Showing 4 results for karami
Mohsen Esfahanian, Mohammad Saadat, Parisa Karami,
Volume 8, Issue 3 (9-2018)
Abstract
Hybrid electric vehicles employ a hydraulic braking system and a regenerative braking system together to provide enhanced braking performance and energy regeneration. In this paper an integrated braking system is proposed for an electric hybrid vehicle that include a hydraulic braking system and a regenerative braking system which is functionally connected to an electric traction motor. In the proposed system, four independent anti-lock fuzzy controllers are developed to adjust the hydraulic braking torque in front and rear wheels. Also, an antiskid controller is applied to adjust the regenerative braking torque dynamically. A supervisory controller, is responsible for the management of this system. The proposed integrated braking system is simulated in different driving cycles. Fuzzy rules and membership functions are optimized considering the objective functions as SoC and slip coefficient in various road conditions. The simulation results show that the fuel consumption and the energy loss in the braking is reduced. In the other hand, this energy is regenerated and stored in the batteries, especially in the urban cycles with high start/stop frequency. The slip ratio remains close to the desired value and the slip will not occur in the whole driving cycle. Therefore, the proposed integrated braking system can be considered as a safe, anti-lock and regenerative braking system.
Dr Amirhasan Kakaee, Mr Mohammadreza Karami,
Volume 9, Issue 2 (6-2019)
Abstract
In this study, modeling of a fuel jet which has been injected by high pressure into a low-pressure tank are investigated. Due to the initial conditions and the geometry of this case and similar cases (like CNG injectors in internal combustion engines (ICE)), the barrel shocks and Mach disk are observed. Hence a turbulence and transient flow will be expected with lots of shocks and waves. According to the increasing usage of this type of injectors in ICE, more studies should be conducted to find the most accurate and beneficial models for modeling this phenomenon.
In order to find an accurate and beneficial turbulence model ,in this study, three Reynolds-averaged Navier–Stokes (RANS) turbulence models (SST k-ω, RNG and standard k ) and large eddy simulation (LES) turbulence model were compared by the fuel jet characteristics in three regions (outlet of the nozzle, at Mach disk and at the downstream of the flow). Although the LES model needs more time for each test, the results are more reliable and accurate. On the other hand, RANS turbulence models have lots of errors (more than 10 percent) especially for predicting the characteristics of fuel jet at Mach disk.
Saeed Chamehsara, Mohammadreza Karami,
Volume 9, Issue 4 (12-2019)
Abstract
Changing various parts of different types of engines in the maintenance phase was always a remarkable question. Purpose of the present study is identifying the performance and emissions of a diesel-fueled engine (OM457) before and after replacing connecting rod and crankshaft with another engine (OM444) in the same engine family.
At the first step, a solid model was made then some CFD analyses were done and, results were compared with previous studies for validation after that in the CFD modeling the impact of these parts replacement were observed, and the performance and emissions of this engine were compared with data before replacements.
As the result of these replacements, compression ratio and performance were decreased. HC and CO were increased due to lower air-fuel ratio, and NOX was decreased because of the lower temperature of in cylinder. Lowering the CR of a diesel engine will reduce the NOx emission numerously but the increase in other emissions will be slight. So for the environment issues lowering the CR will be a practical and low cost method.
Mr. Saeed Chamehsara, Mr. Mohammadreza Karami,
Volume 11, Issue 4 (12-2021)
Abstract
Many efforts have been made to increase power and reduce emissions from internal combustion engines. For this purpose, the internal combustion engine subsystems are examined via many studies, and the effective parameters in each of them are analyzed. One of these subsystems is the air inlet and outlet to the combustion chamber, the most important part of which is the manifold. In the present study, using one-dimensional modeling of the OM457 heavy diesel engine in the GT SUITE software environment, the effect of geometric parameters of cylinder runner’s length - cylinder runner’s transverse distance as well as plenum’s depth on the performance and the emissions of this engine has been investigated. During this study, it was concluded that increasing the volume of the plenum not only improves the engine’s output but also reduces the emission of pollutants produced. Also, increasing the length of the cylinder runner increased the engine power. The change in the transverse distance of the cylinder runners did not have a significant effect on the power and pollutants of the sample engine. It was also observed that in similar geometric changes, the effect of changing the input manifold is significantly greater than the output manifold level.
