Showing 5 results for Qasemian
M.h. Shojaeefard, P. Azarikhah, A. Qasemian,
Volume 7, Issue 2 (6-2017)
Abstract
Heat transfer in internal combustion engines is one of the most significant topics. Heat transfer may take place through thermal conduction and thermal convection in spark ignition engines. In this study, valve cover heat transfer and thermal balance of an air-cooled engine are investigated experimentally. The thermal balance analysis is a useful method to determine energy distribution and efficiency of internal combustion engines. In order to carry out experiments, a single cylinder, air-cooled, four-stroke gasoline engine is applied. The engine is installed on proper chassis and equipped with measuring instruments. Temperature of different points of valve cover and exhaust gases is measured with the assistance of K-type thermocouples. These experiments are conducted in various engine speeds. Regarding to the first law of thermodynamics, thermal balance is investigated and it is specified that about one-third of total fuel energy will be converted to effective power. It is also evaluated that for increasing brake power, fuel consumption will increase and it is impossible to prevent upward trends of wasted energies. In addition, it is resulted that, there is a reduction heat transfer to brake power ratio by increasing engine speed. Furthermore, it is found that, at higher engine speed, lower percentage of energy in form of heat transfer will be lost.
Dr. Ali Qasemian, Mr Pouria Azarikhah, Mr Sina Jenabi Haqparast,
Volume 8, Issue 2 (6-2018)
Abstract
The thermal balance analysis is a useful method to determine energy distribution and efficiency of internal combustion (IC) engines. In engines cooling concepts, estimation of heat transfer to brake power ratio, as one of the most significant performance characteristics, is highly demanded. In this paper, investigation of energy balance and derivation of specific heat rejection is carried out experimentally and numerically. Experiments are carried out on an air-cooled, single cylinder, four-stroke gasoline IC engine. The engine is simulated numerically and after validation with experimental data, the code is run to find out total and instantaneous thermal balance of engine. Results indicate that about one-third of fuel energy is converted to brake power and major part of energy is dissipated through exhaust and heat transfer. Experimental and numerical results show that by increasing engine speed, heat transfer to brake power ratio decreases. It is also observed that increasing engine speed leads to increase of exhaust power to brake power ratio. Finally two correlations for estimation of heat transfer and exhaust power to brake power ratios are obtained.
Hamed Saeidi Googarchin, Ali Qasemian, Mohammad Rouhi Moghanlou,
Volume 10, Issue 4 (12-2020)
Abstract
The primary objective of a brake disc is to absorb frictional heat during braking and dissipated it immediately by convection and radiation. However, during hard and repetitive brakings, thermal coning on brake disc generates surface hot spots which are responsible for the undesired accumulation of compressive stresses on the surface of the brake disc. These stresses would lead to disc cracking and finally failure of it. In the current paper, a coupled transient thermo-mechanical FE analysis of a heavy vehicle braking system is carried out in a way that thermal coning of the disc and surface hot spots and bands are recognizable. Braking condition is chosen from a standard for hard braking in trucks. Moreover, five additional braking actions with different severities are investigated to study the effects of braking severity on thermo-mechanical instability of brake discs. Comparison of numerical results of transient temperature during braking and cooling phases with experiment reveal a high accuracy of thermal prediction of this model. Also, the results show that thermal coning of brake disc is varied between 0.05 to 0.7 mm depending on braking severity and tangential location of the disc. Additionally, surface hot spots experience higher temperature gradients in higher decelerations. Finally, results show that circumferential compressive stresses during braking are the major component of thermal stresses and should be taken into account for life estimation analysis.
Dr Ali Qasemian, Mr Sina Jenabihaghparast, Mr Pouria Azarikhah,
Volume 12, Issue 3 (9-2022)
Abstract
In the current study, the hydrogen-addition influence on the performance of an SI engine using a gasoline-ethanol blend is investigated numerically. The simulation and validation of the model are carried out in order to evaluate the engine performance using conventional gasoline (G100) and the blend of gasoline and ethanol (G75E25). Furthermore, the hydrogen is added to the gasoline–ethanol blend (G50E25H25) to improve the engine thermal efficiency and reduce the amount of brake specific fuel consumption (BSFC) which leads to the reduction in greenhouse gas (GHG) emissions. The brake specific carbon dioxide (BSCO2) is also studied in this paper. Results show that the addition of hydrogen increases the brake power and thermal efficiency, moderates the BSFC, and decreases the maximum temperature of combustion chamber which reduces the production of greenhouse gases as well as BSCO2. In comparison with pure gasoline, by using G50E25H25, the maximum temperature of in-cylinder gas decreased by 12.55%, 10.82%, and 13.43% at 2000, 4000, and 6000 rpm, respectively. It is also evaluated that the lowest amount of BSCO2 is related to G50E25H25 in most of the engine speeds. The bio-fuel of G75E25 and pure gasoline are placed in next positions, respectively.
Ali Modarresi, Saman Samiezadeh, Ali Qasemian,
Volume 13, Issue 1 (3-2023)
Abstract
In recent years, the automotive industry has experienced a dramatic mutation in the develop ment of electric vehicles. One of the most important aspects of this type of vehicle is its thermal management. Among the various parts of an electric vehicle that are subjected to thermal management, the battery is of particular importance. Battery cell temperatures may exceed the allowable range due to continuous and high-pressure operation and various weather conditions, and this, in addition to performance, severely affects battery life. Therefore, the appropriate cooling system is essential. In this research, the most common methods of battery cooling are investigated. First, three-dimensional thermal analysis on the battery is performed using the computational fluid dynamics method in transient and steady-state phases. Then, the effect of changing the cooling flow rate on the maximum temperature of the battery cell as well as the temperature difference of the cells in the battery pack is investigated. The effect of changing inlet coolant temperature change on battery cell temperature distribution is also investigated. The results show that by increasing the flow rate from 0.5 to 1.2 liter per minute, the maximum temperature in the battery pack and the temperature difference between the cells decrease to 44.4 and 2.51 ° C, respectively. Also, by changing the temperature of the inlet coolant from 15 to 30 ° C, the maximum temperature in the battery pack increases up to 42.2 ° C and the temperature difference is negligible.
