downsized version. A one-dimensional Engine model equipped with a zero-dimensional two-zone combustion sub-model was developed and validated via experimental results for both natural aspirated and turbocharged Engine types. Then experimental and numerical studies were carried out for the primary concept, deactivation of one cylinder besides using a turbocharger. To overcome the concept shortages, especially in lower ranges of Engine speed, numerical studies were extended. Deployment of several turbochargers with different performance maps and different valve timing via a dual CVVT system were investigated. The results showed that there is a feasible method for EF7 Engine downsizing via a 3-cylinder type equipped with a modified turbocharger and valve timing. The maximum difference between base-Engine and downsized version torque is about 7% in low Engine speeds.

Certain stratified charge divided chamber Engines have a very small pre-chamber, equipped with a spark plug and a main chamber connected to the pre-chamber through nozzles. A theoretical model is presented in this research to predict ignition delay and initiation of combustion in the pre-chamber. It considers ame progress in the pre-chamber up to the point where the ame penetrates the main chamber through the connecting nozzles. Step by step calculations then continue in the main chamber and the mass fraction burned and the energy release rate is calculated. The process continues to the point where all the fuel is burned. At each step, due to a one degree rotation of the crank shaft, there is a change in the cylinder volume, due to the movement of the piston and, also, a change in the mole fraction burned, due to the burning of a fraction of the mixture. Considering heat transfer from the cylinder contents to its surrounding area, some important operating parameters, such as indicated power, indicated thermal efficiency, indicated septic fuel consumption, indicated mean elective pressure and volumetric efficiency, are predicted. Stepwise calculations also provide in-cylinder pressure-volume and pressure-crank angle diagrams, as well as the in-cylinder contents temperature variation with the crank position and concentration of species existing in the combustion products. Predicted values obtained by the present model are compared with corresponding experimental values available in the literature to evaluate the accuracy of the model. The comparison shows reasonable agreement between theoretical and measured values.

In this paper, a Dish-Stirling Concentrating Solar Power (CSP) system was examined in which the Engine works no longer as a receiver but is displaced away from it. In this arrangement it is necessary to adopt a heat transfer fluid capable of transmitting the useful power from the receiver to the hot spring in the Stirling Engine head.Various components of the system need designing and especially the heat exchanger in charge of transferring power to the Engine head thanks to the cooling of the fluid.The Dish-Stirling system under study includes a linear piston Stirling Engine of 4 kW total rated power (3 kW thermal and 1 kW electric). The minimum temperature for starting of the Engine is 190oC, while the maximum is 565oC. There are many innovative aspects of dish Concentrating Solar Power systems with Stirling Engine dislocated, for example, the possibility of using an increased number of Engines powered by a single greater dish and energy savings in the solar tracking system. The work covers the search for the most suitable fluids for the purpose, risks and benefit evaluation of fluids never usedpreviously in the field of solar concentration. The heat exchanger sizing was carried out examining different geometric configurations. The study was conducted using a computer and setting up thermo-fluid dynamics simulations in the ANSYS 14.5 environment. Finally, the results were tested and validated through a comparison study with empirical correlations found in the literature.

In this paper, the effect of the Intake Valve Deactivation (IVDA) on Engine performance is investigated in detail. Based on an optimization platform with Genetic Algorithm (GA) and Engine thermodynamic model, the characteristics of the Engine volumetric efficiency and pumping loss were studied under the cam-drive, Single Intake Valve (SIV) and Dual Intake Valves (DIV) operating modes, and the effect of the IVDA on the Engine fuel economy was revealed with taking the power consumption of the Electromagnetic Actuated Valvetrain (EAVT) system into consideration. Then, switch rules for the SIV and DIV mode was proposed, and the switching boundary conditions between them were confirmed. Finally, the optimal intake valve close timings for the EAVT system were obtained. Results show that, under the low speed conditions, the SIV mode has little influence on the Engine volumetric efficiency, while within the high speed conditions the effect of the IVDA on the volumetric efficiency is significant; compared with the traditional cam-drive valvetrain, the pumping loss of the EAVT Engine decreases significantly and shows unique characteristics due to the use of the EIVC strategy; with the use of the IVDA scheme, the energy consumption of the EAVT system reduces, but the Engine pumping loss increases in the meantime, both balance their influence on the Engine fuel economy. In general, the IVDA scheme is preferred if the Engine volumetric efficiency can be ensured, otherwise, the DIV mode takes priority over the SIV mode to maintain the Engine power performance

In the current paper, an aero-thermodynamic solver is employed to simulate the performance of innovative turbofan Engine layouts. The main aim is to investigate the key parameters such as thrust, specific fuel consumption (SFC), and Engine efficiency. The innovative Engine configurations are integrated with a base Engine referred to as Engine type 1. Engine type 2 is constructed by adding a secondary combustion chamber, while Engine type 3 incorporates a secondary inner bypass. Engine type 4 benefits from a secondary chamber and an inner bypass duct simultaneously. Flat rate analysis shows that Engine type 1 turbine inlet temperature can increase up to 1708.5 K under ISA+30 conditions. Additionally, the cruise thrust of Engine type 2 can be enhanced by up to 77% with a penalty of 20% increase in SFC. An optimum reference inner bypass ratio is achieved for Engine type 3, which simultaneously maximizes thrust and minimizes SFC. For Engine Type 4, when the sum of reference inner and outer bypass ratios equals 5.1, and the combustion chamber temperature matches that of the baseline Engine, it produces 17% higher cruise thrust than Engine type 1. Besides, Engine type 4 has a higher cruise thrust at M=0.8 among all Engine types. Engine type 2 and type 4 have higher flat rate performance (ISA+40). Engine type 3 has the highest overall efficiency, while Engine type 2 demonstrates the lowest efficiency.