نشریه تحقیقات موتور
پیاپی 56 (پاییز 1398)

Turbochargers are used to increase engine manifold air pressure. Control of intake manifold pressure is crucial issue which is done through the speed control of turbocharger, but since it is difficult to directly control the speed of the turbocharger, it is done indirectly through a gate that called the waste gate, which is located in the engine outlet and turbocharger’s turbine inlet. One of the most common control methods for control of turbocharger is the gain scheduling control. This method design in parameter look-up table, supervisor and system subsection to control turbocharger performance. The performance of control loop can be evaluated with accuracy of considered model and designed controller. In this paper, the  engine model with the turbocharger has been created in the GT-POWER software, then, by defining the input and output parameters in the GT-POWER model, the model is coupled with MATLAB software to controller design. In the next step, two methods have been developed to design the controllers for the gain scheduling control method. Eventually, effectiveness of turbocharger control using gain scheduling control is shown.

Transverse vibration of the serpentine belt is effective at noise and durability of it. Therefore, understanding of this phenomenon and studying effective parameters can be used in the process of reducing belt noise and increasing life time. In this paper, transverse vibration of serpentine belt is measured experimentally and analyzed. In the implementation test steps, the displacement of the belt in two positions has been measured. Then, the time signals were transformed to frequency domain. It is derived and observed that the belt vibration is synchronous with engine speed, accordingly order analysis is selected to analysis the vibration signal. Results show that the natural frequency of serpentine belt in the region between A/C compressor and crankshaft pulley changes due to A/C compressor loading, but this parameter is not affected by engine load variations. In the area between automatic tensioner and idler, natural frequency is constant regardless of A/C compressor on-off condition and engine load changing. In all engine rotating speeds, the dominant frequencies are highly closed to the natural frequencies. In some engine speeds, vibration amplitude is high and the frequency of these points are proportionally equal to 2, 3, 4 and other orders of engine speed.

Muffler is a part of the vehicle exhaust system that absorb or reflect sound waves to reduce exhaust noise. One of the most important determinants of a muffler performance is the amount of attenuation that has on its input wave; this parameter is known as sound transmission loss. Four - mic standard test is one way to determine this parameter which is used in this paper. In this study, a test device was developed to measure the level of Sound Transmission Loss. In order to validate the performance of the test apparatus and its results, sound transmission loss is calculated for real sample using GT-Power software and theoretical calculations. The sound transmission loss test machine can be used to assess mufflers used in the car and other industries. In general, the main purpose of this research is to construct the sound transmission loss test device and develop the computational code for it and validate the performance of the test system.

Internal Combustion Engine Vehicles or ICEVs play a major role in air pollution for big cities like Tehran. Catalyst converters manage to contain much of the generated pollution from combustion and are considered as a mandatory part of any vehicle. Manufacturer guidelines clarify a certain mileage for catalyst to be regarded as completely degraded and thus unable to contain harmful gasses from combustion. In this paper we test the theory that catalyst degradation is greatly affected by driving condition by using kinematic simulation of vehicle in different driving cycles. Catalyst degradation parameters are derived for the reference driving cycle (NEDC) and then developed accordingly for other driving conditions. The vehicle model with degradation sub-model is then utilized for investigating different scenarios of replacing old catalyst with a new one. Results clearly support the idea that driving cycles greatly affect the degradation age of 3-way catalysts and vehicle emissions are increased up to 5 times by using catalyst after its age limit. For Tehran driving cycle, 75K kilometers appears to be the aging limit. Authors conclude that local investigation of driving cycles is necessary for finding degradation limits and careful designation of parts replacement plans can help to massively increase air quality in large cities.

The aim of this study is to evaluate a heavy duty diesel engine operation under reactivity controlled compression ignition combustion fueled with diesel oil and natural gas enriched with hydrogen and nitrogen addition. In this study, a single cylinder heavy– duty diesel engine is set to operate at 9.4bar gross IMEP (Mid- Load). The amount of injected diesel oil per cycle into the engine combustion chamber assumes to be fixed and hydrogen and nitrogen (75:25 volumetric proportion of hydrogen: nitrogen) along with exhaust gas recirculation are gradually added to natural gas while the total fuel energy content is kept fixed. The results show that by adding hydrogen and nitrogen to natural gas, without the exposure to the excessive combustion noise, the hydrogen energy share can be enhanced up to 40.24% and the gross indicated efficiency more than 50% is achievable. Moreover, without significant engine power losses, the engine emission levels such as NOx, carbon monoxide, unburned hydrocarbon, and formaldehyde are reduced significantly.

Design of exhaust manifold is important due to its effects on performance of catalyst, thermal and thermo- mechanical loads. In this paper, first transient analysis of fluid was carried out with FLUENT software, then time-average temperature and heat transfer coefficient contour for three cycle were mapped on inner surface of exhaust manifold with MATLAB software for thermomechanical analysis. For validation of thermal analysis, experimental thermal data was used. In thermomechanical analysis, stress distribution in exhaust manifold due to thermal load, residual stress in exhaust manifold after cooling, vertical displacement of flange due to thermal load, flange torsion in vertical direction due to plastic strain has been validated. Finally, necessary geometrical corrections for optimal design structural resistance and strength of it has been delivered.