نشریه تحقیقات موتور
پیاپی 62 (بهار 1400)

A modified multi zone model (MMZM) is developed for RCCI engines simulation. The CFD model is used to predict the evaporated n-heptane stratification to introduce as input to the MMZM to predict the SOC (start of combustion) and CA50 with sufficient accuracy. In the next step, a physic-base model is developed for SOC prediction and parameterized with 70 multi-zone results and validated using the same results and extra 25 experimental data. The model prediction average error for 95 steady-state operating conditions is below 1.2 CAD. Also, a modified fuel burn rate model is developed for predicting 50% of fuel mass burn and burn duration. Predicted results are in good agreement with all multi-zone results and operating conditions in prediction of both CA50 and burn duration. The MMZM can predict CA50 and burn duration with acceptable accuracy as the average error are about 1 CAD and 1.2 CAD.

Diesel engines in both automotive and industrial types are one of the most efficient engines in the world. Improving emissions and reducing fuel consumption is of great importance in the automotive industry. There are various methods in order to reduce emissions and fuel consumption of diesel engines. In this paper, at first it is tried to use the common rail fuel injection system to provide high pressure fuel behind the injectors and improve combustion inside the combustion chamber. It will decrease, soot, HC and CO emissions and fuel consumption while maintaining the performance of the OM355 diesel engine. It should be noted that by using the common rail system and better evaporation of fuel by the injection system and increasing the combustion efficiency, while reducing soot, HC and CO, the amount of NOX also increases. Therefore, after this stage, using a system to reduce the amount of NOX is necessary to create a trade-off between soot, HC, CO and NOX. So, with the use of Selective catalytic reduction (SCR) catalyst, which is one of the efficient technologies for controlling and reducing NOX, the amount of NOX in the post-combustion phase is significantly reduced. The experimental results of the OM355 engine test show the proper operation of the common rail and SCR systems.

Natural gas is known as one of the clean fuels the employment of which in vehicles results in the decrease of emissions and greenhouse gases. In addition, ammonia is known as one of the hydrogen carrier fuels the co-burning of which with natural gas leads to increment of combustion efficiency. In this paper, a numerical investigation is performed on the impacts of ammonia injection on the emission production and performance of a CNG-fueled EF7 engine. At first, the gaseous fueled EF7 engine has been modeled in AVL BOOST software and the main parameters of the engine at 6000 RPM and full load condition have been extracted and compared with experimental data for validation purpose. Then, the ammonia has been injected by 5% and 10% injection ratio by 4 injectors mounted on the air manifold into the engine, and the results of its injection into the engine are studied. By injection of ammonia, the engine power and brake mean effective pressure has been changed minimally. However, the in-cylinder temperature increased resulted in a decrement in CO and HC emissions up to 27% and 7.5%. On the other hand, the increase of in-cylinder temperature also led to an increase in NOx production which increased up to 43.4% for 5% ammonia injection and 118.7% for 10% ammonia injection.

In the present paper, molecular dynamics simulations of nano-wear were performed using a diamond nanoparticle with a diameter of 3 nm enclosed by two iron blocks. The whole process remained constant at 300 K and the slip velocity was selected for the upper and lower 100 m/s boundary layers. The study of the diamond lubrication mechanism shows that nanoparticles convert the sliding motion of friction surfaces into rolling motion. Based on the obtained results, the use of a diamond nanoparticle makes it possible to reduce the coefficient of friction from 0.24 to 0.05. To investigate the effect of pressure on the wear process, simulation of the wear process at constant temperature and velocity was performed under three different pressures of 350, 500, and 650 MPa. The results showed that nanoparticle does not deform under higher pressures and retain their spherical shape and improve the friction by creating a distance between the surfaces of friction compared to when there are no nanoparticles. However, in the presence of nanoparticles, the coefficient of friction increased with increasing pressure.

The powertrain is a vital part of any vehicle. In the meantime, the crankshaft is one of the important components of the system, by connecting rod, it takes the necessary combustion force from the pistons that have a linear motion and converts it into a rotational motion. Because crankshaft suffers from repetitive cycles in its activity, it is always subject to complex forces and boundary conditions. Therefore, identifying and how to apply, amount and direction of such components is very important. Lack of knowledge of the conditions governing the crankshaft will lead to the failure of the crankshaft and the failure of the entire transmission system. In this regard, for the first time, we sought to determine the stress conditions in the ITM 1500 tractor crankshaft that working in operational situation and to determine the stress concentration and places prone to fatigue and failure. We begin by evaluation of the source and amount of loads applied and how they affect the crankshaft. Then we drew the necessary 3D models in Siemens NX software. Finite element model analysis was performed by defining suitable material, solver, load and boundary conditions specifications in Abaqus software. Mesh was also done in ANSA specialized pre-processing software. The results obtained from finite element analysis were presented and reviewed. The amount and location of critical stress points in the entire model and the path defined on the main bearings were determined. In the end, the necessary conclusions were expressed using the obtained results.

In the present study, a new combined-cycle consisting of a turboprop engine equipped with a solid oxide fuel cell has been analyzed and investigated. In this configuration, after the air inlet, the air compressor, solid oxide fuel cell, combustion chamber, high-pressure turbine, free turbine, and outlet are considered, respectively. In this study, the cycle performance at different turbine inlet temperatures is investigated. Examination of the results shows that the integration of solid oxide fuel cells with turboprop engines will improve the efficiency of this engine. The results of this study show that adding solid oxide fuel cells to the turboprop engine will increase the efficiency of the whole system from 20% in the turboprop engine to 26% in the combined cycle. The results and diagrams also show that the combined cycle generates somewhat more thrust than a real turboprop engine and also provides 50 kWh of aircraft electrical energy.