Automotive Science and Engineering

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In this study, a numerical simulation using the CFD software, FLUENT, has been conducted to examine the effect of various shapes of the venturi component sections in order to find the optimum venturi specifications to increase the EGR rate with minimum pressure loss at the part load operation range. The CFD results reveal that the venturi should be precisely optimized to introduce the required amount of EGR to the engine manifold. Then, the optimum venturi was manufactured, and it was installed on the engine intake system. By using the optimum Venturi EGR system instead of original system the 26% increase in EGR flow rate to the engine manifold is observed. In the second part of the paper, an experimental investigation was carried out on a “Lister 8-1” dual fuel (diesel – natural gas) engine to examine the simultaneous effect of inlet air pre-heating and EGR on performance and emission characteristics of a dual fuel engine. The use of EGR at high levels seems to be unable to improve the engine performance at part loads, however, it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency, resulting in reduced levels of both UHC and NOx emissions. CO and HC emissions were reduced by 24% and 31%, respectively. The NOx emissions were decreased by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.

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Nitrogen oxides (NOx) contribute to a wide range of environmental effects including the formation of acid rain and destroy ozone layer. In-cylinder high temperature flame and high oxygen concentration are the parameters which affect the NOx emissions. The EGR system is a very effective way for reducing NOx emission from a diesel engine (via reduction of these parameters), particularly at the high load of engine operation condition. In this study, the influence of EGR on diesel engine combustion, NOx/PM emissions, brake specific fuel consumption (BSFC), engine thermal efficiency, cylinder pressure and heat release rate (HRR) are analyzed and presented. The experiments have been conducted on a turbocharged DI diesel engine under full load condition at two different injection timings in order to distinguish and quantify some effects of Hot and Cooled EGR with various rates on the engine parameters. Experimental results showed that increase of EGR rate has a negative effect on air-fuel ratio. For a premixed combustion at constant boost pressure, ignition delay is increased leading to retardation of all combustion process, a low HRR peak and reduce of in-cylinder peak temperature. Using of Hot EGR reduces NOX emissions whereas PM emissions are increased. The advance of injection timing resulted in the reduction PM while both NOX emissions and fuel consumption were increased. The use of cooled EGR was more effective compared to the hot EGR. As a result, the EGR temperature has no significant impact on NOx emissions. With increasing EGR rate, unequal EGR distribution was increased in inlet port of cylinders while the reducing EGR temperature (cooled EGR) improved its distribution among the engine cylinders and decreased the EGR cylinder-to-cylinder variations.

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Although, the Stirling engine (SE) was invented many years ago, the investigation on SE is still interesting due to variety of energy resources can be applied to power it (solar energy, fossil fuel, biomass and geothermal energy). In this paper, the thermodynamic cycle of SE is analyzed by employing a new analytical model and a new method is presented to evaluate output power and efficiency of real engines. Using the correcting functions; represent more accurate results for known Schmidt equations respect to adiabatic model. So without need to employing numerical methods and iterative solver programs, analogous results with accuracy and correctness of open-form solution-adiabatic method is obtained. The modeling of results of two methods is done by Non-linear Multiple Regression and new equations based on Schmidt equations with new correctness factors is presented. The correctness factors are function of structural and operational characteristics of engine.  Moreover, available output data of GPU-3 SE was compared. These comparisons show good agreement, indicating that the model is an appropriate method for modeling of SE outputs.

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The Global Positioning System (GPS) and an Inertial Navigation System (INS) are two basic navigation systems. Due to their complementary characters in many aspects, a GPS/INS integrated navigation system has been a hot research topic in the recent decade. The Micro Electrical Mechanical Sensors (MEMS) successfully solved the problems of price, size and weight with the traditional INS. Therefore they are commonly applied in GPS/INS integrated systems. The biggest problem of MEMS is the large sensor errors, which rapidly degrade the navigation performance in an exponential speed. Three levels of GPS/IMU integration structures, i.e. loose, tight and ultra tight GPS/IMU navigation, are proposed by researchers. The loose integration principles are given with detailed equations as well as the basic INS navigation principles. The Extended Kalman Filter (EKF) is introduced as the basic data fusion algorithm, which is also the core of the whole navigation system to be presented. The kinematic constraints of land vehicle navigation, i.e. velocity constraint and height constraint, are presented. A detailed implementation process of the GPS/IMU integration system is given. Based on the system model, we show the propagation of position standard errors with the tight integration structure under different scenarios. A real test with loose integration structure is carried out, and the EKF performances as well as the physical constraints are analyzed in detail.

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In this paper, a computational in-cylinder analysis of HCCI diesel engine was carried out using IC Engine FORTE (ANSYS 18.2) software package. The analysis used pre-defined industry standard CHEMKIN format for specifying a chemical reaction mechanism during the combustion duration. The investigation was carried out for the effects of various EGR mass percentages on the thermal and emission characteristics of a diesel engine running on HCCI mode of combustion. It was observed that an increase in EGR concentration resulted in the decrease in peak in-cylinder pressure and temperature and it was also found that when the EGR rates were increased beyond 75% there was no combustion happening within the cylinder. A considerable decrease in the NO_x emissions was found with an increase in EGR mass percentage with almost negligible values when the EGR rates were increased beyond 50%, however there was a slight increase in un-burnt hydrocarbons.

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In this paper, a new version of multi-objective differential evolution with dynamically adaptable mutation factor is used for Pareto optimization of a 5-degree of freedom vehicle vibration model excited by non-stationary random road profile. In this way, non-dominated sorting algorithm and crowding distance criterion have been combined to differential evolution with fuzzified mutation in order to achieve multi-objective meta-heuristic algorithm. To dynamically tune the mutation factor, two parameters, named, number of generation and population diversity are considered as inputs and, one parameter, named, the mutation factor as output of the fuzzy logic inference system. Conflicting objective functions that have been observed to be optimally designed simultaneously are, namely, vertical seat acceleration, vertical forward tire velocity, vertical rear tire velocity, relative displacement between sprung mass and forward tire and relative displacement between sprung mass and rear tire. Furthermore, different pairs of these objective functions have also been chosen for bi-objective optimization processes. The comparison of the obtained results with those in the literature unveils the superiority of the results of this work. It is displayed that the results of 5-objective optimization subsume those of bi-objective optimization and, consequently, this achievement can offer more optimal choices to designers.